Best option for electric self starting glider

[Magnus]

Hi experienced glider pilots,

I am a newly retired ex glider pilot that is updating my license and want to do some serious soaring and distance flights in Europe now that I have plenty of time. I live in Lausanne (member of Montricher gliding club) and as well member in Landskrona gliding club in Sweden as well where I spend most of my summers.
I have come down to the following alternatives for a private purchase:

- LAK 17C Front Electric Self starter, 18m, 22kW, 10.32 m2 wing surface, MTOW 600kg and CS-22 certification

- GP-15 Jetta, retractable motor, 15m, 25kW, 7.78 m2 wing surface, MTOW 470kg, UL/EcoLight certification

Both ships are flapped, take water ballast, Vne= 275km/h, wing loading between 37 - 57kg/m2, L/D around 50 and has a base price of apps. 100kEuro

GP15 seems to be a more modern glider with safety cockpit, ballistic rescue system and steerable tail wheel but LAK seems to be a more stable company with longer experience.

This is a nice problem to have but I would very much like your input as I have a one time opportunity to get my dream machine and I want to get it right.

/Magnus

[[email protected]]

Hello Magnus,

I can't respond to flight characteristics of the two self-launchers you mentioned (LAK-17C and GP-Gliders JETA). But, I can say that I sat in a JETA and also have JETA serial number 5 on order.

The JETA MTOG, per the provisional flight manual, is 525KG (1157 lbs). Below are the advertised self-launch numbers with the larger battery:

a) 5 x takeoff and climb to 800 m (2,600 feet) altitude, or
b) 1 x takeoff and climb to 800 m altitude + 150 km (80 nm) autonomy, or
c) 1 x takeoff and total climb to 4 500 m (14,700 feet)
d) my number: aero tow and 185 km (100nm) autonomy based on 20 nm/launch.

Climb rate: >3,7 m/s (728 fpm or 7.2 knots)

takeoff distance: 180 m (590 feet)

I visited the GP-Glider factory near Krosno, Poland (jokingly to make sure that they weren't operating out of a tent). I was happy that they were doing things correctly. A visit to the LAK factory would have given me a balanced experience, but I was not able to do that.

Raul Boerner
LS-6BWL

[Dave Walsh[_2_]]

I'd take any unproven factory "statistics" with a large grain of
salt. You have a well known Antares 20E pilot based at
Montricher, have you asked his opinion?
You remember that old saw: never buy the first of anything, it
applies equally to yachts and sailplanes.
Dave Walsh (20E owner).

[Dave Nadler]

On Wednesday, April 8, 2020 at 11:45:05 AM UTC-4, Dave Walsh wrote:
> Dave Walsh (20E owner).

I believe that should be "(Long-suffering Antares 20E owner)"?
Meanwhile, mine has failed yet again...

[[email protected]]

Did you consider a Diana 2-FES? Mine delivers this month.
I chose it because it's a proven performing 15m glider, and it has the proven electric FES system. I don't want to be a test pilot for a new system with bugs.

I didn't place my order until I confirmed the performance figures myself and flew it to evaluate the handling, I would not trust any predicted/calculated numbers.

[[email protected]]

On Wednesday, April 8, 2020 at 6:04:43 PM UTC+1, wrote:
> Did you consider a Diana 2-FES? Mine delivers this month.
> I chose it because it's a proven performing 15m glider, and it has the proven electric FES system. I don't want to be a test pilot for a new system with bugs.
>
> I didn't place my order until I confirmed the performance figures myself and flew it to evaluate the handling, I would not trust any predicted/calculated numbers.

Are the Diana 2 FES and Lak 17B FES officially "self starters" - i.e. self-launchers as are the GP 15 and the Mini-LAK? Please correct me if I am wrong but I wasn't aware that they are other than self-sustainers, although I believe self-launching is unofficially possible in the right wind/runway/weight conditions.

[Magnus]

On Wednesday, April 8, 2020 at 7:31:13 PM UTC+2, wrote:
> On Wednesday, April 8, 2020 at 6:04:43 PM UTC+1, wrote:
> > Did you consider a Diana 2-FES? Mine delivers this month.
> > I chose it because it's a proven performing 15m glider, and it has the proven electric FES system. I don't want to be a test pilot for a new system with bugs.
> >
> > I didn't place my order until I confirmed the performance figures myself and flew it to evaluate the handling, I would not trust any predicted/calculated numbers.
>
> Are the Diana 2 FES and Lak 17B FES officially "self starters" - i.e. self-launchers as are the GP 15 and the Mini-LAK? Please correct me if I am wrong but I wasn't aware that they are other than self-sustainers, although I believe self-launching is unofficially possible in the right wind/runway/weight conditions.

LAK 17B FES is a sustainer but the new 17C FES is claimed as a self-starter (as miniLAK) with higher landing gear for propeller clearance, stronger FES, different aerodynamicall configuration of wings and fuselage according to LAK. For the Diana 2 FES I don't know.

[[email protected]]

On Wednesday, April 8, 2020 at 6:41:36 PM UTC+1, Magnus wrote:
> On Wednesday, April 8, 2020 at 7:31:13 PM UTC+2, wrote:
> > On Wednesday, April 8, 2020 at 6:04:43 PM UTC+1, wrote:
> > > Did you consider a Diana 2-FES? Mine delivers this month.
> > > I chose it because it's a proven performing 15m glider, and it has the proven electric FES system. I don't want to be a test pilot for a new system with bugs.
> > >
> > > I didn't place my order until I confirmed the performance figures myself and flew it to evaluate the handling, I would not trust any predicted/calculated numbers.
> >
> > Are the Diana 2 FES and Lak 17B FES officially "self starters" - i.e. self-launchers as are the GP 15 and the Mini-LAK? Please correct me if I am wrong but I wasn't aware that they are other than self-sustainers, although I believe self-launching is unofficially possible in the right wind/runway/weight conditions.
>
> LAK 17B FES is a sustainer but the new 17C FES is claimed as a self-starter (as miniLAK) with higher landing gear for propeller clearance, stronger FES, different aerodynamicall configuration of wings and fuselage according to LAK. For the Diana 2 FES I don't know.

Thank you for enlightening me Magnus. I didn't see that one on the LAK website.

[[email protected]]

If you register the Diana 2 as an ultralight, you can self launch. There's Diana 2's delivered and flying in France in this configuration.
If you register it as EASA CS-22, you cannot (legally). I'm told it's easier for them to get the initial TC through as a sustainer.

For self-launch under CS-22 you need 23cm of propeller clearance with the main wheel fully deflated. I believe both the Mini-LAK and the Silent 2 operate outside of CS-22 as microlights or otherwise if you want to use them for self launching.

It sounds like LAK is trying to get the 17C through on CS-22 for self launch with a modified landing gear to get that required clearance. I hope they'll be successful and others will follow.

On Wednesday, April 8, 2020 at 6:41:36 PM UTC+1, Magnus wrote:
> On Wednesday, April 8, 2020 at 7:31:13 PM UTC+2, wrote:
> > On Wednesday, April 8, 2020 at 6:04:43 PM UTC+1, wrote:
> > > Did you consider a Diana 2-FES? Mine delivers this month.
> > > I chose it because it's a proven performing 15m glider, and it has the proven electric FES system. I don't want to be a test pilot for a new system with bugs.
> > >
> > > I didn't place my order until I confirmed the performance figures myself and flew it to evaluate the handling, I would not trust any predicted/calculated numbers.
> >
> > Are the Diana 2 FES and Lak 17B FES officially "self starters" - i.e. self-launchers as are the GP 15 and the Mini-LAK? Please correct me if I am wrong but I wasn't aware that they are other than self-sustainers, although I believe self-launching is unofficially possible in the right wind/runway/weight conditions.
>
> LAK 17B FES is a sustainer but the new 17C FES is claimed as a self-starter (as miniLAK) with higher landing gear for propeller clearance, stronger FES, different aerodynamicall configuration of wings and fuselage according to LAK. For the Diana 2 FES I don't know.

[krasw]

Minilak is cs22 glider, not ultralight.

[[email protected]]

On Wednesday, April 8, 2020 at 8:08:57 PM UTC+1, krasw wrote:
> Minilak is cs22 glider, not ultralight.

I think it's a stretch to say it *is* CS-22 when it is not yet certified as such. Or at least I couldn't find any type certificate in the EASA database.
All existing miniLAK's will be flying on something else (PtF/Experimental/Ultralight). I have no doubt it is certifiable as it seems strongly derived from the LAK-17, the question is whether LAK will be able to certify it for self-launch, something I am sure all FES owners are watching.

[kinsell]

On 4/8/20 10:00 AM, Dave Nadler wrote:
> On Wednesday, April 8, 2020 at 11:45:05 AM UTC-4, Dave Walsh wrote:
>> Dave Walsh (20E owner).
>
> I believe that should be "(Long-suffering Antares 20E owner)"?
> Meanwhile, mine has failed yet again...
>

I always get a good laugh when somebody tries to tell me how reliable
and maintenance-free electric gliders are. They must be confusing
"ought to be" with "actually are".

[[email protected]]

I'm hoping that someone creates an electric self-launch glider with complete propulsion redundancy: two 20kW motors, two propellors, two batterey packs, two speed controls. Any single failure would leave you with at least sustainer performance.

A traditional motorglider must be flown like an unpowered sailplane; you must keep safe landing options within glide. With sufficient redundancy, it would not be unreasonable to enjoy soaring in some entirely new and inhospitable places.

[[email protected]]

On Wednesday, April 8, 2020 at 5:41:58 PM UTC-6, wrote:
> I'm hoping that someone creates an electric self-launch glider with complete propulsion redundancy: two 20kW motors, two propellors, two batterey packs, two speed controls. Any single failure would leave you with at least sustainer performance.
>
> A traditional motorglider must be flown like an unpowered sailplane; you must keep safe landing options within glide. With sufficient redundancy, it would not be unreasonable to enjoy soaring in some entirely new and inhospitable places.

To quote Dave Nadler, "How hard could it be?"

[Emir Sherbi]

El miércoles, 8 de abril de 2020, 21:33:17 (UTC-3), escribió:
> On Wednesday, April 8, 2020 at 5:41:58 PM UTC-6, wrote:
> > I'm hoping that someone creates an electric self-launch glider with complete propulsion redundancy: two 20kW motors, two propellors, two batterey packs, two speed controls. Any single failure would leave you with at least sustainer performance.
> >
> > A traditional motorglider must be flown like an unpowered sailplane; you must keep safe landing options within glide. With sufficient redundancy, it would not be unreasonable to enjoy soaring in some entirely new and inhospitable places.
>
> To quote Dave Nadler, "How hard could it be?"


Easiness = Sqroot(Money^3 * time^2)/(distance to manufacturers)

[kinsell]

On 4/8/20 5:41 PM, wrote:
> I'm hoping that someone creates an electric self-launch glider with complete propulsion redundancy: two 20kW motors, two propellors, two batterey packs, two speed controls. Any single failure would leave you with at least sustainer performance.
>
> A traditional motorglider must be flown like an unpowered sailplane; you must keep safe landing options within glide. With sufficient redundancy, it would not be unreasonable to enjoy soaring in some entirely new and inhospitable places.
>
>


Just start with a King Air and drop in a couple electric motors. Makes
more sense than a lot of electric conversions I read about.

[Tango Whisky]

Magnus, with a LAK17C you won't be able to take off safely from Montricher, especially not to the northeast. I wouldn't go for less than 50 hp, and that leaves you with Ventus 2CM, DG800, Antares 20E or ASH26E with the Schleicher prop.

Bert
Ventus cM "TW"
working in Lausanne, flying in Bex

[krasw]

On Wednesday, 8 April 2020 23:02:09 UTC+3, wrote:
> On Wednesday, April 8, 2020 at 8:08:57 PM UTC+1, krasw wrote:
> > Minilak is cs22 glider, not ultralight.
>
> I think it's a stretch to say it *is* CS-22 when it is not yet certified as such. Or at least I couldn't find any type certificate in the EASA database.
> All existing miniLAK's will be flying on something else (PtF/Experimental/Ultralight). I have no doubt it is certifiable as it seems strongly derived from the LAK-17, the question is whether LAK will be able to certify it for self-launch, something I am sure all FES owners are watching.

Ok. I asked this exact question few years back at Lak factory and was answered that they will certify it as glider. Lak has good track record certifying gliders.

[[email protected]]

> To quote Dave Nadler, "How hard could it be?"

Love the quote. Actually, this would be right up my alley. I've developed a few aircraft from scratch and people pay me a lot of money to modify special mission airplanes. A multi-motor self-launcher would be pretty easy to do as a modification to an existing self-launcher; probably a 3 month project. Perhaps I'll get around to this eventually, but first I have some more pressing items on my wish list!

[[email protected]]

Out of curiousity, does anyone know how electric motorgliders handle prop strikes? I know that it can be very expensive to rebuild a conventional aircraft engine after a prop strike, but what are electric manufacturers recommending?

[[email protected]]

>
> To quote Dave Nadler, "How hard could it be?"

Love the quote. I'm thinking this might actually be pretty easy to do as a modification to an existing glider with a FES configuration. Most of them already have two batteries and it would be simple to add a second motor controller. The hard part would be mounting the second sustainer motor in a clean manner. I'd have to do some structural analysis, but it might be possible to add a motor to the vertical stabilizer. Alternatively, one could glass motor mounts onto the wings for a pair of 5kW motors.

[kinsell]

On 4/9/20 12:05 AM, wrote:
>
>> To quote Dave Nadler, "How hard could it be?"
>
> Love the quote. Actually, this would be right up my alley. I've developed a few aircraft from scratch and people pay me a lot of money to modify special mission airplanes. A multi-motor self-launcher would be pretty easy to do as a modification to an existing self-launcher; probably a 3 month project. Perhaps I'll get around to this eventually, but first I have some more pressing items on my wish list!
>

Wow. The GP folks are about four years late in delivering product and
you can do all this in three months!! Go for it!!!

Actually the Alice electric plane has much of the redundancy that you're
asking for. Three motors with dual inverters on each of them, a highly
segmented battery configuration that can be reconfigured almost
infinitely. At least on paper it has those things, they burned up their
prototype before getting to taxi tests.

[[email protected]]

On Thursday, April 9, 2020 at 7:57:10 AM UTC+1, kinsell wrote:
> On 4/9/20 12:05 AM, wrote:
> >
> >> To quote Dave Nadler, "How hard could it be?"
> >
> > Love the quote. Actually, this would be right up my alley. I've developed a few aircraft from scratch and people pay me a lot of money to modify special mission airplanes. A multi-motor self-launcher would be pretty easy to do as a modification to an existing self-launcher; probably a 3 month project. Perhaps I'll get around to this eventually, but first I have some more pressing items on my wish list!
> >
>
> Wow. The GP folks are about four years late in delivering product and
> you can do all this in three months!! Go for it!!!
>
> Actually the Alice electric plane has much of the redundancy that you're
> asking for. Three motors with dual inverters on each of them, a highly
> segmented battery configuration that can be reconfigured almost
> infinitely. At least on paper it has those things, they burned up their
> prototype before getting to taxi tests.

If we're diving into pipedreams seeking maximum redundancy, what if there's a shared software bug between the parallel systems, like the firmware bug triggered by date that affected many GPS's simultaneously.
It'd be safer to combine two completely different systems for maximum redundancy, like Igor's MiniLAK FES-Jet (https://imgur.com/a/Y6uK4fP)
Plus you get the benefit of both propeller for climb and jet for cruise.

[[email protected]]

On Thursday, April 9, 2020 at 2:57:10 AM UTC-4, kinsell wrote:
> On 4/9/20 12:05 AM, wrote:
> >
> >> To quote Dave Nadler, "How hard could it be?"
> >
> > Love the quote. Actually, this would be right up my alley. I've developed a few aircraft from scratch and people pay me a lot of money to modify special mission airplanes. A multi-motor self-launcher would be pretty easy to do as a modification to an existing self-launcher; probably a 3 month project. Perhaps I'll get around to this eventually, but first I have some more pressing items on my wish list!
> >
>
> Wow. The GP folks are about four years late in delivering product and
> you can do all this in three months!! Go for it!!!
>
> Actually the Alice electric plane has much of the redundancy that you're
> asking for. Three motors with dual inverters on each of them, a highly
> segmented battery configuration that can be reconfigured almost
> infinitely. At least on paper it has those things, they burned up their
> prototype before getting to taxi tests.

Clearly you are a brilliant developer.
I'll describe my experience with this task.
Start with existing self launch sailplane having a fuel to noise converter. ASW-24E
Procure a group of components from existing supplier that was/is being used by a developer of self launch sailplanes. 10 week delivery.
Engineer and implement modifications to incorporate "proven" components. 10 weeks part time.
Test
Component failure (drive).
Return for warranty repair 4 weeks.
Test
Component failure (drive).
Return for warranty repair 4 weeks.
Test
Component failure (drive).
Return for warranty repair. Manufacturer say they can't repair due to my modifications. There were none. 3 weeks.
Source alternative controller used in another proven glider. 3 weeks.
Integrate, develop control and instrumentation to replace items obsoleted by controller change and get running. 6 weeks.
Test fly. Multiple sessions.
Now flying but more work to do to get full power and functionality.
So far this has taken a bit over 2 years, admittedly not full time.
If there was am identified and proven set of compatible components it might be possible for a very skilled person or group to do fast track. Given that I have seen no such group, I seriously doubt the projection is even close to realistic.
Given time this will be made to work well, but it won't be fast, or cheap.
Been there- Doing that
UH

[Dave Walsh[_2_]]

Ha, ha; so nice to see so many optimists still exist in gliding.
The idea of a duplicate electric engine/battery system must
bring a smile to those existing realists who already own an
electric glider.
I suppose the thought that twin systems just doubles the
chance of failures has been noted? In the power world there
seems to be no obvious safety advantages in having two
engines. What do they say: "In a twin the remaining working
engine gate you safely to the accident site"....
Dave Walsh

[Dave Nadler]

On Thursday, April 9, 2020 at 10:04:25 AM UTC-4, wrote:
> Been there- Doing that
> UH

Aw Hank, don't be such a downer.
For your viewing pleasure:
https://www.facebook.com/eNewsAZ/videos/video-of-the-airport-fire-eviation-prototype-plane/722278014963205/
https://evtol.com/news/lilium-evtol-catches-fire/

[David Smith[_5_]]

Getting back to the original question, which to choose, it you are a
sport pilot rather than a competition pilot if you choose a 15 M
span you are going to be starting the motor sooner than a 17 or
18M. I would be choosing the one with the lower wing loading, you
can still fly 15M on a strong day

At 14:29 09 April 2020, Dave Nadler wrote:
>On Thursday, April 9, 2020 at 10:04:25 AM UTC-4,

>wrote:
>> Been there- Doing that
>> UH
>
>Aw Hank, don't be such a downer.
>For your viewing pleasure:
>https://www.facebook.com/eNewsAZ/videos/video-of-the-
airport-fire-eviation-prototype-plane/722278014963205/
>https://evtol.com/news/lilium-evtol-catches-fire/
>

[David Smith[_5_]]

Getting back to the original question, which to choose, it you are a
sport pilot rather than a competition pilot if you choose a 15 M
span you are going to be starting the motor sooner than a 17 or
18M. I would be choosing the one with the lower wing loading, you
can still fly 15M on a strong day

At 14:29 09 April 2020, Dave Nadler wrote:
>On Thursday, April 9, 2020 at 10:04:25 AM UTC-4,

>wrote:
>> Been there- Doing that
>> UH
>
>Aw Hank, don't be such a downer.
>For your viewing pleasure:
>https://www.facebook.com/eNewsAZ/videos/video-of-the-
airport-fire-eviation-prototype-plane/722278014963205/
>https://evtol.com/news/lilium-evtol-catches-fire/
>

[Soartech]

On Thursday, April 9, 2020 at 2:12:46 AM UTC-4, wrote:
> Out of curiousity, does anyone know how electric motorgliders handle prop strikes? I know that it can be very expensive to rebuild a conventional aircraft engine after a prop strike, but what are electric manufacturers recommending?

I am buying the Jeta because I have seen a Silent Electro prop strike on a grass field. The prop is just too close to the ground for reliable self-launching in an FES (my opinion). In the situation I saw the prop exploded but running the motor afterward showed no evidence of a bent shaft or other damage to the system. However they still recommend you send it back to the factory for inspection!

[[email protected]]

On Thursday, April 9, 2020 at 9:00:24 AM UTC-8, Soartech wrote:
> On Thursday, April 9, 2020 at 2:12:46 AM UTC-4, wrote:
> > Out of curiousity, does anyone know how electric motorgliders handle prop strikes? I know that it can be very expensive to rebuild a conventional aircraft engine after a prop strike, but what are electric manufacturers recommending?
>
> I am buying the Jeta because I have seen a Silent Electro prop strike on a grass field. The prop is just too close to the ground for reliable self-launching in an FES (my opinion). In the situation I saw the prop exploded but running the motor afterward showed no evidence of a bent shaft or other damage to the system. However they still recommend you send it back to the factory for inspection!

I have lifted the tail of a Silent 2 Electro three feet before the prop contacts a level surface. It has flaps and does a nice two point lift off. I think a mini Lax might be similar. The prop strike might of been to much foward stick.

[WB]

> https://evtol.com/news/lilium-evtol-catches-fire/

Paul Moller must be so proud! Founding Father of the whole VTOL scam industry. Moller is probably bummed that he didn't think of the electric angle. How many more of the gullible could he have scammed if he had glued a couple solar panels to the wings of his Skycar?

[Eric Greenwell[_4_]]

wrote on 4/8/2020 4:41 PM:
> I'm hoping that someone creates an electric self-launch glider with complete propulsion redundancy: two 20kW motors, two propellors, two batterey packs, two speed controls. Any single failure would leave you with at least sustainer performance.
>
> A traditional motorglider must be flown like an unpowered sailplane; you must keep safe landing options within glide. With sufficient redundancy, it would not be unreasonable to enjoy soaring in some entirely new and inhospitable places.

Here is the simplest system I have thought of: Start with an FES self-launcher,
then add a fixed mast with a similar motor and a pusher folding propeller. One
battery for each motor, giving you two independent systems. You still have the
same available climb or distance ability.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Eric Greenwell[_4_]]

Magnus wrote on 4/8/2020 7:11 AM:
> Hi experienced glider pilots,
>
> I am a newly retired ex glider pilot that is updating my license and want to do some serious soaring and distance flights in Europe now that I have plenty of time. I live in Lausanne (member of Montricher gliding club) and as well member in Landskrona gliding club in Sweden as well where I spend most of my summers.
> I have come down to the following alternatives for a private purchase:
>
> - LAK 17C Front Electric Self starter, 18m, 22kW, 10.32 m2 wing surface, MTOW 600kg and CS-22 certification
>
> - GP-15 Jetta, retractable motor, 15m, 25kW, 7.78 m2 wing surface, MTOW 470kg, UL/EcoLight certification
>
> Both ships are flapped, take water ballast, Vne= 275km/h, wing loading between 37 - 57kg/m2, L/D around 50 and has a base price of apps. 100kEuro
>
> GP15 seems to be a more modern glider with safety cockpit, ballistic rescue system and steerable tail wheel but LAK seems to be a more stable company with longer experience.
>
> This is a nice problem to have but I would very much like your input as I have a one time opportunity to get my dream machine and I want to get it right.

Where do you find the information about the LAK 17C? I can not find any, not even
on the LAK site.

My dream is for a smaller, lighter, simpler self-launcher, but with the same
performance as my ASH26E. I considered the miniLak, AS34, and the GP15. The
miniLak did not have enough wing loading, L/D, and powered range for the
Nevada/Utah area I often fly in, and the AS34 was just as big and heavy as the
ASH26E. So, I have ordered a GP15 for delivery next year, as it promises the best
compromise. It will be a few months, maybe longer, before we know if it begins to
fulfill it's promise.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[[email protected]]

On Thursday, April 9, 2020 at 7:30:05 AM UTC-7, Dave Walsh wrote:
> Ha, ha; so nice to see so many optimists still exist in gliding.
> The idea of a duplicate electric engine/battery system must
> bring a smile to those existing realists who already own an
> electric glider.
> I suppose the thought that twin systems just doubles the
> chance of failures has been noted? In the power world there
> seems to be no obvious safety advantages in having two
> engines. What do they say: "In a twin the remaining working
> engine gate you safely to the accident site"....
> Dave Walsh

Much of the problem with multi-engine safety is due to minimum control airspeed with one engine. This is less of an issue with in-line configurations, such as the Cessna Skymaster. One benefit of electric propulsion is that it's very compact and provides more mounting options. You'd never squeeze two rotax engines into an in-line configuration, but this would be very easy to do with electric.

[[email protected]]

On Thursday, April 9, 2020 at 7:04:25 AM UTC-7, wrote:
> On Thursday, April 9, 2020 at 2:57:10 AM UTC-4, kinsell wrote:
> > On 4/9/20 12:05 AM, wrote:
> > >
> > >> To quote Dave Nadler, "How hard could it be?"
> > >
> > > Love the quote. Actually, this would be right up my alley. I've developed a few aircraft from scratch and people pay me a lot of money to modify special mission airplanes. A multi-motor self-launcher would be pretty easy to do as a modification to an existing self-launcher; probably a 3 month project. Perhaps I'll get around to this eventually, but first I have some more pressing items on my wish list!
> > >
> >
> > Wow. The GP folks are about four years late in delivering product and
> > you can do all this in three months!! Go for it!!!
> >
> > Actually the Alice electric plane has much of the redundancy that you're
> > asking for. Three motors with dual inverters on each of them, a highly
> > segmented battery configuration that can be reconfigured almost
> > infinitely. At least on paper it has those things, they burned up their
> > prototype before getting to taxi tests.
>
> Clearly you are a brilliant developer.
> I'll describe my experience with this task.
> Start with existing self launch sailplane having a fuel to noise converter. ASW-24E
> Procure a group of components from existing supplier that was/is being used by a developer of self launch sailplanes. 10 week delivery.
> Engineer and implement modifications to incorporate "proven" components. 10 weeks part time.
> Test
> Component failure (drive).
> Return for warranty repair 4 weeks.
> Test
> Component failure (drive).
> Return for warranty repair 4 weeks.
> Test
> Component failure (drive).
> Return for warranty repair. Manufacturer say they can't repair due to my modifications. There were none. 3 weeks.
> Source alternative controller used in another proven glider. 3 weeks.
> Integrate, develop control and instrumentation to replace items obsoleted by controller change and get running. 6 weeks.
> Test fly. Multiple sessions.
> Now flying but more work to do to get full power and functionality.
> So far this has taken a bit over 2 years, admittedly not full time.
> If there was am identified and proven set of compatible components it might be possible for a very skilled person or group to do fast track. Given that I have seen no such group, I seriously doubt the projection is even close to realistic.
> Given time this will be made to work well, but it won't be fast, or cheap..
> Been there- Doing that
> UH

Great job. I'd be interested to hear which components you ended up using. I've had my eye on some of the Pipistrel stuff, but I haven't had a chance to play with them yet. What kind of performance are you getting out of your ASW-24E conversion?

I actually make a living doing these types of projects FAST. I'm fortunate to live above a 4,000ft^2 workshop with in-house machining, CNC routing, CAD, vacuum forming, welding, autoclave, paint booth etc. I reckon it would take me about 3 months of full time work (Note: I tend to spend at least 80 hours per week on such projects), but I completely understand that 1-3 years is probably more reasonable for a typical homebuilt project.

[[email protected]]

On Thursday, April 9, 2020 at 12:31:56 AM UTC-7, wrote:
> On Thursday, April 9, 2020 at 7:57:10 AM UTC+1, kinsell wrote:
> > On 4/9/20 12:05 AM, wrote:
> > >
> > >> To quote Dave Nadler, "How hard could it be?"
> > >
> > > Love the quote. Actually, this would be right up my alley. I've developed a few aircraft from scratch and people pay me a lot of money to modify special mission airplanes. A multi-motor self-launcher would be pretty easy to do as a modification to an existing self-launcher; probably a 3 month project. Perhaps I'll get around to this eventually, but first I have some more pressing items on my wish list!
> > >
> >
> > Wow. The GP folks are about four years late in delivering product and
> > you can do all this in three months!! Go for it!!!
> >
> > Actually the Alice electric plane has much of the redundancy that you're
> > asking for. Three motors with dual inverters on each of them, a highly
> > segmented battery configuration that can be reconfigured almost
> > infinitely. At least on paper it has those things, they burned up their
> > prototype before getting to taxi tests.
>
> If we're diving into pipedreams seeking maximum redundancy, what if there's a shared software bug between the parallel systems, like the firmware bug triggered by date that affected many GPS's simultaneously.
> It'd be safer to combine two completely different systems for maximum redundancy, like Igor's MiniLAK FES-Jet (https://imgur.com/a/Y6uK4fP)
> Plus you get the benefit of both propeller for climb and jet for cruise.

Wow, that's a very cool concept. I wonder about the reliability and starting time of the jet.

[Dave Nadler]

On Thursday, April 9, 2020 at 3:31:56 AM UTC-4, wrote:
> ...what if there's a shared software bug between the parallel systems,
> like the firmware bug triggered by date that affected many GPS's simultaneously.

That wasn't a bug, epoch wrap was well understood and not implemented
by everyone. Especially in consumer stuff expected not to last >1 epoch.

> It'd be safer to combine two completely different systems for maximum
> redundancy, like Igor's MiniLAK FES-Jet (https://imgur.com/a/Y6uK4fP)

Pretty much guaranteeing something will always be broken,
and doubling the expertise required to diagnose and fix...

[Dan Marotta]

I'm not familiar with that airport, but my Stemme has 115 turbocharged
horsepower and a reliable Rotax 4-stroke engine.Â* It climbs at 800 fpm
at high density altitudes and, with a full gas tank of 30 US gallons,
can cruise for 8 hours at over 100 kts at 18,000' (more if you want to
be cold).

Or are we just talking about single seaters with delightfully light
controls? :-D

On 4/8/2020 10:23 PM, Tango Whisky wrote:
> Magnus, with a LAK17C you won't be able to take off safely from Montricher, especially not to the northeast. I wouldn't go for less than 50 hp, and that leaves you with Ventus 2CM, DG800, Antares 20E or ASH26E with the Schleicher prop.
>
> Bert
> Ventus cM "TW"
> working in Lausanne, flying in Bex

--
Dan, 5J

[kinsell]

On 4/9/20 12:20 PM, Eric Greenwell wrote:
> Magnus wrote on 4/8/2020 7:11 AM:
>> Hi experienced glider pilots,
>>
>> I am a newly retired ex glider pilot that is updating my license and
>> want to do some serious soaring and distance flights in Europe now
>> that I have plenty of time. I live in Lausanne (member of Montricher
>> gliding club) and as well member in Landskrona gliding club in Sweden
>> as well where I spend most of my summers.
>> I have come down to the following alternatives for a private purchase:
>>
>> - LAK 17C Front Electric Self starter, 18m, 22kW, 10.32 m2 wing
>> surface, MTOW 600kg and CS-22 certification
>>
>> - GP-15 Jetta, retractable motor, 15m, 25kW, 7.78 m2 wing surface,
>> MTOW 470kg, UL/EcoLight certification
>>
>> Both ships are flapped, take water ballast, Vne= 275km/h, wing loading
>> between 37 - 57kg/m2, L/D around 50 and has a base price of apps.
>> 100kEuro
>>
>> GP15 seems to be a more modern glider with safety cockpit, ballistic
>> rescue system and steerable tail wheel but LAK seems to be a more
>> stable company with longer experience.
>>
>> This is a nice problem to have but I would very much like your input
>> as I have a one time opportunity to get my dream machine and I want to
>> get it right.
>
> Where do you find the information about the LAK 17C? I can not find any,
> not even on the LAK site.
>
> My dream is for a smaller, lighter, simpler self-launcher, but with the
> same performance as my ASH26E. I considered the miniLak, AS34, and the
> GP15. The miniLak did not have enough wing loading, L/D, and powered
> range for the Nevada/Utah area I often fly in, and the AS34 was just as
> big and heavy as the ASH26E. So, I have ordered a GP15 for delivery next
> year, as it promises the best compromise. It will be a few months, maybe
> longer, before we know if it begins to fulfill it's promise.
>

Typing "lak 17c" into Google brings up multiple results, including an
Oct 2018 test flight in FB. Also been discussed on R.A.S.

[son_of_flubber]

On Thursday, April 9, 2020 at 3:16:58 PM UTC-4, wrote:

> Much of the problem with multi-engine safety is due to minimum control airspeed with one engine. This is less of an issue with in-line configurations, such as the Cessna Skymaster. One benefit of electric propulsion is that it's very compact and provides more mounting options. You'd never squeeze two rotax engines into an in-line configuration, but this would be very easy to do with electric.

I'd not much worry about the FES electric motor or prop failing. I might get a big reliability boost from redundant controllers. A small secondary battery pack with ~10 minutes of sustainer function would reduce my chances of landing in someone's attic. A more reliable 'metering fuel gauge' would solve the same problem with fewer parts.

If the system fails, the best Plan B for me is to land out. As a recreational pilot I choose where to fly, so flying out of reach of a landable field would be simple hubris.

Owning a tow-capable LSA AND a pure sailplane seems the most cost-effective solution to a shortage of aerotow providers. Finding a time-building young tow pilot should not be too hard, especially if I let them use the plane for few hours gratis and they might even crew if I occasionally land out. And I could fly the LSA on poor soaring days.

My interdependence with a group of people is one of the most rewarding aspects of soaring. If I wanted to be entirely self-reliant, I would buy a power plane, and pay hourly for professional assistance as needed.

[MNLou]

And nobody has mentioned the Diana 3.

Lou

[[email protected]]

On Thursday, April 9, 2020 at 3:42:55 PM UTC-4, wrote:
> On Thursday, April 9, 2020 at 7:04:25 AM UTC-7, wrote:
> > On Thursday, April 9, 2020 at 2:57:10 AM UTC-4, kinsell wrote:
> > > On 4/9/20 12:05 AM, wrote:
> > > >
> > > >> To quote Dave Nadler, "How hard could it be?"
> > > >
> > > > Love the quote. Actually, this would be right up my alley. I've developed a few aircraft from scratch and people pay me a lot of money to modify special mission airplanes. A multi-motor self-launcher would be pretty easy to do as a modification to an existing self-launcher; probably a 3 month project. Perhaps I'll get around to this eventually, but first I have some more pressing items on my wish list!
> > > >
> > >
> > > Wow. The GP folks are about four years late in delivering product and
> > > you can do all this in three months!! Go for it!!!
> > >
> > > Actually the Alice electric plane has much of the redundancy that you're
> > > asking for. Three motors with dual inverters on each of them, a highly
> > > segmented battery configuration that can be reconfigured almost
> > > infinitely. At least on paper it has those things, they burned up their
> > > prototype before getting to taxi tests.
> >
> > Clearly you are a brilliant developer.
> > I'll describe my experience with this task.
> > Start with existing self launch sailplane having a fuel to noise converter. ASW-24E
> > Procure a group of components from existing supplier that was/is being used by a developer of self launch sailplanes. 10 week delivery.
> > Engineer and implement modifications to incorporate "proven" components.. 10 weeks part time.
> > Test
> > Component failure (drive).
> > Return for warranty repair 4 weeks.
> > Test
> > Component failure (drive).
> > Return for warranty repair 4 weeks.
> > Test
> > Component failure (drive).
> > Return for warranty repair. Manufacturer say they can't repair due to my modifications. There were none. 3 weeks.
> > Source alternative controller used in another proven glider. 3 weeks.
> > Integrate, develop control and instrumentation to replace items obsoleted by controller change and get running. 6 weeks.
> > Test fly. Multiple sessions.
> > Now flying but more work to do to get full power and functionality.
> > So far this has taken a bit over 2 years, admittedly not full time.
> > If there was am identified and proven set of compatible components it might be possible for a very skilled person or group to do fast track. Given that I have seen no such group, I seriously doubt the projection is even close to realistic.
> > Given time this will be made to work well, but it won't be fast, or cheap.
> > Been there- Doing that
> > UH
>
> Great job. I'd be interested to hear which components you ended up using. I've had my eye on some of the Pipistrel stuff, but I haven't had a chance to play with them yet. What kind of performance are you getting out of your ASW-24E conversion?
>
> I actually make a living doing these types of projects FAST. I'm fortunate to live above a 4,000ft^2 workshop with in-house machining, CNC routing, CAD, vacuum forming, welding, autoclave, paint booth etc. I reckon it would take me about 3 months of full time work (Note: I tend to spend at least 80 hours per week on such projects), but I completely understand that 1-3 years is probably more reasonable for a typical homebuilt project.

Contact me privately for more conversation.
UH

[[email protected]]

but this would be very easy to do with electric.

I love it when armchair aircraft designers tell us something is "very easy."

[[email protected]]

On Thursday, April 9, 2020 at 4:46:57 PM UTC-7, wrote:
> but this would be very easy to do with electric.
>
> I love it when armchair aircraft designers tell us something is "very easy."

"armchair aircraft designers"... lol. I'll have to show you some of my more challenging, and very much finished, aerospace projects someday :)

I'm currently installing a Rotax on my ship. Electric is interesting, and I can certainly understand why it appeals to many. I personally favor the increased range of gasoline over the cleanliness and convenience of electric. Others will have different preferences. Either option can eliminate tows and retrieves, which is all well and good. However, a motor glider that "will start" can do a lot of things that a motor glider that "will probably start" cannot.

It would be a game changer if I could "safely" fly deep into unlandable terrain, or ridge soar the lip of the grand canyon. I'd love to plan some epic soaring safaris to rugged areas of Alaska, or make first flights in magnificent places. It would also be a whole new ballgame if I could reduce my restart altitude to something like 200ft. That sounds crazy until you figure out that's about 90 seconds at typical sink rates. If it takes only 10 seconds to transition to a powered climb, then 90 seconds provides plenty of margin.

The first electric motor gliders borrowed the retractable mast from their gasoline counterparts. Later, folks figured out that the smaller electric motor could fit in the nose. I think it's only a matter of time before people discover that we can use more than one motor, as is the trend for VTOL. Perhaps I'll get around to this at some point but I currently have a couple of more pressing crazy projects on my plate.

[[email protected]]

No disrespect intended, but RAS seems to have a large number of unicorn herders who are somewhat unclear on the laws of physics and engineering.

[Dave Nadler]

On Thursday, April 9, 2020 at 10:32:35 PM UTC-4, wrote:
> The first electric motor gliders borrowed the retractable mast
> from their gasoline counterparts.

No, real-world designers understood that a pylon system:
- makes possible much larger hence more efficient prop,
and efficiency is critical given battery low energy
- avoids prop strikes
- doesn't reduce performance
- makes cooling easier
Real-world examples include:
- original electric Silent circa 1997
- Antares (2m prop)
- AS-34 (and AS-32E sustainer)
- GP series (Real Soon Now)
- Hank's ASW-24E ;-)
etc.

[Magnus]

On Thursday, April 9, 2020 at 8:21:00 PM UTC+2, Eric Greenwell wrote:
> Magnus wrote on 4/8/2020 7:11 AM:
> > Hi experienced glider pilots,
> >
> > I am a newly retired ex glider pilot that is updating my license and want to do some serious soaring and distance flights in Europe now that I have plenty of time. I live in Lausanne (member of Montricher gliding club) and as well member in Landskrona gliding club in Sweden as well where I spend most of my summers.
> > I have come down to the following alternatives for a private purchase:
> >
> > - LAK 17C Front Electric Self starter, 18m, 22kW, 10.32 m2 wing surface, MTOW 600kg and CS-22 certification
> >
> > - GP-15 Jetta, retractable motor, 15m, 25kW, 7.78 m2 wing surface, MTOW 470kg, UL/EcoLight certification
> >
> > Both ships are flapped, take water ballast, Vne= 275km/h, wing loading between 37 - 57kg/m2, L/D around 50 and has a base price of apps. 100kEuro
> >
> > GP15 seems to be a more modern glider with safety cockpit, ballistic rescue system and steerable tail wheel but LAK seems to be a more stable company with longer experience.
> >
> > This is a nice problem to have but I would very much like your input as I have a one time opportunity to get my dream machine and I want to get it right.
>
> Where do you find the information about the LAK 17C? I can not find any, not even
> on the LAK site.
>
> My dream is for a smaller, lighter, simpler self-launcher, but with the same
> performance as my ASH26E. I considered the miniLak, AS34, and the GP15. The
> miniLak did not have enough wing loading, L/D, and powered range for the
> Nevada/Utah area I often fly in, and the AS34 was just as big and heavy as the
> ASH26E. So, I have ordered a GP15 for delivery next year, as it promises the best
> compromise. It will be a few months, maybe longer, before we know if it begins to
> fulfill it's promise.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

Hi Eric,
Thanks very much for your Guide to Self-Launching...
Your dream is the same as mine and I am curious how you came to the decision with all your experience behind you. Have you tested it? GP15 looks really good on paper but is unproven so far. I also met Sebastian Kawa last year after his almost crash landing with his GP14 when the electrical motor did not start. He has written an article about it in Soaring International December issue. I would really need some pilot feedback from testing it before I would dare to order one.
The LAK17FES was first officially shown at the Aero Show last year but the information is limited as LAK is waiting for the CS-22 certification. I will send you a data sheet separately by mail. It is heavier (but also 18m) and the motor is not as strong as for GP15 so it needs 350m on asphalt and 400-500m on grass to get airborne (without water ballast), which is a handicap. he battery is also smaller compared to GP15 if you choose the Jettas 8.1 kW alternative. The front vs the pylon mounted propeller can be discussed but the front mounted seems simpler with less risk for failure (less moving parts).
I really wish you all the best with the GP15 choice and look forward to your experiences.

[Magnus]

On Wednesday, April 8, 2020 at 5:14:54 PM UTC+2, wrote:
> Hello Magnus,
>
> I can't respond to flight characteristics of the two self-launchers you mentioned (LAK-17C and GP-Gliders JETA). But, I can say that I sat in a JETA and also have JETA serial number 5 on order.
>
> The JETA MTOG, per the provisional flight manual, is 525KG (1157 lbs). Below are the advertised self-launch numbers with the larger battery:
>
> a) 5 x takeoff and climb to 800 m (2,600 feet) altitude, or
> b) 1 x takeoff and climb to 800 m altitude + 150 km (80 nm) autonomy, or
> c) 1 x takeoff and total climb to 4 500 m (14,700 feet)
> d) my number: aero tow and 185 km (100nm) autonomy based on 20 nm/launch.
>
> Climb rate: >3,7 m/s (728 fpm or 7.2 knots)
>
> takeoff distance: 180 m (590 feet)
>
> I visited the GP-Glider factory near Krosno, Poland (jokingly to make sure that they weren't operating out of a tent). I was happy that they were doing things correctly. A visit to the LAK factory would have given me a balanced experience, but I was not able to do that.
>
> Raul Boerner
> LS-6BWL

Hi Raul,
When is your delivery of the Jeta? I am really interested in your experiences. Where are you flying?
According to the max wing loading of 60/37 kg/m2 the MTOM is below 475/285kg UL with a wing area of 7.77m2 - this also is indicated on the website. I suppose the take-off distance is without ballast but it is still good. How/where do you register it as UL?

[Magnus]

On Thursday, April 9, 2020 at 1:41:58 AM UTC+2, wrote:
> I'm hoping that someone creates an electric self-launch glider with complete propulsion redundancy: two 20kW motors, two propellors, two batterey packs, two speed controls. Any single failure would leave you with at least sustainer performance.
>
> A traditional motorglider must be flown like an unpowered sailplane; you must keep safe landing options within glide. With sufficient redundancy, it would not be unreasonable to enjoy soaring in some entirely new and inhospitable places.


There is a the Euroglider under design and testing in France with 2 electric motors with folding propellers on the wings - see Soaring International February 2020 issue.

[[email protected]]

On Friday, April 10, 2020 at 4:46:52 PM UTC+1, Magnus wrote:
> On Wednesday, April 8, 2020 at 5:14:54 PM UTC+2, wrote:
> > Hello Magnus,
> >
> > I can't respond to flight characteristics of the two self-launchers you mentioned (LAK-17C and GP-Gliders JETA). But, I can say that I sat in a JETA and also have JETA serial number 5 on order.
> >
> > The JETA MTOG, per the provisional flight manual, is 525KG (1157 lbs). Below are the advertised self-launch numbers with the larger battery:
> >
> > a) 5 x takeoff and climb to 800 m (2,600 feet) altitude, or
> > b) 1 x takeoff and climb to 800 m altitude + 150 km (80 nm) autonomy, or
> > c) 1 x takeoff and total climb to 4 500 m (14,700 feet)
> > d) my number: aero tow and 185 km (100nm) autonomy based on 20 nm/launch.
> >
> > Climb rate: >3,7 m/s (728 fpm or 7.2 knots)
> >
> > takeoff distance: 180 m (590 feet)
> >
> > I visited the GP-Glider factory near Krosno, Poland (jokingly to make sure that they weren't operating out of a tent). I was happy that they were doing things correctly. A visit to the LAK factory would have given me a balanced experience, but I was not able to do that.
> >
> > Raul Boerner
> > LS-6BWL
>
> Hi Raul,
> When is your delivery of the Jeta? I am really interested in your experiences. Where are you flying?
> According to the max wing loading of 60/37 kg/m2 the MTOM is below 475/285kg UL with a wing area of 7.77m2 - this also is indicated on the website. I suppose the take-off distance is without ballast but it is still good. How/where do you register it as UL?

Absent from those endurance/climb figures is the weight at which these are achieved, which is going to have a huge impact on the figures. Does anyone know the weight?
And are they are calculated or experimentally tested?

[Eric Greenwell[_4_]]

wrote on 4/10/2020 9:01 AM:
> On Friday, April 10, 2020 at 4:46:52 PM UTC+1, Magnus wrote:
>> On Wednesday, April 8, 2020 at 5:14:54 PM UTC+2, wrote:
>>> Hello Magnus,
>>>
>>> I can't respond to flight characteristics of the two self-launchers you mentioned (LAK-17C and GP-Gliders JETA). But, I can say that I sat in a JETA and also have JETA serial number 5 on order.
>>>
>>> The JETA MTOG, per the provisional flight manual, is 525KG (1157 lbs). Below are the advertised self-launch numbers with the larger battery:
>>>
>>> a) 5 x takeoff and climb to 800 m (2,600 feet) altitude, or
>>> b) 1 x takeoff and climb to 800 m altitude + 150 km (80 nm) autonomy, or
>>> c) 1 x takeoff and total climb to 4 500 m (14,700 feet)
>>> d) my number: aero tow and 185 km (100nm) autonomy based on 20 nm/launch.
>>>
>>> Climb rate: >3,7 m/s (728 fpm or 7.2 knots)
>>>
>>> takeoff distance: 180 m (590 feet)
>>>
>>> I visited the GP-Glider factory near Krosno, Poland (jokingly to make sure that they weren't operating out of a tent). I was happy that they were doing things correctly. A visit to the LAK factory would have given me a balanced experience, but I was not able to do that.
>>>
>>> Raul Boerner
>>> LS-6BWL
>>
>> Hi Raul,
>> When is your delivery of the Jeta? I am really interested in your experiences. Where are you flying?
>> According to the max wing loading of 60/37 kg/m2 the MTOM is below 475/285kg UL with a wing area of 7.77m2 - this also is indicated on the website. I suppose the take-off distance is without ballast but it is still good. How/where do you register it as UL?
>
> Absent from those endurance/climb figures is the weight at which these are achieved, which is going to have a huge impact on the figures. Does anyone know the weight?
> And are they are calculated or experimentally tested?

The quoted numbers are likely based on..

220kg empty weight + 21kg for large battery + pilot (75 kg? no mention) = 316 kg

The weight affects the climb proportionately, but I think the reduction in range
is not as much; mainly, the battery charge is not quite as much after the climb to
800 m. Note: the Vne is 300 kph, not the 275 I saw mentioned elsewhere.

The specifications are on this page:

https://www.gpgliders.com/offer/gp-15-e-se-jeta

They are calculated, and also a bit out of date, as better batteries are now
supplied, and also some changes in the controller, and aerodynamic refinements.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Eric Greenwell[_4_]]

kinsell wrote on 4/9/2020 1:38 PM:
> On 4/9/20 12:20 PM, Eric Greenwell wrote:
>> Magnus wrote on 4/8/2020 7:11 AM:

>> Where do you find the information about the LAK 17C? I can not find any, not
>> even on the LAK site.
>>
>> My dream is for a smaller, lighter, simpler self-launcher, but with the same
>> performance as my ASH26E. I considered the miniLak, AS34, and the GP15. The
>> miniLak did not have enough wing loading, L/D, and powered range for the
>> Nevada/Utah area I often fly in, and the AS34 was just as big and heavy as the
>> ASH26E. So, I have ordered a GP15 for delivery next year, as it promises the
>> best compromise. It will be a few months, maybe longer, before we know if it
>> begins to fulfill it's promise.
>>
>
> Typing "lak 17c" into Google brings up multiple results, including an Oct 2018
> test flight in FB.* Also been discussed on R.A.S.

I did that, and didn't find very much information. If it's not on the factory
site, it does not seem like a good choice to consider by a pilot that wants a
glider for next year's season. But, given it's an 18 m glider, it is unlikely to
meet my "smaller, lighter, easier) criteria.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[kinsell]

On 4/10/20 11:55 AM, Eric Greenwell wrote:
> kinsell wrote on 4/9/2020 1:38 PM:
>> On 4/9/20 12:20 PM, Eric Greenwell wrote:
>>> Magnus wrote on 4/8/2020 7:11 AM:
>
>>> Where do you find the information about the LAK 17C? I can not find
>>> any, not even on the LAK site.
>>>
>>> My dream is for a smaller, lighter, simpler self-launcher, but with
>>> the same performance as my ASH26E. I considered the miniLak, AS34,
>>> and the GP15. The miniLak did not have enough wing loading, L/D, and
>>> powered range for the Nevada/Utah area I often fly in, and the AS34
>>> was just as big and heavy as the ASH26E. So, I have ordered a GP15
>>> for delivery next year, as it promises the best compromise. It will
>>> be a few months, maybe longer, before we know if it begins to fulfill
>>> it's promise.
>>>
>>
>> Typing "lak 17c" into Google brings up multiple results, including an
>> Oct 2018 test flight in FB.Â* Also been discussed on R.A.S.
>
> I did that, and didn't find very much information. If it's not on the
> factory site, it does not seem like a good choice to consider by a pilot
> that wants a glider for next year's season. But, given it's an 18 m
> glider, it is unlikely to meet my "smaller, lighter, easier) criteria.


It's on the Blanik America website with base price of 99.500 euros.
Nice list of accessories. I saw a claim it was just a 17B-FES with a
new wing profile, if that's true then you would have the weight info.

http://home.nwi.net/~blanikam/ba/lak_prices.htm

Given GP's record in delivering gliders, I would take their promised
delivery dates with a huge grain of salt.

-Dave

[jld]

GP are getting their act together and increasing their manufacturing footprint.
We should finally see GP's coming out of the factory door.

Even if there is a little bit more complexity with a pylon mounted motor, there are clear advantages over the FES solution.
- more powerful motor
- better cooling
- better prop efficiency
- no prop strike risk
Another advantage of GP with large batteries is that, beside the larger energy capacity, the cells are discharged at lower amps rating and therefore run cooler.

The climb performance seems to be in line with flight test results.
As discussed before the published climb perf are without WB. Therefore TOM 320-330 kg. Even when flying empty, the typical WL will be ~42 kg/m2 which is already nice.
GP has made some good choices:
- light weight to allow very good electric climb performance (climb rate and altitude gain)
- high aspect ratio/low wing surface to achieve high L/D and higher WL. Maybe Max L/D will be a little bit less than 18m like ASH26 or DG800, but the L/D above 150 km/h should be better.

BTW, you need to add fixed ballast to get to 525 kg MTOM.

Regards,
JL

[Dan Marotta]

I looked at your email address website (sculptressfashions.com) and
didn't see anything aircraft related.Â* Did I miss something?

Regarding starting your motor or engine at 200' agl dismisses the
possibility that it can start, let you pitch up, and then fail, possibly
catastrophically.Â* I like your dream of flying deep into tiger country,
but I've had a couple of engine failures (6 to be exact) and so I don't
trust any engine to prevent a land out.Â* If I'm over an airport, I'll
descend to 1,000' before starting the engine.Â* The further out I am, the
higher I will start.

On 4/9/2020 8:32 PM, wrote:
> On Thursday, April 9, 2020 at 4:46:57 PM UTC-7, wrote:
>> but this would be very easy to do with electric.
>>
>> I love it when armchair aircraft designers tell us something is "very easy."
> "armchair aircraft designers"... lol. I'll have to show you some of my more challenging, and very much finished, aerospace projects someday :)
>
> I'm currently installing a Rotax on my ship. Electric is interesting, and I can certainly understand why it appeals to many. I personally favor the increased range of gasoline over the cleanliness and convenience of electric. Others will have different preferences. Either option can eliminate tows and retrieves, which is all well and good. However, a motor glider that "will start" can do a lot of things that a motor glider that "will probably start" cannot.
>
> It would be a game changer if I could "safely" fly deep into unlandable terrain, or ridge soar the lip of the grand canyon. I'd love to plan some epic soaring safaris to rugged areas of Alaska, or make first flights in magnificent places. It would also be a whole new ballgame if I could reduce my restart altitude to something like 200ft. That sounds crazy until you figure out that's about 90 seconds at typical sink rates. If it takes only 10 seconds to transition to a powered climb, then 90 seconds provides plenty of margin.
>
> The first electric motor gliders borrowed the retractable mast from their gasoline counterparts. Later, folks figured out that the smaller electric motor could fit in the nose. I think it's only a matter of time before people discover that we can use more than one motor, as is the trend for VTOL. Perhaps I'll get around to this at some point but I currently have a couple of more pressing crazy projects on my plate.
>
>

--
Dan, 5J

[[email protected]]

On Friday, April 10, 2020 at 6:30:28 PM UTC-7, Dan Marotta wrote:
> I looked at your email address website (sculptressfashions.com) and
> didn't see anything aircraft related.Â* Did I miss something?
>
> Regarding starting your motor or engine at 200' agl dismisses the
> possibility that it can start, let you pitch up, and then fail, possibly
> catastrophically.Â*

Dan, I looked up your email address at earthlink.net and didn't see anything about aviation either :) Feel free to check out motorcyclepilot.com for some of my cooler aviation products. My company primarily mods special mission aircraft and I've also produced tooling for a number of consumer products, such as the shapewear you found. Lately, I've been working mostly with airplanes, motorcycles, and boobs. It's a fun job, but somebody has to do it!

Yes, I'm proposing that it is possible to dismiss off field landings. Don't forget that airlines safely fly 4 billion passengers each year over unlandable terrain and oceans. There are multi-engine airplanes, helicopters and ultralights... it's not science fiction to put a second sustainer on a motor glider. Besides, we don't need to match the reliability of an airliner; we only need to achieve a level of risk that's appropriate for the sport of cross-country soaring.

Let's assume that a modern FES system has a 1 in 200 chance of failure. I would expect pilots to encounter a failure every few years and it sounds like this has been your experience. Now, if you can install a second sustainer with the same reliability (1 failure in 200), then the chance of a double failure works out to 1 in 40,000. If the failure rate of each sustainer happens to be more like 1 in 400, then the chance of a double failure rate would be only 1 in 160,000!

To put this into perspective, the Soaring Safety Foundation estimates that soaring pilots have accidents every few thousand hours. Amatuer Built airplanes, such as the ones that I fly, have a fatality every 18,000 hours. I would personally feel very comfortable making occassional low saves and trusting a twin propulsion system with a failure rate of 1 in 160,000. Instead of worrying about a double motor failure, I'd be far more concerned about stall/spin while soaring at low altitude.

Also consider that off field landings are risky business. Preparing for off field landings is great, but avoiding them is all the better. If you could eliminate 99.75% of off-field landings via reliability, then I think you'd see an overall safety gain, even if some of saves happened at low altitude..
Indeed with increasing reliability, a threshold exists at which it would be safer to attempt a LOW save in an EXTREMELY realiable motor glider, than it is to attempt a 1,000ft save in a traditiol motor glider. I've done some preliminary spreadsheet models and I believe this objective is feasible for a a sailplane with two sustainer systems.

I'm interested in this concept for adventure soaring. However, there are also obvious competitive advantages with being able to stray far from landing fields, or safely restart from 200ft.

[[email protected]]

On Saturday, April 11, 2020 at 7:46:26 AM UTC+1, wrote:
> On Friday, April 10, 2020 at 6:30:28 PM UTC-7, Dan Marotta wrote:
> > I looked at your email address website (sculptressfashions.com) and
> > didn't see anything aircraft related.Â* Did I miss something?
> >
> > Regarding starting your motor or engine at 200' agl dismisses the
> > possibility that it can start, let you pitch up, and then fail, possibly
> > catastrophically.Â*
>
> Dan, I looked up your email address at earthlink.net and didn't see anything about aviation either :) Feel free to check out motorcyclepilot.com for some of my cooler aviation products. My company primarily mods special mission aircraft and I've also produced tooling for a number of consumer products, such as the shapewear you found. Lately, I've been working mostly with airplanes, motorcycles, and boobs. It's a fun job, but somebody has to do it!
>
> Yes, I'm proposing that it is possible to dismiss off field landings. Don't forget that airlines safely fly 4 billion passengers each year over unlandable terrain and oceans. There are multi-engine airplanes, helicopters and ultralights... it's not science fiction to put a second sustainer on a motor glider. Besides, we don't need to match the reliability of an airliner; we only need to achieve a level of risk that's appropriate for the sport of cross-country soaring.
>
> Let's assume that a modern FES system has a 1 in 200 chance of failure. I would expect pilots to encounter a failure every few years and it sounds like this has been your experience. Now, if you can install a second sustainer with the same reliability (1 failure in 200), then the chance of a double failure works out to 1 in 40,000. If the failure rate of each sustainer happens to be more like 1 in 400, then the chance of a double failure rate would be only 1 in 160,000!
>
> To put this into perspective, the Soaring Safety Foundation estimates that soaring pilots have accidents every few thousand hours. Amatuer Built airplanes, such as the ones that I fly, have a fatality every 18,000 hours. I would personally feel very comfortable making occassional low saves and trusting a twin propulsion system with a failure rate of 1 in 160,000. Instead of worrying about a double motor failure, I'd be far more concerned about stall/spin while soaring at low altitude.
>
> Also consider that off field landings are risky business. Preparing for off field landings is great, but avoiding them is all the better. If you could eliminate 99.75% of off-field landings via reliability, then I think you'd see an overall safety gain, even if some of saves happened at low altitude.
> Indeed with increasing reliability, a threshold exists at which it would be safer to attempt a LOW save in an EXTREMELY realiable motor glider, than it is to attempt a 1,000ft save in a traditiol motor glider. I've done some preliminary spreadsheet models and I believe this objective is feasible for a a sailplane with two sustainer systems.
>
> I'm interested in this concept for adventure soaring. However, there are also obvious competitive advantages with being able to stray far from landing fields, or safely restart from 200ft.

Cargo pods, handbags and ugg boots, that's an eclectic mix - I think that website has been hacked? See http://motorcyclepilot.com/contact.php (caution advised)

[Luka Žnidarši�[_2_]]

Note that at LAK17C max power is 30kW. With such power climb performance are very good as there is no pylon drag.

[jld]

The propulsion efficiency has much more direct effect than pylon drag.
In fact, for Takeoff and climb performance, the overall glider drag has secondary effect compared to aircraft weight and available thrust.
Without fuselage interference and opportunities for larger props, the pylon mounted motor provides a significant efficiency advantage. This has a direct effect on climb performance in terms of climb rate and altitude gain.
Running large battery packs, beside running cooler, also provides better energy efficiency and installing large batteries in the wing reduces overall structure weight and provides better flying handling characteristics due to CG.

FES is a nice solution, especially for retrofit of existing gliders.
For a brand new design, there are opportunities for better optimizations.
Is GP at the optimum, probably not (yet:-), but they have certainly made good design decisions for both teh glider and the propulsion.

[Dave Walsh[_2_]]

This thread gets better and better!

"obvious competitive advantages with being able to stray far
from landing fields, or safely restart from 200ft"

Not sure about a "competitive advantage" but you must be in
the running for a Darwin Award. Obviously Covid-19 holds no
fears for you.

[Dan Marotta]

On 4/11/2020 12:46 AM, wrote:
> airplanes, motorcycles, and boobs. It's a fun job, but somebody has to do it!
:-D

My fridge is open to you at Moriarty Municipal Airport, Dave!

Nice products and I liked your approach to adventure soaring.Â* We're
heading out on a different path, having an AirGyro AG-915
<http://www.airgyro.com/> kit on order.Â* We should have been assembling
it or even test flying it right now but this damned virus thing has
things slowed down.

This aircraft will complete our toy box, sitting between the Stemme and
the Cessna 180K.Â* I do the maintenance on my 2004 Dyna Wide Glide in the
hangar, too.
--
Dan, 5J

[Muttley]

There was a project in the UK for a UL Glider driven by a Motorised Main Wheel and a Jet. Website still up at http://www.proairsport.com/project-glow.php
However do no think it ever got of the Ground.

[Martin Gregorie[_6_]]

On Sat, 11 Apr 2020 08:10:55 -0700, Muttley wrote:

> There was a project in the UK for a UL Glider driven by a Motorised Main
> Wheel and a Jet. Website still up at
> http://www.proairsport.com/project-glow.php However do no think it ever
> got of the Ground.

I think it was taxiied and have a feeling that was without wings fitted.

But UL? Its empty weight, 180 kg, is the same as the Diana 2.

--
Martin | martin at
Gregorie | gregorie dot org

[[email protected]]

On Saturday, April 11, 2020 at 4:51:34 PM UTC+1, Martin Gregorie wrote:
> On Sat, 11 Apr 2020 08:10:55 -0700, Muttley wrote:
>
> > There was a project in the UK for a UL Glider driven by a Motorised Main
> > Wheel and a Jet. Website still up at
> > http://www.proairsport.com/project-glow.php However do no think it ever
> > got of the Ground.
>
> I think it was taxiied and have a feeling that was without wings fitted.
>
> But UL? Its empty weight, 180 kg, is the same as the Diana 2.
>
> --
> Martin | martin at
> Gregorie | gregorie dot org

I'd be interested to hear some reasons from the peanut armchair-aircraft-designer gallery as to why electric main wheels haven't "taken off" - seems like it would be a big win for both electric gliders in reduced launch energy, and solve the static thrust problem for jet self launchers?
The biggest problem I see is you'd need to have the main wheel a long way forwards, or a nose wheel to not pitch over on the belly?

[BG[_4_]]

On Saturday, April 11, 2020 at 9:04:39 AM UTC-7, wrote:
> On Saturday, April 11, 2020 at 4:51:34 PM UTC+1, Martin Gregorie wrote:
> > On Sat, 11 Apr 2020 08:10:55 -0700, Muttley wrote:
> >
> > > There was a project in the UK for a UL Glider driven by a Motorised Main
> > > Wheel and a Jet. Website still up at
> > > http://www.proairsport.com/project-glow.php However do no think it ever
> > > got of the Ground.
> >
> > I think it was taxiied and have a feeling that was without wings fitted..
> >
> > But UL? Its empty weight, 180 kg, is the same as the Diana 2.
> >
> > --
> > Martin | martin at
> > Gregorie | gregorie dot org
>
> I'd be interested to hear some reasons from the peanut armchair-aircraft-designer gallery as to why electric main wheels haven't "taken off" - seems like it would be a big win for both electric gliders in reduced launch energy, and solve the static thrust problem for jet self launchers?
> The biggest problem I see is you'd need to have the main wheel a long way forwards, or a nose wheel to not pitch over on the belly?


Like to confirm a real world experience I had some years back while visiting El Tiro. I was there with my DG 800b took real interest in an Antares 20e that was tied down. I beleive the advertised climb from sea level in still air is 9000 ft. Well, sitting next to the glider was a hefty Honda gas generator. I asked the owner some question about his experience so far. First thing he said was he was disappointed. They found once the ground temperatures were above 100F they need to keep it in the shade before launch. If they left it ouside the batteries would over heat at around 1000AGL. Guess it� was designed for cooler climates like in Germany. Next I asked him how long it took to recharge the batteries from the generator.. He basically said all night long and consumed 10 gallons of gas. I doubt there are airports that would allow you to tap into their grid. El Tiro was using solar panels. On sites like Truckee where you can camp on the airport, you would become very unpopular in a hurry have that much noise. I have never seen an Antares fly from there, getting back into Truckee requires a climb to over 12,000 feet to safely get back in. The surrounding routes back in might have you starting the engine at 5-6k. Very marginal or impossible if you used the engine for self launch at the beginning of the day. In contrast the DG 800 will climb to well over 14k, personally in the winter I took off from sea level and climbed to 16k and it was still gaining 100-200 FPM. Recharging the gas tank takes less than 5 minutes for 5 gallons of fuel. When the battery's reach a much higher level of capacity and are able to be recharged in a different way, the electric glider will come of age, and i have no doubt they will. The backing to behind this push is driven by electric cars. Asking any one who owns a pure electric car and hear their stories on range anxiety. ONLY Tesla usiong super chargers do you see a charge time to drive time much less than one. My Volt is horrible! From a 110vac socket pulling 8 amps, it takes over 12 hours to get 40 minutes of driving time at 60 mph.

[Eric Greenwell[_4_]]

kinsell wrote on 4/10/2020 1:18 PM:
> On 4/10/20 11:55 AM, Eric Greenwell wrote:
>> kinsell wrote on 4/9/2020 1:38 PM:
>>> On 4/9/20 12:20 PM, Eric Greenwell wrote:
>>>> Magnus wrote on 4/8/2020 7:11 AM:
>>
>>>> Where do you find the information about the LAK 17C? I can not find any, not
>>>> even on the LAK site.
>>>>
>>>> My dream is for a smaller, lighter, simpler self-launcher, but with the same
>>>> performance as my ASH26E. I considered the miniLak, AS34, and the GP15. The
>>>> miniLak did not have enough wing loading, L/D, and powered range for the
>>>> Nevada/Utah area I often fly in, and the AS34 was just as big and heavy as the
>>>> ASH26E. So, I have ordered a GP15 for delivery next year, as it promises the
>>>> best compromise. It will be a few months, maybe longer, before we know if it
>>>> begins to fulfill it's promise.
>>>>
>>>
>>> Typing "lak 17c" into Google brings up multiple results, including an Oct 2018
>>> test flight in FB.* Also been discussed on R.A.S.
>>
>> I did that, and didn't find very much information. If it's not on the factory
>> site, it does not seem like a good choice to consider by a pilot that wants a
>> glider for next year's season. But, given it's an 18 m glider, it is unlikely to
>> meet my "smaller, lighter, easier) criteria.
>
>
> It's on the Blanik America website with base price of 99.500 euros. Nice list of
> accessories.* I saw a claim it was just a 17B-FES with a new wing profile, if
> that's true then you would have the weight info.
>
> http://home.nwi.net/~blanikam/ba/lak_prices.htm
>
> Given GP's record in delivering gliders, I would take their promised delivery
> dates with a huge grain of salt.
>
It would take major changes beyond a new wing profile to transform the 17B FES
into a self-launcher; regardless, I contacted the dealer in Nov 2019 about
electric self-launchers. He offered only the miniLAK (it ended up being my second
choice, after the GP15), and did not mention the 17C. It is odd that the dealer
lists the prices for the 17C, but no technical information.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Eric Greenwell[_4_]]

Luka Žnidarši� wrote on 4/11/2020 1:14 AM:
> Note that at LAK17C max power is 30kW. With such power climb performance are very good as there is no pylon drag.
>
The pylon mount allows a much greater choice in propellers, allowing it to
significantly exceed an FES in efficiency. The GP15, for example, uses a three
blade propeller, and the blade shape is not constrained by the shape of the nose,
or the need for low drag when the motor is stopped. The pylon is a single,
streamlined strut that will produce almost insignificant drag at climb speeds,
even when accounting for the open doors. I base that claim on how well my ASH 26 E
thermals with the engine partially retracted for cooling, a much dirtier object
than the GP15 pylon.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Ron Gleason]

On Saturday, 11 April 2020 11:51:57 UTC-6, Eric Greenwell wrote:
> Luka Žnidarši� wrote on 4/11/2020 1:14 AM:
> > Note that at LAK17C max power is 30kW. With such power climb performance are very good as there is no pylon drag.
> >
> The pylon mount allows a much greater choice in propellers, allowing it to
> significantly exceed an FES in efficiency. The GP15, for example, uses a three
> blade propeller, and the blade shape is not constrained by the shape of the nose,
> or the need for low drag when the motor is stopped. The pylon is a single,
> streamlined strut that will produce almost insignificant drag at climb speeds,
> even when accounting for the open doors. I base that claim on how well my ASH 26 E
> thermals with the engine partially retracted for cooling, a much dirtier object
> than the GP15 pylon.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

While classified as a CLass 2 Hang Glider, this machine fits the objectives you defined https://www.youtube.com/watch?v=G3qfW3ydZuY&t=178s

Yes they are ridiculously expensive

[Dave Walsh[_2_]]

In the Antares I'd expect to get to ~2500 feet AGL if the
ground temperature was 37C (100F). This at Sisteron at 1770
feet; so not a lot different to El Tiro altitude, this assumes that
the batteries/electronics are cool at the start. On my A/C the
climb limit would be the engine temperature not the battery
temperature. After such a climb I'd expect 50-60% battery
charge remaining so you'd certainly get a healthy climb at the
end of the day.
A Honda generator is a very non ideal way to charge the
batteries, perhaps it wasn't powerful enough? Plugged into the
mains (a 230 volt 16A supply) it rarely takes 7 hours to fully
charge.
As I've said before you cannot fly it like a DG800 but not many
pilots go from Antares20E to DG800.
And before the DG owners pass comment I did own a DG808C
for several years.
Dave Walsh

[Eric Greenwell[_4_]]

jld wrote on 4/10/2020 4:48 PM:
> GP are getting their act together and increasing their manufacturing footprint.
> We should finally see GP's coming out of the factory door.
>
> Even if there is a little bit more complexity with a pylon mounted motor, there are clear advantages over the FES solution.
> - more powerful motor
> - better cooling
> - better prop efficiency
> - no prop strike risk
> Another advantage of GP with large batteries is that, beside the larger energy capacity, the cells are discharged at lower amps rating and therefore run cooler.
>
> The climb performance seems to be in line with flight test results.
> As discussed before the published climb perf are without WB. Therefore TOM 320-330 kg. Even when flying empty, the typical WL will be ~42 kg/m2 which is already nice.
> GP has made some good choices:
> - light weight to allow very good electric climb performance (climb rate and altitude gain)
> - high aspect ratio/low wing surface to achieve high L/D and higher WL. Maybe Max L/D will be a little bit less than 18m like ASH26 or DG800, but the L/D above 150 km/h should be better.
>
> BTW, you need to add fixed ballast to get to 525 kg MTOM.
>
> Regards,
> JL

It's not clear going to a 525kg/7.78m2 = 67 kg/m2 (13.75 lb/ft2) wing loading is a
good idea, even in very strong conditions! That aside, the wing loading without
fixed ballast depends on the battery size, because the batteries take up space in
the wing that could be used for water. You can put in 130 L if you get the small
battery; but only 85 L using the big battery. I estimate I can go to 12 lb/ft2
with my weight (165 lb), the large battery, and 85 L of water. That should be
adequate, even in Nevada.

The minimum wing loading you can achieve depends mostly on the battery size you
select, as the large battery is 21 kg heavier than the small battery. That's a
2.7kg/m2 difference (about 0.6 lb/ft2).

Note that pilot weight is just the pilot - no parachute - as the glider has it's
own parachute.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Luka Žnidarši�[_2_]]

Dne sobota, 11. april 2020 12.02.19 UTC+2 je oseba jld napisala:
> The propulsion efficiency has much more direct effect than pylon drag.
> In fact, for Takeoff and climb performance, the overall glider drag has secondary effect compared to aircraft weight and available thrust.
> Without fuselage interference and opportunities for larger props, the pylon mounted motor provides a significant efficiency advantage. This has a direct effect on climb performance in terms of climb rate and altitude gain.
> Running large battery packs, beside running cooler, also provides better energy efficiency and installing large batteries in the wing reduces overall structure weight and provides better flying handling characteristics due to CG.
>
> FES is a nice solution, especially for retrofit of existing gliders.
> For a brand new design, there are opportunities for better optimizations.
> Is GP at the optimum, probably not (yet:-), but they have certainly made good design decisions for both teh glider and the propulsion.

Actually efficiency of glider in powered mode is quite important:
1.Efficiency of FES powered glider in powered mode is the same as in glide mode.

FES powered glider, L/D 50 and 500kg T.O.W, minimum sink 0,5m/s:
-required thrust for level flight; 500kg/50=10kg which is 100N
-another 100N is required for climb rate 0,5m/s; 200N
-another 100N is required for climb rate 1,0m/s; 300N
-another 100N is required for climb rate 1,5m/s; 400N
-another 100N is required for climb rate 2,0m/s; 500N
-another 100N is required for climb rate 2,5m/s; 600N
-another 100N is required for climb rate 3,0m/s; 700N

2.Efficiency of most powered gliders with retractable systems is about half (or even worse) of the efficiency as glider. Note that pylon drag with its big pulley or motor on top is still there even if propeller is rotating :).. Like flying with half opened airbrakes.

Pylon powered glider, with pylon extended, L/D 25 and 500kg T.O.W, minimum sink 1,0m/s:
-required thrust for level flight; 500/25=20kg which is 200N
-another 200N for climb rate 1m/s; 400N
-another 200N for climb rate 2m/s; 600N
-another 200N for climb rate 3m/s; 800N

Efficiency of propeller not depends just on its diameter but also how much thrust such propeller should create. Even with smaller propeller diameter is possible to achieve good efficiency when required thrust is smaller, for instance during level flight or more shallow climb rates and this is typical use of FES. As you can see above, with FES required thrust for climb rate 1m/s is 300N, while with pylon for 1m/s is required 400N. This seems to be possible to offset with higher efficiency of bigger propeller, but bigger propeller requires higher torque. With direct drive electric motors higher torque can be achieved only with bigger motor diameter, but this means even more drag. With more drag it would be required also more thrust from propeller, which means higher power, higher energy consumption, bigger battery packs, more weight. Another possibility is to install motor in the fuselage and transfer power with belts to pylon, but there are quite high loses in efficiency, more that most engineers imagine and so not in equation. Diameter of upper pulley is usually bigger than lower pulley, due to reduction ratio, which is not helpful from drag viewpoint. And number of propeller blades do not affect much to its efficiency. It is only helpful if prop loading it very high but is also possible to increase chord of propeller blades to some extent.

So 700N for FES with 1m prop diameter or 800N with 1,4m (or bigger) retractable system to climb 3m/s, seems to be in advantage of pylon due to better prop efficiency. However, when you put all factors into equation, result is almost the same.
However, in the range of lower power settings FES is much more efficient (100N vs 200N).
In case of FES self-launch, I feel much safer on critical altitudes till 50m, as in case of motor failure there is still available pure glider efficiency to perform a turn back if required. With retractable systems you end up flying a brick, where you can hardly afford turning back without risk of spin entry.
Another big FES advantage is non problematic starting of engine above non landable terrain.
With retractable systems you should never try to start engine without landing field below, as in case that engine do not start and cannot be retracted for any reason, you end up flying a brick.
Clearly propeller clearance is advantage of pylon, but with pylon there are more problems related to take-off in side-wind conditions. With FES there is much better rudder efficiency.
It is hard to compare FES with retractable systems, as they are very different in also in flying style, and all pilots will prefer one over another.
I believe that in next months there will be more information about LAK17C FES.

[Eric Greenwell[_4_]]

BG wrote on 4/11/2020 10:17 AM:
> On Saturday, April 11, 2020 at 9:04:39 AM UTC-7, wrote:
>> On Saturday, April 11, 2020 at 4:51:34 PM UTC+1, Martin Gregorie wrote:
>>> On Sat, 11 Apr 2020 08:10:55 -0700, Muttley wrote:

>
> Like to confirm a real world experience I had some years back while visiting El Tiro. I was there with my DG 800b took real interest in an Antares 20e that was tied down. I beleive the advertised climb from sea level in still air is 9000 ft. Well, sitting next to the glider was a hefty Honda gas generator. I asked the owner some question about his experience so far. First thing he said was he was disappointed. They found once the ground temperatures were above 100F they need to keep it in the shade before launch. If they left it ouside the batteries would over heat at around 1000AGL. Guess it� was designed for cooler climates like in Germany. Next I asked him how long it took to recharge the batteries from the generator.. He basically said all night long and consumed 10 gallons of gas. I doubt there are airports that would allow you to tap into their grid. El Tiro was using solar panels. On sites like Truckee where you can camp on the airport, you would become very unpopular in a hurry have that much noise. I have never seen an Antares fly from there, getting back into Truckee requires a climb to over 12,000 feet to safely get back in. The surrounding routes back in might have you starting the engine at 5-6k. Very marginal or impossible if you used the engine for self launch at the beginning of the day. In contrast the DG 800 will climb to well over 14k, personally in the winter I took off from sea level and climbed to 16k and it was still gaining 100-200 FPM. Recharging the gas tank takes less than 5 minutes for 5 gallons of fuel. When the battery's reach a much higher level of capacity and are able to be recharged in a different way, the electric glider will come of age, and i have no doubt they will. The backing to behind this push is driven by electric cars. Asking any one who owns a pure electric car and hear their stories on range anxiety. ONLY Tesla usiong super chargers do you see a charge time to drive time much less than one. My Volt is horrible! From a 110vac socket pulling 8 amps, it takes over 12 hours to get 40 minutes of driving time at 60 mph.

It is strange to hear "When the battery's reach a much higher level of capacity
and are able to be recharged in a different way, the electric glider will come of
age", as the number in service and on order increase quickly, and the pilots are
smiling broadly. The current batteries a quite sufficient for a lot of pilots,
especially for FES pilots.

I've flown my ASH 26 E for 25 years, so I have plenty of experience with the range
I use and want. Based on that experience (over 4000 hours), I decided the GP15
with the large battery would easily handle all but a few of the self-retrieve
situations I've encountered. Those few situations can be avoided by turning around
in flight a bit sooner, or accepting a car or towplane retrieve every few years.

Recharging the batteries may be the more difficult problem, but at the places I
normally fly, all have at least one of these choices:

- plugging in to the FBO sockets, RV campground power pedestals, or friend's hangars
- charging with my RV's generator, or with a portable generator
- taking the batteries to the motel for charging

Your judgement is based on how you operate, but your criteria are not universal,
as I have indicated. If we went by your DG 800 comparison, no one would be flying
an FES, and a pure glider would never fly from Truckee!

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[David Shelton]

>
> Not sure about a "competitive advantage" but you must be in
> the running for a Darwin Award. Obviously Covid-19 holds no
> fears for you.

Dave, I've already run my engine at 200ft more times than I can remember! Damn near every self-launch seems to involve climbing through 200ft with the engine out ;)

To be clear, I haven't suggested doing anything dangerous. I'm exploring very reasonable operating limitations for a hypethetical motor glider that is orders of magnitude more reliable than a traditional one. Since a couple orders of magnitude is a VERY BIG difference, you really can't draw on experiences or practices from traditional motor gliders. It's a bit of a paradym shift so you really need to look at the math to get your mind around it.

My premise is this:

1) It is physically possible to install a redundant sustainer system on an existing FES motor glider.

2) The math suggests that there is room to improve reliability by several orders of magnitude.

3) With sufficient reliability, one could SAFELY operate over unlandable terrain, or lower decision heights. SAFELY means that the risk can be made very small relative to our other flight risks (stall/spin, mid-air, weather, etc.).

By the way, my cousin flies accross the ocean for work. My ex flies commercial heli tours over volcanos. My neighbor's airplane is certified to fly in known icing conditions. My aerial applicator buddies fly around at 5ft AGL with only ONE engine. I don't think it's very far-fetched to imagine an occasional trip down to 200ft AGL in a motor glider with redundant propulsion.. Unfortunately, existing motor gliders are just soooooo ****ty that we can't imagine starting the engine unless our fingers are crossed and we're at least 1,000ft above a landing field. Many accept this as reality, but I see this as an area for substantial improvement.

[Matt Herron (Sr)]

I don't pretend to be a techie on the subject of self-launch gliders, but I do have some personal experience to offer. I went to Lithuania in October 2018 to test fly and then buy a LAK17b Mini FES.
The demo Mini was not ready for flying when I arrived, so I made two flights in a LAK17B FES in 18 meter configuration that had been modified with a higher wheel gear and the more powerful generation III battery pak to give it self-launch capability. I believe this is the same FES system that is now being supplied with the new Lak17C FES.

I had never flown a motor glider before, but I found launching the LAK17B to be dead simple: twist the power knob to 4500 RPM, keep the tail wheel on the ground until lift off is achieved and then follow a launch trajectory that seemed to me to be very similar to my aero tow experience. I made multiple engine starts and stops in the air to get the hang of the propeller docking system and then landed.

On the final day I flew the Mini from the same relatively short paved runway. The take off was much the same, except a bit quicker. Baltic fall weather did not offer any thermals but I found the Mini to be exceptionally responsive and easy to fly – even nicer than my LS-6, which has the reputation of being a very friendly glider. The reason for my Lithuania visit was to determine whether the Mini had good xcountry capabilities, a notable problem with many 13.5 meter ships. When I pushed her, she did not fall out of the sky, but held her own. I later learned that the Mini has recorded several flights in excess of 700 kilometers – good enough for me.

I also spent a day touring the LAK factory. I was impressed with the well-equipped and organized factory floor and the obvious professionalism of the 50-odd employees. The place had the feeling of a hard working but friendly family. LAK has been building gliders for 50 years, and it showed.

My Mini has been delivered, but I've not flown it yet. Still working my way through the FAA certification process. I'll write a report when I've had some initial flight experience, but meanwhile, here's a cover piece I wrote for Soaring in February 2019: http://front-electric-sustainer.com/PDF%20Articles/Mini%20and%20Me%20Soaring%20February%202019.pdf

[Eric Greenwell[_4_]]

Ron Gleason wrote on 4/11/2020 12:29 PM:
> On Saturday, 11 April 2020 11:51:57 UTC-6, Eric Greenwell wrote:
>> Luka Žnidarši� wrote on 4/11/2020 1:14 AM:
>>> Note that at LAK17C max power is 30kW. With such power climb performance are very good as there is no pylon drag.
>>>
>> The pylon mount allows a much greater choice in propellers, allowing it to
>> significantly exceed an FES in efficiency. The GP15, for example, uses a three
>> blade propeller, and the blade shape is not constrained by the shape of the nose,
>> or the need for low drag when the motor is stopped. The pylon is a single,
>> streamlined strut that will produce almost insignificant drag at climb speeds,
>> even when accounting for the open doors. I base that claim on how well my ASH 26 E
>> thermals with the engine partially retracted for cooling, a much dirtier object
>> than the GP15 pylon.
>>
>> --
>> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
>> - "A Guide to Self-Launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>
> While classified as a CLass 2 Hang Glider, this machine fits the objectives you defined https://www.youtube.com/watch?v=G3qfW3ydZuY&t=178s
>
> Yes they are ridiculously expensive

It appears to be a fine machine, certainly smaller/lighter (maybe not simpler),
but it's gliding performance is far less than my requirement: performance that
equals or exceeds an ASH26E. The price is close to my cost for a GP15.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[jfitch]

On Saturday, April 11, 2020 at 1:09:56 PM UTC-7, Luka Žnidarši� wrote:
> Dne sobota, 11. april 2020 12.02.19 UTC+2 je oseba jld napisala:
> > The propulsion efficiency has much more direct effect than pylon drag.
> > In fact, for Takeoff and climb performance, the overall glider drag has secondary effect compared to aircraft weight and available thrust.
> > Without fuselage interference and opportunities for larger props, the pylon mounted motor provides a significant efficiency advantage. This has a direct effect on climb performance in terms of climb rate and altitude gain..
> > Running large battery packs, beside running cooler, also provides better energy efficiency and installing large batteries in the wing reduces overall structure weight and provides better flying handling characteristics due to CG.
> >
> > FES is a nice solution, especially for retrofit of existing gliders.
> > For a brand new design, there are opportunities for better optimizations.
> > Is GP at the optimum, probably not (yet:-), but they have certainly made good design decisions for both teh glider and the propulsion.
>
> Actually efficiency of glider in powered mode is quite important:
> 1.Efficiency of FES powered glider in powered mode is the same as in glide mode.
>
> FES powered glider, L/D 50 and 500kg T.O.W, minimum sink 0,5m/s:
> -required thrust for level flight; 500kg/50=10kg which is 100N
> -another 100N is required for climb rate 0,5m/s; 200N
> -another 100N is required for climb rate 1,0m/s; 300N
> -another 100N is required for climb rate 1,5m/s; 400N
> -another 100N is required for climb rate 2,0m/s; 500N
> -another 100N is required for climb rate 2,5m/s; 600N
> -another 100N is required for climb rate 3,0m/s; 700N
>
> 2.Efficiency of most powered gliders with retractable systems is about half (or even worse) of the efficiency as glider. Note that pylon drag with its big pulley or motor on top is still there even if propeller is rotating :). Like flying with half opened airbrakes.
>
> Pylon powered glider, with pylon extended, L/D 25 and 500kg T.O.W, minimum sink 1,0m/s:
> -required thrust for level flight; 500/25=20kg which is 200N
> -another 200N for climb rate 1m/s; 400N
> -another 200N for climb rate 2m/s; 600N
> -another 200N for climb rate 3m/s; 800N
>
> Efficiency of propeller not depends just on its diameter but also how much thrust such propeller should create. Even with smaller propeller diameter is possible to achieve good efficiency when required thrust is smaller, for instance during level flight or more shallow climb rates and this is typical use of FES. As you can see above, with FES required thrust for climb rate 1m/s is 300N, while with pylon for 1m/s is required 400N. This seems to be possible to offset with higher efficiency of bigger propeller, but bigger propeller requires higher torque. With direct drive electric motors higher torque can be achieved only with bigger motor diameter, but this means even more drag. With more drag it would be required also more thrust from propeller, which means higher power, higher energy consumption, bigger battery packs, more weight. Another possibility is to install motor in the fuselage and transfer power with belts to pylon, but there are quite high loses in efficiency, more that most engineers imagine and so not in equation. Diameter of upper pulley is usually bigger than lower pulley, due to reduction ratio, which is not helpful from drag viewpoint. And number of propeller blades do not affect much to its efficiency. It is only helpful if prop loading it very high but is also possible to increase chord of propeller blades to some extent.
>
> So 700N for FES with 1m prop diameter or 800N with 1,4m (or bigger) retractable system to climb 3m/s, seems to be in advantage of pylon due to better prop efficiency. However, when you put all factors into equation, result is almost the same.
> However, in the range of lower power settings FES is much more efficient (100N vs 200N).
> In case of FES self-launch, I feel much safer on critical altitudes till 50m, as in case of motor failure there is still available pure glider efficiency to perform a turn back if required. With retractable systems you end up flying a brick, where you can hardly afford turning back without risk of spin entry.
> Another big FES advantage is non problematic starting of engine above non landable terrain.
> With retractable systems you should never try to start engine without landing field below, as in case that engine do not start and cannot be retracted for any reason, you end up flying a brick.
> Clearly propeller clearance is advantage of pylon, but with pylon there are more problems related to take-off in side-wind conditions. With FES there is much better rudder efficiency.
> It is hard to compare FES with retractable systems, as they are very different in also in flying style, and all pilots will prefer one over another.
> I believe that in next months there will be more information about LAK17C FES.

Are you sure this analysis is correct? It does not match my understanding of aerodynamics. Yes, the engine pylon will add drag and reduce L/D by some amount. However it is parasitic drag, and once overcome at climb speed need not be overcome again and again as climb increases. Lift and drag at climb speed remain constant regardless of climb rate, once airborne in unaccelerated flight. Additional thrust is put directly to work as climb rate. In your example 100N extra would be required to push the pylon through the air, but every 100N above that contributes the same to climb on either ship. Where else would the energy go?

[jld]

Luka,

I don't want to bother the group with too many details but please, don't present data in a biased way.

EFFECT of L/D:
The L/D of the glider only affects the thrust required for level flight.
Because we care about takeoff and climb, a large majority of the thrust produced is used for the work required to climb. This is independent from L/D, it is just about lifting the weight of the glider!
The equation can be simplified to : vertical speed (m/s) = glider speed (m/s) x Thrust (N) / weight (N).
Thrust being the thrust from the prop minus the thrust required for level flight.
Just to illustrate using your example:
With FES, to climb at 2.5 m/s requires 600 N. In the 600 N, only 100 N are dependent of L/D and 500 are dependent of weight of the glider.

PYLON POWERED GLIDER L/D:
You use L/D 25 for gliders with pylon installation.
This is too high for gliders with combustion engine which have L/D below 20 when pylon is extended.
This is too low for gliders with an electric motor on a single clean mast and a foldable prop. The drag penalty should not exceed 20-25 N at climb speed which means L/D should be at least 40 with your example of a 500 kg ship with 50 L/D when clean.
This means that when the engine is out, you still get a nice L/D allowing you more options, almost like with FES.

Back to climb performance, to climb at 2.5 m/s with a pylon would require an additional 25 N due to the drag.

Using your examples again, if you estimate the difference of climb thrust between FES and pylon to be around 100 N, there is a 75 N (100-25) advantage to the pylon mounted motor!
This will be more than that in reality since, beside prop diameter, the prop can be further optimized with a pylon installation (number of blades, shape, etc.).

Just a note concerning thrust. When you claim 700 N of thrust, it is probably static with 30 kw (not the current 22 kw motor). The climb thrust at 30 m/s assuming 25 kw continuous power is probably more around 500-550 N.

There are indeed pros and cons of FES versus Pylon but, if the goal is to allow high pressure altitude operation and high altitude gain (>4000 m on a charge), Pylon has an advantage. If the goal is to use the motor more like a sustainer, then FES is a nice solution.

More important, a lighter glider (with high aspect ratio wing and low surface to maintain good performance / wing loading) will significantly improve takeoff and climb performance.

Regards.

Ps: Please don't use this type of dangerous suggestion: "Another big FES advantage is non problematic starting of engine above non landable terrain". You may decide to start engine at lower altitude with FES but it should always be above a landable area.

[David Shelton]

> Are you sure this analysis is correct? It does not match my understanding of aerodynamics. Yes, the engine pylon will add drag and reduce L/D by some amount. However it is parasitic drag, and once overcome at climb speed need not be overcome again and again as climb increases. Lift and drag at climb speed remain constant regardless of climb rate, once airborne in unaccelerated flight. Additional thrust is put directly to work as climb rate. In your example 100N extra would be required to push the pylon through the air, but every 100N above that contributes the same to climb on either ship. Where else would the energy go?

Part of the problem is that the pylon is located behind the prop, rather in the free stream. Increased thrust will cause higher pylon drag, even if you maintain the same airspeed.

Trim drag may be another factor. The pylon configuration has a substantial pitching moment. More thrust will require more trim drag.

Still, neither configuration has a clear advantage for all missions. However, if I ever switch to electric, it will likely be for increased reliabiity.. In this reguard, FES would be the clear winner. They pylon in my ship is a Rube Goldberg system with a manual crank, chain, gear rack, gas strut, micro switches, hinged doors, cable stay, prop brake system, a lock to keep the engine seure while retracted, and a little mirror so I can see what the hell I'm doing. It's kind of amazing they figured this out before CAD!

[jfitch]

On Saturday, April 11, 2020 at 5:16:32 PM UTC-7, David Shelton wrote:
> > Are you sure this analysis is correct? It does not match my understanding of aerodynamics. Yes, the engine pylon will add drag and reduce L/D by some amount. However it is parasitic drag, and once overcome at climb speed need not be overcome again and again as climb increases. Lift and drag at climb speed remain constant regardless of climb rate, once airborne in unaccelerated flight. Additional thrust is put directly to work as climb rate. In your example 100N extra would be required to push the pylon through the air, but every 100N above that contributes the same to climb on either ship. Where else would the energy go?
>
> Part of the problem is that the pylon is located behind the prop, rather in the free stream. Increased thrust will cause higher pylon drag, even if you maintain the same airspeed.
>
> Trim drag may be another factor. The pylon configuration has a substantial pitching moment. More thrust will require more trim drag.
>
> Still, neither configuration has a clear advantage for all missions. However, if I ever switch to electric, it will likely be for increased reliabiity. In this reguard, FES would be the clear winner. They pylon in my ship is a Rube Goldberg system with a manual crank, chain, gear rack, gas strut, micro switches, hinged doors, cable stay, prop brake system, a lock to keep the engine seure while retracted, and a little mirror so I can see what the hell I'm doing. It's kind of amazing they figured this out before CAD!

Surely the increase in pylon drag due to increased thrust is at least equaled in the FES, where the prop wash is blown directly over the fuselage, wing root, and enpennage. But in either case it is no where near the total drag of the aircraft. I agree the FES is mechanically simpler.

Despite all the hand wringing, in over 250 self launches and a few retrieves or relights in my ASH26, I have experienced only one failure to start, and that on the first ground check after the winter layup. I have had a very few incidents of unscheduled maintenance, in every case caught at annual or during preflight, and none of which would have resulted in a failure to start. I.e, 100% reliability. Nevertheless, I consider starting the engine outside of sure and easy glide to a known landing site foolhardy and know many pilots who have done so resulting in considerable drama.

[Eric Greenwell[_4_]]

On Saturday, April 11, 2020 at 1:09:56 PM UTC-7, Luka Žnidarši� wrote:
...
> In case of FES self-launch, I feel much safer on critical altitudes till 50m,
> as in case of motor failure there is still available pure glider efficiency to
> perform a turn back if required. With retractable systems you end up flying a
> brick, where you can hardly afford turning back without risk of spin entry.
> Another big FES advantage is non problematic starting of engine above non
> landable terrain. With retractable systems you should never try to start engine
> without landing field below, as in case that engine do not start and cannot be
> retracted for any reason, you end up flying a brick. Clearly propeller
> clearance is advantage of pylon, but with pylon there are more problems related
> to take-off in side-wind conditions. With FES there is much better rudder
> efficiency. It is hard to compare FES with retractable systems, as they are
> very different in also in flying style, and all pilots will prefer one over
> another.

One: My ASH26E is hardly a "brick" with the pylon and gear extended, and I can
turn around to land back with just 200' AGL just as well as an unpowered glider
(for which I always used the 200' AGL criteria if the tow failed). I tested
that years ago - it loses very little during a 180 degree turn. A friend found the
same thing for his DG 400.

Two: It is true the FES pilot will have a better L/D after a failed start than a
similar engine/pylon glider (like my ASH26E) with a failed start AND a failed
retract. It is not necessary to be over a field, but only within gliding reach
with the mast extended. It is the same decision process for either propulsion
type. Unlike the ASH26E, the GP15 can risk a start almost as far from the landing
area as a comparable FES glider. Because mast is streamlined like an airfoil, and
the propeller folds in-line with the motor, it has much less drag than the
conventional "engine on a stick".

Three: I am not aware of any crosswind problems for engine/pylon gliders caused by
lack of rudder efficiency. The propeller air goes directly past the rudder from
the nearby propeller on the pylon, increasing the rudder's effectiveness at least
as much as the FES, where the propeller is much further from the rudder.
Regardless, it is not the rudder that is used to keep the glider going straight
down the runway in a crosswind, but the steerable tailwheel (every glider should
have one). On my ASH26E, I hold the tail wheel on the ground until about 25 knots
airspeed, then lift it off by moving from negative flaps to positive flaps (soft
fields may need a different technique).

Four: Off course, pilots will generally prefer one system over the other, but I
think some (many?) will find the GP15 much closer in operation to the FES gliders
than to the gasoline "engine on a pylon" gliders like my ASH26E. From clicking the
"mast up" switch to full power on the GP15 is 5 seconds; retraction is about 3
seconds. Compare this to my ASH26E, with about 20 seconds to initial power, and
about 30 seconds to retract partially for cooling, then another 1 to 4 minutes to
full retraction after cooling.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Eric Greenwell[_4_]]

jfitch wrote on 4/11/2020 6:54 PM:
> Despite all the hand wringing, in over 250 self launches and a few retrieves or relights in my ASH26, I have experienced only one failure to start, and that on the first ground check after the winter layup. I have had a very few incidents of unscheduled maintenance, in every case caught at annual or during preflight, and none of which would have resulted in a failure to start. I.e, 100% reliability. Nevertheless, I consider starting the engine outside of sure and easy glide to a known landing site foolhardy and know many pilots who have done so resulting in considerable drama.

My experience with my ASH26E is essentially the same as Jon's, but with about
700-800 self-launches and over 200 in-flight restarts, with only one start
failure. And, I also always have a field within an easy glide before attempting to
start the engine.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[jld]

"Part of the problem is that the pylon is located behind the prop, rather in the free stream. Increased thrust will cause higher pylon drag, even if you maintain the same airspeed"
==> You should look at modern pylon solutions with clean single pylon and pusher foldable prop.
==> FES is not free stream at all, due to fuselage interference.

"Still, neither configuration has a clear advantage for all missions. However, if I ever switch to electric, it will likely be for increased reliability. In this regard, FES would be the clear winner. They pylon in my ship ....."
==> again there has been lessons learned over time since ASH, DG, SH and Lange designed their propulsion systems. Pylon designed for electric pushers can have much less components and demonstrate much better reliability.
==> A possible advantage of electrical solutions is that it becomes practical for glider manufacturers to run automatically, in advance to users, many cycles on their prototype to identify early design issues and reliability risks. You can run 1000 cycles in a few weeks and get more cycle than any pilot will do over many years.
==> If your mission does not require to climb 1000 m AGL before starting your task and you don't have the expectation to have the energy to come back home even when 100 km away, then FES is a solution. Otherwise, Pylon mounted electric pusher is probably the way to go.


"Nevertheless, I consider starting the engine outside of sure and easy glide to a known landing site foolhardy and know many pilots who have done so resulting in considerable drama"
==> Amen

[Dave Walsh[_2_]]

A couple of points: -
(i) On the Antares 20E the pylon is in front of the prop.
(ii) "Bricks" have various glide angles: The Antares20E is 30:1
with the engine up and the prop windmilling so better than
many basic two seat trainers.

[[email protected]]

On Sunday, April 12, 2020 at 1:00:05 PM UTC+1, Dave Walsh wrote:
> A couple of points: -
> (i) On the Antares 20E the pylon is in front of the prop.
> (ii) "Bricks" have various glide angles: The Antares20E is 30:1
> with the engine up and the prop windmilling so better than
> many basic two seat trainers.

Why would the pylon being in front or behind the prop make a meaningful difference? Whichever way, you're either sucking or blowing air through it at a speed proportional to the thrust you're trying to make?

[kinsell]

On 4/10/20 9:46 AM, Magnus wrote:
> On Wednesday, April 8, 2020 at 5:14:54 PM UTC+2, wrote:
>> Hello Magnus,
>>
>> I can't respond to flight characteristics of the two self-launchers you mentioned (LAK-17C and GP-Gliders JETA). But, I can say that I sat in a JETA and also have JETA serial number 5 on order.
>>
>> The JETA MTOG, per the provisional flight manual, is 525KG (1157 lbs). Below are the advertised self-launch numbers with the larger battery:
>>
>> a) 5 x takeoff and climb to 800 m (2,600 feet) altitude, or
>> b) 1 x takeoff and climb to 800 m altitude + 150 km (80 nm) autonomy, or
>> c) 1 x takeoff and total climb to 4 500 m (14,700 feet)
>> d) my number: aero tow and 185 km (100nm) autonomy based on 20 nm/launch.
>>
>> Climb rate: >3,7 m/s (728 fpm or 7.2 knots)
>>
>> takeoff distance: 180 m (590 feet)
>>
>> I visited the GP-Glider factory near Krosno, Poland (jokingly to make sure that they weren't operating out of a tent). I was happy that they were doing things correctly. A visit to the LAK factory would have given me a balanced experience, but I was not able to do that.
>>
>> Raul Boerner
>> LS-6BWL
>
> Hi Raul,
> When is your delivery of the Jeta? I am really interested in your experiences. Where are you flying?
> According to the max wing loading of 60/37 kg/m2 the MTOM is below 475/285kg UL with a wing area of 7.77m2 - this also is indicated on the website. I suppose the take-off distance is without ballast but it is still good. How/where do you register it as UL?
>

I'd be interested in hearing when the order was placed, what the
original delivery date was supposed to be, and now when Raul
reallistically expects to get it.

[jld]

> Why would the pylon being in front or behind the prop make a meaningful difference? Whichever way, you're either sucking or blowing air through it at a speed proportional to the thrust you're trying to make?

Indeed front or behind does not make a lot of difference.
The cross section and shape of pylon is what matters.
The point of having the pylon in front is mainly to use foldable prop which lowers drag significantly when engine is not operating.

[Dan Marotta]

I would think that electric motors have a very real advantage in not
needing much, if any, warm up time.Â* Whereas my Stemme starts reliably
every time, after a long cold soak it requires a lot of time to get the
oil temperature up to a level where I'm willing to advance the
throttle.Â* I feel that I therefore need to be more considerate of what
is below the aircraft...

On 4/11/2020 7:54 PM, jfitch wrote:
> On Saturday, April 11, 2020 at 5:16:32 PM UTC-7, David Shelton wrote:
>>> Are you sure this analysis is correct? It does not match my understanding of aerodynamics. Yes, the engine pylon will add drag and reduce L/D by some amount. However it is parasitic drag, and once overcome at climb speed need not be overcome again and again as climb increases. Lift and drag at climb speed remain constant regardless of climb rate, once airborne in unaccelerated flight. Additional thrust is put directly to work as climb rate. In your example 100N extra would be required to push the pylon through the air, but every 100N above that contributes the same to climb on either ship. Where else would the energy go?
>> Part of the problem is that the pylon is located behind the prop, rather in the free stream. Increased thrust will cause higher pylon drag, even if you maintain the same airspeed.
>>
>> Trim drag may be another factor. The pylon configuration has a substantial pitching moment. More thrust will require more trim drag.
>>
>> Still, neither configuration has a clear advantage for all missions. However, if I ever switch to electric, it will likely be for increased reliabiity. In this reguard, FES would be the clear winner. They pylon in my ship is a Rube Goldberg system with a manual crank, chain, gear rack, gas strut, micro switches, hinged doors, cable stay, prop brake system, a lock to keep the engine seure while retracted, and a little mirror so I can see what the hell I'm doing. It's kind of amazing they figured this out before CAD!
> Surely the increase in pylon drag due to increased thrust is at least equaled in the FES, where the prop wash is blown directly over the fuselage, wing root, and enpennage. But in either case it is no where near the total drag of the aircraft. I agree the FES is mechanically simpler.
>
> Despite all the hand wringing, in over 250 self launches and a few retrieves or relights in my ASH26, I have experienced only one failure to start, and that on the first ground check after the winter layup. I have had a very few incidents of unscheduled maintenance, in every case caught at annual or during preflight, and none of which would have resulted in a failure to start. I.e, 100% reliability. Nevertheless, I consider starting the engine outside of sure and easy glide to a known landing site foolhardy and know many pilots who have done so resulting in considerable drama.

--
Dan, 5J

[BG[_4_]]

On Saturday, April 11, 2020 at 8:06:30 PM UTC-7, Eric Greenwell wrote:
> On Saturday, April 11, 2020 at 1:09:56 PM UTC-7, Luka Žnidarši� wrote:
> ...
> > In case of FES self-launch, I feel much safer on critical altitudes till 50m,
> > as in case of motor failure there is still available pure glider efficiency to
> > perform a turn back if required. With retractable systems you end up flying a
> > brick, where you can hardly afford turning back without risk of spin entry.
> > Another big FES advantage is non problematic starting of engine above non
> > landable terrain. With retractable systems you should never try to start engine
> > without landing field below, as in case that engine do not start and cannot be
> > retracted for any reason, you end up flying a brick. Clearly propeller
> > clearance is advantage of pylon, but with pylon there are more problems related
> > to take-off in side-wind conditions. With FES there is much better rudder
> > efficiency. It is hard to compare FES with retractable systems, as they are
> > very different in also in flying style, and all pilots will prefer one over
> > another.
>
> One: My ASH26E is hardly a "brick" with the pylon and gear extended, and I can
> turn around to land back with just 200' AGL just as well as an unpowered glider
> (for which I always used the 200' AGL criteria if the tow failed). I tested
> that years ago - it loses very little during a 180 degree turn. A friend found the
> same thing for his DG 400.
>
> Two: It is true the FES pilot will have a better L/D after a failed start than a
> similar engine/pylon glider (like my ASH26E) with a failed start AND a failed
> retract. It is not necessary to be over a field, but only within gliding reach
> with the mast extended. It is the same decision process for either propulsion
> type. Unlike the ASH26E, the GP15 can risk a start almost as far from the landing
> area as a comparable FES glider. Because mast is streamlined like an airfoil, and
> the propeller folds in-line with the motor, it has much less drag than the
> conventional "engine on a stick".
>
> Three: I am not aware of any crosswind problems for engine/pylon gliders caused by
> lack of rudder efficiency. The propeller air goes directly past the rudder from
> the nearby propeller on the pylon, increasing the rudder's effectiveness at least
> as much as the FES, where the propeller is much further from the rudder.
> Regardless, it is not the rudder that is used to keep the glider going straight
> down the runway in a crosswind, but the steerable tailwheel (every glider should
> have one). On my ASH26E, I hold the tail wheel on the ground until about 25 knots
> airspeed, then lift it off by moving from negative flaps to positive flaps (soft
> fields may need a different technique).
>
> Four: Off course, pilots will generally prefer one system over the other, but I
> think some (many?) will find the GP15 much closer in operation to the FES gliders
> than to the gasoline "engine on a pylon" gliders like my ASH26E. From clicking the
> "mast up" switch to full power on the GP15 is 5 seconds; retraction is about 3
> seconds. Compare this to my ASH26E, with about 20 seconds to initial power, and
> about 30 seconds to retract partially for cooling, then another 1 to 4 minutes to
> full retraction after cooling.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1


I find a huge difference in cross capability in my DG 800 on pavement vs. dirt or grass. You need help from the wheel on the ground to prevent weather vanning. I find the fringe turbulent thrust from the engine is not so effective on the rudder, standing behind the glider you fill most of the prop thrust is up near the elevator anyway. The pylon thrust line lifts the tail and reduces traction on the rear wheel. I have lost track of how many aborted takeoffs I have had in strong cross winds, while gliders being towed were doing just fine off dirt and grass..

[Eric Greenwell[_4_]]

BG wrote on 4/12/2020 9:45 AM:

>>
>> Three: I am not aware of any crosswind problems for engine/pylon gliders caused by
>> lack of rudder efficiency. The propeller air goes directly past the rudder from
>> the nearby propeller on the pylon, increasing the rudder's effectiveness at least
>> as much as the FES, where the propeller is much further from the rudder.
>> Regardless, it is not the rudder that is used to keep the glider going straight
>> down the runway in a crosswind, but the steerable tailwheel (every glider should
>> have one). On my ASH26E, I hold the tail wheel on the ground until about 25 knots
>> airspeed, then lift it off by moving from negative flaps to positive flaps (soft
>> fields may need a different technique).
>
>
> I find a huge difference in cross capability in my DG 800 on pavement vs. dirt or grass. You need help from the wheel on the ground to prevent weather vanning. I find the fringe turbulent thrust from the engine is not so effective on the rudder, standing behind the glider you fill most of the prop thrust is up near the elevator anyway. The pylon thrust line lifts the tail and reduces traction on the rear wheel. I have lost track of how many aborted takeoffs I have had in strong cross winds, while gliders being towed were doing just fine off dirt and grass..

I don't have any personal experience with the DG 800, but your description shows
it's very different in some respects from my ASH26E. I had no idea it was so bad,
or I would not have made such a general statement.

What measures have you tried to improve the soft field, crosswind takeoff? Are
your takeoffs unassisted? If so, have you tried placing the downwind wing on the
ground to help counteract the weathervaning from the wind?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[jfitch]

On Sunday, April 12, 2020 at 10:19:01 AM UTC-7, Eric Greenwell wrote:
> BG wrote on 4/12/2020 9:45 AM:
>
> >>
> >> Three: I am not aware of any crosswind problems for engine/pylon gliders caused by
> >> lack of rudder efficiency. The propeller air goes directly past the rudder from
> >> the nearby propeller on the pylon, increasing the rudder's effectiveness at least
> >> as much as the FES, where the propeller is much further from the rudder.

[Duster[_2_]]

Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.

[Dan Marotta]

I saw one in Robert Mudd's shop at Moriarty.Â* It appeared to be will
constructed and very roomy, but I think it's considered an ultra light
sailplane.Â* I'm not saying there's anything wrong with that, but it's my
opinion, and only my opinion, that it would be more of a floater than a
runner.Â* But it would be nice to cut the tow rope, so to speak.

On 4/13/2020 10:37 AM, Duster wrote:
> Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.

--
Dan, 5J

[Eric Greenwell[_4_]]

Duster wrote on 4/13/2020 9:37 AM:
> Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.
>
There at least one of them in the US, so contact them for experienced advice. I
believe the 2020 SSA convention had a presentation on it, and perhaps there was an
article in Soaring Magazine. There is also at least one gas engine Taurus in the
country, another source for info.

I've seen both of the referenced gliders fly at Parowan, the pilots and passengers
seemed to enjoy the experience. I do envy the ability to taxi upright.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Emir Sherbi]

El lunes, 13 de abril de 2020, 13:37:18 (UTC-3), Duster escribió:
> Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.

Very good motor, controller and battery pack.

I flew once a taurus with the I.C. engine, very comfy and fun to share with some one at your side.

But if you like competitive soaring, is out of the question.

[jld]

Taurus is a nice glider. Very roomy, nice side by side configuration when flying with friends or for instruction.
It is very well build.
Typical WL with 2 pilots is 38-40 kg/m2
The cruise performance is similar to lightly loaded standard class.
The climb performance is more like a heavy loaded standard.
It would be an excellent 2 seater with a wing more specifically designed for soaring.With modern 18m wings would make it a fantastic 2 seater.
I know the 503 version.
I have never flown the electro but it has too limited battery capacity for my need. It would need at least 10 kwh batteries for comfortable operation.

[2G]

On Monday, April 13, 2020 at 2:42:54 PM UTC-7, jld wrote:
> Taurus is a nice glider. Very roomy, nice side by side configuration when flying with friends or for instruction.
> It is very well build.
> Typical WL with 2 pilots is 38-40 kg/m2
> The cruise performance is similar to lightly loaded standard class.
> The climb performance is more like a heavy loaded standard.
> It would be an excellent 2 seater with a wing more specifically designed for soaring.With modern 18m wings would make it a fantastic 2 seater.
> I know the 503 version.
> I have never flown the electro but it has too limited battery capacity for my need. It would need at least 10 kwh batteries for comfortable operation.

Electric gliders won't cut it when you have to motor a was to the lift, like at Williams. Once, Jim Leedy and I motored from KRLD to Mt. Rainier in his Taifun to get to the wave lift.

Tom

[Eric Greenwell[_4_]]

2G wrote on 4/13/2020 5:54 PM:
> On Monday, April 13, 2020 at 2:42:54 PM UTC-7, jld wrote:
>> Taurus is a nice glider. Very roomy, nice side by side configuration when flying with friends or for instruction.
>> It is very well build.
>> Typical WL with 2 pilots is 38-40 kg/m2
>> The cruise performance is similar to lightly loaded standard class.
>> The climb performance is more like a heavy loaded standard.
>> It would be an excellent 2 seater with a wing more specifically designed for soaring.With modern 18m wings would make it a fantastic 2 seater.
>> I know the 503 version.
>> I have never flown the electro but it has too limited battery capacity for my need. It would need at least 10 kwh batteries for comfortable operation.
>
> Electric gliders won't cut it when you have to motor a was to the lift, like at Williams. Once, Jim Leedy and I motored from KRLD to Mt. Rainier in his Taifun to get to the wave lift.

The Williams case is one I considered before choosing the Jeta. On the map, it
looks like about 20 NM the to hills to the west. Most electric gliders have that
much range; eg, the Gp15 Jeta with the large battery could launch, motor the 20
miles, and still have about 55-60 NM range left. The small battery would only have
30-35 nn range left, though. The AS34 would have about 45 NM range left after
motoring from Williams to the hills; the miniLak FES also about 45 NM, maybe more.

Everyone knows the gasoline powered self-launchers all have powered ranges that
exceed the best electric range, but that is irrelevant for most of the people
buying an electric glider. They want to eliminate the tow and dramatically
increase their chances of getting home, and the electric glider gives them what
they want. If you dream of flights that require hours of power, or airfields that
don't have electricity, you must stay with gasoline.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[2G]

On Monday, April 13, 2020 at 7:48:51 PM UTC-7, Eric Greenwell wrote:
> 2G wrote on 4/13/2020 5:54 PM:
> > On Monday, April 13, 2020 at 2:42:54 PM UTC-7, jld wrote:
> >> Taurus is a nice glider. Very roomy, nice side by side configuration when flying with friends or for instruction.
> >> It is very well build.
> >> Typical WL with 2 pilots is 38-40 kg/m2
> >> The cruise performance is similar to lightly loaded standard class.
> >> The climb performance is more like a heavy loaded standard.
> >> It would be an excellent 2 seater with a wing more specifically designed for soaring.With modern 18m wings would make it a fantastic 2 seater.
> >> I know the 503 version.
> >> I have never flown the electro but it has too limited battery capacity for my need. It would need at least 10 kwh batteries for comfortable operation.
> >
> > Electric gliders won't cut it when you have to motor a was to the lift, like at Williams. Once, Jim Leedy and I motored from KRLD to Mt. Rainier in his Taifun to get to the wave lift.
>
> The Williams case is one I considered before choosing the Jeta. On the map, it
> looks like about 20 NM the to hills to the west. Most electric gliders have that
> much range; eg, the Gp15 Jeta with the large battery could launch, motor the 20
> miles, and still have about 55-60 NM range left. The small battery would only have
> 30-35 nn range left, though. The AS34 would have about 45 NM range left after
> motoring from Williams to the hills; the miniLak FES also about 45 NM, maybe more.
>
> Everyone knows the gasoline powered self-launchers all have powered ranges that
> exceed the best electric range, but that is irrelevant for most of the people
> buying an electric glider. They want to eliminate the tow and dramatically
> increase their chances of getting home, and the electric glider gives them what
> they want. If you dream of flights that require hours of power, or airfields that
> don't have electricity, you must stay with gasoline.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

The launch has to be 4kft, min and the distance is more like 22nm. And what if the lift is further into the hills? And what if you have a headwind? And if you don't connect you don't have a glide back to Williams. The same thing goes for Minden. The margins are either non-existent or too thin for my tastes. Of course, you could always get a tow. In fact, save the cost of a FES and fly a pure glider.

Tom

[[email protected]]

On Monday, April 13, 2020 at 9:37:18 AM UTC-7, Duster wrote:
> Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.

There are 4 Electro's in the USA and about a dozen Rotax powered. I've flown a Rotax-powered one for about 10 years, but only have a few flights in an Electro. It flies like an older generation, lightly loaded 15 meter ship.. Lots of fun soaring, but not for unhandicapped competition or records.

The company's objective in designing the electric version was to have it achieve the same performance, at the same price, as the gas powered. I understand that the electric will climb slightly faster (bigger prop, IIRC), and the price probably isn't that much more than the Rotax version. I think the empty weight is similar, though the batteries consume a lot of space.

But the run time, like all of the electrics, is the big difference. I think Pipistrel used to advertise 6,000' of climb on a charge, though that was a while back and they probably have better numbers today. (The Rotax powered version has a max fuel capacity of something like 14 gallons (with dual tanks). I have only the single tank configuration, but have never had "range anxiety" with probably over an hour of run time, should it be needed. (Typical flight has 5-7 minutes for initial launch and another 5-10 minutes of run time if I need a relight, and I would guess that the Electros have a similar profile.))

The solar trailer for the Electro is quite cool. You can park at an unelectrified gliderport, and the sun charges the battery array in the trailer. Then you hook-up your Taurus overnight and recharge the on-board batteries. Rinse and repeat.

Pipistrel has a big lead over others in actual, in-the-field application and improvements vs. projected and theoretical systems. If they elected to market their systems in a higher-performance sailplane I think they would have a superior product.

[2G]

On Monday, April 13, 2020 at 9:49:26 PM UTC-7, wrote:
> On Monday, April 13, 2020 at 9:37:18 AM UTC-7, Duster wrote:
> > Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.
>
> There are 4 Electro's in the USA and about a dozen Rotax powered. I've flown a Rotax-powered one for about 10 years, but only have a few flights in an Electro. It flies like an older generation, lightly loaded 15 meter ship. Lots of fun soaring, but not for unhandicapped competition or records.
>
> The company's objective in designing the electric version was to have it achieve the same performance, at the same price, as the gas powered. I understand that the electric will climb slightly faster (bigger prop, IIRC), and the price probably isn't that much more than the Rotax version. I think the empty weight is similar, though the batteries consume a lot of space.
>
> But the run time, like all of the electrics, is the big difference. I think Pipistrel used to advertise 6,000' of climb on a charge, though that was a while back and they probably have better numbers today. (The Rotax powered version has a max fuel capacity of something like 14 gallons (with dual tanks). I have only the single tank configuration, but have never had "range anxiety" with probably over an hour of run time, should it be needed. (Typical flight has 5-7 minutes for initial launch and another 5-10 minutes of run time if I need a relight, and I would guess that the Electros have a similar profile.))
>
> The solar trailer for the Electro is quite cool. You can park at an unelectrified gliderport, and the sun charges the battery array in the trailer. Then you hook-up your Taurus overnight and recharge the on-board batteries. Rinse and repeat.
>
> Pipistrel has a big lead over others in actual, in-the-field application and improvements vs. projected and theoretical systems. If they elected to market their systems in a higher-performance sailplane I think they would have a superior product.

For VFR cross country flight the FAA requires you to have a 30 minute fuel reserve. Note that electric gliders don't even have 30 minutes of run time, let alone a reserve. All this discussion assumes running the battery totally flat - no reserve WHATSOEVER and perfect battery performance (no degradation for temperature or age). This is an unacceptable level of even token, lip-service safety. GIVE ME A BREAK!

Tom

[Tim Taylor]

The last few comments on this thread are a really not useful. Each aircraft fits a specific mission. There has been mentioned of needing redundant engines, needing hours of engine operation time, etc, etc. We are not flying airplanes, they are gliders first with motors to allow either take-off or the abilty to sustain.

There is no right answer, each fits the needs of the pilot. Some may want a few miles of sustaining (traditional turbo or non-launching FES), some may want just enough to launch, some want both, snd some want redundant systems so they can fly out of reach of safe landing sites.

Each design is a compromise and ultimately has to fit the needs of the owner. There is no right or wrong design. Arguing over which one is better is like arguing over which flavor of ice cream is better.

[Eric Greenwell[_4_]]

2G wrote on 4/13/2020 9:19 PM:
> On Monday, April 13, 2020 at 7:48:51 PM UTC-7, Eric Greenwell wrote:
>> 2G wrote on 4/13/2020 5:54 PM:

>>> Electric gliders won't cut it when you have to motor a was to the lift, like at Williams. Once, Jim Leedy and I motored from KRLD to Mt. Rainier in his Taifun to get to the wave lift.
>>
>> The Williams case is one I considered before choosing the Jeta. On the map, it
>> looks like about 20 NM the to hills to the west. Most electric gliders have that
>> much range; eg, the Gp15 Jeta with the large battery could launch, motor the 20
>> miles, and still have about 55-60 NM range left. The small battery would only have
>> 30-35 nn range left, though. The AS34 would have about 45 NM range left after
>> motoring from Williams to the hills; the miniLak FES also about 45 NM, maybe more.
>>
>> Everyone knows the gasoline powered self-launchers all have powered ranges that
>> exceed the best electric range, but that is irrelevant for most of the people
>> buying an electric glider. They want to eliminate the tow and dramatically
>> increase their chances of getting home, and the electric glider gives them what
>> they want. If you dream of flights that require hours of power, or airfields that
>> don't have electricity, you must stay with gasoline.
>>
>> --
>> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
>> - "A Guide to Self-Launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>
> The launch has to be 4kft, min and the distance is more like 22nm. And what if the lift is further into the hills? And what if you have a headwind? And if you don't connect you don't have a glide back to Williams. The same thing goes for Minden. The margins are either non-existent or too thin for my tastes. Of course, you could always get a tow. In fact, save the cost of a FES and fly a pure glider.

There are several ways to deal with your worst case scenario:
1) don't fly on a difficult day
2) take a 5 mile, 4000' tow, leaving plenty of reserve to return to Williams
3) accept the possibility you might have to land at Antelope Valley
4) own a GP15: motor the 25 NM to 4000', and have 45-50 NM range left.

For 4), there no worries about getting back to Williams with that 10 knot tail
wind, 2500 agl height where you gave up trying to connect. The AS34 and miniLak
should be OK, too. Connecting with difficult lift will be easier in the electrics:
run at low power while searching around until you find something, turn it off, and
5 seconds later you are flying a glider again. Maybe not quite so easy in the
AS34, with it's more conventional pylon.

The fact is, most people do not fly where a lot of range is required, and most are
currently flying gliders with ZERO powered range (pure gliders). To these pilots,
the range of current electric gliders is very appealing. Think about it: if
maximum range was the crucial factor in selecting a motorglider, we'd all be
flying Stemme S10s! Right, Dan?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[[email protected]]

On Tuesday, April 14, 2020 at 2:14:17 AM UTC-4, Tim Taylor wrote:
> The last few comments on this thread are a really not useful. Each aircraft fits a specific mission. There has been mentioned of needing redundant engines, needing hours of engine operation time, etc, etc. We are not flying airplanes, they are gliders first with motors to allow either take-off or the abilty to sustain.
>
> There is no right answer, each fits the needs of the pilot. Some may want a few miles of sustaining (traditional turbo or non-launching FES), some may want just enough to launch, some want both, snd some want redundant systems so they can fly out of reach of safe landing sites.
>
> Each design is a compromise and ultimately has to fit the needs of the owner. There is no right or wrong design. Arguing over which one is better is like arguing over which flavor of ice cream is better.

I'll describe the requirements I am trying to satisfy for me with my project. I suspect this is much like many but obviously not all.
1) The glider needs to be practical for one person to assemble in a reasonable period of time without heavy lifting. This means a ship that is not more than about 100 lb heavier than it's similar non powered counterpart.
2) Self launch capability with acceptable margins. I am using a takeoff distance of 900 feet, off pavement, and climb rate of at least 400 feet per minute. Ability to fly off unpaved surface knowing takeoff distance will increase.
3) Battery capacity for a 2000 foot launch and 2500 feet reserve to save and get home or to a safe airport.
4)System must have sufficient motor cooling to allow high power settings long enough to get to a safe altitude before power reduction.
5) Practical charging. In my project the battery can be removed for charging away from the glider.
6) Existing proven airframe.
This is my "Wednesday afternoon" ship for when I have no tow pilot.
FWIW
UH

[Muttley]

There is another 2 seater side by side 20mtr electric in the works and they claim the basic version is ok for competitions.



http://www.reinerstemme.aero/

Muttley

[Jonathan St. Cloud]

On Monday, April 13, 2020 at 10:00:45 PM UTC-7, 2G wrote:
> On Monday, April 13, 2020 at 9:49:26 PM UTC-7, wrote:
> > On Monday, April 13, 2020 at 9:37:18 AM UTC-7, Duster wrote:
> > > Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.
> >
> > There are 4 Electro's in the USA and about a dozen Rotax powered. I've flown a Rotax-powered one for about 10 years, but only have a few flights in an Electro. It flies like an older generation, lightly loaded 15 meter ship. Lots of fun soaring, but not for unhandicapped competition or records.
> >
> > The company's objective in designing the electric version was to have it achieve the same performance, at the same price, as the gas powered. I understand that the electric will climb slightly faster (bigger prop, IIRC), and the price probably isn't that much more than the Rotax version. I think the empty weight is similar, though the batteries consume a lot of space.
> >
> > But the run time, like all of the electrics, is the big difference. I think Pipistrel used to advertise 6,000' of climb on a charge, though that was a while back and they probably have better numbers today. (The Rotax powered version has a max fuel capacity of something like 14 gallons (with dual tanks). I have only the single tank configuration, but have never had "range anxiety" with probably over an hour of run time, should it be needed.. (Typical flight has 5-7 minutes for initial launch and another 5-10 minutes of run time if I need a relight, and I would guess that the Electros have a similar profile.))
> >
> > The solar trailer for the Electro is quite cool. You can park at an unelectrified gliderport, and the sun charges the battery array in the trailer. Then you hook-up your Taurus overnight and recharge the on-board batteries. Rinse and repeat.
> >
> > Pipistrel has a big lead over others in actual, in-the-field application and improvements vs. projected and theoretical systems. If they elected to market their systems in a higher-performance sailplane I think they would have a superior product.
>
> For VFR cross country flight the FAA requires you to have a 30 minute fuel reserve. Note that electric gliders don't even have 30 minutes of run time, let alone a reserve. All this discussion assumes running the battery totally flat - no reserve WHATSOEVER and perfect battery performance (no degradation for temperature or age). This is an unacceptable level of even token, lip-service safety. GIVE ME A BREAK!
>
> Tom

That must be because airplane pilots think slower than helicopter pilots?

[Dan Marotta]

The pure glider never has any fuel reserve (molecules or electrons), yet
they go cross country all of the time.Â* Are you suggesting that flying
cross country in a pure glider is illegal?

On 4/13/2020 11:00 PM, 2G wrote:
> On Monday, April 13, 2020 at 9:49:26 PM UTC-7, wrote:
>> On Monday, April 13, 2020 at 9:37:18 AM UTC-7, Duster wrote:
>>> Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.
>> There are 4 Electro's in the USA and about a dozen Rotax powered. I've flown a Rotax-powered one for about 10 years, but only have a few flights in an Electro. It flies like an older generation, lightly loaded 15 meter ship. Lots of fun soaring, but not for unhandicapped competition or records.
>>
>> The company's objective in designing the electric version was to have it achieve the same performance, at the same price, as the gas powered. I understand that the electric will climb slightly faster (bigger prop, IIRC), and the price probably isn't that much more than the Rotax version. I think the empty weight is similar, though the batteries consume a lot of space.
>>
>> But the run time, like all of the electrics, is the big difference. I think Pipistrel used to advertise 6,000' of climb on a charge, though that was a while back and they probably have better numbers today. (The Rotax powered version has a max fuel capacity of something like 14 gallons (with dual tanks). I have only the single tank configuration, but have never had "range anxiety" with probably over an hour of run time, should it be needed. (Typical flight has 5-7 minutes for initial launch and another 5-10 minutes of run time if I need a relight, and I would guess that the Electros have a similar profile.))
>>
>> The solar trailer for the Electro is quite cool. You can park at an unelectrified gliderport, and the sun charges the battery array in the trailer. Then you hook-up your Taurus overnight and recharge the on-board batteries. Rinse and repeat.
>>
>> Pipistrel has a big lead over others in actual, in-the-field application and improvements vs. projected and theoretical systems. If they elected to market their systems in a higher-performance sailplane I think they would have a superior product.
> For VFR cross country flight the FAA requires you to have a 30 minute fuel reserve. Note that electric gliders don't even have 30 minutes of run time, let alone a reserve. All this discussion assumes running the battery totally flat - no reserve WHATSOEVER and perfect battery performance (no degradation for temperature or age). This is an unacceptable level of even token, lip-service safety. GIVE ME A BREAK!
>
> Tom

--
Dan, 5J

[Dan Marotta]

True dat, Eric.

For me the Stemme's range is only used to reposition to another soaring
location as I don't have a trailer.Â* That money is better spent on other
toys.Â* The big down side to the Stemme for me is it's limitation to
paved runways.Â* I know a lot of them are flown off of grass fields, but
there are none of those where I fly.Â* Gravel is also pretty much out of
the question, again for me, due to the cost of a propeller.

On 4/14/2020 7:17 AM, Eric Greenwell wrote:
> 2G wrote on 4/13/2020 9:19 PM:
>> On Monday, April 13, 2020 at 7:48:51 PM UTC-7, Eric Greenwell wrote:
>>> 2G wrote on 4/13/2020 5:54 PM:
>
>>>> Electric gliders won't cut it when you have to motor a was to the
>>>> lift, like at Williams. Once, Jim Leedy and I motored from KRLD to
>>>> Mt. Rainier in his Taifun to get to the wave lift.
>>>
>>> The Williams case is one I considered before choosing the Jeta. On
>>> the map, it
>>> looks like about 20 NM the to hills to the west. Most electric
>>> gliders have that
>>> much range; eg, the Gp15 Jeta with the large battery could launch,
>>> motor the 20
>>> miles, and still have about 55-60 NM range left. The small battery
>>> would only have
>>> 30-35 nn range left, though. The AS34 would have about 45 NM range
>>> left after
>>> motoring from Williams to the hills; the miniLak FES also about 45
>>> NM, maybe more.
>>>
>>> Everyone knows the gasoline powered self-launchers all have powered
>>> ranges that
>>> exceed the best electric range, but that is irrelevant for most of
>>> the people
>>> buying an electric glider. They want to eliminate the tow and
>>> dramatically
>>> increase their chances of getting home, and the electric glider
>>> gives them what
>>> they want. If you dream of flights that require hours of power, or
>>> airfields that
>>> don't have electricity, you must stay with gasoline.
>>>
>>> --
>>> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
>>> email me)
>>> - "A Guide to Self-Launching Sailplane Operation"
>>> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>>
>> The launch has to be 4kft, min and the distance is more like 22nm.
>> And what if the lift is further into the hills? And what if you have
>> a headwind? And if you don't connect you don't have a glide back to
>> Williams. The same thing goes for Minden. The margins are either
>> non-existent or too thin for my tastes. Of course, you could always
>> get a tow. In fact, save the cost of a FES and fly a pure glider.
>
> There are several ways to deal with your worst case scenario:
> 1) don't fly on a difficult day
> 2) take a 5 mile, 4000' tow, leaving plenty of reserve to return to
> Williams
> 3) accept the possibility you might have to land at Antelope Valley
> 4) own a GP15: motor the 25 NM to 4000', and have 45-50 NM range left.
>
> For 4), there no worries about getting back to Williams with that 10
> knot tail wind, 2500 agl height where you gave up trying to connect.
> The AS34 and miniLak should be OK, too. Connecting with difficult lift
> will be easier in the electrics: run at low power while searching
> around until you find something, turn it off, and 5 seconds later you
> are flying a glider again. Maybe not quite so easy in the AS34, with
> it's more conventional pylon.
>
> The fact is, most people do not fly where a lot of range is required,
> and most are currently flying gliders with ZERO powered range (pure
> gliders). To these pilots, the range of current electric gliders is
> very appealing. Think about it: if maximum range was the crucial
> factor in selecting a motorglider, we'd all be flying Stemme S10s!
> Right, Dan?
>

--
Dan, 5J

[jfitch]

On Tuesday, April 14, 2020 at 10:16:57 AM UTC-7, Dan Marotta wrote:
> The pure glider never has any fuel reserve (molecules or electrons), yet
> they go cross country all of the time.Â* Are you suggesting that flying
> cross country in a pure glider is illegal?
>
> On 4/13/2020 11:00 PM, 2G wrote:
> > On Monday, April 13, 2020 at 9:49:26 PM UTC-7, wrote:
> >> On Monday, April 13, 2020 at 9:37:18 AM UTC-7, Duster wrote:
> >>> Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.
> >> There are 4 Electro's in the USA and about a dozen Rotax powered. I've flown a Rotax-powered one for about 10 years, but only have a few flights in an Electro. It flies like an older generation, lightly loaded 15 meter ship. Lots of fun soaring, but not for unhandicapped competition or records.
> >>
> >> The company's objective in designing the electric version was to have it achieve the same performance, at the same price, as the gas powered. I understand that the electric will climb slightly faster (bigger prop, IIRC), and the price probably isn't that much more than the Rotax version. I think the empty weight is similar, though the batteries consume a lot of space..
> >>
> >> But the run time, like all of the electrics, is the big difference. I think Pipistrel used to advertise 6,000' of climb on a charge, though that was a while back and they probably have better numbers today. (The Rotax powered version has a max fuel capacity of something like 14 gallons (with dual tanks). I have only the single tank configuration, but have never had "range anxiety" with probably over an hour of run time, should it be needed. (Typical flight has 5-7 minutes for initial launch and another 5-10 minutes of run time if I need a relight, and I would guess that the Electros have a similar profile.))
> >>
> >> The solar trailer for the Electro is quite cool. You can park at an unelectrified gliderport, and the sun charges the battery array in the trailer. Then you hook-up your Taurus overnight and recharge the on-board batteries. Rinse and repeat.
> >>
> >> Pipistrel has a big lead over others in actual, in-the-field application and improvements vs. projected and theoretical systems. If they elected to market their systems in a higher-performance sailplane I think they would have a superior product.
> > For VFR cross country flight the FAA requires you to have a 30 minute fuel reserve. Note that electric gliders don't even have 30 minutes of run time, let alone a reserve. All this discussion assumes running the battery totally flat - no reserve WHATSOEVER and perfect battery performance (no degradation for temperature or age). This is an unacceptable level of even token, lip-service safety. GIVE ME A BREAK!
> >
> > Tom
>
> --
> Dan, 5J

In a glider, you only need about 6000 ft AGL at all times. That's about 30 minutes till you hit the dirt.

That's about what I try to maintain, flying in the Sierra/Great Basin. The valleys are around 4000 MSL, and below about 10,000 you are beginning the think about landing sites.

[[email protected]]

On Tuesday, April 14, 2020 at 1:00:45 AM UTC-4, 2G wrote:
> On Monday, April 13, 2020 at 9:49:26 PM UTC-7, wrote:
> > On Monday, April 13, 2020 at 9:37:18 AM UTC-7, Duster wrote:
> > > Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.
> >
> > There are 4 Electro's in the USA and about a dozen Rotax powered. I've flown a Rotax-powered one for about 10 years, but only have a few flights in an Electro. It flies like an older generation, lightly loaded 15 meter ship. Lots of fun soaring, but not for unhandicapped competition or records.
> >
> > The company's objective in designing the electric version was to have it achieve the same performance, at the same price, as the gas powered. I understand that the electric will climb slightly faster (bigger prop, IIRC), and the price probably isn't that much more than the Rotax version. I think the empty weight is similar, though the batteries consume a lot of space.
> >
> > But the run time, like all of the electrics, is the big difference. I think Pipistrel used to advertise 6,000' of climb on a charge, though that was a while back and they probably have better numbers today. (The Rotax powered version has a max fuel capacity of something like 14 gallons (with dual tanks). I have only the single tank configuration, but have never had "range anxiety" with probably over an hour of run time, should it be needed.. (Typical flight has 5-7 minutes for initial launch and another 5-10 minutes of run time if I need a relight, and I would guess that the Electros have a similar profile.))
> >
> > The solar trailer for the Electro is quite cool. You can park at an unelectrified gliderport, and the sun charges the battery array in the trailer. Then you hook-up your Taurus overnight and recharge the on-board batteries. Rinse and repeat.
> >
> > Pipistrel has a big lead over others in actual, in-the-field application and improvements vs. projected and theoretical systems. If they elected to market their systems in a higher-performance sailplane I think they would have a superior product.
>
> For VFR cross country flight the FAA requires you to have a 30 minute fuel reserve. Note that electric gliders don't even have 30 minutes of run time, let alone a reserve. All this discussion assumes running the battery totally flat - no reserve WHATSOEVER and perfect battery performance (no degradation for temperature or age). This is an unacceptable level of even token, lip-service safety. GIVE ME A BREAK!
>
> Tom

- I guess I should never venture out flying my motorless (pure) glider, since it has no fuel reserve at all! :-)

[Eric Greenwell[_4_]]

2G wrote on 4/13/2020 10:00 PM:
> Note that electric gliders don't even have 30 minutes of run time, let alone a reserve. All this discussion assumes running the battery totally flat - no reserve WHATSOEVER and perfect battery performance (no degradation for temperature or age). This is an unacceptable level of even token, lip-service safety. GIVE ME A BREAK!

Actually, several of them do exceed 30 minutes run time; eg, the Jeta with the
large battery has a nominal 150km range under power. That's at about 100kph,
yielding a 90 minute run, and a few minutes longer if you include the launch and
climb to 2500' AGL. The AS34 has a similar run time, the miniLak about 60 minutes,
plus launch time.

The discussion does not assume running the batteries totally flat; eg, the GP15
battery is limited to a 90% discharge to greatly extend it's life. Of course,
temperature and age will affect performance, as it can with gasoline gliders.
Electrics do have an advantage at high density altitudes: their power remains
constant, unlike a gas engine.

As for safety, most motorglider pilots know the engine is to be treated as a
convenience, and not an insurance policy. Like a pure glider, we should always be
within gliding reach of a safe landing place.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[[email protected]]

On Monday, April 13, 2020 at 9:00:45 PM UTC-8, 2G wrote:
> On Monday, April 13, 2020 at 9:49:26 PM UTC-7, wrote:
> > On Monday, April 13, 2020 at 9:37:18 AM UTC-7, Duster wrote:
> > > Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.
> >
> > There are 4 Electro's in the USA and about a dozen Rotax powered. I've flown a Rotax-powered one for about 10 years, but only have a few flights in an Electro. It flies like an older generation, lightly loaded 15 meter ship. Lots of fun soaring, but not for unhandicapped competition or records.
> >
> > The company's objective in designing the electric version was to have it achieve the same performance, at the same price, as the gas powered. I understand that the electric will climb slightly faster (bigger prop, IIRC), and the price probably isn't that much more than the Rotax version. I think the empty weight is similar, though the batteries consume a lot of space.
> >
> > But the run time, like all of the electrics, is the big difference. I think Pipistrel used to advertise 6,000' of climb on a charge, though that was a while back and they probably have better numbers today. (The Rotax powered version has a max fuel capacity of something like 14 gallons (with dual tanks). I have only the single tank configuration, but have never had "range anxiety" with probably over an hour of run time, should it be needed.. (Typical flight has 5-7 minutes for initial launch and another 5-10 minutes of run time if I need a relight, and I would guess that the Electros have a similar profile.))
> >
> > The solar trailer for the Electro is quite cool. You can park at an unelectrified gliderport, and the sun charges the battery array in the trailer. Then you hook-up your Taurus overnight and recharge the on-board batteries. Rinse and repeat.
> >
> > Pipistrel has a big lead over others in actual, in-the-field application and improvements vs. projected and theoretical systems. If they elected to market their systems in a higher-performance sailplane I think they would have a superior product.
>
> For VFR cross country flight the FAA requires you to have a 30 minute fuel reserve. Note that electric gliders don't even have 30 minutes of run time, let alone a reserve. All this discussion assumes running the battery totally flat - no reserve WHATSOEVER and perfect battery performance (no degradation for temperature or age). This is an unacceptable level of even token, lip-service safety. GIVE ME A BREAK!
>
> Tom

The 30 minutes is a flight planning requirement for Airplanes....Helicopters 20 minutes. For the glider category there is no such flight planning requirement.

[Duster[_2_]]

Thanks to those providing opinions/experiences with the Taurus Electro. I asked my local dealer if Pipistrel was planning on a longer wing. His reply was "The planform is a more forward sweep with a slight increase in span. it will be a 4 piece wing with the outer sections easily removable to permit hangaring in European smaller T-hangars. L/D 43:1 or slightly better. The wing will be plug and play with all current Taurus Electro G2.5 fuselages. Not sure if it will be plug and play with Taurus M fuselages.There is no estimated in service date as of yet."

[Dave Penworth]

I see that the same circular arguments and dogmatic thinking exists in the
wider world of gliding as it does in UK gliding.

On the topic of powered gliders, one side will argue that this is the way
the market is heading and that one of the benefits is faster turnaround and
fewer people required for launches.
The other side will engage in circular logic and argue that it is safer to
fly aircraft without engines as using an engine introduces the possibility
of engine failure.

My opinion:
Do as you like.
Buy a powered glider, preferably an SSDR, if that's what you want.
If your club is headed up by old-school dogmatic individuals who won't
'allow' you to fly from the site, find somewhere better.

[LOV2AV8]

I'll describe the requirements I am trying to satisfy for me with my project. I suspect this is much like many but obviously not all.
1) The glider needs to be practical for one person to assemble in a reasonable period of time without heavy lifting. This means a ship that is not more than about 100 lb heavier than it's similar non powered counterpart.
2) Self launch capability with acceptable margins. I am using a takeoff distance of 900 feet, off pavement, and climb rate of at least 400 feet per minute. Ability to fly off unpaved surface knowing takeoff distance will increase.
3) Battery capacity for a 2000 foot launch and 2500 feet reserve to save and get home or to a safe airport.
4)System must have sufficient motor cooling to allow high power settings long enough to get to a safe altitude before power reduction.
5) Practical charging. In my project the battery can be removed for charging away from the glider.
6) Existing proven airframe.
This is my "Wednesday afternoon" ship for when I have no tow pilot.
FWIW
UH

In response to UH criteria above I would like to chime in with the AMS-Flight Carat meets all of the criteria except for being electric and how happy I am with my AMS-Flight Carat. Decent performance launching in the summers out of Moriarty, Parowan and Eli. This will be my 3rd season with her and still love it. Factory is still taking orders.

[Eric Greenwell[_4_]]

LOV2AV8 wrote on 4/14/2020 1:41 PM:
> I'll describe the requirements I am trying to satisfy for me with my project. I suspect this is much like many but obviously not all.
> 1) The glider needs to be practical for one person to assemble in a reasonable period of time without heavy lifting. This means a ship that is not more than about 100 lb heavier than it's similar non powered counterpart.
> 2) Self launch capability with acceptable margins. I am using a takeoff distance of 900 feet, off pavement, and climb rate of at least 400 feet per minute. Ability to fly off unpaved surface knowing takeoff distance will increase.
> 3) Battery capacity for a 2000 foot launch and 2500 feet reserve to save and get home or to a safe airport.
> 4)System must have sufficient motor cooling to allow high power settings long enough to get to a safe altitude before power reduction.
> 5) Practical charging. In my project the battery can be removed for charging away from the glider.
> 6) Existing proven airframe.
> This is my "Wednesday afternoon" ship for when I have no tow pilot.
> FWIW
> UH
>
> In response to UH criteria above I would like to chime in with the AMS-Flight Carat meets all of the criteria except for being electric and how happy I am with my AMS-Flight Carat. Decent performance launching in the summers out of Moriarty, Parowan and Eli. This will be my 3rd season with her and still love it. Factory is still taking orders.

I've often wondered why the Carat was not more popular, as it seemed like good
compromise. What is the cost for a new one delivered to the US?


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[2G]

On Tuesday, April 14, 2020 at 10:16:57 AM UTC-7, Dan Marotta wrote:
> The pure glider never has any fuel reserve (molecules or electrons), yet
> they go cross country all of the time.Â* Are you suggesting that flying
> cross country in a pure glider is illegal?
>
> On 4/13/2020 11:00 PM, 2G wrote:
> > On Monday, April 13, 2020 at 9:49:26 PM UTC-7, wrote:
> >> On Monday, April 13, 2020 at 9:37:18 AM UTC-7, Duster wrote:
> >>> Any opinions on the Taurus Electro? Side-by-side, pylon, self-launch, trailer option for solar array charging, etc. They claim the profile of the cockpit/fuselage acts like a lifting body.
> >> There are 4 Electro's in the USA and about a dozen Rotax powered. I've flown a Rotax-powered one for about 10 years, but only have a few flights in an Electro. It flies like an older generation, lightly loaded 15 meter ship. Lots of fun soaring, but not for unhandicapped competition or records.
> >>
> >> The company's objective in designing the electric version was to have it achieve the same performance, at the same price, as the gas powered. I understand that the electric will climb slightly faster (bigger prop, IIRC), and the price probably isn't that much more than the Rotax version. I think the empty weight is similar, though the batteries consume a lot of space..
> >>
> >> But the run time, like all of the electrics, is the big difference. I think Pipistrel used to advertise 6,000' of climb on a charge, though that was a while back and they probably have better numbers today. (The Rotax powered version has a max fuel capacity of something like 14 gallons (with dual tanks). I have only the single tank configuration, but have never had "range anxiety" with probably over an hour of run time, should it be needed. (Typical flight has 5-7 minutes for initial launch and another 5-10 minutes of run time if I need a relight, and I would guess that the Electros have a similar profile.))
> >>
> >> The solar trailer for the Electro is quite cool. You can park at an unelectrified gliderport, and the sun charges the battery array in the trailer. Then you hook-up your Taurus overnight and recharge the on-board batteries. Rinse and repeat.
> >>
> >> Pipistrel has a big lead over others in actual, in-the-field application and improvements vs. projected and theoretical systems. If they elected to market their systems in a higher-performance sailplane I think they would have a superior product.
> > For VFR cross country flight the FAA requires you to have a 30 minute fuel reserve. Note that electric gliders don't even have 30 minutes of run time, let alone a reserve. All this discussion assumes running the battery totally flat - no reserve WHATSOEVER and perfect battery performance (no degradation for temperature or age). This is an unacceptable level of even token, lip-service safety. GIVE ME A BREAK!
> >
> > Tom
>
> --
> Dan, 5J

When you are flying a motorglider the FAA considers it to be a glider and fuel reserves don't apply. The point is that planning launches or retrieves w/o factoring in reserves is a bad idea. You will NEVER get the promised performance for a variety of reasons. It would be like planning a final glide using the max L/D.

Tom

[Dan Marotta]

You're right, Tom.

I recall the time we got low over an airport about 60 nm from home.
Rather than land, I started the engine and discovered that we were low
on fuel.Â* Rather than give up, I climbed straight ahead under power,
watching the glide back to the airport, until I had a certain glide
home.Â* I had enough fuel, though not enough to make me comfortable.Â* I
now won't take off with less than about 3/8 of a tank, or about 12 gallons.

On 4/14/2020 7:38 PM, 2G wrote:
> When you are flying a motorglider the FAA considers it to be a glider and fuel reserves don't apply. The point is that planning launches or retrieves w/o factoring in reserves is a bad idea. You will NEVER get the promised performance for a variety of reasons. It would be like planning a final glide using the max L/D.
>
> Tom

--
Dan, 5J

[Eric Greenwell[_4_]]

Dan Marotta wrote on 4/15/2020 2:30 PM:
> You're right, Tom.
>
> I recall the time we got low over an airport about 60 nm from home. Rather than
> land, I started the engine and discovered that we were low on fuel.* Rather than
> give up, I climbed straight ahead under power, watching the glide back to the
> airport, until I had a certain glide home.* I had enough fuel, though not enough
> to make me comfortable.* I now won't take off with less than about 3/8 of a tank,
> or about 12 gallons.
>
> On 4/14/2020 7:38 PM, 2G wrote:
>> When you are flying a motorglider the FAA considers it to be a glider and fuel
>> reserves don't apply. The point is that planning launches or retrieves w/o
>> factoring in reserves is a bad idea. You will NEVER get the promised performance
>> for a variety of reasons. It would be like planning a final glide using the max
>> L/D.
>>
>> Tom

Contest pilots often start their final glide even lower than a max L/D glide, when
they know the conditions on the way to the airport have some rising air. Uvalde is
well-known for that kind of planning. I don't think it is always necessary to
factor in reserves, either, as long as you have a safe place to land if it doesn't
work out. That seems to be what Dan did: not enough fuel to provide an adequate
reserve, but a bail-out plan if he didn't get lucky.

I do agree with your point in general, however, which applies to all glider
flying, powered or not.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[2G]

On Wednesday, April 15, 2020 at 2:30:39 PM UTC-7, Dan Marotta wrote:
> You're right, Tom.
>
> I recall the time we got low over an airport about 60 nm from home.
> Rather than land, I started the engine and discovered that we were low
> on fuel.Â* Rather than give up, I climbed straight ahead under power,
> watching the glide back to the airport, until I had a certain glide
> home.Â* I had enough fuel, though not enough to make me comfortable.Â* I
> now won't take off with less than about 3/8 of a tank, or about 12 gallons.
>
> On 4/14/2020 7:38 PM, 2G wrote:
> > When you are flying a motorglider the FAA considers it to be a glider and fuel reserves don't apply. The point is that planning launches or retrieves w/o factoring in reserves is a bad idea. You will NEVER get the promised performance for a variety of reasons. It would be like planning a final glide using the max L/D.
> >
> > Tom
>
> --
> Dan, 5J

While the FAA considers motorgliders to be gliders, engines don't give a damn: they want fuel to run. PERIOD. Launching with a near empty tank is just plain stupid.

[2G]

On Wednesday, April 15, 2020 at 4:10:28 PM UTC-7, Eric Greenwell wrote:
> Dan Marotta wrote on 4/15/2020 2:30 PM:
> > You're right, Tom.
> >
> > I recall the time we got low over an airport about 60 nm from home. Rather than
> > land, I started the engine and discovered that we were low on fuel.Â* Rather than
> > give up, I climbed straight ahead under power, watching the glide back to the
> > airport, until I had a certain glide home.Â* I had enough fuel, though not enough
> > to make me comfortable.Â* I now won't take off with less than about 3/8 of a tank,
> > or about 12 gallons.
> >
> > On 4/14/2020 7:38 PM, 2G wrote:
> >> When you are flying a motorglider the FAA considers it to be a glider and fuel
> >> reserves don't apply. The point is that planning launches or retrieves w/o
> >> factoring in reserves is a bad idea. You will NEVER get the promised performance
> >> for a variety of reasons. It would be like planning a final glide using the max
> >> L/D.
> >>
> >> Tom
>
> Contest pilots often start their final glide even lower than a max L/D glide, when
> they know the conditions on the way to the airport have some rising air. Uvalde is
> well-known for that kind of planning. I don't think it is always necessary to
> factor in reserves, either, as long as you have a safe place to land if it doesn't
> work out. That seems to be what Dan did: not enough fuel to provide an adequate
> reserve, but a bail-out plan if he didn't get lucky.
>
> I do agree with your point in general, however, which applies to all glider
> flying, powered or not.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

I don't worry about what "contest" pilots do - they are trying to win a contest. I would NEVER plan a glide at best L/D where the consequences are a crash - and neither should you or anybody else.

[Eric Greenwell[_4_]]

2G wrote on 4/15/2020 11:48 PM:
> On Wednesday, April 15, 2020 at 4:10:28 PM UTC-7, Eric Greenwell wrote:
>> Dan Marotta wrote on 4/15/2020 2:30 PM:
>>> You're right, Tom.
>>>
>>> I recall the time we got low over an airport about 60 nm from home. Rather than
>>> land, I started the engine and discovered that we were low on fuel.* Rather than
>>> give up, I climbed straight ahead under power, watching the glide back to the
>>> airport, until I had a certain glide home.* I had enough fuel, though not enough
>>> to make me comfortable.* I now won't take off with less than about 3/8 of a tank,
>>> or about 12 gallons.
>>>
>>> On 4/14/2020 7:38 PM, 2G wrote:
>>>> When you are flying a motorglider the FAA considers it to be a glider and fuel
>>>> reserves don't apply. The point is that planning launches or retrieves w/o
>>>> factoring in reserves is a bad idea. You will NEVER get the promised performance
>>>> for a variety of reasons. It would be like planning a final glide using the max
>>>> L/D.
>>>>
>>>> Tom
>>
>> Contest pilots often start their final glide even lower than a max L/D glide, when
>> they know the conditions on the way to the airport have some rising air. Uvalde is
>> well-known for that kind of planning. I don't think it is always necessary to
>> factor in reserves, either, as long as you have a safe place to land if it doesn't
>> work out. That seems to be what Dan did: not enough fuel to provide an adequate
>> reserve, but a bail-out plan if he didn't get lucky.
>>
>> I do agree with your point in general, however, which applies to all glider
>> flying, powered or not.

>
> I don't worry about what "contest" pilots do - they are trying to win a contest. I would NEVER plan a glide at best L/D where the consequences are a crash - and neither should you or anybody else.

Those contest pilots at Uvalde do exactly what you recommend. My point is your
"reserves" do not have to be fuel in the tank or watt hours in the battery - those
are conveniences. What matters is keeping a safe place to land within "easy"
reach. That's what I do, and that's what I've recommended for decades. It's even
documented in my "A Guide to Self-Launching Sailplane Operation" :^)


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[2G]

On Thursday, April 16, 2020 at 5:51:04 AM UTC-7, Eric Greenwell wrote:
> 2G wrote on 4/15/2020 11:48 PM:
> > On Wednesday, April 15, 2020 at 4:10:28 PM UTC-7, Eric Greenwell wrote:
> >> Dan Marotta wrote on 4/15/2020 2:30 PM:
> >>> You're right, Tom.
> >>>
> >>> I recall the time we got low over an airport about 60 nm from home. Rather than
> >>> land, I started the engine and discovered that we were low on fuel.Â* Rather than
> >>> give up, I climbed straight ahead under power, watching the glide back to the
> >>> airport, until I had a certain glide home.Â* I had enough fuel, though not enough
> >>> to make me comfortable.Â* I now won't take off with less than about 3/8 of a tank,
> >>> or about 12 gallons.
> >>>
> >>> On 4/14/2020 7:38 PM, 2G wrote:
> >>>> When you are flying a motorglider the FAA considers it to be a glider and fuel
> >>>> reserves don't apply. The point is that planning launches or retrieves w/o
> >>>> factoring in reserves is a bad idea. You will NEVER get the promised performance
> >>>> for a variety of reasons. It would be like planning a final glide using the max
> >>>> L/D.
> >>>>
> >>>> Tom
> >>
> >> Contest pilots often start their final glide even lower than a max L/D glide, when
> >> they know the conditions on the way to the airport have some rising air. Uvalde is
> >> well-known for that kind of planning. I don't think it is always necessary to
> >> factor in reserves, either, as long as you have a safe place to land if it doesn't
> >> work out. That seems to be what Dan did: not enough fuel to provide an adequate
> >> reserve, but a bail-out plan if he didn't get lucky.
> >>
> >> I do agree with your point in general, however, which applies to all glider
> >> flying, powered or not.
>
> >
> > I don't worry about what "contest" pilots do - they are trying to win a contest. I would NEVER plan a glide at best L/D where the consequences are a crash - and neither should you or anybody else.
>
> Those contest pilots at Uvalde do exactly what you recommend. My point is your
> "reserves" do not have to be fuel in the tank or watt hours in the battery - those
> are conveniences. What matters is keeping a safe place to land within "easy"
> reach. That's what I do, and that's what I've recommended for decades. It's even
> documented in my "A Guide to Self-Launching Sailplane Operation" :^)
>
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

Even if you have a safe place to land, most of us use, or our glide computers use via a high McCready setting, a conservative glide angle. This works and we know it works (most of the time). This is a basic element of flying gliders safely. Peter Masak died when he violated this basic principal and went down in unlandable territory. It seems like you are taking the opposite side of this very basic principal to somehow justify eking out the last drop of electrical performance from electric self-launchers. I am cautioning against this because it is, basically, bad policy that will, ultimately, end badly.

Tom

[[email protected]]

Old aviation quote:

"The only time you have too much fuel is when you are on fire."

[Eric Greenwell[_4_]]

2G wrote on 4/16/2020 7:18 PM:
> On Thursday, April 16, 2020 at 5:51:04 AM UTC-7, Eric Greenwell wrote:
>> 2G wrote on 4/15/2020 11:48 PM:
>>> On Wednesday, April 15, 2020 at 4:10:28 PM UTC-7, Eric Greenwell wrote:
>>>> Dan Marotta wrote on 4/15/2020 2:30 PM:
>>>>> You're right, Tom.
>>>>>
>>>>> I recall the time we got low over an airport about 60 nm from home. Rather than
>>>>> land, I started the engine and discovered that we were low on fuel.* Rather than
>>>>> give up, I climbed straight ahead under power, watching the glide back to the
>>>>> airport, until I had a certain glide home.* I had enough fuel, though not enough
>>>>> to make me comfortable.* I now won't take off with less than about 3/8 of a tank,
>>>>> or about 12 gallons.
>>>>>
>>>>> On 4/14/2020 7:38 PM, 2G wrote:
>>>>>> When you are flying a motorglider the FAA considers it to be a glider and fuel
>>>>>> reserves don't apply. The point is that planning launches or retrieves w/o
>>>>>> factoring in reserves is a bad idea. You will NEVER get the promised performance
>>>>>> for a variety of reasons. It would be like planning a final glide using the max
>>>>>> L/D.
>>>>>>
>>>>>> Tom
>>>>
>>>> Contest pilots often start their final glide even lower than a max L/D glide, when
>>>> they know the conditions on the way to the airport have some rising air. Uvalde is
>>>> well-known for that kind of planning. I don't think it is always necessary to
>>>> factor in reserves, either, as long as you have a safe place to land if it doesn't
>>>> work out. That seems to be what Dan did: not enough fuel to provide an adequate
>>>> reserve, but a bail-out plan if he didn't get lucky.
>>>>
>>>> I do agree with your point in general, however, which applies to all glider
>>>> flying, powered or not.
>>
>>>
>>> I don't worry about what "contest" pilots do - they are trying to win a contest. I would NEVER plan a glide at best L/D where the consequences are a crash - and neither should you or anybody else.
>>
>> Those contest pilots at Uvalde do exactly what you recommend. My point is your
>> "reserves" do not have to be fuel in the tank or watt hours in the battery - those
>> are conveniences. What matters is keeping a safe place to land within "easy"
>> reach. That's what I do, and that's what I've recommended for decades. It's even
>> documented in my "A Guide to Self-Launching Sailplane Operation" :^)
>
> Even if you have a safe place to land, most of us use, or our glide computers use via a high McCready setting, a conservative glide angle. This works and we know it works (most of the time). This is a basic element of flying gliders safely. Peter Masak died when he violated this basic principal and went down in unlandable territory. It seems like you are taking the opposite side of this very basic principal to somehow justify eking out the last drop of electrical performance from electric self-launchers. I am cautioning against this because it is, basically, bad policy that will, ultimately, end badly.
>
Look at my paragraph above yours, where I say "...as long as you have a safe place
to land if it doesn't if it work out". Aren't we advocating the same thing?

This discussion about the performance of electric gliders was based mostly on the
manufacturers numbers. NOBODY suggested these numbers can be trusted to be so
accurate you can discard the normal glider pilot cautions about the uncertainties
in what we do. Still, they are accurate enough to make useful comparisons for the
purposes of the discussion. Case in point: You said none of the electric gliders
could run for more than 30 minutes, and I responded with examples of electric
gliders that clearly can exceed that. That's just factual disagreement, not a
recommendation you fly the glider until the motor stops.

Please Read my "A Guide to Self-Launching Sailplane Operation" (link below) for a
better understanding of what I think are good practices for being safe in a
motorglider.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[2G]

On Thursday, April 16, 2020 at 8:20:37 PM UTC-7, Eric Greenwell wrote:
> 2G wrote on 4/16/2020 7:18 PM:
> > On Thursday, April 16, 2020 at 5:51:04 AM UTC-7, Eric Greenwell wrote:
> >> 2G wrote on 4/15/2020 11:48 PM:
> >>> On Wednesday, April 15, 2020 at 4:10:28 PM UTC-7, Eric Greenwell wrote:
> >>>> Dan Marotta wrote on 4/15/2020 2:30 PM:
> >>>>> You're right, Tom.
> >>>>>
> >>>>> I recall the time we got low over an airport about 60 nm from home. Rather than
> >>>>> land, I started the engine and discovered that we were low on fuel.Â* Rather than
> >>>>> give up, I climbed straight ahead under power, watching the glide back to the
> >>>>> airport, until I had a certain glide home.Â* I had enough fuel, though not enough
> >>>>> to make me comfortable.Â* I now won't take off with less than about 3/8 of a tank,
> >>>>> or about 12 gallons.
> >>>>>
> >>>>> On 4/14/2020 7:38 PM, 2G wrote:
> >>>>>> When you are flying a motorglider the FAA considers it to be a glider and fuel
> >>>>>> reserves don't apply. The point is that planning launches or retrieves w/o
> >>>>>> factoring in reserves is a bad idea. You will NEVER get the promised performance
> >>>>>> for a variety of reasons. It would be like planning a final glide using the max
> >>>>>> L/D.
> >>>>>>
> >>>>>> Tom
> >>>>
> >>>> Contest pilots often start their final glide even lower than a max L/D glide, when
> >>>> they know the conditions on the way to the airport have some rising air. Uvalde is
> >>>> well-known for that kind of planning. I don't think it is always necessary to
> >>>> factor in reserves, either, as long as you have a safe place to land if it doesn't
> >>>> work out. That seems to be what Dan did: not enough fuel to provide an adequate
> >>>> reserve, but a bail-out plan if he didn't get lucky.
> >>>>
> >>>> I do agree with your point in general, however, which applies to all glider
> >>>> flying, powered or not.
> >>
> >>>
> >>> I don't worry about what "contest" pilots do - they are trying to win a contest. I would NEVER plan a glide at best L/D where the consequences are a crash - and neither should you or anybody else.
> >>
> >> Those contest pilots at Uvalde do exactly what you recommend. My point is your
> >> "reserves" do not have to be fuel in the tank or watt hours in the battery - those
> >> are conveniences. What matters is keeping a safe place to land within "easy"
> >> reach. That's what I do, and that's what I've recommended for decades. It's even
> >> documented in my "A Guide to Self-Launching Sailplane Operation" :^)
> >
> > Even if you have a safe place to land, most of us use, or our glide computers use via a high McCready setting, a conservative glide angle. This works and we know it works (most of the time). This is a basic element of flying gliders safely. Peter Masak died when he violated this basic principal and went down in unlandable territory. It seems like you are taking the opposite side of this very basic principal to somehow justify eking out the last drop of electrical performance from electric self-launchers. I am cautioning against this because it is, basically, bad policy that will, ultimately, end badly.
> >
> Look at my paragraph above yours, where I say "...as long as you have a safe place
> to land if it doesn't if it work out". Aren't we advocating the same thing?
>
> This discussion about the performance of electric gliders was based mostly on the
> manufacturers numbers. NOBODY suggested these numbers can be trusted to be so
> accurate you can discard the normal glider pilot cautions about the uncertainties
> in what we do. Still, they are accurate enough to make useful comparisons for the
> purposes of the discussion. Case in point: You said none of the electric gliders
> could run for more than 30 minutes, and I responded with examples of electric
> gliders that clearly can exceed that. That's just factual disagreement, not a
> recommendation you fly the glider until the motor stops.
>
> Please Read my "A Guide to Self-Launching Sailplane Operation" (link below) for a
> better understanding of what I think are good practices for being safe in a
> motorglider.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1

The 30 minutes was at full power, not a low power cruise setting.

Tom

[Eric Greenwell[_4_]]

2G wrote on 4/16/2020 8:34 PM:
> On Thursday, April 16, 2020 at 8:20:37 PM UTC-7, Eric Greenwell wrote:

>> This discussion about the performance of electric gliders was based mostly on the
>> manufacturers numbers. NOBODY suggested these numbers can be trusted to be so
>> accurate you can discard the normal glider pilot cautions about the uncertainties
>> in what we do. Still, they are accurate enough to make useful comparisons for the
>> purposes of the discussion. Case in point: You said none of the electric gliders
>> could run for more than 30 minutes, and I responded with examples of electric
>> gliders that clearly can exceed that. That's just factual disagreement, not a
>> recommendation you fly the glider until the motor stops.
>>
>> Please Read my "A Guide to Self-Launching Sailplane Operation" (link below) for a
>> better understanding of what I think are good practices for being safe in a
>> motorglider.

>
> The 30 minutes was at full power, not a low power cruise setting.

Your original reference was to 30 minute VFR fuel reserves, which are at cruise
power, not full power, so I assumed your 30 minute remark about electric gliders
duration was also about cruising.

Practically speaking, full power duration is not a useful number when talking
about motorgliders; instead, it's climb rate for the launch, and range using the
motor, that are the important numbers. You and I are accustomed to using the "saw
tooth" method for achieving maximum range in our gas powered gliders, but for FES
gliders (and I thin also for the GP15), steady cruising is the way to achieve
maximum range.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Eric Greenwell[_4_]]

wrote on 4/16/2020 8:07 PM:
> Old aviation quote:
>
> "The only time you have too much fuel is when you are on fire."

Us Pedantics would argue even with that!

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[Jonathan St. Cloud]

On Wednesday, April 15, 2020 at 11:48:48 PM UTC-7, 2G wrote:
> On Wednesday, April 15, 2020 at 4:10:28 PM UTC-7, Eric Greenwell wrote:
> > Dan Marotta wrote on 4/15/2020 2:30 PM:
> > > You're right, Tom.
> > >
> > > I recall the time we got low over an airport about 60 nm from home. Rather than
> > > land, I started the engine and discovered that we were low on fuel.Â* Rather than
> > > give up, I climbed straight ahead under power, watching the glide back to the
> > > airport, until I had a certain glide home.Â* I had enough fuel, though not enough
> > > to make me comfortable.Â* I now won't take off with less than about 3/8 of a tank,
> > > or about 12 gallons.
> > >
> > > On 4/14/2020 7:38 PM, 2G wrote:
> > >> When you are flying a motorglider the FAA considers it to be a glider and fuel
> > >> reserves don't apply. The point is that planning launches or retrieves w/o
> > >> factoring in reserves is a bad idea. You will NEVER get the promised performance
> > >> for a variety of reasons. It would be like planning a final glide using the max
> > >> L/D.
> > >>
> > >> Tom
> >
> > Contest pilots often start their final glide even lower than a max L/D glide, when
> > they know the conditions on the way to the airport have some rising air.. Uvalde is
> > well-known for that kind of planning. I don't think it is always necessary to
> > factor in reserves, either, as long as you have a safe place to land if it doesn't
> > work out. That seems to be what Dan did: not enough fuel to provide an adequate
> > reserve, but a bail-out plan if he didn't get lucky.
> >
> > I do agree with your point in general, however, which applies to all glider
> > flying, powered or not.
> >
> > --
> > Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> > - "A Guide to Self-Launching Sailplane Operation"
> > https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>
> I don't worry about what "contest" pilots do - they are trying to win a contest. I would NEVER plan a glide at best L/D where the consequences are a crash - and neither should you or anybody else.

Difficult to state maxims about XC flying, but I would think most western flyers start their final glide before the computer says you have the numbers.. If you have been flying though lift the entire day, why wouldn't you take into consideration the amount of lift you are likely to hit on the way home. Now if the air is getting still and the day dying, one should not plan on finding additional lift. There is rarely a right answer in xc soaring, but there can definitely be a wrong answer.

[[email protected]]

most of the time I fly on final the day is dying, so making sure I have it nailed is a requirment 😂😂

[Ramy[_2_]]

Overall, the FES sounds like a very good option to me.
However someone mentioned the real possibility of prop strike. If this happen, I still want to be able to fly my glider as a pure glider until I get the new prop, but if I need to send the motor for repair, or worse, send my ship to Europe to repair the motor, then this could be a deal breaker. Anyone knows more about the consequences (and cost) of prop strike?

Ramy

[Eric Greenwell[_4_]]

Ramy wrote on 4/17/2020 11:40 PM:
> Overall, the FES sounds like a very good option to me.
> However someone mentioned the real possibility of prop strike. If this happen, I still want to be able to fly my glider as a pure glider until I get the new prop, but if I need to send the motor for repair, or worse, send my ship to Europe to repair the motor, then this could be a deal breaker. Anyone knows more about the consequences (and cost) of prop strike?
> According to the FES site, an FES glider can be easily returned to the "pure
glider" configuration. The motor and propeller are removed and a nose cone is
attached; the batteries can be removed the usual way. I suspect the weight and
balance would still be correct, too.

I have no idea what the cost of the prop strike would be, but I recall reading
about one, and the motor was undamaged. The motor is simple and easily examined,
unlike a gasoline motor.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1

[[email protected]]

I know of a Silent 2 FES that had a prop strike on takeoff. Took an inch or 2 off both props. Pilot continued the launch. Said from his perspective he suspected a strike but the glider seemed to power and fly okay. Motor was fine; don’t even think it required an inspection. Got new props. I’ve watched a FES prop balancing exercise. Looked like it required special equipment and was rather tedious. Anyone have information on that process?

Danny Brotto
LS-8/18 "P6"

[[email protected]]

ship to Europe to repair the motor, then this could be a deal breaker. Anyone knows more about the consequences (and cost) of prop strike?
>
> Ramy

I know Paul Gains in Arizona has repaired or still repairing a FES set up glider from what I think was a prop strike.

Kevin
92

[Jonathan St. Cloud]

On Friday, April 17, 2020 at 7:11:52 PM UTC-7, wrote:
> most of the time I fly on final the day is dying, so making sure I have it nailed is a requirment 😂😂

Dying means it is still alive. I come home many times while there is still lift. Perhaps I flew the task I had declared pre-flight, perhaps I am old enough to want to disassemble by daylight and drink a beer will my fellow pilots. I remember one special flight of about 10 km short of a 1000K. The last thermal was soft, not turbulent, unlike the others of that day and wide. Rode that thermal to 17,0000 feet and the day just shut off, not another bump. Ended up over an airport at 5000 AGL and pulled spoilers as the day had died about 45 minutes ago. One of the reasons this day was so remarkable, was because the day died so sudden and complete.
I don't just let the computer think for me. If I do that I feel disconnected to the flight. If the day is not dead and you have practice at estimating the amount of lift based on the day the sky and flarm of other pilots why wouldn't you take into account the lift you are likely to encounter on the way home.

This past summer I spent about 25 hours with a new xc pilot in his dou-d. I had him estimate every glide arrival even just to the next cloud. He got pretty good at estimating the lift we encountered between glides. On longer days when he started to be wrong on the callouts (300 feet) he knew the day had changed.
same in sailing, just practice until you know your boat/bird and the air.

[Alex Lamb]

Magnus,

What did you decide about electric self launch?

--- Alex (Willamette Valley Soaring Club)

[Matthew Scutter]

On Wednesday, January 20, 2021 at 3:10:40 PM UTC+10, Alex Lamb wrote:
> Magnus,
>
> What did you decide about electric self launch?
>
> --- Alex (Willamette Valley Soaring Club)

I don't know what Magnus ordered, but my aforementioned Diana 2NG-FES arrived about a month after my post, and you can see the results:
https://www.youtube.com/watch?v=3clSlZUPI3w

I will make some better videos in the coming months.

[Magnus]

Alex,
Thanks for remembering me. I have not yet decided as COVID-19 has delayed the certification and launch of both the GP Jeta and LAK-17C gliders in Europe. The advice from the original thread was to wait for some practical experience in the field and I look forward to that. The battery development is also moving fast so while waiting the capacity is improving and cost is going down. Still have my eyes open for alternatives
Magnus

On Wednesday, January 20, 2021 at 6:10:40 AM UTC+1, Alex Lamb wrote:
> Magnus,
>
> What did you decide about electric self launch?
>
> --- Alex (Willamette Valley Soaring Club)