The Nimrod Review - Official Documents

6.100
Chapter 6 – Overflow or Pressure from Air-to-Air Refuelling
6.99.1 The conclusion of the Feasibility Study clearly states: “This report describes the incorporation into
a Nimrod MR Mk 2 of an AAR capability which will meet the requirements of a full CA Release.”
(emphasis added)
6.99.2 Section 5 of the Feasibility Study expressly considers whether the aircraft’s existing fuel venting system
required any modification and concludes, in this respect, that as regards tank No. 5, “During AAR a
fuel discharge from this valve may cause difficulties due to possible fuel ingress into the port engines.
To alleviate this possibility a differential pressure switch, identical to the Mod 700 installation, will
be fitted”. There would have been no need for BAE Systems to have considered such issues if its
responsibilities in relation to Mod 715 were as limited as it now sought to suggest.
6.99.3 The attachments to the Feasibility Study included schematic drawings of the refuel system as a whole.
In my view, therefore, reading Mod 715 and the Feasibility documents together, it is crystal clear that it was
intended that BAE Systems was responsible for ensuring the entire AAR capability, including the internal fuel
system, was Def-Stan 00-970 compliant.
XV230’s experience
6.101
6.102
On return from a sortie in August 2006, the Nimrod detachment personnel found a small amount of fuel in
XV230’s bomb bay, and traces of fuel having been discharged from the No. 1 tank blow-off valve during sorties
prior to the aircraft’s loss. The Nimrod detachment air and ground crew examined the symptoms and made a
logical deduction that the No. 1 tank blow-off had operated and that fuel from the blow-off had penetrated
the bomb bay along the hinge line. A de facto limit of 15,000lbs was subsequently operated by crews when
filling No. 1 tank during AAR and the symptoms disappeared. This limitation was not formally recorded in the
aircraft documentation but I have no doubt that it was put into operation by crews, and it was relayed to FS
Davies when he was briefed prior to his first AAR sortie in theatre and carried out by him. 50 Crew 3 was a highly
experienced, close-knit and capable crew.
In any event, there was no evidence available to the personnel at the time that blow-off might give rise to any
hazard. The No. 1 tank blow-off, unlike the No. 5 tank blow-off, had been left functional after the Nimrod was
made AAR capable. The blow-off was clearly capable of functioning, and indeed was meant to function, either
on the ground or in the air, to prevent over-pressurisation of the tank by fuel. It was, therefore, in my view a
reasonable assumption on the part of all concerned that there was no particular hazard in it functioning in either
environment.
6.103 The Air Member for Materiel, Air Marshal Sir Barry Thornton, notes, in his comments on the BOI, “it is unfortunate
that no aircraft incident reports were raised as a result of these events”, 51 while discussing the detachment’s
reaction to the occurrence of blow-off. In my view, however, in the circumstances pertaining at the time in theatre,
it is quite understandable that no incident report was raised. If blow-off had occurred on the ground during refuel,
no similar action would have been taken. The aircraft had been refuelled on the ground without incident. The
symptoms had also disappeared following the application of the 15,000lbs limitation. Thus, there was no reason
for anyone to think that were any significant underlying problems with the No. 1 tank’s refuel system.
6.104
In my view, the air and ground crew have absolutely nothing to reproach themselves for. The blow-off valve was
working normally as it was intended to operate. An incident report or call back to RAF Kinloss for instructions
would have been unlikely to have elicited any different solution to the problem. The BOI acknowledged that,
even after the accident, it took several months of painstaking investigation to uncover the cause and possible
effects of a blow-off. No one in theatre had any reason to suppose that it was anything other than the correct
operation of the aircraft systems. No one in theatre had any reason to suppose it might be a safety matter. No
one in theatre was, or could reasonably have been, aware of the serious ignition danger lurking in No. 7 Tank
Dry Bay.
50 BOI Report, page 2-34, and Witness Statement 22.
51 BOI Report, Comments of Air Member for Materiel, paragraph 14.
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