UK investigators have recommended a safety audit of Icelandic carrier City Star Airlines after a serious incident in which a Dornier 328 crew flew close to cliffs and failed to respond correctly to terrain warnings during an approach to Scotland's Sumburgh airport.
City Star Airlines suspended the 61-year-old captain involved and, after an internal investigation, asked him to resign.
The turboprop crew, operating to Sumburgh on the Shetland Islands from Aberdeen, had been planning a visual approach that involved heading north towards high coastal ground before turning right to line up with runway 15.
Although air traffic control had cleared the approach, weather conditions became hazy. As the aircraft descended from the sector safe altitude of 2,100ft (640m), it continued to fly towards high terrain despite neither crew member having visual contact with the headland.
"To maintain surface contact [the captain] needed to descend the aircraft to an unusually low level, considering the aircraft's distance from the airport," says the UK Air Accidents Investigation Branch. "If the commander actually intended flying towards the highest ground in the vicinity then it is remarkable that he continued to do so in conditions of poor and reducing forward visibility without informing air traffic control of the fact."
Data from the enhanced ground-proximity warning system shows the Dornier, tracking towards the cliff face, descended to around 630ft while less than 1nm (0.5km) from the point where terrain rises to 930ft.
Although the enhanced ground proximity warning system (EGPWS) issued a "pull up" alert - which normally demands a wings-level, maximum-performance climb - the captain responded with a right turn.
The AAIB suggested the crew was not fully aware of their location relative to the terrain. The aircraft came within 0.6nm of the high ground before tracking parallel to the line of the cliff, below the level of the cliff top, flying at a height of 400-600ft - low enough for the terrain to mask radar contact. The EGPWS continued after the turn and the landing-gear warning siren also sounded.
Shortly afterwards the aircraft landed safely at Sumburgh.
City Star Airlines flight safety officer Allan Chalmers says the captain, although experienced at flying to Sumburgh, "chose to ignore" the EGPWS warning, adding: "Ignoring this warning is against City Star's published procedures. He was suspended while we did our own investigation and subsequently was asked to resign."
Source: Flight International
