The Nimrod Review - Official Documents

The Nimrod Review
7.67
Conclusion
148
the analysis were not aircraft designers. Third, the relevant group of detectors were described in the relevant
documentation as the “centre section” overheat detection system and thus the reader might be forgiven for
not appreciating that the sensors did not, in fact, cover the centre section of the centre section. Fourth, the
hot air leak warning system and Cross-Feed ducting were part of the original MR1 design and were the same
as had been installed when the aircraft initially entered service and, up to that point, nobody had queried its
effectiveness or coverage (with the exception of the subsequent UI report). In these circumstances the errors
in the initial analysis of the coverage of the aircraft’s existing overheat detection systems were understandable.
However, the level of analysis carried out at this stage was unsatisfactory and below what might be expected
from an Engineering Authority. More careful analysis was called for, which might have revealed the ‘gap’ in the
coverage of the system.
A further question arises as to whether the Nimrod IPT ought to have revisited that decision following publication
of BAE Systems’ June 2005 report into the life of the ducts and the publication of the UI report in July 2005. The
BAE Systems paper investigating the bleed-air detection system noted that the flow-limiting venturi would not
detect relatively substantial leaks from the SCP system. Furthermore, the UI flagged up the system’s incomplete
coverage and recommended a leak detection system for both the SCP and the Cross-Feed duct. There is no
evidence that either of these documents gave rise to a re-consideration of the earlier decision to switch the SCP
back on, or that wider implications were considered, notwithstanding that, even with the SCP turned off, the
Cross-Feed duct would have been active during flight, presenting the risk of an undetected leak in any event. The
IPT appears not to have considered the clear implications of the BAES and UI documents and to have remained
fixated on their earlier, faulty analysis. If these later documents had been given the focus they deserved then
a reassessment of the risks of duct failure would necessarily have followed. This might have led to a decision
to restrict the use of the SCP and Cross-Feed system, or placed greater emphasis on the need to consider
replacement of the Cross-Feed ducts. In many ways this seems another example of the IPT examining faults in
isolation and failing to consider their wider implications or impact (see Chapter 8). It is also symptomatic of the
general malaise of reports being received but not being reviewed with sufficient rigour.
The analysis carried out by the Nimrod IPT of the coverage of the
7.68 overheat detection system was, in my view, far
from satisfactory. It remains an unfortunate fact that the result of the decision to turn the SCP back on meant
that, by a tragic coincidence, the ignition source which led to the loss of XV230 was available.