PC Control System Troubleshooting

[ltdoyle]

Instead of a rubber band to disconnect, try a plastic 35mm film canister.   It fits right over the yolk tip and holds the disconnect button down great.  When you want the system on, just take the film canister off and put it on the opposite yolk tip....

[N6843N]

I had an interesting conversation today with Brian Kendrick at Mooney. We got to talking about the PC system and I remembered this thread so I asked him how Mooney looked at the PC installation and he said it is part of the certification for the aircraft. So I asked him about it being inop, he replyed that it has to be operational for the aircraft to be airworthy, he went on to say if they get one in for an annual it has to be repaired to be returned to service. He also said the button is designed to be removed as a disabling feature incase of a falure. If you have an early model with the PC added after the plane was built the above would not hold true.

[HRM]

Quote: N6843N

I had an interesting conversation today with Brian Kendrick at Mooney. We got to talking about the PC system and I remembered this thread so I asked him how Mooney looked at the PC installation and he said it is part of the certification for the aircraft. So I asked him about it being inop, he replyed that it has to be operational for the aircraft to be airworthy, he went on to say if they get one in for an annual it has to be repaired to be returned to service. He also said the button is designed to be removed as a disabling feature incase of a falure. If you have an early model with the PC added after the plane was built the above would not hold true.

[aeromancfi]

Help! The PC  in my 65 E model worked fine until two years ago, then degraded. and finally quit. Inspection of the wing servos showed cracks in both rubbers.  Both servos replaced with Brittain units, New push-button O-rings installed, and overhauled trim valve ( Yoke mounted , sourced from Brittain). installed.  Mean-while had static system and transponder check performed for IFR to 20,000 ft.  PC system never worked again.  Maybe  static system guy unplugged, bent or pinched some vacuum valves?  Any good shops, or Gurus who know how to trouble-shoot these old systems??   Can't go IFR in this this bird unless the wing leveler is working. Location in Central CA     Thanks!!

 

aeromancfi

[JaredDavis]

Call Brittain: (918)836-7701

[N601RX]

There are 2 bulkhead pass through fittings the the pc hoses just slip over up close to the altimeter on the side of the plane.  They probably accidentally pulled one of the hoses off these.

[Hank]

Check the vacuum hoses behind the panel, mine were crumbly. Make sure the red & green tubes are in good shape and that no connections were pulled loose while checking static lines. They run from behind to panel to each wing servo, to both tail servos and to the controller in the top of the tailcone.

 

You already worked on the difficult-to-reach wing servos. Pull and inspect the tail servos; mine are inside the tailcone access door, and there is only one screw to remove per servo. If the boot isn't torn, the guys at Brittain can tell you how to rewrap them to eliminate leaks, quickly & inexpensively.

[aeromancfi]

Three good suggestions,that I will follow up on. I just had another thought. The pilot's yoke was removed  to comply with the inspection AD for cracks in the control tube. Maybe hose inside yoke is disconnected.. Got to check that too,  

 

Aeromancfi

[rbs4159]

Great thread. My '68 M20C had a beautifully functioning PC system in it when I bought it almost 7 years ago. A wonderful safety feature, which I leave engaged all the time except during landings/takeoffs and turns, when I simply press the release valve on the pilot yoke - I never pull the button up to relieve system vacuum. A couple of years ago, my A&P replaced an o-ring on the valve that was leaking, no big deal. This year, after looking for a long time, I finally obtained all the parts to add the Accuflite heading preselect and the Accuflite nav tracking systems which my A&P installed a couple of weeks ago during my annual. It is a terrific system, and everything works great except - - - my newly overhauled DG rolls out and tracks about 12 degrees left of the heading bug on all headings. My A&P has tested everything and Brittain has been very helpful, we now think the DG, which I bought ovhauled just last month is the problem. Does anyone know if the DG has a simple adjustment to align the lubber line and the bug? It tracks perfectly, but 12 degrees off. On another subject, a friend has an F model with the Brittain B6 system in it, but he has no documentation. Does anyone have the B6 manual that they could PDF and send me? I would be happy to pass along anything we learned during the Accuflite/Accutrak installation and testing if you want to email me. richard4159@att.net

[Hank]

Call Brittain. There is an adjustment screw on the Accu-Trak box in addition to the roll adjustment on the DG.

 

The L-R roll knob on Accu-Flite is very, very effective . . .

[rissacher]

So our mooney has PC and a Brittain B6. The airplane constantly wants to roll left, even with the knob turned to the right until the stop. Pushing or pulling the PC override button does nothing (still wants to roll left). I assume there's an air leak somewhere but I'm not sure why I can't turn the system off in the meantime.

Also, I assume the PC system has to be functional for the B6 to do its job?

[KSMooniac]

You could just have a plain old rigging problem with your flight controls, and not a problem with the PC system.  If it rolls left with the PC system off, then start checking the rigging with a shop that knows how to do this on Mooneys, using the book and the travel boards.

[rbs4159]

The PC system in my '68 C model works perfectly and I never disengage it. To make turns a bit easier, and on takeoff and landing, I depress the yoke button. When my son flies with me as co-pilot I just let him overpower it, which causes no damage, but keeps him from over-controlling, which he is inclined to do. I had both the Accuflite heading hold and Accutrak nav tracking systems installed last year, and they both work perfectly, as wel. The nav tracking system does wander some when chasing the CDI on a VOR, especially close to the station  - when that happens, I switch to the heading hold. The Accutrak will induce an almost perfect standard rate turn. I have located most of the components for the altitude hold, as well, and when I locate the panel for it (if anyone has parts for it, please let me know, I'm interested in buying them), I plan to have it installed. Brittain, has been incredibly helpful and their prices can't be beat. BTW, keep your fingers crossed that they're all all right, they're in Tulsa, OK, right in the path of yesterday's storm and tornadoes. I have PDF installation and maintenance manuals for these systems that I could attach to an email if anyone needs them, but they can be obtained directly from Brittain, too. 

[rissacher]

Its difficult to know whether the aircraft rolls left on its own, or whether the pc override button doesn't work.  There is no noticeable difference when I push the button so it leads me to believe that the button is broke.  I found a copy of the service manual and it appears that there are a few tests that my A&P can do to troubleshoot the system (leak check and gyro check) which looks like where we should start.  

 

I certainly wouldn't rule out rigging though.  Is there a way to disable the system other than the button to be sure how the aircraft flies on its own without the involvement of the pc system?

[JaredDavis]

What Hank said. Call Brittain.

 

Perhaps your system is not even on. What happens on the taxi test?

 

Near the end of my taxi run I turn a little right and watch the yoke go left.  Then turn a little left and watch the yoke go to the right. There is probably a better write up in the POH or Brittain manual. I do it near the end of the run to give the gyro time to spin up.

[N601RX]

When I 1st purchased my plane the pc system would not disconnect . The turn cordinator has 2 vac source lines going to it. One spins the turn cordinator, the other supplies the pc system. Someone had switched them in the past and pushing the button just allowed the turn cordinator to spool down. It would not disconnect the PC.

I also have an extra electric brittain disconnect valve if anyone wants to get rid of the pneumatic valve and switch and replace it with electric.

[yvesg]

When I 1st purchased my plane the pc system would not disconnect . The turn cordinator has 2 vac source lines going to it. One spins the turn cordinator, the other supplies the pc system. Someone had switched them in the past and pushing the button just allowed the turn cordinator to spool down. It would not disconnect the PC.

I also have an extra electric brittain disconnect valve if anyone wants to get rid of the pneumatic valve and switch and replace it with electric.

Does it replace the pneumatic switch on the yoke only?

Yves

[N601RX]

It re

Does it replace the pneumatic switch on the yoke only?

Yves

It replaces the pneumatic button in the yoke and valve behind the panel with a electric switch and valve.

[yvesg]

It re

It replaces the pneumatic button in the yoke and valve behind the panel with a electric switch and valve.

My pushbutton on the yoke is near the end of its life. I will PM you.

Thanks.

Yves

[hoot777]

Any suppliers out there for boots for the pc system???

[apriav]

For leak repair, fuel tank sealant will fix holes.

[carusoam]

1 hour ago, hoot777 said:

Any suppliers out there for boots for the pc system???

Not directly yet…

There are repair methods, used inventory, and sellers of similar products…

Best regards,

-a-