KFC 150 Problems

[Releew]

I am recently getting intermittent TRIM failures when initializing the KFC 150 AP test.  Reading the book it refers to an internal test is done on the servos and if the system passes the trim indication light will blink 4 times and you will receive an audible tone 6 times along with 12 blinks from the AP indicator.  Well lately its hit or miss......  One thing for sure...  if you fail to do this check before taxi you cannot get this system to engage until the aircraft is on the ground and completely stationary with control surfaces neutral.....  I have tried pulling the fuse, turning off the trim switch... to reset, everything I could assume could be done......  What am I missing?

Now... when it does work, its SOLID as a rock!  

Is this correct or does it sound like there is something wrong or going in that direction?

Thanks for your input.  Well appreciated!

Rick

 

[carusoam]

Often, the trim switch on the yoke is a culprit for the BK AP challenges...

The tones and blinks are related to each test. A missing tone indicates what part of the system it thinks is missing.  The manual has a list of tests and what order they are in.

Can you detect which beep is missing when you count along with the beeps?

Mine is a KAP 150. When the trim circuit breaker switch is turned off I get the missing tone when the AP fails...

The all CBs/switches off line in the checklist gets a little old after awhile...

Am I close?

Best regards,

-a-

[carqwik]

Yoke trim switch.  Use quick dry electrical contact cleaner on it (unscrew it from the yoke, pull it out slightly, spray all of it...). 

I didn't know the beeps and lights related to individual system/circuit tests...30+ years with King A/Ps and never knew this...thanks!

[Releew]

I get 4 flashes on the trim light, FD bar stays up on the AI, 6 beeps on the audible annunciation and the AP light on the AP blinks... when all is OK.  On a failure, the FD bar on the AI drops out and all lights on the AP go off.  If the trim rocker switch is off, I get a continuous pulsing audible annunciation.

If I move this aircraft before conducting the test..... get ready to hand fly!  I've tried resetting the trim rocker switch and the breaker with ZERO success.  Just made a big label !!!!!! TRIM TEST BEFORE TAXI.....  I know if the aircraft is stationary, it test OK the first time.  I'm just trying to understand why.  All the books says is contact a service center if the trim test fails.......

The previous owner told me it did this to him as well.  I've got some AP experience with STEC but none with the KFC 150.  Looking for Normal or Not.....

Thanks!

Rick

 

 

[kortopates]

First paragraph is normal, and because of the need to for the AP to have the trim switch on and ensuing beeps at startup, I always leave my Trim switch on - the only switch I do not turn off at shutdown.

Regarding the second paragraph, you should be able to reset the AP by pushing the Test button on the computer anytime. Especially after a disconnect of some kind. You should not need to do the trim test before taxi - something is wrong. It could fail from the Yoke trim switch, Trim servo, pitch-trim servo or the computer. An auto-pilot specialist is best for troubleshooting it.

[Releew]

Thanks!  Call Autopilot Central tomorrow....

[Tony Armour]

There is a very similar post in the avionics forum under "autopilot" 

Might check it out. Here is what I posted: 

Before doing your test, just barely/gently try to move the trim wheel. If it doesn't move easily like it should don't move it and see if it fails the test. If it fails, then move the trim wheel manually and try the test again. I forget everything about how it works but there is a part that works via magnet and sometimes the arm doesn't let go. A possible fix may be as simple as a piece of electrical tape to calm down the magnetic part. That's the best way I can explain it but if that test works the same for you, I can find out more. Mine gave fits for a few flights and I figured out the trim wheel work/not work deal. When the trim wheel was "stuck" I would manually move it and the autopilot would test fine. We never did the tape because it just quit...not working :-) and has been fine since. 

[Releew]

For those interested.....  I did more digging and with the help of AutoPilot Central got a schematic on the system and some great troubleshooting advice.  Below is the sequence of operational checks without the need to remove the unit.

• Trim rocker on.  If yes, advance if no, continuous alarm (obvious....)
• Trim light KFC 150 solid on
• Depress trim test button
• Trim light blinks 4 times.  Each pulse represents a "TO PULSE" and "RETURN PULSE" to the A/P computer.  Place you hand on the trim servo to verify the pulses.
• If pass, Check.....
• CWS... Open contact
• Trim Up...Open contact
• Trim Down...Open contact
• A/P disconnect.  Checks for 28VDC back to the A/P computer.  N/C switch.
• Also checks the Gyro for centering.  Was told it could not be greater than 20 degrees off center. Can't do this visually but you should verify its spinning.

If all good above there should be a audible tone of 5 beeps indicating system passed. It was suggested I remove the top hat on the yoke and clean the switch contacts with a high grade electronic spray.  I did this and so far all has worked well...on the ground.  Will try in flight this week...

Rick

 

[carusoam]

Thanks for sharing your detailed research, Rick.

Good luck on the test flight.

Best regards,

-a-

 

[flyboy0681]

I flew yesterday and pressing of the TEST button on the KAP 150 during my run-up resulted in nothing happening, even though the TRIM button was illuminated (that is, the unit was powered up). After doing this for a minute I pulled and reset the breaker and low and behold the unit tested fine. Upon my return flight the same scenario. Any ideas?

[Bravoman]

One question on the kfc 150: a couple of days  ago I was shooting the ILS at PDK and the glide slope wouldn't couple/capture. I was as the right altitude and the localizer coupled perfectly. Was vectors to final. On the S tec 60-2 I use in another aircraft pressing alt will cause GS capture and the GS light to come if it doesn't do so automatically for some reason and as long as you are at the right altitude etc. Pressing alt doesn't seem to do that with the 150. I was in Alt, HDG and then Approach mode. Usually works fine and I disconnected and hand flew but what am I missing?

 

thanks, Frank

[Marauder]

One question on the kfc 150: a couple of days  ago I was shooting the ILS at PDK and the glide slope wouldn't couple/capture. I was as the right altitude and the localizer coupled perfectly. Was vectors to final. On the S tec 60-2 I use in another aircraft pressing alt will cause GS capture and the GS light to come if it doesn't do so automatically for some reason and as long as you are at the right altitude etc. Pressing alt doesn't seem to do that with the 150. I was in Alt, HDG and then Approach mode. Usually works fine and I disconnected and hand flew but what am I missing?

 

thanks, Frank

Frank -- on my 60-2, the only way it will capture a GS would if I have the AP in HDG & ALT mode prior to the FAF and then within the acceptable intercept position hit the NAV mode. This puts the STEC into GS intercept mode (if there is a GS). The 150 looks like you need to hit the APR button. Could that be what is going on?

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[carusoam]

3 hours ago, Bravoman said:

 

BK is pretty good about posting their manuals on line.

As Marauder points out there is a combination of buttons to be pressed depending on your situation.

A few important details are...

- Above or below the glide slope for the intercept.

- How far out on the procedure you are.

- Being in approach mode allows for different other things to happen.

- Angle of intercept details may be important as well

So many details, it's good to have a chart for the list of memory items...

http://www.bendixking.com/Downloads/Documents

Best regard,

-a-

 

[Bravoman]

Yes I activated APR mode from FD ALT and HDG modes. And I turned my heading bug on the Aspen to the approach course. I am positive I did everything right but the GS light did not illuminate and no glide slope capture. I don't know why and unlike the S tec I don't know how to initiate a manual capture for lack of a better way of putting it.

[Marauder]

Yes I activated APR mode from FD ALT and HDG modes. And I turned my heading bug on the Aspen to the approach course. I am positive I did everything right but the GS light did not illuminate and no glide slope capture. I don't know why and unlike the S tec I don't know how to initiate a manual capture for lack of a better way of putting it.

On the STEC 60-2, pushing the HDG and NAV together forces the system into a manual intercept mode. I have a video on my YouTube channel that shows how an 80° intercept is handled by the STEC.

The BK unit may have different requirements for the proper intercept required for GS activation than what you are used to seeing on the STEC. Have you tried activating while straight in on the localizer, below the GS and within 2 miles of the FAF? I would try to rule out all of the variables with a straight-in approach before trying to see if the intercept is the problem.

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[Marauder]

Frank - I just re-read your first post. It sounds like manually flying it works. I would look at the BK manual for very specific limitations on where it will intercept. It sounds like a parameter is not being met.

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[PTK]

1 hour ago, Bravoman said:

Yes I activated APR mode from FD ALT and HDG modes. And I turned my heading bug on the Aspen to the approach course. I am positive I did everything right but the GS light did not illuminate and no glide slope capture. I don't know why and unlike the S tec I don't know how to initiate a manual capture for lack of a better way of putting it.

Bravoman, please elaborate and clarify what you mean on what I highlighted above.

The way it should work with VTF activated on the navigator is as follows: With APR  "armed" outside the final approach course it flashes.  ALT, FD and HDG are lit solid and HDG bug is available. Once it captures localizer APR "activates" and remains lit solid and HDG bug is not available to you. ALT remains lit until GS capture when GS lights up and ALT goes out. The KFC 150 will capture GS from both above and below.

[Bravoman]

Peter, I pressed the APR button just as I was intercepting the final approach course using the heading bug. I was more than 2 miles from the FAF(to Marauder's comment) and the APR light went immediately solid since I was only a degree or so from the localizer course when I pressed APR.  As I said, it tracked the localizer perfectly but the GS light never came on and there was no GS capture. Proper altitude for capture is 2900 ft and I had that pegged.

 

i will go out and fly some approaches to see if I have a glitch but was also wondering if there is some way to "force" GS capture as there is on the S tec?

 

thanks for the help guys. Regards, Frank

 

 

[carqwik]

I've seen the exact same problem with my KFC-150....set up perfectly but stays in ALT mode and flies right through the GS intercept.  Last time I saw this was on the ILS 16R into VNY....

Two thoughts...first, I think (not sure of this however) that the KFC-150 won't capture if you set APR at a point where you're above the GS and have ALT mode engaged. You have to engage the APR mode below the GS and fly into the GS.  Second, (and I've done this too), in my plane you have to manually switch from GPS to NAV.  If it stays in GPS mode, then you'll see the localizer center (but it's actually the GPS derived course) appear and no GS in the HSI.  So the plane just tracks course and altitude.

[Bravoman]

1 hour ago, carqwik said:

I've seen the exact same problem with my KFC-150....set up perfectly but stays in ALT mode and flies right through the GS intercept.  Last time I saw this was on the ILS 16R into VNY....

Two thoughts...first, I think (not sure of this however) that the KFC-150 won't capture if you set APR at a point where you're above the GS and have ALT mode engaged. You have to engage the APR mode below the GS and fly into the GS.  Second, (and I've done this too), in my plane you have to manually switch from GPS to NAV.  If it stays in GPS mode, then you'll see the localizer center (but it's actually the GPS derived course) appear and no GS in the HSI.  So the plane just tracks course and altitude.

The second of your points was not my issue because my navigator is the GTN 650 and I was definitely in VLOC mode. As to your first point I will experiment with that and report back. Can't imagine that being the way it is designed though since it doesn't seem logical that it wouldn't be set up to capture at the published GS capture altitude. I'll look back at the manual too. 

 

Thanks again, Frank

[flyboy0681]

Here is what the manual says about the GS after the APR button is pressed:

 

7. Once localizer course capture has
occurred on an ILS approach, the
glideslope mode is armed. Automatic
capture occurs as the aircraft
approaches the glideslope from either
above or below. When the intercept
occurs, "GS' is illuminated on the
annunciator panel. The autopilot will
maintain the glideslope with pitch corrections.
If altitude hold (ALT) mode
had been engaged prior to GS capture,
it will disengage at capture and
the ALT light will go out.

 

 

[Marauder]

1 hour ago, carqwik said: I've seen the exact same problem with my KFC-150....set up perfectly but stays in ALT mode and flies right through the GS intercept.  Last time I saw this was on the ILS 16R into VNY....

Two thoughts...first, I think (not sure of this however) that the KFC-150 won't capture if you set APR at a point where you're above the GS and have ALT mode engaged. You have to engage the APR mode below the GS and fly into the GS.  Second, (and I've done this too), in my plane you have to manually switch from GPS to NAV.  If it stays in GPS mode, then you'll see the localizer center (but it's actually the GPS derived course) appear and no GS in the HSI.  So the plane just tracks course and altitude.

The second of your points was not my issue because my navigator is the GTN 650 and I was definitely in VLOC mode. As to your first point I will experiment with that and report back. Can't imagine that being the way it is designed though since it doesn't seem logical that it wouldn't be set up to capture at the published GS capture altitude. I'll look back at the manual too. 

 

Thanks again, Frank

Based on what flyboy just posted, it looks like the 150 will intercept from above.

I think you mentioned you have an Aspen. Is the Aspen set to GPSS mode while this is going on? The reason I ask, I am wondering if you are doing the transition from a GPS driven feeder to the final approach course and leaving the GPSS on is doing something weird.

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[Bravoman]

4 minutes ago, flyboy0681 said:

Here is what the manual says about the GS after the APR button is pressed:

 

7. Once localizer course capture has
occurred on an ILS approach, the
glideslope mode is armed. Automatic
capture occurs as the aircraft
approaches the glideslope from either
above or below. When the intercept
occurs, "GS' is illuminated on the
annunciator panel. The autopilot will
maintain the glideslope with pitch corrections.
If altitude hold (ALT) mode
had been engaged prior to GS capture,
it will disengage at capture and
the ALT light will go out.

 

 

Thanks, that's what I always do. Works same way for GPS(RNAV) approaches and usually works fine for me. Was a bit disconcerting that I didn't have capture in IMC although it certainly wasn't the end of the world. I will thoroughly troubleshoot to make sure I don't have a system problem. Thanks for looking that up! 

 

Frank

[Bravoman]

8 minutes ago, Marauder said:

Based on what flyboy just posted, it looks like the 150 will intercept from above.

I think you mentioned you have an Aspen. Is the Aspen set to GPSS mode while this is going on? The reason I ask, I am wondering if you are doing the transition from a GPS driven feeder to the final approach course and leaving the GPSS on is doing something weird.

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No I definitely had the Aspen in heading mode since I was on vectors and had been using the heading bug on the Aspen for a good while before being cleared for the approach and twisting the bug to the final approach course.

[carqwik]

Hmm...perhaps it was operator error a few times on my part where I put it in heading/nav mode instead of heading/approach...that would explain why it didn't capture the GS.