Aircraft General Knowledge: Airframe, Systems and Powerplant
Airframe and flight controls
Understand primary structure - fuselage, wing, empennage, landing gear - and how loads flow through spars, ribs, and skin. Know the difference between a semi-monocoque and a truss structure, the purpose of stringers and frames, and the meaning of fail-safe, safe-life, and damage-tolerant design. For controls, know what each surface does: ailerons roll, elevator pitches, rudder yaws, flaps increase lift and drag, spoilers destroy lift and add drag, and trim relieves control force. Know the difference between a servo tab, balance tab, and anti-balance tab.
Hydraulics, pneumatics, electrics
Know that hydraulic systems use a reservoir, pump, accumulator, filters, relief valve, and selector valves; the accumulator smooths demand and provides emergency reserve. Understand that pneumatics supply anti-ice, pressurisation, and engine starting on many types. For electrics, know the difference between AC and DC buses, the role of the generator/alternator, battery, and bus-tie, and what happens on a bus failure.
Pressurisation and fuel
Know the meanings of cabin altitude, differential pressure, outflow valve, and the safety valves; the maximum differential pressure limits cabin altitude at high flight levels. For fuel, know the tanks, boost pumps, crossfeed, jettison, and the difference between usable and unusable fuel.
Powerplant
For turbine engines, know the compressor, combustion chamber, turbine, and accessory gearbox; understand N1 and N2, EGT, EPR, and what they indicate. For piston engines, know the four-stroke cycle, carburettor icing, and mixture control. Traps include confusing N1 (fan/low-pressure spool) with N2 (high-pressure spool), and confusing anti-ice with de-ice.
Worked example
If maximum cabin differential pressure is 8.0 psi and cabin altitude must not exceed 8,000 ft, then at a cruise altitude where ambient pressure is 3.0 psi, the maximum cabin pressure is 11.0 psi; a cabin altitude of 8,000 ft corresponds to about 10.9 psi, so the limit is just satisfied - the outflow valve controls the cabin altitude, not the differential directly.