👍Nice post. I tested this in my RV-7A also. There are two scenarios for an engine failure: Fuel starvation=wind-milling prop... and engine seizure=prop stopped. Wind-milling produces more drag than stopped. I tested mine both ways and found slightly better glide performance with the prop stopped. To get my Hartzell constant speed two bladed prop to stop (after engine shutdown), the airspeed had to be decreased to just above stall speed. Eventually, it flops to a stop. Your test results are reasonable for a side-by-side nose-dragger. I'm sure a taildragger tandem seat RV would have way LESS aerodynamic drag than mine... and better glide performance. Another useful number to determine is Minimum Sink speed....assuming you've glided to overhead a landing field and have lots of altitude remaining to work your problem. Well... A lot of this is splitting hairs with the glide performance numbers. HOW you fly your airplane in the first minutes of a sudden engine failure is more crucial. Obviously, turning immediately toward the nearest airport or landing area is important. I always have NRST airport displayed on my RNAV unit even on local flights. Energy conservation: If you're cruising at 130 knots when the engine quits, the best technique is to pitch up, trading speed for altitude until reaching best glide speed (80 kts) & THEN TRIM to stay there. That will stretch your overall glide distance much better than staying at altitude and bleeding energy due to drag. Practicing "Power Off 180's" in the pattern is also great practice for energy management. That is the most failed item on a Commercial Pilot checkride. Another tool is mastering the "Forward Slip to Landing".... That takes practice. Thanks for a great post, Flying Aardvark... Waldo
I took a Cessna 172B over on my airplane channel - and heavily modified the wings: STOL cuff, VGs, and wing extensions of 3 extra feet in length. I know my glide ratio changed, and I've been testing it but I haven't yet got a solid number. So I've kept a very conservative stock 172 ratio in Foreflight until I can finish testing.
Thanks for the info. I’ve also noticed that some of the glide ratios posted elsewhere in the interwebs seemed a bit optimistic. As a 6A owner I appreciate your test. I’d prefer to err on the side of caution running 7.5:1 as you did. I wasn’t going to kill the engine in flight as you did to find out so thanks for that too!
One more piece to the puzzle... The prop is still spinning during the engine-out descent. This is causing additional drag that would bring different numbers if you were able to get it to stop. I would think that at idle, the engine isn't producing "thrust" as much as it is assisting overcoming some of the drag that is created with the windmill pumping losses... Would be interesting to see how much it improves the results, with the prop stopped.
I haven't stopped the prop yet, but I have a SLSA with an absurdly conservative number in the POH. I did a series of tests, using autopilot to reduce the human factor, and I also tested reflex (negative) flap settings and zero. It's hard to test with winds though! I guess I'll have to go up when there's either a perfect crosswind in my test valley or find a time when the wind is near zero. I feel like I'm missing an obvious correction for wind speed so my numbers are still valid, I have the wind data since I'm pulling logs out of my panel anyhow.
@@flyingaardvarks1133 nothing exotic, just a Flight Design LSA. I know Pipistrels and Maules have reflex, RV10 does, and something like the Columbia or Lancair does as well.
Thank you for this! Awesome job. Companies should be forced to provide "correct glide ratios", It may matter to the extent of life or death! Guys and Gals... this deserves a thumbs up!
Interesting video but you neglected a very important factor - the windmilling propeller. There are two basic types of engine failures with two different glide ratios. Let's call the first, Type 1 - Engine isn't producing power but prop is windmilling. Type 2 - Engine seizes, prop stops. Type 2 has a significantly better glide ratio. You might consider a re-do where you pull the mixture then pull the nose up enough to stop the prop. If you do, I think you'll be amazed at the difference. I've tried it in a Citabria, huge difference, felt like I was in an early, low performance sailplane, gobs of time to glide to the ground. Thanks for the video but please address this important variable. John McClanahan, Atlanta
I like your video and I'm going to do more testing, but there are 2 points where I disagree. The way I have been adjusting my glide ring is totally different. Please let me know if you disagree. The way I do it is to go up to a reasonable altitude with my GR set on Foreflight and fly to a point where the green circle is just to the edge of an airport, and then I pull the power and see if I can make the airport. If I don't make it then I adjust the GR and try again. I care about the green ring, I don't care about the number. One question I have is how are you determining your horizontal distance with any degree of accuracy? I am sure your trig is very accurate, but that horizontal distance could be way off. The second point is that having the green ring set too close is just as bad as having it set too far. If I am flying over the Cascades and my engine quits then I'm going to immediately turn to an airport that I can make based on the green ring, but it would be even worse if I turned away from an airport that I could have made because it's just outside of my green ring because it was set too conservatively. I don't want to aim for a mountain snowfield if I could have made an airport. One additional point is that I have a Sling tsi and it has a CS prop which can fully feather. I need 2 glide rings, one with the engine windmilling and the other with a dead engine and the prop fully feathered. What I do is set my ForeFlight glide ring with it fully feathered, and the G3X glide ring set for the windmilling distance. My only problem is I don't really know what my feathered glide ring is because I'm too chicken to completely stop my engine to test it. Let me know what you think.
Hey, thanks. The horizontal distance is relatively easy with GPS. I am flying a straight track line (track not heading) direct to a gps point. I also did it both ways to account for wing.
Maybe I missed it but do you run a constant speed prop? My RV-7A got similar glide results but when I pulled the prop control the glide ratio went way up! I too did it with engine off. Nice work
Yup-CS prop. Going to test it in also (next) with the prop way back. But I will still keep my glide ration at 7.5 so I know “worst case” ie no pitch control.
👍Nice post. I tested this in my RV-7A also.
There are two scenarios for an engine failure: Fuel starvation=wind-milling prop... and engine seizure=prop stopped.
Wind-milling produces more drag than stopped.
I tested mine both ways and found slightly better glide performance with the prop stopped.
To get my Hartzell constant speed two bladed prop to stop (after engine shutdown), the airspeed had to be decreased to just above stall speed. Eventually, it flops to a stop.
Your test results are reasonable for a side-by-side nose-dragger. I'm sure a taildragger tandem seat RV would have way LESS aerodynamic drag than mine... and better glide performance.
Another useful number to determine is Minimum Sink speed....assuming you've glided to overhead a landing field and have lots of altitude remaining to work your problem.
Well... A lot of this is splitting hairs with the glide performance numbers. HOW you fly your airplane in the first minutes of a sudden engine failure is more crucial.
Obviously, turning immediately toward the nearest airport or landing area is important. I always have NRST airport displayed on my RNAV unit even on local flights.
Energy conservation: If you're cruising at 130 knots when the engine quits, the best technique is to pitch up, trading speed for altitude until reaching best glide speed (80 kts) & THEN TRIM to stay there. That will stretch your overall glide distance much better than staying at altitude and bleeding energy due to drag.
Practicing "Power Off 180's" in the pattern is also great practice for energy management. That is the most failed item on a Commercial Pilot checkride. Another tool is mastering the "Forward Slip to Landing".... That takes practice.
Thanks for a great post, Flying Aardvark...
Waldo
I took a Cessna 172B over on my airplane channel - and heavily modified the wings: STOL cuff, VGs, and wing extensions of 3 extra feet in length. I know my glide ratio changed, and I've been testing it but I haven't yet got a solid number. So I've kept a very conservative stock 172 ratio in Foreflight until I can finish testing.
Great video, honestly made me reconsider my glide performance settings in FF. I’m sure this will help a lot of pilots, thx!!
Thanks, and it sure was an eye opener for me!
Thanks for the info. I’ve also noticed that some of the glide ratios posted elsewhere in the interwebs seemed a bit optimistic. As a 6A owner I appreciate your test. I’d prefer to err on the side of caution running 7.5:1 as you did.
I wasn’t going to kill the engine in flight as you did to find out so thanks for that too!
Great video. Looking forward to the follow up with a stopped propeller.
When I did my, I got around 7.5. That was a lot less than I though it would be in a RV7a. Great vid Ace.
One more piece to the puzzle... The prop is still spinning during the engine-out descent. This is causing additional drag that would bring different numbers if you were able to get it to stop.
I would think that at idle, the engine isn't producing "thrust" as much as it is assisting overcoming some of the drag that is created with the windmill pumping losses...
Would be interesting to see how much it improves the results, with the prop stopped.
A part II?!?!?!
I haven't stopped the prop yet, but I have a SLSA with an absurdly conservative number in the POH. I did a series of tests, using autopilot to reduce the human factor, and I also tested reflex (negative) flap settings and zero. It's hard to test with winds though! I guess I'll have to go up when there's either a perfect crosswind in my test valley or find a time when the wind is near zero. I feel like I'm missing an obvious correction for wind speed so my numbers are still valid, I have the wind data since I'm pulling logs out of my panel anyhow.
Reflex? Wow--What are you flying?
@@flyingaardvarks1133 nothing exotic, just a Flight Design LSA. I know Pipistrels and Maules have reflex, RV10 does, and something like the Columbia or Lancair does as well.
Thank you for this! Awesome job. Companies should be forced to provide "correct glide ratios", It may matter to the extent of life or death!
Guys and Gals... this deserves a thumbs up!
Thanks, Robert!
Interesting video but you neglected a very important factor - the windmilling propeller. There are two basic types of engine failures with two different glide ratios. Let's call the first, Type 1 - Engine isn't producing power but prop is windmilling. Type 2 - Engine seizes, prop stops. Type 2 has a significantly better glide ratio. You might consider a re-do where you pull the mixture then pull the nose up enough to stop the prop. If you do, I think you'll be amazed at the difference. I've tried it in a Citabria, huge difference, felt like I was in an early, low performance sailplane, gobs of time to glide to the ground. Thanks for the video but please address this important variable. John McClanahan, Atlanta
Sounds like a good “part 2.” Will give it a try and see how different it is.
I like your video and I'm going to do more testing, but there are 2 points where I disagree. The way I have been adjusting my glide ring is totally different. Please let me know if you disagree. The way I do it is to go up to a reasonable altitude with my GR set on Foreflight and fly to a point where the green circle is just to the edge of an airport, and then I pull the power and see if I can make the airport. If I don't make it then I adjust the GR and try again. I care about the green ring, I don't care about the number. One question I have is how are you determining your horizontal distance with any degree of accuracy? I am sure your trig is very accurate, but that horizontal distance could be way off.
The second point is that having the green ring set too close is just as bad as having it set too far. If I am flying over the Cascades and my engine quits then I'm going to immediately turn to an airport that I can make based on the green ring, but it would be even worse if I turned away from an airport that I could have made because it's just outside of my green ring because it was set too conservatively. I don't want to aim for a mountain snowfield if I could have made an airport.
One additional point is that I have a Sling tsi and it has a CS prop which can fully feather. I need 2 glide rings, one with the engine windmilling and the other with a dead engine and the prop fully feathered. What I do is set my ForeFlight glide ring with it fully feathered, and the G3X glide ring set for the windmilling distance. My only problem is I don't really know what my feathered glide ring is because I'm too chicken to completely stop my engine to test it. Let me know what you think.
Hey, thanks. The horizontal distance is relatively easy with GPS. I am flying a straight track line (track not heading) direct to a gps point. I also did it both ways to account for wing.
Maybe I missed it but do you run a constant speed prop? My RV-7A got similar glide results but when I pulled the prop control the glide ratio went way up! I too did it with engine off. Nice work
Yup-CS prop. Going to test it in also (next) with the prop way back. But I will still keep my glide ration at 7.5 so I know “worst case” ie no pitch control.
It can glide directly to the crash site, every time….
Takeoffs are optional, landings are mandatory…
Nice Q-1 shirt.
Yessir!
You're obviously also assuming a straight line glide. Having to make a turn would affect your 'safe gliding distance'-no?
It would for sure
Glide "radio"? Really? At least proofread the title..
Ha-thanks. Fixed it.