New evidence shows that the air chief marshal who blamed the pilots for the Chinook crash on the Mull of Kintyre in 1994 was not given potentially vital information related to the helicopter's safety-critical software.
This evidence was due to be presented by senior Peers and MPs to defence secretary Geoffrey Hoon yesterday (Wednesday).
In a parliamentary answer, the Ministry of Defence (MoD) confirmed that Sir William Wratten, the most senior officer on the RAF Board of Inquiry into the crash on the Mull of Kintyre, was unaware of an earlier incident, in 1989, in which an RAF Chinook suffered serious damage as a result of a software fault.
Wratten was also unaware that, as a result of the 1989 incident, the MoD had made serious allegations against Textron Lycoming, the US supplier of the Chinook's computerised Full Authority Digital Engine Control (Fadec) system.
In court documents, the MoD had claimed that the Fadec was "unsafe", that the specification contained patent errors and ambiguities that remained after "numerous revisions", and the design strategy "relied on unproven software as the only significant safeguard against catastrophe".
Not knowing of these allegations, Wratten had no reason to believe that the Fadec system was capable of causing a crash. The MoD has claimed repeatedly that the system was not capable of causing a catastrophic accident.
Both Wratten and air vice marshal Sir John Day, as reviewing officers, over-ruled an inconclusive report by a three-man inquiry team which found that a series of minor or a possible major technical malfunction could have distracted the crew.