Principles of Flight
Principles of flight questions test the physics of lift, drag, stability and control. Understand the four forces and how they balance in steady flight. Know the lift equation and that lift is proportional to density, velocity squared and wing area, and depends on angle of attack.
Learn the drag curve: parasite drag rises with the square of speed, induced drag falls with speed, and total drag is minimum at the speed for best glide (L/D max). Understand the significance of the critical angle of attack and the stall.
Stability: know the difference between static and dynamic stability, and between longitudinal, lateral and directional stability. Understand the role of the horizontal stabiliser, dihedral and fin.
Control: know the effect of ailerons, elevator and rudder, and the meaning of adverse yaw and how it is countered.
Traps: assuming lift is proportional to speed rather than speed squared; confusing best glide with minimum sink; and forgetting that a stall can occur at any speed.
Worked rule of thumb: to double the speed, lift quadruples at the same angle of attack, so the angle of attack must be reduced to maintain level flight.