Wing bending relief
 

Can anybody help me with this topic. I understand that it has to do with ZFW, but an explanation would be great.

Thanks FF

At higher AUWs, the ailerons are deflected upwards to move the lateral (spanwise) centre of pressure inwards to take they strain off the outer part of the wing.

Not all aircraft have it. The VC10 was the first to my knowledge, it is simply a switch which moves the ailerons up about 8 degrees. It is switched manually at certain
weights and altitudes.

The Tristar took it a step further with an automated system, and the modern state of the art system is the A330/340s Manouevre Load Alleviation, but someone else will have to explain that.

Wing bending relief is a bit of a catch-all. It covers active ailerons, fuel loading/burn sequences, pod-mounted engines, tip tanks etc.
In effect it can be thought of as anything that allows the wing to utilise that which must occur to allow lighter structure. Things like burning fuselage tank fuel first, outboard wing tank fuel last, loading wing fuel first, fuselage fuel last. Pod engs get unavoidable weight outboard where they help to oppose the lift forces. Lighter structure is the guts of it - less structural weight allows more payload.
Am I making sense for you FuelFlow??? :)

Helps fatigue counts no end as well.
JF

Maneuver Load Alleviation, as mentioned earlier relates to a high speed, high loading demand, where some of the outer spoilers, and the ailerons, are deflected upward to alleviate stress/bending. Wing bending relief, I think, relate more to the situ. that Mustapha mentioned. The 330/340 series burn tip tanks last, wing tanks second last.

The 747 also burns the tip reserve tanks last, to preserve wing bending relief. If the tanks were leaking into the mains, it was a 'no despatch' job.(Notice came out from Boeing)

Wing bending relief was designed and in use with the DC-4 (yes indeed folks, that far back) and its purpose was to relieve strain at the wing/fuselage and inner/outer wing attach points and allowed for lighter wing structure/higher payload. It was improved with later models of the Douglas piston line (DC-6 & DC-7) and especially the DC-7C with its much larger fuel capacity. When the jets arrived (DC-8 & 707) wing bending relief provided much larger fuel supplies to be carried and on the intercontinental models the weight of the fuel exceeded the empty weight of the aircraft for the first time.

Of course wing bending releif is also acheived by hanging heavy items such as engines off the wings. Which is probably the reason the VC10 needed it's aileron upset system.

Load alleviation was fitted to the 320 but no longer.
Airbus have obviously decided it's a waste of time on that type.

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Thanks to all those who responded.
I managed to find a reference in Handling The Big Jets.
Thanks again to all of you.