VOR Problem - M20J King KCS-55A Garmin 530W

[base698]

About 2.5 months ago we got a G5 installed to replace a bad CastleBerry standby attitude indicator.  About 2 months ago, while doing a practice approach, I noticed the CDI on the number 1 (King HSI) was centered, but was quite offset according to the GPS.  ATC told me I was offset, which corroborated the what I was seeing.  My wife also doing the same approach noticed the same thing.  During RNAV and ILS/LOC approaches there is no offset.  The 530W and CDI match.  We decided to have the shop look at it that installed the G5.  They couldn't really find the problem but concluded it must be the Nav board, so they sent the 530 to Garmin.  It came back and they said it was good to go.  On the flight home we were flying a known radial and noticed it was still bad.  We switched to VOR2 and flew the known radial.  It was sending us wrong as well.  Now both VORs seem borked.  We sent the plane back to the shop.  Now they are saying the HSI is bad, which we've never seen a problem with the HSI--two IFR checkrides and lots of approaches ILS, RNAV and never had a problem.  We are going to bring the plane home and send it elsewhere at this point.

TL;DR: Borked VOR 1/2, CDI on KI525 HSI works with RNAV/ILS, Shop says it's HSI

Two questions:  Any ideas on what could cause the VORs to be borked but CDI still work for RNAV/ILS/LOC?  Where would you recommend taking it in Southern California?

Thanks!  

The joys of ownership

 

[ArtVandelay]

I’m leaning towards an antenna (or it’s wiring) is the issue. They should have a test box to simulate signals on the ground, did they do a ground test?

[kortopates]

What does your VOT test show you in terms of number of degrees off?

What does your 530 on the startup pre-flight test show for how close the CDI is to what the 530 displays for CDI course?

These should have been the first checks and should isolate the issue, besides being required checks for IFR flight.

ILS, LOC & GPS course guidance should always work fine since it doesn't matter where there OBS selector is positioned.

Only VOR nav and GPS via OBS actually matter where the OBS is position for course guidance.

If the VOT test fails, there is a resolver in the HSI that needs to be re-calibrated

If the GPS is CDI is off (for OBS usage) then the GPS can be put in setup mode and re-calibrated, and if still off the issue should lie in the resolver along with failing the VOT test.

[Jerry 5TJ]

If the 530 receives LOC signals then the antenna is adequate as it’s the same input for VOR reception.  

I’m inclined to suspect the HSI.  

The KI-525 left-right needle drive circuit sounds normal.  During ILS and GPS RNAV the deviation signals drive the needle directly.  During VOR operation the KI-525a CDI resolver circuitry processes the signal before it drives the L-R needle.  That electro-mechanical assembly is likely the source of a fixed degree offset.  

All you want to know about KI-525 operation Maintenance Manual

Time for a second G5 & ditch the KI-525?

(Where to take your KI-525 in Southern California?  How about half-way to Catalina? )

[Aerodon]

I'm having a problem with both VOR's showing the same error.  But what #2 Nav do you have?  First step is to go to a VOT or known VOR test point and see what is going on.  Its been a while, but I know the SL30 could be calibrated to the VOR resolver - I'm not sure about the GNS430.  

Seems to me, you should check the calibration of both Nav's first, before sending out any more parts.

 

Don

 

[Marcopolo]

23 minutes ago, kortopates said:

These should have been the first checks and should isolate the issue, besides being required checks for IFR flight.

Hi Paul,

 

  Based on the thread title, the OP has a 530W,  I thought the required 30 day VOR checks went away with WAAS.  Am I wrong?

 

  I agree that this check should have been a first step in the OPs troubleshooting tree, just curious about the IFR required/legality statement.

 

Ron

[kortopates]

51 minutes ago, Marcopolo said:

Hi Paul,

 

  Based on the thread title, the OP has a 530W,  I thought the required 30 day VOR checks went away with WAAS.  Am I wrong?

 

  I agree that this check should have been a first step in the OPs troubleshooting tree, just curious about the IFR required/legality statement.

 

Ron

Although you don't need to use VOR navigation in the enroute structure, you still do need a current VOR test to fly any VOR approach since you need to have the raw signal displayed when navigating from the FAF to the runway. I assume that is what the OP was doing when he says it was off on a practice approach (but does not mention type of approach) but was not offset when doing RNAV and LOC approaches. Without a current VOT/VOR test, you would be limiting yourself to no VOR approaches, which might be operationally fine for you; except if you loose GPS for any reason since its still also our backup form of nav. But most of us train for proficiency in all kinds of approaches even though I wouldn't personally fly a VOR approach when I have a GPS approach option.

Edited February 6, 2018 by kortopates

[Marcopolo]

Thank you for the clarification,  Now back to our regularly scheduled program, sorry for the tangent!

 

Ron

[carqwik]

FWIW - For 15 years, the VOR guidance on my KI-525 was off by ~15 degrees...despite several shops "tuning" the KX-165 which drives it.  My 2nd VOR - (I think it's a KI-206?) - driven by the KX-155 worked perfectly.  So I gave up trying to fix the #1...figured it worked for ILS/LOC approaches (as Jerry5TJ described above as it's driven directly) and the #2 VOR worked fine in case the GPS went out. Then the #2 VOR got weird.  Called Bevan-Rabell in Wichita.  They had me send in the -525 (for the #1 VOR) and the KX-155 (for the #2 VOR).  Came back a week later and both worked perfectly!!

My guess is you need to get your -525 fixed.