Capturing Glideslope with KFC 225

[CaptainBen]

Hi folks. I posted this in the Avionics forum, but sharing here as well. I have a question about using the KFC225 autopilot (2004 Ovation) on instrument approaches. Everything seems to be working, except when I press the "APR" button, it's not capturing the glideslope (ILS or RNAV LPV). I'm sure it's user error and I'm probably just not using the right sequence. The KFC 225 user manual isn't very helpful, so reaching out here to see if I can get some insights from y'all. Here's the sequence I've been following:

1) With the flight plan and approach activated on my Garmin 430, press "FD", NAV", and "AP" on the autopilot and use altitude pre-select for IAF altitude. The autopilot tracks the GPS course to the IAF, levels off at altitude, and turns on the approach course.

2) Use altitude pre-select and VS/DOWN buttons to descend to step-down altitudes between fixes. The airplane descends and levels off as appropriate.

3) At last waypoint / fix BEFORE the FAF, use the VS/DOWN button to continue descent to FAF altitude

4) When I see the glideslope come alive above me, press "APR"

When following the above sequence, the airplane just continues descending right through the glideslope after crossing the FAF.

Any suggestions? Appreciate your help!

[Fritz1]

flying towards the FAF on NAV and ALT, i.e. you have reached the intercept altitude press APR, you feel how the autopilot is tracking the localizer more aggressively, GS armed should appear on the display, at the FAF the display switches from GS armed to GS and the airplane follows the glidepath, think you have to be in ALT mode to arm the GS, at least this is how it works for me

[NickG]

Is the VS setting overriding the GS?

[Jackk]

One trick on flying a ILS on most APs

 

 If cleared a ILS approach dial in the FAF altitude, heading to an intercept, or direct to whatever fix, arm aprch mode, once it swaps, or you swap, from the GPS to ILS at the FAF it should be good.

 

 But hitting the FAF on lateral and vertical target helps as if you’re too high sometimes it won’t do the “hand off”

 

That said it’s been a hot minute since I was behind a KFC225

[CaptainBen]

23 hours ago, NickG said:

Is the VS setting overriding the GS?

Yes I think this is what's happening... I'm in VS mode descending down to FAF altitude. Before reaching the FAF I see the glideslope come alive (above me) and press APR, but the plane continues to descend at the VS rate and doesn't capture the GS.

[midlifeflyer]

6 hours ago, CaptainBen said:

Yes I think this is what's happening... I'm in VS mode descending down to FAF altitude. Before reaching the FAF I see the glideslope come alive (above me) and press APR, but the plane continues to descend at the VS rate and doesn't capture the GS.

Right. It’s not really “overriding.” The glideslope was above you in VS mode and it remained above you because you told it to descend. You never told the AP to level off. Or reduce the descent rate.  How could it capture?

[skykrawler]

The implication is you are below the glideslope intercept altitude and descending at the glideslope intercept point on the approach course.

You really want the system to be in approach mode on the inbound course several miles before the FAF.

If the glideslope indicator is alive and above, do alt hold or reduce your descent rate.   If approach mode is active,  as the GS pointer comes down zero deflection the system should transition to GS capture.

Many approaches have a level segment before the FAF which is also the GS intercept point.  Those that don't require more planning.

Here is an example: https://aeronav.faa.gov/d-tpp/2512/00957R2.PDF

Descending from NUTTY you probably want the gear down rather than waiting for the PFAF/FAF - because you'll have a speed control problem.  The LPV will give you vertical guidance somewhere past NUTTY that will put you on the glidepath before BCOAT.  Two choices, hold altitude at NUTTY to intercept GS, or dive and drive to 1700 for intercept at BCOAT.

 

[Fly Boomer]

On 11/28/2025 at 10:51 AM, CaptainBen said:

Any suggestions? Appreciate your help!

Not sure if this is your issue, but this article from Max Trescott's email blast sounded similar:

GPS Approach Glidepath Capture Failures

Have you ever flown an RNAV (GPS) approach with vertical guidance and found that your autopilot failed to capture the glidepath?  Did the glidepath indicator remain hollow and fail to fill in and become solid magenta?  I’ve seen this often in everything from a Vision Jet down to smaller piston aircraft.

What I found is that people are flying ILS and RNAV approaches improperly.  But while they can almost always get away with doing it on an ILS, the same improper procedure often doesn’t work on an RNAV approach.

AIM 5-4-5b says in a note:  "The ILS glideslope is intended to be intercepted at the published glideslope intercept altitude."  But rather than descend at every stepdown, pilots often remain high and intercept the glideslope well above the glideslope intercept altitude.  That’s not the correct procedure, but it usually works when you fly an ILS, as the glideslope signal is constantly available throughout the entire approach.  But that’s not the case with an RNAV approach.

What I found is that the RNAV glidepath indicator doesn’t become solid magenta until the FAF becomes the active waypoint.  That occurs after you’ve flown by all of the other waypoints prior to the FAF.  So, for example, if you cross the IAF and remain at that altitude, later the glidepath indicator will most likely center before you’ve crossed the last waypoint prior to the FAF.  And it will remain hollow, and the autopilot won’t couple to it.

So the moral of the story is, fly all of the step downs of an approach.  When flying an RNAV (GPS) approach, if you don’t descend to the glidepath intercept altitude, you may find that your autopilot won’t couple to the glidepath.

[skykrawler]

The problem with intercepting a GlideSlope signal away from the intercept point is the signal integrity substantially beyond that range might not be good.  Also depending on the geometry there might be a 'false' glideslope.  That is one of the reasons to check the altitude at the charted intercept point.

There are plenty of RNAV approaches with vertical guidance charted with altitude AT OR ABOVE an altitude for the final approach course.  Its important to know if you are above the glidepath and not descending fast enough to intercept at the fix.

Different equipment displays differently.  Generally, Boeing equipment, with at least the flight director on will change loc/gs symbols to solid when it 'couples' to the signal and starts commanding to follow the loc/gs.    You could hand fly the raw loc/gs bugs (hollow) with the autopilot/flight director OFF.

The Pro Line 21 system doesn't fill the loc/gs bugs.   LNAV and GP bugs are star symbols.

The important thing is to know and understand is what your equipment will do.

[Max Clark]

I think the trick here is needed to perform a sequence on both the navigator and the autopilot.

The perspective+ in Cirrus need the approach loaded and active before pressing APR on the autopilot.

I originally had an IFD 540 with the KFC in my 2003 Ovation. When approaching the FAF the IFD would msg activate APR, except you had to soft key APR on the IFD before pressing APR on the KFC. Don’t ask me how long that took me and my CFI to figure out  

There was a note about bugging the minimum altitude before capturing the glideslope. Depending on the Garmin gear this is absolutely true. Similar to using VNAV, it won’t descend without having the target set. 

[Jerry 5TJ]

The KFC225 when used with a GTN750 (and IFD540) requires an extra step to capture the GS on an RNAV GPS coupled approach, as Max Clark described.  The extra step is annunciated on the GTN750 screen and requires a soft button press before engaging APR mode on the KFC225.  The procedure is detailed in the Garmin pilot reference manual for the GTN750.  
There is no mention of this requirement in the KFC225 manual or in the AFM supplement.  
 

[midlifeflyer]

On 1/3/2026 at 3:56 PM, Max Clark said:

I think the trick here is needed to perform a sequence on both the navigator and the autopilot.

The perspective+ in Cirrus need the approach loaded and active before pressing APR on the autopilot.

I originally had an IFD 540 with the KFC in my 2003 Ovation. When approaching the FAF the IFD would msg activate APR, except you had to soft key APR on the IFD before pressing APR on the KFC. Don’t ask me how long that took me and my CFI to figure out  

There was a note about bugging the minimum altitude before capturing the glideslope. Depending on the Garmin gear this is absolutely true. Similar to using VNAV, it won’t descend without having the target set. 

I'm still trying to figure out what was set up incorrectly. It would really help to know the approach and how things were set up.  Yes, you absolutely need the approach, not only active, but the FAF needs to be the active waypoint if you expect the autopilot to capture.

But I don't agree about setting a minimum altitude. I have not seen a Garmin that requires that to capture an ILS GS or RNAV GP.  That's strictly a VNV  requirement. The only time you need to set a bottom altitude is if you need to meet stepdowns before the FAF. 

 

My home base is an example. The entire approach until the FAF is at 2100'. So is the climb to the final missed approach altitude. So that's the selected altitude throughout the approach. Never changed. Always captures the GS/GP if everything is set and armed properly.