Why ground adjustable aileron trim tabs on aircraft w/ roll trim?

SixPapaCharlie

SixPapaCharlie

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Cirrus question... It just occurred to me today that I have both roll trim and also ground adjustable trim tabs on my ailerons.

Seems strange that the tab would be added to a plane with roll trim.
And more specifically a plane where the roll trim is obnoxiously aggressive.
 
Probably for the same reason Boeing's are roll trimmed by adjusting flap track position with aileron trim set to zero. Aileron trim is used to adjust for aircraft loading/balance.
 
SixPapaCharlie said:
Cirrus question... It just occurred to me today that I have both roll trim and also ground adjustable trim tabs on my ailerons.

Seems strange that the tab would be added to a plane with roll trim.
And more specifically a plane where the roll trim is obnoxiously aggressive.
Click to expand...
Hmm. Maybe the roll trim is obnoxiously aggressive because the fixed tabs could use an adjustment. Does your roll trim seem to be working harder in one direction more than the other? Probably a stupid question, I've never flown a plane with roll trim.
 
What Glenn said. Trim tab allows for neutral aileron trim when the plane is evenly balanced while aileron trim hat switch allows adjustments as fuel burns off on one side or due to passenger weight imbalances. It also probably helps reduce drag a bit by allowing the ground rigging to be adjusted vs using one aileron up, one down to fix the issue.
 
RudyP said:
What Glenn said. Trim tab allows for neutral aileron trim when the plane is evenly balanced while aileron trim hat switch allows adjustments as fuel burns off on one side or due to passenger weight imbalances. It also probably helps reduce drag a bit by allowing the ground rigging to be adjusted vs using one aileron up, one down to fix the issue.
Click to expand...
Isn't that what the trim tab would do? Move the aileron up or down a little. These tabs are on the aileron aren't they? Or are they an independent "control surface" attached directly to the wing?
 
The few roll trims I have been acquainted with were all 'very aggressive' or at least, sensitive.
Where you might honk on the rudder trim to center the ball, it was quickly learned that roll trim only received a 'tweak' now and then.
 
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