Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment
What the exam tests
This domain covers transport-category airframes: structural loads and fail-safe design, flight controls, pressurisation, fuel, hydraulics, electrical generation/distribution, powerplant and fire/oxygen equipment. Expect system-logic questions, not type ratings.
Core rules
- Fail-safe vs safe-life: fail-safe structures use multiple load paths and crack-stopping features; safe-life components are retired before predicted failure.
- Pressurisation: the outflow valve controls cabin altitude; the cabin pressure controller schedules climb; negative pressure relief protects the fuselage.
- Electrical: 115 V AC 400 Hz is generated by IDGs; TRUs supply 28 V DC; batteries are the last-resort DC source for essential buses. Non-essential loads are shed automatically.
- Hydraulics: engine-driven pumps, electric pumps, PTU/RAT; check pressure, quantity and temperature after failure.
- Fire: detection loops, extinguisher bottles, isolation of fuel/hydraulic/electrical sources.
Worked example
Left IDG fails in cruise. The generator control unit trips the generator offline; the bus tie closes and the right IDG supplies both AC buses, while the battery/essential DC bus remains available through TRUs. If the right IDG then fails, the APU generator or emergency RAT (if installed) restores AC. The reasoning is priority: keep essential buses alive, shed galley and utility loads, then land at the nearest suitable aerodrome.
Traps
Assuming the battery can power all AC loads; forgetting the RAT is not available at low speed; confusing a hydraulic PTU with an electric bus tie; treating a fire warning as a confirmed fire without checking the other loop; missing that fuel imbalance can affect CG and roll control.