Originally Posted by
beinghuman
Hello Guys,
One question. I've read and heard everywhere that an aerofoil stalls at a constant angle, irrespective of speed. I came across a statement saying '' As the flap is lowered, Cl max increases but the stalling angle is reduced ''
How and why does the stalling angle change in this scenario ?
From a pure aerodynaimcal point of view the stalling angle of the effective new chord does not decrease. Rather the contrary (due to more camber).
However in an aircraft the AoA is measured with regard to the main plane and not with regard to the new effective chord (which is altered due to the rear part of the chord being moved downward). Aerodynamic AoA 0° with flaps down would provide negative AoA readout on the instruments.
The effective increase in max AoA of the more cambered profile is less than the effective tilt of the chord on the airframe when deploying the flaps, thus resulting in a reduced max AoA wrd to the airframe.