How to “Use” Brittain Autopilot

[Nukemzzz]

3 hours ago, Lawyerpilot said:

Thanks Hank, I am confused, if you look at my picture of the B6 you will see that there is a HDG, CAP, TRK, LOC selection switch and the altitude hold and pitch trim knobs are not even installed and I don't see any servos installed in the tail for pitch control.  These is a magnetic sensor installed which suggests the opposite, that it has at least HDG control,  The knobs and the ability to dial in a heading are consistent with direction control, but no altitude.  Are you familiar with any B6 publications?  Do you know if the Brittain parts are interchangeable?  Like could I hook up a Brittain DG and that would manage the system instead of a remote gyro?  Lee 

I’ve read a lot on Brittain and I’ve seen very little on your model. Perhaps and earlier version of the system. It seems to be a combo of the accuflight and accutrac with you able to select a heading bug with a slaved compass in the tail, but then also able to follow a track. You’ll have to control altitude with your trim wheel in cruise which isn’t a big deal I don’t think. 

First thing is probably to find your 4 servos and get them working. None of the rest works if the boots are bad. Once it’s working try flipping those switches and turning dials to see what happens?

[Lawyerpilot]

30 minutes ago, Nukemzzz said:

I’ve read a lot on Brittain and I’ve seen very little on your model. Perhaps and earlier version of the system. It seems to be a combo of the accuflight and accutrac with you able to select a heading bug with a slaved compass in the tail, but then also able to follow a track. You’ll have to control altitude with your trim wheel in cruise which isn’t a big deal I don’t think. 

First thing is probably to find your 4 servos and get them working. None of the rest works if the boots are bad. Once it’s working try flipping those switches and turning dials to see what happens?

Great info!  I just conducted a vacuum test at the red and green lines behind the panel at the firewall.  Entire line checked out.  It’s holds vacuum pressure at 5 per the manual.  Ailerons deflect when vacuum is applied.  From here now I need to figure out how to reconnect to the B6.  Someone else mentioned the system can be managed by a turn coordinator instead of a remote gyro.  I wonder if a DG could also provide the gyro input?  

[carusoam]

There are Brittain Branded TCs that get panel mounted...

If you have the 65 mini TnB, the TC would be better...

If you fly in IMC... you are already aware that TCs in the real world are not very good... and second AIs are all the rage.

 

PP thoughts only, not a CFI...

Best regards,

-a-

[Guest]

My 66 E model had the gyro between the firewall and instrument panel.  I took it out and installed a new turn coordinator with the vacuum controls on the turn coordinator.  It worked fine.

I’ve never seen a DG with vacuum outputs for the autopilot.

Clarence

Edited July 3, 2020 by M20Doc

[Lawyerpilot]

Hey guys, thanks I really think I might get this thing running.  I think what I am hearing from the guys with experience is that I need to get a t/c and hook it up to the red and green lines and then somehow connect the new turn coordinator to the B6 control head.  Did I get that right?  I assume the magnetic sensor in the tailcone also connects directly to the B6 control head.  Once connecting the magnetic sensor in the tailcone and the turn coordinator output to the B6 control head I will have magnetic course control.  Did I also get that right?  Right now my understanding is that I just need a serviceable Brittain Turn Coordinator and I will have all of the components and it should work.  The turn coordinator was the missing component.  All of this feedback is fantastic!  

[Ross Taylor]

Do you have electric gear in your C?  That gold pressure switch looks like my gear airspeed switch, but mine is mounted on the back of my airspeed indicator.  I don't see another one in our Brittain system...so that may not be part of your Brittain system?  Or...I'm totally wrong and I have one of those in my Brittain system too...but just haven't found it.

You mentioned that your "pitch trim" knob is missing. That empty spot is for the trim "eye".  Here's what mine looks like - and here's a Brittain page that shows what the different switch positions do:

 

[Nukemzzz]

5 hours ago, Lawyerpilot said:

Great info!  I just conducted a vacuum test at the red and green lines behind the panel at the firewall.  Entire line checked out.  It’s holds vacuum pressure at 5 per the manual.  Ailerons deflect when vacuum is applied.  From here now I need to figure out how to reconnect to the B6.  Someone else mentioned the system can be managed by a turn coordinator instead of a remote gyro.  I wonder if a DG could also provide the gyro input?  

I think you are confusing the PC and Autopilot systems. The PC system came stock on all these planes and it is simply a wing leveler. The Turn Coordinator that you speak of is just to level the wings. It uses the gyro in the TC. I’d start first with trying to figure out where your stock gyro is located (Or where it is supposed to be) before going to install another. You should also have a pilot valve in the system that disables it if vacuum on the circuit gets low. It’s effectively a vacuum solenoid actuated with vacuum. I think they often go bad as well. 
 

Try and find the system diagram for your vintage system. It’s probably on the forums somewhere. 

[Nukemzzz]

Update on my system. 

I found the missing two elevator servos. The rudder ailerons are shot. So far I’ve replaced the diaphragm on one. The aileron servos look good. Also found a cracked hose. With a little luck this system will just work when I get flying again in about a month!

Old boot:

What’s inside (note I installed the retaining chord when I put back together, it didn’t have it):

Put back together (picked up the 33+ tape today):

[Ross Taylor]

These are the docs which most helped me.

Brittain Autopilot Manual.pdf Brittain_IM 11971 Rev. -, Model LSA-2.pdf

[Vance Harral]

2 hours ago, Nukemzzz said:

I think you are confusing the PC and Autopilot systems. The PC system came stock on all these planes and it is simply a wing leveler. The Turn Coordinator that you speak of is just to level the wings.

Probably not true.  While there are many Brittain variants, my guess is the OP's B-6 system works very similar to our B-5.  In the B-5 system, electrical turn left/turn right signals from the autopilot head are sent to the Turn Coordinator, to drive its vacuum shuttle valve left/right to induce turns for lateral navigation.  So the Turn Coordinator is not "just to level the wings", but is in fact the electrical/vacuum interface between the navigational functionality in the autopilot head, and the servos which steer the airplane.

[Nukemzzz]

39 minutes ago, Vance Harral said:

Probably not true.  While there are many Brittain variants, my guess is the OP's B-6 system works very similar to our B-5.  In the B-5 system, electrical turn left/turn right signals from the autopilot head are sent to the Turn Coordinator, to drive its vacuum shuttle valve left/right to induce turns for lateral navigation.  So the Turn Coordinator is not "just to level the wings", but is in fact the electrical/vacuum interface between the navigational functionality in the autopilot head, and the servos which steer the airplane.

The Turn Coordinator replaces the under dash gyro and yoke mounted trim Knob found on mine.  There is a rotating bias valve behind it that equalizes the pressure when it reports wings level and not yawing. So you believe this TC somehow accepts electrical signals to bias as well?

[cliffy]

Before you buy anything get the correct manuals and find out just what you have and what you need. 

Get the manuals and read them and learn how and why it works so you don't make mistakes.  

The manuals tell all. Don't guess!

As a last thought - there IS an STC connected with the installation. It should be in your log book somewhere

[211º]

On 7/2/2020 at 10:50 AM, Nukemzzz said:

I have picture #1 above (remote gyro) for PC with Accurak and altitude hold added.  What's strange is I don't see any elevator servos.  Shouldn't they also be in the tail section?

In the back you should have the larger elevator servos only if you have altitude hold on your aircraft. You can also differentiate the elevator servos as they have yellow and blue vacuum lines going to them. 

There should be two same-as-size-as-the-aileron servos (BI-706) back there connected to a red or green vacuum line.

[211º]

15 hours ago, Lawyerpilot said:

Hey guys, thanks I really think I might get this thing running.  I think what I am hearing from the guys with experience is that I need to get a t/c and hook it up to the red and green lines and then somehow connect the new turn coordinator to the B6 control head.  Did I get that right?  I assume the magnetic sensor in the tailcone also connects directly to the B6 control head.  Once connecting the magnetic sensor in the tailcone and the turn coordinator output to the B6 control head I will have magnetic course control.  Did I also get that right?  Right now my understanding is that I just need a serviceable Brittain Turn Coordinator and I will have all of the components and it should work.  The turn coordinator was the missing component.  All of this feedback is fantastic!  

@Lawyerpilot, I am editing this on the fly a bit and hope that it'll make sense.  The first thing that would have helped me a ton is to think of the Positive Control system and the autopilot system (the BI-603 and its components) as two separate systems.  If you can get the PC system to work, you will have the "poor man's autopilot" system working... and that will create the your first smile as that system does a pretty good job at reducing pilot workload and confirming wing leveling in IFR conditions).  Once you get that working, then as you move on to the checking the actual autopilot, you'll get a bigger smile as (say) you get even just the heading function to work).

I think that you and I have the same system for direction control - my BI-603 has a pull-button for altitude control too (but that is just a pneumatic switch (no electronics).

Autopilot: I think that I have a manual to check the BI-603 to make sure that it is receiving power and is in working order - it involves sliding the unit out a little bit and then checking voltages while in different autopilot configurations and/or using the heading bug.

PC System: I think that you were the person asking about directional control - there is a "roll trim" button above the clock on the yoke that balances the aileron input from side to side to compensate for passengers or asymmetrical fuel loading/use.  I'll find and post a photo of mine.  I've heard that some units also have this mounted on the panel.

PC System: Also on the yoke, you should have a pressure relief button on the left hand side. If/when you open the clock panel on the yoke, there should be four 3/16" vacuum tubes. One goes to the pressure relief button and three go to the roll trim button.  (on the pressure relief side, one of the nipples doesn't have a hose attached to it - it is an open air line. I'm guessing that this is where the pressure/vacuum relief air comes from).

PC System: About your photo with the two Ts and the red and green lines going to them, if we talk about just (say) the red line. From that T, one red line goes all of the way back to the ailerons (ultimately the left wing) and rudder servo (there is another T here at the baggage area).  Attach the vacuum tester here (at the front T area) to this line to check a whole part of the system (not just the vacuum hose from the baggage area to the aileron and its servo) but (a) the red vacuum line left of the pilot behind the side panel, (b) the T at the baggage area, (c) the line from the baggage area to the rudder servo, (d) the rudder servo, (e) the line from the T to the aileron, and (f) the aileron servo.  If you can hold 5 psi, you have much of your path solved.

PC System: A second line from that T goes to the Pilot Valve (I don't know what this valve does, but a line goes there).  

PC System: The third line goes to the Rate Gyro (not the Remote Gyro).  This Rate Gyro also has an adjustable "stem" on it that can balance the vacuum system between left-level-right (10" Hg - 0" - 10" Hg). This stem is not adjustable in flight or with any frequency as it is Allen-wrench tightened. I'll find a photo of mine looking up from near the rudder pedals (my hunch is that you may be missing this piece).

Dave

PS: I may have portions of this wrong, I'm a guy trying to pay it forward as Mooneyspace helped me learn about and tweak the systems over the years.  As @carusoam frequently states "Dammit Jim, I'm a pilot not an airplane mechanic" - or at least I hear that every time he adds his disclaimer.

First Photo: bottom of the Rate Gyro. (there is a strong warning in publications - don't ever adjust the slotted thing, only adjust with the stem).

Second Photo: Behind the clock on the yoke.  The Roll Trim "button" with the three 3/16" lines attached.  The relief valve line and its open nipple are visible in the back.

Third Photo: another view of behind the clock/valves.

Fourth Photo: My BI-603.

Fifth Photo: Another view of the Rate Gyro.  Look in the 11968 Manual for a side view of this gyro.

[211º]

@Lawyerpilot, regarding the BI-603 and checking its operation, see the attached Brittain document 11968-1. (FYI, there is also a 11968-2 document that has to do with altitude control - the document naming convention was a bit confusing to me as initially I thought that "-2" was a revision of "-1".

I've also attached the "base document" 11968 that has to do with just the PC system.

Finally, I've attached the 11971-9 document as it shows the entire B-6 installation (I think our installations are (if I recall correctly) the B-2B installation, but they are very similar - I think the the only difference is that we don't have the eye-ball leveler in our BI-603 unit - it is blanked out.

MM 11968-1 Mooney Nav-Coupler-Heading Lock Operation and Service Instructions.pdf MM 11968-2 Mooney Pitch Control Operation and Service Instructions.pdf MM 11968 Mooney PC Operation and Service Instructions.pdf

11971-9 Brittain B6 Installation Instructions coloredIn.pdf

[211º]

@Lawyerpilot, the poor-man's way to check PC and Autopilot systems (maybe you have a tweaked system that uses different parts - it seems that there was a lot of transition between 65-66-67 production.

PC System: when taxiing, push one rudder, the aileron/yoke should deflect in the other direction.  If it moves in one direction or the other only, that is a pretty good sign as it implies that the PC system is working but that there is probably a vacuum leak somewhere.

Autopilot: On the ground when the aircraft is running and vacuum is flowing (maybe a little higher than 1300 on the RPM), turn the auto pilot to Heading and turn the heading bug on the BI-603 to 90° left and right of the direction that your plane is facing. If the autopilot is working, it'll deflect the ailerons/yoke toward the heading direction.

[Vance Harral]

11 hours ago, Nukemzzz said:

The Turn Coordinator replaces the under dash gyro and yoke mounted trim Knob found on mine.  There is a rotating bias valve behind it that equalizes the pressure when it reports wings level and not yawing. So you believe this TC somehow accepts electrical signals to bias as well?

Again, there are multiple Brittain systems, with multiple gyro units.  The best advice in this thread is from folks stressing the importance of using the manuals for the specific system one is working with.

That said, to answer your specific question, the B-5 system makes use of a Brittain TC-100-EVT turn coordinator.  Here's a picture of a TC-100-EVT on Mooneyspace.  Note the wiring cable with the multi-pin connector.  That's the electrical connection to the B-5 control head.  So yes, that particular Brittain Turn Coordinator accepts electrical control signals that control the pneumatic shuttle valve.

I don't know if the B-6 system uses the TC-100-EVT or similar.  But in general, the nav control unit has to have some way to "tell" the pneumatic servos to turn left/right to track a heading or course.  Consequently, there has to be an electro/pneumatic interface somewhere in the system.  In at least some Brittain systems - particularly the B-5 - that electro/pneumatic interface is built into the Turn Coordinator itself.  It's possible other Brittain autopilot systems have a separate control valve independent of the TC, such that the TC has no electrical connection other than power/ground for gyro drive motor.  I'm not intimately familiar with anything other than the B-5 system.

[Ross Taylor]

@Vance Harral describes the B-5 well.  In our B-6, there is a gyro (separate from the TC) between the panel and the firewall.  That gyro is all-vacuum and controls the PC roll through an internal variable balancing valve.  The B-6 control unit sends electrical signals to a separate shunt valve (86005-1) that converts the electrical signals to vacuum inputs.

In looking at @Lawyerpilot photos, and chatting with him, it looks like he's missing that servo...and maybe the gyro?  And...many thanks to @211º for posting this colorized doc, which I didn't have...it's amazing how much the color helps sort things out...and thankfully, I'm not red/green color blind.

On a side, but related note, I just bought a PC system from another MSer and I took a vacuum pump to the hangar yesterday.  I also just ordered a differential vacuum gauge, which will be here this week.  My plan for this is to lay it all out on a board, connect it, and video how it works.  I'll also dig into the gyro and see if I can identify replacement bearing options.  And finally, I'm still trying to source suitable replacement rolling diaphragms for the servos.  These systems are impressive and I need to keep mine going for a long time.

[Lawyerpilot]

Thanks to Ross and 211 we now have installation Manuals and pubs and they are telling all!  I was afraid I would never find any when I first started this project and the manuals are gold!  Thanks again everyone.  At this point I have 4 good servos and a sealed line that actuate the ailerons when 5kg of vacuum is applied.  With the installation publication and everything is Becoming clear regarding the necessary components.  Can’t thank you guys enough, the support has been very inspiring and motivating!

Edited July 4, 2020 by Lawyerpilot

[carusoam]

The Brittain company is still in business, sort of... @CSmith is the gal for Brittain...

They had some NOS of the colored tubing that may be helpful...

I see in the drawings above that there may be some rubber hose being used...

Rubber hose was good in 1965... it doesn’t age very well...

So... be on the look out for crumbling latex rubber hose...

It even shows up in modern airplanes every now and then...

Best regards,

-a-

[Hank]

The rubber hose under the panel was originally windshield washer fluid hose . . . . No idea of a good replacement, but modern automotive vacuum hose comes only in 1/16".increments and skips the 1/8" sizes.

[Ross Taylor]

5 hours ago, carusoam said:

They had some NOS of the colored tubing that may be helpful...

That's good to know.  And Aircraft Spruce has the clear/white Poly-Flo which, I'm assuming, you could mark red and green...unless the color is part of the spec?  If anyone needs 3/8-inch red Poly-Flo tubing, there's an 80-foot roll on the Bay for $70 shipped.  That would do one side of about 4 planes. 

[Lawyerpilot]

I am learning so much!  Thanks everyone!  To learn the system i got all of the technical manuals as everyone one sent to me, and I also got a return call from Cecilia (very helpful and friendly) at Brittain systems and they still plan to be back in business In the future, but the best part is they still are providing technical support on a part time basis, How cool is that!  Anyway, I purchased all of the components for the 1967 installation with the TC100EVT.  I wanted to make a bench test so I understand how the whole thing works.  As you see I have the TC100EVT, the pilot valve, the pilot cut off valve and the roll trim valve in these photos.  I bench tested the electric gyro in the turn coordinator and it seems to work as it should when powered.  It is dual powered and will also be hooked into the vacuum system and attached to the red and green servo lines aft of the firewall to the 4 servos.  I picked up these parts with the help of Larry (very helpful and friendly) At Wentworth Aviation right here in Minneapolis for a reasonable price.  I wanted to share my update and next step is to connect the marked hose connections with poly flo and other tubing in the aircraft.  The technical manuals provide all of the testing and troubleshooting procedures.  I also printed out all the part numbers and diagrams for this installation. The aircraft is in annual and I am working with the AI on this.  Once I get the basic PC system functioning I will move on to get the B6 to operate properly for navigation.  This is a fun project to do the restoration and learn more about the brilliance of the simplicity of the original NASA Apollo technology that was state of the art in 1967.  With my next step in mind, does anyone know what this blue plug coming off the TC100EVT is for?

Edited July 24, 2020 by Lawyerpilot

[carusoam]

Nice write-up LP!

My 65C TnB had a similar blue plug to power it... the TnB used 12V ship’s power...

The blue plastic is amazingly still deep blue after 50years...

Al Mooney probably bought a surplus box of 50k units after the war some time and used it for everything....

Best regards,

-a-

[Lawyerpilot]

Thanks @carusoam, the TC100EVT is powered from the inverter on one side, but this plug comes out the other side, like it should connect to something else.  It is not needed to operate the PC.  It is directly inline with the power input.  One thought I had is that maybe it is just an extension of the inverter power to daisy chain to something else for power.  The schematic doesn’t show anything else attached.  The other thought is that this could be output to the B6 autopilot.