Meteorology
Atmosphere and weather systems
Know the standard atmosphere, pressure and density altitude, and how temperature and humidity reduce performance. Understand the formation of clouds, fronts (cold, warm, occluded), and the weather associated with each. Learn about stability, lapse rates, and the conditions that produce thunderstorms, icing and turbulence. For helicopters, low-level wind shear, mountain waves and dust devils are particularly relevant.
Local and hazardous weather
Know the difference between a METAR (observed) and a TAF (forecast), and how to read both. Understand fog formation (radiation, advection, upslope) and the conditions that dissipate it. Learn the hazards of icing: carburettor icing can occur at temperatures well above freezing, and airframe icing is a serious risk for helicopters without de-icing equipment. Understand wind gradient and the behaviour of wind around obstacles and in confined areas.
Traps in questions
Questions often give a temperature and dew point and ask about fog: a small spread (2-3 °C) suggests fog risk. Another trap is confusing QNH and QFE, or asking for density altitude without accounting for humidity. Watch for questions about mountain flying where the correct answer is the windward versus leeward side.
Worked example
Rule of thumb: density altitude rises about 120 ft for each 1 °C above standard temperature at a given pressure altitude. If the field is at 3 000 ft pressure altitude and 15 °C above standard, expect a density altitude near 4 800 ft, with a corresponding loss of hover performance.