Aileron trim: a question to Jan

[Syl20]

Hello Jan,

I have a couple of questions concerning the aileron trim of the 737-300.

I heard that it is not normal procedure to use it while flying, but I wonder:

- Under which circumstances is it used?

- How do I see the actual trim value of the aileron (how do I know that it is centered)?

 

Thanks in advance.

 

Cheers

Sylvain

Edited July 21, 2017 by Syl20

[Poweer]

I know I'm not Jan, but I'll try to answer as far as I know. 

Aileron trim is used when for whatever reason your aircraft is abnormally banking to one side or another. Then you use aileron trim - there are two switches. BOTH must be operated at the same time (one gives power, the other gives ground to the actuator). And the only indication is the phisical movement of the control wheel (on the yoke) and it will change the neutral position which you can read from the scale on the top of the yoke column.

Edited July 21, 2017 by Poweer

[Syl20]

Thanks Poweer, these seems very logical explanations.

I wonder why I wasn't able to figure it out by myself ;-) ...

[Litjan]

Poweer is right.

Aileron trim is RARELY used on the 737 - as it limits your available aileron travel (which you may need in strong crosswinds). So if the plane constantly banks, you need to find out why (and rectify that). Small banking tendencies can be countered with the rudder (even though that results in a bit of uncoordination).

The correct trim procedure, however, is like this:

Fly straight and level, make sure N1´s and wingtank fuel levels are the same. Maintain wings level with aileron, stop any turning tendency (yaw) with rudder-trim. Then use aileron trim if needed. For more than one unit (see top of yoke), make a maintenance entry.

Jan

 

[Syl20]

Thanks Jan,

Crystal clear explanation as usual :-)

Cheers

Syl