Aerodynamics and Flight Controls
Lift, drag and the speed trade
The exam tests practical relationships: lift L = ½ρV²SC_L; induced drag falls as speed rises; parasite drag rises with V². Total drag is minimum where they cross. Angle of attack (AoA) controls lift coefficient; pitch attitude is not AoA. A stall occurs at critical AoA regardless of speed, weight or bank, though those change the speed at which it occurs. Controls: ailerons roll, elevator pitches, rudder yaws; trim reduces pilot load; flaps increase C_L and drag; spoilers spoil lift and add drag.
Stability, control and high-speed effects
Static stability means an initial tendency to return; dynamic stability describes the resulting motion over time. Dihedral gives lateral stability; sweep gives directional and lateral effects and delays drag rise. At high Mach, shock-induced separation can cause Mach tuck and buffet; control effectiveness changes. Flutter is an unstable interaction of aerodynamics and structure and is prevented by stiffness, mass balance and placards.
Worked example
Sea level, ρ = 1.225 kg/m³, V = 60 m/s, S = 16 m², C_L = 0.4. L = 0.5 × 1.225 × 60² × 16 × 0.4 = 14,112 N (about 1.44 t mass equivalent). If C_L is doubled at the same speed, lift doubles; if speed rises by 10%, lift rises by about 21% because V is squared.
Traps
Do not use pitch attitude as AoA; do not say lift is only Bernoulli (Newton and circulation both contribute); do not forget density altitude; and do not assume a higher speed always means more margin - flutter and Mach limits can reduce it.