The Nimrod Review - Official Documents

Chapter 16 – Inquest
16.4.2 Second, the Coroner misunderstood the QinetiQ Combustion Report. 6 He said that at “11:13:45 the
combustion analysis demonstrates that at the time of observation by the camera the fuel couplings
would still be intact”. 7 This is incorrect. The QinetiQ Combustion Report Timeline has the fuel pipes in
the No. 7 Tank Dry Bay starboard starting to leak, and the No. 7 tank vent pipe starting to deteriorate,
before the camera observation at 11:13:45, depressurisation having taken place 1 minute 25 seconds
before at 11:12:20. 8 The QinetiQ Combustion Report concluded that “it appears likely that the elastomer
seals experienced minor early [heat] deterioration that caused fuel leaks” which then became “selflimiting
due to fuel cooling”. 9 The Coroner did not understand the logical and compelling sequence of
events explained in the QinetiQ Combustion Report: (1) only a small amount of fuel (no more than 300
mls) was required to start a pool fire in the tray at the bottom of the No. 7 Tank Dry Bay starboard; 10 (2)
this pool fire would have generated sufficient heat to cause damage to the nine elastomer seals in the
bay such that they began to leak fuel themselves; (3) the deterioration of these seals would, however,
have been gradual and self-limiting because of the cooling effect of the fuel in the pipes; (4) these
damaged and leaking seals would nonetheless have provided a sufficient secondary fuel source prior
to the pool fire burning out, or the loss of the lower panel; and (5) the ensuing conflagration would
become self-sustaining and led to all surfaces in the bay being subjected to temperatures well in excess
of the melting point of aluminium, including the No. 7 fuel tank itself. 11
16.4.3 Third, the Coroner appears to have misheard the evidence of the Harrier pilot. The Coroner suggested
“if the source of fuel was a fuel feed pipe then the fire would burn gradually forward towards the
source of the fuel leak” and “this would accord with the description first given by the Harrier pilot of a
fire further forward as set out within the Accident Investigation Report”. 12 In fact, the Harrier pilot said
clearly twice in evidence to the Inquest that the fire was “half-way down the wing root”, 13 i.e. near the
area of the No. 7 Tank Dry Bay starboard and nowhere near the leading edge of the wing. Moreover, it
is difficult to see how a fire could burn forward in the face of a 400 knot airstream.
16.4.4 Fourth, as explained elsewhere in this Report, the absence of surviving physical evidence means one
cannot, of course, rule out any one of a number of theoretical or possible fuel sources and fluid paths
in the aircraft. Any realistic assessment of the probabilities, however, points to a leak in the immediate
vicinity of the Cross-Feed/SCP duct from one of no less than eight fuel couplings within the No. 7 Tank
Dry Bay starboard itself, some located inches immediately above the SCP elbow, leading to a pool
fire 14 in the bottom corrugated panel, with the ensuing consequences outlined above. (See generally
Chapter 5).
16.4.5 Fifth, the Coroner was wrong to dismiss the possibility of blow-off from the No. 1 tank blow-off valve
during Air-to-Air Refuelling (AAR) as a source of fuel for the fire on XV230. He did so on the grounds
that “not one person has reported seeing a blow-off from number 1 tank during air-to-air refuelling...”
which “...would be spectacular with a huge amount of fuel being sent out from the side of the aircraft”. 15
The evidence showed that the phenomenon of blow-off has, in fact, been observed during refuelling
on the ground and will occur if similar conditions are imposed on a fuel tank during refuelling in the air,
although it will not necessarily be visible to the crew of the Nimrod or the tanker. There was, moreover,
evidence that blow-off did in fact occur on XV230 on several occasions during AAR sorties prior to
XV230’s final flight. (See generally Chapter 6).
6 Combustion Analysis of Nimrod MR2 XV230 Accident Issue 3, QinetiQ.
7 Coroner’s narrative verdict, 23 May 2008, page 23, first paragraph.
8 Combustion Analysis of Nimrod MR2 XV230 Accident Issue 3, QinetiQ, page 45.
9 Combustion Analysis of Nimrod MR2 XV230 Accident Issue 3, QinetiQ, paragraph 11.2(c).
10 About a Coke can.
11 Combustion Analysis of Nimrod MR2 XV230 Accident Issue 3, QinetiQ, page 16.
12 Coroner’s narrative verdict, 23 May 2008, page 27, third paragraph.
13 Inquest transcript, 12 May 2008, pages 157 and 163, fourth and third paragraphs respectively.
14 And probably a stoichometric mix.
15 Coroner’s narrative verdict, 23 May 2008, page 16, second paragraph.
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