Brittain bellows as removed

[Alan Fox]

Brittain bellows removed from salvage aircraft 150 for the 4 and I will throw in the vinyl tubing that came out also , You may get a few good ones out of these , if not they will serve as good cores .....

[Hank]

I replaced all of my tubing, and especially the screw-together fittings, a few years ago. Wonderful improvement!

If someone has a non-functioning PC, this will be an inexpensive way to bring it back.

[Shadrach]

PM sent!

[Alan Fox]

Sale pending , thanks Ross

[Alan Fox]

sold

[markejackson02]

I replaced all of my tubing, and especially the screw-together fittings, a few years ago. Wonderful improvement!

If someone has a non-functioning PC, this will be an inexpensive way to bring it back.

 

How difficult is replacing the tubing?  Does the interior have to be removed?

[Alan Fox]

Yes it is a big deal to remove,  the tubing is heavy vinyl and should not need to be replaced....

[Vance Harral]

Hank, we replaced all our autopilot tubing at our most recent annual.  Doing so requires removing the left side interior panels, as the lines from the turn coordinator (and altitude hold unit, if you have that) run along the left side cabin wall.  I don't consider removing interior panels a particularly big deal, as you should be doing that periodically for SB 208 inspections anyway.  You also need to pull a few belly panels to route the lines to the wings and tail cone, but these are the same ones you remove for an annual inspection.  Routing the new lines through various clamps, connectors, etc. was more of a pain than removing the panels.

 

As for why we did it... agree with Alan that the tubing itself lasts indefinitely if undisturbed.  But, over decades of use, it tends to get cut or nicked for various reasons.  Maybe torn up when servo boots are R&R'd for maintenance, maybe nicked by a rock where it runs through the wheel wells, etc.  When we bought our airplane, the PC didn't work, and we traced it to a screw in the baggage compartment that had been driven right through the tubing.  The ends of the tubing that mate to fittings also get brittle, and it's harder to get a good seal.

 

All these problems can be repaired without replacing the tubing.  But over time you get a growing set of patches: holes covered with electrical tape, couplings that aren't part of the original design, etc.  Small leaks throw off the roll trim adjustment (ours was almost full travel to maintain level flight), and make the vacuum pump/regulator work harder to maintain nominal vacuum for the gyros.  In our case, we were debugging problems with the tubing for the altitude hold reference chamber, which requires an absolutely leak-proof system.  We couldn't establish the integrity of the tubing itself, and decided to replace the whole length of it.  So "while we're in there..." we replaced all the servo control tubing as well.  Kind of a pain, but certainly not the worst project we've undertaken in the last 10 years.  We did resolve our autopilot problems, and finally have a 100% functional B-5 with altitude hold system, which is really nice for cross country flying.  Hopefully the new tubing will be good for another 30-40 years.

[Hank]

It was old, leaky connectors and brittle tubing at the many plugins that made us exchange it. The A&P was not happy . . . I didn't have time off of work to help on that one.

[211º]

Reviving an old thread if no one minds…

 

Earlier today, I disconnected both the red and the green hoses from my 805. I applied – or rather tried to apply – a vacuum to both sides. The green gave a little bit a vacuum (not much at all) and the red side held absolutely nothing after several attempts.

 

While I will disconnect and plug the hoses near/at the T near the baggage area to see if I can get a vacuum on the hoses running in the left side wall, I am curious for opinions on whether the consensus would be to bet on the hoses being old and brittle or the servos/rubber leaking.

 

 

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[N201MKTurbo]

1 hour ago, 211º said:

Reviving an old thread if no one minds…

 

Earlier today, I disconnected both the red and the green hoses from my 805. I applied – or rather tried to apply – a vacuum to both sides. The green gave a little bit a vacuum (not much at all) and the red side held absolutely nothing after several attempts.

 

While I will disconnect and plug the hoses near/at the T near the baggage area to see if I can get a vacuum on the hoses running in the left side wall, I am curious for opinions on whether the consensus would be to bet on the hoses being old and brittle or the servos/rubber leaking.

 

 

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Servo rubber leaking.

[Vance Harral]

Don't bet.  Diagnose.

It's statistically likely to be leaking servo seals and statistically unlikely to be the poly tubing being "brittle", but that doesn't mean much on any particular airplane.  You also didn't mention a couple other possibilities, both of which we found on our airplane when resurrecting the Brittain system: bad seals at the interface between the poly tubing and the servos, and specific damage to the poly lines caused by interior panel screws being inadvertently screwed into the poly lines.  There's really no way to know without proper debug and diagnosis.

[N201MKTurbo]

21 minutes ago, Vance Harral said:

Don't bet.  Diagnose.

It's statistically likely to be leaking servo seals and statistically unlikely to be the poly tubing being "brittle", but that doesn't mean much on any particular airplane.  You also didn't mention a couple other possibilities, both of which we found on our airplane when resurrecting the Brittain system: bad seals at the interface between the poly tubing and the servos, and specific damage to the poly lines caused by interior panel screws being inadvertently screwed into the poly lines.  There's really no way to know without proper debug and diagnosis.

Well of course, but he asked for a bet not a reasonable discussion.

[Vance Harral]

46 minutes ago, N201MKTurbo said:

Well of course, but he asked for a bet not a reasonable discussion.

Point taken.  I guess I don't understand if the "bet" is just for fun, or if he's contemplating ordering parts in advance, or otherwise spending time/money without knowing what's wrong.  That's the sort of judgment call mechanics are often pilloried for here, but I suppose it's less of a sin if it's the owner themselves speculating.

[211º]

Yep. Just a simple bet. Sounds like Hank above had a lot of luck with renewing hoses. From tracking the hoses, they appeared to be solid, but those appearances may simple be wrong.

 

So a bet before I get all comfy in the baggage area at the T where I can try to see if two of the directions will move with a vacuum applied and the third will hold a vacuum.

 

I’ll get back out there and dig into it more in the next few weeks.

 

[Hank]

4 minutes ago, 211º said:

Sounds like Hank above had a lot of luck with renewing hoses. From tracking the hoses, they appeared to be solid, but those appearances may simple be wrong.

 

All Hank did was replace the connectors in the tubing, not the actual tubing itself. They were the old style compression fittings with rings on the tubing, and many of the fittings were cracked. New, modern fittings installed, much better performance.

[211º]

Aha! Thanks for that clarification. I see that now as I re-read.


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[carusoam]

Not sure if 211°‘S picture is a video or just a photo...

Be a betting man... I would bet there can be a lot of random things happening to plastics used in the 1960s... over 50 years...

Back then, drinking straws were made out of paper...

From the afore mentioned picture.  The green tube on the tee fitting isn’t held in place by a spring.  It’s spring is moved a few inches out of place... further up.  

Brittain used to sell tubing up to recently, at least... worth making a call, if wanted...

There are so many improvements to tubing and fittings and the means to make attachments over the years...

Expect taking a look at each piece to make sure it isn’t leaking, AND each spring is seated in the right place on each T....

A lot of MSers have discussed their methods of placing the proper tape in the proper place...

There is a whole thread or two on rubber bellows, broken molds and availability...

So, if it ain’t tape, expect tubes and tees, if not these, it’s got to be the rubber bellows...

It doesn’t get really expensive until you are looking for the valve...?

PP thoughts regarding tubing only, not a plumber... but I did sit through a lecture on fittings back in the 80’s presented by Mark Dinnerman who was teaching a bunch of engineering students how compression fittings work. He was the local sales guy for Parker-Hannifin back in the day...  (wish I could use that memory location for something more important). 

Parker-Hannifin is one of the suppliers for Mooney O2 systems... the other thing Mark mentioned... don’t mix and match fitting parts between manufacturers.... a feral from one supplier will not fit properly in another manufacturer’s fittings... guaranteed to leak later on down the line...  

Fortunately, these are simple tees with springs not real compression fittings...

you can bet, if something can go wrong, it will...

Best regards,

-a-

[211º]

OK, So I spent some time hunkered over the backseat today.

I was able to disconnect the red and the green hoses at the Ts in this area. I was happy to apply a vacuum to the red hose that leads to the left aileron and see that aileron deflect.  That line was able to keep a 5" vacuum for over 1 minute - Win!

Unfortunately, that was the only win.  Applying a vacuum to both the red and green that lead to the rudder did nothing but (literally) suck air.  

Applying the vacuum to the green/right aileron did nothing, but I did note that turning the aileron manually from inside the airplane did push air the other direction - I'm still thinking that through on what it means.

From the T to the front (to the 805) I was able to cap the line at the T then attempt to apply the vacuum to "just the line" (i.e., no bellows, joints, or cans) and that did not get any vacuum at all. So that makes me think that the hose on the left side of the cockpit is kaput (both the green and red).

So, I think that some items may be coming out of the cockpit in the not too distant future.

(an aside, I'm pretty impressed that the autopilot (and vacuum) were able to cause turns to the left at all as it seems that the hose is sieve-like).

PS: The picture that has a play button in the middle of it is a screen grab from a video.

[Vance Harral]

Before you disassemble/extract too much to get to the hose running down the left side of the cockpit... you might start by taking out the left (pilot) side carpet panel in the baggage compartment.  This is pretty easy and will expose "some" of the tubing, which you can examine for cracks and holes.  In particular, you can check if any of the screws holding that carpet panel in place were accidentally screwed into the autopilot tubing.  That was the primary source of initial leaking we found when resurrecting our Brittain autopilot.  If so, it's possible to patch such holes without replacing all the tubing.

If you have a borescope - and from the video above it looks like maybe you do - you can run it down the left side between the skin and the interior panel from the baggage compartment and possibly find other problems, though it might be a tight fit past the roll cage tubing.

Good luck with your debug.

[N5937Q]

Brittain bellows removed from salvage aircraft 150 for the 4 and I will throw in the vinyl tubing that came out also , You may get a few good ones out of these , if not they will serve as good cores .....

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[211º]

I did try to peer into the wall... and after being able to see just a little I took the panel off and began looking at the hose - it was then that I realized/fount out that there is another T... and it goes right to a filter - hence the inability to keep a vacuum.  On the other line, I also noted that/saw that a vacuum line was disconnected.

It does make a little more sense that the Polyflex line doesn't have a hole in it. 

Learning more about the plane, so I got that going for me.

[211º]

On 3/18/2018 at 7:28 PM, Vance Harral said:

Don't bet.  Diagnose.

It's statistically likely to be leaking servo seals and statistically unlikely to be the poly tubing being "brittle", but that doesn't mean much on any particular airplane.  You also didn't mention a couple other possibilities, both of which we found on our airplane when resurrecting the Brittain system: bad seals at the interface between the poly tubing and the servos, and specific damage to the poly lines caused by interior panel screws being inadvertently screwed into the poly lines.  There's really no way to know without proper debug and diagnosis.

You statistic likely comment is proving to be true.

Seals and servos are now more and more likely.  Now I need to create a logical plan of attack - perhaps the servos in the tail first as they're easier to get to.

[FBV]

I found a couple leaks in my servo today. My pc system has been pulling to the left for the last couple flights. Anybody have a spare they’d sell me? Any advice on how to patch them? I tried a bike patch kit and it worked for about 6 months. But with two holes now, it really needs to be replaced. Brittain is closed.


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[Chris from PA]

Give LASAR a call. I purchased a new one from them in February. It's my understanding that LASAR purchased quite a few from Brittain when they closed.

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