Brittain Autopilot Systems

[Vance Harral]

2 hours ago, Eric fddt said:

Since the G5 is not certified with the Brittain AP (from my understanding) I have to keep the DG connected to the AP in order for it to work on heading when I don't use the GPS.

This is the same story we got from multiple avionics shops when we looked into it earlier this year.  Everyone agrees it's possible to connect a G5 to a Brittain autopilot.  But doing so legally on a certified airplane requires either a FSDO field approval, or waiting on a hopefully-resurrected Brittain to complete the process of publishing certified drawings for the connection.  We're biding our time for now, hoping Brittain is alive enough to complete the drawings.  If that doesn't pan out, the most straightforward option would be to finally give up on the B-5 after many years of sorta-faithful service, and install a GFC-500 along with the G5(s).  While this is a lot less expensive than it used to be, it would still be a hefty chunk of change.

[HRM]

2 hours ago, Eric fddt said:

Since the G5 is not certified with the Brittain AP (from my understanding) I have to keep the DG connected to the AP in order for it to work on heading when I don't use the GPS.

You could keep the DG for use with the AP since you have to keep the vac system anyway. It just becomes totally redundant given the two G5's.

[211º]

After about 30 months of tweaking, learning, swearing. After having my hands and arms in both wings in convoluted manners, after sucking and blowing on different hoses and connections. And after using a vacuum pump many more times, Oh and also after reading so much on the internet and MS, I’m happy to report that the PC system, the altitude hold, the heading bug, and the tracking to the GPS are all now working on Queenie.

It was never that difficult to hand fly from Cincinnati to Tuscaloosa or Kansas City - but I think that it is going to be less tiring now.

If you have this system and want to talk any of it through, please free to DM me. I might be a useful resource and would not mind paying some of Jerry’s, Kevin’s, and Cecilia’s information forward.

It is a good, well-designed, simple system.

[outermarker]

GREAT! Since you are now the unofficial resident expert, do I fly to you or do you make house calls? Better yet....did you make a video of all the steps?

albert 

[211º]

No video is available yet... but I will try to put all of the steps and some of the different helpful documents together in one package.


Sent from my iPad using Tapatalk Pro

[Browncbr1]

On 2/27/2019 at 11:48 AM, Vance Harral said:

This is the same story we got from multiple avionics shops when we looked into it earlier this year.  Everyone agrees it's possible to connect a G5 to a Brittain autopilot.  But doing so legally on a certified airplane requires either a FSDO field approval, or waiting on a hopefully-resurrected Brittain to complete the process of publishing certified drawings for the connection.  We're biding our time for now, hoping Brittain is alive enough to complete the drawings.  If that doesn't pan out, the most straightforward option would be to finally give up on the B-5 after many years of sorta-faithful service, and install a GFC-500 along with the G5(s).  While this is a lot less expensive than it used to be, it would still be a hefty chunk of change.

The drawings have been done for a long time.. see attached two alternate methods.   I was told they sent these to Garmin, but my guess is that no one pushed or followed up with Garmin.

Brittain G5 Dwg Rev A.pdf G5 Hook Up, No Transformers.pdf

[Yetti]

It's two wires.   I would have to guess there is no certified "data" to hook to the various manual DGs with heading bugs or the various GPS sources.    Why would the G5 be treated different than any other input source?

[cliffy]

Just a thought-

I would think that there would be a difference in approvals for VFR only steering and full IFR approvals. 

[Eric fddt]

I got the G5 installed (to replace the attitude indicator but kept the gyro DG) in my M20E and I love it but not my PC system (an Brittain autopilot as well) doesn't work anymore.

The installer told me he removed the old attitude indicator and had to block those 2 suction hoses and had to lower the suction pump since an instrument was removed from the system.

Was that the right way to do it ? Any idea why the PC system doesn't work anymore ?

Thanks in advance for your help. 

[HRM]

12 minutes ago, Eric fddt said:

Was that the right way to do it ? Any idea why the PC system doesn't work anymore ?

Probably not. (1st question)

The PC system (2nd question) is actually quite simple, but a few parts can be problematic. You need good aileron servos, and those are easy to check. Then you need to look at the Brittain documentation for the PC system, which can be looked at as independent of the 2-axis and 3-axis system. Nothing flies like a Mooney with the PC. While I was doing some IFR training once the CFI/I commented "Your rudder skills are excellent!". I barely touch the rudder, he was not aware of the fact that my E had the PC system. In fact, with an operable PC you can pretty much steer with the rudder pedals 

[Eric fddt]

2 minutes ago, HRM said:

Probably not. (1st question)

The PC system (2nd question) is actually quite simple, but a few parts can be problematic. You need good aileron servos, and those are easy to check. Then you need to look at the Brittain documentation for the PC system, which can be looked at as independent of the 2-axis and 3-axis system. Nothing flies like a Mooney with the PC. While I was doing some IFR training once the CFI/I commented "Your rudder skills are excellent!". I barely touch the rudder, he was not aware of the fact that my E had the PC system. In fact, with an operable PC you can pretty much steer with the rudder pedals 

Do you have an idea how he should had done it ? The PC system and autopilot worked fine before the G5 installation.

[Andy95W]

17 minutes ago, Eric fddt said:

Do you have an idea how he should had done it ? The PC system and autopilot worked fine before the G5 installation.

No, but I understand why he did it.  The attitude indicator and DG each need about 2-3 inches of vacuum, or about 5 total.  Removing one instrument, he reduced the suction at the regulator to probably 2.5 or 3".  Unfortunately, the PC system needs 5", so yours now doesn't have the vacuum "muscle" that it needs to fly the airplane properly.

I don't know what the right resolution should be, but your DG will probably run just fine at 5", although it might need overhauled sooner.

[HRM]

3 minutes ago, Andy95W said:

I don't know what the right resolution should be, but your DG will probably run just fine at 5", although it might need overhauled sooner.

Should just need to bump the regulator up a bit.

[Eric fddt]

1 minute ago, Andy95W said:

No, but I understand why he did it.  The attitude indicator and DG each need about 2-3 inches of vacuum, or about 5 total.  Removing one instrument, he reduced the suction at the regulator to probably 2.5 or 3".  Unfortunately, the PC system needs 5", so yours now doesn't have the vacuum "muscle" that it needs to fly the airplane properly.

I don't know what the right resolution should be, but your DG will probably run just fine at 5", although it might need overhauled sooner.

Thanks Andy, so you are confirming that what he did to those hoses was ok so all he has to do ions is crank the suction a little more ?

[Eric fddt]

1 minute ago, HRM said:

Should just need to bump the regulator up a bit.

Thank you !

[Andy95W]

11 hours ago, Eric fddt said:

Thanks Andy, so you are confirming that what he did to those hoses was ok so all he has to do ions is crank the suction a little more ?

Without seeing it myself, I really don't know- but it seems logical if your guy has any idea at all about a PC system. If nothing else, bumping up the regulator and test flying is the easiest trouble shooting route.

[Igor_U]

On ‎4‎/‎11‎/‎2019 at 7:40 PM, Eric fddt said:

The installer told me he removed the old attitude indicator and had to block those 2 suction hoses and had to lower the suction pump since an instrument was removed from the system.

 

Eric,

What does your vacuum gage shows after the install?

He might be right to reduce the regulator settings somewhat but I think it might be issue in blocking wrong hose(s). I'd like to hear about solution as I want to do the same at my next annual.

Thank you.

[takair]

On 4/11/2019 at 10:40 PM, Eric fddt said:

I got the G5 installed (to replace the attitude indicator but kept the gyro DG) in my M20E and I love it but not my PC system (an Brittain autopilot as well) doesn't work anymore.

The installer told me he removed the old attitude indicator and had to block those 2 suction hoses and had to lower the suction pump since an instrument was removed from the system.

Was that the right way to do it ? Any idea why the PC system doesn't work anymore ?

Thanks in advance for your help. 

Eric

Can you elaborate on the wing leveler not working?  Does it provide zero force to the servos?  In other words, do you feel any difference between hitting the disconnect vs not?  Even with low vacuum you should get some notable force....Andy the system will just be sloppy vs doing nothing.  If it is simply sloppy, then yes, bumping up the vacuum would help.  If you have zero force, I would start looking at the Britain lines behind the panel, pinched, kinked, broken or loose.  

[211º]

In my searches, I’ve been quite surprised at the loss of vacuum in connection points. Especially the t’s in the baggage area.

 

As a check you can remove the t’s and insert the correct size outer diameter rubber or nylon tubing that matches the plastic (red and green) tubing’s inner diameter. Connect the hoses from the front to the wing hoses.

 

This also has the benefit of keeping (the highly probable leaking) rudder servos from the test.

 

Then go taxi the airplane. As you push the right rudder the turn coordinator should deflect and cause the ailerons and yoke to turn the opposite direction. (This should occur with or without the rudder hoses connected)

 

My Occam‘s razor list of most likely issues:

 

Thumb button - go to Home Depot and buy a pack of rubber washers for $5. Replace both washers on the thumb button. 30% chance that this will fix vacuum issues.

 

Rear/rudder servos. They’re behind the battery in a caustic location. Before contorting your body and scarring your head, remove them temporarily from the equation as noted above.

 

After you disconnect these lines, get a hand vacuum pump from Harbor Freight and try to vacuum the lines to 5 psi. With any luck after 20 or so pumps you’ll begin to see the rudder or aileron deflect. If it deflects and holds 5psi, smile as that part of the system checks out.

 

If all four lines check out, I would think that the T is leaking. When they’re off, try to plug two ends and suck on the third. These T’s always feel like they leak. I think that these T’s and the connectors are highly suspect in any system. (And relatively easy to swap out)

 

No need to try to test the red and green lines that run to the front as they’re connected to a filter and won’t seal.

 

If the wing servos lines don’t deflect. I’d look at these third. The boots are probably leaking. I ended up buying new servos as I couldn’t get them to seal well with re-taping. I don’t think that I have the knack.

 

Fourth the rudder servos. Same as wing servos but a different contorted challenge.

 

If you have altitude hold. It is separate from the green and red tube system but it does share and use the vacuum.

 

Right now, I can hold altitude or hold heading, but not both. I think that my altitude box in the back has a slow leak where a line should be plugged.

 

That minor leak has the benefit of making me wonder which part of the autopilot is better - heading hold or altitude hold. The PC system still works in altitude hold, so I frequently lean toward flying with that... unless I’m flying through falling pressure, at that point the airplane constantly tries to climb and needs resetting more frequently.

 

Dave

 

 

 

[carusoam]

Eric,

a small misspelled word early on... Now your wing leveler doesn’t work...

+1 for Dave Occam!  He has a fine razor. 

Use caution with using pressure measurements to substitute for volume of air flow...  they are kind of related...

Also Keep in mind... things that are attached to the vacuum line also can effect the vacuum instruments... adjusting the vacuum lower can effect how well the vac instruments are behaving... There is a vacuum regulator in the system for some reason, isn’t there?

 

If the wing leveler is no longer working... and you didn’t ask for that... your mechanic has done something you didn’t ask for...

I would want to talk to my mechanic about the proper way to execute the work I want to have done....

he may have some great ideas... but disconnecting something important can’t be what he had in mind.

 

PP thoughts only, not a mechanic...

Best regards,

-a-

[Badmoonraising]

i have a Brittain system in my 64 M20E. Seems to work fine as long as there isn't a lot of crosswind to fight. I assume the vacuum system in the limiting factor. When the system is working well. I find myself flying with my hand on the trim to maintain altitude. So really you can't call it a true autopilot. It simply help maintain a heading. 

[Hank]

6 hours ago, Badmoonraising said:

i have a Brittain system in my 64 M20E. Seems to work fine as long as there isn't a lot of crosswind to fight. I assume the vacuum system in the limiting factor. When the system is working well. I find myself flying with my hand on the trim to maintain altitude. So really you can't call it a true autopilot. It simply help maintain a heading. 

My AccuTrak does very well, crosswinds and all. Just move the heading bug further to the side the wind is coming from. I've had up to 30° crosswind correction during cruise before; my wife commented that it was weird looking out her window to see where we were going instead of the windshield.

[0TreeLemur]

On 4/24/2019 at 10:35 PM, Badmoonraising said:

i have a Brittain system in my 64 M20E. Seems to work fine as long as there isn't a lot of crosswind to fight. I assume the vacuum system in the limiting factor. When the system is working well. I find myself flying with my hand on the trim to maintain altitude. So really you can't call it a true autopilot. It simply help maintain a heading. 

The Accutrak II in our '67C is switchable between the output of two CDI's- one on the Garmin 430W, and the second on the KX155 NAV receiver.   When connected to the Garmin, it follows a magenta line really well, automatically adjusting for the crosswind, it does what is needed to keep the needle centered.   Given the wobbly nature of some VOR signals it is not as solid when driven by the KX155.  While not approved for approaches, it is a true 1-axis enroute autopilot; when engaged all I have to do is maintain altitude with tiny trim adjustments.  I'd love to add Brittain altitude hold, but it seems that parts for that system are exceedingly rare.

[Ross Taylor]

This thread has so much good information, I've read through it twice.  I have downloaded the Stability Augmentation Systems installation manual (so fun to see the great hand drawn details) and all the manuals I can find on the B6 we have.  I also looked at the 60 or so photos on the Brittain site.  But, in all of this, I'm not clear on what the altitude sense chamber looks like.  Because of the symptoms we have, I'm guessing diaphram i stretched out... and I have read that it can be either inside the cockpit or in the tail.  Does anyone have a photo of that chamber, please?  Maybe @211º ?

Thanks!

[211º]

From talking to Jerry a long time ago, I think that the altitude chamber and trim chamber are the two black boxes that are stacked in the tail cone. Mine (and many) have CCW and CW marked on them. But alas, I do not know which is which.

In that same conversation, Jerry noted that the altitude hold sometimes wouldn’t work too well because pilots can still descend with the altitude hold on... just over power the system like we do when turning without pushing the yoke button. That descent without turning the altitude hold off stretches the two diaphragms.

After looking at the pictures it looks like the altitude hold is the one on the bottom.