Constant Airspeed turns

[Jaybird180]

In training airplanes, I can't imagine this being too effective as they tend to hold airspeed pretty well, and also any losses will be quickly recovered, so much that it's not in the PP PTS, although constant airspeed climbs and decents are.

Years ago, I saw a depiction and instructions in the 1987 (or 88- not sure) World Book Encyclopedia on how to turn an airplane. It explained that with the control inputs of aileron, rudder and elevator would add enough drag that the pilot would then add power to compensate. For whatever reason, this was on my mind this morning (see - what you put in your mind eventually comes out). I now realize that this was a constant airspeed turn.

Who uses them in their everyday flying and what practical purpose do they serve?

Yes, I agree that it adds precision to flying. The cost however is increased turn radius for a given bank angle in a coordinated turn, so why bother?

 

[Sac Arrow]

Well, for one, stall speed increases with bank angle, and if you're losing speed in the turn to begin with....

 

[poadeleted20]

Depends on your speed and bank angle -- in some cases, failure to add power will result in the speed decaying to the point at which you reach stalling AoA while trying to use higher AoA to compensate for lost lift to maintain altitude. What happens is you lose some of the vertical component of lift in the bank, so you have to increase AoA to compensate. The extra drag of that higher AoA slows you, costing you more lift, and you add more AoA to compensate. This continues until you reach a speed where you have enough power to maintain altitude at that lower speed and higher AoA -- unless you hit critical AoA first, at which point you stall. Not a big deal in a shallow turn or at cruise speed, but at minimum controllable airspeed or at high bank angles (like steep turns) it can spoil the party.

 

[DouglasBader]

Yes, I agree that it adds precision to flying. The cost however is increased turn radius for a given bank angle in a coordinated turn, so why bother?

It's a matter of flying the airplane, vs. letting it fly you.

Are you particularly concerned about the radius of your turn?

I've only flown a few places where I'm very concerned about the radius of the turn on departure, where I'd normally leave flaps down and use the lower airspeed to reduce radius, and where I'd maintain that radius at the slower airspeed on the climb...Kabul, Bagram, etc. Most places, it's just not an issue.

When you're training, it's axiomatic that when doing a steep turn or any kind of turn, you'll get in the habit of adding power in the turn. It may not take much. It may take a lot, depending on the nature of the turn. Where I'm flying presently, with a lot of steep turning close to the ground (and always a concern for the radius of the turn due to terrain), I make big power changes when maneuvering. I also lower flaps in the turn, or have them extended before I start maneuvering.

Keeping your airspeed constant as you load and unload the wing in the turn is a way of teaching you to fly the airplane. By ensuring that you're adding power to keep the airspeed constant as you enter the turn, and to smoothly retard the power as you roll out, you're developing life-long habits associated with flying the airplane. These aren't annoyances designed as superficial, meaningless exercises. They're central to understanding how to operate the aircraft.