Brittain Vacuum Hoses

[Shadrach]

This is an informational post for all of you who are operating the much beloved Brittain autopilot systems. The latex vacuum tubing (Brittain P/N 116-010-003) utilized behind the panel of all aircraft equiped with Brittain control systems seems to have a service life of about a 5 to 7 year at best. I replaced mine in 2010 and again this year at annual.  I bring it up because merely looking at the tubing is not adequate to determine it's condition. I know that in the past, deteriorating tubing had gone unnoticed during annual when it should have been replaced. I was surprised to see some minor deterioration last year. My IA and I agreed it was serviceable for another year. While that was true, it deteriorated a great deal in the past 13 months. Dan at LASAR said 7 years is about the best that could be expected. 

Below are pics of 7 year old tubing I removed this year. For the most part it looks fine until stretched slightly. Thankfully it deteriorates from the outside in. Good thing to stay on top off as losing vac on one side of the system will result in a very gentle uncommanded bank in one direction. 

P.S Sorry for the funky fingernail shots. I'm still due for my post annual manicure...

Edited November 11, 2017 by Shadrach

[HRM]

8 hours ago, Shadrach said:

The latex vacuum tubing (Brittain P/N 116-010-003)

Do you have to get that from Brittain, or are there other sources? Do you just buy an XX' roll or what?

Thanks!

[cctsurf]

 

[Shadrach]

6 hours ago, HRM said:

Do you have to get that from Brittain, or are there other sources? Do you just buy an XX' roll or what?

Thanks!

LASAR sells it for $2.69 pe foot. I bought 14 feet and had a comfortable margin left over. I have a PC wing leveler; an autopilot with additional features may require more tubing.

Edited November 12, 2017 by Shadrach

[Yetti]

The word from Brittain is that the left wing tubing does not last as long as the right

[Guitarmaster]

The word from Brittain is that the left wing tubing does not last as long as the right

I can verify that!

Sent from my XT1585 using Tapatalk

[MBDiagMan]

Is it typically only the tubing or does the tee fitting give trouble?

If you remove the belly pan below the tee and the access covers along the rear of the wing do you have enough access for changing it all or does some of the interior have to come out?

Edited December 19, 2019 by MBDiagMan

[Shadrach]

3 hours ago, MBDiagMan said:

Is it typically only the tubing or does the tee fitting give trouble?

If you remove the belly pan below the tee and the access covers along the rear of the wing do you have enough access for changing it all or does some of the interior have to come out?

The black tubing is only behind the panel. Like I said in your thread, verify everything is correct behind the panel before you nature to the wings and tail. I have never seen the red or green stuff fail. 

[Yetti]

3 minutes ago, Shadrach said:

The black tubing is only behind the panel. Like I said in your thread, verify everything is correct behind the panel before you nature to the wings and tail. I have never seen the red or green stuff fail. 

Mine did.  Brittain replaced it.  Says the red line fails more often than the green line.

 

[0TreeLemur]

Avoid rubber tubing.   Modern polymer tubing styles are so much more durable.  Nylon is very durable, abrasion resistant, flexible, stiff and clear.  Polyethylene- milky but very rugged.  That is what runs out to your pitot tube, and out to the vacuum servos..  Even Tygon (expensive but will survive the end of the planet) is great behind the panel.  Rugged, expandable, lasts forever.  Silicone- great for high temperature apps.  Not an A&P but I have worked with tubing much of my career.

[carusoam]

Tygon, is plasticized PVC...

Which, I think, is what Britain is using with their colored red and green tubes... the plasticized PVC part...

The PVC, in fact, lasts forever... but... the amount of plasticizer changes over time...

So the dimensions get tighter... and the flexibility gets more stiff... over the ensuing decades... splits may occur where it is stressed over barbs... or cuts may occur where tie wire is used...

 

The worst Mooney failures of PVC tubing is their use in the back-up vacuum systems in the tails of long bodies... the vacuum aided the removal of the plasticizer and the oily plasticizer was drawn towards the instruments...

Tygon is a high quality name for plasticized PVC... so at least order the Tygon by name... if not getting the real hose from Britain...

A lower quality plasticized PVC may look the same on the first day, but may not last as long as the Britain stuff has... and the risk of drawing plasticizer toward the instruments makes you think a bit more...

A forever plane with a large upkeep budget would probably consider using improved tubing and fittings where able...

For additional details for following exactly what the M20s used ask Celia at Britain.... I think she is still there...

PP thoughts regarding things I have read around MS... not a mechanic...

Best regards,

-a-

 

[Yetti]

16 minutes ago, carusoam said:

Tygon, is plasticized PVC...

For additional details for following exactly what the M20s used ask Celia at Britain.... I think she is still there...-a-

 

Emailed and spoke to her last week.

Why would nylon or polynylon tubing not be a better upgrade?  The stuff I ordered for my static lines was a parker hanilyn speced product.

 

[carusoam]

Parker Hannifin is one of my favorite suppliers for all things tubing and fittings... they supplied a presentation to a bunch of school kids back in the 80s... Mark Dinnerman was the young sales guy tasked with the presentation... I got trained on ferrels and compression fittings... and how not to mix up various supplier’s parts...

https://www.parker.com/portal/site/PARKER/menuitem.b90576e27a4d71ae1bfcc510237ad1ca/?vgnextoid=c38888b5bd16e010VgnVCM1000000308a8c0RCRD&vgnextfmt=EN

Today they are an aviation tubing supplier most often found in important places like O2 systems and probably brake lines....

So... upgrading the hardware of an AP from plasticized PVC tube pressed on barbs, held in place with wire is an excellent idea...

The original set-up worked for many decades... but if going the next step of upgrading a forever-plane... by replacing the old system with something a bit more modern... Parker probably has the parts...

If your static plumbing is using Parker parts, it would make additional sense to use similar Parker parts in the other locations...

As always... Check with your A&P, because I’m only a PP, known to make errors in my rush to type out half a good idea...
 

Hey, check that link above... Parker just announced they bought Lord!  You know....? Our donut supplier...   

I sense a baker’s dozen of donuts may have just got more expensive... wait... we only need 11... not 13...

Best regards,

-a-

[Shadrach]

On 12/20/2019 at 12:26 AM, 0TreeLemur said:

Avoid rubber tubing.   Modern polymer tubing styles are so much more durable.  Nylon is very durable, abrasion resistant, flexible, stiff and clear.  Polyethylene- milky but very rugged.  That is what runs out to your pitot tube, and out to the vacuum servos..  Even Tygon (expensive but will survive the end of the planet) is great behind the panel.  Rugged, expandable, lasts forever.  Silicone- great for high temperature apps.  Not an A&P but I have worked with tubing much of my career.

Perhaps, but unfortunately the IPC does not specify “tubing of choice”.  Furthermore the tubing behind the panel must be incredibly flexible (it’s about as rigid as overcooked pasta). I could not imagine the PITA it would be to try to route nylon behind the panel.