CPL Meteorology · Mock exam

A pilot sets QNH 1028 hPa at an aerodrome with an elevation of 850 ft. Flying the circuit at 1000 ft AGL, what altitude should the altimeter read, and why is QNH the correct altimeter setting for this purpose?

• A.The altimeter reading is irrelevant at circuit height — pilots rely on visual reference to the runway threshold and altimeters are only used above 3000 ft AGL
• B.The altimeter reads 1000 ft because QNH is calibrated to read zero at the aerodrome threshold; QNH shows height above the runway directly and requires no arithmetic
• C.The altimeter reads 1850 ft because QNH sets it to read altitude above mean sea level, matching chart elevations; this is standard below transition altitude in Australia
• D.The altimeter reads 0 ft because the standard setting of 1013.25 hPa removes all reference to aerodrome elevation and standardises readings across all aircraft