OH NO! This is going to be expensive

[Glen Davis]

OK guys, I few weeks back I post that my KFC-150 would rock left and right when I engaged the autopilot in the heading mode for the first few minutes of engagement, then it would be rock steady.  I got lots of good advice but have not acted on it yet.  Now I have another factor to throw in that might be related.  All advice would be appreciated.

In addition to the lateral rocking for the first few minutes of engagement in the heading mode, now the K I-256 Flight Command Indicator is constantly showing a left-hand turn. And sometimes, it shows a descent. I have included a few photographs (I know everybody loves photographs) showing this situation. In the photographs you will see that the KI 256 is showing a left hand turn while the backup attitude indicator is showing straight and level, the turn and bank indicator is showing straight and level and the six pack on Foreflght display is showing straight level.

In previous post, the blame went to either the gyros in the KI-256 or the brushes in the servo motor.  With this new information about the K I-256 constantly showing a left hand turn, would you now throw all of the blame on the K I-256?

Thank you,

Glen

[carusoam]

Fist step….

We have a pair of resources around here….

@Jake@BevanAviation  Jake is usually quick on the trigger for insight….  (KFC150 challenge)

Best regards,

-a-

[Will.iam]

Does the KI-256 shakeout when first spooling up? Mine tilts about the same as yours but my autopilot flies straight and level on my other instruments. Mine doesn’t shakeout and i have a replacement ki-256 to install the next annual. 

[jaylw314]

I don't recall overhauled KI-256's being horribly expensive if that's actually the issue.  OTOH, that doesn't seem like a huge roll error

[Glen Davis]

While the visual indication on the KI- 256 is not very much, the rocking back-and-forth of the wings during the first five minutes of engagement is at least 20° left and right. Certainly enough to get the passengers attention!


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[Glen Davis]

The price I was quoted to overhaul my instrument was $2500


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[Glen Davis]

I did try to call Jake. Unfortunately he’s on holiday this week. I sent him an email and hopefully I’ll hear from him when he returns.


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[LANCECASPER]

3 hours ago, Glen Davis said:

The price I was quoted to overhaul my instrument was $2500

There are shops that will do it for less than that for sure, but many of the KI256s are 30+ years old. Buying a used one and putting it in is a crap shoot. Plus every time that is swapped, the autopilot should be re-aligned to the attitude indicator (which could  be part of your problem).

I would decide where you plan to be down the road. If you plan on using the Garmin ecosystem, I would seriously consider a GI275 to replace to KI256. When you start thinking that direction, then you start thinking about the aging KG102A remote Gyro in the tail which provides your KCS55A Compass system with heading (KI525 HSI) and then you start looking at two GI275s. Ant then when you start thinking about that you start thinking about G3X, etc, etc, etc. Huge advantages of the GI275 are that you don't need to cut a new panel and that they will work with your KFC150 in the meantime.

Throwing parts at it though without knowing for sure what the problem is, is frustrating and expensive and probably going to make it worse. The odds that a novice is going to get it right by replacing one random piece of the autopilot puzzle are not good. I would be patient and talk to either @Jake@BevanAviation or @Bob Weber before buying anything or doing anything else.

[Rwsavory]

There are many good-used and overhauled units out there for less than $1,000. There are a couple recently overhauled ones on Ebay for less than $800. It pays to shop around. 

[Jake@BevanAviation]

@Glen Davis I sent you a pm on something you could possibly try to narrow it down.  Also, if you can get a video of the oscillation that might give me some clues on the possible issue.  

[Glen Davis]

Will do. Thanks.


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