The IAI1124 uses hydraulic pressure to keep the gear up. There is no mechanical uplock.
As soon as the hydraulics are breached from the gear side, the gear comes down. It's fairly heavy and will swing down and locked quite easily... even without using the blow down bottle. (I've seen it first hand while dealing with a complete hydraulics failure on a Westwind...)
Chimbu does have a point about aircraft selection, however I believe the Westwind is suitable for this type of operation. Quite simply, if one goes to a remote island constantly, without a plan B (alternate), eventually one will get bitten. Who cares what the law says, its bloody common sense! Just because it's legal, doesn't make it a good idea!
That was about 1 hour worth of fuel that was not taken by not filling those tip tanks. More than enough for one approach and diversion to NWWW.
As for that bad excuse of a joke as Director of Civil Aviation, I'm sure he would be quite happy if we all started planning our RPT ops using manual calculations for oceanic flights. "Back in my day..." yes well back in your day, you probably had a navigator and radio operator too.
Still, it was quite a shock to read in the special audit report that there was no specific flight planning method for the Westwinds nor could the software under consideration consider enroute winds. If you can't afford or just won't pay for the proper tools (UVAir etc), then you shouldn't be doing that sort of operation. Fanging around from Darwin-Alice-Adelaide is completely different to long overwater oceanic routes...