Yet another G5 question

[jaylw314]

OK, I'm going to ask this question, because I can never remember if my understanding is correct.

Can the Garmin G5 with a GAD29 interface be used as a replacement for a BK KI-525 HSI that is part of a KFC-150 autopilot, and how much has such an install cost?  I'm just interested in the HSI for now, not the attitude indicator, that's a whole other can of worms, I know.

My understanding is that the answer is yes, it's just the G5 as a primary attitude indicator that is a no-go since the flight director functionality on BK autopilots isn't compatible (yet?).

My current situation is that I have a KI-525A where the glideslope indicator over the last few years has been having issues on startup when the GNS530W does its self-test.  At first, it failed without the engine running, but appeared right away when the motor was running.  Over a few years, It seemed like it was taking longer and longer on the initial self test, and recently it has just stopped appearing on the initial test.  It still works in flight, when I've tested RNAV and ILS approaches in VMC, so it seems like there is some stickiness that is shaken loose with the motor running, and now requires enough shaking it only appears with the motor running faster than taxi speeds.  I suppose a bigger problem would be the signal pathway or whatever electric drivers for the needle.

My options at this point (I suspect in order of cost) are:

1. Attempt a repair at an instrument shop -- Repairs are a crapshoot, I know
2. Replace with an overhauled KI-525A --  I'm fairly sure an overhauled KI-525A would be about $3k.  How much has the work to swap one out cost?  IFR recertification?
3. Replace with a new Garmin G5 --  The question at hand?

FWIW, I'm not sold on getting a new G5 since, the upgrade pathway to dual G5 remains unclear for KFC 150's, and I'm not ready to plonk down an order of magnitude larger cost to swap a working autopilot for a new install.  Likewise, replacing the HSI alone makes no headway to removing the vacuum system, so it's not like that's a motivation.

Thanks for any input, gentlepeople!

Edited August 23, 2022 by jaylw314

[Ragsf15e]

Mine is more vote than knowing… you’ll see “yes” often because it can actually interface with a -150, but only to provide heading.  As an attitude source, no.  You’re gonna need a gi-275.

[201Mooniac]

The G5 can replace the HSI but no the AI interface to the KFC-150.  You can use a GI-275 for attitude and either the G5 or GI-275 for HSI.

[jaylw314]

As a follow up to this, I dropped the plane at the shop to do its annual and told them about the INOP glideslope.  I talked to the IA about replacing the KI-525, but I asked if there was a way to bench test it to make sure.  He was actually pretty excited, and said he'd always wanted an excuse to get a diagnostic transmitter.  He also had a spare 530W to compare it to.

When I landed and stopped on the shop's ramp, I ran the 530W self-test one more time, and lo and behold, the GS moved.  Not half-scaled like it was supposed to, but it crept up a little.

A couple days later, my IA called and said they couldn't get the GS to fail.  When they ran the 530W self-test in-situ the first time, the GS went to half-scale.  They used the diagnostic transmitter to test all the receiver functions and everything worked fine.  They wiggled the harness and connectors around, then took out the KI-525 and tested it on the bench with their 530W and harness, same thing.  They re-racked my 530W as well with no change.

Maybe taking it to the shop scared it into working again?  Like taking your cat to the veterinarian, somehow they just KNOW. 

On the flight home, lo and behold, it picks up the GS perfectly again.  I'm under no illusion that it won't fail again sometime in the future, but now I have no idea where to look.  My IA said his gut feeling was that there may be something intermittent with the 530W, but there's nothing to troubleshoot if it's working now, so it looks like replacements/upgrades will be kicked to later down the road.  I'll be avoiding IMC to minimums for a while until I'm confident the GS is reliable

 

 

[N201MKTurbo]

I have found when King needles get stuck, it is almost always the yellow tape they wrap the coil wires on the movements. After 40 or 50 years, the adhesive fails and the tape unwraps. The tape will bind the meter movement. If this is what caused it, it could have eventually unwrapped enough to unbind itself. I have never been into a 525, but I have fixed 3 king VOR heads and they all had this problem. I imagine the 525 was designed by the same folks.

You have to disassemble them further than the service manual authorizes. I have always snipped the offending piece of tape out with surgical scissors.

[Jake@BevanAviation]

It's not uncommon to have the G/S pointer stick on the KI-525.  If the pointer gets stuck you can take the palm of your hand and bump the panel around the instrument.  After bumping the panel they will drop into view and respond correctly until it gets stuck again.  Only way to really fix this is have a instrument shop open the indicator up and clean/repair the G/S pointer assembly.

[jaylw314]

39 minutes ago, Jake@BevanAviation said:

It's not uncommon to have the G/S pointer stick on the KI-525.  If the pointer gets stuck you can take the palm of your hand and bump the panel around the instrument.  After bumping the panel they will drop into view and respond correctly until it gets stuck again.  Only way to really fix this is have a instrument shop open the indicator up and clean/repair the G/S pointer assembly.

You know, the funny thing is I tried doing that a few weeks before, and I noticed the GS needle seemed to wobble freely and return to its hidden position, but it still failed to work afterwards, so I assumed that ruled out a sticking needle.  Maybe it started working as a delayed reaction after smacking it around? 

As an aside, can the KI-525A be repaired, or is it on BK's exchange-only list?

Edited November 17, 2022 by jaylw314

[Jake@BevanAviation]

@jaylw314 It can be repaired, typically we send the sticking needle issues to Mid-Continent instruments for repair.

Edited November 17, 2022 by Jake@BevanAviation

[PT20J]

1 hour ago, Jake@BevanAviation said:

It's not uncommon to have the G/S pointer stick on the KI-525.  If the pointer gets stuck you can take the palm of your hand and bump the panel around the instrument.  After bumping the panel they will drop into view and respond correctly until it gets stuck again.  Only way to really fix this is have a instrument shop open the indicator up and clean/repair the G/S pointer assembly.

On a Mooney, it’s at the bottom of the panel and I use to just reach underneath the panel and tap the case.