Aircraft General Knowledge - Airframe, Systems, Electrics, Power Plant and Emergency Equipment
Structure
Most light aircraft use semi-monocoque stressed-skin construction: the skin carries part of the load, stringers and frames stabilise it, and spars and ribs form the wing box. Longerons and bulkheads carry concentrated loads.
Systems
Hydraulic systems comprise reservoir, pump, accumulator, relief valve and selector; the accumulator smooths demand and gives limited emergency pressure. Pneumatic vacuum pumps drive the gyros. The fuel system runs from tanks through a selector, strainer and pump to the carburettor or injector.
Electrics
The battery is for starting and emergency supply; in normal flight the alternator or generator carries the load and charges the battery. A voltage regulator protects the system, and the bus bar distributes power. Load shedding protects the essential bus when a generator is lost.
Powerplant and emergency equipment
Four-stroke cycle: induction, compression, power, exhaust. Two magnetos provide independent ignition. Fire detection uses heat or smoke sensors; extinguishers are CO2, dry powder or Halon. Emergency equipment includes fixed oxygen, a 406 MHz ELT, life jackets, escape hatches and a crash axe.
Worked example
Carburettor icing: OAT 5°C, relative humidity 70%, descending at low power. The venturi and throttle pressure drop can cool the charge by 20–25°C, taking the mixture below 0°C, so ice forms on a mild day. Apply full carburettor heat; expect a temporary further power loss as melted ice passes through the engine, then set the mixture as the checklist requires.
Traps
Assuming the battery runs the avionics in cruise; forgetting that carburettor heat enriches the mixture; confusing the vacuum system with the electrical system; ignoring the magneto drop limits (typically 150 rpm maximum and 50 rpm between magnetos).