On 1/23/2014 7:18 AM, kirk.stant wrote (w. some snippage):


http://www.youtube.com/watch?v=2S7T81LbvIs

Nice pass!

A question for all you aero majors out the when pulling up at high
speed, should you lead with the flaps, or follow with them?

In this vid, pilot pulls, then lowers flaps after speed has dropped. My
understanding is that it is more efficient to lower flaps (from cruise to
zero, then positive as you slow) during the pull, and my experience
somewhat bears that out (higher alt gain with a good pull and simultaneous
flaps).


Neither lead nor follow?

Here's an attempt at one of those potentially worthless - in the sense that
for all practical purposes it can be neither effectively measured nor
implemented in real time - responses that might just shed some theoretical
light upon one's flying techniques...

If we - for the purposes of a pullup - define "efficiency" as "least
aerodynamic drag possible per time instant" (since both drag and gravity
oppose the ship's ability to trade kinetic energy for height) then the answer
to the question obviously (!) is the flaps should be placed in whatever
position minimizes aerodynamic drag for that instant's speed...think polar.

Complicating factors almost certainly include time and flap position, since
for any given (ever-increasing) amount of flap deflection (below the
separation angle of attack) the wing section can generate greater total lift,
which for a fixed-weight condition will be proportional to "wing developable
G." So, will a shorter time at high G (and drag) - meaning a shorter time to
change pitch angle from (say) "descending through pitched up" - result in
greater speed at the start of the ascent than a "theoretically most
aerodynamically efficient (longer-in-time) configuration" through the same
angular change?

I don't know, but my suspicion is aerodynamic efficiency would trump. In any
event, if we take "the rapid pitch-up" scenario to an extreme, various
fighters can demonstrate that a rapid pitch-up is a great way to bleed energy
and speed (think "the cobra maneuver").

As foe Joe Glider Pilot, this is a great example of one (ideally, many)
test(s) being worth ten thousand considered opinions! Kids, don't do this test
in the pattern...

Bob - it's still winter... - W.