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

[Jim Logajan]

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.

 

[Jim Logajan]

Counter/clarifying question: is the plane actually climbing at that speed? (before the engine quits)

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.

 

[Jim Logajan]

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

Can you suggest an example airplane model and configuration that would stall?

 

[Jim Logajan]

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

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]

Save us some time: Where in the video do the stalls occur?

Nauga,
and the difference warning and break

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?

 

[Jim Logajan]

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?

 

[Jim Logajan]

Thanks everyone! Here is what I found:

I tabulated the results of 6 configurations of climb speeds and flap settings and have a link to a 2 minute video of the gauges of the airplane panel at the following web page (my various follow-up comments there are simply too long to re-post here):

https://tinyurl.com/takeoff-engine-out-stall

Bottom line: the nose drops rather abruptly. In only about 2.5 (+/- 0.4) seconds the plane has lost all the speed (~4.5 knots +/- 1.8) it is going to and will start accelerating to well above trim speed; the beginning of a phugoid. In my discussion on that web site I post my reasons for believing any GA airplane with a standard category certification by the FAA is unlikely to stall during a hands-off climb if an engine failure occurs. However, I think it a worthwhile exercise to perform at a safe altitude since I could be wrong!

 

[Jim Logajan]

Context:

The airplane is trimmed to climb about 5 mph or knots above stall.

Ugh. You are correct about the context. I messed up when I stated the airplane was 5 over stall. I should have said something like climbing at Vx.

In a C-152 the slowest wings level stall speed is in the most forward CG at 40 KIAS at flaps of 0 to 10 degree flaps but 35 KIAS at 30 degree flaps. The slowest scenario I tested the was 51 KIAS with a worst case 7 KIAS speed drop. So if it were just 5 knots over stall then it may be an even chance it would stall on engine out (but since it wasn't tested that slow I can't be sure.) But I was close to running our of trim at 50 knots and I can't think of any normal reason to climb below the lowest POH speed (short field takeoff, flaps 10 degrees) of 54 KIAS.

 

[Jim Logajan]

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.

Agreed.

That is not what I found in real tests documented here:
https://tinyurl.com/takeoff-engine-out-stall

 

[Jim Logajan]

If I had used a different oscilloscope as dead weight would that have affected my test results?