Piston and Turbine Powerplants, Propellers
What this domain tests
This domain covers piston and turbine powerplants and propellers: cycles, mixture and detonation, turbine limits, and propeller control.
Core rules
- A four-stroke piston engine has intake, compression, power, and exhaust strokes. The mixture is set by fuel flow versus airflow; detonation is uncontrolled explosive burning after ignition, while pre-ignition is ignition before the spark.
- Carburettor icing can occur at outside air temperatures well above freezing; carb heat bypasses the filter and warms the intake.
- A gas turbine follows the Brayton cycle: intake, compression, combustion, exhaust. N1 is fan or compressor speed; N2 is core speed; EGT is a limit parameter. Compressor surge is a reversal of flow, often caused by a disturbed inlet.
- A constant-speed propeller uses a governor to vary blade angle and keep rpm constant; feathering aligns blades with the relative wind; beta range controls pitch on the ground; reverse thrust is blocked in flight.
Worked example
A propeller has a geometric pitch of 2.0 m and turns at 2,400 rpm. Ideal advance per second = 2.0 × (2,400/60) = 80 m/s = 288 km/h. At 85% efficiency, true airspeed ≈ 0.85 × 288 = 245 km/h. The reasoning shows why pitch and rpm set the no-slip speed, and slip reduces it.
Traps
Confusing detonation with pre-ignition; assuming carb ice needs freezing temperatures; using N2 for thrust on a high-bypass engine; treating geometric pitch as true airspeed; forgetting that beta and reverse are ground ranges.