On 6 November 1986 the first flight of the Bristish Airways Boeing Vertol (Chinook) 234 LR was delayed due to an oil leak from an engine gearbox that was soon rectified. Captain Vaid could take off from Sumburgh at 08:58 with 40 passengers for the Brent Field. It was a routine run to the Brent Charlie and Brent Delta platforms when they were told to make an additional stop at Brent Alpha. The Chinook departed Brent Charlie at 10:22 with 45 passengers on board for return to Sumburgh Airport, transiting at a height of 2,500 feet with the co-pilot Neville Nixon doing the flying. Approching Sumburgh the aircraft was given clearance to land and descended to 500ft. At about 11.30, 2.5 miles from the runway, the crew noticed a whining noise coming from the front gearbox. A catastrophic failure of forward transmission led to de-synchronisation of the twin rotors such that the forward and aft rotor blades collided. As a result the aft pylon, complete with the aft transmission and rotor system, detached from the fuselage. The aircraft struck the sea in a tail down attitude with considerable force, broke up and sank. An air rescue helicopter that had taken off from Sumburgh shortly before for a training flight, was able to rescue two survivors. The Captain Vaid was part of the two survivors. On 10 November the cockpit voice recorder, the cockpit section of the fuselage, the rotors and rotor heads, and the gearboxes and associated control systems had been recovered. 44 of the 45 bodies were recovered. The accident was caused by the failure of a modified bevel ring gear in the forward transmission which allowed the twin rotors to collide when synchronisation was lost. Captain Vaid was back in the cockpit six months after the tragedy but for the rest of his flying days, he took November 6 off.
The Chinook were withdrawn from operations in the North Sea after the accident and sold to Columbia Helicopters for heavy lift operations.
The Sumburgh tragedy is the 7th deadliest accident of the oil and gas industry. (Image: The Scotsman)