Aircraft General Knowledge - Airframe, Systems and Powerplant
This domain tests how the airframe, hydraulic, pneumatic, electrical, fuel and powerplant systems work together, and how system failures affect handling and dispatch decisions.
Airframe and systems
- Primary structure carries flight, pressurization and landing loads; secondary structure is non-load-critical.
- Hydraulic systems power flight controls, gear, brakes and flaps; redundancy may be provided by multiple systems, a power transfer unit or an electric backup pump.
- Bleed air supplies pressurization and anti-ice; using bleed air reduces available engine thrust and raises EGT.
- Gas-turbine engines are monitored by N1, N2, EGT and fuel flow; FADEC schedules fuel and protects limits.
Worked example
A turbofan is at 85% N1 with EGT 20°C below limit. Selecting engine anti-ice increases bleed-air extraction. The FADEC adds fuel to maintain thrust, so EGT rises and available thrust falls. If EGT reaches its limit, the crew must reduce thrust or change configuration rather than ignore the indication.
Traps
- N1 and N2 are not interchangeable; N1 usually represents fan/low-pressure speed.
- EGT is a limit, not a target; sustained near-limit EGT accelerates hot-section damage.
- Not all hydraulic systems can supply all services after a failure.
- Bleed penalties affect takeoff and climb performance, especially at high altitude/high temperature.