Hi Dougie, I think the weight on wheels switch was hooked in to the parachute bomb rack selector switch on the flight deck.
Ken, Our J has the early generation Brooks and Perkins with the bicycle chains and operating leavers. (No electrical interlocks at all) If I recall the port side lever had to be operated to open ALL. two levers on the Port side, one to shuttle the bicycle chain which enabled the individual latches to be selected open or close. the The Stbd lever was operated to EMERG to release the springs on all of the airdrop latches operated a shaft with a series of cam followers to jettison the load in either a true airborne emergency (Pallet on fire) or Combat Offload.
I think the HOEU did pay on the grass at Lyneham letting a few pallets go. The 463L pallets were in short supply (like Rocking horse s#it) following a debacle betwixt AAR Cadilac/Capewell and Amsafe Bridport who were fitting them up in the UK. I think dropping a pallet off the ramp rendered it unsuitable for further use hence the ones Ksim speaks of. I think these fell out of the DRAS (Dual row airdrop system) 88 x 108 on the C17 cheaper than a Type V and more effective than a double row of 48" wide CDS.