On Tuesday, August 18, 2020 at 4:01:47 PM UTC-7, kinsell wrote:
On 8/18/20 4:07 PM, 2G wrote:
On Tuesday, August 18, 2020 at 1:49:35 PM UTC-7, andy l wrote:
On Tuesday, 18 August 2020 at 16:41:21 UTC+1, jld wrote:
You probably have reasons to be skeptical but, they should only "expect" until the validation (ground/flight tests) are performed and don't force design changes.
If they updated their configuration this year, it makes sense for the validation tests to happen in Q1 next year.
Because this is not a complete redesign, they should be confident enough to pass validation tests and take the risk to start production using new configuration right now. Therefore I am not surprised to hear they are updating already produced gliders and produce new ones with latest configuration.
"wasn't design driven, but regulatory driven, meaning it can't be relied upon"
I don't get your point, the same situation would be true for anybody designing under FAA/EASA or UL. Until you apply for TC, if authorities changes the rules, you have to adjust.
The UL regulation changes in EU took a long time to get delivered and I am confident it is going to be stable for quite a bit of time.
GP did their best to come up with design targets and now they adjust them to fit most authorities requirements.

Concerning the MTM, if the structure is not the limiting factor, GP will eventually have to adjust it to pass the Vso requirement for UL in EU (i.e. 45 Kts for Germany and 38 Kts in France).
If structure is capable, US experimental could use a higher MTM but, who want to fly above 60 kg/m2 anyway?
Adding together some of the recent comments, it sounds like this glider might be stronger and lighter than others, and possibly faster as well

Does it use different materials?

And what are all the changes? You can't easily modify already existing gliders for a much higher all up weight, just by writing it down somewhere; it needs to be stronger, for instance thicker spar caps

They claim to use different materials that make GP gliders lighter and stronger than the competition:

"We use the most advanced composites and construction methods that allow for the exceptional strength requirements of the design. They also contribute to the quality and reliability of the structure. This allows gliders of far lower weight to be as strong as gliders produced using conventional methods."

GP doesn't just claim "lower weight," but "far lower weight" than other gliders, but w/o any evidence to support this claim. The only real evidence I have seen is that Sebastian Kawa was very unhappy with the glider GP delivered to him and switched gliders at the last minute. Kawa also had a propulsion failure while flying a GP-14 in Italy, yet GP gliders makes this bizarre claim on their website:

"The motor can be deployed and running at full power within five seconds providing confidence in the event of when a ‘low save’ is on the cards."

I guess Sebastian didn't get the memo on how reliable GP propulsion systems are. You are certainly welcome to accept all of GP's claims w/o any evidence, but I won't. And I certainly wouldn't send them six figures in cash for it.

Tom


Sebastian's disinterest in flying the Jeta in 2018 was addressed in the
November Soaring article. The wings weren't adequately cured and sagged
fore and aft of the spars. These same wings were what the U.S. dealer
test flew for the article. Putting his best spin on it, he said 51:1
remains a reasonable goal for the small fuselage version. Not exactly
the same as a Dick Johnson test report.

On the propulsion failure, Eric has claimed it was pilot error. If it's
too complicated for a world-class pilot to get right, maybe it needs to
be simplified? "Alexa, save my ass!!"

Sebastian for his part hasn't admitted to error, he made it sound like a
sensor failure indicating the boom wasn't fully up, as can happen on any
boom system. He did press on from an area with good landing options
when getting low to one with poor options, so there was a judgement
error there.

-Dave

Ok, let's blame the victim here. GP delivered a poorly constructed glider to Kawa - maybe that's Kawa's fault as well. AFAIK, no GP-15s have received airworthiness certificates in the US (or elsewhere for that matter). The point is that the very limited quality control data we have on GP Gliders is not encouraging, and their wild advertising claims are unsupported.

Tom