Aircraft Systems
Aircraft systems tests fuel, oil, electrical, hydraulic, pneumatic, ice and rain protection, and fire protection - mainly the checks, indications and failure actions.
Fuel and oil
- Avgas 100LL is blue; Jet A-1 is kerosene for turbines. Check grade, quantity and contamination by sumping every drain before flight.
- Tanks are vented; unporting can occur in slips, uncoordinated flight or with low fuel. Know the selector positions and any “both” limitation.
- Oil systems are usually dry-sump: pressure pump, scavenge pump, cooler and filter. Low oil pressure is a land-as-soon-as-practicable item, not a gauge to ignore.
Electrical, hydraulic and pneumatic
- Battery for start and emergency; alternator or generator through the master switch, bus and circuit breakers. Monitor ammeter or loadmeter.
- Hydraulics: reservoir, engine-driven pump, relief valve and accumulator; check pressure and fluid before flight.
- Pneumatics: engine-driven vacuum pump supplies gyros; normal suction is about 4.5–5.5 inHg.
Ice, rain and fire
Carburettor heat melts induction ice; alternate air does the same for injected engines. Pitot heat, de-ice boots, TKS fluid and windscreen heat protect against ice and rain. Fire protection uses detectors, a bottle and a fuel shut-off; learn the memory items.
Worked example
A 28 V, 70 A alternator supplies 1,960 W. Continuous loads of landing light 10 A, pitot heat 7.5 A, avionics 12 A, fuel pump 5 A and interior lights 3 A total 37.5 A - about 54% load. If the alternator fails, a 20 Ah battery at that load lasts about half an hour, so shed non-essential loads immediately.
Traps
- Leaving the selector on a tank that can unport.
- Using carburettor heat to cure roughness caused by detonation.
- Reading the suction gauge as pressure.
- Forgetting the fire bottle gives one limited shot.