What happened
On 3 December 2005, a McDonnell Douglas MD-11, registration N701GC, was conducting a commercial cargo flight from Cologne (Bonn) to Nottingham East Midlands Airport. During the approach, the crew received updated ATIS information indicating a change in the local pressure (QNH) from 973 mb to 974 mb. Although the crew acknowledged this change, they failed to update the pressure settings on any of the aircraft's three altimeters.
As the aircraft descended to 2,000 ft, the crew became preoccupied with a lateral navigation issue when the autopilot began turning the aircraft away from the localiser centerline. While the crew focused on correcting the heading, they neglected to complete the remaining items of their 'Descent/Approach' checklist. Consequently, the altimeters remained set to the standard 1013 mb pressure.
At approximately 7 nm from the runway, an Air Traffic Controller noticed the aircraft appeared lower than expected on radar and initiated an altitude check. The radar recording revealed the aircraft was maintaining an altitude of approximately 918 ft amsl, which was more than 1,000 ft lower than the cleared altitude. The error was identified and corrected after the controller questioned the altimeter setting, and the aircraft landed safely without further incident.
The investigation
The AAIB investigation, supported by a company inquiry, utilized radar recordings from the National Air Traffic Services and radio telephony recordings from East Midlands ATC. The investigation established that the crew had completed the initial portion of their checklist but had been distracted by a navigation problem, leading them to omit the altimeter updates. The investigation also noted that the aircraft was not equipped with an automated radar altimeter callout feature, which might have otherwise alerted the crew to the discrepancy.