contactflying wrote:At high density altitude and underway, we don't want the flaps impeding rapid transition from descending air to rising air. In the mountains, the difference between rising and descending air makes far greater climb difference than flaps. Using flaps in rising air and dumping them in descending air would be technically correct, but pitching up in rising air and pitching down in descending air is more rapid and effective.

Attempting climb, with or without flaps, in descending air is defective and dangerous.

Exactly right. And allow me to state the obvious just for my own peace of mind: PLEASE don't rely on flap setting to out climb terrain in the airplanes we fly without a clearly marked exit strategy. It's a bet that will eventually be lost, guaranteed.

gbflyer,

Thanks for the help in reminding pilots to always position themselves where a descending turn can be made to down drainage.

There are so many things that affect Vx and Vy and all that V stuff. Controlling the airplane is so simple: when pulling back no longer makes the aircraft climb, try pushing forward a bit. I have amazed so many students with this stupid little trick.

contact

Thanks for all the great input. I really appreciate the constructive discussions. There is a lot of experience here.

Fly a 2008 Scout....My plane definitely climbs out of Idaho canyons better with one notch of flap deployed..

If I followed the flight manual of my ancient P172D exactly, I'd use no flaps at high density altitudes. But with the more powerful engine that I have, and lots of practice to make sure I'm right, I still use 10 flaps off of any soft surface to get the mains off the ground as early as possible, even at DAs approaching 10,000'. Off of paved strips, I don't bother with flaps for take off, although I can use them to break ground a little sooner.

But once I've built speed to climb out, I retract those 10 flaps, because at Vy I'm getting close to Vfe and they're not providing any benefit for the climb-out and are providing some unnecessary drag.

Different airfoils and different engines will undoubtedly provide different results. There's no "one size fits all" answer.

Cary