My September 2017 visit to GP Gliders

On Tuesday, August 18, 2020 at 10:26:51 PM UTC-4, Eric Greenwell wrote:
... The original mechanical mast switch, external to the mast, was deemed
too vulnerable to damage after Kawa's accident with the prototype glider.
It was replaced with two redundant, buried solid state switches
to prevent a repeat of the problem.

Um, you might want to review my discussion of limit switch problems he
https://www.youtube.com/watch?v=R--m0NDR0j8&t=6s

"I checked and can confirm that you are wrong"
Before telling people they are wrong, you should "check" a little bit more.
The information is not always easy to access from "Google" and you need too look for national authorities or UL organizations to get he data.
Just to use an example I already provided, France limits single seat class 3 UL to 238kg empty weight, with a 21 kg fuel lump weight and 86kg pilot lump weight. This gets to the 345 kg MOTM. They also limit Vso to 70 km/h at MTOM.
In the case of electric propulsion, DGAC (French authority) allows to transfer the 21kg of fuel lump weight into the empty weight. Therefore maximum empty weight of single seat electric powered class 3 UL with batteries is 259kg. As you can see, this is quite different from the 600kg 45 Kts you refer to.


"I suspect your motivation for telling lies post after post is that you are GP dealer?"
I am certainly intrigued and interested by the GP15 and I have done some reverse engineering to try better understand it but, I am not a GP dealer.
I don't pretend to be always correct but I feel offended when you state I am lying. I don't mind to stand corrected if you can point to specific points which you believe are not correct.

Indeed sarcasm is not useful and it was just a useless response to your statements.

I don't believe I have been smearing at anybody.
I certainly complained about poor communication from established glider manufacturers. Being lucky to be an owner, I certainly have experience in this domain.

I don't propound weaker cockpits, if you read carefully, I am suggesting there might be a better safety trade to invest weight in a new rescue system instead of a new 16G cockpit. You don't have this choice under CS but you have it under UL. Of course if you can get both, without significant weight and CG effect and, at an affordable price, it would be the cherry on the cake!

Cert authorities have introduced regulation changes with the right intention in mind but, sometimes not appreciating the value/risk benefit. To use the previous example, if it was possible, from an overall safety standpoint I would rather fly a glider with a cockpit designed under previous cockpit structural requirements (e.g. Ventus 2, DG800, etc.) equipped with a rescue system, instead of a brand new V3 or JS3 designed per the new standards, without a rescue system.

If you are concerned about UL design in EU, you should look at the DULV (Germany) requirements. This is very comprehensive. Because Germany is a large market, UL manufacturers in EU make sure their design can pass the validation tests which can then be reused for other nations validation.

On Wednesday, August 19, 2020 at 9:49:11 AM UTC-7, Dan Marotta wrote:
Remember your high school chemistry (or was it physics?).Â* Water gives
up 1 calorie per gram per degree C while cooling.Â* To transition from
water at zero deg C to ice at zero deg C requires the loss of 80
calories per gram per degree C.Â* That's a lot of heat to be lost!Â* Sure,
you have a large surface area, but you have a very large volume as
well.Â* It would take quite some time to freeze a ballast tank.

Bottom line is I never worried about icing the ballast tanks (when I had
them) at sub-freezing temperatures.Â* Now freezing the dump valves is a
different issue, but not really if you fly your glider all the way to a
stop.Â* I once landed my LAK-17a with nearly 50 gallons on board and
didn't notice until after getting out of the glider.Â* Another time, one
dump valve stuck closed and, again, I landed with 25 gallons in one wing
and empty in the other.Â* I didn't notice until coming to a stop and the
full wing dropped heavily.

On 8/18/2020 8:06 PM, Eric Greenwell wrote:
wrote on 8/18/2020 3:54 PM:
On Tuesday, August 18, 2020 at 10:39:00 AM UTC-7, Eric Greenwell wrote:
jld wrote on 8/18/2020 9:57 AM:
Â*Â* "Glider pilots on the Allegheny Ridges (ridge soaring), in
Western US high deserts (thermal soaring), and in the Sierra wave
sometimes use higher wing loading"

Then the GP15 might be able to satisfy these US pilots as long as
they use antifreeze in the ballast :-).
Also you might not be able to get all the benefits of high WL if
you are limited by Vne due to high altitude.

I have been lucky to fly in Minden before.
Unless you compete in the WGC or are trying to beat a world record,
60 kg/m2 would already be A lot.

Bottom line, lets look for news from GP or the dealers to get
confirmation of configuration and delivery dates...

No antifreeze needed in the summer, as the temperatures at 18,000'
are not cold
enough to freeze the water in the wings. Winter wave flying is much
colder, of
course, and wave runners that get permission to fly above 18,000'
have to consider
the temperature at any time of the year.

According to the recent provisional manual, the GP15 VNE is 162 kts
IAS up to 3000
meters; 143 kts IAS at 6000 meters. That's about 195 kts TAS from
3000 meter on
up, so a pretty high limit, especially compared to my ASH26E, with
it's 143 kt
VNE. I don't know what modern gliders have for VNE, or wing loading,
for that matter.



Eric, what air temp do you regard as cold enough to freeze water in
the wings?

The situation I mentioned - summer in high desert areas - means ground
elevations of 5000' or more, and with ground temperatures of 90+, it
will be 25 deg F at 18,000. With the ups and downs of thermal flying,
the average temperature will be around freezing, so the water ballast
won't be cold enough long enough to freeze.

For other situations, I really don't know. In thermal conditions, I
wouldn't worry unless the minimum temperature went below 20 deg F.
Perhaps a temperature meter with a remote probe in the wing tank is
the safest thing. The glider handbook may have guidance, too. A
wireless sensor might be easiest to use for the wing



--
Dan, 5J

Water expands as it forms ice, so the pressure may rise enormously in trapped volumes (as in burst water pipes). Are there ballast vents apart from the valves, and do they freeze closed too? I'm waving my hands, maybe there is no worry, but personally I dump all water at 2C, as SH recommends.

You are correct about water expanding as it freezes.Â* It also contracts
to its smallest volume at 4 deg C, IIRC.Â* My point was that it takes a
long time for that mass to freeze.Â* I had not considered the tank vents
and, given their small relative diameter, I would expect them to freeze
well before the tanks if they have water inside them.

It is certainly not a bad idea to dump water as the manufacturer recommends.

On 8/19/2020 3:05 PM, wrote:
On Wednesday, August 19, 2020 at 9:49:11 AM UTC-7, Dan Marotta wrote:
Remember your high school chemistry (or was it physics?).Â* Water gives
up 1 calorie per gram per degree C while cooling.Â* To transition from
water at zero deg C to ice at zero deg C requires the loss of 80
calories per gram per degree C.Â* That's a lot of heat to be lost!Â* Sure,
you have a large surface area, but you have a very large volume as
well.Â* It would take quite some time to freeze a ballast tank.

Bottom line is I never worried about icing the ballast tanks (when I had
them) at sub-freezing temperatures.Â* Now freezing the dump valves is a
different issue, but not really if you fly your glider all the way to a
stop.Â* I once landed my LAK-17a with nearly 50 gallons on board and
didn't notice until after getting out of the glider.Â* Another time, one
dump valve stuck closed and, again, I landed with 25 gallons in one wing
and empty in the other.Â* I didn't notice until coming to a stop and the
full wing dropped heavily.

On 8/18/2020 8:06 PM, Eric Greenwell wrote:
wrote on 8/18/2020 3:54 PM:
On Tuesday, August 18, 2020 at 10:39:00 AM UTC-7, Eric Greenwell wrote:
jld wrote on 8/18/2020 9:57 AM:
Â*Â* "Glider pilots on the Allegheny Ridges (ridge soaring), in
Western US high deserts (thermal soaring), and in the Sierra wave
sometimes use higher wing loading"

Then the GP15 might be able to satisfy these US pilots as long as
they use antifreeze in the ballast :-).
Also you might not be able to get all the benefits of high WL if
you are limited by Vne due to high altitude.

I have been lucky to fly in Minden before.
Unless you compete in the WGC or are trying to beat a world record,
60 kg/m2 would already be A lot.

Bottom line, lets look for news from GP or the dealers to get
confirmation of configuration and delivery dates...
No antifreeze needed in the summer, as the temperatures at 18,000'
are not cold
enough to freeze the water in the wings. Winter wave flying is much
colder, of
course, and wave runners that get permission to fly above 18,000'
have to consider
the temperature at any time of the year.

According to the recent provisional manual, the GP15 VNE is 162 kts
IAS up to 3000
meters; 143 kts IAS at 6000 meters. That's about 195 kts TAS from
3000 meter on
up, so a pretty high limit, especially compared to my ASH26E, with
it's 143 kt
VNE. I don't know what modern gliders have for VNE, or wing loading,
for that matter.

Eric, what air temp do you regard as cold enough to freeze water in
the wings?
The situation I mentioned - summer in high desert areas - means ground
elevations of 5000' or more, and with ground temperatures of 90+, it
will be 25 deg F at 18,000. With the ups and downs of thermal flying,
the average temperature will be around freezing, so the water ballast
won't be cold enough long enough to freeze.

For other situations, I really don't know. In thermal conditions, I
wouldn't worry unless the minimum temperature went below 20 deg F.
Perhaps a temperature meter with a remote probe in the wing tank is
the safest thing. The glider handbook may have guidance, too. A
wireless sensor might be easiest to use for the wing


--
Dan, 5J
Water expands as it forms ice, so the pressure may rise enormously in trapped volumes (as in burst water pipes). Are there ballast vents apart from the valves, and do they freeze closed too? I'm waving my hands, maybe there is no worry, but personally I dump all water at 2C, as SH recommends.

--
Dan, 5J

On Wednesday, August 19, 2020 at 3:02:00 AM UTC-7, jld wrote:
""GP doesn't just claim "lower weight," but "far lower weight" than other gliders, but w/o any evidence to support this claim""
The evidences are in the design and certification choices.

GP15 is about same empty weight as the H301 which was a fiberglass ship, so there is nothing new. Carbon now allows to use lower relative thickness airfoil and higher aspect ratio wings to get to higher performance.

Certification requirements have forced manufacturers to significantly increase the weight of their gliders (e.g. cockpit protection). Because more recent airfoils are tolerant to higher WL, this has not been a significant issue, except for the fact MTM goes up and self launchers need more power!
By using experimental in US and UL in EU, GP has more design freedom. For example, not proposing a heavy 16G cockpit but a rescue parachute instead!

That is more closely akin to wishful thinking than evidence. Since GP isn't going to certify their gliders to EASA standards we do not know anything about their testing process. A ballistic chute is not going to help you unless you deploy it, which you can't do in the landing phase, the most likely time you will need a strengthened cockpit. My idea of evidence is things like the ultimate breaking strength of a wing taken to destruction (which you must do for EASA certification). Ultralights may be exempted from this testing by each member country so we will not even know if GP has done this test unless they produce the test results from an independent testing company.. I am just not willing to take such things on faith if my life depends upon it (which it does).

Tom

On Wednesday, August 19, 2020 at 6:21:50 AM UTC-7, Eric Greenwell wrote:
2G wrote on 8/18/2020 10:10 PM:
On Tuesday, August 18, 2020 at 7:26:51 PM UTC-7, Eric Greenwell wrote:
2G wrote on 8/18/2020 3:07 PM:
On Tuesday, August 18, 2020 at 1:49:35 PM UTC-7, andy l wrote:

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.
The motor can indeed be deployed and running in 5 seconds, and with considerable
confidence. The original mechanical mast switch, external to the mast, was deemed
too vulnerable to damage after Kawa's accident with the prototype glider. It was
replaced with two redundant, buried solid state switches to prevent a repeat of
the problem. You've had a similar switch failure on your Schleicher glider, but
were lucky that it eventually worked after repeated attempts. Other Schleicher
owners have also experienced mast switch failures, but Schleicher still uses the
external mechanical switches. Maybe they didn't get the memo?
--
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

I DIDN'T have a similar failure - in fact, I had no failure at all. The switch was in perfect working order, the only explanation was flying a little too fast for the mast to deploy fully. In any event, this has NOTHING to do with the outrageous claims being made by GP Gliders. No one should depend upon propulsion to start in an emergency.
My main point was we shouldn't judge a product on a failure in a prototype a
couple years ago, as there have been many changes made since then.

My apologies - I did not realize you'd concluded it was pilot error that caused
your problem; even so, other pilots have had failed switches, including myself.
For the particular failure I had, Schleicher did respond by switching to more
water resistant switches.

This is off topic, but since I fly a Schleicher glider with the same engine
system, how fast were you flying when the problem occurred?
--
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

I assume that I was flying too fast because no mechanical anomalies were found, including subsequent deployment tests on that same flight. My recollection was around 60kt (it certainly wasn't 70 or more). Looking at the flight track (https://www.onlinecontest.org/olc-3....l?dsId=4554327) I estimate that my IAS was around 60kt, which shouldn't have been too fast (there was an apparent tailwind of around 14kt that has to be subtracted from the ground speed). The ASH26e flight manual lists the max prop extend speed as 65kt. It would be a good test to find out what speed is too fast. But it is a single point of failure that can prevent the operation of the engine.

Tom

On Wed, 19 Aug 2020 10:48:30 -0600, Dan Marotta
wrote:

Remember your high school chemistry (or was it physics?).* Water gives
up 1 calorie per gram per degree C while cooling.* To transition from
water at zero deg C to ice at zero deg C requires the loss of 80
calories per gram per degree C.* That's a lot of heat to be lost!* Sure,
you have a large surface area, but you have a very large volume as
well.* It would take quite some time to freeze a ballast tank.

Bottom line is I never worried about icing the ballast tanks (when I had
them) at sub-freezing temperatures.* Now freezing the dump valves is a
different issue, but not really if you fly your glider all the way to a
stop.* I once landed my LAK-17a with nearly 50 gallons on board and
didn't notice until after getting out of the glider.* Another time, one
dump valve stuck closed and, again, I landed with 25 gallons in one wing
and empty in the other.* I didn't notice until coming to a stop and the
full wing dropped heavily.

.... text deleted

Maybe off topic, but what worried me in past years when I flew in the
New Mexico mountains was not the wing ballast tanks, but the tail
tank.

I always had visions of the tail tank freezing and failing to dump
when I dropped ballast, leaving my CG too far aft.

I usually left the tail tank empty if I was expecting high altitutes.

Bob

I fly NM with water regularly, both in the wings and the tail. I generally fly dry in the early spring when temperatures are still sub freezing at 17,000+ and start filling up during the summer. No problems so far, but if I do decide to use water in the tail tank when it's really cold, I can always add some propylene glycol antifreeze. Several of our more manic pilots do that and it seems to work well.

"My idea of evidence is things like the ultimate breaking strength of a wing taken to destruction (which you must do for EASA certification)"

It is up to GP to negotiate with DULV (Germany), but ultimate load test will have to be performed and DULV will probably ask to go to rupture since it is a brand new design. DULV also has to witness this type tests.
I was skeptical about UL for a long time until I took the time to dig into the different national regulations and realize most countries had very high standards.
if you can read German, here is a link to LTF-UL which defines requirements for approval.
https://www.dulv.de/sites/default/fi...V%201.22_0.pdf
There is an older version in English available from the net: https://drive.google.com/file/d/0BzP...ew?usp=sharing