KI-256 part number

[hypertech]

Does anyone have the full part number for the KI-256 used in the 2000 Ovation with KFC-225?

I've been troubleshooting some roll oscillations with the avionics shop.  We might have narrowed it down to the KI-256 needing to be overhauled.  But, I need the full part number used in the Ovation so that he can have one ready for an overhaul exchange to do the swap in one visit to his shop.  There are no services on my home field and I'd rather not make my IA make a trip out just to pull a part number.  The shop is going to pull the STC paperwork for the autopilot to check the part number but I thought it'd be worth checking here as well.

Thanks!

[Aerodon]

4 hours ago, hypertech said:

Does anyone have the full part number for the KI-256 used in the 2000 Ovation with KFC-225?

I've been troubleshooting some roll oscillations with the avionics shop.  We might have narrowed it down to the KI-256 needing to be overhauled.  But, I need the full part number used in the Ovation so that he can have one ready for an overhaul exchange to do the swap in one visit to his shop.  There are no services on my home field and I'd rather not make my IA make a trip out just to pull a part number.  The shop is going to pull the STC paperwork for the autopilot to check the part number but I thought it'd be worth checking here as well.

Thanks!

My roll oscillations were caused by a weak servo.  New one fixed the problem.

[carusoam]

Hypertech,

Which AP Do you have?  

How many hours on the system/plane?

As aerodon has pointed out... the servo motor(s) may need some maintenance... possibly a worn clutch mechanism?

oscilations caused by a single servo might be pretty easy to track down... 

Best regards,

-a-

[hypertech]

It’s a KFC-225 - the digital autopilot with built in gpss (that I finally got working -woohoo).  As far as I can tell the servo has never been changed so about 1200 hours and 18 years on that.  The KI-256 was last overhauled around 2010. That would be something around 500 hours.

Due to the way it behaves, the shop doesn’t think it’s the servo. Primarily in a pitch up attitude like in a climb, it will occasionally go into s turns sometimes rolling over almost 60 degrees to the left. The flight director bars lead the behavior. Pulling the computer breaker and resetting it will typically return to normal operation.  

If I don’t climb, it will operate correctly for hours and do a descent and approach without a problem. 

It may be the roll servo in the end but due to the gentle nature of the turn, the extreme angle, and the flight director behavior along with the resetting of the breaker for the computer - not servos - returning it to normal operation, he doesn’t think it’s the servo. 

We already tried swapping out the computer for a test flight and it didn’t correct it. So the expected culprit now is the attitude indicator. Especially because of the apparent correlation of this happening in pitch up attitudes. 

There are a couple part numbers and so we need the full part number of a KI-256 used in the KFC-225 autopilot in a Mooney. 

[MIm20c]

I have one coming out of a 225 system but we’re postponing the install until the gfc500 is certified.  I’d just look for a 0 degree tilt unit that someone recently removed. Most large shops have a few on the shelf. Spending 3k to overhaul a 256 these days might not be worth it. 

[hypertech]

If I had a choice, I'd do the same.  But my plane is FIKI and so I'm stuck with this at least for a while.

[smccray]

I have a KI 256 P/N 060-0017-01 that was working when removed from my A36.  It drove a KFC 200 if it matters.  Date on the side of the instrument is March 27 2017.  Looks like mods 1-11- happy to share a photo of the label.  I need to sell it.

[Baker Avionics]

@hypertech check you PM.  I sent you the complete Installation Manual for your aircraft of the Autopilot System.  Hope it helps

[MIm20c]

2 hours ago, hypertech said:

If I had a choice, I'd do the same.  But my plane is FIKI and so I'm stuck with this at least for a while.

Same situation, Garmin is working to remove the FIKI limitation around the same time the AP is certified. I’d buy a used 256 with a 30 day warranty, might buy you another 1k hrs for $500-1000. 

Edited November 28, 2018 by MIm20c

[hypertech]

If you have better information than me, that's great news.  The best I could get out of Garmin was maybe they will do something to address the FIKI problem next summer.

[Aerodon]

On 11/28/2018 at 5:31 AM, hypertech said:

It’s a KFC-225 - the digital autopilot with built in gpss (that I finally got working -woohoo).  As far as I can tell the servo has never been changed so about 1200 hours and 18 years on that.  The KI-256 was last overhauled around 2010. That would be something around 500 hours.

Due to the way it behaves, the shop doesn’t think it’s the servo. Primarily in a pitch up attitude like in a climb, it will occasionally go into s turns sometimes rolling over almost 60 degrees to the left. The flight director bars lead the behavior. Pulling the computer breaker and resetting it will typically return to normal operation.  

If I don’t climb, it will operate correctly for hours and do a descent and approach without a problem. 

It may be the roll servo in the end but due to the gentle nature of the turn, the extreme angle, and the flight director behavior along with the resetting of the breaker for the computer - not servos - returning it to normal operation, he doesn’t think it’s the servo. 

We already tried swapping out the computer for a test flight and it didn’t correct it. So the expected culprit now is the attitude indicator. Especially because of the apparent correlation of this happening in pitch up attitudes. 

There are a couple part numbers and so we need the full part number of a KI-256 used in the KFC-225 autopilot in a Mooney. 

The roll problem in my Seneca was much worse in the climb.  Also, if the FD bars are leading the turn, is that not an indicator that the servo is not keeping up?  Seems to me trying another servo is a quicker ‘plug and play’ option the the FD.  I have a FD for you, just send me an email.  Supercub180@gmail.com. Aerodon

[hypertech]

Thanks.  Talked to the shop today and they have my exchange unit in and ready to install.  The shop doesn't think its the roll servo, but if this doesn't fix it I guess we'll be changing that too.  I don't have a whole lot of info on how these things work but his diagnoses makes sense to me.  I don't see how a sluggish servo or tach problem could cause the FD to command a 60 degree bank.  It shouldn't ever go that far so seems like at least something has to be out of whack with the KI-256.

[Jerry 5TJ]

I assume that when you say the  “FD leads the turn” it means the plane is following the FD commands.  That implies the servos are working.  You have already swapped the KC225 leaving just the KI-256 as the source of pitch error.   As you already suspect.  

The KI-256 is the most failure-prone component in the original KFC225 system.  

Once you replace the KI-256 with a solid-state AHRS the next highest on the probable failures list is the KS270C pitch servo.  

 

[hypertech]

Yes, that's right.  It departs level flight by the flight director moving to a bank angle and the plane following the flight director's lead.  Sometimes if I override with CWS and put it back to a level orientation, it will return to normal control and sometimes there is no convincing it and it has to be shut off / breaker pulled.  

A solid state AHRS would be great but that's a ways off yet.

[carusoam]

Jerry,

Just wondering...

What’s on your current panel?  Classic BK needles or All Glass?  

Note for others... Jerry know his instruments, deeply...

Best regards,

-a-