§ 34. Mr. Swayne
To ask the Secretary of State for Defence what revisions have been made to Chinook MKII FADEC software since June 1994. 
§ Mr. Spellar
As I explained in my letter of 21 August 1999 to the hon. Member, the only revisions to the Chinook FADEC software since 1994 were the nine software changes introduced as part of the block 1 upgrade later in that year. Two of these changes were potentially the most significant. The first of these was the introduction of a discrete memory to store the position of the engine condition lever (ECL) which was designed to prevent an engine shut down. The second was the fitting of a software filter to screen the speed values of the engine compressor and power turbines, which was designed to prevent an engine run-up.
However, we know that an engine shut down or run up was not a factor in the Mull of Kintyre accident. Examination of the wreckage showed that both engines were working normally right up until impact, and thus faulty FADEC could not have caused this accident. Indeed, the Air Accident Investigation Branch (AAIB) concluded that there was no evidence of any technical malfunction that could possibly have caused the crash.