The Nimrod Review - Official Documents

The Nimrod Review
74
Figure 5.8: Fuel Seals in the No. 7 Tank Dry Bay (NB: not all couplings are visible in this diagram)
Maintenance Policy and Regulations
‘Corrective’ Maintenance
5.10
5.11
The majority of the Nimrod fuel system is maintained under a policy of Corrective Maintenance. Corrective
Maintenance is defined as: “...all those maintenance activities required to return an aircraft or equipment to a
serviceable state following an unscheduled arising”. 9
In the case of the Nimrod fuel system, Corrective Maintenance has meant that items such as pipes, couplings
and seals were only replaced if they were observed to be faulty, either due to visible damage or corrosion, or
because they were actually leaking. Also, the MOD, in common with other operators, operates a strict ‘one use
only’ policy for seals, i.e. when a coupling is removed for any reason the used seal is discarded and replaced
with a new one. Elements of the fuel system are dismantled during Major maintenance to allow access to other
systems; as a result, almost half of the aircraft’s fuel seals were, in practice, replaced every five years. 10 Since the
loss of XV230, however, and following the results of a Fuel System Safety Review undertaken by QinetiQ, 11 the
Nimrod Integrated Project Team (IPT) decided to replace 42 fuel seals on each aircraft in the Nimrod fleet, being
those seals which are not disturbed during Major maintenance, but which are located primarily in the centre
section of the aircraft where any leak is deemed to be particularly undesirable. 12
What is the military and civilian practice worldwide regarding fuel seal replacement?
5.12
FRS Seals
Avimo seal
My researches and inquiries have found that the Nimrod fuel system maintenance and seal replacement policy
(which reflects the maintenance policy throughout the RAF) is little different to that of other military and civilian
operators worldwide. The United States Air Force (USAF), Royal Australian Air Force and Canadian Defence
Forces do not ‘hard life’ fuel seals. 13 I have found no overarching policy for routine seal replacement within the
civilian world.
9 JAP 100A-01 Issue 17, Chapter 5.4, paragraph 1.1.
10 Once a coupling is dismantled, its seal is always discarded and replaced.
11 Nimrod Fuel System Safety Review Report (Q/CHC/1/2/N1), dated October 2007.
12 Known as the Fuel Seal Replacement Programme (FSRP).
13 BOI Report Exhibit 77, DE&S(WYT)/366/8/2/CASD dated 22 November 2007 and USAF Air Force Response to Questions From the Nimrod Review.