Airbus LAF

[rudderrudderrat]

Hi,

Can someone explain what LAF (Load Alleviation Function) is?

There are references to LAF in my A320 FCOM but no explanation as to what it did when it was fitted.

I gather the A380 has it fitted.

Thanks

[spook]

A computer implemented method, apparatus, and computer usable program product for symmetric and anti-symmetric control of aircraft flight control surfaces to reduce wing-body loads. Commands are sent to symmetrically deploy outboard control surfaces to shift wing air-loads inboard based on airplane state and speed brake deployment. Surface rate retraction on a wing with peak loads is limited to reduce maximum loads due to wheel checkback accompanied by utilization of opposite wing control surfaces to retain roll characteristics. Airloads are shifted inboard on a swept wing to move the center of pressure forward, thereby reducing the tail load required to perform a positive gravity maneuver. In a negative gravity maneuver, speed brakes are retracted, thereby reducing the positive tail load and reducing the aft body design loads. High gain feedback commands are filtered from wing structural modes above one hertz by a set of linear and non-linear filters.

Source: WING-BODY LOAD ALLEVIATION FOR AIRCRAFT - Patent application - computer implemented method apparatus and computer usable program product for symmetric and anti-symmetric (http://www.faqs.org/patents/app/20090292405#ixzz0teElRr9f)

[Swedish Steve]

Our oldest A320, built in 1987/88 have LAF accumulators. Two in each wing connected to two spoilers in each wing. They were tiny little hyd px vessels that always needed servicing. When LAF occured, they pushed up the four spoilers together to alleviate the load in the wing.
Our later A320 built in 1999 do not have them.
No accumulators, no problem, but is LAF still active?
I think that Airbus removed the system on later build aircraft because they found it wasn't needed?

[rudderrudderrat]

Thanks guys.

[fantom]

You're all wrong.

To hear the LAF operating, turn up the speaker switch and it goes : 'hahahaha'.

True.

[FE Hoppy]

Before 411 gets in the act I'll quickly say that the L1011-500 had a similar system called ACS which used the outboard ailerons to offload the wing either symmetrically or asymmetrically.

[TO MEMO]

Spooks explanation is preatty much it! The link is very interesting and its worth reading it!

A320s no longer have LAF. LAF was removed from A320s around 1998, global solution, airbus said. That`s why the old ones have the actuators, but system is disabled and new A320s no longer have the actuators.

[ampclamp]

yes the older 320's had it.
It used some of the spoilers and ailerons to unload the wing.Accumulators assisted with the very rapid movement required up to around 300 degrees per second ( been few years so not sure of exact numbers).
the mech guys were regularly topping up the accumulators.

[Dan Winterland]

My company has had all the LAF systems removed in our older aircraft.

[screwdriver]

yes the older 320's had it.
It used some of the spoilers and ailerons to unload the wing.

Correct. It's only active with a clean wing and reduces wing loading. BA's older CFM powered a/c still have it. I seem to remember reading last year that Airbus are considering re introducing it. The 380 does have it.
:ok:

[Slasher]

So why did they dump the LAF then? Unless Im missing
something it wouldve been quite useful (and assuring)
when cutting through a bloodey great line of thunderys.