SilsoeSid has posted some very interesting information about an ongoing 20kg transfer of fuel after the transfer switches are turned off. Whatever the reason for this quirk of the fuel management system, it might cause a pilot to see fuel flowing and convince him that the transfer switches are on when they are not.
May I suggest that the fuel indications over Dalkeith might have been as follows:
Arrive over Dalkeith with fuel display indicating 47/99/43.
After one minute of task receive and heed transfer pump caution 47/96/43.
Continue task for a further two minutes 47/90/43.
Start to fly back to base, nvg on, check fuel: no cautions, 47/86/43.
Continue flight back to base, no cautions, 47/80/43.
All's well, fuel flowing ok, dark below, so turn lighting down for best nvg vision.
At 47/76/43, unknown to pilot, the supply tanks begin to deplete.
The fuel indications all look good, but it is the run-on 20kg he is seeing. Indicates that the transfer pumps are on and working although they are still switched off.
henry_crun
only a 'white-coated boffin'