Basic Aerodynamics
Core concepts
Understand the atmosphere (ISA, pressure, density, temperature lapse), airflow and Bernoulli's theorem, the generation of lift and drag, boundary layers (laminar and turbulent), and the four forces in equilibrium. Know aerofoil terminology: chord, camber, angle of attack, stagnation point, centre of pressure. Cover Mach number, compressibility effects, shock waves, and the basics of stability and control about three axes.
Traps to watch
- Angle of attack vs pitch attitude: they are not the same; AoA is relative to the airflow.
- Bernoulli alone is incomplete: lift also requires Newton's third law (downwash); exam questions often test the combination.
- Centre of pressure movement: as AoA increases, the centre of pressure typically moves forward on a cambered aerofoil.
- Critical Mach number: local airflow reaches Mach 1 before the aircraft does; this is where shock waves begin.
- ISA values: sea level 15 °C, 1013.25 hPa, lapse rate 1.98 °C per 1000 ft up to the tropopause.
Worked example
At 10,000 ft in ISA, temperature = 15 − (1.98 × 10) ≈ −4.8 °C. Density falls with altitude, so for the same true airspeed the dynamic pressure and hence lift are lower; more speed or a higher angle of attack is needed. Dynamic pressure q = ½ρV².
Rule of thumb
When a question mentions lift, drag or pressure, immediately think "angle of attack and dynamic pressure". Most aerodynamics distractors attack one of those two.