Will an airplane engine failure on takeoff cause an aerodynamic stall?

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Jim Logajan

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Will an airplane engine failure during a takeoff climb cause an aerodynamic stall? In this scenario the pilot's hands are off the stick or yoke - or at least only lightly applying aileron control, no elevator. The airplane is trimmed to climb about 5 mph or knots above stall.

I ran a series of experiments on this in 2015 and recorded a video of the instrument panel at various flap settings in a Cessna 152. So I know the answers for the different configurations in that airplane. Am wondering what everyone will say. I only recently edited the video to a small length and will share the video in a few days or whenever it looks like all those sure enough or brave enough have submitted answers.
 
Counter/clarifying question: is the plane actually climbing at that speed? (before the engine quits)
 
Tabuka said:
Counter/clarifying question: is the plane actually climbing at that speed? (before the engine quits)
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Yes. Although I will admit that the C-152 was barely climbing in the full flaps at 50 knots. The other configurations and speed it was climbing when the throttle was cut.
 
Engine power doesn't (much) affect stall. Speed doesn't affect stall. Trying to maintain altitude or climb in light of those things being lost by increasing AOA past the critical angle causes the stall.

Yes, you can trim a plane such that it will stall itself.
 
Depends on the configuration, longitudinal stability (i.e. CG), and to some extent control system of the airplane (bobweights, downsprings, etc). There is no one answer that covers every permutation. That being said, I'd bet it's pretty difficult to get a 152 to stall with a loss of thrust in a *steady* climb.

Nauga,
and a little DOE
 
My answer is no, it will not stall. The plane will start descending at approximately configured airspeed.

Edit: for cessna 152 given it's stability and limited thrust, other planes may vary
 
nauga said:
Depends on the configuration, longitudinal stability (i.e. CG), and to some extent control system of the airplane (bobweights, downsprings, etc). There is no one answer that covers every permutation. That being said, I'd bet it's pretty difficult to get a 152 to stall with a loss of thrust in a *steady* climb.

Nauga,
and a little DOE
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Can you suggest an example airplane model and configuration that would stall?
 
Tabuka said:
My answer is no, it will not stall. The plane will start descending at approximately configured airspeed.

Edit: for cessna 152 given it's stability and limited thrust, other planes may vary
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Are you sure? According to the first video you have to push forward on the yoke and in the second the stall horn allegedly sounds - and you have to push forward on the yoke:


 
Jim Logajan said:
Are you sure? According to the first video you have to push forward on the yoke and in the second the stall horn allegedly sounds - and you have to push forward on the yoke
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Save us some time: Where in the video do the stalls occur?

Nauga,
and the difference warning and break
 
nauga said:
Save us some time: Where in the video do the stalls occur?

Nauga,
and the difference warning and break
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They both performed the engine out very low so they were forced to implement their recommended action immediately. Although the second video shows an engine out a second time at a higher altitude he appears to be concentrating on discussing another issue.

Have you experimented with engine out during climb on take-off? If not, why not?
 
I only watched the first video, but it's not responsive to the question, which was of the airplane trimmed for the climb would stall hands off the yoke. If the pilot holds the yoke back, then absolutely the airplane will stall or just mush into the ground.
 
In an old Citabria manual for the plane flew for a while I seem to recall a warning along the lines of "if engine failure occurs during a Vx climb, pilot must immediately push forward on stick to prevent a stall." So maybe the answer is it depends. Vx was very nose high in that plane (probably a GCBC).
 
Jim Logajan said:
Will an airplane engine failure during a takeoff climb cause an aerodynamic stall? In this scenario the pilot's hands are off the stick or yoke - or at least only lightly applying aileron control, no elevator. The airplane is trimmed to climb about 5 mph or knots above stall.

I ran a series of experiments on this in 2015 and recorded a video of the instrument panel at various flap settings in a Cessna 152. So I know the answers for the different configurations in that airplane. Am wondering what everyone will say. I only recently edited the video to a small length and will share the video in a few days or whenever it looks like all those sure enough or brave enough have submitted answers.
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Even with trim all the way up, most GA planes will not stall with power off and hands off the controls. I know some people advocate for aggressively pushing on the controls when there is a power loss, but that is totally unnecessary.
 
Airplanes with a high thrust line, like the Lake Buccaneer or BD-5 will pitch nose up if power is lost.
Better be quick with forward stick when close to the ground.
 
Non Compos Mentis said:
Airplanes with a high thrust line, like the Lake Buccaneer or BD-5 will pitch nose up if power is lost.
Better be quick with forward stick when close to the ground.
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Absolutely true, but most GA planes including the 152 referenced in the original post do not fall in that category.
 
inadvertent thrust reverser deployment can do it on certain airframes. It disturbs enough flow over the wing to cause problems.
 
sarangan said:
Even with trim all the way up, most GA planes will not stall with power off and hands off the controls. I know some people advocate for aggressively pushing on the controls when there is a power loss, but that is totally unnecessary.
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One possible reason...

In training we practice engine failure at altitude in a cruise configuration. When the engine quits we raise the nose to slow to best glide.

During takeoff, though, when the engine quits we must accelerate to best glide speed, and that requires lowering the nose.

It needn’t be “aggressive” but we have to fight the instinct to pull up.
 
I'm gonna say the plane will stall without pushing forward on the stick/yoke. The stall depends on the AOA to the relative wind. Well, if the engine goes out on takeoff, then the loss of forward thrust would affect the angle of the relative wind causing the AOA to be critical in a very short period of time.
 
Half Fast said:
One possible reason...

In training we practice engine failure at altitude in a cruise configuration. When the engine quits we raise the nose to slow to best glide.

During takeoff, though, when the engine quits we must accelerate to best glide speed, and that requires lowering the nose.

It needn’t be “aggressive” but we have to fight the instinct to pull up.
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I agree with you, but there are plenty of people advocating that you need to pull a negative G when you lose power on takeoff. If that is not aggressive, I don't know what is. Here is one example.

 
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sarangan said:
Even with trim all the way up, most GA planes will not stall with power off and hands off the controls. I know some people advocate for aggressively pushing on the controls when there is a power loss, but that is totally unnecessary.
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Depends on the pitch attitude, airspeed, and <maybe> the stability of the aircraft. In a normal climb, at 20 knots above stall, I would expect a trimmed to climb speed 172 to pitch over and glide, rather than stall. OTOH, if the 172 was at full power 5 knots above stall speed at a high AOA and the engine quit, I'd expect it to stall.
 
kyleb said:
OTOH, if the 172 was at full power 5 knots above stall speed at a high AOA and the engine quit, I'd expect it to stall.
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Interesting.

Why wouldn’t you expect it to continue flying at 5 knots above stall, though beginning a (possibly rapid) descent?
 
Half Fast said:
Interesting.

Why wouldn’t you expect it to continue flying at 5 knots above stall, though beginning a (possibly rapid) descent?
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you're probably getting the equivalent of 5 knots relative wind from prop wash.
 
I really appreciate the responses!

Doesn't look like anyone so far has professed personal knowledge of actually performing the experiment or knows anyone who has actually done it. Yes, some have done demos at low altitude, but not to the point of actually letting the airplane do its thing absent pilot elevator control. Maybe this will get people to actually try it next time they are up in an airplane with some time to try it out. I found it informative in a practical way.

Not sure when I should post what I discovered. Maybe tomorrow?
 
In my humble experience, there is very little chance of a stall that is not pilot-induced. For me, once the fan goes quiet, the plane has always promptly nosed over and descended at at least the airspeed for which it had been trimmed. There are variables such as different configurations, CG, etc, but I can only imagine that you'd ever experience a truly hands-off stall if you were severely outside of the CG envelope, grossly out of trim, or some interpolation of both. But even trimmed full aft, I rarely get below glide speed without backpressure
 
In my 150, best climb speed is within a few knots of best glide. If trimmed hands off in the climb, and power pulled, it arcs over at nearly constant airspeed and settled into a descent at very nearly the previously trimmed speed. Propwash has some effect over the tail, but in my case not enough to make much difference. I have tried this and an aggressive push is not necessary to prevent a stall.
 
Jim Logajan said:
I really appreciate the responses!

Doesn't look like anyone so far has professed personal knowledge of actually performing the experiment or knows anyone who has actually done it. Yes, some have done demos at low altitude, but not to the point of actually letting the airplane do its thing absent pilot elevator control. Maybe this will get people to actually try it next time they are up in an airplane with some time to try it out. I found it informative in a practical way.

Not sure when I should post what I discovered. Maybe tomorrow?
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I’ve done it. Depends on the plane. Do it and see for yourself.
 
Jim Logajan said:
I really appreciate the responses!

Doesn't look like anyone so far has professed personal knowledge of actually performing the experiment or knows anyone who has actually done it. Yes, some have done demos at low altitude, but not to the point of actually letting the airplane do its thing absent pilot elevator control. Maybe this will get people to actually try it next time they are up in an airplane with some time to try it out. I found it informative in a practical way.

Not sure when I should post what I discovered. Maybe tomorrow?
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I've tried it on many different trainers. None of them enter a stall without pilot input. Nearly all recover on their own if you let go. Only one time I came across a situation where that didn't happen. It was a commander 112. It took considerable effort to break from a practice stall. My guess is that I drove it too deep into the stall. The T-tail configuration probably had something to do with it as well.
 
You need to disconnect the thought that an engine makes a wing fly. Think sailplane, about as efficient as mortals can get, no engine. The wing flys on relative wind, so as long as you have the relative wind you will fly and not "stall" the wing. Doesn't matter if the engine is running or not. Now you need to keep that relative wind to keep from stalling the wing. that requires, "in this case" forward momentum, energy management would be more appropriate for this example. But the forward momentum provides the relative wind to keep the wing flying. That is where the energy management comes into play. Has almost nothing to do with the engine running. It has everything to do with keeping appropriate relative wind across the wing, in order to keep flying. The ONLY thing an engine does is provide forward momentum that can be used to create relative wind.
 
More to the point, if you let the airplane recover itself following an engine failure on takeoff, at what descent rate will you impact the ground?
 
Loss of engine can cause pitch changes and trim issues. The propwash does have an effect on the eppenage.
 
Oldmanb777 said:
You need to disconnect the thought that an engine makes a wing fly. Think sailplane, about as efficient as mortals can get, no engine. The wing flys on relative wind, so as long as you have the relative wind you will fly and not "stall" the wing. Doesn't matter if the engine is running or not. Now you need to keep that relative wind to keep from stalling the wing. that requires, "in this case" forward momentum, energy management would be more appropriate for this example. But the forward momentum provides the relative wind to keep the wing flying. That is where the energy management comes into play. Has almost nothing to do with the engine running. It has everything to do with keeping appropriate relative wind across the wing, in order to keep flying. The ONLY thing an engine does is provide forward momentum that can be used to create relative wind.
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It may be of interest that in a glider, if the tow line breaks during launch, you’d better push the nose down pretty quickly.
 
That is a very slow climb, with a lot of up trim to be flying that slow hands off. I almost never trim to fly that slow, other than slow flight demonstrations.
Vx is 55kts.
Stall Speed is 36-40KIAS depending on CG. CG position may slightly affect the answer.

So for the OP's Scenario we would be climbing out a 41-45kts. I am not entirely convinced it can even be trimmed to fly that slow at least flaps up. But admit I haven't tried.

My best guess is NO it won't stall, but it will likely pitch down quickly and have a very high sink rate. If left long enough there might be some potential for a secondary stall. If the power failure happened below 50ft and maybe even 100ft I think a pilot would be unlikely to stop the decent enough to avoid damaging the airplane.


But I like answering interesting questions, I may try it tomorrow in the 172.

Brian
CFIIG/ASEL
 
Salty said:
It may be of interest that in a glider, if the tow line breaks during launch, you’d better push the nose down pretty quickly.
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Is that to prevent stall or to keep from decelerating even further from Vbg when you need all the performance you can get?

ETA: The followup question to either answer is "Are you sure?" ;)

Nauga,
tested, for sure
 
Salty said:
It may be of interest that in a glider, if the tow line breaks during launch, you’d better push the nose down pretty quickly.
Click to expand...

Yes that is true, its energy management to keep wind flowing over the wing. might be easier to say if a wing stalls, will the engine quit? They are not connected. They are independent of each other.
 
kyleb said:
Depends on the pitch attitude, airspeed, and <maybe> the stability of the aircraft.
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Maybe? I think (and data support that) it absolutely depends on the stability - for example, a neutrally stable airplane will not pitch down as AOA increases kinematically*, but a stable airplane will. There are other dependencies for sure, but stability is a big player.

*as speed decreases and the airplane begins to accelerate downward since lift is no longer equal to weight.

Nauga,
and the reason you pull to make the houses get smaller
 
Jim Logajan said:
Will an airplane engine failure during a takeoff climb cause an aerodynamic stall? In this scenario the pilot's hands are off the stick or yoke - or at least only lightly applying aileron control, no elevator. The airplane is trimmed to climb about 5 mph or knots above stall.

I ran a series of experiments on this in 2015 and recorded a video of the instrument panel at various flap settings in a Cessna 152. So I know the answers for the different configurations in that airplane. Am wondering what everyone will say. I only recently edited the video to a small length and will share the video in a few days or whenever it looks like all those sure enough or brave enough have submitted answers.
Click to expand...
Are you properly trimmed is an important question.
 
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