My September 2017 visit to GP Gliders

On Friday, August 21, 2020 at 12:24:21 AM UTC-7, jld wrote:
"regulations to allow 525 kg in a year or two"
Maybe some countries could increase MTOM (up to 600 kg) but don't forget that the glider must still demonstrate a certain Vso at that MTOM.
Given the small surface of the GP15 (7,78 m2), the low relative thickness of the airfoil (required to get to high L/D), it is going to already be excellent if they can meet the 45 Kts Vso limit at 470 Kg (which is 60 kg/m2)..
If you register outside EU and the 45 Kts Vso limit does not apply, going to higher WL/Vso means climbing at IAS above 60 kts.

You can always increase WL to improve your task speed but this is not going to help much if you start from a bad polar curve.
If they can get close to their polar and achieve 2 m/s sink rate at 200 km/h with 45 kg/m2 WL, then GP15 will be an excellent cruiser.

The $64,000 Question (yes, I am that old) is which country's certification standards, if any, is GP going to meet? They don't mention certification on their website. Also, I assume that the V-n diagram (fig. 1) are the G loads the glider must be designed for. If so, they are considerably less than what non-UL gliders must meet.

Tom

2G wrote on 8/21/2020 3:30 PM:
On Friday, August 21, 2020 at 12:24:21 AM UTC-7, jld wrote:
"regulations to allow 525 kg in a year or two"
Maybe some countries could increase MTOM (up to 600 kg) but don't forget that the glider must still demonstrate a certain Vso at that MTOM.
Given the small surface of the GP15 (7,78 m2), the low relative thickness of the airfoil (required to get to high L/D), it is going to already be excellent if they can meet the 45 Kts Vso limit at 470 Kg (which is 60 kg/m2)..
If you register outside EU and the 45 Kts Vso limit does not apply, going to higher WL/Vso means climbing at IAS above 60 kts.

You can always increase WL to improve your task speed but this is not going to help much if you start from a bad polar curve.
If they can get close to their polar and achieve 2 m/s sink rate at 200 km/h with 45 kg/m2 WL, then GP15 will be an excellent cruiser.

The $64,000 Question (yes, I am that old) is which country's certification standards, if any, is GP going to meet? They don't mention certification on their website. Also, I assume that the V-n diagram (fig. 1) are the G loads the glider must be designed for. If so, they are considerably less than what non-UL gliders must meet.

Tom

The G Limits for the GP15 are the same as your ASH 26 E - +5.3/-2.65.

--
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 Friday, August 21, 2020 at 9:11:39 PM UTC-7, Eric Greenwell wrote:
2G wrote on 8/21/2020 3:30 PM:
On Friday, August 21, 2020 at 12:24:21 AM UTC-7, jld wrote:
"regulations to allow 525 kg in a year or two"
Maybe some countries could increase MTOM (up to 600 kg) but don't forget that the glider must still demonstrate a certain Vso at that MTOM.
Given the small surface of the GP15 (7,78 m2), the low relative thickness of the airfoil (required to get to high L/D), it is going to already be excellent if they can meet the 45 Kts Vso limit at 470 Kg (which is 60 kg/m2)..
If you register outside EU and the 45 Kts Vso limit does not apply, going to higher WL/Vso means climbing at IAS above 60 kts.

You can always increase WL to improve your task speed but this is not going to help much if you start from a bad polar curve.
If they can get close to their polar and achieve 2 m/s sink rate at 200 km/h with 45 kg/m2 WL, then GP15 will be an excellent cruiser.

The $64,000 Question (yes, I am that old) is which country's certification standards, if any, is GP going to meet? They don't mention certification on their website. Also, I assume that the V-n diagram (fig. 1) are the G loads the glider must be designed for. If so, they are considerably less than what non-UL gliders must meet.

Tom

The G Limits for the GP15 are the same as your ASH 26 E - +5.3/-2.65.
--
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

That is what is posted on their website, but have destructive tests been done on an actual wing by an independent lab? And, again, I ask what country's aircraft certification standards, if any, will the GP15 meet?

Tom

"which country's certification standards, if any, is GP going to meet? "
If they want to sell in EU, the addressable market is large but they have no choice and need approval in Germany, France, Italy and a few other countries.
This is confirmed by the fact GP has initiated activities with DULV

As Eric mentioned, even if +4g is sufficient to satisfy UL rules, GP has elected to use the CS22 limits at 5,3g.
This being said, +4g is already good (I am that old too and can't pull that many g's in thermal anyway) and believe the gust load and Vb (see Vn diagram for gust load) are of more interest for gliders.
Because GP15 Vne is 162 kts, Vd is 180 kts and Vb=Va is 120 Kts.
This means you can fly up to 120 Kts, hit a strong rotor and be OK (the glider be OK I should say).

"but have destructive tests been done on an actual wing"
They will have no choice but do it to get DULV approval.

UL "certification" does not require similar destructive test (at 54C temp) as certified gliders. It is the whole idea of UL, the manufacturers can state, without independent tests, that "we think this is ok" and buyers are aware that they are getting uncertified products.

This does not mean that manufacturer don't test their aircraft at all, of course. I bet all of them do at least simple static sandbag test to max G.

"UL certification does not require similar destructive test (at 54C temp) as certified gliders"
Depends on the authorities you are dealing with.
With DULV, LTF-UL 305 (Strength and deformations) and LTF-UL 307 (Proof of strength)are pretty clear and identical to CS22.
In both cases, unless the manufacturer can justify previous experience, compliance by analysis is no possible and evidence of load tests (which must be witnessed) has to be provided.
And in both cases 54°C is considered normal temperature for all components.

2G wrote on 8/21/2020 10:28 PM:
On Friday, August 21, 2020 at 9:11:39 PM UTC-7, Eric Greenwell wrote:
2G wrote on 8/21/2020 3:30 PM:
On Friday, August 21, 2020 at 12:24:21 AM UTC-7, jld wrote:
"regulations to allow 525 kg in a year or two"
Maybe some countries could increase MTOM (up to 600 kg) but don't forget that the glider must still demonstrate a certain Vso at that MTOM.
Given the small surface of the GP15 (7,78 m2), the low relative thickness of the airfoil (required to get to high L/D), it is going to already be excellent if they can meet the 45 Kts Vso limit at 470 Kg (which is 60 kg/m2)..
If you register outside EU and the 45 Kts Vso limit does not apply, going to higher WL/Vso means climbing at IAS above 60 kts.

You can always increase WL to improve your task speed but this is not going to help much if you start from a bad polar curve.
If they can get close to their polar and achieve 2 m/s sink rate at 200 km/h with 45 kg/m2 WL, then GP15 will be an excellent cruiser.

The $64,000 Question (yes, I am that old) is which country's certification standards, if any, is GP going to meet? They don't mention certification on their website. Also, I assume that the V-n diagram (fig. 1) are the G loads the glider must be designed for. If so, they are considerably less than what non-UL gliders must meet.

Tom

The G Limits for the GP15 are the same as your ASH 26 E - +5.3/-2.65.

That is what is posted on their website, but have destructive tests been done on an actual wing by an independent lab? And, again, I ask what country's aircraft certification standards, if any, will the GP15 meet?

The Velo 14 (the 13.5M version) has been tested for flutter and to destruction. A
video is on the FB page. The factory says the GP15 will be tested in Q1-2021, and
the videos will be posted afterwards.

From the Feb 2020 Provisional Flight Manual:

1.2. Certification Basis

This Motor Glider has been approved in the SFUL LSZ category -
http://www.sful.sk/smernice in accordance with the higher tier regulations of:

LTF-UL http://www.dulv.de/sites/default/fil...amische_ul.pdf

CS-22
https://www.easa.europa.eu/certifica...red-sailplanes

Your concern for the safety of GP15 customers suggests that you might be
considering a reservation deposit to get in the order queue, just in case the GP15
works out. You would not be the first owner of a large and complicated motorglider
to do so :^)

--
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 Saturday, August 22, 2020 at 6:27:14 AM UTC-7, Eric Greenwell wrote:
2G wrote on 8/21/2020 10:28 PM:
On Friday, August 21, 2020 at 9:11:39 PM UTC-7, Eric Greenwell wrote:
2G wrote on 8/21/2020 3:30 PM:
On Friday, August 21, 2020 at 12:24:21 AM UTC-7, jld wrote:
"regulations to allow 525 kg in a year or two"
Maybe some countries could increase MTOM (up to 600 kg) but don't forget that the glider must still demonstrate a certain Vso at that MTOM.
Given the small surface of the GP15 (7,78 m2), the low relative thickness of the airfoil (required to get to high L/D), it is going to already be excellent if they can meet the 45 Kts Vso limit at 470 Kg (which is 60 kg/m2)..
If you register outside EU and the 45 Kts Vso limit does not apply, going to higher WL/Vso means climbing at IAS above 60 kts.

You can always increase WL to improve your task speed but this is not going to help much if you start from a bad polar curve.
If they can get close to their polar and achieve 2 m/s sink rate at 200 km/h with 45 kg/m2 WL, then GP15 will be an excellent cruiser.

The $64,000 Question (yes, I am that old) is which country's certification standards, if any, is GP going to meet? They don't mention certification on their website. Also, I assume that the V-n diagram (fig. 1) are the G loads the glider must be designed for. If so, they are considerably less than what non-UL gliders must meet.

Tom

The G Limits for the GP15 are the same as your ASH 26 E - +5.3/-2.65.

That is what is posted on their website, but have destructive tests been done on an actual wing by an independent lab? And, again, I ask what country's aircraft certification standards, if any, will the GP15 meet?
The Velo 14 (the 13.5M version) has been tested for flutter and to destruction. A
video is on the FB page. The factory says the GP15 will be tested in Q1-2021, and
the videos will be posted afterwards.

From the Feb 2020 Provisional Flight Manual:

1.2. Certification Basis

This Motor Glider has been approved in the SFUL LSZ category -
http://www.sful.sk/smernice in accordance with the higher tier regulations of:

LTF-UL http://www.dulv.de/sites/default/fil...amische_ul.pdf

CS-22
https://www.easa.europa.eu/certifica...red-sailplanes

Your concern for the safety of GP15 customers suggests that you might be
considering a reservation deposit to get in the order queue, just in case the GP15
works out. You would not be the first owner of a large and complicated motorglider
to do so :^)
--
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

Your CS22 link is broken.

Tom

2G wrote on 8/23/2020 4:59 PM:
On Saturday, August 22, 2020 at 6:27:14 AM UTC-7, Eric Greenwell wrote:
2G wrote on 8/21/2020 10:28 PM:
On Friday, August 21, 2020 at 9:11:39 PM UTC-7, Eric Greenwell wrote:
2G wrote on 8/21/2020 3:30 PM:
On Friday, August 21, 2020 at 12:24:21 AM UTC-7, jld wrote:
"regulations to allow 525 kg in a year or two"
Maybe some countries could increase MTOM (up to 600 kg) but don't forget that the glider must still demonstrate a certain Vso at that MTOM.
Given the small surface of the GP15 (7,78 m2), the low relative thickness of the airfoil (required to get to high L/D), it is going to already be excellent if they can meet the 45 Kts Vso limit at 470 Kg (which is 60 kg/m2)..
If you register outside EU and the 45 Kts Vso limit does not apply, going to higher WL/Vso means climbing at IAS above 60 kts.

You can always increase WL to improve your task speed but this is not going to help much if you start from a bad polar curve.
If they can get close to their polar and achieve 2 m/s sink rate at 200 km/h with 45 kg/m2 WL, then GP15 will be an excellent cruiser.

The $64,000 Question (yes, I am that old) is which country's certification standards, if any, is GP going to meet? They don't mention certification on their website. Also, I assume that the V-n diagram (fig. 1) are the G loads the glider must be designed for. If so, they are considerably less than what non-UL gliders must meet.

Tom

The G Limits for the GP15 are the same as your ASH 26 E - +5.3/-2.65.

That is what is posted on their website, but have destructive tests been done on an actual wing by an independent lab? And, again, I ask what country's aircraft certification standards, if any, will the GP15 meet?
The Velo 14 (the 13.5M version) has been tested for flutter and to destruction. A
video is on the FB page. The factory says the GP15 will be tested in Q1-2021, and
the videos will be posted afterwards.

From the Feb 2020 Provisional Flight Manual:

1.2. Certification Basis

This Motor Glider has been approved in the SFUL LSZ category -
http://www.sful.sk/smernice in accordance with the higher tier regulations of:

LTF-UL http://www.dulv.de/sites/default/fil...amische_ul.pdf

CS-22
https://www.easa.europa.eu/certifica...red-sailplanes

Your concern for the safety of GP15 customers suggests that you might be
considering a reservation deposit to get in the order queue, just in case the GP15
works out. You would not be the first owner of a large and complicated motorglider
to do so :^)
--

Your CS22 link is broken.


A dash got lost somehow when I copied it from the pdf. This one works for me:

https://www.easa.europa.eu/certifica...red-sailplanes
--
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