The Ministry of Defence denied yesterday that the action had any link to the crash of a Chinook on the Mull of Kintyre five years ago, which killed 25 senior intelligence officers. But the announcement will inevitably raise fresh questions about that crash, which was blamed on pilot error, to the anger of the crew's relatives.
The RAF has ceased to fly its 27 Chinooks, though they are technically not grounded. The difference is that no specific action is required before they can take to the air again. But the US Army grounded its 466 CH-47 helicopters and Boeing, the manufacturer, advised the many other air forces and armies around the world that operate the machine to halt flights.
The cracked engine transmission gear was found recently in a second stage plenary gear assembly during a routine check by the RAF, Boeing said. A subsequent investigation found that the cracked gear was one of 63 made in a single production lot. Eleven of the remaining gears were found at Boeing, one of them cracked, and five others were found in an Egyptian aircraft.
"We take flight safety very seriously," an MoD spokesman said yesterday. But there was "nothing to suggest a serious problem", he added. "No accidents have been cause by this problem." He specifically ruled out any link between the latest fault in the Chinooks and the June 1994 crash. That was "a completely separate issue".
The RAF Chinook crash killed 25 senior intelligence officials from the Army, the Royal Ulster Constabulary and MI5 on their way from RAF Aldergrove to Fort George near Inverness for a discussion of security policy in Northern Ireland. They hit the ground in very poor visibility.
An RAF board of inquiry said that the crash was caused by pilot error, accusing the crew of negligence. But a fatal accident inquiry found that in the absence of a flight recorder, the cause would remain a mystery. And subsequent investigations revealed a series of questions about the Chinook's safety, centring on the aircraft's Full Authority Digital Engine Control, which controlled fuel supply to the engines.
Shortly before the crash, the crew reported a change of engine noise and unequal distribution of power. There had also been problems with the automatic pilot; an instrument panel broke loose; rumbling noises were heard in the engine; and warning lights had come on.
The Chinook has had a mixed history. It was first built in 1961, and its ability to carry up to 50 people made it a favourite of the North Sea oil industry. It gathered a reputation in Vietnam as a workhorse, but has been involved in a number of accidents.
There were at least 10 crashes of military Chinooks in the US between 1985 and 1994.Reuse content