Aircraft Technical: airframes, engines, systems and instruments
Domain 1 - Aircraft Technical: airframes, engines, systems and instruments
This domain tests the PPL candidate's understanding of how a light aircraft is built and how its systems behave in flight. Questions are practical: identify a system, interpret an indication, or explain a limitation.
Airframe and piston engine
- Semi-monocoque structures carry flight and landing loads through skin, stringers, frames and bulkheads. Inspect for cracks, corrosion, loose rivets and blocked drain holes.
- A four-stroke piston engine runs induction, compression, power and exhaust. The mixture control sets fuel/air ratio; best power is richer than best economy.
- Carburettor icing is most likely at outside air temperatures roughly between -10°C and +25°C with high humidity. Apply carburettor heat, expect an rpm drop, and use it before ice forms.
- Detonation is explosive combustion after normal ignition; pre-ignition is ignition before the spark. Both cause roughness and high cylinder head temperature. Reduce power, enrich the mixture and lower temperature.
Systems and instruments
- Electrical system: battery, alternator or generator, bus and master switch. An ammeter or loadmeter shows charge or discharge; it does not show battery capacity.
- Pitot-static instruments: ASI uses pitot total pressure and static pressure; altimeter uses static pressure; VSI uses rate of change of static pressure.
- If the static port blocks, the altimeter freezes, the VSI reads zero, and the ASI under-reads in a climb and over-reads in a descent because trapped static pressure is compared with changing pitot pressure.
- Gyroscopic instruments: attitude and heading indicators are usually vacuum-driven; the turn coordinator is usually electric. The vacuum gauge shows suction, not pressure.
Worked example
An aircraft climbs with a blocked static port. Altimeter: stuck at the blocked altitude. VSI: zero. ASI: under-reads because trapped static pressure is higher than the outside static pressure, reducing the indicated pressure difference. The correct response is to use the alternate static source, if fitted, and fly attitude/power.
Traps
Confusing suction with pressure; assuming a turn coordinator is vacuum-driven; ignoring carburettor icing at low power; using cruise performance figures without density altitude; treating an ammeter as a battery charge gauge.