Widerøe Flight 744

Widerøe Flight 744, also known as the Namsos Accident (Norwegian: Namsos-ulykken), was a controlled flight into terrain of a de Havilland Canada DHC-6-300 Twin Otter during approach to Namsos Airport, Høknesøra in Norway. The incident occurred on 27 October 1993 at 19:16:48 and killed six of the nineteen people on board, including the crew of two. No technical problems were found on the aircraft, and the accident report commented on a number of procedural errors committed by the two pilots during descent.

Accident

Widerøe Flight 744 was a scheduled flight from Trondheim Airport, Værnes to Namsos Airport, Høknesøra operated with a de Havilland Canada DHC-6-300 Twin Otter. The aircraft had registration LN-BNM and serial number 408, and was delivered to Widerøe in 1974. The aircraft had flown 40,453 hours and had met all service requirements. The pilot in command was 43 years old, had held a pilot's license since 1974 and had been employed in Widerøe since 1985. He had held a C certificate since 4 January 1993, and had been a pilot in command since 20 January. He had flown 4,835 hours and landed 13 times at Namsos Airport in the last 12 months. The first officer was 34 years old, had training from the United States, starting in 1981, which had been converted to a C certificate in 1988. He had 6,354 hours of flight, of which 1,356 was in a Twin Otter. He had been a pilot in command for 3,441 hours prior to working for Widerøe, where he had been employed since 1990. He had landed 27 times the last 12 months at Namsos Airport.

The first officer was using a medication against back pains which was not permitted while flying. However, these had been prescribed by a physician who had training in aviation medicine. No traces of the substance were found in the pilot's body after the accident.^[1] The aircraft had a maximum take-off weight of 5,675 kilograms (12,510 lb), while the aircraft took off with 5,460 kilograms (12,000 lb). Prior to departure, the ground handling agent, Scandinavian Airlines System had calculated the passenger load and mean aerodynamic chord of the passengers. When correcting this after observing the seating of the passengers, the pilot in command had made a calculation mistake, whereby he though passengers did not need to move around, while they actually would have to meet the limits of the distribution of weight.^[2]

The crew had started duty at Bodø Airport at 13:30 (UTC+1) and were to make a round trip to Trondheim Airport, with intermediate stops at Sandnessjøen Airport, Mosjøen Airport, Brønnøysund Airport, Brønnøy, Rørvik Airport as Flight 711. On the way down, the flight canceled stopping at Mosjøen due to the bad weather and the aircraft landed at Trondheim Airport at 17:52. The return flight was to operate as Flight 744 from Trondheim via Namsos to Rørvik, where the plane and crew were to overnight. At Trondheim, 17 passengers boarded along with 136 kilograms (300 lb) of cargo. Estimated flight time to Namsos was 35 minutes. The aircraft left Trondheim Airport at 18:37 after which it ascended to cruising height at 5,000 feet (1,500 m). At 18:53, the QNH was confirmed by Namsos to be 1017 hPa. This gave a height reading of 4,950 feet (1,510 m) and 4,900 feet (1,500 m), respectively, for the pilot in command and first officer. There was 25 knots (46 km/h; 29 mph) wind from 250°, with gusts up to 36 knots (67 km/h; 41 mph).^[3]

The pilot in command then decided on the descent plan, involving an initial descent to 4,000 feet (1,200 m), then down to 3,000 feet (910 m), before making a swing towards localizer 255. Then the aircraft should descend to 2,100 feet (640 m) and head towards Namsos beacon inbound. After that, minimum height was set to 2,100 feet (640 m). At 19:01, the aerodrome flight information service (AFIS) announced new weather data: the wind had changed to 260° at 25 knots (46 km/h; 29 mph), with gusts up to 40 knots (74 km/h; 46 mph). As the crew planned to use Runway 26, this would give wind directly against the craft, so the crew decided to add some height to the descent. At 19:05, the first officer stated that the descent checklist was completed, and the pilot in command started the approach checklist. At this time, both height indicators showed 5,000 feet (1,500 m). At 19:07, the aircraft was turned to 050°.^[4]

At 19:10, the aircraft reached the center line and the aircraft was confirmed by Namsos AFIS at 255°. By 19:14, the aircraft had descended to 2,100 feet (640 m) and at 19:15:13, it passed Namsos beacon. At 19:15:30, the first officer confirmed visual contact with the field. At 19:16:35, the pilot in command stated a height of 500 feet (150 m), confirmed by the first officer. Four second later, the pilot in command stated: "we should not descend any further". At 19:16:48, the aircraft hit a hill 6.15 kilometres (3.82 mi) from the airport, at Berg in Overhalla. A distress radiobeacon signal was received by Namsos and a search and rescue operation was started immediately. Both pilots, plus four passengers were killed, while the remaining thirteen passengers were injured.^[5] The aircraft first hit some trees, located 119 metres (390 ft) above mean sea level. The aircraft was written off after the accident.^[6] The instrument landing system at Namsos Airport was tested by the Norwegian Aviation Authority on 28 October and 4 November, without finding any faults with the system.^[7]

Cause

The weather in the area had wind up towards 30 knots (56 km/h; 35 mph), with clouds and heavy rain, and some reports of turbulence.^[8] The aircraft was not equipped with ground proximity warning system, nor was this required.^[9] There was no requirement for the aircraft to have a flight data recorder and cockpit voice recorder, but the airline had chosen to install the latter.^[10] Interviews with the surviving passengers show that none of them perceived that there was any problems with the flight until the sudden impact. One of the passengers of navigation profession could see parts of the cockpit from his seat, being able to confirm some of the navigational displays. Interviews with locals indicated that the aircraft followed a normal path.^[11]

The report from the Accident Investigation Board Norway pointed to several errors, both from the pilots, but also systematic failures from Widerøe and the Aviation Authority. In particular, the report commented on the lack of callouts during descent. The base turn procedure was also criticized, because the crew failed to time it correctly, ending up 14 nautical miles (26 km; 16 mi) from the airport. When the flying pilot canceled the instrument landing and changed to visual landing during darkness, he did not have sufficient visual references to the terrain. During this part of the approach, the aircraft's position was not controlled with any available navigational aids. This was in part due to both pilots focus on extra-cockpit activity after the non-flying pilot had identified the necessary sight to the airport. The crew were not aware of their distance from the terrain; the small margins from 500 feet (150 m) to 392 feet (119 m) were in part caused by pilots' unawareness. The cooperation between the crew did not follow the regulations of crew resource management and seemed to have stopped after visual identification of the airfield. The airline was criticized for not having standardized an operative concept that the crew fully respected and followed.

References

Notes

Bibliography

• Accident Investigation Board Norway (1996). "Rapport om luftfartsulykke ved Namsos den 27. oktober 1993 med DHC-6-300 Twin Otter, LN-BNM" (in Norwegian) (pdf). http://www.aibn.no/rapport-07-1996-pdf?pid=Native-ContentFile-File&attach=1.