What happened
On 11 June 2006, a Dornier 328-100, registration TF-CSB, was conducting a passenger charter flight from Aberdeen to Sumburgh Airport in the Shetland Isles. During the approach, the flight crew attempted a visual landing on Runway 15. As the aircraft descended, it encountered thickening haze, which reduced visibility and obscured the coastline.
While navigating toward a waypoint, the aircraft's descent rate increased significantly. The crew, believing they were flying a safe path, did not realize they were tracking toward the high ground of Fitful Head. The aircraft's Enhanced Ground Proximity Warning System (EGPWS) triggered multiple alerts, including "CAUTION TERRAIN" and "TERRAIN TERRAIN PULL UP." Despite these warnings, the commander did not initiate a maximum performance climb, instead increasing the turn rate to avoid what he perceived as the edge of the headland. The aircraft flew at an altitude of less than 400 ft near the terrain before eventually turning toward the airport and completing a safe landing.
The investigation
The AAIB investigation focused on the crew's mental model of the approach and the lack of effective communication between the pilots. The investigation examined the aircraft's EGPWS data, radar tracks, and radio transmissions. It was established that the commander's briefing for the approach was inconsistent with the co-pilot's understanding, leading to an incorrect perception of the aircraft's position relative to the terrain. The investigation also reviewed the operator's training manuals and the regulatory oversight provided by the Icelandic Civil Aviation Administration.
Findings
- The crew maintained an incorrect mental model of their position relative to Fitful Head.
- A steep authority gradient existed between the highly experienced commander and the relatively inexperienced co-pilot, which prevented the co-pilot from effectively challenging the commander's actions.
- The aircraft's descent rate was high, and the crew failed to respond to the EGPWS "PULL UP" warnings with the required maximum climb procedure.
- There was a lack of specific training and company guidance regarding the predictive "look ahead" functions of the EGPWS.
- The operator's manuals contained discrepancies regarding descent limitations and lacked a formal system for certifying terrain briefings for Category B aerodromes.
Safety action
- The Icelandic Civil Aviation Administration issued a Flight Crew Notice (FCN) to provide guidance on responding to GPWS warnings.
- The operator committed to updating its Operations Manual to include better guidance on descent rates and terrain briefings.
- The ICAA increased its oversight of the operator's crew conversion training programs.