Aeroplane Aerodynamics, Structures and Systems
What the module tests
This module covers airframe structures, flight controls, hydraulics, landing gear, pneumatics, air conditioning, pressurisation, fuel, electrical power, lights, oxygen, ice and rain protection, and water/waste. Questions link system purpose to component function and failure effect.
Core rules
- Cabin pressurisation uses bleed air and an outflow valve; differential pressure is cabin pressure minus external pressure.
- Hydraulic systems use pressure, flow and return lines; a priority valve protects essential services.
- Landing gear sequencing uses up-locks, down-locks and squat switches; a weight-on-wheels signal inhibits retraction on the ground.
- Fuel is managed by pumps, valves and vents; imbalance and unporting are certification concerns.
- Ice protection may be anti-icing (prevent) or de-icing (remove); bleed-air thermal systems are common on transport aircraft.
- Structure types include monocoque, semi-monocoque and stressed skin; fail-safe and damage-tolerance principles govern inspection.
Worked example
An aircraft cruises at 35,000 ft where ambient pressure is about 3.46 psia. The cabin is held at 8,000 ft, about 10.9 psia. Find the differential pressure. Differential = cabin pressure - ambient pressure = 10.9 - 3.46 = 7.44 psi. The outflow valve modulates to hold this differential within the structural limit. If the cabin altitude rises, the differential falls; if the outflow valve closes too far, differential rises toward the relief-valve setting.
Traps
Mixing absolute and differential pressure; assuming cabin altitude equals aircraft altitude; ignoring squat-switch inhibition; confusing anti-icing with de-icing; forgetting that a hydraulic priority valve may drop a non-essential service.
Exam approach
For system questions, trace supply, control and indication. For pressurisation, always subtract ambient from cabin pressure.