Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment
The Aircraft General Knowledge paper tests how a light aeroplane is built and how its systems behave when you need them. Questions cover airframe structures, flight controls, fuel, oil, electrics, piston engines, propellers, instruments and emergency equipment. You must be able to explain a system, recognise a failure and state the correct immediate action.
Airframe and controls
Semi-monocoque stressed-skin construction carries loads through spars, ribs, stringers and skin. Control cables or pushrods link the yoke and pedals to ailerons, elevator and rudder; trim reduces control force. Flaps increase lift and drag at low speed. Gust locks must be removed before flight, and control continuity checked during the walk-around.
Powerplant and systems
A normally aspirated piston engine works on the four-stroke Otto cycle: induction, compression, power, exhaust. The carburettor mixes fuel and air; mixture control compensates for altitude. Dual magnetos provide independent ignition. The electrical system typically uses an engine-driven alternator to charge a battery and feed a bus through fuses or circuit breakers. Fuel must be checked for quantity, grade, water and contamination; the selector must be on a serviceable tank.
Emergency equipment
Know the location and use of the fire extinguisher, ELT, first-aid kit, life jackets and survival kit. The ELT transmits on 406 MHz to the COSPAS-SARSAT system and 121.5 MHz for local homing.
Worked example
During a run-up, left magneto drop is 120 rpm and right is 80 rpm; the difference is 40 rpm. If the AFM limit is 150 rpm maximum drop and 50 rpm maximum differential, the check is acceptable. If the engine runs rough, or the differential exceeds 50 rpm, shut down and have it investigated: a dead magneto or fouled plug can cause an in-flight ignition failure.
Traps
Do not confuse ammeter and voltmeter; do not assume the battery will carry a failed alternator indefinitely; do not lean aggressively at high power; do not ignore carburettor ice; and never treat the ELT as a substitute for a MAYDAY.