[Ref. The Pilot’s Manual PM2 Ground School Page 23,84]
Washout – decrease AOI(Angle of Incidence) from wing root to tip.
Washout imply wing root would reaches stall angle prior to the wing tip, thus wing root would stall first
Notes: rectangular wing also tends to stall at wing root first.
Benefit of wing root stalling first
- allow the control buffer over the horizontal stabilizer
- the ailerons should still be effective – even in case asymmetric stall (i.e stall occurring on one wing before the other)
AOI – angle between Chord line and Longitudinal;
AOA – angle between Chord line and RAF