Best option for electric self starting glider

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

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

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).

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...

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".

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?

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?

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/motorg...ad-the-guide-1

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.

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.