Altimeter Setting Procedures

Description

The aircraft altimeter barometric sub-scale must be set to the appropriate setting for the phase of flight. These are:

  • Flight level. Standard pressure setting (1013 hPa) is set when flying by reference to flight levels above the transition altitude;
  • Altitude. Regional or airfield pressure setting (QNH) is set when flying by reference to altitude above mean sea level below the transition level;
  • Height. Altimeter pressure setting indicating height above airfield or touchdown (QFE) is set when approaching to land at airfield where this procedure is in use.

Failure to set the appropriate barometric sub-scale pressure setting may result in a significant deviation from the cleared altitude or Flight Level

Altimeter Setting Error (example)

Types of Altimeter Setting Error

  • The pilot mishears the transmitted pressure setting and sets an incorrect figure.
  • The pilot hears the transmitted pressure setting correctly but fails to set it or mis-sets it.
  • The pilot fails to change the pressure setting at the appropriate point in a departure, climb, descent or approach.

Threatss

Mitigations

  • The existence of appropriate SOPs for the setting and cross-checking of altimeter sub scales and their strict observance is the only universal primary solution to eliminate incorrect altimeter setting.
  • Use of the aircraft radio altimeter to monitor the aircraft proximity with the ground can help to improve situational awareness provided that the flight crew are generally familiar with the terrain over which they are flying;
  • GPWS/GPWS/TAWS provide a safety net against CFIT and, in the case of TAWS Class 'A' with its option of a simple terrain mapping display, it can also be used to directly improve routine situational awareness.
  • Strict adherence to the verification of pressure-altitude-derived level procedure by ATC. This should be done at least once by each suitably equipped ATC unit. The check is performed by comparing the level received from surveillance sources with a voice report by the pilot.

Accidents and Incidents

Events in which the incorrect altimeter pressure setting was either a cause or contributing factor in a Level Bust or CFIT/near CFIT:

Related Articles

Further Reading

ICAO

Flight Safety Foundation ALAR Toolkit

EUROCONTROL Level Bust Toolkit

UK CAA

Airbus Briefing Notes

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