Originally Posted by
FCeng84
Starting with 787 Boeing has incorporated wing maneuver load alleviation into its control systems whereby the spanwise lift distribution is managed to be that for efficient, low drag operation when at 1g cruise and more inboard during elevated g maneuvers.
This idea of adjustable span-wise distribution of lift has been around longer than many will think. The Vickers VC-10 had a manually operated switch for an 'Aileron Upset' system, that moved the ailerons symetrically upwards by a couple of degrees during certain phases of flight. This moved the centre of lift on the wings inboard, thereby reducing the wing bending moment, and was mainly used at lower altitudes and heavier weights, when there was more likely to be greater amounts of centreline (fuselage) fuel on board.
In general, once that weight was burned off, the Aileron Upset was switched off. Having Aileron upset applied did, of course, have it's own limiting effect on the aircraft's performance envelope, and when switched off the aircraft's altitude capability was improved. This was due to the extra drag created by having those ailerons a couple of degrees upwards from a more normal free-trail position.
A similar idea was employed on the Handley Page Victor K2. At conversion from bomber to tanker the ailerons were
permanently rigged upwards by a couple of degrees, to shift the centre of lift inboard slightly and relieve wing bending moments. Didn't prevent the ol' beastie from having an Mno of 0.93, or being capable of reaching FL490 (the latter limit was imposed because of oxygen regulators, rather than aerodynamic capability, but that is another story entirely ...).
