KFC 150 auto pilot troubleshooting

[Vref]

Looking for some expert advise on a KFC150.

The final phase off the major overhaul /rebuild is nearing his end on my M20J.

I was hoping that everything would be fine but unfortunatly the A/P is giving some troubles...The problem is that I am 700 Miles from the location where the repair is done. So I can only give some remote advise..I am neither an expert on BK auto pilot systems..;-(

So this is the status:

electric trim is working

auto pilot self test fails (engine was not running)...light stays on when self test finished (The Pilot manual states the self test should be done befor takeoff...) Engine running is not stated as a test condition..But I could imagine this is necessary to have a valid ATT/FD input to the KC192 as the KI256 is a vacuum system..?

I advised the mechanics over email to run up the engine to check:

1) If this has any impact on the test result

2) check if the Flight Director mode is working when the HSI in heading select is turned left and right...I that works my thinking is that at least the computation part is working OK...

3) If the FD is OK investigate rigging forces...?

Looking for some basic hands on troubleshooting guidance to at least isolate the issue..?

I assume the trim rigging can play role also..?

Input much appreciated

Luc

[carusoam]

Luc,

Things to check to make sure the self test works on the AP...

I have a BK KAP 150

There are a few buttons that can interfere with the initialization test.

(1) CWS - Control Wheel Stearing.  It is hard to tell, but if the button is activated, the initialization period never ends.

(2) AP emergency Off button.  This is more obvious than the others.

(3) Electric Trim. must be on for the test.

The engine is always on when this part of the Pre-flight comes up, but I don't know that it is required for the initialization test.

Good luck,

-a-

[Vref]

Quote: carusoam

Luc,

Things to check to make sure the self test works on the AP...

I have a BK KAP 150

There are a few buttons that can interfere with the initialization test.

(1) CWS - Control Wheel Stearing.  It is hard to tell, but if the button is activated, the initialization period never ends.

(2) AP emergency Off button.  This is more obvious than the others.

(3) Electric Trim. must be on for the test.

The engine is always on when this part of the Pre-flight comes up, but I don't know that it is required for the initialization test.

Good luck,

-a-

[kortopates]

Luc,

The engine need not be running providing you have electric standby vacuum for the gyros. Per your AFMS for the KFC150 that should be in the supplement portion of your POH, Section IV - Normal Procedures, (pg 22) Preflight test Step I is "GYROS - - Allow 3 to 4 minutes for gyros to come up to speed ....."  the A/P won't be able to pass its preflight test without the gyro's working.

If you don't have it or don't have access to it while its in the shop, you can download a copy of the King 150 series  AFMS for the J & K Mooney  models from the Mooney factory website - or PM me and I'll send up a copy.

[Wistarmo]

The autopilot disconnect switch on the yoke ususally does two things:  1) It disconnects the autopilot, and 2) It disengages the electric trim.  If this switch is defective, the autopilot will not pass the self-test.  This has happened to me.  The switch is an easy and cheap thing to replace if it is the culprit. 

[Vref]

Very good feedback so far thanks all, So I don't have a electric gyro's its only a KI256 which is vacuum. This would mean the engine needs to be running to pass the test......

Maybe the KC192 needs a valid flag signal (gyro spinning) from the ATT ..?.......

YEPPP...just read the German Flight Manual (Tranlated from english in 1985)

VORFLUG KONTROLLE (befor each flight)

Die Kreiselinstrumente benotigen ca 3 -4 minuten um aufzurichten..

(The Gyros need 3 to 4 minutes for erection)

then the description as in the english Pilot Mnaual...YESSS.....sounds logic...

....Kortopates I will check the mooney site also tnx for the hint and the input!!

 

Anyway on the big jets the full A/P test is a tricky job you need to fool the aircraft systems and let them think they are in flight mode...;-)..

[jetdriven]

I have an old Century IIB and it works great mostly, but the first thing is to get a maintenance or service manual for the KAP 150.  I now owners can only do lmited maintenance but education is cheap and when you find out a list of likely solutions take those to your A&P. 

[kbrad622]

Hi, I read your comments and I have a KFC150 in my Mirage and had a self test failure. It was the pitch servo located in the rear of the plane. My plane has three servos. Hope this helps, cost about $1500 to overhaul.

[Vref]

Quote: kbrad622

Hi, I read your comments and I have a KFC150 in my Mirage and had a self test failure. It was the pitch servo located in the rear of the plane. My plane has three servos. Hope this helps, cost about $1500 to overhaul.

[tyrefoote]

I'm having an issue with my KFC 150 also, In the heading mode it seems to track the far left side of the heading bug.  Does anyone know if this is normal or is something else wrong ?  It works fine and the self test seems to indicate it's ok.    

[LFOD]

Quote: tyrefoote

I'm having an issue with my KFC 150 also, In the heading mode it seems to track the far left side of the heading bug.  Does anyone know if this is normal or is something else wrong ?  It works fine and the self test seems to indicate it's ok.    

[Vref]

Quote: LFOD

Wish I could help, but I can only commiserate.  Mine is doing the exact same thing. 

[LFOD]

I have absolutely no idea what any of that means. 

[Vref]

Quote: LFOD

I have absolutely no idea what any of that means. 

[BorealOne]

Grr...i'm getting a 'HDG' flag now about 50% of the time. I'm taking this as a sign from the gods that the KG102A gyro in the tail is going down. You don't know how much you rely on the autopilot, esp in IFR flight, until it becomes a glorified wing-leveller.  

[Vref]

Update on my KFC150 A/P troubleshooting:

What I have found out so far (maybe useful for anyone having a KFC150 installation):

I checked out my vacuum system for leaks: Even if the gyro seems to work having a leak may impact the attitude valid signal to the A/P. Honestly I am surprised the KI256 does not give a warning flag if there is a problem..? This could have been easely implemented by checking the Gyro rotor speed...?.. A real safety concern I think specially if you only have no back up ATT indicator for cross checking...

I had two months ago a small air leak (tube between the firewall and indicator was not OK) though the KI256 was working normally the A/P self test failed. We found this out while we heard a light hissing sound...

After solving this issue the KFC150 passed the on ground f test before take-off.

Now I was able to engage the A/P in ATT hold mode after checking the Flight Director mode first

However my HSI still has a problem with the slaving, I initially thought it was fluxvalve problem but after some intensive troubleshooting it was clear the indicator has a problem ( I assume the synchro heading resolver is screwed up inside the indicator). The KFC150 will not work in heading mode when your HSI is in free gyro mode.....

 

So lessons learned so far (maybe obvious for someone having experience with the KFC150 but for me its new). I found out also that the KFC150 operational manual does not explain diffrent failure mode well...:

I will install a small suction indicator in my bird to show any tendency there might be a degradation of the vacuum system. This not only impacting your ATT but also A/P functionality (KFC150). I was surprised that though my bird is very well equiped this feature was not installed over the lifespan of the aircraft so far..? The M20J annunciator LOW VAC light I don't thrust..)

KI525A (KCS55A) with a not working slave mode will impact your A/P roll steering (this is rather dubiously mentioned in the KFC150 operational manual)...

I am seriously thinking of dumping my Turn coordinator and install a backup electrical ATT indicator. I am VFR only but when I am instrumented rated I wouldn't fly without a back up ATT in IMC....just from technical redundancy perspective that is....

A lot of people in the US are dumping there KI525A's for glass so you can do very good deals ($ versus euro). I bought a second hand KI525A with a very hi serial number 90000+ P/N 3046-07 all the later KI525A have all the bootstrap mod which is required to run your HDG on a Storm-scope or RMI indicator if you have one and the -07 runs on both 30/400Hz .....

Luc

 

[jetdriven]

thats a great idea I'm going to do that soon.  a T/C mistakes yaw for bank.   KI-2525A are still hellishly expensive used.  People here want 3K for a used system.

Quote: Vref

I am seriously thinking of dumping my Turn coordinator and install a backup electrical ATT indicator. I am VFR only but when I am instrumented rated I wouldn't fly without a back up ATT in IMC....just from technical redundancy perspective that is....

A lot of people in the US are dumping there KI525A's for glass so you can do very good deals ($ versus euro). I bought a second hand KI525A with a very hi serial number 90000+ P/N 3046-07 all the later KI525A have all the bootstrap mod which is required to run your HDG on a Storm-scope or RMI indicator if you have one and the -07 runs on both 30/400Hz .....

Luc

 

[TLSDriver]

I have had mine go down twice.   First time it was the ap disconnecrt switch.  Cost me $20.  Second time it was my pitch servo. It was intermittent at first but finally died.  That one cost me $750. (Another shop wanted $1,500.)

Other note is the comment about doing the self test on the ground.  I can tell you that the self test works just fine in the air. I think they want you doing it on the ground becuase you don't want to get airborne and find out it won't come on-line.

When my pitch servo started acting up my a\p would fail on the ground.  Once I was airborne I would do it again and it would pass.  After an hour or so the a\p would quit.  I would do another self-test cycle.  75% of the time it would pass and I would re-start the a\p.  I did this nonsense for about 30 hours before the servo finaly died completely.

Good luck!

[Vref]

Quote: jetdriven

 

[Vref]

Quote: TLSDriver

I have had mine go down twice.   First time it was the ap disconnecrt switch.  Cost me $20.  Second time it was my pitch servo. It was intermittent at first but finally died.  That one cost me $750. (Another shop wanted $1,500.)

Other note is the comment about doing the self test on the ground.  I can tell you that the self test works just fine in the air. I think they want you doing it on the ground becuase you don't want to get airborne and find out it won't come on-line.

When my pitch servo started acting up my a\p would fail on the ground.  Once I was airborne I would do it again and it would pass.  After an hour or so the a\p would quit.  I would do another self-test cycle.  75% of the time it would pass and I would re-start the a\p.  I did this nonsense for about 30 hours before the servo finaly died completely.

Good luck!