PPRuNe Forums - View Single Post - AF 447 Thread No. 8
View Single Post
Old 25th May 2012, 17:51
  #935 (permalink)  
gums
 
Join Date: Jun 2009
Location: florida
Age: 81
Posts: 1,610
Received 55 Likes on 16 Posts
Salute!

Thank you , OG, for the observation that the classical stall depiction and AoA is more applicable to general aviation planes and very old straight-wing designs.

The top of the curve for just about any bent-wing plane is less severe. There's no abrupt loss of lift, and additions such as leading edge flaps, slats, slots, etc. can make the stall onset very delayed. With enough thrust, you can even remain controllable and flying well beyond the maximum AoA versus lift point on the curve. Wing loading and aspect ratio also contribute to "flyability".

The high-aspect wings increase drag faster than loss of lift. You can also see this with a plane that has great directional authority and a high wing-loading. So I flew one model that had classical AoA versus lift curves, but you could get that sucker up to 40 or 50 degrees AoA and sink like a rock without getting into a spin. The rudder remained very effective. To recover all you had to do was lower the nose. Hmmmm......

On the delta I flew ( like the Concorde and such designs), we did not have a sharp break in lift versus AoA, but drag increased dramatically. The Viper had similar characteristics due to the leading edge flaps and using the flaperons to shape the camber of the wing. So our alpha limit was more due to the mission requirements - maintain energy and maximize lift versus drag. The Hornet was not designed like that.

I must add that our FBW laws had many sensor inputs that kept the pointy end forward. Rate gyro inputs, acceleration inputs in all three axis, AoA until the three probes froze up, then things were based on last value or ignored and body rates became prime. Attitude was not used in any fashion, unlike the 'bus laws that limit bank angle and pitch attitude according to the mode and sub-mode of the system.

out,
gums is offline