Bonus Jet glider demo weekend

On Apr 24, 9:43*pm, Darryl Ramm wrote:

What does the take-off ground roll or 50' numbers look like?

Thanks

Darryl

There are some ground roll claims on the website but I didn't see any
50 ft numbers. I only had pressure altitude recording so no distance
data for my flight.

See http://www.desertaerospace.com/faq/faq_bonusjet.html

Andy

On Apr 25, 2:21*am, gotovkotzepkoi gotovkotzepkoi.
wrote:
This is indeed impressive. But while it may be cool to have a jet engine
it's becoming clear that electric self launch is the future. The jet
option is too noisy, uses too much fuel and you still have to fly around
with a bomb at your back.

--
gotovkotzepkoi

It's not that black and white. Electrics make sense if viewed as
simply self-launch but jets offer higher XC speeds to "self-retrieve"
from 120 NM away in less than an hour in addition to self-launch.

On 4/25/2011 7:26 AM, bildan wrote:
On Apr 25, 2:21 am, gotovkotzepkoigotovkotzepkoi.
wrote:
This is indeed impressive. But while it may be cool to have a jet engine
it's becoming clear that electric self launch is the future. The jet
option is too noisy, uses too much fuel and you still have to fly around
with a bomb at your back.

--
gotovkotzepkoi

It's not that black and white. Electrics make sense if viewed as
simply self-launch but jets offer higher XC speeds to "self-retrieve"
from 120 NM away in less than an hour in addition to self-launch.

The high speed could be a game changer for someone doing wave flying.
The best wave is 90 NM upwind of me, completely impractical to reach at
the 70 knot cruising speed of my ASH 26 E against a 30-40 knot headwind
- 2 1/2 hours and out of fuel to get there. A 120 knot cruise (or 150
knot like the DuckHawk could provide), would take less than an hour.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz

Thanks to everyone in ASA and at Turf Soaring in Phoenix for a
wonderful weekend. Driving back to Albuquerque Sunday I was wishing
I'd just made the attempt by air. The cloud streets looked awesome
and I'd have had a hell of a tailwind!

Also, thanks to the Sylacauga Soaring Society (Birmingham, AL) for
hosting us the previous weekend. It was also a great weekend with
great folks and awesome soaring conditions - after the Friday night
tornadoes, that is ;o)

We're hoping to do some more demo weekends later this summer.

Here's the stats for the ASA weekend: We gave 14 rides, used 3.15
gallons jet-A per launch (fuel cost per launch $11.34 in Alabama,
$19.50 in Phoenix), 9 minutes engine run per launch, averaged just
over 1000 ft/min initial climb (two full sized guys and 6 - 15 gallons
fuel, density altitude about 3700' MSL). We successfully thermalled up
on every flight. The engine was usually reduced to idle by about
1500' AGL and shut down by 2500' AGL.

To answer a few of the questions and comments:

Single control - The factory-supplied throttle quadrant does have a
single lever start/throttle with a detent like Andy suggested. With
the dual cockpit, we chose to place the throttle unit between the
cockpits (with mechanical linkage to both seats) and place a start/
stop switch on the panel, as it would be difficult to design a
mechanical method for actuating the detent from either cockpit.
Integrating the pylon and throttle would be possible, just more
expensive. Lots of cost and effort to eliminate one momentary switch.

Takeoff roll - The takeoff rolls at Turf were probably extended a bit
because of the rough runway surface (we were using 23R) and (I think)
a slight uphill grade. Most launches began in the soft gravel
adjacent to the runway. At Moriarty, we've measured the takeoff roll
at around 700'. I was also going easy on the initial throttle-up. If
runway length was an issue, one could hold the brakes until the engine
spooled up to full power.

Noise - Yes, it is noisy when you're nearby, especially aft of the
engine. Once airborne, the noise diminished quickly. I've posted
comparative takeoff noise values on the website. Slightly worse than
a Pawnee, better than a Citation or Rotax powered gyrocopter. Noise
in the cockpit is comparable to other motorgliders, and less than most
airplanes. We flew with an EW logger on one flight. I'll check the
cockpit ENL reading.

Jet vs. electric - Either is, IMHO, better (and safer) than the 2
stroke lawn mower engines used by most current motorgliders. Yes, the
jet is noisier and uses about the same fuel as a towplane launch, but
it gives you the option of traveling at high speed for many miles, as
well as the option of refueling at another airport. Like electric,
the jet eliminates vibration, thus increasing reliability. As for the
unwarranted 'bomb at your back' comment, I'd ask that you check
statistics on fires caused by electrical failures before jumping to
the conclusion about comparative safety. Electric self launch systems
are capable of producing thousands of amps. Also, ask the R/C guys
about battery fires (high power density batteries are getting better,
but still a concern). I don't see electric and jets as mutually
exclusive. Both have merit in different situations. I applaud any
effort to make something more reliable than the existing motorglider
technology.

Fuel capacity - solo - 24 gallons, good for almost two hours at 80
knot cruise (faster if higher). With two normal guys, fuel capacity
is reduced to about 15 gallons.

Blue skies,

Bob Carlton
Desert Aerospace, LLC
www.desertaerospace.com



On Apr 25, 8:26*am, bildan wrote:
On Apr 25, 2:21*am, gotovkotzepkoi gotovkotzepkoi.

wrote:
This is indeed impressive. But while it may be cool to have a jet engine
it's becoming clear that electric self launch is the future. The jet
option is too noisy, uses too much fuel and you still have to fly around
with a bomb at your back.

--
gotovkotzepkoi

It's not that black and white. *Electrics make sense if viewed as
simply self-launch but jets offer higher XC speeds to "self-retrieve"
from 120 NM away in less than an hour in addition to self-launch.

On Apr 25, 7:26*am, bildan wrote:
On Apr 25, 2:21*am, gotovkotzepkoi gotovkotzepkoi.

wrote:
This is indeed impressive. But while it may be cool to have a jet engine
it's becoming clear that electric self launch is the future. The jet
option is too noisy, uses too much fuel and you still have to fly around
with a bomb at your back.

--
gotovkotzepkoi

It's not that black and white. *Electrics make sense if viewed as
simply self-launch but jets offer higher XC speeds to "self-retrieve"
from 120 NM away in less than an hour in addition to self-launch.

Jets (as long as they have the endurance) also offer much more
impressive capability to self-deploy. We've had some cases of SF Bay
Area motorglider pilots crossing the central valley to to go soaring
in the Sierras or on the Whites. But its a challenge given the slow XC
performance and poor high-altitude operation of typical motorgliders
(even many touring ones). Electric self launcher are a non-starter for
these type missions. Or the long self retrieve mentioned already - and
you are constantly fighting battery weight vs. capacity limits.

The issue with the jets I see is the operational issue of noise and
jet blast in many glider operations - OTOH operating any motorglider
at many typical gliderports already has some of these issues.

Darryl

On 4/25/2011 9:55 AM, Darryl Ramm wrote:
On Apr 25, 7:26 am, wrote:
On Apr 25, 2:21 am, gotovkotzepkoigotovkotzepkoi.

wrote:
This is indeed impressive. But while it may be cool to have a jet engine
it's becoming clear that electric self launch is the future. The jet
option is too noisy, uses too much fuel and you still have to fly around
with a bomb at your back.

--
gotovkotzepkoi

It's not that black and white. Electrics make sense if viewed as
simply self-launch but jets offer higher XC speeds to "self-retrieve"
from 120 NM away in less than an hour in addition to self-launch.

Jets (as long as they have the endurance) also offer much more
impressive capability to self-deploy. We've had some cases of SF Bay
Area motorglider pilots crossing the central valley to to go soaring
in the Sierras or on the Whites. But its a challenge given the slow XC
performance and poor high-altitude operation of typical motorgliders
(even many touring ones). Electric self launcher are a non-starter for
these type missions. Or the long self retrieve mentioned already - and
you are constantly fighting battery weight vs. capacity limits.

The issue with the jets I see is the operational issue of noise and
jet blast in many glider operations - OTOH operating any motorglider
at many typical gliderports already has some of these issues.

Darryl


If a towplane (or winch) is available, you could take a pattern tow,
then start the engine.

You need to carry a lot of fuel to go very far, though. That probably
means fuel in the wings. I don't know what you do if there still is
fuel in the wings when you disassemble the glider. Just leave it in the
wings?

On Apr 25, 10:13*am, Greg Arnold wrote:
On 4/25/2011 9:55 AM, Darryl Ramm wrote:









On Apr 25, 7:26 am, *wrote:
On Apr 25, 2:21 am, gotovkotzepkoigotovkotzepkoi.

*wrote:
This is indeed impressive. But while it may be cool to have a jet engine
it's becoming clear that electric self launch is the future. The jet
option is too noisy, uses too much fuel and you still have to fly around
with a bomb at your back.

--
gotovkotzepkoi

It's not that black and white. *Electrics make sense if viewed as
simply self-launch but jets offer higher XC speeds to "self-retrieve"
from 120 NM away in less than an hour in addition to self-launch.

Jets (as long as they have the endurance) also offer much more
impressive capability to self-deploy. We've had some cases of SF Bay
Area motorglider pilots crossing the central valley to to go soaring
in the Sierras or on the Whites. But its a challenge given the slow XC
performance and poor high-altitude operation of typical motorgliders
(even many touring ones). Electric self launcher are a non-starter for
these type missions. Or the long self retrieve mentioned already - and
you are constantly fighting battery weight vs. capacity limits.

The issue with the jets I see is the operational issue of noise and
jet blast in many glider operations - OTOH operating any motorglider
at many typical gliderports already has some of these issues.

Darryl

If a towplane (or winch) is available, you could take a pattern tow,
then start the engine.

You need to carry a lot of fuel to go very far, though. *That probably
means fuel in the wings. *I don't know what you do if there still is
fuel in the wings when you disassemble the glider. *Just leave it in the
wings?

Roger that, when some glider ports get really busy its easier and less
disruptive to operations even with my ASH-26E to take a tow than self-
launch - even if that means getting off tow and continuing under
engine power for a long self-launch.

Don't know for the jet, but most fuel bags in the wing motorgliders
are not designed to hold fuel in the bags when the wings are removed -
you need to drain the fuel before derigging.

Darryl

Fuel is in the wings and should be drained before derigging. The
BonusJet has overwing fuel caps, so draining is easy with a small pump
or siphon. I would think draining fuel would be a good idea before
trailering, even if the fuel was in the fuselage.

BC

On Apr 25, 11:24*am, Darryl Ramm wrote:
On Apr 25, 10:13*am, Greg Arnold wrote:



On 4/25/2011 9:55 AM, Darryl Ramm wrote:

On Apr 25, 7:26 am, *wrote:
On Apr 25, 2:21 am, gotovkotzepkoigotovkotzepkoi.

*wrote:
This is indeed impressive. But while it may be cool to have a jet engine
it's becoming clear that electric self launch is the future. The jet
option is too noisy, uses too much fuel and you still have to fly around
with a bomb at your back.

--
gotovkotzepkoi

It's not that black and white. *Electrics make sense if viewed as
simply self-launch but jets offer higher XC speeds to "self-retrieve"
from 120 NM away in less than an hour in addition to self-launch.

Jets (as long as they have the endurance) also offer much more
impressive capability to self-deploy. We've had some cases of SF Bay
Area motorglider pilots crossing the central valley to to go soaring
in the Sierras or on the Whites. But its a challenge given the slow XC
performance and poor high-altitude operation of typical motorgliders
(even many touring ones). Electric self launcher are a non-starter for
these type missions. Or the long self retrieve mentioned already - and
you are constantly fighting battery weight vs. capacity limits.

The issue with the jets I see is the operational issue of noise and
jet blast in many glider operations - OTOH operating any motorglider
at many typical gliderports already has some of these issues.

Darryl

If a towplane (or winch) is available, you could take a pattern tow,
then start the engine.

You need to carry a lot of fuel to go very far, though. *That probably
means fuel in the wings. *I don't know what you do if there still is
fuel in the wings when you disassemble the glider. *Just leave it in the
wings?

Roger that, when some glider ports get really busy its easier and less
disruptive to operations even with my ASH-26E to take a tow than self-
launch - even if that means getting off tow and continuing under
engine power for a long self-launch.

Don't know for the jet, but most fuel bags in the wing motorgliders
are not designed to hold fuel in the bags when the wings are removed -
you need to drain the fuel before derigging.

Darryl

On Apr 25, 8:21*pm, gotovkotzepkoi gotovkotzepkoi.
wrote:
This is indeed impressive. But while it may be cool to have a jet engine
it's becoming clear that electric self launch is the future. The jet
option is too noisy, uses too much fuel and you still have to fly around
with a bomb at your back.

*Anything* that stores large amounts of energy and can release it
quickly is a potential bomb.

At the moment I'd say we know more about stopping kerosine from
inadvertently catching fire or exploding than we know about stopping
Lithium batteries doing the same.

(and kerosine is noticeably better than petrol in that regard too)

On 4/25/2011 6:06 PM, Bruce Hoult wrote:
On Apr 25, 8:21 pm, gotovkotzepkoigotovkotzepkoi.
wrote:
This is indeed impressive. But while it may be cool to have a jet engine
it's becoming clear that electric self launch is the future. The jet
option is too noisy, uses too much fuel and you still have to fly around
with a bomb at your back.

*Anything* that stores large amounts of energy and can release it
quickly is a potential bomb.

At the moment I'd say we know more about stopping kerosine from
inadvertently catching fire or exploding than we know about stopping
Lithium batteries doing the same.

He might have been talking about the engine flying apart if an impeller
wheel fails. A shield to protect the fuselage might be useful; possibly,
the engine is built to contain a failed impeller.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl