BP, Yes the Lockheed flight computer predicated the drift down performance was recalculated every 2,000 feet for burnoff. They found that they could improve the range by re-calc every 500 ft !!
Of course the aircraft did not know any difference !!!
Re South Africa, the Sikorsky did pasenger/ freight supply to ships going round The Cape Town and they did lose one in the sea so they bought one from San Francisco to replace it. Apparently it was quite a challenge because the ships did not want to slow down or change course so in some cases the choper had to run backward when dropping the load !!!