Replacing the Bellows in my '66 M20E to fix the PC

[Dcflyn]

The PC doesn't work. We've checked the vacuum which is ok. Has anyone replaced the bellows? How difficult is the job? Do the interior side panels need to come off?

Thanks...

[Ron McBride]

You're servos are in the wings and tail, you may also have a servo on your step.   Servos are available at Britton and Lasar, and probably others.

Ron

[Yetti]

Call Brittian.  They can rebuild or exchange or such.   Also the tubing in the wing (port side more than starboard) needs replacing every now and then. About 2AMU if Brittian goes through the system and fixes everything. 

Edited August 9, 2016 by Yetti

[Hank]

The rudder servos are in the tailcone, easily accessible through the avionics panel behind the wing. Aileron servos are behind the inspection panel at the inboard end of each aileron; patience and small hands help with their removal and replacement.

I replaced all of the old, cracked screw fittings in my PC tubing several years ago, it really helped.

[carusoam]

1) hoses age and crack.

2) rubber pieces age and leak.

3) Brittain still services this stuff.

http://www.brittainautopilots.com/products-services.html

My 65C's wing leveler never got the love it deserved.  I learned all this from MS people...

 

Best regards,

-a-

 

[geoffb]

When you say doesn't work, could you be more specific?  If it doesn't work at all, I wouldn't think it's a servo issue since even the basic PC has 4 servos.  Might be more likely something in the pilot valve part of the system.  When I bought my plane, the PC wouldn't disengage.  Ended up being the hose from the disconnect valve being pinched.  PC troubleshooting is in the Mooney service manual and I think also available on the Brittain site.

[N201MKTurbo]

How to test the servos:

take the rubber hoses off the back of the turn coordinator. Stick each one in you mouth and suck on it till the yoke moves then stick your tongue over the end of the hose. If the vacuum goes away then you have a leak. You can tell if the vacuum goes away because your tongue won't be stuck to he end of the hose anymore or the yoke will move back to where it was.

if you are not familiar with the plumping, you want to test the hoses that connect to the two plastic tubes that run along the side wall. Don't get them mixed up or the airplane will roll over when you engage the wing leveler.

Edited August 10, 2016 by N201MKTurbo

[MyNameIsNobody]

  On 8/9/2016 at 11:58 PM, N201MKTurbo said:

How to test the servos:

take the rubber hoses off the back of the turn coordinator. Stick each one in you mouth and suck on it till the yoke moves then stick your tongue over the end of the hose. If the vacuum goes away then you have a leak. You can tell if the vacuum goes away because your tongue won't be stuck to he end of the hose anymore or the yoke will move back to where it was.

if you are not familiar with the plumping, you want to test the hoses that connect to the two plastic tubes that run along the side wall. Don't get them mixed up or the airplane will roll over when you engage the wing leveler.

Expand  

Are you being serious?  It takes very little effort to defeat the vacuum in a PC system.  Let's not scare the kids...

[ryoder]

My bellows were popped like balloons in the wings.  Pull the inspection panel in the wing and see for yourself.  The panel on the pilots side of the airplane should be opened to check the ones in the back.  I owned my Mooney for over a year before I opened up that panel.  Seems silly not to open it.

[MyNameIsNobody]

...and the wing leveler is "always engaged"...unless you push a tiny widdle button and disengage it...That tiny widdle buttons "defeats the P.C." And we all lived happily ever after.

[Hedge]

Also, the turn coordinator might need to be rebuilt.  If the servos are good and there isn't a leak anywhere, it is probably the turn coordinator that is bad.  You can send it back to Britton and they can fix it pretty cheap and quickly.

 

Mark

[HRM]

  On 8/9/2016 at 10:02 PM, Dcflyn said:

The PC doesn't work. We've checked the vacuum which is ok. Has anyone replaced the bellows? How difficult is the job? Do the interior side panels need to come off?

Expand  

Doesn't work in what way? If it pulls to one side it is probably a wing servo--check those first.

The PC only involves (small) servos in the wings and they are a beyotch to replace. Easily checked by sucking on the hoses accessible in the tail. I was shown this by the great one at KGGG. When we concluded that the pilot side servo was shot, he pulled the access panel and let me feel where the rubber was split. He then proceeded to replace the thing on the tarmac in front of his hangar. Took about 45 minutes, multiple tools and expletives.

If you have the retractable  step, that is easy to check too since it is right there in the tail. if it is split I'd just let the hangar elves put some tape on it since it really does nothing critical to flight.

If you have a 3-axis system, then you will have elevator and rudder servos, but those do not affect the PC to my knowledge. It is practically a separate system.