The Nimrod Review - Official Documents

Chapter 3 – The Board of Inquiry Report
3.10.2 Service training courses were perceived by a number of witnesses no longer to impart the skill of hand
and depth of knowledge necessary to maintain an aircraft built around a design philosophy now some
40 years old. This, combined with a tautly-manned engineering establishment and a recent outflow
of skilled personnel, had led to an effective dilution of engineering skills, although the BOI found no
evidence that this contributed to the loss of XV230. I also consider this issue further in Chapter 13.
3.10.3 Other aircraft types in the MOD inventory use fuel seals similar to those fitted on the Nimrod. I consider
this issue further in Chapter 5.
BOI’s Conclusions in relation to the Nimrod Safety Case
3.11
3.12
3.13
The NSC was compiled between 2001 and 2005. In its Report, the BOI drew attention to a number of errors
contained within the NSC, including the following: 17
3.11.1 The NSC quoted the potential for fuel system leakage as ‘Improbable’, which is defined as ‘Remote
likelihood of occurrence to just 1 or 2 aircraft during the operational life of a particular fleet’. The BOI’s
analysis of fault data, however, indicated an average of 40 fuel leaks per annum for the Nimrod MR2
fleet between 2000 and 2005;
3.11.2 The NSC stated that the Cross-Feed duct was only pressurised during engine start, not taking into
account the lengthy periods it can be pressurised (at a working temperature of up to 420°C) when
feeding the SCP; and
3.11.3 The NSC noted as mitigation for Zone 614 hazards (which included the starboard No. 7 Tank Dry Bay)
the provision of an aircraft fire detection and suppression system, when neither existed within Zone
614.
The BOI concluded that the above inaccuracies led to an overly optimistic assessment of the hazards relating to
Zone 614, which in turn affected the assessment of the probability of the loss of an aircraft to an uncontrolled
fire/explosion – given as ‘Improbable’. Had the NSC’s inaccuracies been noted earlier, the BOI considered that a
more intense review of the hazards concomitant on airframe fuel leaks might have been instigated. Moreover,
the higher assessed risk which necessarily would have been attributed to such a hazard would have required
sanction at a higher level of management, or active mitigation, such as not using the SCP. 18
It was therefore the BOI’s conclusion that the overly optimistic hazard/risk categorisation of the potential threat
to the aircraft caused by the co-location of fuel and hot air system components within the No. 7 Tank Dry Bay
was a contributory factor in the loss of XV230. 19
3.14 Chapters 9 to 11 of this Report contain a detailed analysis the NSC, the facts surrounding it, the roles of those
responsible for it, and its part in the loss of XV230.
Validation of the BOI
3.15 The Review’s Terms of Reference are expressed to be “ in light of the findings of the BOI”. It has therefore been
important for me to satisfy myself as to the accuracy and completeness of the findings of the BOI. I summarise
below why I am satisfied that the reasoning and main conclusions of the BOI are correct.
17 BOI Report, paragraph 64 [2-45 to 2-46].
18 BOI Report, paragraph 32c(2) [2-23 – 2-24].
19 BOI Report, paragraph 32c(3) [2-24].
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