Aircraft General Knowledge (Airframe, Systems, Powerplant)
What the exam tests
This domain checks your understanding of airframe structure, flight controls, fuel, electrical, pitot-static, vacuum, hydraulic, and powerplant systems on light training aircraft, with emphasis on system failures and limitations.
Core rules
- A typical CPL trainer such as the C172S uses a Lycoming IO-360-L2A: horizontally opposed, air-cooled, fuel-injected, direct-drive engine rated at 180 hp at 2,700 rpm.
- Dual magnetos are independent of the electrical system; the engine keeps running after an alternator failure. The battery then supplies radios and lights for a limited time.
- Fuel: 56 US gal total, 53 US gal usable. Fuel injection reduces carburettor icing but does not eliminate induction icing.
- Pitot heat protects the pitot tube; the static port is separate. Blocked static causes airspeed to read high in a climb and low in a descent.
- The engine-driven vacuum pump supplies the attitude and heading indicators; failure leaves the turn coordinator and electric instruments.
Worked example
During run-up, selecting the right magneto gives a 150 rpm drop and the left gives 50 rpm. The maximum permitted drop is 175 rpm and the maximum difference between magnetos is 50 rpm. The difference is 100 rpm, so the run-up is unsatisfactory: reject the aircraft and have the ignition system inspected.
Traps
A 175 rpm drop on both magnetos is acceptable only if the difference is within 50 rpm. Do not assume fuel injection means no icing risk. Do not reset a popped circuit breaker more than once without maintenance advice.