Brittain Main. Positive Control System. Course and Heading. Altitude Control. Tidbits and Rules of Thumb. Parts Gallery.
Course and Heading
There are many different types of “heads” that control the course and heading in our Mooneys.
My control head is called a B 6. There are others called (I think) Accu-trak and Accu-fly.
For this area, I will only discuss the B 6 as I don’t know about the other controlling-heads
Theory of Course
This is to be completed… as I don’t fully understand it yet.
In theory, the B-6 should track a course based on the centering of the needle. In my plane, there is a toggle switch to track via the VOR or the GPS.
I think that they way that this is supposed to work is (for the GPS as an example). Set the selector to CAP, set the B-6 heading bug to “about” the course to capture, set the DG to the course to intercept. The B-6 should then intercept the course at about a 30-degree angle. When the course is intercepted, then the pilot is supposed to change to TRK to “fence in” the course tracking better.
When doing an approach, the LOC narrows the focus of the tracking even narrower.
Currently, (since the B-6 uses its heading bug (which is tied to its independent compass in the tail of the aircraft)) I have a quasi-educated feeling that the B-6 compass in the back needs degaussed. Sometimes, my heading but will veer off of course for no apparent reason.
TonyPynes wrote this useful, confirming tidbit on Mooneyspace.com
It’s important to note that to slave off of GPS your CDI must also be set to course. At least in mine it is required. once GPS and CDi are set you then select CAP (capture) on the B6 then select TRK (track). I have flown for hours in CAP mode so I am not sure the difference but then I use it for cross country cruising only and there maybe be other stages of flight that require this process. It also has a LOC selection which I have not used yet.
In a DM, Vance Harral noted:
Regarding course tracking, I think your readers will understand better if you say that the Accutrack/Accuflite/B-5/B-6 are capable of tracking a course as indicated by a CDI with analog left/right output signals. Starting the discussion by talking about switches that select between VOR and GPS is misleading. The Accutrack/Accuflite/B-5/B-6 doesn't know what a VOR or GPS is, it only knows it's receiving an analog electrical signal from a CDI that says "left of course" or "right of course", and by how much. So If you have two CDIs in your airplane, one of which gets input from a VOR receiver and another from a GPS receiver, then yes, switching between these two CDIs effectively switches between VOR and GPS navigation. But in the typical 430/530/650/750 setup, a single CDI can indicate either GPS cross-track deviation or VOR angular deviation, depending on whether the navigator is set to GPS or VLOC mode; and the GPS/VLOC switch is a function of the navigator mode, not any external switch.
So again, suggest you just say that the Accutrack/Accuflite/B-5/B-6 can track a course as indicated by a CDI output, and that it's up to the pilot and system installer to decide what inputs drive the CDI.
Theory of Heading
In my ‘66 E, the heading bug on the B 6, the Zone, and the system’s compass are integrated to provide accurate heading. See “Mooney Autopilot Operating Instructions” for Mooney’s vague operational direction.
B-6’s Compass
B-6 Compass
The B-6 compass is in the tail section of the aircraft away from most electrical fields.
References and Useful PDFs
Mooney Autopilot Operating Instructions
Brittain Industries Brittain Model B-6 Flight Control System Installation Instructions 11971-9 for Mooney Models M20C and M20E (Revision C signed 2-11-66 and 3/12-70 [sic]) This is a version of the plans where I colored the hoses in.
Mooney Navigation Coupler Operations & Service Instructions Manual No. 11990-1 (Issue A 5/31/01)
Information from Mooneyspace.com
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.