trex8 From United States of America, joined Nov 2002, 5222 posts, RR: 14 Posted (3 years 1 month 3 weeks 6 days 21 hours ago) and read 2540 times:
The latest Code One magazine from LM has an article on fuel saving developments for LM products and they say a Lift distribution control system with active control of ailerons to shift aerodynamic loading could in one scenario they discussed DOUBLE the range of a C130. They also say the Tristar and C5 have a version already (presumably a 1960s version!).
Being technically challenged I've never heard of this type of system. Is this common on commercial jetliners now being built and does it seem really feasible to double range or is the Hercules such a dog any modern tweak will help!
prebennorholm From Denmark, joined Mar 2000, 6759 posts, RR: 54
Reply 1, posted (3 years 1 month 3 weeks 6 days 19 hours ago) and read 2508 times:
Quoting trex8 (Thread starter): The latest Code One magazine from LM has an article on fuel saving developments for LM products and they say a Lift distribution control system with active control of ailerons to shift aerodynamic loading could in one scenario they discussed DOUBLE the range of a C130.
I put an underline under "in one scenario", because that is what matters here.
That scenario is when the Herc shall move a very heavy load, heavier than what the wing was designed for.
In that case the operational procedures prescribe that fuel is carried in the outer wing tanks to relieve the wing bending moment. That fuel must stay there during the whole flight - it cannot be used, so the range becomes very short.
By lifting the ailerons a little, the lift is more concentrated at the center part of the wing, which gives the same relief to the bending moment. It increases the drag of the wing, but since it now has to fly with a more "nose up" attitude, then the terribly draggy aft fuselage of the Herc accidentally becomes less terrible, so the total drag isn't changed much. That aft fuselage was never designed for minimum drag, but for convenient loading, unloading, dropping paratroopers etc.
The main issue is, that now the fuel in the outer wing tanks can be used - the Herc doesn't any longer need to land with a heavy load of unusable fuel. So in one scenario with a very heavy payload the range goes from extremely short to double of extremely short.
No, that's not the case. But with this small and possible very cheap tweak the Herc gains a little in flexibility, It makes it able to carry a very heavy load, which it was never designed for, over a few hundred miles longer distance than without the tweak.
The same flexibility could be gained by making a stronger wing, with the small disadvantage that a stronger wing would be heavier.
The fact that it works pretty well on the Herc is due to the aft fuselage shape. Doing the same thing on a modern and well streamlined airliner would impose a huge drag penalty, and fuel efficiency would go far south.
Anyway long range airliners can benefit from small adjustments of the ailerons as fuel is burned and therefore the the weight and weight distribution is changed. But no airliner ever has to take off and land with substantial quantities of fuel as ballast in the wing tip tanks. Therefore it is an entirely different issue.
Always keep your number of landings equal to your number of take-offs
trex8 From United States of America, joined Nov 2002, 5222 posts, RR: 14
Reply 2, posted (3 years 1 month 3 weeks 5 days 1 hour ago) and read 2391 times:
Thanks for such a great explanation. One more question,am I correct in thinking of the wing bending moment from the fuel in the outer wings to counter the high weight carried in the fuselage akin to a heavy weight being dropped with paper thin wings and these wings would bend up but if they are weighted at their tips they will stay "down"??