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Software safety issues were noticed by MOD before Chinook crash

A leaked draft memo written by a senior RAF officer reveals for the first time that there were safety concerns over the software used in the type of Chinook Mk2 helicopter that crashed on the Mull of Kintyre in June 1994.

Written a few days after the crash, the memo also reveals that the RAF was trying to "maintain a capability" by bringing the Chinook Mk2 aircraft fitted with the new software into service.

The Ministry of Defence has always denied that there was a serious shortage of Chinooks at the time of the crash on the Mull of Kintyre. It has also denied that any of its specialists had questioned the safety of the Chinook Mk2's new Full Authority Digital Engine Control software (Fadec), which controls fuel to the Chinook's two engines.

In the House of Lords in November 1999, for example, the MoD attacked a suggestion that its airworthiness assessors at the Aeroplane and Armaments Experimental Establishment (A&AEE) at Boscombe Down had claimed the Fadec was unsafe.

"Boscombe Down indicated a wish to assess the design of the Fadec software using a static code analysis - a methodology used by the nuclear industry... It did not say that Fadec was unsafe."

And the House of Commons Defence Committee was told by the MoD in 1998: "What we have is not a system that anybody has said is not safe... Not even Boscombe Down says it is not safe."

However, the RAF memo says that A&AEE had halted trials flying on the Chinook Mk2 "because of their concerns about the safety of the Fadec system".

The day after the ban on trials flying, which did not affect operational pilots, Chinook ZD576 crashed on the Mull of Kintyre, killing all 29 personnel on board. The pilots were blamed.

The House of Commons Public Accounts Committee is expected to meet this week to discuss, among other matters, whether the Chinook Mk2 was introduced into the service prematurely to meet high operational demand, despite the concern of its Boscombe Down.

The high-level RAF officer's memo, which has a reference date of 6 June 1994, may lend some weight to the idea that new Chinooks fitted with Fadec were brought into service too quickly. It says that the A&AEE's decision to halt trials flying on the Chinook Mk2 "contrasts sharply with the considerable efforts being made by the front line to bring the aircraft into service and maintain a capability".

The memo makes further attacks on Boscombe Down. The senior RAF officer said, "I find A&AEE's attitude quite incredible".

Draft memo reveals MoD’s “safety concerns” over Chinook software

A&AEE announced that, for the second time this year, because of their concerns about the safety of the FADEC system they had stopped trials flying on the Chinook Mk 2. I understand that, in practice, they are not flying the Chinook at all. Consequently, delivery of their aircraft to RAF Odiham on 21 July to enter minor servicing will be carried out by a No 7 Squadron crew who, because of test equipment fitted to the aircraft, will operate under a Service Deviation.

Since A&AEE will not have their Chinook Mk 2 back until September, I cannot claim that between now and then their refusal to fly the aircraft will further delay the trials programme. However, their ongoing stance towards the Mk 2 contrasts sharply with the considerable efforts being made by the front line to bring the aircraft into service and maintain a capability. It also does nothing to engender aircrew confidence in the aircraft. In sum, I find A&AEE's attitude quite incredible.

What is vital is that by the time the A&AEE aircraft is returned to them, they are fully ready to resume the flight trials programme. When all are agreed, including Boeing Helicopters, CA, the DHSA, my own Logistics staff and the front line squadrons, that the Chinook Mk2 is safe to operate at safe single engine weights, there can be no excuse for A&AEE not to fly at least to those parameters. Indeed, I believe that they can use jettisonable water ballast to load the aircraft to greater weights and thus it may well be possible to conduct safety trials above 18000 kg internal mass.

I would be grateful if you would establish whether or not A&AEE will be fully ready to resume Chinook Mk 2 trials flying in September and let me know the outcome.

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