DV:
It is true that the duct replacement program stems from the incident involving XV277, but the statement from BAES that certain ducts within the system were "life expired" goes back to June 2005, in is not a recent event. MOD did not accept that there was a problem until early 2008, almost 3 years later. Between June 2005 and 2nd Sept 2006, Nimrods flew with the cross-feed duct activated and with "life expired" ducting in the system. Since then Nimrods have continued to fly with suspect parts of the hot air system.
I wasn't aware that BAeS had inspected all of the HP air ducts and pronounced them lifex as early as Jun 05. Are you confusing the examination of the SCP system with the HP air system? The SCP system was certainly examined and declared dangerous the day after the XV227 incident, resulting in the immediate banning of its use. BAeS later (Jun 05?) confirmed the SCP was lifex.
The completion date of 31st May, 2009, was set by the Nimrod IPTL at the inquest, when he agreed that the system was not ALARP, but he was moving towards it. I am not surprised that IPT do not want to go beyond this point, because if it is not ALARP it is not safe.
IMHO Your last few words are not quite correct. ALARP, in the context of Nimrod risk analysis refers to the degree of risk of losing the aircraft due to a hazard caused by a single failure. Hickmans use of the term "ALARP" was misplaced and has led to a lot of confusion. Yes, in terms of the hazard presented by the old ducts, the risk of a single failure was not as low as practicable. They are lifex and they need to be replaced and, arguably, it is practicable to change them at the first opportunity, hence it can be said that the risk of a duct failure is not as low as practicable until the duct is changed. But, importantly, that is only in reference to the ducts, NOT the AIRCRAFT. The risk to the aircraft, created by a single duct failure (for whatever reason, including lifex) can be mitigated by the structure around the ducts and well practised crew procedures. Granted, there were no crew drills for a duct failure in the bomb bay, due to a lack of detection capability, and that part of the system is now out of operation in the air. Therefore, although the duct failure risk is not as low as reasonably practicable, the risk to the aircraft of a catastrophic or critical failure is bordering on negligible due to mitigation. This high degree of mitigation provides the control required for safe operation even in the event of pipe burst at the most critical time. Therefore, regardless of what Hickman said at the inquest, there is no legal need to drive towards ALARP then, now, or in the future. A HP air duct might be about to fail, according to Qinetiq, but the structure and the crew can handle it, safely.
With regards to the hazard risks in the engine bay and wing areas, I must ask if you have had time to read up on Hazard H66 and the QinetiQ report of Feb 2008. (We have talked about this on the other thread).
Yes, I read Hazard 66 some time ago, but the discussion was inactive and I thought it sensible to leave it so. Now, due to "Bob" its back in the headlines. I haven't been able to read Qinetiq's report, but I know the conclusion and I don't have any argument with it. It centres, quite rightly, on the age and condition of the pipework and they have upgraded the hazard accordingly. However, I'm led to believe that QQ did not comment on how the loss of the aircraft due to a pipe failure is mitigated by airframe structure, warnings and drills. Is there anything in H66 that you want to know more about? Please believe me, the loss of a hydraulic system (we have 5), an electric supply (we have 4), an air conditioning system (we have 2), and airframe de-icing system (we have 2; each capable of supplying everywhere) or a CDSU cooling pipe (I don't know why they mentioned that, but we have 4, anyway) an engine fuel fire (we have detection and extinguishants) all due to a single hot pipe failure is not a problem. Even our least experienced crews will deal with the problem very effectively. It has been practiced regularly since the day the aircraft first flew. Its a formal Basic Training Requirement to be able to deal with a hot pipe failure in an engine compartment. But it appears that Hickman doesn't want to account for our training in his narrow decision making process. On that basis, every max weight take off is dangerous because if an engine fails, the crew procedure is not accounted for as the only mitigation against a crash.
Meanwhile, the troops on the ground will not know where the next bullet is coming from. I wonder what the Army chiefs would think if they find out that we are not flying one their most valued air assets because we are "worried" about an insignificant problem.
Finally, detectors, fire suppression etc do not mitigate a hazard, they mitigate the accident. QinetiQ's words, not mine.
Agreed. And to summarize, we can easily avoid the accident and we can live with pipe failures ad infinitum.
Regards
Ed Sett