de Havilland Canada DHC-6 Twin Otter 300 – LN-BNK

Incident Overview

Date: Thursday 11 March 1982

Aircraft Type: de Havilland Canada DHC-6 Twin Otter 300

Owner/operator: Wider?es Flyveselskap

Registration Number: LN-BNK

Location: 6 km SE off Gamvik – ÿ Norway

Phase of Flight: En route

Status: Destroyed, written off

Casualties: Fatalities: 15 / Occupants: 15

Component Affected: Aircraft Vertical StabilizerAircraft Vertical Stabilizer

Investigating Agency: HSLHSL

Category: Accident

On March 1, 1993, a DHC-6 Twin Otter, en route from Kirkenes Airport to Alta Airport, experienced a sudden loss of altitude and subsequently disappeared over the Gamvik area of Norway. The aircraft was scheduled for a domestic service flight with an intermediate stop at Vads?, Berlevg, Mehamn, and Honningsvg airports. The flight originated at 13:19 hours from Berlevg, Norway, and the pilot reported an altitude of 2,000 feet over the Tanafjord, with an estimated arrival time of 13:33. Upon reaching Mehamn Aerodrome, the pilot radioed Flight 933 at 13:35, but received no response. The aircraft failed to arrive at its destination, and was subsequently located two days later at a depth of 45 meters off Gamvik, Norway, in the water. The investigation determined the vertical stabilizer malfunction was the primary cause of the accident, stemming from strong turbulent wind conditions. The incident occurred during a NATO military exercise, specifically within a designated no-fly zone for allied military aircraft, and a radar observation of an unidentified aircraft on a collision course with the Twin Otter occurred in 1987.On March 1, 1993, a DHC-6 Twin Otter, en route from Kirkenes Airport to Alta Airport, experienced a sudden loss of altitude and subsequently disappeared over the Gamvik area of Norway. The aircraft was scheduled for a domestic service flight with an intermediate stop at Vads?, Berlevg, Mehamn, and Honningsvg airports. The flight originated at 13:19 hours from Berlevg, Norway, and the pilot reported an altitude of 2,000 feet over the Tanafjord, with an estimated arrival time of 13:33. Upon reaching Mehamn Aerodrome, the pilot radioed Flight 933 at 13:35, but received no response. The aircraft failed to arrive at its destination, and was subsequently located two days later at a depth of 45 meters off Gamvik, Norway, in the water. The investigation determined the vertical stabilizer malfunction was the primary cause of the accident, stemming from strong turbulent wind conditions. The incident occurred during a NATO military exercise, specifically within a designated no-fly zone for allied military aircraft, and a radar observation of an unidentified aircraft on a collision course with the Twin Otter occurred in 1987.

Description

Wider?es Flyveselskap flight 933, a DHC-6 Twin Otter, crashed into the sea off Gamvik, Norway, killing all 15 occupants. Wider?e Flight WF933 was a scheduled domestic service from Kirkenes Airport, Norway to Alta Airport, with intermediate stops at Vads? Airport, Berlevg Airport, Mehamn Airport and Honningsvg Airport. The Twin Otter left Berlevg at 13:19 hours on the third leg of the flight. The first officer reported to Mehamn Aerodrome Flight Information Service (AFIS) at 13:22 that the aircraft was at 2,000 feet altitude over the Tanafjord and had an estimated time of arrival of 13:33. Mehamn AFIS radioed Flight 933 at 13:35, but received no answer. The aircraft failed to arrive at was declared missing. The wreckage was located two days after the accident at a depth of 45 meters in the water off Gamvik, Norway. The investigation into the cause of the accident concluded that the vertical stabilizer failed in flight in strong turbulent wind conditions. The accident occurred during a NATO military exercise, within a self-declared no-fly zone for allied military aircraft. A report in 1987 that radar had observed an unidentified aircraft which was on a collision course with the Twin Otter caused a second investigation to be started. It was concluded that the existence of other aircraft in the area could be ruled out; and that no other airborne objects could have caused the accident. The debate about the accident resurfaced in 1997 when several sources claimed there was new or overlooked evidence of the involvement of NATO aircraft. The Accident Investigation Board Norway (AIBN) decided in 1997 to investigate the new claims and concluded that there was no evidence to support these claims. The accident was ordered investigated again in November 2002 after a retired Norwegian air traffic controller said one of the Harrier pilots, involved in a mission about the time of the accident, had requested an immediate landing because of technical problems. The report was published on 20 September 2005. It fully supported the findings of all three previous reports and found no evidence for an impact with a Harrier or any other aircraft. ORIGINAL PROBABLE CAUSE: Overload due to a combination of clear air turbulence, local whirlwind, mountain wave and the pilots spontaneous improper actions.

Source of Information

https://web.archive.org/web/20160119132351/https://www.stortinget.no/Global/pdf/Dokumentserien/2004-2005/dok24-200405.pdfhttps://web.archive.org/web/20160119132351/https://www.stortinget.no/Global/pdf/Dokumentserien/2004-2005/dok24-200405.pdf

Primary Cause

Vertical stabilizer failure due to strong turbulent wind conditions during a NATO military exercise.Vertical stabilizer failure due to strong turbulent wind conditions during a NATO military exercise.

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