wrote on 4/28/2020 2:56 PM:
On Tuesday, April 28, 2020 at 10:25:27 AM UTC-7, Eric Greenwell wrote:
wrote on 4/28/2020 8:16 AM:

The typical slow self launch climbout speed arguably makes a self launch more hazardous than an aerotow or a winch launch until above 500ft, which takes a couple of minutes. The climb speed is lower than the typical approach speed, and the speed would drop fast, due to the nose up attitude, the flap use for climb, and the sudden windmill drag, which will try to increase the pitch-up for a mast design. I find it best to approach at Minden in my ventus 2cxM at a speed much higher than the climbout speed: I approach at 70kts in summer, due to the typical changeable, windy conditions, only slowing in the last 50ft.

My experience is much different than yours. I think self-launch in my ASH26E is
safer than towing or winch, because I am in complete control. There is no chance
miscommunication, no chance of entanglement with a rope or parachute, no need to
fly formation or operate at a very high pitch attitude.

At the places I fly, I can land straight ahead from less than 100' agl, and do a
180 back to the runway over 200' agl - the same numbers I would use for a typical
tow. At 600 fpm climb, that's only 10 seconds of "aw snap!" if the engine stops
between 100' and 200', same as for a tow. If the engine quits (never has), I will
just nose down to keep the speed correct, then use my pre-determined plan for the
situation, same as if I was being towed. I've practiced this at altitude, examined
the IGC file, so I'm confident it would work as well as it would with a tow failure.

I've flown at Minden, Ely, and Parowan many times over 25 years with the 26E, and
never had a problem with handling turbulence on takeoff; I do land as you do in
the often much more turbulent afternoon.



Hi Eric, your points are all true, and on balance I prefer a motorglider. But just not for the first minute of takeoff. Although I don't feel personally endangered, an engine failure would probably force me to sacrifice my motorglider to preserve my safety. From 200ft, starting nose up at best climb speed (51-54kts), flaps +2 and engine windmilling, I very much doubt I could do a safe 180 in my glider (Ventus 2cxm). I've I've never dared try it, and I've never heard of anyone trying it. In contrast, simulated aerotow failures from 200ft in gliders is practiced as part of standard training. Similarly, a winch failure at any time should be able to be safely handled.

Surely, there is a period after takeoff when you can still land straight ahead
without damage? In my usual locations, I can be as high as 100' and still do that
- what about your locations?

You can simulate an engine failure during a launch at a safe altitude. I've done
at 2000'-3000':
- set your flight recorder to 1 second intervals, to get the best flight trace data
- at altitude, configure the glider for takeoff: gear down, flaps normally used
- line up on a long, straight road or similar
- establish a steady, full power climb at your normal climb speed
- climb for 200' or so, then set throttle to idle, and do a 180 degree turn,
lining up on the that road
- repeat the test, but this time, turn the ignition off, then turn as before

After you are done flying, you can download the flight trace to determine how much
altitude you lost. From that, you can judge how high you want to be before making
a 180 degree turn. I was surprised at how little altitude loss there was during
the turn. Ditto for my friend in his DG400, when he tried it. I don't know how
well a Ventus 2CXM will do, but I suspect it's not any worse than a DG400;
regardless, it gives you actual numbers to work with.

Some will point out a 180 degree turn leaves you offset from the runway, and you
need to do more turning to line up. Yup - unless you drift away from the runway
during your climb, making a 180 degree sufficient to line you up with runway.


--
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