Aircraft General Knowledge: Airframe, Systems, Electrics, Powerplant and Emergency Equipment
Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment - asks what a system does, how it fails, and what the flight deck shows when it does. Ghana ATPL questions are strong on system architecture (how many sources, what feeds what) and on the practical consequence of a single failure.
Airframe
- Modern transports are semi-monocoque: stressed skin carries shear, stringers and frames stiffen it, spars and ribs carry wing bending. Fail-safe designs use multiple load paths; safe-life components are retired at a fixed life; damage tolerance adds scheduled inspection.
- Pressurisation is controlled by the outflow valve; cabin altitude is normally held at or below 8 000 ft, with pressure-relief and negative-pressure relief valves protecting the structure.
Electrics and hydraulics
- A typical transport generates 115 V AC 400 Hz from engine-driven IDGs, 28 V DC from transformer-rectifiers and batteries, and keeps a battery bus for essential loads. An IDG fault is cleared by a drive disconnect which is not reset in flight.
- Hydraulics run at about 3 000 psi, with engine-driven and electric pumps, accumulators to absorb surges and supply brief demand, and a power transfer unit that pressurises one system from another without transferring fluid.
Powerplant and emergency equipment
- Gas turbine thrust is scheduled on N1 (or EPR); EGT is the life-limited parameter. Bleed air is taken from HP/IP compressor stages for air conditioning and anti-ice.
- Fire detection uses loop sensors; Halon 1301 is used for engines and cargo, water glycol for cabin fires. Emergency equipment includes escape slides, a 406 MHz ELT, PBE, portable oxygen, crash axe and first-aid kits.
Worked example
A crew loses the engine-driven pump on hydraulic system 1. Pressure falls from 3 000 psi to about 2 900 psi, then drops sharply. The accumulator, precharged to roughly 1 000 psi, supplied the shortfall until system pressure reached precharge; below that it gives nothing. The correct conclusion is that the remaining pressure was stored energy, not pump output - the fault is the pump, not the accumulator.
Traps
Assuming an IDG can be reconnected in flight; confusing the PTU (pressure only) with a fluid transfer; thinking the electric pump replaces full system flow; and forgetting that EGT limits are usually the first exceeded at high altitude.