The Nimrod Review - Official Documents

Figure 4.13: No. 7 Tank Dry Bay (Design Features)
Breach of design standards applicable in 1969 and 1979 – AvP 970
4.50
Chapter 4 – Cross-Feed/SCP Duct
In my view the original Nimrod designs for the MR1 and MR2 were in breach of design standards applicable in
1969 and 1979.
4.51 As explained in Chapter 2, the Nimrod MR1 was a derivative of the Comet 4C airliner and was designed and
certificated to MOD Specification No. MR254 D&P dated 13 April 1965, which accepted the same certification
base as the MR1. The underlying design specification of the Comet 4C was accepted as being valid, having
been certified in accordance with British Civil Airworthiness Requirements (BCARs), Section D Issue 3, dated 1
July 1956. The changes to the original design were required to comply with AvP 970, the military equivalent of
BCARs. Derogation from AvP 970 was not allowed unless “… the requirements are obviously inapplicable or are
over-ridden by the requirement of the Aeroplane specification.” 64
4.52
4.53
4.54
Inadequate
insulation
No fire
protection
400°C ducts
Those elements of the Nimrod MR1’s design which were specific to the Nimrod (such as the Cross-Feed system
and the bomb-bay empennage) were required to conform to the military AvP 970 issued on 1 May 1958.
As a matter of good engineering practice, it would be extremely unusual (to put it no higher) to co-locate an
exposed source of ignition with a potential source of fuel, unless it was designated a fire zone and provided with
commensurate protection. Nevertheless, this is what occurred within the Nimrod.
It will come as no surprise that the design of the Nimrod Cross-Feed/SCP system was contrary even to the design
standards and regulations applicable at the time of the original design and modifications in 1969 and 1979,
respectively:
64 AvP 970, 1965 Edition, Volume 1, paragraph 1.2.
Design – multiple fuel and vent couplings
Area of No. 7 Tank Dry Bay
Location – bottom of bay
where fuel can pool in tray
57