Investigators have criticised the captain of an Embraer EMB-120 Brasilia turboprop for allowing the aircraft to descend to just 475ft (216m) above water to highlight a safety point to a trainee first officer.
The French-registered aircraft was approaching the Isle of Man off the north-west UK mainland after a scheduled flight from Manchester with seven passengers and three crew, on 31 March last year. During preparations for approach to runway 08 at Ronaldsway airport, the captain realised that the aircraft's instruments were not tuned to the instrument landing system (ILS) frequency, but instead to the airport's VOR frequency.
The captain was training an inexperienced first officer and chose not to point out the error, or retune the ILS instrument to the correct frequency, to use the oversight to highlight safety issues.
At a distance of 5.2nm (9.6km) from the runway the captain initiated a descent until the aircraft was just 475ft above the surface of the sea but heading toward 600ft-high terrain only 1nm away. The aircraft's primary and secondary radar returns briefly vanished and air traffic controllers, concerned about the aircraft's height and position relative to high ground, contacted the crew to ask if they had the terrain in sight.
Once satisfied that the first officer had realised the ILS tuning error, the captain brought the turboprop back up to 1,600ft.
"Originally it was considered that the most likely reason for this incident was that the pilots had made a genuine mistake," says the Air Accidents Investigation Branch (AAIB). "However, later in the investigation the commander was insistent that he was fully aware of his actions, wishing to use the mistake as a training point for the first officer."
The AAIB says that the deliberate deviation potentially endangered the aircraft and "raises concerns" about the training and oversight of the flightcrew. The company involved has now ceased trading.
Investigators have studied a number of events during which aircraft have been at risk of colliding with terrain while attempting an approach to the Isle of Man. Previous inquiries highlighted the fact that the island's main navigation beacon, used during landings, was several miles from the airport.
Source: Flight International
