Originally Posted by
TWOTBAGS
With 4000hr in Twin Otters ill say this (yes its a long tine going nowhere)
Standard Fuel capacity is a little over 2400lb, PT-6's (-27/-34) plan on 600lb/hr all day every day doing utility work low level
at regular MTOW 12,500lb and an high (dont laugh) cruise FL100+ you can get fuel flows down to the 520lb/hr mark.
With a ferry permit the highest weight i've seen was 17500lb, it used a lot of runway and a lot higher than usual take off speed. If you lost one on departure then close the other throttle and land ...... wherever that is. Our ferry kit in the day was a wood base with the cut out for a bunch of 44 gal drums connected by 2 inch hose that fed a manifold into the two under floor tanks.
Any ferry was preceded by a flight test to ensure the ferry set up would work and there were no blockages. Usually we would climb on the mains for 90 min after departure then open the feed on the ferry tanks and see if the fuel gauges increased, if not we'd turn back.
My opinion in this case is for whatever reason the ferry set up would not feed the main tanks, The crew exhausted there mains and were screwed after that.
I agree with your practice of testing the ferry system. When I did a solo crossing in a Twin Comanche I removed most of the interior seats and had 3 fuel tanks in the cockpit. Two where the back seat would be, and one where the co-pilot would normally sit. I put 5 gallons of fuel in each tank and flew a test flight to confirm I could feed fuel from each tank and that I could get down to at most 5 gallons left in each tank.
I'm struggling with what the pilots went through when they knew they could not feed from the ferry system. They went too far into their ferry flight before they discovered they were not feeding from the ferry fuel system. Based on the math in my last post, it seems pretty clear they flew the mains dry. Not being able to get out of the aircraft after ditching is puzzling, but perhaps there was not much attention paid to securing the fuel bladders. If that was the case, then when they ditched the bladders may have come forward and trapped them or rendered them unconscious.
It is all very sad.