A320 aileron trim

[NorthSouth]

Flying out of Heathrow on an A320 the other day I noticed that on the climbout a significant amount of left aileron trim was required to keep the aircraft wings level. Then in the cruise the ailerons seemed to be set with a slight right roll input, while in the descent rather more right aileron was required.

Why the changes? Are they airspeed-related? Or are there torque-driven trim changes with changes in power setting?Please help a poor confused SEP instructor.

[JABBARA]

If I understand you correctly, here is the answer:
(Sorry for my English if it s diffucult to understand)
The airplane is designed so that when the ailerons are flush with wings, the airplane should fly wings level with horizon. This is true only therotically. But in real life, this never hapens or is extremly rare. First of all, in the manufacturing phase, the airplane cannot be built as exactly (with zero error) as in the blue print or CATIA. If very luckily this happens, this is called as
"in-rig" airplane and while flying with this airplane you can see the ailerons are almost flush with the wing. Even this is only possible as asuming the engines are producing exactly same amount of thrust (for twins), the fuel in the wing tanks are weighing same and there is no yawing moment induced by rudder, tail or any other component of the airplane. Since coinciding these parameters are very difficult, for any type of airplane, you will keep seeing deflected ailerons varying their positions depending on the phase of flight, regardless it is a highly sophisticated fly-by wire A 320 or Cessna R 172.

[Wino]

A320 ailerons also droop a little with certain flap and slat positions, sooooooooo you could be looking at that as well.


Cheers
Wino

[NorthSouth]

Wino:A320 ailerons also droop a little with certain flap and slat positionsAh, that's it - probably still had some flap deployed when I was looking on the climbout. The right trim in the descent was small enough to be explained by discrepancies in power setting etc.

Thanks guys

[Pegasus77]

Hi all,

After a few thousand cycles no airplane is exactly like it was in the beginning. We have some 321 which fly with 1,5 degree of bank in cruise flight.

In cruise flight the autopilot uses ruddertrim to zero out the forces, causing the above mentioned bank angle, and thus keeping the ailerons aligned with the wing. When taking over manually you'll notice (if you zero out the rudder trim, or if you decrease speed in the approach) that the roll rate command of the side stick will cause a slight aileron deflection to keep the roll rate zero. You can notice this behaviour on the FCTL-page on the ECAM.


P77

[square leg]

Just to be pedantic:

Normally ELAC 1 controls the ailerons and is also responsible for the 5° droop when FLAPS are set. (ELAC 2 normally controls the elevators).

[SKYYACHT]

You also have to remember that the ailerons are locked out at higher speeds, so roll control is by way of differential speed brakes.


Tailwinds