Meteorology
This domain tests weather knowledge for low-level helicopter operations: pressure, density altitude, wind, turbulence, icing, fog, thunderstorms, fronts and METAR/TAF interpretation.
Core concepts
QNH is pressure reduced to mean sea level; QFE is pressure at the aerodrome. Density altitude rises with high elevation, high temperature, high humidity and low pressure. Wind shear and microbursts are dangerous near showers. Mechanical turbulence is worst over rough terrain and buildings; mountain waves produce downdraughts. Icing can occur in supercooled cloud; helicopters are particularly vulnerable at low level. Fog forms when temperature approaches dew point.
Worked example
Decode: METAR DNMM 121200Z 21012KT 9999 SCT020 30/24 Q1012. Wind 210° at 12 kt; visibility 10 km or more; scattered cloud at 2,000 ft; temperature 30°C, dew point 24°C; QNH 1012 hPa. The spread is 6°C, so mist or fog is not imminent, but a cooling trend or rising dew point would reduce the margin.
Traps
Using QFE where QNH is required; confusing temperature/dew-point spread with cloud base; ignoring density altitude; and treating a TAF as an observation rather than a forecast.