Aircraft and Principles of Flight
This domain tests the aircraft knowledge a controller needs: wake turbulence behaviour and categories, performance limitations that shape clearances, and basic principles of flight behind phrases such as "unable due performance".
Wake turbulence
- Wingtip vortices form whenever a wing generates lift; they are strongest when the aircraft is heavy, clean and slow - takeoff and early climb, and late final approach.
- Vortices sink roughly 300–500 ft/min and drift with the wind; in calm conditions they persist near the flight path, which is the worst case for a following aircraft.
- Controllers apply wake separation minima in addition to the standard separation and issue cautionary wake turbulence information where the minima are not applied.
Categories
- By maximum certificated take-off mass: Light up to 7000 kg, Medium 7000 to 136 000 kg, Heavy 136 000 kg or more, plus the Super category for the A380.
- Aircraft in the Heavy and Super categories include "Heavy" or "Super" in the radiotelephony callsign.
- Typical radar minima: 4 NM Heavy behind Heavy, 5 NM Medium behind Heavy, 6 NM Light behind Heavy, 5 NM Light behind Medium. Time-based departure minima are commonly 2 minutes, extended to 3 minutes for a Light or Medium departing behind a Super or Heavy from an intermediate point.
Performance and principles
- V speeds: V1 decision, VR rotation, V2 takeoff safety, VREF reference approach speed, VNE never-exceed.
- Density altitude raises true airspeed and takeoff distance and reduces climb performance; hot, high and humid is the worst combination.
- Load factor rises steeply in turns; stall speed increases with the square root of load factor, and swept wings stall at the tips first.
- Contaminated runways reduce braking action and can cause hydroplaning.
Worked example
A Light aircraft is cleared to take off behind a departing Heavy from the same runway. Reasoning: the Heavy's vortices will sink behind its rotation point. Minimum radar wake separation is 6 NM; for departure, the Light must wait 3 minutes and should lift off before the Heavy's rotation point and stay above its flight path.
Traps
Forgetting that calm wind maximises vortex hazard; assuming vortices stay at the Heavy's altitude; applying wake minima only to arrivals; ignoring "unable due performance" as a legitimate refusal.