This kind of movement is related to the
Load Alleviation Function mainly.
The Aileron Droop Function and
Lift Dumping and Phased Lift Dumping Functions are involved as well.
Load Alleviation Function:
The aim of the Load Alleviation Function (LAF) is to alleviate the
fatigue and static loads on the wings by reduction of the wing bending
moment.
The LAF is composed of:
- The Passive Turbulence Alleviation (PTA) and,
- The Active Turbulence Alleviation (ATA).
The Passive Turbulence Alleviation alleviates the static loads in
turbulence and during maneuvers. The activation is based on the
vertical load factor given by normal law. Once the PTA is activated,
it progressively decreases 5 seconds after the triggering condition
disappeared. The computed orders are sent to the ailerons and spoilers
6 to 8.
The pitch compensation linked to the deflections is sent to the inner
elevators.
The Active Turbulence Alleviation alleviates the fatigue and static
loads.
The activation is based on the measurement of the vertical load factor
on the wings given by the accelerometer units installed on the outer
pylons.
The ATA uses the inner and mid ailerons. It can only be activated if:
- The PTA is activated and,
- At a speed above 240 knots.
The ATA orders are added to the PTA orders, and can be added to
the roll orders.
There is no pitch compensation for the ATA.
The LAF is activated above a given speed and vertical acceleration
thresholds but is inhibited when slats and flaps are in full
configuration.
Aileron Droop Function:
The aileron droop function is computed by the lateral law.
When the pilot puts the slat/flap control lever in the position "1" or
more, the Slat Flap control computers send to the PRIMs a "flap out"
signal through ARINC 429.
The PRIMs send deflection orders to the ailerons.
The ailerons droop downward to increase the wing curve.
The ailerons continue to fulfill the roll function
Lift Dumping and Phased Lift Dumping Functions:
The lift dumping and phased lift dumping functions are used to:
- stick the aircraft on ground by suppressing the lift,
- reduce bound risks,
- decelerate the aircraft and,
- give acceptable level of passenger comfort at touch down.
All available spoilers are used for these functions.
Moreover, ailerons contribute to the lift dumping function. The ailerons
move upward.
Rgds