King HSI slaving problem

[231Pilot]

The HSI on my M20J started acting strangely yesterday.  While in the slaved mode, the HSI is about 30 degrees off of the indicated heading on the vertical card compass.  I can take it out of the slaved mode and rotate the HSI to a reading that agrees with the compass, but if I re-enter the slaved mode, it is off by 30 degrees again.  This does not make it very easy to fly an approach, or to use the autopilot, or to fly the airplane safely.  It looks like I might have to overhaul the slaving unit....not cheap, but cheaper than a PFD.

Any thoughts?

[Jlocke]

Lew,

I'm going through the same issues on my M20K.  The avionics shop can't find the problem so what they've done is swap parts in an effort to isolate the gremlin.  The put in a new flux gate and HSI and everything worked perfectly.  They then put the original stuff back in and, after a few flights with no problems, the HSI precessed a bit (I was headed west, then turned south, but the HSI kept pointing west though it eventually, slowly came 'round).  After that, they swapped HSI's and it's been working fine.  I'm sure this dance will continue until a it gets isolated.

I did read on the 'net about a similar incident where an owner spent a bunch of money on diagnostics only to eventually find the culprit was a simple connector.

Good luck with it.  I'll let you know what happens as my issues are sorted out.  My guess it it'll involve buying a new whatever costs the most...

[231Pilot]

It looks like changing out the Flux Gate has resolved the problem...but it will take several hours of test flying to be sure that was the only problem.  Not a terrribly expensive repair, all things considered.

[MattS]

Im glad you were able to solve the problem.. Is it bad that I secretly hope that something like this happens to me to justify the purchase of an aspen or G500? 

[Parker_Woodruff]

Matt-

No, it's not a bad thing. But I gave up on waiting for it to happen and did it anyway. ;-)

[jlunseth]

That is exactly the experience I had. Maybe that was me on the Internet. The HSI was wildly off, sometimes over 50 degrees. The issue was a loose connection. We recalibrated it also, but it was not off very far once the connection issue was diagnosed.

[JoeSpeed]

The HSI is driven by the KG102 Gyro. The KG102 uses an optical reader with 360 slots 1 for each degree. When I had the same issue,  it was the KG 102 that needed an overhaul and cleaning. Dust on the card would cause the same problem.  It maybe the HSI needs an overhaul too if it cannot keep up with the KG 102. The slaving system consists of the magnetometer in the wing and the head on the panel. It usually is not the problem, Unless you have magnetized part of the airframe

[davidfreedman]

I'm having the same issue as of today.  Tower must of wondered what the hell I was doing taxiing in circles for 20 mins trying to get my HSI and GPS to agree. 

jlunseth, was the loose connection readily accessible or did you have to open up the panel?

[231Pilot]

Quote: davidfreedman

I'm having the same issue as of today.  Tower must of wondered what the hell I was doing taxiing in circles for 20 mins trying to get my HSI and GPS to agree. 

jlunseth, was the loose connection readily accessible or did you have to open up the panel?

[jlunseth]

My A&P found it so I am not sure where it was.  I vaguely remember it was behind an access panel in the wing.  I think the flux gate is in the left wing on my aircraft.

[davidfreedman]

I found/cleaned the connector and no joy.  Avionics shop estimates $2200-$3900 for a KG102 overhaul depending on what needs to be done.  Ouch.

[231Pilot]

Still much cheaper than a new HSI or a glass upgrade.  As much as I would like to go with some glass, I was relieved when the problem turned out to be relatively inexpensive.  Now I should be able to do the paint upgrade within the year....that could not happen if I was buying a new HSI or an Aspen PFD.

[FlyDave]

Quote: davidfreedman

I found/cleaned the connector and no joy.  Avionics shop estimates $2200-$3900 for a KG102 overhaul depending on what needs to be done.  Ouch.

[davidfreedman]

Lew, don't start talking about an Aspen PFD...I'm almost financially irresponsible enough to go for it:) 

Dave, thank you for the referral!  I'll give them a ring tomorrow and let you know how it goes.

[Immelman]

A KG-102 O/H will not cost that much as long as you have a servicable core (i.e. mod 1 ***on the gyro can***). Call Aerolab aviation, they know the KCS-55A system the best and will help you troubleshoot over the phone.

[conom06d]

Ouch...I am having this problem now as well. Just started happening. Does anyone have an estimated cost on the cleaning on the unit and or fixing the connections? If i have to overhaul it for the price of 2-3K I will just wait and fly with it as a DG. I dont need slaving capabilities that badly.

[Royski]

I've been fighting the same issue intermittently and on top of that my KI-256 is now sending garbage to the autopilot.   So just ordered an Aspen and their EA-100 autopilot adapter (which is supposed to ship later this month) to interface with the KFC-150.

[231Pilot]

Quote: Royski

I've been fighting the same issue intermittently and on top of that my KI-256 is now sending garbage to the autopilot.   So just ordered an Aspen and their EA-100 autopilot adapter (which is supposed to ship later this month) to interface with the KFC-150.

[Royski]

I'm using Shenandoah Avionics.  Todd there has done several other Aspens and says it should take about a week.  I  managed to get Aspen to extend the Oshkosh rebate a bit which helped make the decision.

[Piloto]

The compass offset you describe is typically caused by poor wire contact at the flux sensor. Disconnect the little blue connector on top of the flux sensosr and spray contact cleaner to it. Reconnect and check. It is a good idea to do the same with all the related connectors. Half of the avionics problems are related to contacts oxidation which can be fixed by cleaning the contacts..

José

 

[PTK]

Quote: Piloto

The compass offset you describe is typically caused by poor wire contact at the flux sensor.

[Piloto]

Quote: allsmiles

 Jose, where is this located in the aircraft?  I'd like to clean all contacts as a preventive measure. Thanks.

[davidfreedman]

Here's the conclusion to my story...drove down to Global Tech (Thanks for the tip, Dave) with my 102A and 525 in hand for bench testing.  They agreed to do the tests while I waited as it was a 75 min drive for me.  Both tested solid and they suggested it was likely the flux valve (as many on the board have already commented).  They gave me an overhauled unit for $450 on the condition that I'd send them my old one.  I also had a slight slight errors corrected on the heading bug and glide slope deviation indicator...$200 for what looks like 3 cents worth of metal.  I got out of there for just under 1 AMU after having the metal resanded and painted + knob replaced.

To make the longer part of the story short, first me and then my local avionics shop (Able Avionics at KVNY) removed every conceivable access panel without being able to locate the old flux valve.  A call to very helpful Mooney Headquarters confirmed that it was located 3 panels inboard on the left wing.  This seem unreasonable is it was rivoted rather than screwed.  The shop removed the rivots and there is was.  They modified the access panel for easier removal next time around.  Turns out those were factory rivots. $660 worth of detective work for 2 minute swap out...little frustrating but happy to be back in the air!

[Rod Robertson]

I have the same problem with my Partinavia P68C. The ks55  is slaved and it is ten degrees out. When I try to set it manually it dances around a little bit but settles around ten degrees out. I have taken onboard the comments, thank you and will look at the connections if I can find them.  Has anyone had the problem with their P68C?? Thanks Rod Queensland  Australia 

[carusoam]

Welcome aboard Rod!

We have a few MSers in Australia... 

But, I don’t know if their other plane is a P68C... 

Best regards,

-a-