Aircraft General Knowledge (Airframe, Systems, Powerplant, Instruments)
What the exam tests
This domain tests practical system knowledge for the PPL: how the airframe carries load, how power and fuel systems work, and how pitot-static and gyroscopic instruments fail.
Core rules
- A semi-monocoque fuselage carries load through stressed skin, stringers, frames and spar attachments. Inspect for corrosion, loose fasteners, cracks and drain blockage.
- A four-stroke engine produces power on the power stroke; the mixture control sets fuel/air ratio, and excessively lean mixture raises cylinder temperature. Carburettor icing can occur at outside air temperatures well above freezing, especially with high humidity.
- Magnetos are independent ignition sources; a mag check confirms both operate. A constant-speed propeller maintains selected RPM by changing blade angle.
- The pitot-static system feeds the airspeed indicator, altimeter and vertical speed indicator. The altimeter subscale must be set to QNH for elevation, QFE for height above a datum, or standard pressure for flight levels.
- Gyroscopic instruments depend on rigidity in space and precession; suction or electrical failure can make them unreliable.
Worked example
On climb with the pitot tube blocked but the static port open, trapped pitot pressure stays fixed while static pressure falls. The pressure difference increases, so the airspeed indicator overreads. In descent the same blockage causes underreading. The correct response is to cross-check attitude, altimeter and power, and fly known pitch and power rather than trust the ASI.
Traps
Confusing indicated, calibrated and true airspeed; leaving the altimeter on QFE when crossing to flight levels; assuming carburettor ice needs freezing air; ignoring a magneto drop; and treating a gyro instrument as reliable after a suction failure.