Theory of Flight
Aeroplane aerodynamics and flight controls, high-speed flight, and rotary-wing (helicopter) aerodynamics.
Theory of flight — summary notes
Free- FIXED-WING: lift comes from a wing at an angle of attack (L = C_L·½ρV²·S); the primary controls act about three axes — ailerons roll, elevator pitches, rudder yaws — and the stall is an angle-of-attack event at any speed.
- HIGH-SPEED flight brings compressibility: the critical Mach number is where the local airflow first reaches Mach 1; beyond it shock waves form and drag rises sharply. Swept wings raise the critical Mach and delay the effect.
- ROTARY-WING: a helicopter rotor is a set of rotating wings. The COLLECTIVE changes the pitch of ALL blades together to vary total rotor thrust (climb/descend); the CYCLIC tilts the rotor disc to move the aircraft horizontally.
- The main rotor's torque reaction tends to spin the fuselage the opposite way; a TAIL ROTOR (or NOTAR/fenestron) provides anti-torque and yaw (directional) control.
- In forward flight the advancing blade sees more airflow than the retreating one — 'dissymmetry of lift' — corrected by blade FLAPPING; retreating-blade stall ultimately limits a helicopter's forward speed.
- ⚠ Exam trap: on a helicopter the COLLECTIVE changes all blades' pitch together (total lift) while the CYCLIC tilts the disc for direction; the TAIL ROTOR counters main-rotor torque and gives yaw control.
- Lift
- L = C_L·½·ρ·V²·S
A helicopter pilot raises the collective lever. What happens to the rotor, and what secondary effect must be countered?
Raising the collective increases the pitch of all main-rotor blades simultaneously, increasing total rotor thrust so the helicopter climbs (with a matching power/RPM adjustment). The extra power increases the torque reaction trying to yaw the fuselage, so more anti-torque (tail-rotor) thrust — via the pedals — is needed to hold heading.
Lift, angle of attack & the stall
FreeThe four forces in flight
ProThis simulation is part of Engineer
Upgrade to unlock every quiz, mock exam and advanced simulation across all modules. Notes and mind maps stay free.
Theory of flight concept map
FreeTheory of Flight
Theory of flight quiz
FreeTheory of Flight — quiz
1. On a helicopter, the collective control changes:
2. The cyclic control:
3. The tail rotor provides:
4. 'Dissymmetry of lift' in forward flight is caused by:
5. A helicopter's maximum forward speed is ultimately limited by:
6. Fixed-wing ailerons control:
7. A stall occurs when the wing exceeds its:
8. The critical Mach number is where: