430w/650 to Brittian CAP/TRK?

[TheTurtle]

I have a brittian autopilot.  cant remember the model number now.  It has cap and trk and theres a switch in my panel to switch between nav1 and nav2 which are currently kns80 and k 155.

Can it take a signal from a 430 or 650?  How about with a G5 HSI?

sort of thinking of putting some waas nav in the plane and just wondered if that was a possiblility.  Ive never even tested the cap and trk connected to my current radios but did have the brittian unit overhaul a few months ago.

[Vance Harral]

We have a GTN-650 and a Brittain B-5 autopilot in our airplane.  The system works well in NAV, TRK, and APPRCH (capture) modes.

That said, understand the Brittain is just getting its information from the GI-106 CDI we installed with the 650, not directly from the GTN itself.  The autopilot doesn't "know" it's talking to a GPS, it's just getting left/right track information from the analog voltage output of the CDI.  Really no different than when the CDI is receiving a VOR signal in VLOC mode.  Your current setup almost certainly works the same way - the autopilot gets information from the CDIs your KNS80 and KX155 drive, not directly from the radios themselves.

My understanding is it's possible to install a GPS roll steering computer such as the DAC GDC31, and interface it to the Brittain.  With this setup, you put the autopilot in heading mode, and the roll steering unit computes headings for the autopilot to fly, which result in it tracking the desired course.  This allows the autopilot to fly course reversals, holding patterns and other complex courses.  It's a nice feature, but not one we've been motivated to pay for.

I don't think a G5 indicator set up for HSI mode has traditional analog voltage outputs that can directly drive an autopilot, like the GI-106 and other CDI indicators.  My understanding is you can't interface the G5 with an autopilot unless you purchase the forthcoming GAD29B interface unit.  That unit is not yet certified, and the list of legacy autopilots for which Garmin intends to pursue certification doesn't include Brittain.

Edited July 31, 2017 by Vance Harral

[Browncbr1]

I have talked to Jerry at Brittain and he says he has converted many boxes to digital so that aspen pfds can drive the AP.  Same setup would be for a G5.  

Call Jerry and ask him how much $ for the DG box modification to accept digital inputs.

 

[Vance Harral]

1 hour ago, Browncbr1 said:

I have talked to Jerry at Brittain and he says he has converted many boxes to digital so that aspen pfds can drive the AP.  Same setup would be for a G5.

I have no doubt the technology for this works fine, but I've never understood the basis for certification.  Is Brittain getting field approvals for this sort of thing through their local FSDO?

That comment isn't meant to disparage Brittain, I really appreciate the way they support our autopilots.  I just wonder if there's potential trouble down the road when some over-zealous A&P or inspector says, "Where is the STC for this autopilot installation?"

Also, note that the converter box which allows the G5 to drive "legacy autopilots" isn't even certified yet (target date is later this year).  I have no doubt it can be made to work with the Brittain, but I wouldn't assume the certification and approval process to make it legal is guaranteed and/or quick.

[Browncbr1]

3 hours ago, Vance Harral said:

I have no doubt the technology for this works fine, but I've never understood the basis for certification.  Is Brittain getting field approvals for this sort of thing through their local FSDO?

That comment isn't meant to disparage Brittain, I really appreciate the way they support our autopilots.  I just wonder if there's potential trouble down the road when some over-zealous A&P or inspector says, "Where is the STC for this autopilot installation?"

Also, note that the converter box which allows the G5 to drive "legacy autopilots" isn't even certified yet (target date is later this year).  I have no doubt it can be made to work with the Brittain, but I wouldn't assume the certification and approval process to make it legal is guaranteed and/or quick.

good points.. i have no idea.

[Andy95W]

9 hours ago, Vance Harral said:

I have no doubt the technology for this works fine, but I've never understood the basis for certification.  Is Brittain getting field approvals for this sort of thing through their local FSDO?

That comment isn't meant to disparage Brittain, I really appreciate the way they support our autopilots.  I just wonder if there's potential trouble down the road when some over-zealous A&P or inspector says, "Where is the STC for this autopilot installation?"

As the manufacturer, Brittain has substantial leeway on what they can do to their own equipment, moreso than anyone working on it such as an Avionics shop.  They would need to provide documentation saying that it was modified by the manufacturer.  That should be all a future A&P would need to justify its legality.

[Vance Harral]

15 minutes ago, Andy95W said:

As the manufacturer, Brittain has substantial leeway on what they can do to their own equipment.

Hmm... This makes sense, but I'm curious how the details work.  It would be one thing to make trivial changes like swapping a resistor, changing a plastic fascia, etc.  But putting a digital interface on an analog autopilot seems like the kind of thing that would have to be re-certified.  At some point, a modification crosses the line from being a minor tweak to being a whole new product.

That said, documentation from the manufacturer of the autopilot itself seems like pretty solid ground to stand on.