Minimum acceptable self-launch climb rate

What's the minimum realistic climb rate that should be acceptable for self-launch? I've heard things like 1:4 ratio of thrust to MTOW (where thrust is approximated as 3x motor/engine power), but planes like the Silent 2 Electro and miniLAK FES seem to exceed this somewhat, with the miniLAK FES having a ratio approaching 1:5.5. The S2E's flight manual publish a climb rate somewhere around 400fpm, and just based on the numbers I would expect the miniLAK FES to be around 300fpm.

The GP 15 Jeta has a ratio of 1:6.3, which is far lower than the rule of thumb for powered flight. Yet, I don't hear anyone complaining.

And gas-powered craft might have 500fpm at sea-level, but they certainly can't attain anywhere near that at higher (density) altitudes.

So while all this sounds slow, when I compare to stall speeds I find that self-launch gliders' overall performance is generally 2-3x better than the FAA's minimum requirement of 200'/1nm for instrument flight (that's the closest I could find to a hard and fast rule for climb rates). So it would suggest that quick climb rates aren't necessary if the forward flight speed is very low.

So what's the right real-world response? Is there a certain absolute minimum for safe glider flight, or is it better to have a great climb angle rather than a great climb rate?

On Sunday, April 26, 2020 at 1:38:33 PM UTC-4, Kenz Dale wrote:
What's the minimum realistic climb rate that should be acceptable for self-launch?

I can just tell you my experience with two different ships. My first self-launch was a Silent-IN Club. I got 400 fpm. Flew it for several years and put 500 hours on it. Great intro bird for self-launch.

But, my second self-launch is a DG-400. I get between 600-700 fpm at a much steeper angle. Immensely more comfortable. The oh crap period on climb out is much shorter. Love my 400.

Kevin
92

On Sunday, April 26, 2020 at 1:38:33 PM UTC-4, Kenz Dale wrote:
...that quick climb rates aren't necessary if the forward flight speed is very low.

Seems like it would depend on where and when you want to takeoff. Some airports have shorter runways with sink, strong wind and wind shear close to the ground on good soaring days. Slow speed over the ground leaves me in the sink for a longer time. Low climb rate leaves me in the wind shear for longer. Low airspeed and windshear seem like a bad combination.

On Sunday, April 26, 2020 at 1:38:33 PM UTC-4, Kenz Dale wrote:
What's the minimum realistic climb rate that should be acceptable for self-launch? I've heard things like 1:4 ratio of thrust to MTOW (where thrust is approximated as 3x motor/engine power), but planes like the Silent 2 Electro and miniLAK FES seem to exceed this somewhat, with the miniLAK FES having a ratio approaching 1:5.5. The S2E's flight manual publish a climb rate somewhere around 400fpm, and just based on the numbers I would expect the miniLAK FES to be around 300fpm.

The GP 15 Jeta has a ratio of 1:6.3, which is far lower than the rule of thumb for powered flight. Yet, I don't hear anyone complaining.

And gas-powered craft might have 500fpm at sea-level, but they certainly can't attain anywhere near that at higher (density) altitudes.

So while all this sounds slow, when I compare to stall speeds I find that self-launch gliders' overall performance is generally 2-3x better than the FAA's minimum requirement of 200'/1nm for instrument flight (that's the closest I could find to a hard and fast rule for climb rates). So it would suggest that quick climb rates aren't necessary if the forward flight speed is very low.

So what's the right real-world response? Is there a certain absolute minimum for safe glider flight, or is it better to have a great climb angle rather than a great climb rate?

CS 22 - Certification Specifications for Sailplanes and Powered Sailplanes - has standards.

"CS 22.51 Take-off
(a) For a powered sailplane the take-off distance at maximum weight and in zero wind, from rest to attaining a height of 15 m must be determined and must not exceed 500 m when taking off from a dry, level, hard surface. In demonstration of the take-off distance, the powered sailplane must be allowed to reach the selected speed promptly after lifting off and this speed must be maintained throughout the climb.
(b) The selected speed must not be less than;
(1) 1·3 VS1, or
(2) any lesser speed, not less than 1·15 VS1, that is shown to be safe under all reasonably expected operating conditions, including turbulence and complete engine failure.
CS 22.65 Climb
(a) For a powered sailplane the time for climb from leaving the ground up to 360 m above the field must not exceed four minutes with:
(1) not more than take-off power;
(2) landing gear retracted;
(3) wing-flaps in take-off position;
(4) cowl flaps (if any) in the position used in the cooling tests.
(b) For self-sustaining powered sailplanes, the maximum altitude that can be sustained must be determined."
https://www.easa.europa.eu/sites/def...S-22_Amendment 1 revised.pdf

On Sunday, April 26, 2020 at 12:24:31 PM UTC-7, Dan Daly wrote:
On Sunday, April 26, 2020 at 1:38:33 PM UTC-4, Kenz Dale wrote:
What's the minimum realistic climb rate that should be acceptable for self-launch? I've heard things like 1:4 ratio of thrust to MTOW (where thrust is approximated as 3x motor/engine power), but planes like the Silent 2 Electro and miniLAK FES seem to exceed this somewhat, with the miniLAK FES having a ratio approaching 1:5.5. The S2E's flight manual publish a climb rate somewhere around 400fpm, and just based on the numbers I would expect the miniLAK FES to be around 300fpm.

The GP 15 Jeta has a ratio of 1:6.3, which is far lower than the rule of thumb for powered flight. Yet, I don't hear anyone complaining.

And gas-powered craft might have 500fpm at sea-level, but they certainly can't attain anywhere near that at higher (density) altitudes.

So while all this sounds slow, when I compare to stall speeds I find that self-launch gliders' overall performance is generally 2-3x better than the FAA's minimum requirement of 200'/1nm for instrument flight (that's the closest I could find to a hard and fast rule for climb rates). So it would suggest that quick climb rates aren't necessary if the forward flight speed is very low.

So what's the right real-world response? Is there a certain absolute minimum for safe glider flight, or is it better to have a great climb angle rather than a great climb rate?

CS 22 - Certification Specifications for Sailplanes and Powered Sailplanes - has standards.

"CS 22.51 Take-off
(a) For a powered sailplane the take-off distance at maximum weight and in zero wind, from rest to attaining a height of 15 m must be determined and must not exceed 500 m when taking off from a dry, level, hard surface. In demonstration of the take-off distance, the powered sailplane must be allowed to reach the selected speed promptly after lifting off and this speed must be maintained throughout the climb.
(b) The selected speed must not be less than;
(1) 1·3 VS1, or
(2) any lesser speed, not less than 1·15 VS1, that is shown to be safe under all reasonably expected operating conditions, including turbulence and complete engine failure.
CS 22.65 Climb
(a) For a powered sailplane the time for climb from leaving the ground up to 360 m above the field must not exceed four minutes with:
(1) not more than take-off power;
(2) landing gear retracted;
(3) wing-flaps in take-off position;
(4) cowl flaps (if any) in the position used in the cooling tests.
(b) For self-sustaining powered sailplanes, the maximum altitude that can be sustained must be determined."
https://www.easa.europa.eu/sites/def...S-22_Amendment 1 revised.pdf

When reading the manufacturer's sales brochure, remember that the advertised climb will usually be for standard atmosphere at sea level. For gas engines, the climb rate will be significantly less if you plan to fly in the US western states in summer.

Thanks, Dan, you knocked it out of the park with this answer.

CS 22 - Certification Specifications for Sailplanes and Powered Sailplanes - has standards.

"CS 22.51 Take-off
(a) For a powered sailplane the take-off distance at maximum weight and in zero wind, from rest to attaining a height of 15 m must be determined and must not exceed 500 m when taking off from a dry, level, hard surface. In demonstration of the take-off distance, the powered sailplane must be allowed to reach the selected speed promptly after lifting off and this speed must be maintained throughout the climb.
(b) The selected speed must not be less than;
(1) 1·3 VS1, or
(2) any lesser speed, not less than 1·15 VS1, that is shown to be safe under all reasonably expected operating conditions, including turbulence and complete engine failure.
CS 22.65 Climb
(a) For a powered sailplane the time for climb from leaving the ground up to 360 m above the field must not exceed four minutes with:
(1) not more than take-off power;
(2) landing gear retracted;
(3) wing-flaps in take-off position;
(4) cowl flaps (if any) in the position used in the cooling tests.
(b) For self-sustaining powered sailplanes, the maximum altitude that can be sustained must be determined."
https://www.easa.europa.eu/sites/def...S-22_Amendment 1 revised.pdf

My Stemme gets 800 ft/min at 8,000' density altitude but it's
turbocharged. :-D If I'm repositioning for a safari or such, I climb
straight up to 18,000' MSL and cruise at 140 KTAS.Â* But it sure isn't a
fingertip light ship to fly. :-(

On 4/26/2020 4:44 PM, Kenz Dale wrote:
Thanks, Dan, you knocked it out of the park with this answer.

CS 22 - Certification Specifications for Sailplanes and Powered Sailplanes - has standards.

"CS 22.51 Take-off
(a) For a powered sailplane the take-off distance at maximum weight and in zero wind, from rest to attaining a height of 15 m must be determined and must not exceed 500 m when taking off from a dry, level, hard surface. In demonstration of the take-off distance, the powered sailplane must be allowed to reach the selected speed promptly after lifting off and this speed must be maintained throughout the climb.
(b) The selected speed must not be less than;
(1) 1·3 VS1, or
(2) any lesser speed, not less than 1·15 VS1, that is shown to be safe under all reasonably expected operating conditions, including turbulence and complete engine failure.
CS 22.65 Climb
(a) For a powered sailplane the time for climb from leaving the ground up to 360 m above the field must not exceed four minutes with:
(1) not more than take-off power;
(2) landing gear retracted;
(3) wing-flaps in take-off position;
(4) cowl flaps (if any) in the position used in the cooling tests.
(b) For self-sustaining powered sailplanes, the maximum altitude that can be sustained must be determined."
https://www.easa.europa.eu/sites/def...S-22_Amendment 1 revised.pdf

--
Dan, 5J

On Sunday, April 26, 2020 at 10:38:33 AM UTC-7, Kenz Dale wrote:
What's the minimum realistic climb rate that should be acceptable for self-launch? I've heard things like 1:4 ratio of thrust to MTOW (where thrust is approximated as 3x motor/engine power), but planes like the Silent 2 Electro and miniLAK FES seem to exceed this somewhat, with the miniLAK FES having a ratio approaching 1:5.5. The S2E's flight manual publish a climb rate somewhere around 400fpm, and just based on the numbers I would expect the miniLAK FES to be around 300fpm.

The GP 15 Jeta has a ratio of 1:6.3, which is far lower than the rule of thumb for powered flight. Yet, I don't hear anyone complaining.

And gas-powered craft might have 500fpm at sea-level, but they certainly can't attain anywhere near that at higher (density) altitudes.

So while all this sounds slow, when I compare to stall speeds I find that self-launch gliders' overall performance is generally 2-3x better than the FAA's minimum requirement of 200'/1nm for instrument flight (that's the closest I could find to a hard and fast rule for climb rates). So it would suggest that quick climb rates aren't necessary if the forward flight speed is very low.

So what's the right real-world response? Is there a certain absolute minimum for safe glider flight, or is it better to have a great climb angle rather than a great climb rate?

As a practical matter, the climb angle should significantly exceed the glide angle with the engine not operating but deployed, at the density altitude of your field. That way the engine cannot take you to a place you can't get back from. If your dirty glide is 20:1 @ 50 knots, that's 260 ft/min so you'd want a climb rate of 350 or so. The C22 climb criteria (1200 ft in 4 min) suggests a minimum climb rate of 300. That'd be real minimum for me. FES may be slower climbing but also cleaner gliding with a failed motor, so a step back and a step ahead.

I'd be careful of brochure or owner claimed climb rates. Look at the IGC files to be sure. I get about 880 ft/min at sea level and about 530 at 9000 ft density altitude (averaged over many flights, from IGC data - I wrote an app to analyze multiple files automatically).

On Sunday, April 26, 2020 at 10:38:33 AM UTC-7, Kenz Dale wrote:
What's the minimum realistic climb rate that should be acceptable for self-launch? I've heard things like 1:4 ratio of thrust to MTOW (where thrust is approximated as 3x motor/engine power), but planes like the Silent 2 Electro and miniLAK FES seem to exceed this somewhat, with the miniLAK FES having a ratio approaching 1:5.5. The S2E's flight manual publish a climb rate somewhere around 400fpm, and just based on the numbers I would expect the miniLAK FES to be around 300fpm.

The GP 15 Jeta has a ratio of 1:6.3, which is far lower than the rule of thumb for powered flight. Yet, I don't hear anyone complaining.

And gas-powered craft might have 500fpm at sea-level, but they certainly can't attain anywhere near that at higher (density) altitudes.

So while all this sounds slow, when I compare to stall speeds I find that self-launch gliders' overall performance is generally 2-3x better than the FAA's minimum requirement of 200'/1nm for instrument flight (that's the closest I could find to a hard and fast rule for climb rates). So it would suggest that quick climb rates aren't necessary if the forward flight speed is very low.

So what's the right real-world response? Is there a certain absolute minimum for safe glider flight, or is it better to have a great climb angle rather than a great climb rate?

hi guys i was wondering why most of the groups on google groups are from 6or 7 years ago\

Kenz Dale wrote on 4/26/2020 10:38 AM:
What's the minimum realistic climb rate that should be acceptable for self-launch? I've heard things like 1:4 ratio of thrust to MTOW (where thrust is approximated as 3x motor/engine power), but planes like the Silent 2 Electro and miniLAK FES seem to exceed this somewhat, with the miniLAK FES having a ratio approaching 1:5.5. The S2E's flight manual publish a climb rate somewhere around 400fpm, and just based on the numbers I would expect the miniLAK FES to be around 300fpm.

The GP 15 Jeta has a ratio of 1:6.3, which is far lower than the rule of thumb for powered flight. Yet, I don't hear anyone complaining.

And gas-powered craft might have 500fpm at sea-level, but they certainly can't attain anywhere near that at higher (density) altitudes.

So while all this sounds slow, when I compare to stall speeds I find that self-launch gliders' overall performance is generally 2-3x better than the FAA's minimum requirement of 200'/1nm for instrument flight (that's the closest I could find to a hard and fast rule for climb rates). So it would suggest that quick climb rates aren't necessary if the forward flight speed is very low.

So what's the right real-world response? Is there a certain absolute minimum for safe glider flight, or is it better to have a great climb angle rather than a great climb rate?

I don't think you should pay any attention to estimated thrust. What you want to
know is the climb rate, and that is always given by the brochure or handbook, and
most owners know about what their plane really does.

Based on 25 years of flying my ASH26E, I want at least 500 fpm at the weight I
would normally expect to fly. Don't use MTOW, as that gives you a very distorted
picture if you compare a Silent 2 Electro with a GP15, which can fly at a far
higher wing loading than the Electro.

The GP15 is rated at 865 fpm (large battery, 705 lbs takeoff weight, 8.4 lb/ft2).
That's a lot better than an Electro or miniLak, two of the gliders I considered
before deciding to buy the GP15. Compare it to my ASH26E, which is around 600 fpm
at the same wing loading, and drops off at higher density altitudes. So, the GP15
should be significantly better at places like Minden, Ely, and Parowan, as it's
electric propulsion does not lose nearly as much power at those places.

The maximum weight I expect to fly at (1010 lbs) gives a 12 lb/ft2 wing loading,
and I estimate the climb rate would be about 600 fpm.

--
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