KFC150 Glideslope issue

[YsniperY]

Hi guys, 

I have a Mooney M20K with an HSI and KFC150.  It always passes the auto check fine on the ground and all. My issue is when I’m flying an ILS approach and want the autopilot to fly it. The localizer bars come online many miles out and the plane turns and tracks down that just fine. At about 10 miles out the glide slope bar on the KI206 (secondary VOR/localizer/GS) indicator pops up showing I’m below the glideslope which is normal but the glideslope flag on the HSI is still showing.  After a few more miles and when I’m usually above the glideslope the glideslope bar on the HSI finally decides to wake up. By then it’s too late for it to couple to the autopilot and have the GS light come on and for the autopilot to track the glideslope although it’s still tracking the localizer.  Sometimes I’ll use the control wheel steering button to “nose dive” a bit so the plane will descend down through the glide slope and then the GS light on the autopilot will come on and then it will take over and fly the plane down to the runway.  It’s like the signal to the Glideslope portion of the HSI is weak or something. Isn’t it the same antenna as the KI206? 

 Then today I flew it and the GS light on the autopilot won’t come on at all whether I fly down through the glideslope or not and the autopilot never does connect and follow the glideslope although the localizer is tracking fine. (The GS light isn’t burned out).

 When I took it to the avionics shop about 8 years ago they did an “overhaul” on the HSI and “turned up the signal” whatever that means and said they didn’t see any thing wrong with it although they didn’t fly it.  They said it could be that some moron painted the fin type antennas on the tail with metallic paint.  I removed the paint and it didn’t make much difference plus the KI206 seems to work just fine.  Is it possible to swap the wiring from that portion of the HSI with the KI206 and see if it behaves differently?

Any ideas?

I’d greatly appreciate any help. 

Thanks.  Jay

[m20kmooney]

You may want to call Bob Bramble, Aerolab Aviation Services, (913) 680-4169. He is the specialist on the KI-525-A and KCS-55A components, and also for the KI-256.

 

 

[jackn]

I had a very similar problem. Intermittent problems are a bitch. In my case it turned out to be a bad contact from the circuit board to the push-in type connector. I don’t believe any electronic product uses this type of connector anymore. You might get away with pulling the kfc150, checking/cleaning the connection.

[larryb]

The receiver is the nav radio and displays on the hsi. The antenna is common for both radios. There is a splitter feeding the signal to both radios. Since your #2 works we know the antenna is ok. The problem could be your #1 radio or the antenna cable between the splitter and the radio.

[YsniperY]

7 hours ago, larryb said:

The receiver is the nav radio and displays on the hsi. The antenna is common for both radios. There is a splitter feeding the signal to both radios. Since your #2 works we know the antenna is ok. The problem could be your #1 radio or the antenna cable between the splitter and the radio.

Hey guys thanks for responding.  I talked to an avionics shop not long after posting this and like LarryB stated they think it has to do with the inexperienced avionics installer at a different shop not using the correct splitter or something in the connection from the GNS530 to the HSI. It sounded like something that could be diagnosed and fixed relatively easily. We’ll see I guess.  If anyone else has any experience with this type of thing let me know.  I appreciate it.  Jay 

[Bob Weber]

If it is a 530W, does the vertical guidance respond correctly on the HSI? I would recommend an IFR 4000 test set be used and set it up for ILS and attenuate the signal to compare the sensitivity of the two glideslope receivers. May I assume it has the KI 525A? How does the test page of the 530 display on the HSI? 525A's don't have a spectacular record for glideslope performance.

Bob Weber

webairconsulting.com

[larryb]

Does the HSI and autopilot work correctly for an LPV approach?

[Bob - S50]

We had a similar problem when we first installed the GTN.  During an ILS the GS bug would not come visible until about 2 or 3 miles on final.  The problem was in fact how everything was connected through the splitter.  After it was connected as indicated in the GTN installation manual it worked normally.

[Baker Avionics]

On 12/5/2018 at 4:33 PM, YsniperY said:

Hi guys, 

I have a Mooney M20K with an HSI and KFC150.  It always passes the auto check fine on the ground and all. My issue is when I’m flying an ILS approach and want the autopilot to fly it. The localizer bars come online many miles out and the plane turns and tracks down that just fine. At about 10 miles out the glide slope bar on the KI206 (secondary VOR/localizer/GS) indicator pops up showing I’m below the glideslope which is normal but the glideslope flag on the HSI is still showing.  After a few more miles and when I’m usually above the glideslope the glideslope bar on the HSI finally decides to wake up. By then it’s too late for it to couple to the autopilot and have the GS light come on and for the autopilot to track the glideslope although it’s still tracking the localizer.  Sometimes I’ll use the control wheel steering button to “nose dive” a bit so the plane will descend down through the glide slope and then the GS light on the autopilot will come on and then it will take over and fly the plane down to the runway.  It’s like the signal to the Glideslope portion of the HSI is weak or something. Isn’t it the same antenna as the KI206? 

 Then today I flew it and the GS light on the autopilot won’t come on at all whether I fly down through the glideslope or not and the autopilot never does connect and follow the glideslope although the localizer is tracking fine. (The GS light isn’t burned out).

 When I took it to the avionics shop about 8 years ago they did an “overhaul” on the HSI and “turned up the signal” whatever that means and said they didn’t see any thing wrong with it although they didn’t fly it.  They said it could be that some moron painted the fin type antennas on the tail with metallic paint.  I removed the paint and it didn’t make much difference plus the KI206 seems to work just fine.  Is it possible to swap the wiring from that portion of the HSI with the KI206 and see if it behaves differently?

Any ideas?

I’d greatly appreciate any help. 

Thanks.  Jay

Jay, the "feed" from the GNS-530W to the HSI and the Autopilot are actually the same lines.  They come from the 530W, then spliced into 2 wires and one goes to the HSI and the other to the Autopilot.  The same lines feed both units basically.  I can get you a print of the system if you would like to reference the issue.  Let me know if I can help out.  I would love to.  It seems like it could be the "ILS Energize" line to the AP or a connector not completely seated.  Just a WAG.

[YsniperY]

Hey Guys, I appreciate all of your comments.  My GNS530 is not WAAS yet so I cant do the LPV approach.  When I turn the course selector knob on the HSI the heading matches fine with what's displayed on the 530 test page.  The general consensus that I'm getting from you all is that it's most likely in the wiring/splitter from the 530 to the HSI.  Why the avionics shop didn't check this 7 years ago is beyond me; they came to the conclusion it was the paint but any person doing this type of work should know if the secondary instrument is working fine then it's not the antenna.  geesh.   I appreciate all your help and timely responses!  I hope others with similar issues see these posts and it helps them too.

Thanks again.  Jay