The Ministry of Defence has spent more than £500 million on eight Chinook helicopters that have never been flown as a result of “one of the most incompetent procurements of all time”, an audit has concluded.

The helicopters have been sitting in a special air-conditioned shelter for the past seven years because of a “gold-standard cockup” that meant the machines’ software could not be accessed.

While commanders in Afghanistan have been crying out for extra helicopters, the Chinooks – which were supposed to fly missions for Special Forces – have been lying idle in hangars in the Wiltshire countryside.

A report by the National Audit Office (NAO) says that by the time the helicopters enter service the cost of making them airworthy as well as taking interim measures to fill the capability gap will have risen to more than £500 million. The original purchase price of the eight Chinooks was £259 million.

The procurement nightmare involving the unflyable eight Chinook Mk3s, bought from Boeing in 2001, has already been the subject of one NAO report, published in 2004. Then it was described by Edward Leigh, chairman of the Commons Public Accounts Committee, as “one of the most incompetent procurements of all time”.

The major difficulty with the purchase arose when the MoD discovered that it had neglected to include in the contract a clause that would provide access to the source codes for the highly complex software. Without them, RAF specialists were unable to check whether the adapted helicopters passed Britain’s strict airworthiness criteria.

Boeing was reluctant to hand over the codes since no request had been made for them in drawing up the contract. So the RAF said that the Chinooks could not be flown except in the most clement weather. The sky had to be cloudless and the pilots would have to operate from at least 500ft so that they could navigate by landmarks.

For a helicopter that was supposed to be used by the SAS and the Special Boat Service (SBS) in covert missions in all-weather conditions, night and day and at hedge-hopping altitudes, the decision by the RAF in effect grounded all eight Chinooks.

They were put into climate-controlled, dehumidified aircraft shelters at Boscombe Down, Wiltshire. Since 2001 they have been inspected once a week and moved out every two years for more detailed checks, at a total cost of £560,000, according to the NAO.

“Today, nearly seven years since they were delivered, the Chinook Mk3s are still languishing in climate-controlled hangers, despite the fact that they are desperately needed on operations in Afghanistan,” Mr Leigh said.

“The MoD’s programme to make airworthy the eight Chinook Mk3 helicopters . . . has been a gold-standard cockup,” he said.

After the shock of discovering that it was too risky to fly the Chinooks in cloud, the MoD negotiated with Boeing in 2004 to upgrade the eight helicopters, including modifications to the cockpit, costing £215 million. It took 30 months for the programme to be agreed, however, and in 2006 the MoD announced that thousands more troops would be sent to Afghanistan and more helicopters were desperately needed, especially Chinooks. The MoD decided to cancel the Chinook Mk3 upgrade project and convert the special-forces helicopters into ordinary troop-carrying utility helicopters. But the NAO said that the MoD failed properly to analyse the costs and risks of this decision. The costs rose by 70 per cent from £53 million to £90 million.

Extra funds were also spent to provide an improved night-vision capability on the older Chinook Mk2s for the SAS to use. But the NAO discovered that the “night enhancement package” obscured the pilot’s forward view. Mr Leigh said it potentially endangered the safety of the helicopter. The first of the converted Chinook Mark 3s will now come into service next year.

Baroness Taylor of Bolton, Minister for Defence Equipment and Support, said that the decision to revert the helicopters to utility aircraft would allow the delivery of more Chinooks to Afghanistan “in the shortest time-frame”.

The NAO said that as a result of the “protracted” decision-making process at the MoD, “the shortage of helicopters to support operations has been exacerbated”.

Nick Harvey, the Liberal Democrats’ defence spokesman, said: “This is a dismal tale of dithering, bad planning and a gross waste of public funds . . . yet penny-pinching on other MoD equipment has cost lives.”

Short supply

— Each Chinook can carry up to 55 troops, or ten tonnes of cargo or two Land Rovers

— The helicopter has seen service in the Falklands, Northern Ireland, Kuwait, Bosnia, Sierra Leone, Iraq and Afghanistan

— Chinook Mark 2 and Mark 2a helicopters have out-of-service dates of 2015 and 2025 respectively

— The UK’s 40 Chinooks are flown by three RAF squadrons, No 7, No 18 and No 27

— There is a global shortage of Chinooks. The US Army is 100 short of its requirement of 489 helicopters

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