Aircraft General Knowledge - Powerplant (Turbine and Piston Engines)
What you must understand
For turbine engines: the Brayton cycle in plain terms - intake, compression, combustion, exhaust - and how thrust is produced by momentum change. Know the compressor types (axial, centrifugal), the purpose of variable stator vanes and bleed valves to avoid surge, combustion chamber types, turbine blade cooling, and the accessory gearbox. Understand the meaning of EPR versus N1 as thrust parameters, and why N2 and EGT are monitored. Know the starting sequence, ignition systems (including the difference between continuous and intermittent ignition), and the function of the fuel control unit and its scheduling of fuel against throttle and compressor conditions.
For piston engines: the four-stroke cycle, valve timing and overlap, the difference between rich and lean mixture effects on power and temperature, detonation versus pre-ignition, carburettor icing (and why it occurs at moderate ambient temperatures with high humidity), and the function of the magneto. Understand the purpose of the dual ignition system and why a magneto check reveals a faulty plug or lead. Know propeller fundamentals: blade angle, pitch, constant-speed units and feathering.
Traps
Candidates mix up detonation (uncontrolled explosion after ignition) with pre-ignition (ignition before the spark). Questions often test that carburettor icing can occur at outside air temperatures well above freezing.
Worked example
If a magneto check shows a larger-than-normal RPM drop on one magneto, the fault lies in that magneto's circuit - plug, lead or the magneto itself - not the engine as a whole. If both drops are equal but excessive, suspect timing or a general ignition problem.