Minimum acceptable self-launch climb rate

I really would like to second Steve message.
Because the prop used on existing self launchers have very little speed Range, their pitch is selected to provide a narrow compromise between takeoff speed and climb speed.
This allows to have sufficient thrust during takeoff run, but reduces the climb speed.
From my precedent message, it is not pleasant at all, especially when density altitude gets high and the feeling gets worse with low IAS and less than 3 knots of climb.

Modern props with significant ESR effect (Extended Speed Range) could be used to improve the situation without compromising performance (you would still get the higher drag from the pylon/engine).

When looking at the GP prop, they seem to be using modern airfoils which should exhibit the necessary ESR effect (good question to ask GP)
Because of the low drag pylon and better electric motor speed/torque control, the climb rate should be good over a large speed range compared to existing combustion engine self launchers.

On Monday, 27 April 2020 15:46:46 UTC-6, Dave Nadler wrote:
On Monday, April 27, 2020 at 2:22:15 PM UTC-4, jfitch wrote:
Last year I took two tows behind a Pawnee...

Reminds me of a western tow a couple years ago...

The task will open in 15 minutes.
CD, can you hold that, YO is still at 1600 feet on tow.
... and 5 minutes later ...
The task will open in 15 minutes.
CD, can you hold that, YO is still on tow, 1500 feet and descending.
IIRC, I gave up at 1300 feet, pulled the release, and climbed out...

Some of you were in the air waiting...

I was laughing reading this YO as I remember it vividly. You and your Arcus and UGLY the tow plane just did not mesh well. No fault on either end of the rope, sometimes combinations just do not function well.

The look on your face a day or two later when I had UGLY pull onto the runway in front of your glider before waving it off was priceless.

FWIW UGLY the tow plane is/was a Calair and was the work horse at Morgan UT airport for years. It has been retired after hitting power lines on the way to Nephi a couple of ago. Both pilot and aircraft survived but aircraft had to be retired.

I also agree with Eric. Having been flying an ASH26e and recently a
Ventus self-launcher I have never been in the slightest concerned about climbing at around 54 knots. It is totally different from being on an aerotow.. I would definitely not want to trade climb rate for climb speed. The only thing to be very aware of is the pitch change when the propulsion stops before the engine is retracted.

I used to self-launch in an Arcus M and many other types. I was happy that the Arcus had a significant margin between best climb RPM and redline. IIRC about 400rpm margin.
In turbulent conditions, close to the ground, I could maintain 63kts while climbing.

I guess the same applies to the DG1001M and Quintus, but I don't remember precisely.

Redline is a serious concern in the DG600M. Probably a little less so in the DG400.

Aldo Cernezzi

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.

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.


--
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 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.


--
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

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.

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

I've had two Rotax 912 seizures in a Pipistrel Sinus.Â* In each case I
was at or below 200' AGL.Â* In both cases I turned back and landed safely
without undue concern other than being extremely ****ed off. In the
first case, the engine seized so quickly that the 6 bolts holding the
prop onto the hub sheared and the prop windmilled like a pinwheel almost
separating from the aircraft.

In the second event, I noticed reduced climb rate, and reduced pitch.Â*
Then the RPM dropped slightly.Â* At that point, again at or below 200'
AGL and still over the runway but too far down to land straight ahead, I
started to turn back.Â* About half way through the turn it threw a rod
through the crank case, filling the cockpit with smoke and covering the
windscreen with oil.Â* I landed on the parallel taxiway.

The root cause for both failures was that Pipistrel replaced the hose
from the oil cooler to the oil pump with one with internal wire bracing
and did make note in the Illustrated Parts Breakdown.Â* When the hoses
were replaced with Rotax recommended hoses at 5 years, the hose in
question, having a tight bend, collapsed when it heated up starving the
engine.Â* The wire braced hose would not have failed that way.

On 4/28/2020 3:56 PM, wrote:
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.


--
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
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.


--
Dan, 5J

"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"

You cannot do that last bit in an Arcus M - when you turn the engine off it commences the prop lowering process. In the ASH 26 I had before I did try this sort of stuff and would have been confident of a turn back from 200 foot. I think it would also be fine in the Arcus. However from my club's small grass field I am vulnerable to a potentially damaging off field arrival from about 50 foot to about 200 foot.

The only relevant power failure I have had was in the Arcus just after lift off, at 5 foot or less off the ground. There was a drive belt failure, and the glider plonked down rather heavily on the ground - instead of the lift component of the engine power I now had no power and a high drag prop mast.. Happily no damage done other than by the flailing drive belt(s). Since then I have tried to stay just above the ground until achieving say 55 knots.

In the Arcus while best climb rate is supposed to be about 52 knots, you can climb quite a lot faster without over-revving and without much sacrifice of climb rate - and there is a rev limiter which you could only hit in level flight, probably about 90 knots.