Aircraft General Knowledge - Airframe, Systems and Powerplant
What the exam tests
This section covers airframe structures and flight controls, hydraulic and electrical systems, fuel, ice and rain protection, pressurisation, piston and turbine powerplants, and propellers. Questions test system purpose, normal indications and the first correct response to a malfunction.
Core rules
- The airframe carries flight, ground and pressurisation loads; primary structure includes spars, ribs, stringers and skins.
- Hydraulic systems actuate landing gear, flaps, brakes and some flight controls; pressure and quantity are separate indications.
- The electrical system normally has an engine-driven alternator/generator, battery and busbars; losing the alternator leaves the battery as a limited source.
- Piston engines need fuel, air, ignition and compression; carburettor icing can occur at outside air temperatures well above freezing.
- A constant-speed propeller governor changes blade angle to hold selected RPM as power or airspeed changes.
Worked example
On a cool, humid day at reduced power, RPM falls and the engine runs rough. Carburettor heat is applied: RPM initially drops further, then rises and roughness decreases. Reasoning: the initial drop is richer mixture after heat is applied; the later rise is ice melting and the carburettor returning to normal. Leave carburettor heat on until certain the ice has cleared, and expect reduced power while heat is selected.
Traps
Using carburettor heat as a cure-all without recognising its power penalty; leaning the mixture excessively at high power; confusing alternator failure with battery depletion; assuming hydraulic quantity indicates pressure.