Once again, many thanks for your very informative comments
No problem. I don't think I'm breaking any rules in discussing and amplifying info already in the public domain. Although some of it should not have been released.
Does this new hazard analysis negate the complete BAE systems hazard analysis of 2004, and which IPT approved in Feb 05? Or does it only address the problems in the dry bay area?
Good question, and I'm sure its one that the QC will be posing in due course. Its the most accurate analysis we have at the moment and if it differs from any previous analyzes on points of fact, it has to override them in those particular matters. It covered all aspects of the Nimrod fuel system.
They also suggest the problem could have been caused by a small hole in a hot air pipe, which in turn damaged a fuel line. (very much like XV227).
The SCP and the other pipes in that zone are surrounded by heat sensors, specifically designed and located to detect hot air leaks. So, the BOI rightly surmised that any hot air leak would have been below the detection threshold (235C), because the engineer did not mention an overheat warning. Such a small leak would have to have played directly onto a fuel coupling (it would never have burned through a metal pipe) such that the coupling failed and the fuel then played onto the pipe. Its a series of events that are less likely than a simple coupling leak (for any reason) or a blow-off. However, its a scenario that can't be discounted. I should add that a number of the "similar" pipes, as referred to in the 227 incident, on other aircraft have since been checked for deterioration and none has been found showing any potential to fail.
It is also worth reading Air Member for Materiel's comments in the BoI report.
Quote:
Prohibiting use of the SCP removes this ignition source but we must not allow ourselves to be convinced that consideration of other potential sources of ignition can therefore be excluded.
Whilst we still have problems with fuel in the bomb bay post AAR, I can not see how we can consider the aircraft safe.
Well, the BOI used the term, "probable cause". That leaves the door open for anyone to add the quoted comment. However, I place my personal trust, and I recommend it to other aircrew, in the QQ combustion analysis sponsored by the BOI. It provides us with the confidence that fuel leaks in the bomb bay are not dangerous in the absence of very hot surfaces. I'm not suggesting that the crews should ignore fuel leaks, but we need to be confident in that particular analysis, respect our ground crew's efforts to prevent the leaks and rely on our training to deal with them if they occur. We have well-practised procedures to stop every single fuel pipe leak on a Nimrod.
Ed