The Nimrod Review - Official Documents

Temperatures
4.16
Cross-Feed
SCP 'Elbow'
Fairing
Flying control cables
Figure 4.4: No. 7 Tank Dry Bay (Lower Panel)
Figure 4.5: No. 7 Tank Dry Bay (Internal Drain Holes)
Chapter 4 – Cross-Feed/SCP Duct
Fuel pipe
No. 7 Tank Dry Bay
lower access panel
Wing rear spar
Ribs can allow fuel to
pool before draining
Drain holes above bottom
level of inner skin
The BOI’s theory for the initiation of the fire on XV230 relied on fuel reaching its spontaneous ignition
temperature, or auto-ignition temperature (AIT), 15 on the hot SCP duct. Certain conditions have to be present
for auto-ignition to occur; the surface has to be hot enough and the fuel has to remain in contact long enough
for it to reach ignition temperature before it evaporates or runs off. The hotter the surface, the shorter the
contact time required, but contact time will also be affected by the shape of the surface. Flat surfaces require
lower temperatures than, for example, curved pipes, because fuel does not run off so easily. Other variables also
have an effect on AIT, such as altitude and the temperature of surrounding air. AIT increases with altitude, but
decreases as the ambient temperature increases.
15 The terms ‘spontaneous ignition’ and ‘auto-ignition’ are used in a number of sources to explain the same phenomenon, and for the purposes of
this Report, are considered to be synonymous.
45