Aircraft General Knowledge - Airframe, Systems and Powerplant
This domain tests the airframe, hydraulic, electrical, fuel, ice-protection and piston-engine systems, plus the propeller. Questions often ask what happens after a failure, so learn system purpose and redundancy rather than isolated component names.
Structure and loads
Light aircraft use semi-monocoque construction: skin carries stress, stringers and frames stiffen it, and spars carry wing bending. Limit load is the maximum expected in service; ultimate load is normally 1.5 times limit load, above which structural failure is possible. Inspect for corrosion, loose rivets, cracks and composite delamination.
Systems
Hydraulics: reservoir, engine-driven pump, accumulator, pressure-relief valve, selector and actuators. The accumulator smooths pulses and gives limited emergency pressure; it is not a continuous source. Electrics: battery, alternator, voltage regulator, buses and circuit breakers. The battery is a short-term reserve. Fuel: tanks, selector, strainer, primer and drain points; check for water and contamination before flight.
Powerplant
A four-stroke piston engine needs the correct mixture, ignition timing and cooling. Detonation is uncontrolled explosive combustion after normal ignition, caused by high manifold pressure, high temperature or weak mixture. Pre-ignition is ignition before the spark, often from a hot spot. A constant-speed propeller governor maintains RPM by changing blade angle; if the governor fails, the propeller usually goes to fine pitch and RPM rises.
Worked example
In cruise, the ammeter shows discharge and the alternator warning light is on. The battery is supplying the bus. Action: reduce electrical load, keep the battery for essential equipment, notify ATC and plan to land at the nearest suitable aerodrome. Do not assume the alternator will reset; the battery endurance is limited.
Traps
Believing the accumulator gives continuous hydraulic pressure; confusing detonation with pre-ignition; forgetting carburettor ice can occur at positive outside air temperatures; ignoring magneto drop limits.