Chronology: The Chinook

1985 : Almost at the start of development of the Chinook's Full Authority Digital Engine Control ( Fadec ) computer system there...

1985: Almost at the start of development of the Chinook's Full Authority Digital Engine Control (Fadec) computer system there are unrealistic expectations. Delivery of the Fadec is promised within 23 months - it is delivered several years late. The Fadec controls the flow of fuel to the Chinook's two jet engines. The Fadec has a novel design - it has no mechanical backup, the main and backup "reversionary" lanes being controlled by software.

1989: After four years of development, Fadec has its first series of tests, fitted to an MoD Chinook Mark One. But the Chinook is nearly destroyed by a Fadec-related engine surge. The disaster is described in a confidential MoD report as "potentially catastrophic".

1989: Fadec is modified.

1993: An assessment on the modified Fadec software, by contractor EDS, is abandoned because of the large number of anomalies found - 485 after an analysis of less than 18% of the code. EDS says in a report to the Ministry of Defence that a potential flaw in the Fadec's main computer "may cause incorrect operation of the Fadec".

1993: Boscombe Down, the MoD's airworthiness assessor, questions the integrity of the Fadec design and integrity and refuses to endorse its use in service. The Superintendent of Engineering Systems Division has "major concerns" - in particular that it contains "illegal code" which means it may behave in a way not intended by the system designers. Boscombe Down's airworthiness experts say they will not approve the Fadec software unless it is rewritten. But MoD and RAF over-rule Boscombe Down and put the Chinook Mk2 into operational service without a software rewrite.

January to May 1994: The MoD's procurement executive raises "safety case issues" over the Fadec. Chinook pilots experience "flight critical" problems including unexpected engine surges, engine run-downs and cockpit warning lights. Boscombe Down suspends trial flights because of Fadec concerns.

1 June 1994: For the second time in five months, Boscombe Down suspends trial flights over Fadec concerns.

2 June 1994: Chinook ZD576 crashes on the Mull of Kintyre. There is no evidence of whether the helicopter was, or was not, under the control of the pilots in the last moments of flight.

3 June 1994: Boscombe Down says in a memo that the Fadec has been shown to be "unacceptable" and is "unsuitable for its intended purpose".

Late 1994: Major improvements to Fadec are made by its manufacturer Textron.

1995: Two air marshals over-rule the inconclusive report of an RAF Board of Inquiry into the crash and find that the pilots of ZD576 were grossly negligent.

1996: A Scottish Fatal Accident Inquiry says there is not enough evidence to blame the pilots.

1999: Computer Weekly publishes RAF Justice, a 140-page report on a cover-up of Fadec problems. Nearly 90 MPs sign an early-day motion for an investigation into Computer Weekly's findings.

December 2000: The Public Accounts Committee, after an investigation into the crash and the integrity of the helicopter, conclude that faulty software could have been a factor in the accident. The all-party committee accuses the MoD of "unwarrantable arrogance" in defending the "unsustainable finding" of pilot error in the 1994 Chinook helicopter crash. The MoD rejects the committee's findings. Senior ministers including Tony Blair reject calls for new inquiry.

February 2002: There are behind-the-scenes attempts to stop the House of Lords setting up an inquiry into the Chinook crash. But peers set up an independent inquiry and find that the cause of the accident can never be known - effectively exonerating the pilots. But the MoD rejects this conclusion of the committee, as it rejected the conclusion of the Public Accounts Committee, and reaffirms the finding of gross negligence against the pilots.

March 2002: Then defence secretary Geoff Hoon rejects calls for a new inquiry and launches an attack on Computer Weekly in the House of Commons over the magazine's Chinook campaign to clear the names of the pilots.

October 2002: The government makes it impossible for the families of two pilots blamed for the crash of Chinook helicopter ZD576 to seek a judicial review of the way ministers and officials have handled the matter.

December 2008: John Hutton, the new secretary of state for defence, meets legal and parliamentary representatives of the families of the pilots of ZD576. He is aware of striking new evidence - as yet unpublished - which the legal representatives of the families had given to the MoD months before.

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