If the doctors body went overboard minutes before the helicopter took off then why did the doctors body wash up on the beach at least 36 hours before the helicopter arrived at the island? Even if there was a time travel element surely the helicopter would still turn up before the doctors corpse.

The only explanation I can think of is the bearings. If the helicopter follows a certain bearing there would be no time travel but as the corpse obviously couldn't follow a bearing then time travel would take place.

I'm not sure that it is possible to travel to or from the boat without time travelling is it? I thought that happens anyway. If that is possible, that opens up all kinds of problems

True. Even so maybe how much you travel could be determined by the bearings.

Yeah I think that's probably right