Brittain Autopilot Systems

[cliffy]

In fact I'd take a complete B5 from the grim reaper if he had on but I've never seen one available. 

[Yetti]

12 hours ago, SkyTrekker said:

$3500 for 3 axis AP including labor is crazy amazing.  Well-done!   

I'd love to do it all myself and have an AI sign off on it.  Problem is, this is my first plane, I've never worked on one before, and I don't have a relationship with an AI yet.  Even if I did, I would not trust me (yet) if I were him/her.  I would love to spend a day with a great AI, working from the nose to the tail on my E and learning as much as I could about everything in between.  Maybe do a couple of service or maintenance jobs with them.  Then I think I'd be ready for taking on something like installing an autopilot system.  I guess I'll print out the documentation that Brittain sent and study up.  Either way I go, knowing everything about the system will be a good thing.

In the meantime, I've emailed Cecelia to get a quote for Brittain installing the B-11 and B-12, with me assisting.  We'll see what they come back with.

-Sia

I had my Brittian system redone in Tulsa.  Great folks.  For the Owner Maintenance items if you want to pop down to Brenham we can go through some of them.   Just a PPL, not an IA or AP....But I have read the first book.  Done two owner assist annuals and gaining the trust of the local IA. 

Edited July 15, 2017 by Yetti

[MyNameIsNobody]

21 hours ago, cliffy said:

All I've needed for years is the altitude hold but I haven't found one yet. I'd buy it today if I could find one.

You guys must be luckier than me to find one.

I was vigilant...daily ebay for a long, long, long time. Just lucky I got there before you Cliffy

 

[HRM]

On 7/14/2017 at 2:07 PM, cliffy said:

In fact I'd take a complete B5 from the grim reaper if he had on but I've never seen one available. 

The owner of one of The Mistresses assembly-line sisters got tired of the Brittain and had his whole 3-axis system pulled out. I bought it for 2 AMU and then paid 2.5 AMU to have the Alt Hld and Pitch Control added to mine. It's the easiest thing in the world to maintain and works great. 

[cctsurf]

6 hours ago, MyNameIsNobody said:

I was vigilant...daily ebay for a long, long, long time. Just lucky I got there before you Cliffy

Couldn't you just set up a ifttt.com (If this then that) on Ebay to notify you of anything that fit the bill?  It would take out a lot of the time for the daily vigilance...

Just a thought.

 

Edited July 15, 2017 by cctsurf

[MyNameIsNobody]

1 minute ago, cctsurf said:

Couldn't you just set up a ifttt.com (If this then that) on Ebay to notify you of anything that fit the bill?  It would take out a lot of the time for the daily vigilance...

Just a thought.

 

I'm an analog guy in a digital world (the chase is half the fun)

[cctsurf]

BTW, to the poster looking for altitude hold, um...  http://www.ebay.com/itm/Brittain-AutoPilot-Altitude-Hold-components-complete-/122449456861?hash=item1c828e6edd:g:0I8AAOSwIWVY83b8&vxp=mtr

[Andy95W]

2 hours ago, MyNameIsNobody said:

I'm an analog guy in a digital world (the chase is half the fun)

 

[cliffy]

I resemble that last remark!  :-) :-)

The hard part to find is the "eyeball"  Lots of the boxes around.

[211º]

I'm learning more and more about the Brittain B-6 Autopilot system that I have.  Since this is the longest thread, I'm going to post seemingly obvious things that I've learned here.

To remove the B-601 until from the panel, see the attached pictures for some tips.

[211º]

This is the BI-201 Sensor. in my M20E, mine was mounted in the tail cone and accessible through the large pilot's side access panel. Although it looks rigid, it freely swing's back and forth.

[211º]

My M20E has the B-6 System with Altitude hold. The panel (aka B-601) used to have the eyeball, but that was blanked out prior to my ownership.  As I understand, there were two sides (two halves of a circle split vertically - each with a horizontal white line).  As the pilot would pull the "Alt Hold" to turn on the altitude hold, he would align the floating, horizontal while lines to match up.  I think that this aligned the pitch of the airplane to assist in (easily (easier(?)) holding altitude for the AP.  This eyeball had two vacuum lines to it. I think that these vacuum lines now (ultimately) route to a pitch sensor (in my airplane) in the tailcone area - right under the altitude hold box (I'm still learning about how this works).

[211º]

Over the past couple of weeks, I've chatted with Cecelia and Kevin at Brittain quite a bit.  Kevin gave me pointers on removing the B-601 panel from the aircraft. My hope was that there was something wrong with the unit and he'd be able to fix it and I'd be back in autopilot-business.  We chatted after he bench tested the unit and told me that the unit was working fine (and nothing needed to be repaired).  He then suggested that I use a voltage meter and see if I get a voltage between the ground and positive on pins 1 and 2 of the cable that connects to the back of the B-601.  

After several  trips and hours upside down, under the pilot's side panel, I was able to find a 22-guage wire that was broken... and was then able to find its broken partner.  Reconnecting these wires, I was able to get voltage back to Pins 1 and 2.

Cecelia sent the (now cleaned and yellow-tagged) B-601 back to me.  This morning, I reinstalled the unit in the panel and taxied around the 500-foot ceiling airport.  In the run-up area, I turned the autopilot to Heading and turned the heading. Kevin told me that the system would turn the yokes/actuate the ailerons . And Whoop! The AP commanded a left turn.  See the video though, I'm thinking through it, but is appears that I must have a vacuum leak for right hand turns as the autopilot returns to center, but is not pulled to the right (i.e., the left boot releases it pressure, but the right boot doesn't pull the opposite direction past zero/level).

As I write this up, I think that I can narrow down the issues to a hose issue, boot issue, or valve issue by figuring out a way to see if the tail or possibly even just the rudder pedals move concurrently with the aileron left, center, right movement.  

AP_-_1.m4v

[Vance Harral]

1 hour ago, 211º said:

As I understand, there were two sides (two halves of a circle split vertically - each with a horizontal white line).  As the pilot would pull the "Alt Hold" to turn on the altitude hold, he would align the floating, horizontal while lines to match up.  I think that this aligned the pitch of the airplane to assist in (easily (easier(?)) holding altitude for the AP.  This eyeball had two vacuum lines to it. I think that these vacuum lines now (ultimately) route to a pitch sensor (in my airplane) in the tailcone area - right under the altitude hold box (I'm still learning about how this works).

To clarify, the "eyeball" indicator has a fixed side and a moving side, both with horizontal white lines as you say.  The vacuum lines actuate the moving side, which is essentially an indicator of how much force the system is applying to the elevator.  In other words, the vacuum lines are an input to the indicator, driven by an output from the altitude hold unit in your tailcone.  The (negative) pressure in the indicator lines is a down-regulated analog of the (negative) pressure in the lines to the elevator boots.

The primary purpose of the eyeball indicator is to give the pilot information on what to do with the elevator trim when the system is engaged.  If the indicator is consistently indicating an application of up elevator, the pilot should add some up trim, and vice versa.  The goal is for the lines to match, most of the time.  This indicates the most efficient trim setting, with the autopilot applying little to no elevator force in either direction.  But note that when the autopilot is working, the indicator is constantly in motion to small degrees.  You only adjust the trim if the average value is consistently above/below the fixed line.

In our system (B-5 instead of B-6 but the idea is the same), I find the eyeball indicator to have mixed utility at best.  First, I always trim the airplane for level flight prior to engaging altitude hold, so the indicator is mostly neutral most of the time anyway.  Momentary changes in the indicator aren't very interesting - again, that's just a confirmation the pitch actuator is actually working.  If the indicator is consistently high or low for an extended period of time, that means you've entered a very extended up/down draft, or that one of the boots is starting to leak.  A trim adjustment is appropriate in those cases, but those are pretty rare events.  More importantly, though, I don't think the indicator is intuitive at all.  Imagine for a moment that you look at it, and the movable line is higher than the fixed line.  What exactly does that indicate?  Should you trim up or trim down to fix it?  There's a correct answer, of course, but it's not obvious.

My motivation to be really educated about the pitch trim indicator and other operational aspects of the altitude hold is hampered by the performance of our system to date.  Our altitude hold "works", but performance is weak.  We think this is a combination of two issues in our system.  The first is the integrity of the seals for the tubing and valves associated with the altitude reference chamber.  Ideally these would be perfect.  In practice, they have a nonzero leak rate spec'd in the maintenance manual.  What this means is that if your altitude varies from the selected altitude for more than a certain amount of time, the reference chamber establishes a new normal, and holds that new altitude instead of the one you originally selected.  To prevent this, the system must be able to apply enough force to the elevator to correct altitude variances fairly quickly.  That's our second issue.  When we encounter an up/down draft, the system applies appropriate correction, but it's often too "soft".  Before the system can return the airplane to the originally selected altitude, the reference chamber leaks enough to establish a new reference.  We then have to disengage the pitch control, manually re-established the desired altitude, and re-engage.  In smooth air this might happen once every 10-15 minutes, which really isn't too bad.  In rough air - when you really want the altitude hold - it happens every couple of minutes.  So often that it's arguably like not having altitude hold in the first place.  We're hopeful performance can be improved by improving the reference chamber seals and/or increasing the gain on the elevator servos, but we haven't gotten around to addressing it yet.

[N601RX]

My altitude hold works reasonably well. It might vary 50-75 ft per hr. It's made up of 2 parts, pitch control and altitude hold. The altitude control reference chamber and associated plumbing valve shouldn't leak any. It consist of a diaphragm with one side connected to the reference chamber and the other side exposed to cabin attitude pressure. The diaphragm is attached to a small valve that directs more or less vac to the up or down servo. If the altitude control chamber pressure matches the cabin pressure the diaphragm and valve are centered and direct equal pressure to both the up and down servo.  It isn't hooked to the static port and is sensitive to internal cabin pressure/temp.  Opening the vent window in leve flight will result in a almost full down deflection of the yoke.

The pitch control is connected to the airspeed pitot tube and has a calibrated leak in it. It uses airspeed as well as a pendulum to detect pitch changes. 

When both are turned on the altitude hold and pitch control are plumbed in parallel with your servos and indicator. 

Edited November 4, 2017 by N601RX

[MyNameIsNobody]

You two have a much better understanding of your pitch/altitude hold systems than I do.  Thank you for the read.  I am glad that I had the system installed, but the altitude hold is wonky in my plane.  My co-owner flew the plane to witchita and Brittain did install.  I had the Accu-Trak and Accu-Flite already installed and the decision was made to NOT (due to space under the panel) install in cabin.  The diaphragm is in the rear by the retractable step.  When trimmed for level flight and you pull the pitch you must then adjust aggressively the trim (to trim out) down force...The window is NOT aligned (one is high one is low) when level flight/pitch is obtained with manual trim.  I think the system could be adjusted, but you would need to do multiple flights adjusting a little to get right.  NOT optimal to have the system in the rear of the plane no doubt...System hunts A LOT in rough air (altitude hold) so I do not use under those flight conditions (if you are into repeated porpoiseing you would love it)...

I had a refurbed step servo and all vacuum lines replaced when in Kansas at Brittain.  Should have had them also install the control that is in the T&B.  Mine is by the hydraulic fluid pot on pilot side access (Not easy to get to). I have the unit if mine starts to go...

[Browncbr1]

I've been working with Brittain regarding my dual G5 and gtn install and I'm happy to say that Garmin will be adding Brittain to the G5 HSI / gad29b stc.  It was supposed to be included with revision 9, but a deadline was missed.   It should be on the next revision.  

[Browncbr1]

On 11/5/2017 at 9:51 AM, MyNameIsNobody said:

.  When trimmed for level flight and you pull the pitch you must then adjust aggressively the trim (to trim out) down force...The window is NOT aligned (one is high one is low) when level flight/pitch is obtained with manual trim.  I think the system could be adjusted, but you would need to do multiple flights adjusting a little to get right.  

There is a pitch adjustment screw on the top of the box.   Basically, the box was installed on a different azimuth than straight and level, so the pitch screw needs to be turned.   Mine had the same issue when installed.   Roughly, one full screw turn for each 100fpm that the plane pitches after pulling the plunger.   If your plane pitches up after pulling the plunger, adjust the screw counter clockwise.    If down, then clockwise.  

[MyNameIsNobody]

2 minutes ago, Browncbr1 said:

There is a pitch adjustment screw on the top of the box.   Basically, the box was installed on a different azimuth than straight and level, so the pitch screw needs to be turned.   Mine had the same issue when installed.   Roughly, one full screw turn for each 100fpm that the plane pitches after pulling the plunger.   If your plane pitches up after pulling the plunger, adjust the screw counter clockwise.    If down, then clockwise.  

Thank you.  If you have a photo of the screw location on the box that would be super helpful.  Appreciate your reply.  Scott

[Browncbr1]

 

2 hours ago, MyNameIsNobody said:

Thank you.  If you have a photo of the screw location on the box that would be super helpful.  Appreciate your reply.  Scott

It's the only hole on the top of the computer box that has all the tubes plugged into it.  There might be a sticker or rubber plug covering it.  Some are labeled, some are not.    

[HRM]

On 11/4/2017 at 12:18 PM, Vance Harral said:

I find the eyeball indicator to have mixed utility at best. 

It is one of the key elements to owning a 'Buck Rogers' edition E. The eyeball, the swept antennae and the auto-retracting step are right out of a 50's SciFi movie.

As for the overall system, it is incredibly easy to troubleshoot and the folks at star fleet command are amongst the most helpful there are 

[MyNameIsNobody]

On 11/6/2017 at 4:03 PM, Browncbr1 said:

I've been working with Brittain regarding my dual G5 and gtn install and I'm happy to say that Garmin will be adding Brittain to the G5 HSI / gad29b stc.  It was supposed to be included with revision 9, but a deadline was missed.   It should be on the next revision.  

That is exciting.  Please keep us updated.

[MyNameIsNobody]

On 11/6/2017 at 4:03 PM, Browncbr1 said:

I've been working with Brittain regarding my dual G5 and gtn install and I'm happy to say that Garmin will be adding Brittain to the G5 HSI / gad29b stc.  It was supposed to be included with revision 9, but a deadline was missed.   It should be on the next revision.  

How does the vacuum driven Brittain system work?  My HI/DG with heading bug has vacuum line.

[Browncbr1]

8 minutes ago, MyNameIsNobody said:

How does the vacuum driven Brittain system work?  My HI/DG with heading bug has vacuum line.

You have to have a Edo Aire, or RCA G-502a or similar DG with heading bug in order to send a 4.5v signal (at 20 degrees)  left or right to the DG gain box that is part of the accuflite setup.  The DG gain box, then, sends a low voltage left or right signal to the B-501 valve, which regulates vacuum to either left or right aileron servo..  

The fact that the DG is driven by vacuum is irrelevant.  

[MyNameIsNobody]

2 hours ago, Browncbr1 said:

You have to have a Edo Aire, or RCA G-502a or similar DG with heading bug in order to send a 4.5v signal (at 20 degrees)  left or right to the DG gain box that is part of the accuflite setup.  The DG gain box, then, sends a low voltage left or right signal to the B-501 valve, which regulates vacuum to either left or right aileron servo..  

The fact that the DG is driven by vacuum is irrelevant.  

We are not on the same page.  The G5 heading has no vacuum, right?  How does it integrate with a Brittain vaccum system is my question...