Synopsis

A European air navigation service provider (ANSP) has reported a recent spate of level bust incidents attributed to incorrect altimeter setting during climb out. Essentially, some flights crews are not changing from the aerodrome QNH to the standard pressure setting (1013.2 hPa) as the aircraft climb resulting in aircraft ‘busting’ the cleared flight level given by ATC. For instance, if aerodrome QNH is 993 hPa, not changing to 1013.2 hPa will result in an aircraft climbing 600 feet above its cleared flight level.

ICAO Provisions

ICAO Doc 8168 – Procedures for Air Navigation Services – Aircraft Operations (PANS-OPS), Volume I, Flight Procedures – Part VI – Altimeter Setting Procedures – Chapter 3.3.3 “On climbing through the transition altitude, the reference for the vertical position of the aircraft shall be changed from altitudes (QNH) to flight levels (1013.2 hPa), and thereafter the vertical position shall be expressed in terms of flight levels.”