Britain AP with G5 HSI

[FastTex]

Has anyone connected  a G5 HSI to a Britain B6 autopilot? I think I have a B6 since I only have the heading bug (no ALT hold) which works great but my mechanical HSI has the glidescope stuck on the flag and fixing it (I have already overhauled it a few years ago) is more expensive than a G5. I wonder if the G5 heading bug can do the same.

 

[FastTex]

Found some references on this forum and reached out to a few folks. Please post in here if you have updates or additional info. 

Thanks!

[N201MKTurbo]

If the Brittain is currently connected to a DG or HSI for heading control, it should work.

The problem is, the modern paradigm is that if the wiring isn't in the install manual, the STC doesn't apply. You should have your IA talk to your FSDO about a field approval. 

[FastTex]

I see, thanks. What a pain...and yes my Brittain is connected to my HSI and the heading bug works.

[FlySafe]

49 minutes ago, FastTex said:

I see, thanks. What a pain...and yes my Brittain is connected to my HSI and the heading bug works.

Hi FastTex, not sure which FSDO region you are in but i have the same setup and tried for a field approval with the Richmond VA branch and was turned away; reason i got on the GFC500 install wait list with a G5 hsi.  good luck

[N201MKTurbo]

3 hours ago, FlySafe said:

Hi FastTex, not sure which FSDO region you are in but i have the same setup and tried for a field approval with the Richmond VA branch and was turned away; reason i got on the GFC500 install wait list with a G5 hsi.  good luck

How did you approach the FSDO and what exactly did they tell you?

[Vance Harral]

I'm in the middle of trying to get this question answered for a Brittain B5 (very similar to the B6), through the Denver FSDO.  Here's what I know so far:

The DER I'm working with says feasibility hinges on whether the FSDO personnel who would grant the field approval consider the B5 to be a, "simple, single-axis autopilot system with limited control authority", as defined in table row  D.13h(1) of the "Major Repair and Alteration Job Aid" document which accompanies FAA Order 8300.16.  That's the governing document for autopilot system modifications, and whether they can be field approved.

This is a tough sell for the B5, because (1) it includes a pitch control and altitude hold system, albeit one that operates completely independent of the lateral control system involving the DG/HSI; and (2) even ignoring the pitch control system, there are servo boots connected to the rudders as well as the ailerons, which arguably makes it at least a 2-axis system.  Frankly, I'd be in better shape if we had an older AccuFlite rig, but even that might not be viewed as "simple".

If my DER can convince the FSDO to consider the B5 a "simple, single-axis autopilot system with limited control authority", he is willing to help me pursue a field approval for a G5/Brittain connection.  His estimate is that it would cost between $5000 and $10,000 to do so, i.e about half the cost of throwing away the B5 and installing a Garmin GFC500 in its place.  It's unclear to me if all that money would go in his pocket for consulting, or if the FAA actually bills applicants for their time (you'd think it would be "free" being a federal government organization, but who knows).  But it's extremely unlikely I could do this without going through a paid DER consultant anyway: I lack detailed knowledge of the rules and process, I lack any direct connections to the FAA, and I lack the patience to develop these things.

If the FSDO decides the Brittain B5 is not a "simple, single-axis autopilot system with limited control authority", the only path to certification is a one-time STC.  My DER says certification and flight test for such a thing runs about $50K, so obviously a non-starter.

Net result of all this is that I'm unlikely to pursue a field approval, but I did agree to pay the DER for a couple of hours consulting time to get an answer to the "simple, single-axis autopilot system with limited control authority" question.  I'll report back here when he gets back to me.

The frustration, of course, is that none of this has anything to do with whether a B5/G5 interface would work.  Everyone agrees it would.  But if you want your certified airplane to continue being legally certified, the paperwork rules are what they are.

[jamesm]

Thanks for sharing Vance,

The wing lever that I use to have installed in a '67C was on all the time I could over ride it in turn or any roll maneuver. I would be  curious to know what  constitutes limited control authority if  the FAA  say the Brittian autopilot does not have limited authority.  I can not image that are is too much different other wing lever and autopilot.  As I understand it  they have same components other than the autopilot has a rate gyro in vertical and lateral axis maybe one axis or both. I don't know how more simpler you can get than Brittain  autopilot. 

But it's the FAA some are good and reasonable while  others no so much.

 

 

 

[Vance Harral]

I don't know what constitutes "limited authority", and as you note, our opinion doesn't matter - only the opinion of the decision makers at the FSDO.

To be fair to those guys, it's not difficult to construct a sound argument either way.  You've constructed the pro- argument, which I agree with.  The con- argument goes like this: "The autopilot has three pairs of servos that connect to aileron/rudder/elevator, and it can hold a heading, intercept and fly a course, and not only hold altitude, but also pitch attitude.  That's neither 'single axis' nor 'limited control authority'".

Maybe I shouldn't say that out loud...

[FlySafe]

21 hours ago, N201MKTurbo said:

How did you approach the FSDO and what exactly did they tell you?

As a CFI-II i work with the FSDO and know serval on 1st name basis. I contacted them and they then passed me to a gentlemen in their group who deals with these sorts of issues.  He asked for the FMS/STC/Operating manuals on the Brittain AP (accuflite, accutrak and altitude hold in my case) and the G5HSI and any wiring drawing i might have showing possible connections for the interface (there are some unofficial drawings on other threads for at at least the heading bug input from a G5).  He reviewed the documents and about 3 weeks later gave me call saying essentially they take a hyperconservative approach when it comes to AP integration; he did not even feel comfortable allowing just the heading bug input given lack of covering STC. Said if i wished to work with a DER to generate more data and evidence for consideration they would be happy to reconsider. I decided to stop at that point as Vance mentioned in his message due to associate costs to go down that path, feeling $ spent on the GFC probably significantly less and its an assured modern solution.

[Nukemzzz]

This is all very informative.  I’ve been wondering about this.  One thing I’m confused about is I’ve seen several folks reporting that they are driving the Brittain system with Garmin 430W.  I don’t know why this would be any different. Is the brittain system connection covered by the 400 series install process?  Also, I’m wondering if you would have better luck with the new Garmin 275 units. They advertise integration with older autopilot systems if I remember correctly. 

[FlySafe]

I asked my installer that very question about the G 275 and hit the same road block, Brittain not listed on the STC ;(  Good question about the 430w - Brittain connection. and one I can not answer for sure, as that is what i previously had before moving to a new navigator; however, i suspect it was allowed because the CDI/HSI was listed as being approved for the Brittian as appose to the case with the G5.

[carusoam]

We should invite the Brittain guy/gal.... to the conversation....  @CSmith (Cecilia)

Best regards,

-a-

[Vance Harral]

On 1/26/2021 at 9:02 PM, Nukemzzz said:

One thing I’m confused about is I’ve seen several folks reporting that they are driving the Brittain system with Garmin 430W

Couple of ways this can be done.

First, the terms of the STC for various Brittain autopilots allow them to be driven from various CDI indicators, several of which are compatible with Garmin navigators (either by name or by interface).  In this setup, the CDI outputs an analog DC voltage to the autopilot giving it left/right deviation info, and the autopilot converts that to steer left/right signals.  So the autopilot is not really being "driven" by the navigator in this case, at least not directly.  Rather, the navigator drives the CDI, and the CDI drives the autopilot.  This works OK for basic course tracking, but it won't correctly do anything" fancy" like flying around a hold.  It's also unclear to me whether it is actually legal - strictly speaking - to engage the autopilot when the CDI is in GPS mode.  So I have never done this, of course!

Second, Brittain did have drawings to interface their autopilots to at least one GPSS roll steering unit (I think it was the DAC GDC31).  So there are a few people flying around with a 430W or other Garmin navigator driving a roll steering unit, and the roll steering unit in turn feeding heading data to the Brittain system.  You make this work by putting the autopilot in heading mode, and flipping a switch that muxes the autopilot heading input between the roll steering unit and the conventional heading interface for the Brittain.  Again, Brittain made drawing for this back when Jerry was still alive.  This is the slicker setup, as roll steering will follow more complicated GPS courses, and it is completely on the up-and-up to fly GPS courses this way.

The problem we're facing in the time of the Garmin G5/GI-275 is, we'd like to connect the DG/HSI to a Garmin GAD29B adapter, which can produce the analog signals the Brittain needs; then interface the GAD29B to the Brittain autopilot.  That's different enough that no existing approved STC or drawing from Brittain addresses it.  Jerry was working on these drawings around the time he passed away, and there are copies floating around showing the connections.  But from a legal perspective it doesn't matter, because they were never approved by the FAA.

[Vance Harral]

9 hours ago, carusoam said:

We should invite the Brittain guy/gal.... to the conversation....  @CSmith (Cecilia)

Best regards,

-a-

My airplane partner tried reaching out to Cici via e-mail just last week, but no response.  Hopefully she is well, and I continue to root for Brittain.  But the longer they stay in this state of "deep hibernation" - where they can't even supply parts, much less service - the less optimistic I am about Brittain ever again being a viable concern.  It's possible to keep the Brittain system going as long as the only thing that fails are the simple mechanical components.  But if our control head unit with its printed circuit board and big multi-plane control switch goes south, I don't know of any viable path - either legal or gray market - to repair it.

[0TreeLemur]

On 1/29/2021 at 11:05 AM, Vance Harral said:

My airplane partner tried reaching out to Cici via e-mail just last week, but no response.  Hopefully she is well, and I continue to root for Brittain.  But the longer they stay in this state of "deep hibernation" - where they can't even supply parts, much less service - the less optimistic I am about Brittain ever again being a viable concern.  It's possible to keep the Brittain system going as long as the only thing that fails are the simple mechanical components.  But if our control head unit with its printed circuit board and big multi-plane control switch goes south, I don't know of any viable path - either legal or gray market - to repair it.

I received a reply from her to a question I had about getting a TC100 inspected in early January.  Brittain is still not up and running.

[N201MKTurbo]

There are two issues here. driving a Brittain from a 430W using the left/right error signals should be no problem. The problem comes from using a G5 as its heading source. Actually, heading error source. Technically, it is a no brainer, it will work. The FAA just wants someone to prove it will work. The proof consists of a giant pile of expensive paper so they can claim they did their due diligence in case of a problem.

[RobertGary1]

I think the answer is no. My shop spent a much of time trying to do that for my gi-275s for my electric Britain. They kind of hooked something up but it doesn’t really work 

[Yetti]

The Brittain installation manual defines the acceptable inputs in terms of signal levels.   This is why a Garmin 340 would be acceptable input to the Brittain system.    If the newer systems have the same signal levels output there should be no reason that the data is not acceptable to the installer.   Since we are not cutting airframes should be a simple sign off of an IA.   See attached manual for Data as prescribed by the Manufacturer.

 

 

Manual No. 11990-1 Mooney Navigation Coupler Operation and Service Instructions.pdf

[Vance Harral]

23 hours ago, Yetti said:

Since we are not cutting airframes should be a simple sign off of an IA.

I believe you're talking about the difference between a "minor modification" which requires only an IA signoff, and a "major alteration" which requires either an STC/337 or field approval.

I'm not sure if you're talking about course error or heading error at this point.  For course error, yes the installation manual defines acceptable inputs in terms of signal levels, which I understand to be the key that lets you e.g. wire up to a GI-106 indicator.

If you're talking about building a heading interface out of a GAD29B with transformer connects based on the Brittain being similar to a Cessna 400-series autopilot, that kind of interface work is specifically defined as a type of major modification in the "Major Repair and Alteration Job Aid" document which accompanies FAA Order 8300.16.  This is not a fuzzy, arguable thing; the Feds have taken a specific position that changes to autopilot interfaces constitute a major alteration.  I'm sure if you looked hard enough you could find a seasoned IA on the brink of retirement who would sign off such a thing as a minor mod anyway.  But there's no way it would hold up when push came to shove.  And if your argument is that push is unlikely to come to shove, then why bother with the sign off in the first place?

Edited February 9, 2021 by Vance Harral
clarify heading vs. course interface

[Yetti]

58 minutes ago, Vance Harral said:

 

I'm not sure if you're talking about course error or heading error at this point.  For course error, yes the installation manual defines acceptable inputs in terms of signal levels, which I understand to be the key that lets you e.g. wire up to a GI-106 indicator.

 

Which would be the same as the heading bug input from a variety of manufactures.  and the same input from a Garmin 430/530  would it not?   If you read the Brittain manuals closely they will take both high and low inputs such as ARINC429.    I think i have an email from Cecil stating the same.

 

[Yetti]

or  in my case connected to the LORAN unit.

[N201MKTurbo]

1 hour ago, Vance Harral said:

I believe you're talking about the difference between a "minor modification" which requires only an IA signoff, and a "major alteration" which requires either an STC/337 or field approval.

I'm not sure if you're talking about course error or heading error at this point.  For course error, yes the installation manual defines acceptable inputs in terms of signal levels, which I understand to be the key that lets you e.g. wire up to a GI-106 indicator.

If you're talking about building a heading interface out of a GAD29B with transformer connects based on the Brittain being similar to a Cessna 400-series autopilot, that kind of interface work is specifically defined as a type of major modification in the "Major Repair and Alteration Job Aid" document which accompanies FAA Order 8300.16.  This is not a fuzzy, arguable thing; the Feds have taken a specific position that changes to autopilot interfaces constitute a major alteration.  I'm sure if you looked hard enough you could find a seasoned IA on the brink of retirement who would sign off such a thing as a minor mod anyway.  But there's no way it would hold up when push came to shove.  And if your argument is that push is unlikely to come to shove, then why bother with the sign off in the first place?

It doesn’t matter if a grizzled IA signed it off or not. If the FAA got interested, they could cancel his sign off in a split second. Heck, if you are trying to get a bogus sign off, just do it and don’t tell anybody about it. Just don’t crash because of the autopilot. 
 

BTW, I’m not raging against you Vance. 

[jetdriven]

The Britain autopilot is driven off the main analog +L and +R outputs.  These generally are sent to a CDI indicator. But the signal is spliced to the Brittain first. So, WRT course tracking, the G5 is irrelevant. 

[Yetti]

1 hour ago, Vance Harral said:

If you're talking about building a heading interface out of a GAD29B with transformer connects based on the Brittain being similar to a Cessna 400-series autopilot, that kind of interface work is specifically defined as a type of major modification in the "Major Repair and Alteration Job Aid" document which accompanies FAA Order 8300.16.  This is not a fuzzy, arguable thing; the Feds have taken a specific position that changes to autopilot interfaces constitute a major alteration.  I'm sure if you looked hard enough you could find a seasoned IA on the brink of retirement who would sign off such a thing as a minor mod anyway.  But there's no way it would hold up when push came to shove.  And if your argument is that push is unlikely to come to shove, then why bother with the sign off in the first place?

I am still trying to resolve your statement with the 1000s of "navigational equipment"  connected to the Brittain units and installs by competent installers along with many annual inspections unless there has been some change in the regulations that has suddenly made those install illegal.   A garmin 430 can drive a heading indicator no?