GP Gliders GP 14 Velo has finally FLOWN!!!

On Saturday, November 26, 2016 at 12:06:03 AM UTC-5, son_of_flubber wrote:
Will GP electric drive gliders be certified to aerotow with the boom deployed and the motor turned off? (Boom extended in case of PT3. Aerotow to save the battery charge for later in the flight.)

Sorry that I cannot point to specifics, but I read somewhere that towing gliders with the boom extended and the motor running is sometimes done in Europe in order to compensate for low powered tugs. This would be a good reason for GP to certify for extending the boom during aerotow.

As Andrzej noted, the prop on the GP has less drag when it is folded. And the motor looks sleek. And since it is electric, I'd guess that you could dial in just enough thrust to negate the drag of the extended boom (and save the batteries for later).

Being able to use FES to recover from PT3 is very appealing if you launch from a short runway with limited low altitude PT3 options. A plus if GP offered comparable functionality.

That said, as battery costs comes down and power density increases, aerotowing a self-launch capable electric glider will at some point stop making sense. Maybe that will happen sooner rather than later.

Do self launch gliders have the climb rate and stability to deal with strong sink on launch and the rotor associated with wave, or are they marginal on turbulent days?

At 05:55 28 November 2016, son_of_flubber wrote:
On Saturday, November 26, 2016 at 12:06:03 AM UTC-5, son_of_flubber
wrote:
Will GP electric drive gliders be certified to aerotow with the boom
depl=
oyed and the motor turned off? (Boom extended in case of PT3. Aerotow
to
=
save the battery charge for later in the flight.)

Sorry that I cannot point to specifics, but I read somewhere that towing
gl=
iders with the boom extended and the motor running is sometimes done in
Eur=
ope in order to compensate for low powered tugs. This would be a good
reaso=
n for GP to certify for extending the boom during aerotow.

As Andrzej noted, the prop on the GP has less drag when it is folded.
And
=
the motor looks sleek. And since it is electric, I'd guess that you
could
=
dial in just enough thrust to negate the drag of the extended boom (and
sav=
e the batteries for later).

Being able to use FES to recover from PT3 is very appealing if you launch
f=
rom a short runway with limited low altitude PT3 options. A plus if GP
offe=
red comparable functionality.

That said, as battery costs comes down and power density increases,
aerotow=
ing a self-launch capable electric glider will at some point stop making
se=
nse. Maybe that will happen sooner rather than later.

Do self launch gliders have the climb rate and stability to deal with
stron=
g sink on launch and the rotor associated with wave, or are they marginal
o=
n turbulent days? =20

The first flights of the GP Velo indicate an average climb under power of
4m/s, this is very encouraging and also very safe. See
https://www.facebook.com/gpgliders/

I do push-pulls with my Ventus cM from time to time. I wouldn't dream of doing this in heavy turbulence...

On Monday, November 28, 2016 at 12:55:50 AM UTC-5, son_of_flubber wrote:
On Saturday, November 26, 2016 at 12:06:03 AM UTC-5, son_of_flubber wrote:
Will GP electric drive gliders be certified to aerotow with the boom deployed and the motor turned off? (Boom extended in case of PT3. Aerotow to save the battery charge for later in the flight.)

Sorry that I cannot point to specifics, but I read somewhere that towing gliders with the boom extended and the motor running is sometimes done in Europe in order to compensate for low powered tugs. This would be a good reason for GP to certify for extending the boom during aerotow.

As Andrzej noted, the prop on the GP has less drag when it is folded. And the motor looks sleek. And since it is electric, I'd guess that you could dial in just enough thrust to negate the drag of the extended boom (and save the batteries for later).

Being able to use FES to recover from PT3 is very appealing if you launch from a short runway with limited low altitude PT3 options. A plus if GP offered comparable functionality.

That said, as battery costs comes down and power density increases, aerotowing a self-launch capable electric glider will at some point stop making sense. Maybe that will happen sooner rather than later.

Do self launch gliders have the climb rate and stability to deal with strong sink on launch and the rotor associated with wave, or are they marginal on turbulent days?

Here I go, again. It's that perspective thing. If the subject is new toys and inventing the rationalization that gets them purchased despite the SO's concern about the bank balance, then I'm OT. If the subject is safety in launching, then Flubber's question is badly framed. I care about safety in launching, so:

The PT3s that are life threatening often *aren't the ones that a second power source is going to help with*. Wing down/bad ground loop at flying speed, controls not hooked up or other assembly fault, dive brakes open, canopy open, that sort of thing. Yes, you can invent scenario in which the electric miracle flies you away from an accident. More often, we see crappy PIC decision making turn a completely manageable situation into a very dangerous & sometimes fatal accident (I can rattle you off a long, sorry list of real, completely preventable PT3 accidents). Safety-wise, I remain an advocate for grasping the low hanging fruit first, and I still see plenty of it. It has nothing to do with new toys and everything to do with basic airmanship.

Who can name a PT3 accident that would have been prevented with instant-on electric propulsion that didn't have some other really obvious solution? I can't think of one off hand. I think these are rare.

Sitting in the back seat of our L23, I've watched nearly everyone I've flown with reach for something on the panel, fiddle with an air vent, look at a wing tip or do some other completely unnecessary thing below 500'. This can have consequences. The last PT3 we had at our airport was the guy who decided to retract his gear on tow, just because he could. Unsurprisingly, he got way out of position and next thing he knew, he was putting the gear right back down again! It doesn't get any more preventable than that.

If you want to improve your odds w.r.t. PT3 survival in particular, or emergency handling in general, the smart money is on training & critique. Increasing the complexity of your aircraft or procedures, not so much.

Evan Ludeman / T8

Well, on my airfield (and a lot of others here in Europe I know of), an aborted aerotow at the end of the field (rope brakes, tug enigines fumes...) will result in a total loss of the glider should there be no instant supply of alternate propulsion.
Nothing to do with training : in this position at 100 ft off the ground, the only choise is what to crash into.

Any worries about the motor eating the rope if it breaks/releases on the tug end? I'm sure the noise would be distracting...

On Monday, November 28, 2016 at 6:50:37 PM UTC+3, Tango Whisky wrote:
Well, on my airfield (and a lot of others here in Europe I know of), an aborted aerotow at the end of the field (rope brakes, tug enigines fumes...) will result in a total loss of the glider should there be no instant supply of alternate propulsion.
Nothing to do with training : in this position at 100 ft off the ground, the only choise is what to crash into.

That is .. terrible. I can't imagine that being tolerated at any club in NZ.. Maybe on a one-off retrieve from a paddock (and maybe not!), but not day to day operation, with members of the public, early solo students...

When I started, my club was towing Blaniks with Super Cubs, from an airfield surrounded by farms. When we started to trade the Blaniks for heavy glass two seaters (Twin Astir and Janus) and the farms turned into housing developments, tows on no wind hot days were getting unacceptably low over the fence and houses. We pretty promptly swapped the Cubs for powerful Pawnees. Problem solved.

Now that the club has moved this year to from a public airfield to a private 2 km long grass strip we've swapped the Pawnees for a brand new Skylaunch winch, and thinking about an LSA such as the Dynamic WT9 for remaining towing duties.

Le lundi 28 novembre 2016 17:11:31 UTC+1, a écritÂ*:
Any worries about the motor eating the rope if it breaks/releases on the tug end? I'm sure the noise would be distracting...

Not really. I had the occasion to watch the rope being cut by the towplane pilot (it had to be changed, so we turned this into an exercise), and it actually drops well below the glider.
Now, if you are in a turbulent situation where you cannot control the slack anymore, that rope could be all over the place. That's why I wouldn't do push-pulls in such a situation.
Also, on a push-pull you need to have a briefing with the tug pilot. Ha has to known what to do if he encounters a problem during the take-off run (i.e. no brakes, evacuate to which side etc).

On Monday, November 28, 2016 at 10:50:37 AM UTC-5, Tango Whisky wrote:
Well, on my airfield (and a lot of others here in Europe I know of), an aborted aerotow at the end of the field (rope brakes, tug enigines fumes...) will result in a total loss of the glider should there be no instant supply of alternate propulsion.
Nothing to do with training : in this position at 100 ft off the ground, the only choise is what to crash into.

Does this describe even 5% of PT3 accidents? It surely doesn't in the USA, and that was my point.

best,
Evan

On Monday, November 28, 2016 at 9:31:24 AM UTC-7, Tango Whisky wrote:
Le lundi 28 novembre 2016 17:11:31 UTC+1, a écritÂ*:
Any worries about the motor eating the rope if it breaks/releases on the tug end? I'm sure the noise would be distracting...

Not really. I had the occasion to watch the rope being cut by the towplane pilot (it had to be changed, so we turned this into an exercise), and it actually drops well below the glider.
Now, if you are in a turbulent situation where you cannot control the slack anymore, that rope could be all over the place. That's why I wouldn't do push-pulls in such a situation.
Also, on a push-pull you need to have a briefing with the tug pilot. Ha has to known what to do if he encounters a problem during the take-off run (i.e. no brakes, evacuate to which side etc).

You probably wouldn't want to do this in low tow - the standard in some countries and many clubs. In turbulent thermals, I had the tow rope snake back over the canopy and wings a couple of times when my ballasted open-class ship over-ran the tug.

Mike