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A/P Approach mode


flyboy0681

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I went up with my CFI today to practice some approaches. For the second LPv approach I had the KAP 150 fly it by engaging the APR mode once I arrived over the FAF. The localizer and GS were nailed when I pressed the APR button but the unit didn't capture the GS and the light did not illuminate, although it flew the localizer perfectly. I did the same thing on the final approach of the day at my home drone and still no GS capture.

As some of you know, we had the unit repaired recently by AP Central for replacement of a capacitor. Once the repair was completed they reported that the unit was checked and it passed all of the factory benchmarks.

Before I send the unit out, any ideas what I should look at? The unit is coupled to a 525A HSI, which is fed by the GTN 750.

 

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I believe the KAP 150 autopilot will not capture the GS from above or if there is not a minimum amount of time prior to capture (30 seconds?) I don't remember the time.

If you are using a Garmin GPS did you establish the inbound course with the autopilot NAV,  APR and ALT selected ? The airplane should be at the approach altitude IAF and fly into the GS from below, usually around the FAF. The GS indicator will light up on its own.

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Just now, Cruiser said:

I believe the KAP 150 autopilot will not capture the GS from above or if there is not a minimum amount of time prior to capture (30 seconds?) I don't remember the time.

If you are using a Garmin GPS did you establish the inbound course with the autopilot NAV,  APR and ALT selected ? The airplane should be at the approach altitude IAF and fly into the GS from below, usually around the FAF. The GS indicator will light up on its own.

NAV, APR and ALT were all engaged at the time and the inbound course was set.

Last year there was a thread here on whether the KAP needs to be above, below or at the intercept altitude and I reported that my unit captured it from above and at intercept altitude, while others said theirs engaged below, which led us to all believe that within a certain tolerance it can be accomplished by all three.

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What is the button-ology required by the KAP 150 to capture the glide slope..?

All stuff that made sense a couple of years ago.... it's been that long since I have used it...

Alt button on or alt button off? Before intercept with the glideslope...

Did you see the glideslope appear on the HSI?

there is a page or two in the KAP User manual for all the various fly a heading, intercept a radial, switch to an ILS and intercept the GS. Kind of thing.

heading mode, nav mode, approach mode (tighter tolerance), intercepts, etc...

Any help? 

Running the sym for MSFS should verify if the logic you are using for the AP is correct...

I believe, The KAP150 is capable of capturing from above... the warning that goes with it is there can be some false signals that can be mis guiding if captured inappropriately.... plus there is he added challenge of going Dow, slowing down, now capture a GS before running out of room.... :)

Things in my crowded head, not a CFI....

Best regards,

-a-

 

 

Edited by carusoam
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Just now, carusoam said:

What is the button-ology required by the KAP 150 to capture the glide slope..?

All stuff that made sense a couple of years ago.... it's been that long since I have used it...

 

 

Alt button on or alt button off? Before intercept with the glideslope... ALT button was on since the IAF

Did you see the glideslope appear on the HSI? Yes, like I said, it was perfectly centered when I arrived at the FAF.

Something is not adding up. I've been using the KAP 150 for decades and have successfully had it fly approaches dozens of times.

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I did some reading as well...

page 43 of the KAP manual covers the details....

The KAP100 is also mixed in as are the different VOR and HSI displays.

Make sure you find the paragraphs that cover your equipment.  The KAP150 with the 525 HSI can intercept above or below.  In APR mode, When it is outside a limitation, it will arm the system while maneuvering and intercepting.  When it is within a tight limitation as you were flying, it should track the ILS laterally, and then intercept and track the GS vertically... while tracking, flashing lights means it isn't on course yet.

The KFC is in there too...

Let me know if you need details of the manual I was reading.  I had downloaded it direct from BK.

You may have confused its 90’s era computer by putting it directly on course and on altitude... (this is possible but unlikely, the manual is written in a limited way to be more user friendly, less deep techie mooniac friendly)

The description is all of about ten sentences long, 9 sentences longer than my memory for writing....

Best regards,

-a-

Edited by carusoam
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4 minutes ago, carusoam said:

Make sure you find the paragraphs that cover your equipment.  The KAP150 with the 525 HSI can intercept above or below.  In APCH mode, When it is outside a limitation, it will arm the system while maneuvering and intercepting.  When it is within a tight limitation as you were flying, it should track the ILS laterally, and then intercept and track the GS vertically... while tracking, flashing lights means it isn't on course yet.

 

Now this is bothering me. I was within the "tight limitation", and it did not flash - as expected. However, it did not capture the GS.

I'm heading out on a trip next week and will be sure to press the APR button prior to reaching the FAF just to see what happens.

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Some additional small details...

There is

- APR Arm mode, This is when you are outside that small range.

- APR mode, This skips the arm mode and goes direct to the approach.

- the Alt light goes out when the AP intercepts the GS.  A piece of information that is kinda too late to make useful, sort of...

The last note in the section of the manual is related to things that are not GS capable, like a VOR or RNAV.  I think this might be capable of giving you a hassle.  Do the recent changes to your AP cause it to not properly recognize the source of data?

If it was thinking VOR or non-WAAS approach, it may have locked out the ability to intercept the GS....  this might be more GTN than KAP150.

I hope these ideas scratch the part of the brain that lights an internal idea light bulb.   :)

I needed the review of both the KLN90B and the KAP 150, so that worked for me.  Thanks for letting me play along.

Best regards,

-a-

 

 

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Just now, carusoam said:

If it was thinking VOR or non-WAAS approach, it may have locked out the ability to intercept the GS....  this might be more GTN than KAP150.

 

The last time I used the AP to fly an approach, which was last September, it all worked just fine. No changes occurred with the GTN in that time, but like I said, the AP was repaired when a capacitor exploded.

I appreciate your input.

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The KAP manual was written before WAAS and GPSS became widely available. 

All vertical guidance is written as if it were being supplied by an ILS.

the last details I got from the KAP manual were...

- if you were using ALT mode to hold altitude the alt light goes out upon interception with the GS.

- the GS indicator light is turned on, on an annuciator somewhere?  (Now I have to look up where my GS annunciator could be)

90s technology used to be so advanced....

Best regards,

-a-

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I appreciate this thread... As I continue learning about my airplane's features in preparation for my IFR rating, this subject is most helpful. I just spoke with my CFI about showing me how to start practicing IFR approaches by hand, so I can learn specifically how to operate and practice using my avionics suite that includes the KAP-150 and its approach capabilities. Now that my 150 has been repaired, I'm most interested in testing its other features like APR mode... Maybe when I have it down, I'll post a video of the whole approach process with a KAP-150 coupled to the KI-525A that's being driven by a GTN-650...

Best,

Jon

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17 minutes ago, carusoam said:

Jon,

have you got a copy of the KAP manual from BK?

It's available online and can be downloaded to your iPad...

Getting a feeling for the all of the capabilities of the GTN approaches and their naming standards takes a bit of memory power.

Best regards,

-a-

I have not downloaded it yet... I have the supplement copy to my POH, which I have read but didn't really process the information, as the AP was inop. Now that it's operational, I've got to learn its features. Do you have a download link, that will speed up my search process to get an electronic copy?

Thanks Much!

Jon

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BK has a manual section that is all downloadable...

I'll see if I can send a link....

First thing that came into my head was the KLN90B manual...   https://www.bendixking.com/HWL/media/Pilot-Guides/006-08773-0000_1.pdf

The one you want....  KAP manual....

https://www.bendixking.com/HWL/media/Pilot-Guides/006-08377-0001_1.pdf

The KAP one is a fun read.  Select the hardware you have and the reading is pretty short.

flying with all the hardware actually working is pretty easy.  Since training for the IR, the CFII fails all the hardware one piece at a time, randomly, until you have nothing left but a power knob, TC, a rudder, a compass, a clock, and one nav com.  :)

Fun stuff. In real life, the digital stuff hardly ever breaks down.  In CFII life, the gps seems to be the first to go on the fritz!  :)

-a-

Edited by carusoam
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8 minutes ago, carusoam said:

BK has a manual section that is all downloadable...

I'll see if I can send a link....

First thing that came into my head...   https://www.bendixking.com/HWL/media/Pilot-Guides/006-08773-0000_1.pdf

stand by...

-a-

Thanks but that is for operating a KLN 90B and the guide doesn't discuss operating with an interfacing autopilot based upon my cursory review. I tried shortening the URL in the hopes of hitting BK's download library--jackpot--but was unsuccessful. Don't search too hard... I have an electronic copy of my POH and its supplements complements of technology, so I'm sure I have it already...

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Jon,

check again...

see where the note used to say Stand by...?

sorry for the delay.  I'm trying to get my KLN90B to cooperate with my KAP150.  And get it all on my iPad instead of printed binders in my office...

i am way older than I want to be...

the next step is to get a GPSS unit to fit between the two devices...

Best regards,

-a-

 

Edited by carusoam
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2 hours ago, flyboy0681 said:

Looking at the manual, it appears that it only captures the GS from above or below, but not at - which is where I was both times today.

Now for a stupid question: why? Why won't it capture it if I'm right on the glideslope when arming it?

 

 

KAP150.jpg

Why? Because it needs time to calculate the intercept.  It's a rather dated piece of analog technology.

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No worries!!! I have researched GPSS units in depth, specifically the ICARUS SAM unit and the GDC 31 unit and their capabilities. The GDC was on my short list but I'm wondering if I even need it. My KAP-150 flies the NAV function based upon my 650 input to the KI-525A like its on rails... I understand that it smooths transitions out from waypoint to waypoint but there is a cost associated with installing the GPSS and I've yet experience a jolt in the AP transitioning from one WP to the next... perhaps they are very helpful when preparing for approach mode. Keep in mind that I am very much an infant with autopilot technology, so I have a bunch of trial and error in front of me with my current equipment before I start spending major bucks on upgrades... Thanks again for spending the time and effort to put things together for me. I sure appreciate your effort!

Regards, 

Jon

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This sounds like a config prob between the gtn 750 and kap150.Both kap 150 and 225 have no way to tell if Rnav Lpv appr is enabled...the gtn 750 should be set to manual prompt "enable a/p output"..so that with RNav LPV approachs the gtn 750 after determining rais ,should message "enable ap guidance?"...typically,you start approach in heading mode if being vectored..or nav mode if own nav to IF.Either way ,altitude is manual per appr plate..somewhere between IF and FAF...the gtn 750 /530w/avadyne 540 etc should message ,and at that time ,once ap output is enabled ..than you hit appr mode on KFC 150 to couple approach.

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Jon,

There are two things that are a bit of a pain in actual IFR flight... really busy times and really slow times...

1) really slow: you sit for long periods of time between any activities... way points suddenly become easy to miss.  Staying on the centerline with nineties technology requires hitting a button within seconds of it blinking.  In daylight, a blinking light is pretty easy to miss while you spend 99% of the time looking for other airplanes.... solution: GPSS.

2) really busy: on climb out, you get cleared to something like 6k'. You get pointed in the right direction, gear stowed, flaps away and your climbing through 3,000' doing checklists. a minute and a half later (at O3 Climb rates) it is time to level off.  Miss that altitude cue by six seconds and you have busted your altitude assignment and keep climbing... solution: altitude alert...

These are two targets that I have found to be a challenge.  There are a number of different hardware and software solutions.  Just being aware of the challenge is a good way to start.  

They are part of the bigger challenges of the human brain during different levels of multi-tasking. Sense of timing, paying attention  to things that need to be done right now and not forgetting the things that need to be done in a couple of minutes.

Get to know where your limits are...

Thanks for sharing your thoughts,

-a-

 

Edited by carusoam
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I have a KFC 150 and got tired of all the GS capture confusion.  I called Autopilots Central and asked them.  What nice folks.  They had a KFC 150 on the test bench and said they would test it for me.  The result was that it captured the glideslope from above or below just as the manual states.

Before the flames start, I too have failed to capture in both directions.  After more research I solved the mystery.  The KFC captures by detecting the zero crossing as you pass THROUGH the glideslope.  In a normal capture from below this is hardly ever a problem.  The glideslope needle comes down, goes a tiny bit below center, capture occurs, and it flys the glideslope.

A capture from above works similarly.  The problem however is the pilot not the KFC.  I, and a lot of others, do not want to fly through the glideslope from above.  Hence we either level off above or right on the glideslope.  In this case The KFC will never capture as there has not been a zero crossing.  Fly through the glideslope from above though and it captures every single time.

If you are having a really good day you can fly to and exactly on the glideslope from above or below and it will not capture.  Once again the explanation is the same, you must fly THROUGH the glideslope, though only by a needlewidth or so, for capture to occur.

Since discovering the above I have had failures to capture but none that I could not explain.

 

 

 

 

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