Power stall

[Farrell]

Hi folks

Can anyone tell me what a 'power stall' is and what the implications of getting into one are.

Am I right in saying that it is to do with stalling at higher speeds when banking (and it having an effect on the load factor), or am I barking up the wrong tree?

Probably a stupid question - my apologies in advance if it is!

Wayne

[machonepointone]

I think that what you may be referring to is a "power ON stall." This is a reference to a situation that the unwary can get into during a go-around. If the aircraft is trimmed on the approach at low airspeed and low power setting, then the application of full power for a go-around will cause the aircraft to pitch nose up unless the pilot applies a lot of forward pressure on the control column to prevent it. In the absence of adequate forward pressure the aircraft can pitch up to a high enough attitude that the speed reduces to the point where the aircraft will stall.

[QNH 1013]

Not a stupid question in my opinion, but like M1.1 I wonder if you are referring to a power-on stall, or "stall with power"? The only other interpretation I can put on a "power stall" is a compressor stall in a turbine engine which is something quite different.

Anyway, assuming that we are talking about a piston aircraft stalling with power-on, the main differences are what happens to the aircraft as it stalls.

In a power-off stall, the designer will have (usually) arranged things so that the inner sections of the wing stall before the outer sections. This reduces the tendency for a wing to drop at the stall, and the ailerons may (but not guaranteed) still be effective even though the inner sections of the wing have stalled.

When a piston engined aircraft is stalled with a medium-to-high power setting, the propwash will prevent the inner sections of the wing stalling first by reducing the angle of attack of the airflow past the sections of the wing in the propwash. The first parts of the wing to stall are now likely to be the outer sections and because they are further from the fuselage any inbalance in lift as they stall will provide a higher rolling force, hence a wing-drop. Also the propwash at these higher power settings will be inducing more yaw as it strikes the fin. The usual result is a more dramatic stall and wing-drop, and if mishandled, a possible spin.

There are other effects too, but the above covers the basics.

[minus273]

Hey there,

May be of some help but not sure as is FAA orientated.

We teach an Accelerated stall which is a stall in steep turn, this is usually to CFI candidates and demonstrated to PPL and Commercial pilots.

The accelerated stall would be in a steep turn usually 45deg to show that as you increase bank angle and thus load factor you will in turn increase the indicated speed at which the aircraft stalls.

It is used to help them avoid that lovely situation where they get slow and low, examples would be a forced landing or even ordinary landing if they get too slow. They try to get the aircraft lined up with where they want to land and over bank and stall spin the aircraft on final when they overshoot final and try to bring it back onto centre-line.

You obviously do this demo at above 3000AGL.

The other stall you mentioned is the Power on stall, this goes by a variety of names, Power on, after take-off, go-around.

As the names suggest the stall occurs when the aircraft has been made to do something with full power, as stated by one of the other posters this will usually mean that the trim has been set for a landing or forced landing and as full power is set the pilot is unable to hold the aircraft at the desired attitude the nose comes up and the aircraft stalls.

You would be amazed or not depending on your experience how much force will be required to hold the nose as required when you go from no power and glide trim to full power.


Hope that is of some help

-273

[Farrell]

Thanks so much for answering chaps.

Another obstacle removed!

Am moving to Wiscon in September and so am doing an intensive FAA Airline Transport Rating.

Need to get my head around that now!

Wayne