Aircraft General Knowledge and Principles of Flight
This domain splits into two halves: the machine (airframe, powerplant, systems, instruments) and the physics that keep it flying (forces, stability, control and the phenomena that limit performance).
Powerplant and systems
A four-stroke piston engine produces power on the firing stroke; dual magnetos give independent ignition and are checked at run-up. Carburettor icing is most likely with high humidity and temperatures roughly between −5°C and +20°C, and can occur on a warm humid day at low power. Lean the mixture as density altitude rises. Turbine engines are monitored by N1/N2 and EGT. Pressurisation is controlled by the outflow valve; anti-icing prevents ice forming, de-icing removes it after it forms.
Flight instruments
Pitot-static: a blocked pitot leaves the ASI behaving like an altimeter; a blocked static makes the ASI over-read in a climb. The VSI lags. Gyroscopic instruments rely on rigidity in space and precession: the attitude indicator and heading indicator are rigidity instruments, the turn coordinator shows rate of turn, not angle of bank. The magnetic compass suffers turning and acceleration errors (ANDS: accelerate north, decelerate south) and dip near the poles.
Principles of flight
Lift = ½ρV²SCL. The critical angle of attack (about 15–18° for most aerofoils) is fixed: the wing stalls at that angle whatever the speed, weight or attitude. Induced drag falls with speed while parasite drag rises; their sum is minimum at L/Dmax, which is also best glide speed. Flaps raise CL and drag; stability is positive static plus positive dynamic, in pitch, roll and yaw. Propeller effects include torque, slipstream, asymmetric blade effect (P-factor) and gyroscopic precession.
Worked example
An aircraft stalls at 60 kt in level flight. In a 60° bank, load factor n = 1/cos 60° = 2.0. Stall speed scales with √n = 1.41, so the accelerated stall speed is 60 × 1.41 ≈ 85 kt. Pulling harder to hold altitude in the turn therefore stalls it at a much higher IAS.
Traps that cost marks
Confusing angle of attack with pitch attitude; thinking stall speed is fixed; quoting IAS when the question means TAS; and assuming the turn coordinator shows bank angle.