Widerøe Flight 710, also known as the Torghatten Accident (), was a controlled flight into terrain into the mountain of Torghatten in Brønnøy Municipality, Norway. The Widerøe-operated de Havilland Canada Dash 7 crashed on 6 May 1988 at 20:29:30 during approach to Brønnøysund Airport. All thirty-six people on board LN-WFN were killed; the crash remains the deadliest accident involving the Dash 7 and the deadliest in Northern Norway. The direct cause of the accident was that the aircraft had descended from at instead of from the airport.
An investigation found several shortcomings in the airline's operating procedures, in particular lack of proper cockpit communication and mutual control of the descent and approach plans. This was in part caused by the airline electing to not follow the sterile cockpit rule and that a passenger was sitting in a cockpit jump seat during the flight. The investigating commission also found lack of proper pilot training in the airline. Flight 710 was the second of four Widerøe accidents between 1982 and 1993, all of which revealed shortcomings in the airline's operations and internal control.
Aircraft The accident aircraft was a four-engine de Havilland Canada DHC-7 Dash 7 Series 102, with serial number 28, built in 1980. It was bought used by Widerøe in 1985 and registered as LN-WFN on 8 November 1985. Its certificate of airworthiness was last renewed on 4 November 1987 and was valid until 30 November 1988. The aircraft had operated 16,934 hours and 32,347 cycles prior to its last flight. The last A-check took place on 15 April 1988, after which the aircraft had flown 147 hours and 30 cycles.AIBN: 11
Flight deck crew The captain was 58-year-old Bjørn Hanssen, a resident of Bodø Municipality. He held a D-certificate issued on 8 April 1981, which was last renewed on 11 December 1987. He took his initial license in 1949 and had worked as a pilot for Widerøe since 1 April 1960. At the time of his last renewal, he had flown 19,886 hours, of which 2,849 hours were with the Dash 7. He had completed periodical flight training with the Dash 7 on 8 March 1988. He had just returned to Norway following a six-week vacation in Spain.AIBN: 9
The first officer was 31-year-old Johannes Andal, a resident of Bømlo Municipality. He held a C-certificate, which limited him to being first officer on the Dash 7. The certificate was issued on 5 January 1987, and had been valid for the Dash 7 since 23 February 1988. He had started his flight training in 1977 and had completed it in the United States in 1979. He was hired as a pilot for Widerøe on 6 February 1986, originally serving on the de Havilland Canada DHC-6 Twin Otter. He was checked out as first officer on the Dash 7 in February 1988. He had a total flight time of 6,458 hours, of which 85 were on the Dash 7.AIBN: 10 The flight attendant was 28 years old and had worked for Widerøe since 1983.
Flight
The aircraft had been used during the morning of 6 May on a multi-leg flight from Bodø to Trondheim and back. It had then flown back to Trondheim where it changed crew. They had arrived at Trondheim with a flight at 18:50 on 6 May and left the hotel in Trondheim at 16:15 on 6 May. Flight 710 was scheduled to fly from Trondheim via Namsos; Brønnøysund; and Sandnessjøen. It departed Værnes after a 90-minute delay at 19:23 due to technical problems with another aircraft. Flight 710 had a crew of three: a captain, a first officer and a flight attendant. The aircraft was packed and therefore a jump seat in the cockpit had to be used by a passenger, bringing the number of people on board to 52.AIBN: 4
The aircraft made a stop-over at Namsos where sixteen passengers disembarked, reducing the number of passengers on board to thirty-three. The captain was the pilot flying for the segment, and the passenger occupying the jump seat remained in the cockpit. The aircraft departed Namsos at 20:07 and received permission from Trondheim ATCC at 20:13 to ascend to flight level 90 (FL 90). During the flight, the passenger in the jump seat held a conversation with the captain and asked several questions regarding the operations. The first officer did not participate in this discussion, and it was he who conducted radio contact with air traffic control and the airline's operations center.AIBN: 5
The first officer contacted the airline at 20:16 and informed that they expected to arrive at 20:32. At 20:20:29, the aircraft asked permission from Trondheim ATCC to switch to Brønnøysund Aerodrome Flight Information Service (AFIS), which was granted. The aircraft announced at 20:20:42 that they would start the descent and would switch to Brønnøysund AFIS. Contact was made at 20:22:34, at which time the aircraft announced it was from the airport and at FL 80. AFIS informed that there were no known aircraft in the area and that runway 22 was in use; wind was from southeast, visibility, a light shower and . At 20:23:22 the first officer held a 62-second conversation with the airline ordering a taxi for one of the passengers so he could reach his connecting ferry.AIBN: 6
The captain asked for the descent checklist at 20:24:24. The fasten seat belt sign was switched on and the flight attendant started the process of preparing the cabin for landing. At 20:24:46 the captain, as part of the checklist, informed the first officer that they would go down to at Torghatten and then down to . This was followed first by a partially inaudible conversation between the captain and the first officers, which included if they were to fill fuel, and then an inaudible conversation between the captain and the jump seat passenger. The direction of the VHF omnidirectional radio range (VOR) and distance measuring equipment (DME) at Brønnøysund was checked at 20:26:37.
The approach checklist was started at 20:27:01, at which time the aircraft's altitude reached . The first point on the checklist was not readable, but the last three were. At 20:27:32 the captain asked for flaps and landing gear, which were immediately deployed by the first officer and resulted in the aircraft gaining of altitude. The landing gears were confirmed locked at 20:28:00. Four seconds later the passenger asked the captain if there were reserve systems which could be used if the landing gear did not deploy properly. At this point the aircraft started the descent from .AIBN: 7
AFIS asked for the aircraft's position at 20:28:10, and the first officer responded at 20:28:13 that it was away. He asked AFIS for a wind check, and AFIS responded that it was from 220 degrees and . The first officer confirmed the information at 20:28:24. The aircraft reached altitude and remained at that height for the rest of the flight. A short conversation was initiated by the passenger at 20:28:55. Three seconds later, the captain asked for "25 degrees flaps and props fully fine". This was confirmed by the first officer two seconds later. The pre-landing checklist was completed between 20:29:04 and :19.
The autopilot had been used since 25 seconds after take-off from Namsos and was used for the remainder of the flight. From 20:29:21 all four engines showed increasing torque and immediately before the crash the aircraft had shifted its angle from −2.5 degrees to 5 degrees.AIBN: 8 At 20:29:29 the ground proximity warning system showed 'minimum'. The aircraft crashed into the western side of Torghatten at 20:29:30 at elevation.
The aircraft flew into the mountain at an angle of 15 to 20 degrees, with the starboard side towards the mountain. The aircraft was ascending at a seven-degree angle, plus/minus one degree. The tip of the starboard wing was the first to hit the mountain, followed by engine number four (the right-most). The engine was immediately torn off and the aircraft started to rotate. The aircraft started being torn in the back rib of the starboard wing. Then the nose and port wing from engine number two (the inner) hit a depression in the mountain-face, causing engine number one to loosen from its nacelle and the port wing to break between the engines. At the same time the aircraft's body was broken in two. The aircraft's forward movement stopped, the wreck pieces rotated with the vertical stabilizer away from the mountain-side, the port wing caught on fire and exploded and the rest of the aircraft fell down the slope. On the way down, the starboard wing caught on fire.AIBN: 19
Salvage The aircraft crashed into Torghatten, which is located south-west of Brønnøysund Airport. The mountain is tall and is a distinct height in an area which is otherwise rather flat. The aircraft hit the western side of the mountain at a point where the terrain is forty degrees steep. The center line of the flight path is from Torghatten. The wreck was spread over an area below the point of impact.AIBN: 18
AFIS made several attempts to call up the aircraft. It received a call from a resident close to Torghatten which said they had heard aircraft noise followed by a crash. Brønnøysund Fire Department and an ambulance helicopter with a doctor was dispatched to Torghatten. The rescue work was made difficult by low clouds, small fires and explosions. The terrain was difficult and the lack of daylight made assisting the situation difficult. A helicopter with medical personnel and the airport direct arrived at 21:25, while a meeting place for the next of kin was established at the airport. At 23:30 the police stated that there was no hope of finding survivors and the scene changed from a search to an investigation scene. Due to the fog it was not possible to verify that all people had been killed until the next day. Seventy-five soldiers from the Home Guard participated in the salvage.
Investigation The Accident Investigation Board Norway was informed about the accident at 21:10.AIBN: 1 Four members of the investigation commission were appointed, consisting of leader Lieutenant General Wilhelm Mohr, Pilot Hallvard Vikholt, Lieutenant Colonel Asbjørn Stein and Chief-of-Police Arnstein Øverkil. Because of poor weather conditions, the commission was not assembled in Brønnøy until 15:00 on 7 May.AIBN: 2 The same day the National Criminal Investigation Service arrived to assist AIBN. Six people appointed by the Canadian Aviation Safety Board, including representatives from de Havilland Canada and Pratt & Whitney Canada, were sent to aid the investigation. Four representatives from Widerøe were available for consultation with the commission. The investigation commission was later supplemented by psychologist Grethe Myhre and Øverkil replaced by Arne Huuse.
The VOR/DME system was tested by the Civil Aviation Administration of Norway on 7 May and found to be working correctly.AIBN: 26 AIBN established a base of operations at the hangar at Brønnøysund Airport and used a helicopter to freight the pieces of the wreck there and bodies to Trondheim University Hospital for identification. Technical investigations started on 9 May.AIBN: 3 The aircraft was equipped with a flight data recorder and a cockpit voice recorder. Both were found intact and were decoded at the Air Accidents Investigation Branch in the United Kingdom.AIBN: 17–18 Improper use of the microphone made it difficult to hear the captain's voice, but it was possible to reconstruct the conversations and line of events. A memorial service was held on 10 May and was attended by Prime Minister Gro Harlem Brundtland. The last Home Guard personnel concluded their work on 11 May and the police concluded their investigations at Torghatten on 13 May.