Roll Trim required message

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Clam
Posts: 40
Joined: Thu Mar 14, 2013 1:10 pm

Roll Trim required message

Post by Clam »

Lately I have been getting "Roll Trim Required" messages, mainly during GNAV mode of GPS course supplied by 430W via AIRINC. Happens both during enroute and terminal operations. When I disconnect the AP, the lateral trim seems in balance and well trimmed. Is there a way I can get more detail on what is driving this message? My HXr with GRT servos does not provide which direction of trim is required laterally (maybe no system do?) or any further detail from what I can find.
Jeff
RV-8 Memphis, TN (KFYE)
jb.flynavy@gmail.com
GRT_Jeff
Posts: 802
Joined: Tue Dec 11, 2012 12:11 am

Re: Roll Trim required message

Post by GRT_Jeff »

Is it still holding courses and turning to new courses or is it also performing poorly? When the EFIS sends a bunch of commands to the servo in a short period of time but the plane doesn't respond, it issues a TRIM REQUIRED alarm. The roll servo doesn't measure force so the EFIS doesn't actually know why the plane isn't moving. If it was working fine before, then the first thing that should be checked is the safety shear screw. If this screw breaks, sometimes the remains have enough friction to keep the arm and base together but not with much force. The screw head may fall off or stay in the hole. If the screw head is still there, you can draw a line down the side of the arm and the cylinder base to see if they separate.
Clam
Posts: 40
Joined: Thu Mar 14, 2013 1:10 pm

Re: Roll Trim required message

Post by Clam »

Thanks for the information. I found that the shear screw was indeed sheared. The screw head easily came out, but I left the body in for now. It appears there is a very small set screw that locks the shear screw?

I don’t see replacement procedures in any manuals and I don’t see where I can purchase a replacement shear screw. Can you point me in the right direction?
Jeff
RV-8 Memphis, TN (KFYE)
jb.flynavy@gmail.com
GRT_Jeff
Posts: 802
Joined: Tue Dec 11, 2012 12:11 am

Re: Roll Trim required message

Post by GRT_Jeff »

You can leave the body in as long as it doesn't interfere with the safety operation. It is held in by red loctite so trying to remove it is not recommended. There are 2 more holes in the cylinder shear base that you can rotate under the arm.

The shear screw is a custom part. You have to order it from us. Contact Jon to get some replacements.

Replacement instructions:

There are 3 shear screw holes in the shear base so you can either rotate the arm or rotate the shear base under the arm to another hole to put in a new shear screw. Use red loctite. Hand tighten just until the screw bottoms out then back 1/4 turn.
Clam
Posts: 40
Joined: Thu Mar 14, 2013 1:10 pm

Re: Roll Trim required message

Post by Clam »

Thanks. This fixed it
Jeff
RV-8 Memphis, TN (KFYE)
jb.flynavy@gmail.com
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