YOUR FLIGHT INSTRUCTOR WAS WRONG! - Simulated vs Real Engine Failure
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- Опубліковано 5 жов 2024
- After quite a few comments telling me I was wrong when I said that a plane at idle (like in a simulated engine out) glides better than a plane with the propeller stopped in an actual engine out, including a few alongs the lines of "I asked both of my instructors and they both said an idling engine creates more drag." Well, at least in my plane after testing both scenarios, your flight instructor was wrong! Obviously it may vary depending on type of aircraft, motor, and propeller but in our case a simulated engine out will give a better glide ratio than a real engine out scenario.
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I would like to point out the propeller is merely a big fan that keeps the pilot cooled. I know this because when it stops the pilot started sweating.
Really?? Wow, Why dont you patent that thought??
Where’d you get that? The original store??
So true, so true . That is the reason nothing beats gliders ......
@@istra70 Is it because glider pilots beats themselves?
@@johnrumpf8559 i mean it could be his...
9:45 Minimum Sink speed (Vms) is not the same as Best Glide Speed (Vg). Vms will give you more time in the air but you will achieve the highest glide ratio and cover more distance at Vg.
This is a great question for Destin at Smarter Every Day.
#smartereveryday
Manny Pandya Yes I totally agree
#smartereveryday
Something could be rigged using an RC propeller on a shaft and dragging it through water with a force gauge on the end of it (like a fish scale, perhaps). Then measure the resistance with the prop idling versus stopped.
That guy is a moron.
Idle the airplane on the ground, take a “thrust test” with a windometer. Whatever speed your propeller pushes air at idle speed will show you at what speed your specific prop generates drag instead of thrust.
This method is a bit too conservative. You are correct that a prop will generate thrust at any glide-speed below this "backwash wind speed". However, it will also generate lift for glide-speeds notably above this speed -- until the angle-of-attack the prop experiences exceeds the critical AoA and the prop stalls.
A good analogy for this is an airplane wing losing altitude but still generating lift as long as it doesn't stall. It is the angle-of-attack of the air which causes the prop to stall, not merely being pushed through the air slightly faster than it's "backwash wind speed". The speed at which this occurs is dependent on the RPM, prop pitch, and airfoil shape. (and of course the prop airfoil is not uniform, so the stall isn't uniform either)
As usual, great content with a clear and concise direction. My friend was telling me that he was looking into buying a Kitfox yesterday, I told him to check out your videos. He told me he’s already watched them all! Lol, I hope Kitfox is thinking about a partial sponsorship for you, as I am also looking harder at the light sport aircraft thanks to your videos. Talk about putting the fun back in aviation. Great job!
Trent should get a commission
I think they did help him a lot with the latest engine upgrade and I know they made him a special carbon fiber cowl. They seem to be a genuinely great company.
This makes absolute sense. The angle of attack on a moving prop is going to be more in line with the chord then on a stopped prop.
Therefore, more drag on a stationary prop.....end of discussion !
This type of real world testing with light aircraft is so important. You guys are getting it right. My hat is off to you.
Better put it back on, that's one big bald spot!!
I'll see myself out...
"Props" to everyone in this video and @Trent Palmer for fearlessly discussing this topic, for the sake of proving it, confirming it, discussing it, and not being afraid of being wrong. This is about "really knowing" which is invaluable for so many people flying so many different STOL planes. Outstanding.
I had an engine out in a PA-20 at 1,000'agl. That thing came down like a streamlined crowbar! Glide is definitely a little better with an engine at idle
I had the same thing happen in a PA 20 while I was towing banners and you're not kidding. I couldn't drop that rag fast enough and I ended up wadding the thing up trying to land in the salt marsh. But luckily I was OK and even though it flipped over the damage was minimal. It happened like it was in slow motion .
n4478j: streamlined crow bar is probably faster than a simonized safe? For the youngsters,just to clarify, we used to use Simonize wax on our cars in the old days.
Jesus, that would be like trying to glide with a parachute attached to your tail! I hope you at least were able to jettison the banner?
@@jameshoiby I was but when the crank broke out of nowhere at 1200 agl it felt like it took forever. I was flying low and slow as it was. But when it quit,it was like hitting the brakes and the stall horn was blaring before my hand got off the release handle. She got all mushy and dropped a wing before I knew it. So it was off to the races before I knew why it quit.
I used to get annoyed when people would say "just fly the plane" but it's what saved my bacon. Well that and I've always subconsciously thought about outs to land in a emergency. Thankfully there's tons of open marshes next to where we towed. The downside is its soft,nasty,stinky mud. But it dug in and went over pretty easy so its still a landing in my book and my only injury was a nasty bruise from getting out upside down in a hurry lol.
"Streamlined crowbar." that image cracked me up. Glad you got that thing on the ground safe, though.
Good point on it being quiet during engine out... probably a good thing to practice (vs just going to idle) so you don't freak out if it really happens.
Try pushing a corkSCREW staight into a cork without spinning it........what part of a screw don't people understand?
Most comments are from basement dwellers that have never screwed anything before
@@slickjimmy76 spicy lol
I see, but what is the difference between a canary?
Yeah. Cork is a solid object. The air isn’t.
Once the prop stops and the blades stall there is less drag. That’s why one of the tricks with a runaway prop on long range bombers and airliners was to cut the oil off and let the engine seize. Drag of a stopped prop is a fraction of one that is idling or windmilling.
@@calvinnickel9995 impossible!
Thank you for risking your planes to do this experiment! I've practice many practice emergency landings before, but always with an idle engine, my CFI said they would never actual turn off the engine, because if we cannot turn on the engine again for some reason that would be a real embarrassing day for us.
What a GREAT real world application and test. Great for ALL pilots not just new ones. As you see here, everyone was learning. Thanks guys love your videos!
Good video. There are so many aspects of flying, it's nice to see that you can take a discussion and turn it into a real demonstration.
I agree that an idling engine is producing thrust, versus a dead engine, with or without a turning prop.
As an aviation and history fan i have an interesting fact for y'all. The germans knew this in ww2. And they wanted to be able to glide as far back to their territory as possible if their engine was shot or died. To insure best glide they installed spring loaded pins right behind the prop of their planes that the pilot could pop out to stop the prop from windmilling and causing drag. (Doubt it was nessicary a v10 or v12 is probably pretty hard to turn over) but none the less they definitely paid attention to tiny details.
Have a good day everyone, fly safe.
This phenomenon can be explained relatively simply.
In general, for a fixed-pitch propeller if the airspeed of the aircraft is GREATER than the pitch speed of the propeller (propeller pitch multiplied by rpm) then drag will be created by the prop.
I've done many engine idling and engine off comparisons in my Rans. Idling it will go on and on and on, but when I shut off the engine it would slow down tremendously. I will say this that when the prop stopped windmilling it was noticeably that the airspeed picked up slightly. The difference is when the engine is actually not running. Windmilling is drag. No notes on this just hundreds of dead stick practice landing all the way to the airport.
I trust Teddy and agree!
in 2002 towards my flying hours in a piper cub, when I climbed in the complicated way that is done, I broke the fuel tube under the instrument panel with my foot, the engine was cold and turned off by luck, then I received help from the mechanics, it was an accident with luck. Excellent video !
Hey guys I just have to chime in on this one as a guy who survived an unplanned engine out. I was a 75ish hour pilot. I had rented a Cessna 150 just like the one I had done most of my training in to build some long xcountry time. Long story short. The engine died at pattern altitude as I was over flying midfield for a left downwind. In my head I was startled that it stopped then oh well no biggy, I have practiced this how many times with the Instructor. I very quickly realized the difference between an idling propeller and a windmilling propeller. I thought for sure I was going to park it in the roof of some shed just outside the airport fence. I landed on the runway about 30 degrees off runway heading. I'm sure angels helped me do what I did. The only damage after all said and done, outside of the engine itself, was the tail tie down ring.
I was really shocked how much shorter my glide was. I now try to warn other new pilots about that.
A couple days after the incident I got to talk with one of the test pilots from Cessna. He said the decision to "stop" the prop or to let it windmill has to do with altitude above the "runway". You have to be high enough for the benefit to out way the altitude loss You WILL experience in trying to stop the prop. Anyway that was my experience.
This was awesome thanks Trent!!! Just remember to kill the mixture, fuel selector and electronics before touchdown in a real life scenario to minimize fire potential!
Fantastic video, one last point for you to consider in the spirit of your initial debate, when the prop stops for real and WILL NOT restart - does time subsequently pass faster or slower?
Trent, is your left side wheel strut fabric buffetting or is it an optical illusion? It appeared when you were under power but not during engine off. Might have been prop wash?
Depends on if you have a runway below you or not
Slower.
It depends on whether the observer on the ground is a friend or an enemy.
Well, that depends. Are we talking "Real Time" here or "Perceived Time" while your "hyper-sense" panicy "oh crap I'm gonna die!!" sense of time kicks in. I believe stress is a very effect multiplier.
I must say it’s very refreshing to see you guys as friends and so passionately enjoying what you do.
I made it to solo in my lessons many years ago, can’t fly now but I so enjoy watching your adventures!
It would be interesting to do an interview with an engineer at Hartzel or NASA regarding this question
Don as I was saying in my comment, I would love to see this sussed out in a fluid dynamics water dye tank. Anyone here work at NASA Ames, and could get a few free cycles with the fluid tank? ? This is what I love abort aviation and aviators- you never stop learning, we are indeed, a band of curious monkeys! . Happy flying!
Look into your flight training manuals where the prop function is explained. No engineers necessary. Common sense isn't common anymore.
SmarterEveryDay?
Agree. Common sense is a misnomer. Uncommon sense is more accurate.
Correct, Bill Hamilton. Even if you want to go further into actual engineering texts, the effects are well known and don't need any further wind tunnel tests at Ames or whatever. It's all well documented already.
Trent's tests did show that it is wrong to always assume the idle glide is worse than a stopped prop.
- It is also wrong to assume that idle glide is always better than a stopped prop.
It depends on the airplane, the pitch of the prop and the glide speed.
Great point on elevator authority. We were trained to think airspeed, which is true, but the airspeed behind the spinning prop is different than the pitot measures.
You must calculate the pitch speed 1st. Take the pitch of the prop times the RPM to get the pitch speed, which is a theoretical distance the prop would "screw" into the air, per revolution. If the aircraft is going faster than the pitch speed, then there will be a drag induced, slowing your airspeed. If the prop pitch speed is more that the actual aircraft speed, then there will be a thrust component added, increasing airspeed. A windmilling prop creates the most drag. The difference in drag between an idling engine, and a stopped prop is much closer to each other, and more difficult to predict. I would think that an idling prop would be just like a car coasting down a hill in 1st gear, producing a lot of drag, but it looks like you guys are proving me wrong. Interesting thoughts to ponder.
"I would think that an idling prop would be just like a car coasting down a hill in 1st gear, producing a lot of drag" I think you are correct except that these are all fixed pitch props -- like a scooter or dirt bike with only one gear. On a constant-speed prop the idle setting at full fine(like first gear in your analogy) is very much a drag force.
This was my thinking too - that for a prop at idle it's a matter of effective pitch speed vs airspeed. And whereas the fixed pitch prop (at a given idle RPM) will generate drag when airspeed is greater than pitch speed, and thrust when airspeed is less than pitch speed, a stopped propeller will generate no drag at zero airspeed, with drag increasing quadratically as airspeed increases.
Boyd , that's exactly what I was trying to say, but couldn't be so concise. Thanks
You are so right. It is very easy to calculate.
I don't even fly and intuitively knew this.
Great video - yep, I'd agree - the tale probably comes from windmilling Vs idling, in engine-out twin training the windmilling prop and drag is noticeable until feathered
Dang, I'm early. Great video Trent, as a flight student currently working on my commercial license this video will definitely bring up some great conversations with my CFII.
If you want to have some fun building time in a tail wheel, look into pulling banners. I did it for 3csummers and had a blast. Plus it'll really help you to be a better pilot in my opinion. Diving down to pick up is a blast but it does get a little boring after that. But that's a little price to pay for spending summers at the beach having a blast getting hours. If you get a chance look IP Paramount air service, the one kid I flew with has some videos on here.
Good luck
I'm almost finished with my tailwheel endorsement, so I'll have to give that a look!
@@199tornado its a ton of fun and you get a lot of time. If I wasn't married I'd probably still be doing it ; -) Anyway good luck
Great piece!
Was forced into my first simulated engine out on return to base by my cfi the other day in 7eca citab!
Was a great experience, loved the pressure, everyone should perfect it and practice it often
Keep up the great episodes!
Cheers!
That was a great video!!! Good reminder of a lot of things that you hardly ever think about as a corporate pilot in daily flight ops. It’d be really cool if you guys could come up with more ideas you could myth bust. 👍
Really good question and it's a question that instructors need to touch upon with their students. The students need to be aware that actual engine out situations will result in a shorter glide ratio than the simulated engine out situations that they practice. Excellent video!
That's not even a question for anyone who has had an actual engine failure. It is very noticeably more drag stopped...
Great job on getting everyone to think about this. We have all trained with engine out scenarios. The real life engine failure is the real deal and no turning back. One must always be prepared, even if it is just running the scenario through your mind, as most of us are doing now. Great job on getting us to think!
The worst: A feathered prop windmilling backwards. Fun times.
This is hands down the best channel on youtube right now. Please! Don't stop filming content. You can easily be the best "UA-camr" if you keep this up.
Haha. I don’t know about that but thanks man! I’ll keep making them 👍🏻👍🏻
This is one of the great pilot debates of all time, even in jets. Military pilots too often deal with flame-outs, and an air start is usually about the best you can hope for, prop or jet. My personal experience tells me the windmilling prop is the least desirable situation, while the prop producing partial thrust is best. It's such a dynamic situation with so many variables that I'm not sure there is a one size fits all answer. Testing like you did is highly desirable, and kudos to you guys for doing that.
I guess I have a bit more experience, then. I'm a retired Air Force colonel, having flown fighters for 27 years, then going into charter aviation for a total of over 20,000 hours. That does NOT mean I know everything, by any stretch of the imagination, but I have learned a couple of things over the years. The most critical thing in a loss of power is to keep your cool and never quit flying the plane. The rest will work itself out. And yes, I have experienced engine failure, though not too often, thank goodness.
I suspect the major prop manufacturers have performed wind tunnel tests on the various windmilling/seized scenarios. Personally, I think the windmilling prop on a dead engine is worse than seized prop. I could be wrong. As for the jet over water you mention, I'd probably shut down one engine. The plane will continue to fly and burn a lot less fuel.
I refer to glide. In any normally maintained plane, the battery is probably going to be sufficient for minimum needed electronics, and if you're VFR, you don't really need any gauge except airspeed. Angle of Attack would be nice, but most civilian planes don't have one. Neither is dependent on vacuum or electricity. Perhaps I should say, the ones I'm familiar with.
Great video, thanks Trent. My instructor back in 1996 in the UK told me that in reality with a stopped engine expect to descend faster even at best glide and to be a little faster during the flare to compensate for less airflow over the elevator. I’m also a glider pilot so I am always checking for landing spots as part of my cruise checks. You have a great channel.
Some thrust is better than no thrust.
An idle engine does not necessarily produce thrust at flying speed. It depends on the pitch of the prop and the speed of the glide. A flat pitch prop will produce more drag at a higher rpm than a higher pitch prop.
These are relatively light, slow flying planes. Not a surprise that they all get a boost at idle. Heavier airplanes or flatter pitch props could have the opposite results.
Thats what she said..... sorry had to go there
John Goscinski Its less drag though. Its a simple physics problem. These things are known quantities.
I think it is in these cases because best glide is so slow. Presumably there is a speed at which the airflow would be trying to turn the engine so much faster than it was able to run at idle that it would have the windmilling effect. IF the throttles are back to idle and the airflow keeps spinning the engine faster, then the engine will also become less efficient as it will be able to draw less and less mixture through the same throttle setting as the rpm's increase, and at some point it will then stop firing, and it becomes a windmill.
I honestly have no idea at what speeds that's likely to happen for each engine, but I feel fairly confident saying it's far, far outside of best glide given that you can pull an engine back to idle at cruise and not risk it staling.
True. I believe folks are looking at this issue from the wrong direction. A propeller has "X" amount of surface area producing drag, whether turning or not. What over comes that drag is thrust, and an idling engine produces some amount of thrust regardless of any propeller drag. The aircraft drag does not change based on the engine or propeller turning, it changes based on the thrust produced. Lift versus gravity; thrust versus drag--the basics of flight.
I like the tech nerdy video, the more people can talk about things like this makes everyone a safer pilot while having fun
I was expecting you to hesitate when you restarted the prop because you thought about yelling clear prop at 6,000ft.
Now that would have been a real side splitter.
Talked about missed opportunity!!!
Haha
Well, you have to give any passing birds a sporting chance to get out of the way, after all!
LOL!!!
That may be true for fixed pitch props, but for constant speed props on Idle you have it on fine pitch, which would create more drag than a stopped propeller which would be feathered. That's why we do the PFL on a low power setting with the PC-9M.
ok, I had to watch this one again. what if you had a anemometer/wind speed indicator you could put out the window and read the wind speed, with an idle, and with engine stopped. if you don't have one, let me know. I could sent you mine. mike
Excellent point about an idling engine increasing control authority!
I think the root of this is people confusing the windmilling prop with an idling prop. Then the fish story continues to grow.
Exactly. If you stop the engine, but the prop keeps windmilling, that energy to turn the engine around has to come from somewhere. As a result you don't glide as far as with the prop stopped. When idling, the engine supplies this power (and perhaps a bit of thrust too).
But the energy is still going to be absorbed by the prop and converted into torque, even if it's not windmilling (assuming an un-feathered prop) and that torque will either act on the airframe or on the rotating components of the engine. It would seem to me that, if your prop is windmilling, that simply means that the prop is converting enough energy into torque that it's able to overcome the friction of the engine, causing it to rotate. If your engine is seized, but the prop is absorbing enough energy that it would normally be causing the engine to rotate, that stationary propeller is probably creating more drag than it would if it were windmilling.
idontcare80 not sure about that. Think about an autogiro or a sycamore seed pod. If the ‘blades’ of either are spinning they create a load of drag, if they are stationary they drop like a rock. Maybe oversimplified and a little off the mark but goes some way towards the reasoning.
But that assumes that lift is also being created, which it's not in the case with a windmilling propeller.
That's not how energy in physics work: if a force is trying to rotate the propeller, but the propeller is standing still, no energy is spent. Of course there's friction in the airflow and stuff, but no energy goes into rotating the propeller.
It is apparently a well known fact that a windmilling propeller creates more drag than a stopped propeller (assuming it is the airflow that drives the propeller around). My energy view of it was just one way to understand why. Another way to understand it is that the stopped propeller blade gets an angle of attack of 90 degrees with the airflow, so the prop blade is stalled and creates little drag. The windmilling propeller has a much shallower angle of attack, so it is able to create more drag (caused by the negative lift).
I want to say - as a PPL - thank you for this video - there is zero doubt in my mind that this collaborative, thought provocative, narrative of a few pilots that wanted to challenge the questions that we all face and ask ourselves, especially when flying family - whats my glide slope - how far can I go - when do we commit to off airport alternatives - bottom line - this simple youtube video will save lives -- period.
Wonderful lesson.
Oh this is a great video and a great topic discussed over and over again. It is very important to know how your plane "behaves" with idled engine and with stopped engine. Even so, choosing the right spot to land in an engine failure means to choose the one that you 100% can get to it in both scenarios. Afterwards it depends on the pilot skills to have the best energy management to get there using a combination of techniques learnt and exercised a lot ( eq: slipping the plane , getting to the best gliding ration , giving more speed/energy in case the terrain is uphill and so on ) . So independent if there is more drag or not , it really depends on what are the skill the pilot has to manage this properly. More over , one of the most important difference is how much authority you have on your elevator when you flare you plane. Not having the air flow generated by the idle engine is a very big factor that needs to have a lot of attention (eq: in a taildragger you might end up having a main wheel landing instead of three points if you are not giving enough extra speed to get your plane in a three point position from its own energy resources instead of using your engine ). The risk is that untrained pilots will stall to plane to high resulting into a big bounce ( when it comes to taildragger planes) or striking the nose wheel of nose-wheeler. Bottom line is that I THINK that the most important things are NOT to focus if there is more or less drag between dead stick or idle prop. The most important things are: choosing the right terrain and learn how to land the damn airplane with no extra airflow on your elevator.
In my 53 years of being a licensed pilot I always suspected that, but never once questioned what I was taught. Very interesting.
Most schools/insurance companies prohibit intentionally shutting off the engine in flight. I will definitely have my students watch this!
I love the notes on the power off approach; adding another reason to aim for the 1000’ mark on a power off 180! I’m also sure many don’t think of how the prop adds to elevator and rudder effectiveness. All around awesome video!!!! Thanks for the great work!
Lance Jackson
Likely school policy. I’ve never seen language in an insurance policy restricting this.
notification squad here... Good talks... and having you guys not just talking but to testing different scenarios.
?
YOU GUYS ROCK! I always have gone with a philosophy horses and power. If horses are being applied, IE the engine is running even a half horse you will go farther. Great video!
I only subscribe to channels that are willing to present both sides of the argument and then encourage their viewers to go see the results for themselves.
You just earned my second subscription, Trent :-p lol
Geoff Ginther I take it you don't subscribe to many flat Earth channels then. He he...
Definitely not! lol
Great video, and a great topic! The comment that (I think) Mark made early on about idle thrust being relative to airspeed (and thus apparent wind) seems spot on and may be a factor for faster planes.
That’s why I fly gliders. No propeller no prob :)
Yep ... Every landing is a forced landing ... no big deal..
If you can fly a glider you can fly about anything with wings. Love my 1-26
Hell yes. I dont fear the forced landings in training or re-currency. I love my 2-33!
Hugo Girod You still have to get towed so it applies to you until you reach altitude and release that tow line.
😆👍
not to bother you or break your idea, but that's the case with every aircraft going up
We used to test this theory flying RC pattern ships, racers and such. YES! A idling, fixed pitch prop creates drag and, without this drag, planes such as the G B Racer or P-51 would be almost impossible to land. Real men fly tail draggers! Don't forget that loss of altitude and drag are not the same. Yes, a stopped prop will cause your loss of altitude due to a complete loss of thrust but when I cut the throttle on my G B I could land, shut that that engine down on a G B and you're flying a brick looking for a spot to crash. Awesome channel.
That 13 seconds is around 1300 feet travailed forward per 1000 feet of altitude.
Ryan Jones, travail: def. pain, anguish, or suffering resulting from mental or physical hardship. The perfect typo in talking about a dead stick landing.
Could you explain the math please
Trent said his best glide is 60 so that is 101 feet per second so 101 FPS times 13S is 1313 feet.
Tried 3 different descends, all straight vertical down towards the earth with my rc shockflyer.
a) 0%throttle, esc brake off
b) 0%throttle, esc brake on
c) 4%throttle, esc brake on
a) was in the MIDDLE, the wind kept the motor spinning pretty fast, faster than c)
b)was the FASTEST descend, the esc forces the motor to spin at 0% throttle, so a stopped motor is definitely the least amount of drag.
c) was the slowest, because the esc forces the motor to spin at 4% throttle, no matter if the prop wants to spin faster or slower, so it acts as an AIRBRAKE
Charly UAV best and cheapest explanation on here....well done Charly!!
you should post that in the main ot as just a reply....cowboy is wrong wrong wrong...all Turbines use it as an air brake for float landing approaches. ..physics don't lie.....great job... any video would be awesome if you could recreate that!!!
I was fortunate enough to have a Flight instructor to allow me to execute a dead stick landing with the propeller stopped to show me the difference. I am glad that he did because I discovered that that windmilling propeller that results from simply pulling the power to idle to simulate a failed engine is actually producing a fair amount of thrust that helps make the landing smoother. Without the windmilling propeller the only air going over the control surfaces is relative wind. What that meant for me is that I had to keep the glide speed up until I was ready to flare and touch down. The first time that I made a dead stick landing was not my smoothest landing but having learned I made smoother future dead stick landings.
Have Mike Patey try it with Draco with the prop in beta.
Now that would be just "plane" weird! LoL
Very common practice in turbines. Its the same as being feathered. Full windmill even with power idle the drag is horrific.
A windmilling prop is a different animal than an idling prop! With my Supercub on floats I routinely practised dead stick landings. I quickly found that after pulling mixture and slowing up a bit so the prop would stop, glide ratio improved. Believe me with an 82x41 Borer prop windmilling around, a Cub on floats has a pretty steep glide ratio!
If you have ever hand-propped a Cub, then you know that it takes energy to turn the thing. Think about where that energy comes from if the engine can't turn itself inflight.
Another question would be if you pitched up to stop the prop, would you lose more due to regaining airspeed versus letting the prop just windmill? I know in my Cessna 150 you have to slow it down quite a bit to stop the prop.
You take out more lift from the wings when you pull up to slow down. But thats a really good question because you will glide way worse close to stall speed than at best glide. But the again best glide are much slower in a lightly loaded plane. When I took my MAX TOW lesson I was shocked by how much better the glide ratio was (with idling engine) compared to when I was alone or with just an instructor. I had a friend in the back seat so balance was also more on the tail heavy side.
It would also probably be distracting to make the prop stop instead of just deciding where to land.
If you're way up high it makes sense to slow the plane and stop the prop, then speed up to best glide speed, plenty of time to make up the difference. But if you're close to the ground, you might lose more by slowing down than you'd regain by the improved glide before you reach the ground.
Have been flying RC airplanes for YEARS and what you just said was spot on 👌🏼 When my motor electric motor locks up it glides muuuch further than when I just lose motor power and it keeps spinning (windmilling)
Great discussion! I stopped the vid, because I want to see how this plays out - A CFI will pull the throttle and tell you "Engine out" But as Mike/Mark???? LoL says, is the glide profile accurate vs a stationary prop?. I think the most definitive way would be to test this in a NASA (Or make one yourself) water flow dye tank, where you have streams of UV dye injected into the water. That would remove all variables, from relative wind,, gusts, etc, thus creating a perfect test platform. In a fluid dynamics test, which this is, the more variables that can be removed the better. When I was in college, I drove prof's nuts because I wanted proof if at all possible. Math is pure, theoretical physics is more or less pure,, (practical) physics is messy . -- OK! Back to the video - thanks guys!
At Bonanza Pilot Training they lower the gear to (a lot of) create drag, then turn the idle up just enough to create the amount of thrust that will have the plane decending at the same rate it would with a dead engine and windmilling prop.
This simulates an engine-out/gear-up approach.
Excellent video and timely for me. I just finished a Zenith CH750 STOL and am writing the flight test plan while waiting for the FAA to certify the kit for flight. Have survived several engine outs long ago, all in 2-cycle ultralights and most due to fuel issues, so I know that after things get silent, it’s all about having the field already selected (every five minutes) and using good, conservative Energy Management (two words I’m surprised that you did not use). Anyway I plan to do several engine out tests at idle and finish with deadstick landing once I know how this ship will glide, slip and flare inside and out. I may be flying in modern 4-cycle Avgas-fueled glass-paneled comfort, but it’s all eventually stick ‘n rudder. You must be calm and prepared, and experience IS the best teacher.
Anyone that says that an engine at idle doesn't produce thrust has never had to disconnect a GPU from a 400 series Cessna. My hat was 50 yards away in the ditch off the end of the ramp.
An idle engine does not necessarily produce thrust at flying speed. The fact that it does on the ground at zero airspeed does not mean a thing in the air.
If the engine is consuming fuel, it is producing thrust. Think about it this way, if you turned the engine off while gliding, would the RPM increase or decrease? On both jets and pistons, the rpm will decrease if you cut fuel. Therefore, the engine MUST have been producing more net thrust (less drag) while idling than when off.
I think it's better to think of an idle engine as producing its "minimum thrust," which is not the same as "zero thrust." Whether that thrust is usable or not will depend on airspeed. Think of it like this: Thrust is produced by moving more air through the prop disk than would be moving through it if the prop were not there. At higher airspeeds, you need to move more air to generate the same thrust. Since no plane flies at 0 kts, there will always be more thrust at idle on the ground than at idle with airspeed.
Forward speed decreases the angle of attack the prop blades experience. The more speed, the lower the angle of attack. If you fly fast enough, like in a dive, you will create drag with a prop even at full power. That's because at some speed, the effective angle of attack on the prop drops to zero. At idle power, you don't have to be going that fast for the angle of attack to drop to zero lift, and the engine isn't developing enough power for the prop to compensate by turning faster .goo.gl/images/kzJEHK
That is completely different for a jet. The jet increases the speed of the air so much greater than a prop does, relatively small changes in airspeed do not affect thrust as much, and can often be considered constant over a range of speeds.
But at any speed, a moving propeller is transferring energy to moving the engine that would otherwise be added to the drag of the prop.
Trent and friends... you guys are my hero’s. You guys rock!!!
You need a wind tunnel.
Give the Pateys 5 mins they'll reinvent a wind tunnel 10x better.
Not really because it's constant mathematically measurable wit basic of fluid dynamic equations, but win tunnel would revealed a more constant average numbers , and I am certain it would prove the math right , no disc bullshit effect that is a optic effect observed, but no scientific FAC behind.
Math and science never lie
@Brian Foote no pitch is constant and engine is at idle , the very important factor is air density and air speed , it will be a head win on a glide slope , and I used a common pitch and no pitch and same result not a factor what so ever till rpm is at 60 RPM or lower
@Brian Foote well the question was is a motor at idle ,therefore the fix pitch props spinning at 800 Rpm create drag , and the answer is no it create more thrust no matter you glide slope head win , but if you have something different question I'll be happy to answer it the best of my knowledge.
>> face palm
I absolutely love this! You guys really are making people want to question their flying abilities and then go out and test them and learn more. My next flight with an instructor will include a full stop landing with engine out.
From my experience with RC planes stopped props tend to cause less drag. Whenever you want to land short on planes without flaps, run the prop as slow as possible. Just my RC experience.
Plenty of the experience for sure, my giant Stinger with a stopped prop is a tough one to stop when trying to line up for a dead stick landing versus the motor at idle. The Drak kind reverses that thought and think of it like a jet that will come down rather quickly.
right, you cannot scale air density to the weight of the model
I like watching your videos. I'm not a pilot and only got to ride in a small plane once and that was with a guy who was probably the oldest pilot in Nebraska at the time. He started out flying Curtiss Jennies. We took off, flew around the airport and landed. A short but exciting flight. My door kept trying to pop open and when he pitched the nose almost straight down, to get a look at the runway, that was a thrill.
I've always wanted to fly since I was a kid back in the 60's. I used to have dreams about it. One of the first books I bought and read was called Iron Men With Wooden Wings. I read it many times. I used to draw biplanes and build model airplane kits all the time. But my life went in a different direction. Watching your videos and the ones about the Draco make me feel like I'm almost there. Thank you for the dreams.
Great video but your title is horrible. As a full time flight instructor for over 15 years, I cringe when I see titles like this and honestly am irritated by them. But I am also well aware that there are a lot of flight instructors out there that do not train on the fundamentals of topics like this one. A student should never be taught to judge glide based only on numbers, but should be taught most importantly to be looking outside at what the actual conditions are and what the glide is doing based on outside references, and how to adjust accordingly to whatever the conditions are. If you watch outside at what your glide is doing and make your judgements based on those outside references, it really shouldn't matter whether the engine is at idle, windmilling or completely stopped, or what your descent rate is. Unfortunately there is a huge lack of training on subjects like this, which I know is where your title comes from!!! Most flight schools and insurance companies will not allow training to be done by shutting the engine (single engine airplane) off, so we train the best we can. But a good instructor will teach students that there is a difference in glide and descent rates based on things like prop condition (as in this video), relative wind direction, advection conditions and available landing locations. Thank you for doing this video, I will use it with my students to show them what those conditions look like since we are not able to do it in most of our training airplanes. Great video, just wish you would have chosen a different title.
Send all your students to the local glider school for that practice. You get all the engine-off time and forced landing practice you can handle. Along the way, you'll also get good spin training etc, typically at a much cheaper rate than power aircraft.
He didn't make the title that to call out instructors. He did it to attract more viewers. He was successful with it, but I agree. Initially I judged this video skeptically, but he is right. Low speed idling prop is producing thrust. In usaf pilot training, if we were at full idle (T-6 Texan II with a PT-6 Turboprop) we would actually have more drag and to simulate engine out, we would actually increase power ever-so-slightly which simulated a feathered prop closer.
An engine out means one thing, gravity is King. The only math involved is how much seat cushion does your hole actually suck up.
F#ck insurance, I shut the motor off anyway. I have learned to fly in gliders 1st so, engine off in a plane is nothing sacred, risky or dangerouse.
@@airgliderz Lol, obviously you're not scared of dangerous things, you literally don't know how to spell dangerous. XD
Awesome awesome video.
This/Your content is cutting edge. You should consider making a longer doc style video about bush flying or something around aviation.
These videos have rekindled my love of flight. You’re doing a great thing.
Go and jump in a motor glider and set yourself up at best L/D and idle then turn the engine off and see what happens... you will pitch down to maintain the same speed and best L/D then go and feather the prop and watch the nose come up to keep the same L/D. You will always be flying for best L/D in an emergency situation. Just ask any motor glider pilot. Why don't you make a polar curve for prop idle and prop stopped? That will solve it.
That's right. There is no use in my mind of trying to extend a glide of any type of aircraft if the airspeed is below best L/D - best L/D is exactly what it says. Trent and Co need to take this into consideration. Another thing; glide the aircraft at say 60 kts theoretically without a prop at all and then theoretically replace it dead. It will be like an airbrake on a glider; idle in my mind will reduce some drag.
It makes quite a reasonable difference. Idle is thrust and when you stop the engine you need to drop the nose to maintain the best L/D speed therefore there is more drag from a stopped engine. It was adding a reasonable amount of thrust at idle otherwise you wouldn't need to pitch down and if and idling engine was infact higher in drag you would be pulling up the nose to maintain airspeed. A fully stopped prop is pretty draggy and once you feather it you will noticeably raise the nose again to keep best L/D. Therefore an engine at idle doesn't truly represent a true dead stick landings decent rate and at idle has a better glide angle than stopped engine.
Seems like this is a great demonstration for aircraft designed to fly at much slower speeds and showing the contrast between the two prop conditions. So many different aircraft with different configurations like those that can’t fly if the motor is off due to drag and lift compared to those that were designed to shut the motor off and glide. Even my rc glider with the motor windmilling is the same as popping the spoiler up. Could turn it into a 10 part miniseries. Keep the videos coming as i enjoy every minute of it.
Man Mike look like Bruce Willis lol
Hesitation is the end preparation is your friend. Great video. This was a good conversation follow up and test. Most people have know idea until it happens to them.
With model airplanes, it's completely different. An actual deadstick is completely different from simulated deadstick. An idling prop on a model plane does act like a massive airbrake. I've seen many pilots who practiced simulated deadsticks no problem, end up way overshooting the runway during an actual deadstick because it glides to much farther / faster. Sometimes to the point they crash into the fence at the end. With electric motors, and their adjustable braking, you absolutely don't want the prop to stop turning when adjusting. For aerobatics it's common to setup the prop brake to slow your downlines. But if the prop brake is too strong, the prop actually stops, and your downlines get way way faster. Massive difference. But this is purely with models. Much lighter relative to scale ratio, much bigger prop relative, and much higher power to weight ratio.
This guy knows whats up. I fly pattern which is a specific aerobatic style one of the properties of which is that you want the plane to fly the same speed the whole time. No matter if it is pointed straight up or straight down. I use a long, low pitch prop to give a lot of low end thrust under power and create a lot of drag at idle. Under dead stick if you point it straight down it will come down a LOT faster than at idle. At idle on a down line, you can actually hear the air turbulance breaking around the prop. Also I have to land with just a little bit of power or it gets too slow which is not a problem deadstick. The difference in results I think has to do with the difference between pitch speed at idle and stall speed of the airframe. If your idle pitch speed is close to or above stall speed, then an idling motor is better. If your idle pitch speed is WAY below stall speed, then stopped prop is better.
EXCELLENT. Thank you for talking about this, and putting it to the TEST! I really love you all and I really respect what you do. I've been following you, Trent, for some time now, not too long after I started following Mike and Draco. I am a student pilot at the moment. I will be sharing this video with my ground school and both of my instructors. This is excellent knowledge, and a great test. I'm not sure they'll allow us to try this test in the school's 172s, but it is very valuable even to simply consider and be ready to expect different dynamics with an actual engine out and a non-rotating propeller.
Oh GOSH, by the way. I realized, I have to give credit where credit is due. I realized, Trent, I discovered you and Draco at the same time, thanks to an interview you did with Mike at some event!!! (It was your Meet Draco The MOST BADASS MONSTER BUSH PLANE EVER video!!!)
Thanks for your great videos and doing everything you do to get people excited about aviation.
This does does not apply to me as my Learjet lacks a prop.
That is nice of you to let everyone know how stinking rich you are. Wanna take us for a ride? Id offer to pay fuel....but I don't have that much money.
And what is the residual thrust from your engines? Hmm? I saw a Bombardier Global 6000 taxiing at Oakland and using one thrust reverser at idle just to stop them cooking the brakes. One of my friends flies Gulfstreams out of there and says it is quite common. Here's a youtube video of one doing it. So which Lear huh? Most people who own jets know enough about them to throw in the model number when talking about them? There's a world of difference between different Lears.
ua-cam.com/video/DYc_gCeMMBo/v-deo.html
yeah you do. They are called fan blades and there are 12 times as many of them, plus compressor blades and vanes. it’s probably worse for you
If you think that this doesn't apply to jets, you're fooling yourself.
Are you sure?!
What a grop of professionals! !! !!! It sure gives you a tremendous amount of confidence flying with such intelligent pilots. GREAT video.
Idle and wind milling are not the same thing.
Yes, I clarify that a few different times
Yes, everybody knows that.
And of course low down just fly the plane and don't worry about it.
Trent. Thanks for another excellent video. Maybe stand behind your aircraft...at idle...with a handheld airspeed indicator... And see what that says... I don't know what it would mean since the aircraft would be motionless, but I still think it would be interesting to know.
I answered the question : Do pilots idle their engine during final approach? This is my answer . I think it is very relevant to your discussion.
Some very good answers already for the heavier aircraft.
For Light Sport Aircraft (LSA) and especially ultralight aircraft we are taught a different approach. Engine failure is more likely to occur on landing than any other portion of the flight. Consequently we are taught to approach in such a way that we are able to glide to a safe landing from any place in our descent. Unlike heavier aircraft which approach with power and higher than best glide speed.
I'll give you an example.
A Jabiru LSA aircraft has a fixed pitch propeller. The engine idles on the ground at 1000 RPM. It climbs at 3200 RPM. It cruises at about 2800 RPM. Now the interesting part. In flight when you close the throttle the engine idles at 1200 RPM, not 1000. This is because the motion of the aircraft is pushing on the propeller causing it to speed up, just like a windmill. In actual fact at idle RPM, the propeller and engine are acting as a brake and are slowing the aircraft down. So at idle the engine is stopping the aircraft, and at 2800 it is pulling the aircraft, so there must be a particular airspeed and RPM combination in between where the engine and propeller produce zero thrust and have no effect on the aircraft.
Secondly every aircraft has what is called best glide speed. For those interested I'll explain it at the end. For the Jabiru in our example it is about 70knots. And at 70knots the engine and propeller combination of our example Jabiru, will produce zero thrust at 1700 RPM.
Ultralight and LSA pilots are taught to begin their descent at best glide speed and at the zero thrust RPM. So in a Jabiru as I reach the end of the downwind leg I will pull the throttle back to 1700 RPM, and continuously raise the elevator to keep the aircraft flying level as the speed bleeds off. Once the speed reaches best glide speed ( 70knots ) I will stop raising the elevator and I will let the nose lower and begin descending at best glide speed and still 1700 RPM. My aiming point will be somewhere about a third of the way down the runway. Once I am sure that I will reach my aiming point and I am close to the ground, I will extend my flaps and begin to slow the aircraft in preparation for the flare. This will bring my aiming point back towards the runway threshold because we are now below best glide speed. I continue to bring the RPM back to idle just before the flare, then flare, hold off, touch down, and we have landed.
If at any point in the descent the engine decides to go quiet, nothing changes. I just continue my approach as if I still had an engine and land normally.
I actually had this happen once. The engine stopped just as I was applying flaps and I just continued to a normal landing, which I must say was about as perfect as any landing that I have ever done. It's funny how a bit of adrenaline can make you perform better.
Most ultralights do not have flaps so we continue all the way to the flare at best glide speed because we don't have to adjust for the flaps.
Explanation of best glide speed.
Lift and consequently Drag of an aircraft is a function of the square of the velocity. An aircraft produces two kinds of drag. Drag due to the wings producing lift (Induced Drag), and drag due to the friction of the surfaces of the aircraft with the passing air (Parasite Drag).
As an aircraft increases speed, the angle of attack is decreased and consequently the Induced Drag decreases exponentially. This means Induced Drag starts high but rapidly decreases as speed increases until it becomes nearly flat.
As an aircraft increases speed, the friction increases and consequently the Parasite Drag increases exponentially. This means that Parasite Drag starts low and nearly flat but then rapidly increases as speed increases.
Total Drag is the sum of both types of drag added together. Because they are exponential, Total Drag is high at low speed due to the very high Induced Drag, and high at high speed due to the very high Parasite Drag. However Total Drag is relatively low in between due to both Induced and Parasite Drags being relatively low. This speed where Total Drag is lowest is the aircraft’s Best Glide Speed.
I like this video. Reminds me of what we do here... sit around and talk about these sorts of things for hours.
The real value of engine out training is not perfectly judging a glide range but being able to see if the field is made or not. It also builds confidence that it is not impossible. Wind will, of course, throw a spanner in the works.
As a CFI, I completely agree training isn't a perfect representation, but it does not need to be. Many people had real accidents doing actual engine outs because the general skill level and environment to instruct this isn't there, so go for the happy medium. The same with the impossible turn. It can save your bacon in the right circumstance, but it can be a real killer even for highly experienced pilots.
Excellent video. The pilot nerd in me just soaked up all that discussion.
I would think that a stationary prop and a windmilling prop would cause the same amount of 'prop drag'. However, a stationary or windmilling prop also 'spoils' the air behind it. In which case your windmilling prop is spoiling more air and causing less wind resistance on the fuselage. That is to say the stationary prop spoils the air on two sides of the fuselage and the windmilling prop spoils the air all around the fuselage.
Love the videos. Keep 'em coming.
Trent, I think this is one of the best videos you have done yet. I love when people prove/disprove controversial topics with real world examples.
The prop pitch can be used to determine that point at which the prop is either driving or being driven (creating drag). For example, my prop is a 43 pitch. Idle on the ground is about 600 but that's partially loaded so let's estimate unloaded idle rpm at 1000. 43" per revolution gives an unloaded (zero AOA) speed of 40.7 MPH. Slower than that and the engine is pulling air, faster than that and the air is pushing the engine. Now look at a L/D curve and remember that the prop is an airfoil. When it is being driven by the air, it is at a negative AOA and at some point, that airfoil will hit the critical angle and stall. It is still producing "lift" aka drag when stalled, but less than when windmilling. If the engine is switched off, the windmilling prop is using energy to pump air. If the engine is just idling, there is at least some energy added to the equation from burning gasoline, even if the engine is being driven by the air.
Good job on the video. I know these can be harder to make than just a simple vlog but I find them much more engaging.
Don't forget, the propeller blade airfoil is completely stalled when the relative wind is from the top of the airfoil. The stalled, turbulent airflow might create less drag than a rotating blade pushing a non-running engine.
This is a great question. I flew for a parachute club which was 501c so I was legit as a PPL. During checkout the instructor pulled the mixture in the 182 which surprised me. He had been stressing to not shock cool the engine on descent after dumping the jumpers. The main difference I saw was my confusion. I did come a bit short since I was confused but not sure if the physics of flight changed.
Major respect that when Palmer gets heated, he goes straight to science.
Hey Trent,
You’re absolutely right - and I’ve never heard of an instructor saying that an idling engine is ‘worse’ than a dead one - these people need educating.
I haven’t instructed for nearly 30 years, but was a QFI in the U.K. in the eighties - I don’t think the laws of physics have changed substantially in my absence!
...and yes, I have experienced several real life engine failures.
The only time I’ve had better performance with a dead engine, has been when flying turboprops - a dead, feathered engine, will create less drag than a propeller set to fully fine (which we used to use to help get down quickly, by ‘discing’ the prop).
However, single engine pistons do not generally (I’ve never seen one) have the ability to fully feather the prop.
During my upgrade to QFI (what used to be the UK’s higher level of instructor), my own instructor instructor demonstrated the difference quite memorably by pulling the mixture on me from downwind. Despite turning straight for the runway threshold, we only just cleared the lights - simulating the same thing with the engine at idle, we could just about fly a full descending circuit - the difference is that marked.
The RAF taught us a really neat way of making any sort of approach (easier in a low wing a/c) - by basically keeping a constant sight-line angle to the threshold, you’ll always make it - engine on or off. Threshold moves up the canopy, tighten the turn, threshold moving down the canopy - widen it out a little. But then the military don’t bother with rectangular circuits - the turn from downwind to finals is one continuous turn - far more efficient than civvie street.
Great channel BTW!
Fantastic video! I love the technical stuff. I've been wanting to go test my plane to see the difference between what is published best glide and what it actually is with the bigger tires, bigger motor, and VG's. Inspired me to go out and finally figure it out!
I flew a small biplane. Without power, the thing fell out of the sky like a stone. A friend of mine exclaimed, "that thing sure loves the ground..."
I do agree with trent. It depends on the relitive wind at best glide when determing the drag of an idling propeller. But i do think that a stopped propellor will always give you more drag. Unless of coarse you have the option to feather your propellor.
Thanks for doing this, it is an excellent example of what you think you know, unless validated can bite you in the butt pretty quickly. Much safer to shoot for mid field and slip it slightly if you want to increase your sink rate...
Awesome and informative. Thanks guys. Something to tell my instructor next time I go into the wild blue.
This is an awesome video Trent! I would agree with you that idle would help a bit more but I'm sure it depends on the plane. I come from mainly a glider background and one soaring pilot in particular, Dick Johnson did over 100 sailplane evaluations. One thing he mentioned is that it is crucial to preform more than one test of each category since you can hit sink and lift at different times. He also would do his tests early in the morning to try to minimize any thermal disturbances. Awesome videos you're posting man, keep it up!
Very much enjoyed getting to watch the deliberation, and then the actual tests. Very good conclusion given the plane types and conditions.
Awesome guys,I could actually feel it and here it on my 72 inch Warp drive prop at idle add a 50 mile per hour descent simulated engine out with my gyrocopter.with engine out had to make inputs to not exceed the 50mph glide it was definitely noticable.by the way best channel on UA-cam!!.
Trent, nice example and good to see different aircraft participate, as we know they all have different characteristics, can you guys do it again with Mike and Cory’s Wilgas and maybe Kevin’s Cessna to really open this deal up?
With you living through an engine out, you should know. The only Air Plane engines I've ever played with were on a thing we used to call, Snow Planes. They didn't fly but were like cars you drive in the snow that are pushed by a Prop.