Dear Bob and Richard,

I'm not sure if this is actually possible in flight, or if it is a hypothetical wind-tunnel situation: given the same IAS as at level flight, is the angle of attack during a climb greater than at level flight?


Cheers, rubber

I'm sure Bob and Richard can answer this better but my thoughts would be that "angle of attack is always related to the direction of the relative airflow" therefore as long as the a/c is flying cleanly, with apropriate power for the climb, then angle of attack doesn't alter - ie: you do not get any closer to the stall as long as Lift, Drag, Thrust and Drag are all on the curve. As you drop airspeed, you get closer to the area of reverse command on the L/D curve but this is not due to angle of attack directly. Having said that, the angle of attack must be increased at lower speeds to maintain sufficient lift at any given speed.

Hope this makes sense. In simple terms Lift, Drag, Thust and Drag are what keeps you where you want to be. Angle of attack is only usually a temporary state to get these other parameters in synch.

Thank you brentonrule. So in this case are you saying the AoA stays the same? rubber

It should be the same if you are flying the same IAS for the same weight, the only difference being that you are having to use more power to maintain the airspeed.

One of the surprises we get when we consider climbing is that, during a climb lift is LESS than weight. This is because an aeroplane does not use its wings for climbing - it uses its engine. So to climb more steeply, you need LESS lift and MORE thrust.

Now since lift is the result of angle of attack and airspeed and you need less lift in a climb, the lower climbing airspeed would require much the same angle of attack as level flight. You cannot say that it is exactly the same angle of attack as level flight, because there are other factors to consider such as the amount of surplus thrust available from the engine.

In fact if you took the ridiculous extreme case of unlimited thrust available, you could do a vertical climb at constant speed. Then you would need no lift at all from the wings!

Thanks Bob for your reply.

You mention that with the lower climbing airspeed, the angle of attack would be about the same as level flight. However my question is "what if the climbing IAS was the same as level flight".

A logical extension of the quote above would be that a decreased angle of attack is required for a climb at same airspeed.

Is this fair logic?

Cheers, rubber

Yep

Thanks Bob! Your books and this site are fantastic.
Cheers, rubber