Problem with gyro compass - M20J, Mooney 201

[Johannes]

Hello Mooney Aviators, I have a avionic problem with my Mooney 201, D-EMOA, and want to ask our community, whether anyone knows/had that problem too and could give me a fitting solution.
The gyro compass in my Mooney does not follow the heading when the plane is turning - unimportant if it is moving on the ground or in flight. The EMOA is IFR-equipped and when I change the switch "Slaved - Free" from slaved to free and back the gyro compass gets the right heading but does not follow when the plane is turning again.
A leading german avionic company tried to fix the problem for 5 weeks now - not successfull. They told me, that they replaced every important part...the compass, the switch, the flux valve transmitter, the main compass in the stern...cleaned all the contacts...-> no success until today...
Now I am asked to fly the plane to the HQ of the avionic company for "further attempts to solve the problem"...
->-> Has anyone of you had this problem,too...? or an idea what the reason of the problem could be?...and what I could do to fix it very soon now?...
Thank you all!....

 

Edited September 12, 2017 by Johannes

[jaylw314]

28 minutes ago, Johannes said:

The gyro compass in my Mooney does not follow the heading when the plane is turning - unimportant if it is moving on the ground or in flight.

I assume you mean to say it does work when moving on the ground or in level flight, but not when banked/turning?  I also assume you have a Bendix/King KCS-55A HSI?

The KCS-55A is pretty common, and there might be a shop around that has an extra one they could swap in to troubleshoot.  If a different unit works, that would suggest the problem is he HSI.

[Johannes]

Yes, it is a Bendix/King KCS-55A HSI. No...it does not work, even on the ground or in flight - only when the knob "slave - free" is switched and back again. As you can read, the  german avionic Company tried to replace "everything"...but all units in the Mooney are working correctly....there is not the Problem...and  -> this is the Problem!....we don't know how to proceed...

[carusoam]

Oops, never mind.......

Welcome aboard Johannes.

Please supply the details as requested by jaylw.

Add the number of hours on the instrument and if it has been OHd before.

If it is a BK unit, as Jay surmised, it might be time for an OH.  There is A good shop in the US for that....

Best regards,

-a-

[jaylw314]

All the things you mentioned the shop tried doing are with the magnetometer and its connection to the HSI, but it didn't sound like they did any troubleshooting with the HSI itself.

If it does not even work on the ground, that actually makes it easier to troubleshoot--no need for a test flight to see if a replacement HSI fixes the problem.

[N201MKTurbo]

It sounds like there is a problem in the switch or cabling. Everything works on the bench but not in the plane. When you switch the switch the wires temporarily connect moving the indicator to the correct position.

[Piloto]

At the tailcone (remove large access panel) check the gyro by listening to it spinning when the avionics master is on, no need to run the engine. If you do no hear it spinning the problem may be the gyro itself or it is not getting power.

José

[N201MKTurbo]

3 minutes ago, Piloto said:

At the tailcone (remove large access panel) check the gyro by listening to it spinning when the avionics master is on, no need to run the engine. If you do no hear it spinning the problem may be the gyro itself or it is not getting power.

José

That was my first thought too. It sounds like all the parts have been bench checked. I could be wrong.

[LANCECASPER]

If you've tried all those other things, like Jose says it's probably the KG-102A, which is the unit in the tail section that needs to be at least Inspected and Repaired as Necessary. But other than just checking to make sure it was set on Slaved and not Free, the KG-102A is the first thing they should have checked. If while the master on you hear it spinning but it's very loud then the bearings are bad. If you don't hear it at all it's failed. If you hear just normal gyro spinning noises then it may be ok, or the optical inside could need aligning.

Ask me how I know? I changed out the KI525 and still the problem existed. The KG-102A only takes about a minute to come out of the airplane.

I sent mine to Porter Strait in Tulsa and for less than $350 they replaced an optical component and realigned everything - fair and honest people.

[Aerodon]

I had this problem in my Seneca many years ago.  The system would appear to be working, but occasionally you could start a turn and the HSI would not turn, but then usually catch up with the turn.  Got worse until you could turn 30 degrees before the HSI would start turning and catch up.  Problem was with the KG102A gyro, removed and sent in for repair.  It was not a gyro problem, but an issue with the optical components.

Best is to swap each component out with a borrowed unit - Gyro, then HSI, then fluxgate, then slaving accessory?  My best guess is replace the KG102A, you should be able to find a relatively inexpensive used unit.

Yes, your shop might have looked at all these components, but very few have the bench facilities to test each of these components properly.

Also, check each of these components connectors, if you have a KA51A slaving accessory, the 'card edge' type connector is terrible.  We once found a wire that had been pushed into one of the autopilot connectors and not soldered.  Worked like that for 25 years from the factory.

Any recent work that might have disturbed the wiring?

 

Don

 

 

 

[Bob - S50]

If it turns out to be the KG102A, I would seriously consider replacing the entire heading system (flux valve, gyro, HSI, and slaving meter) with a Garmin G5.  Especially once the GAD29B becomes available.  I'd even be willing to fly without the autopilot for a couple months while I waited for it to be in stock.  The advertised cost of the G5 + GMU11 + GAD29B is $2975 at Sarasota.  Here is the list of items in the KFC system that supposedly now have to be sent into BK.  I wrote to them and got the exchange prices:

KI525A - $2,695.00

KG102A - $2,385.00

KMT112 – Test Only.  Pricing not available.

KS270 - $2,495.00

KS271 - $2,350.00

KS272 - $2,600.00

That's only about an extra $600 to get rid of the mechanical parts and save about 6 or 7 pounds weight.  Of course, there will also be some installation cost.  You'll also get a battery backed up unit that can also be used as an attitude indicator in a pinch (the HSI can be changed to an ADI, but the ADI is not allowed to be changed to an HSI).  You can do that in flight by selecting it from a menu.

[Awqward]

If it turns out to be the KG102A, I would seriously consider replacing the entire heading system (flux valve, gyro, HSI, and slaving meter) with a Garmin G5.  Especially once the GAD29B becomes available.  I'd even be willing to fly without the autopilot for a couple months while I waited for it to be in stock.  The advertised cost of the G5 + GMU11 + GAD29B is $2975 at Sarasota.  Here is the list of items in the KFC system that supposedly now have to be sent into BK.  I wrote to them and got the exchange prices:
KI525A - $2,695.00
KG102A - $2,385.00
KMT112 – Test Only.  Pricing not available.
KS270 - $2,495.00
KS271 - $2,350.00
KS272 - $2,600.00

That's only about an extra $600 to get rid of the mechanical parts and save about 6 or 7 pounds weight.  Of course, there will also be some installation cost.  You'll also get a battery backed up unit that can also be used as an attitude indicator in a pinch (the HSI can be changed to an ADI, but the ADI is not allowed to be changed to an HSI).  You can do that in flight by selecting it from a menu.

The problem (at the moment) is that most aircraft with a KCS55 system will likely have a BK Autopilot....which the G5 cannot provide signals to...



Sent from my iPhone using Tapatalk

[Bob - S50]

3 hours ago, Awqward said:

 

The problem (at the moment) is that most aircraft with a KCS55 system will likely have a BK Autopilot....which the G5 cannot provide signals to...



Sent from my iPhone using Tapatalk

Not yet.  Once the GAD29B is available (soon?), the G5 can replace the HSI and drive the BK autopilots.  You'll still need the ADI though.  But the KG102A is for the HSI, not the ADI.

[M252]

Appear to be having the same problem. On my last IFR flight the KCS55A system just worked fine as it did over years. The slaving mechanisms has always worked for the last 7 years when I bought the 252. I also have a KR87 slaved ADF indicator, which turns perfectly aligned with the slaved HSI.

On my last flight I noticed that both HSI and ADF indicators would not turn. Upon switching slave to free and back to slave both indicators turned as expected. However, at the next turn the same issue happened (no turning). I had to switch slave to free and back to slave to get them moving. On the ground same behavior. Switching the main switch off and on does the same trick, both indicators would correct. It seems that power needs to be interrupted to trigger movement. It seems that KG102A works well, however, the indicators are not fed with the signal to correct unless power is switched off and on again or from slave to free and back to slave. The small indicator next the slave switch does show the delta after turns but corrections only happen as described above (switching main power off/on or slave/free/slave).

I was wondering if someone may have identified the root cause of the culprit??

Thanks!

[m20kmooney]

Problem is in the KG102A. It needs to come out of the airplane to be bench tested and serviced by someone familiar with it. 

Edited January 26, 2019 by m20kmooney

[M252]

Thanks, I will talk to our avionics shop.

[m20kmooney]

3 hours ago, M252 said:

Thanks, I will talk to our avionics shop.

Be sure they have Bendix King manual is 006-05111-0006. 

[M252]

I will check, Thanks

[see_kay]

HI Johannes

Did you manage to resolve this problem?

I seem to have similar with my 252...

Thanks

[carusoam]

9 hours ago, see_kay said:

HI Johannes

Did you manage to resolve this problem?

I seem to have similar with my 252...

Thanks

Unfortunately, Johannes hasn’t been back in a while....

Want too describe what yours is doing?

Best regards,

-a-

[see_kay]

Hi Carusoam, thanks for responding.

I noticed that my KI 525A HSI compass card was not turning with the aircraft - although it had slaved correctly before takeoff.

I did a 're-slave' manually with the slave/free switch and it responded correctly but continued to not turn with the a/c.

The symptoms do sound very similar to those discussed above, so I was considering swapping out the  KG102A as a first step in the diagnosis.

Any suggestions would be welcomed!

C

[carusoam]

See,

I may have encountered a similar challenge with mine...

I spoke with @Alan Fox to test the component in the tail...

Which was convenient... Alan must be about 25nm from my home drome...

It turns out, the component had significant wear, and needed OH/replacement...

Alan is a source for used devices like these... something to consider if you want to keep things running as they are...

Best regards,

-a-

[see_kay]

Thanks A

I spoke to my avionics guy and he agrees with diagnosis and will provide a loan unit while they check out the existing one.

I plan to upgrade the panel in due course (but not yet)

Only a 45 minute flight to YSBK...

Regards

C

[flyer338]

I have had difficulties with my King HSI system as did the previous owner. I decided it made more sense to upgrade. My plane is in the shop for installation of an Aspen Evolution E5 and removal of the vacuum system. I expect to net 10-15 lbs. of useful load. The Aspen is supposed to play well with my KAP-150 and GNS-430.
I will report back.

[see_kay]

The KG102A checked out ok on the bench. Turned out to be corroded contact at KG connector - now rectified. Beware these antiquated connectors that are very difficult to clean and re-connect. (M252 may find this information useful)

They also looked at the WX-11 and found a minor fault in the display power supply - so altogether it was a good day!

I am however considering upgrading to a G500txi so would be interested to hear how others are enjoying this... (Vac system still needed for the speed-brakes)