Originally Posted by antpp
pitch angle = aoa in horizontal flight at FL 380 which has no other explanation than downward wind strong enough to change aoa by about 4 degrees.
You are misinformed. Pitch angle is between longitudinal axis and the horizontal plane.
Airplane AoA is the angle between longitudinal axis and airspeed vector. In horizontal flight in still air the airspeed vector is horizontal, therefore pitch = AoA. EDIT:: IOW, pitch=AoA implies zero vertical air movement.
Do not confuse
airplane AoA with the
local AoA of a wing section at any spanwise station, which varies considerably between wing root and tip.