Is there an allowable limit of trim

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Is there an allowable limit of trim

Postby Bronster » 16 Nov 2017, 04:04

Is there an allowable limit of aileron trim a pilot can use and keep flying with. When does it become a downer. Have a condition where pilot had to keep 1 unit right for 12 hour flight. How much trim is considered a sloppy aileron. And where can I find that in writing. Thanks
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Re: Is there an allowable limit of trim

Postby engineer » 16 Nov 2017, 22:17

Hi, if you have the access to myboeingfleet you can look in the 767-FTD-27-06002. It's for 767 but i think it's possibly to find this info for your aircraft. This is the part of the FTD

Status
We have had operators report "excessive" rudder trim during flight. "Excessive" rudder trim can be caused by numerous conditions, such as surfaces being out of rig, yaw damper shear rivets being partially or fully sheared and improper trimming of the airplane.

One unit of rudder trim will result in 0.3% decrease in fuel mileage.

We do not specify in service aileron and rudder trim limits for the 767 airplane.

Airlines should determine their own definition of “excessive” trim.
Interim Action
If an airplane is experiencing "excessive" trim we suggest verifying that the flight crew is trimming the airplane per the Boeing flight test procedure. The Boeing flight test procedure and aileron and rudder trim limits for new airplanes follows:

Stable cruise.

.8 Mach number.

Equal engine thrust.

Fuel loading laterally balanced.

Hold wings level with control wheel and note turning tendency.

Apply rudder trim to maintain constant heading.

Apply aileron trim to maintain wings level.

Trim limit, 1/2 unit aileron and or 1 unit of rudder trim, also ball slip indicator must be less than 1/16 inch from center.

Operators may want to verify that proper trimming of the airplane is being performed as above to compare the in-service trim requirements vs the Boeing flight test requirements.
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Re: Is there an allowable limit of trim

Postby gorge » 20 Nov 2017, 16:49

boeing thinks aileron trim is economic issue, not safety matter.
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Re: Is there an allowable limit of trim

Postby sjap » 20 Nov 2017, 18:24

There are limits in ch 27 amm for max trim values.

And first of all re-check the aileron cable tension, it is for sure too low. Adjust it, adjust the ailerons to 0 and youlle be fine again.
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Re: Is there an allowable limit of trim

Postby gorge » 21 Nov 2017, 06:53

lateral trim problems can be cause by many aircraft systems (i.e. aileron rigging, rudder rigging, flap rigging, etc.). TheAMM is intended to help the operator identify and correct lateral trim issues. Boeing does not have any trim limits for flight conditions other than those listed in Table 501.
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