|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.