Brittain AP Help Needed

[Jon Reese]

I am the soon to be owner of a '66 F, and the autopilot is said to be inop. It has a B6 Brittain. Does anyone know of a shop to repair/diagnose/rebuild other than Brittain? I called them and the message said they are closed and trying to eventually get back open. Not sure what options there are for replacing it......

[takair]

1 hour ago, Jon Reese said:

I am the soon to be owner of a '66 F, and the autopilot is said to be inop. It has a B6 Brittain. Does anyone know of a shop to repair/diagnose/rebuild other than Brittain? I called them and the message said they are closed and trying to eventually get back open. Not sure what options there are for replacing it......

Let us know the issue. Have had some recent success with a few installs recently. Sending an IM too. 

[Mooneymite]

2 hours ago, Jon Reese said:

I am the soon to be owner of a '66 F, and the autopilot is said to be inop. It has a B6 Brittain. Does anyone know of a shop to repair/diagnose/rebuild other than Brittain? I called them and the message said they are closed and trying to eventually get back open. Not sure what options there are for replacing it......

Jon, the PC is an incredibly simple autopilot.  The T&B is probably outside the expertise of the average owner, but the rest of the system is rather Rube Goldberg simple.  While any repair must be signed off by an A&P, you can do a lot of trouble shooting for leaks.  Once you discover the leak, it can usually be fixed with Permatex, electrical tape, or some other simple fix.  There are several copies of troubleshooting guides floating around the Internet.

I've kept mine going with very little effort for almost 25 years.

[Vance Harral]

2 hours ago, Mooneymite said:

Jon, the PC is an incredibly simple autopilot.

Careful.  The OP didn't say he had a "PC" system.  He said he had a Brittain B6.  That is a three-axis Brittain autopilot capable of nav tracking and altitude hold.  In addition to the T&B and servos everyone correctly describes as simple, the B6 also has a control head unit full of electronics (not modern ones) with a complex rotary mode switch, as well as a complex altitude control unit, and the associated vacuum switches and relays required to make it work.

Our own @211º has been through the Brittain saga, and was kind enough to collect a bunch of information from a bunch of different sources, and organize it at https://www.windfield.farm/brittain-autopilot.  It's the best reference I know of on this class of Brittain autopilot.  TLDR summary: it is feasible - if a little gray from a legal perspective - to patch cracked vacuum lines, re-seal servo boots, etc.  But if there's an issue with the control head unit or the altitude control box, you're effectively out of luck.  It is extremely difficult to get service for these modules, and any service you could actually get is one-hundred-percent not legal.  Only Brittain holds the legal authority to do this work, and they're not taking any customers.

 

[211º]

One thing to note... regardless of the status of the B6 and its board, the altitude component is completely separate from the B6 circuitry. So, if you determine that the B6 is not operating correctly, you can still have an operating altitude hold (which in well rigged Mooney may reduce your workload significantly during long cross countries).

There are two layman's tests that you can do on the B6 from the cockpit without getting any tools out.  

For the PC, when idling on the ground at (say) 1000 RPM, turn the little knob on the yoke all of the way left and right - if it (even slowly) deflects the ailerons, then you may be in business.  If one deflects slower/doesn't deflect, then the vacuum isn't holding on just one side as well (I always have to think it through to remember which side this indicates the leak is on).

Second layman's test: On the ground again and at 1000 RPM again, turn the B6 to HDG mode and turn the dial to about your plane's heading.  Then turn the dial 90 deg left and then 90 deg right of your plane's direction.  If the aileron's deflect, then it indicates that (at least) a portion of your B6 is working.

[211º]

BTW, my B6 was inop when I bought my 20E... through about 3 or 4 years and finding little things that needed tweaked and finding some geniuses on MS and working with my A&P, it works better and better.  The moments when a little portion of the system come alive or begin to work will make you smile quite a bit.

[Yetti]

buy a mity vac and get to checking.   Usually just replacing some tubing or taping a boot and you will be back in business

[Jon Reese]

Wow thank you for the great advice. I will do some troubleshooting and then report back!

[Yetti]

There is a distribution block on the port wall of the baggage compartment.  That is a great place to start.   Well actually the self test in the flight manual is the best place to start.

Edited July 23, 2021 by Yetti

[Vance Harral]

4 hours ago, 211º said:

the altitude component is completely separate from the B6 circuitry

Electronically, this is true.

Mechanically, the switch that engages the altitude hold is mounted in the BI-601 head unit.  If the switch itself has an issue, repair will require opening the BI-601 unit for service.  To my knowledge, only Brittain can legally do this, and they're not accepting work.

I'm not trying to discourage the OP from working on their autopilot.  It is certainly true that the B6 system consists of multiple sub-systems, and even just getting some of them to work is nice.  We have a B-5 in our airplane, which was inop at the time of purchase.  We got the wing-leveler (PC) component working fairly easily and quickly.  Heading hold came later, though we never have gotten it to be quite as precise as we'd like.  Nav tracking came even later, and we didn't get the altitude hold working until about 8 years into ownership.

[211º]

1 hour ago, Vance Harral said:

Mechanically, the switch that engages the altitude hold is mounted in the BI-601 head unit.

Funny, I came "this close" to making that distinction.

[Vance Harral]

3 hours ago, 211º said:

Funny, I came "this close" to making that distinction.

It wouldn't matter except for the regulatory framework regarding who can disassemble a unit for maintenance and repair.

[Browncbr1]

9 times out of 10, the reason a Brittain is inop is because the rubber hoses behind the panel are old and cracked.   Check the rubber hoses connected to your turn coordinator and follow all vacuum circuits from there

[carusoam]

Welcome aboard Jon!

As you can see there are many Britain’s alive and well around here…

There are many maintenance materials that can be checked…

Go MS!

Best regards,

-a-

[0TreeLemur]

The Brittain system rocks when working.   You can approach troubleshooting incrementally.   First get the PC system working.  Next, troubleshoot the nav coupler.  Follow that up with the  pitch control/altitude hold.  If the PC system isn't working, then the nav coupler won't work.   As @Vance Harral and @211º said, the pitch control/alt. hold system is largely independent except for a switch/valve in the B6.

[211º]

I thought of @0TreeLemur and his posts from a while back where he flew one leg by hand and one leg with a working-well autopilot. Yesterday, I did the same thing, but on a single flight - encouraged by a failed vacuum pump. It is good to see how much better a pilot I am with a working Brittain system.