Killing engine in flight

[Dan Thomas]

Honest question: while I agree with the mixture cable failure possibly (which is also a possibility if one leans heavily while at altitude), how would doing that raise the risk of plug failure? Seems like they’re still firing despite there being nothing to burn, so that risk doesn’t seem increased. That’s one reason I don’t think turning the mag off is wise - that and, when the spark does resume, the raw gas then getting lit in the exhaust can cause “backfiring”.

A spark alone is not sufficient to clear the oil off a plug. It needs the combustion flame and the hot cylinder head to do that.

Pulling the mixture to simulate engine failure has a different effect on that cable than just leaning. The mix lever hits the stop on the carb, and the cable experiences a momentary yank on it. If that cable is old and worn or corroded, it will eventually fail, usually at idle cutoff time. In the flight school I replaced all the engine controls at engine TBO to avoid that. Before I was responsible for the maintenance, we had a throttle cable failure and two carb heat cable failures, all in flight. Enough of that. A mix cable failure would be a bad deal.

 

[rwellner98]

IMO it's never a good idea to intentionally kill the engine when in flight. even practicing power-off stalls or 180s downwind-to-final the engine is running.

"Never"...

Serious question: Why is it ok in a motor glider, but not ok in a 172?

 

[Llewtrah381]

While I agree with the potential risks the various responses have highlighted, I think there’s a “reasonable” risk/benefit for the right situation. Doing it once - maybe twice - at altitude and within very easy reach of an airport can be a valuable lesson both for how much a non-event it is and for learning the “real” behavior of that plane in a power-off situation (seeing the descent rate, “confirming” best glide, etc.). I personally think the risk is low and the learnings can be helpful.

By contrast, doing it mainly for s#!ts and giggles on a regular basis shifts the equation to more risk than benefit, IMHO.

YMMV

 

[texasclouds]

Whatever you do, please wear a Red-bull T-shirt and film it!

 

[nauga]

"we do it in training, so why not do it to get that noisemaker up front to finally shut up" seems like a really odd comparison. "Trying to teach a lesson" vs "Trying to not harsh my spotify jams" don't seem like equivalent causes.

"We do it in training" and "OMG yer gonna die if you do it" seem equally incongruous.

Nauga,
and some FUD for thought

 

[Lndwarrior]

I did this (pulled mixture) just recently. I discovered that there was significant difference in my descent rate at best glide speed between my engine at idle and my prop windmills. In fact it was much greater. I would not have wanted to experience this for the first time in a real emergency. Thirty years of power-off 180s did not prepare me for landing with a windmilling prop.

I won't return to this post after posting so there won't be any follow up responses from me.

 

[murphey]

Omg man. I’m on here asking for advice and leaning on others knowledge, you’re just being a jerk. Unlike the 90% of the other ppl who replied respectfully.

Have you ever practiced a forced landing? Stall? Spin? As pilots we do things that are inherently risky.

Welcome to POA. Thick skin and sense of humor is a required part of your flight bag.

 

[MauleSkinner]

I did this (pulled mixture) just recently. I discovered that there was significant difference in my descent rate at best glide speed between my engine at idle and my prop windmills. In fact it was much greater. I would not have wanted to experience this for the first time in a real emergency. Thirty years of power-off 180s did not prepare me for landing with a windmilling prop.

I won't return to this post after posting so there won't be any follow up responses from me.

the problem with doing it for those reasons is that if you can:
1. Use an aiming point, and
2. maintain best glide speed, adjusted for weight
it negates any need to know what the glide angle looks like. Engine fails, you lower the nose until you get the proper airspeed or it’s time to flare. If you have enough altitude to get to stabilized glide speed, you start looking at the aiming point. If you’re over a body of crocodile-infested water and need to maximize glide to get to shore, knowing the difference between idle and windmilling isn’t going to make a difference.

if you can’t do 1 and 2 above, it won’t matter, either.

 

[Bob Noel]

"Never"...

Serious question: Why is it ok in a motor glider, but not ok in a 172?

Is the engine in a motor glider designed and tested for regular stop/restarts in the air? I don’t know, but I expect better in-air restart performance from the motor glider than a 172.

 

[Mtns2Skies]

Is the engine in a motor glider designed and tested for regular stop/restarts in the air? I don’t know, but I expect better in-air restart performance from the motor glider than a 172.

Why are you expecting poor in-air restart performance from a 172? Air, spark, fuel, the things it takes to make an engine run. Which of those isn't present when starting an engine in the air?

To others point, in-air restarts are a regular occurrence for multi-engine training.

 

[Dan Thomas]

"Never"...

Serious question: Why is it ok in a motor glider, but not ok in a 172?

Motor gliders (and multis) commonly have feathering props, and they WILL spin that engine while coming out of feather. Fixed and non-feathering CS props, when stopped, have a very high negative angle of attack on their blades, stalling them completely. Not much torque generated there at all.



https://limanovember.aero/post/2021/04/first-time-in-glider/

 

[Capt. Geoffrey Thorpe]

 

[Llewtrah381]

Welcome to POA. Thick skin and sense of humor must be part of your flight bag.

Oh - and, as they say, “opinions are like @$$holes: you’ll find a lot of them on PoA”

 

[Ed Haywood]

I don't see a problem with it, if done with a purpose. Cutting the power to enjoy some peace and quiet is dumb. Cutting the power for training benefit can be justified. Possible benefits include practice trimming to best glide speed, knowing the speed required to stop the prop, calculating actual glide ratio, and measuring altitude loss during a 180 turnback.

Flight training inherently requires balancing risks, since no maneuver is risk free. A good example would be practice stalls. The FAA requires this training, even though there is some risk, because the risk of not knowing what a stall feels like is greater.

Yes there is risk to killing the engine in flight. But there is also risk of encountering a real engine-out situation without a full understanding of how your aircraft handles and performs in that scenario. Risk can be mitigated by a few simple safety measures, such as plenty of altitude for a restart and doing it over a large runway with plenty of room for a comfortable deadstick landing.

In my opinion you could even justify killing the engine and gliding it down to a safe landing on a well-selected runway. Then you would be much better prepared if your engine ever quits on its own. The psychological boost of being able to say "Ok, I've done this before" is significant.

 

[rwellner98]

Is the engine in a motor glider designed and tested for regular stop/restarts in the air? I don’t know, but I expect better in-air restart performance from the motor glider than a 172.

The one I flew behind was a Rotax 912, which is also used in a number of light sports and ultralights, nothing motor glider specific about it.

To others point, in-air restarts are a regular occurrence for multi-engine training.

This is a very good point.

Motor gliders (and multis) commonly have feathering props, and they WILL spin that engine while coming out of feather. Fixed and non-feathering CS props, when stopped, have a very high negative angle of attack on their blades, stalling them completely. Not much torque generated there at all.

I can still use my starter, right?

 

[Llewtrah381]

The one I flew behind was a Rotax 912, which is also used in a number of light sports and ultralights, nothing motor glider specific about it.

Funny - my comments were about my Warrior and its Lycoming. By contrast, whereas my gyro has a 912 and I’m really curious to see how it behaves engine-out, because it doesn’t have a mixture control to shut it off and would mean turning it off with a key, I’m reluctant to do so. And with it having a gearbox, I suspect it would take a pretty high airspeed to keep it windmilling. Logically, given that they use them in motorgliders like yours, it shouldn’t be an issue. Emotionally, I’m not ready to test that…

 

[Llewtrah381]

Duplicate - deleted

 

[Half Fast]

In my opinion you could even justify killing the engine and gliding it down to a safe landing on a well-selected runway. Then you would be much better prepared if your engine ever quits on its own.

Yes, but that carries extra risk. If a go-around becomes necessary on short final (deer on the runway, whatever), you might not be able to restart in time to accomplish it. And who among us hasn’t bounced a landing and needed to shove in the throttle?

Personally, I wouldn’t add the extra risk.

 

[Half Fast]

BTW - remember that if you stop the prop from windmilling, you stop the alternator and the vacuum pump, too. Probably okay, but it should be considered.

 

[Daleandee]

And who among us hasn’t bounced a landing and needed to shove in the throttle?

Maybe you should start a poll ...

 

[Let'sgoflying!]

Omg man. I’m on here asking for advice and leaning on others knowledge, you’re just being a jerk. Unlike the 90% of the other ppl who replied respectfully.

Have you ever practiced a forced landing? Stall? Spin? As pilots we do things that are inherently risky.

Hey, calculated - I see you are upset by my post. No need. No disrespect. I'm not telling you what to do. That's your choice.
You are asking about taking action that can expose you to risk, and I am offering thoughts on why my personal choice is to not do that.

Let me explain some of my history so you can understand why I am 'a jerk'.
About 45 years ago and then again (embarrassingly so) more recently, I was much like you seem to be.
I wanted to experiment, try different things in airplanes that were obviously outside the norm.
I won't mention what, to avoid giving others ideas - but some of the guys here on POA knew and saw (& participated) in the more recent things.
Even before the FAA had their hazardous attitudes I suffered from one of them; invincibility.
Since then, I now have these thoughts which I wrote in the previous post that help guide me away from trouble.
If I ever get a wild hair and think of trying one of these things, I bring my mind around to the ntsb report, my aviation reputation, the effects on others, my insurability and all that - if it goes wrong.
I am not perfect and I may falter again, but I do think there is value in guiding others away from what we learned in the past to be risky things - each subsequent generation of pilots should to have the opportunity to improve upon what the last one was.
I have found that aviation has plenty of traps out, there without me setting my own.

 

[Lowflynjack]

I don't recommend it, but I won't discourage it either! Many years ago, I used to shut off the engine in my Cessna 140 fairly often and keep it off through the landing. I would do it over an airport, in open country with no risk to others. I would pull the nose up to get the prop to stop windmilling, then make sure everything was setup to restart the plane if necessary... it never was. Was it smart, probably not. Was it fun... yup. Would I do it again today? Probably not.

As others have pointed out, gliders fly without engines and I've seen powered parachutes and gyroplanes do it often to demonstrate how safe they are.

 

[Ed Haywood]

Personally, I wouldn’t add the extra risk.

And I have no issue with that. Different people draw the line in different places. I have not done it either ... yet. But I think some of the doom responses are overwrought.

 

[Ed Haywood]

I don't recommend it, but I won't discourage it either! Many years ago, I used to shut off the engine in my Cessna 140 fairly often and keep it off through the landing. I would do it over an airport, in open country with no risk to others. I would pull the nose up to get the prop to stop windmilling, then make sure everything was setup to restart the plane if necessary... it never was. Was it smart, probably not. Was it fun... yup. Would I do it again today? Probably not.

And if you ever had to do an off-airport landing in a real emergency, it probably would have been a non-event for you.

 

[MauleSkinner]

And if you ever had to do an off-airport landing in a real emergency, it probably would have been a non-event for you.

By the time I had my seventh actual engine failure or shutdown, it was a nonevent. But shutting down engines and landing wasn’t what allowed the first 6 to turn out just fine…it was procedural training that made the difference.

 

[Lowflynjack]

I will say that shutting the engine off probably wasn't wise, but I don't see it as me taking a huge risk either. I managed my airspeed and made sure I was within gliding distance during the whole sequence. We take risks as pilots. Glider pilots have a risk of not being able to go around, but they enjoy flying without an engine. I've decided flying gliders isn't for me!

Personally, I pull the power in most airplanes at the numbers and try not to touch the throttle. I was taught when learning to fly and I've always done it. I know I will make the runway even if the engine quits. My friend, who has been flying longer than I have, keeps some power on, saying that the engine is most likely to fail when when adding power from idle... neither of us thinks the other is correct!

 

[Mongoose Aviator]

I have to chuckle when people freak out about intentionally shutting off an engine. Between glider ratings and the requirement to shut down an engine in both training and the check ride for multi engine rating, I'm always amazed at how irrational people are about this topic. The odds of the engine not restarting are just not that high.

I did completely shut off an engine during multi training while in flight. Including feathering the prop. It was surprisingly difficult to get the engine started again. My MEI in the aircraft with me (during the engine shut down) had 20+ years experience flying multi engine aircraft in the USAF as a full-time military pilot. So, I was not nervous at all as I was very confident that if we did not get the engine started again, my MEI was completely capable of landing the aircraft.

We did (together myself and my MEI) do another engine shutdown in the twin during another flight to try and see if we could do a better job of starting the engine. Restarting the engine after it has been feathered was just not easy.

I still think the original poster is a troll but hey!!! Good trolling!!!

 

[PaulS]

Yeah, I'm not freaking out, but I still think it's dumb. "Want to know what it's like" can be carried to other things too. Maybe a skidding turn at low speed base to final at 500 or 600 feet to see what it's like? Or simulating a passenger freak out by pulling the yoke to its stop on rotation so we can experience it? Not for me.

Is shutting down a single engine irresponsible? Probably not depending on how and when it's done, but I think if something were to happen, shutting down a perfectly good single engine would definitely be something the FAA would hone in on.

In my mind, aviation is full of risks that we work to mitigate. Accepting additional risk in the name of finding something that at the end of the day is meaningless just shouldn't be added to the risk profile of an average pilot.

 

[brcase]

Airplanes glide substantially better with stopped props than windmilling props.

Generally this is false is smaller single engine airplanes. I would say they fly marginally better as in not noticeably better, especially in an emergency. Bigger Higher powered airplanes with bigger props may benefit more from stopping the propeller but generally these planes are fast enough that stopping the prop is not very likely with out a catastrophic engine failure, or it has a feathering mechanism .

Just be aware that even in “motorglider” (which are designed to stop and then restart the engine later) there are numerous crash/incident reports where the engine would not restart, for various reasons. Motorglider pilots are supposed to not rely on the engine starting and be prepared to make an out-landing (off field landing) just like a non-engine glider pilot.

Cold soaking an engine before starting tends to make this a bit more likely, Gliders are usually using 2 stroke engines, although a number of them are using Rotary (Wankel) engines.
I am not a multi-engine pilot (one engine is scary enough), but am told restarting an engine in multi-engine airplanes after the required single engine demonstration (ACS) for a checkride can occasionally be problematic and the ACS addresses some risk mitigation in this event. (do it over an airport, for example)

Losing engine power in flight is an emergency. I don't intentionally create emergencies.

This isn't an emergency until at least plan C for me..

Plan A. Restart the Engine
Plan B. Land on the Runway below. Occasionally this is a 6mile by 12mile wide dry lake. It would take some real skill to mess up a power off landing on it.
Plan C. Land in the Taxiway, or to side of the runway.

Here is a rope break video, the equivalent of a power failure on take off. It really didn't seem like an emergency, more like just following the plan.

Video: Low-Time Glider Pilot Has Tow Rope Break Down Low

Glider pilot Aryanna Valdovinos was flying in a Schweizer SGS 2-33 at low altitude, the towline broke. This video shows how she handled the situation.

www.planeandpilotmag.com

But if it fails to restart it IS a failure.

And we have a plan for that, land on the runway is Plan A, and we have plan B and C.

If the prop isn't stopped, there is little noise difference between idle power and no power.

Agreed, I have pulled the mixture a time or two while the engine was at idle just to demonstrate to pilots that they can't tell the difference.
Which sort of is the point of why we don't practice it. Pulling the mixture to idle is a very accurate demonstration of a real power failure.
If you can handle an idling engine you can handle a dead engine.

BTW: the closest I have been to an actual power failure was when being towed by a Citabria, I released at 2000ft AGL and the Tow plane (Citabria) pilot pulled the throttle back to idle to descend back to the airport. When he went to open the throttle nothing happened, The thottle cable had disconnected. He ended up landing it on Railroad Access road with no damage. Fixed the cable and flew it back out. Since I switched frequences almost immediatly after releasing I didn't learn about it until I landed 2 hours later, and he already had the airplane back at the airport.



Brian

 

[Capt. Geoffrey Thorpe]

my gyro has a 912 and I’m really curious to see how it behaves engine-out, because it doesn’t have a mixture control to shut it off and would mean turning it off with a key, I’m reluctant to do so. And with it having a gearbox, I suspect it would take a pretty high airspeed to keep it windmilling.

Based on my experience....

My 912 keeps on windmilling for at least a while when I run a tank dry (long enough to switch tanks and get fuel back to the engine at which point it fires right back up on its own.)

Not based on experience...

I wouldn't want to shut down the mags (yes, I know, they are not really magnetos) and have it keep pumping fuel through the engine.

 

[Mongoose Aviator]

I am not a multi-engine pilot (one engine is scary enough), but am told restarting an engine in multi-engine airplanes after the required single engine demonstration (ACS) for a checkride can occasionally be problematic and the ACS addresses some risk mitigation in this event. (do it over an airport, for example)

The ACS does not state to actually turn off one of the engines during a Multi checkride with a DPE. The ACS speaks of simulated feathering and zero-thrust during the checkride.

I know the DPE during my checkride specifically discussed with me the training I had received with my MEI in regards to actually stopping, feathering and re-starting the engine during flight however the DPE during the checkride appeared to follow the ACS and use the zero-thrust approach while I demonstrated the various single engine maneuvers.

 

[ArrowFlyer86]

Curious if it’s a horrible idea to turn off the engine on Cessna 172 to enjoy some quiet gliding on a high altitude decent day 10,000ft to sea level.

If you want some quiet flying, go get yourself some Bose A30s.
... Or better yet just go get your glider rating...

Intentionally turning off your only engine seems like the worst way to get some peace and quiet, but I suspect you already knew that by the phrasing of your question

 

[Lindberg]

Maybe a skidding turn at low speed base to final at 500 or 600 feet to see what it's like? Or simulating a passenger freak out by pulling the yoke to its stop on rotation so we can experience it? Not for me.

You haven't practiced spin avoidance/recovery, and departure stalls?

No one's saying shut off the engine at 500 feet.

 

[dmspilot]

The ACS does not state to actually turn off one of the engines during a Multi checkride with a DPE. The ACS speaks of simulated feathering and zero-thrust during the checkride.

I know the DPE during my checkride specifically discussed with me the training I had received with my MEI in regards to actually stopping, feathering and re-starting the engine during flight however the DPE during the checkride appeared to follow the ACS and use the zero-thrust approach while I demonstrated the various single engine maneuvers.

That is not correct. Private/Commercial AoA X, Task A, requires an in-flight shutdown and restart. Simulated failures are used in other tasks. The other tasks (C and D) note that the "evaluator should then establish zero thrust on the inoperative engine." It is quite clear which Tasks require simulated shutdown and which requires the engine to actually be shut down.

 

[Half Fast]

No one's saying shut off the engine at 500 feet.

No, IIRC it was shut down at 10,000' and glide all the way to the ground, which of course does involve passing through 500' with a dead engine late in the exercise.

 

[Dana]

Should've had a poll.

I used to do it fairly often in my T-Craft and unlike Trevor Jacob, my airplane didn't die.

The first time I tried it I was over a long runway with no other traffic in the area, and plenty of grass alongside the runway in case it was obstructed. On other occasions it was above open farm country with plenty of landing options. It had to be slowed nearly to stall to stop the prop windmilling, and yes, glide is noticeably better with it stopped vs. windmilling (prop stopped glide is similar to engine idling). Had to dive near to Vne to get it turning again (the T-Craft had no starter).

Never had a problem getting it restarted; a windmilling prop spins a lot faster than the starter will spin it, and unlike a starter which can crank for only a limited time, it keeps on spinning until it starts. Sometimes I would leave it stopped all the way to landing (control in the flare is noticeably different).

On a couple of occasions on thermic days I actually gained a couple of thousand feet before losing the lift. Fun!

For those of you furiously genuflecting and saying, "BAD! Don't do that!", you're probably right, YOU shouldn't try it, at least not on your own. But some of us have a more inquisitive mind and like knowing how the aircraft performs in all flight regimes.

 

[Mongoose Aviator]

That is not correct. Private/Commercial AoA X, Task A, requires an in-flight shutdown and restart. Simulated failures are used in other tasks.

I stand corrected. I have no doubt that we did it exactly as you stated and it was my recollection at fault here for the previous posting.

 

[Bob Noel]

Why are you expecting poor in-air restart performance from a 172? Air, spark, fuel, the things it takes to make an engine run. Which of those isn't present when starting an engine in the air?

To others point, in-air restarts are a regular occurrence for multi-engine training.

What part(s) of the certification process for the engine in a 172 covered in-air restarts?

I'm reminded of the Apollo 13 movie... remember the Grumman guy? "I want you to understand that we've never tried this before: burn, cold soak, burn, cold soak, burn, manual control."

edit: I should clarify that I'm only playing devil's advocate. I don't have any basis for saying the 172 wouldn't start or not.

 

[RyanShort1]

Based on my experience....

My 912 keeps on windmilling for at least a while when I run a tank dry (long enough to switch tanks and get fuel back to the engine at which point it fires right back up on its own.)

Not based on experience...

I wouldn't want to shut down the mags (yes, I know, they are not really magnetos) and have it keep pumping fuel through the engine.

912s will stop windmilling with a bang and unless you have a good ignition, I'm sure I'd trust it to restart with just the prop. In fairness, I was flying a motorglider Pipistrel for most of those, but I had some time in an Apollo Fox and once another PIC shut the engine off in flight. I just don't think you get as much experience from that as from safer maneuvers.

 

[rwellner98]

By the time I had my seventh actual engine failure or shutdown, it was a nonevent. But shutting down engines and landing wasn’t what allowed the first 6 to turn out just fine…it was procedural training that made the difference.

That's the second highest I've ever heard. A friend of mine in Mexico used to tow advertising banners at the beaches and he had 13 engine failures.