KAP 150 Heading Adjustment

[PT20J]

Does @Jake@BevanAviation or anyone else know how to adjust the heading on the KC 191? In HDG mode, it is off about +4 deg from the heading bug on the Aspen EFD 1000. There is a hole for a trim pot on the front panel to adjust wings level when not in HDG hold and I set that, but I don't know how to trim the HDG hold. 

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[Jake@BevanAviation]

If the aircraft is consistently off 4 deg from the heading bug when tracking HDG, check how it tracks with just wings level mode.  If the wings are not level adjust the RN pot.  Just be careful to not break the pot when inserting a small flat blade screwdriver. Adjusting the RN pot can potentially cause other modes to be off as this is a attitude trim pot. In theory if the aircraft can fly wings level with no issues adding in an additional nulled lateral command should produce no roll correction command.  There are some internal adjustments for the roll servo null command but that would need to be checked on the bench or with the flight line tester before adjusting anything.

NOTE: heading, course, nav deviation and roll cross-feed errors are all summed by the roll microprocessor.  The only adjustment pot you get before the errors get summed is for NAV deviation.  This is the reason why the unit needs to be checked with a test set prior to adjusting any internal pots.  If you adjust the roll summed error it will effect all lateral modes.

[PT20J]

On 1/25/2021 at 6:17 AM, Jake@BevanAviation said:

If the aircraft is consistently off 4 deg from the heading bug when tracking HDG, check how it tracks with just wings level mode.  If the wings are not level adjust the RN pot.  Just be careful to not break the pot when inserting a small flat blade screwdriver. Adjusting the RN pot can potentially cause other modes to be off as this is a attitude trim pot. In theory if the aircraft can fly wings level with no issues adding in an additional nulled lateral command should produce no roll correction command.  There are some internal adjustments for the roll servo null command but that would need to be checked on the bench or with the flight line tester before adjusting anything.

NOTE: heading, course, nav deviation and roll cross-feed errors are all summed by the roll microprocessor.  The only adjustment pot you get before the errors get summed is for NAV deviation.  This is the reason why the unit needs to be checked with a test set prior to adjusting any internal pots.  If you adjust the roll summed error it will effect all lateral modes.

Thanks, Jake. I thought I had the pot adjusted correctly, but I did it again letting it settle longer in smooth air. Now the heading hold is within 1 deg.

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