Twin Otter main fuel tanks are in the belly. Wing tanks are an option and only hold 88 gallons - about an hours worth of fuel. Mains plus wing tanks gives a bit under six hours fuel, about the same time as they were airborne. That is the only reason I would assume they had wing tanks. At this point I would be quite surprised if there was an issue with the standard or optional fuel systems (ie it appears to be an issue with the ferry tank installation).
Wing tanks can be refuelled over the wing, but due to the height the 'standard' is to use the fuel pumps to transfer fuel from the mains to the wing tanks on the ground.
100LL burns a little more per hour than JET-A if I am not mistaken, but otherwise is a non-event unless you burn it for more than 150 hours.
The FAA registry shows Turtle Pacs installed in 2015. Nothing saying they used a different ferry tank system this time, though.
Last edited by StudentPilot479; 27th May 2023 at 01:15.