I just found this in a Lord Howe Island document.
'Providing the last scheduled flying boat service in the world, the majestic Sandringhams 'Pacific Chieftain', 'Islander' and 'Beachcomber', each able to carry 42 passengers, took off from Rose Bay in Sydney Harbour to touch down in Lord Howe's beautiful lagoon some three hours later. Flights were timed to arrive at the Island one hour before high tide to ensure take-off on the full tide; this meant that departure from Rose Bay often occurred in the early hours of the morning, seeming to add to the romance and drama of the trip.'
The source is here: (A fascinating website)
http://www.lordhoweisland.info/library/transport.pdf
C