Aircraft General Knowledge - Airframe, Systems, Electrics and Powerplant
Aircraft General Knowledge
This domain tests how the airframe, powerplant and systems work together: the four-stroke cycle, fuel and ignition, carburettor ice, electrical supply, vacuum and pitot-static systems, flaps and landing gear. Expect system-failure reasoning rather than memorised diagrams.
Core rules
- Four-stroke cycle: induction, compression, combustion, exhaust. The camshaft opens valves; the magneto supplies ignition independently of the battery.
- Carburettor ice: most likely at 0–15°C with high humidity, and can occur at cruise power. Apply carburettor heat, expect an initial RPM drop, then a rise as ice clears; lean after the ice is gone.
- Mixture: lean for density altitude and cruise economy; enrich for climb and high power. An excessively lean mixture raises cylinder temperature.
- Electrics: the alternator carries the load and charges the battery. If the alternator fails, the ammeter shows discharge; shed non-essential load and land as soon as practical.
- Pitot-static: the pitot tube feeds the airspeed indicator; the static port feeds airspeed, altimeter and VSI. Blocked static causes altitude and airspeed errors.
Worked example
In cruise at 6,500 ft, you apply carburettor heat and the RPM drops about 150 and runs rough. That is consistent with carburettor ice. Keep carburettor heat on, accept the temporary roughness, and wait for smooth operation and RPM recovery; then readjust mixture. Do not immediately conclude the engine is failing.
Traps that cost marks
Using carburettor heat as a mixture control, or leaving it on during take-off, are common errors. Assuming both magnetos are needed for normal operation is wrong - the engine runs on either magneto, and the run-up checks each in turn. Confusing an alternator failure with a battery failure also loses marks: the battery can supply only limited time.