The Nimrod Review - Official Documents

The Nimrod Review
6.96
128
I have concluded that Mod 715 was in breach of Def-Stan 970 in two major respects:
(1) Breach of Def-Stan 00-970 requirements regarding blow-off valves
6.96.1 First, the Nimrod Mod 715 design failed to meet the safety standards regarding the design and location
of fuel blow-off valves. Def-Stan 00-970 required that “no vent or discharge provision shall end at any
point where the discharge of fuel from the vent outlet in flight or on the ground would constitute
a fire hazard.”. 45 The location of the No. 1 Tank blow-off valve, some half-way down and flush with
the aircraft fuselage, and directly forward of the starboard No. 7 Tank Dry Bay, fails to meet these
requirements. Should blow-off operate during AAR, fuel can be discharged into the 400 knots airflow
at a rate of some 120 litres in ten seconds. (This rate would be sufficient to fill an average domestic car
fuel tank in under three and a half seconds). As explained above, fuel discharged in this way could track
back and flow between panels and into voids within the aircraft, including the starboard No. 7 Tank Dry
Bay and possibly the SCP pre-cooler inlet. 46
(2) Breach of Def-Stan 00-970 requirements regarding location of fuel pipes
6.96.2 Second, the Nimrod Mod 715 design failed to meet the safety standards regarding fuel pipes in the
AAR system. Def-Stan 00-970 47 required that: “Fuel pipes should not run through crew/passenger
compartments nor close to high pressure hot air ducts and electrically operated equipment in bays.
Where it is not possible to comply with this, the pipes shall be without couplings, and preferably of
steel. The pipe run through such zones shall be completely jacketed, and overboard drains shall be
provided.” Within the starboard No. 7 Tank Dry Bay, AAR refuel pipes run in close proximity to the Cross-
Feed and SCP pipe work, which contain hot, high pressure air. The fuel pipe-work includes numerous
couplings, is not made of steel, and is not jacketed.
Breach by BAE Systems of Def-Stan 00-970
6.97
6.98
6.99
In my view, when BAE Systems carried out Mod 715 in 1989 to convert the temporary AAR modification (Mod
700) into a permanent modification, it failed to ensure that the whole AAR capability was compliant with
Def-Stan 00-970, in particular, as stated above, it did not ensure that No. 1 tank blow off valve was compliant
with Def-Stan 00-970 or validate the Nimrod refuel system for its new role as part of the AAR capability for
compliance with Def-Stan 00-970.
BAE Systems submitted to the Review that, when introducing Mod 715, it was only required to ensure that
“the AAR refuelling probe and hose down to (but not including) the pre-existing fuel gallery” was compliant
with Def-Stan 00-970. 48 In my view, this is not correct. The requirements of Mod 715 were quite clear, namely,
Part A: “To make provision for and introduce Air to Air Refuelling (AAR) capabilities”; and Part B: “To remove
the SOO (AAR) capability introduced by Mod 700...”. Mod 715 went on to state expressly: “This modification
will re engineer the AAR installation to meet Def-Stan 00-970 CA release requirements” and “Part A of the
modification introduces an AAR capability that meets all the criteria for a full CA Release”.
BAE Systems’ Chief Engineer, Martin Breakell, sought to argue in his evidence to the Review that BAE Systems’
requirement was nonetheless limited by the terms of its Feasibility Study in relation to Mod 71549 which, he
suggested, made it clear that BAE Systems was merely responsible for ensuring that the AAR refuelling probe
and hose added by Mod 700 was compliant with Def-Stan 00-970. In my view, however, there is nothing in the
Feasibility Study to justify this conclusion. Indeed, quite the opposite: the Feasibility Study makes it clear that
BAE Systems was to consider the effect of the AAR capability on the aircraft as a whole and to ensure that it
would meet the requirements of relevant regulations:
45 Volume 1, Chapter 713, paragraph. 4.4.
46 As identified by BAES during the AEW trials (Ref: BAe-MPP-R-AEW-0063).
47 Volume 1, Chapter 704, paragraph 3.4.4.
48 BAE Systems’ Written Submissions dated 9 April 2009, paragraph 280.
49 Report No. 801/MAN/DES/266, dated 15 March 1983.