Tony Blackburn misses out one vital investigation; the inquest. The only investigation that called for evidence to be given on oath, and the cross-examination of witnesses. The inquest concluded that "on the balance of probability" a blow off did not happen. None was witnessed by the Tri Star crew, either during refuelling or on climb out.
The fuel leak on XV235 came from a fuel coupling in the main refuelling line just forward of the bomb bay heating mixing chamber. It was observed as a spray (from port to stbd) by the crew. It certainly was not a blow-off from No.1 tank.
The Harrier pilot was the only close eye witness to the Nimrod fires and drawings produced by him, immediately after the accident and at the inquest, clearly indicate the fire source as being close to the stbd wing leading edge i.e., in line with the mixing chamber. This vital evidence (ignored by the BOI and HC) prompted the coroner to conclude that the source of the fuel "would accord with the description first given by the Harrier pilot of a fire further forward [than No.7 tank dray bay].
Contrary to what the BOI and HC thought, documentary evidence indicates that the temperature of the hot air to the input side of the mixing chamber was well above that required for auto-ignition. The evidence also suggested that due to “air blanking” caused by the Tristar refuelling tanker aircraft the system would run hotter than normal due to the reduced air flow through the primary heat exchangers located in the leading edges of both wings. The same air blanking effect is thought to have caused the Supplementary Cooling Pack to shut down during the AAR process, an event which is mention by the flight crew of XV230. It is unlikely that the shutdown was caused by the fire, as this anomaly had been observed by other flight crews prior to the accident. It is perhaps significant that the hot air feeds to the mixing chamber were immediately isolated on all aircraft in the fleet after the accident and the system never activated again. This act probably saved XV235, and not the isolation of the cross-feed hot air system associated with the SCP.
I agree that there is some commonalty between XV230 and XV235, but not for reason that Tony Blackburn gives. In my opinion the fuel leak came from a refuel coupling in the bomb, just forward of mixing chamber. However I do agree (110%) that the HC report is a rubber stamp of the BOI report, most likely because two BOI members were advisers to HC, and both were visibly upset when the Coroner rejected their blow-off theory.
Nimrod was retired because fuel couplings could not be correctly aligned (1 degree in all axis) and replacements for the life expired hot air pipes were difficult manufacture (all aircraft were different). The aircarft could no loger carry stores safely, because the bomb bay could not be heated and the release units had become defective because of several years of inactivity. £18 million was spent on a pipe/coupling modification programme that failed to save the aircraft.
DV
Last edited by Distant Voice; 23rd Oct 2012 at 12:54.