DIIVS apparently faulty

[BrianB]

I think Lucas may want to read this. My DIIVS, version 2.43, S/N 080715-8000-114-001 was overhauled 7th Dec 2010, Inv 22552, after I zapped the main processor. Since that time, it has behaved impeccably, but now it has the following symptoms:
1. when first switched on, with Alt Hold engaged, it will not keep track and slowly turns right, and keeps on turning. Alt Hold seems to be OK.
2. if I select a HDG to fly by turning the knob, same behaviour.
3. With the "valid GPS signal" showing, and selecting GPS mode, it will not follow the selected GPS track.

Any thoughts Lucas? ..... it has been good until today.. Thank you Brian B.

[TrutrakTech]

Hi Brian,

Is the displayed track on the DG of the autopilot correct?

I want you to check two things. 1) Is the servo actually exerting force on the controls? A broken shear screw could let the aircraft wander where it wills. 2) Try a gyro set the next time you fly. While the aircraft is stationary and with the engine running, AP disengaged, press and hold the knob for about 40 seconds. After that time release and fly as usual. Do not cycle the power on the autopilot. Let me know what you find. Thanks!

[BrianB]

All fixed thanks Lucas, after doing what you suggested. Any idea what was the cause? Thanks for ***istance ... BB

[TrutrakTech]

My guess is a gyro offset was introduced inadvertently. Be sure to power this up on the ground while the aircraft is stationary. Thanks!