Vance Harral

That's exactly my question, actually. I know what the line "is". I just don't have a firm grasp of what it's supposed to mean to me as a pilot; or why it gets a specific depiction vs. just looking at the pressure gradient contour lines that arguably already give you the information it's depicting.

I've been trying to figure out if there is a reasonable way to connect a Garmin navigator to two CDIs at the same time, to solve the same problem as you: maintaining an existing interface to a Brittain autopilot. The place I get stuck is the OBS knobs of the CDIs. When navigating via VOR, or when navigating via GPS in OBS mode, the OBS knob matters, and the two CDIs can have different OBS settings. Even if there is some way to make this work with selector switches, it has the potential to be tremendously confusing, and my opinion is it's probably not a good idea.

Thanks for the explanation about the counterweights, that sounds reasonable. I'm less convinced about the thermal argument, but no need to start a debate on it. What's most important is that you have a set of procedures that work well for you, and you obviously do. Enjoyed the video, thanks for posting.

"Surge" is a vague term. Any chance you can elaborate on the exact concern with quickly advancing the throttle? Inability of the fuel servo to keep up with the sudden change in air volume? Inability of the prop governor to change the blade pitch quickly enough to maintain RPM? Something associated with the turbocharger? Something else? Enquiring minds want to know.

The thing that really jumped out at me about this document is, the sections for starting engines and ground run-ups are not check lists. They are textual, prescriptive descriptions of how to perform the procedure. That's helpful if you're in ground school trying to learn how to start and run up those magnificent radials in a DC-3. But I'd think anyone actually trying to use them as a checklist in the airplane would have trouble, and be prone to skip items. If that's not a problem in practice, feel free to ignore my comment. Those sections just look really incongruous compared to the rest of the document.

The partnership -> club number is 5, at least as of 2 months ago. We just added a 4th partner to our partnership, so that's pretty recent info from one broker plus Avemco.

Thanks for the follow-up, @kortopates. I'm still not entirely convinced the smoothness of landings and/or condition of pucks in Mooneys plays a significant role in sealant lifetime, but the comparison with the Cardinal is worth considering.

I was not aware Cessna Cardinals had wet wings with a substantially better service record than Mooneys. If true, that is certainly interesting data. Did Cessna use the same type of sealant in the 70s as Mooney? If not, then whatever they used is likely superior. If so, then yeah, the initial difference would seem to be the more direct coupling between the wings and the landing gear causing additional flex during ground ops. It's worth noting that there are a lot more Mooneys than Cessna Cardinals, and that may have something to do with the data too. But Wikipedia says 4295 Cardinals were built from 1968-78, so that's certainly plenty of data points. It's always been my understanding that sealant breakdowns and accompanying patch/reseal work with age are simply a fact of life in wet wing airplanes, be they Mooney, RV, Boeing, whatever. Say, 8-10 year life is pretty reasonable, 20-30 is quite good, and the conventional wisdom is that nothing goes longer than that. So the idea that most Cessna Cardinals have gone 40-50 years with no wet wing maintenance seems extraordinary, and worth a polite challenge. When I tried to look for information about this just now, what mostly turned up were comments about how the very few tank access panels in the Cardinal make tank reseals so extraordinarily difficult that nobody wants to do them, e.g. https://www.pilotsofamerica.com/community/threads/cessna-177-b.100637/. And here's a story of Cardinal wet-wing patches that went so badly that it led to a wing replacement: https://www.tennesseeaircraft.net/2017/11/15/when-more-is-less/ (scroll down to "Cardinal Fuel Tank Repair"). These are just anecdotes, but I'm good-naturedly skeptical of the claim that Cardinals have a much better wet-wing longevity record than Mooneys (or anything else).

When faced with the same choice, we scrapped our old #2 NAV/COM and CDI (KX-170 and KI-201), moved our KX-155 and KI-209 from NAV/COM 1 to NAV/COM 2, and purchased a new GI-106A CDI go go along with our new #1 NAV/COM/GPS. My opinion is that you should scrap your KI-209 or re-purpose it for the #2 radio, rather than trying to use it with a 430W/530W; and budget for a new/used GPS-capable CDI to go along with your 430W/530W. The GI-106 is the basic standard, they run about $1500 on eBay. The KI-209A will work and is cheaper, but my understanding is it requires additional equipment: a mode selector switch and external annunciator. I know the extra cost of a new CDI is an irritant, but installing one will allow you to use the CDI in GPS mode, which is useful. And it will in turn allow the Brittain to track a GPS course programmed into your navigator... regardless of whether doing so is strictly legal or not. Just to be sure we're all on the same page, my last couple of posts involve the Brittain tracking a simple course via CDI input, which is all I have direct experience with. There is also discussion in this thread about using Brittain autopilots to track heading via a heading bug on a DG and/or output from a roll steering unit like the GDC31. Those are separate topics I have interest in, but no direct experience with.

It depends on what you mean by "connect the 430W to the Brittain". If you mean using the the Brittain to track a VOR/ILS course tuned in the 430W's VHF nav radio and indicated on the KI-209, the answer is yes. If you mean using the Brittain track a GPS course you have programmed in to the 430W, I think the answer is no - you would need the KI-209A to do that. But I admit confusion, because you said, "In effect, the GPS is pretending to be a raw VOR signal from something like my KX155." That seems to imply your 430W is connected to your KI-209 (non-A), and yet still is somehow able to display deviation from a GPS course when the 430W is in GPS mode. I was not aware this is possible, and find several posts on various aviation boards to the contrary, e.g. this one right here on Mooneyspace: In any case, if you look at the pinout jetdriven posted above, pins 10 and 11 of the KI-209 are left/right outputs from the CDI, not inputs to the CDI. The inputs to the CDI from the radio are on other pins. jetdriven keeps saying you can "tee" off pins 10 and 11 to connect to the Brittain system, but I think that's incorrect - my guess is that if you trace the wiring in your airplane you'll find that pins 10 and 11 of your KI-209 are not connected to your 430W. Rather, my understanding is that the required autopilot wiring is a chain configuration, like this: radio ---(flag/ILS/VOR signals)--> CDI ---(left/right signals)--> Brittain ... not a "tee" configuration like this: radio ---(flag/ILS/VOR/left/right signals) -+-> CDI +-> Brittain In other words, the Brittain doesn't talk directly to the radio, it can only talk to the CDI. If I'm right about all that, your 430W doesn't, and can't, "connect" directly to the autopilot. The autopilot can only receive course guidance from the CDI, and what you're able to do with it is define by the capabilities of the CDI. In the case of the KI-209 (non-A), I think that means VOR/ILS data only, not GPS. If I'm wrong, and a KI-209 (non-A) CDI really can show course deviation from a 430W when the 430W is in GPS mode, then I guess you can get the behavior you want. If so, let us know, I'm always happy to learn new info.

I can also confirm the Brittain will work with a King KI-209 indicator. That was the #1 nav setup in the airplane when we bought it, and it's still the #2 nav. Per jetdriven's post above, seems like the hookup to the Brittain can be either from the CDI head or the radio itself. Ours connects at the CDI.

I think it's both useful and helpful to understand what's required to meet the certification standards, that is also part of the solution. I've got no objection to a technical discussion proceeding in parallel (and it wouldn't matter if I did, I don't control the board). Indeed, I've posted a bunch of technical data about Brittain autopilots trying to help others continue using them. My goal is to be helpful, not to be the "police". As for your rant about Garmin and the feds, I'm not here to defend them or Brittain or anybody else, just posting my understanding of the certification rules. Sounds to me like you've got a problem with the existence of the certification rules in the first place - that you think they contribute nothing to safety or usability. I'm sympathetic to that argument, I share it in many cases. But on that subject, your beef is with the industry, not me. One thing I think we can agree on is, most people who engage in grey-area maintenance and upgrade of this sort don't come to any grief because of it. The philosophy of "I'll do what I want and interpret the rules in whatever way is most beneficial to me", usually works out. Each owner is free to choose their financial/time risk tolerance in this area, just like they choose their own risk tolerance about the actual safety of what sort of flying to engage in. I do think a G5 connected to a Brittain autopilot via a GAD29B isn't going to pass muster with any official who actually cares to look, but that's the last I'll say of it.

I'm sure you can, but that's not the topic of discussion. The topic of discussion is, whose signature is required for the FAA to agree the installation is legal? Going all the way back to the beginning of this thread, the question is not what will work, but what is required for a legal, certified installation? Let's try turning this around. Why do avionics shops that install GPS navigators and autopilots hold a certified repair shop certificate, and employ certified repairmen? What authority does that convey, and what can the avionics shop do that an A&P/IA who does not hold such a certificate cannot?

Nobody, unless they apply for and receive a field approval or STC for connecting the boxes in question. That's what the original avionics company does. My guess is that "qualified radio technician" in the Brittain installation manual refers to a person holding an FAA repairman certificate, employed at a certified repair shop whose certificate covers radio repair and service. When you have avionics installed at an avionics shop, the entry you get in your logbooks includes the shop's CRS number.

The analog +L and +R outputs come from the CDI, not from the nav device that is driving the CDI. At least that's the way it's wired in our airplane.

No, a garmin 430 cannot legally drive any arbitrary heading indicator. It can only interface with units for which a specific drawing exists in the installation manual. Given all the thrash in this thread, I actually dug into the installation manual for the "Brittain Flight Control Installation Instructions 402-731-504 for B-5 System, Nav Flight II System, LSA-4 System, LSA-5 System, LSA-6 System". This is the governing document for the autopilots in question. Let's see what it has to say: First, from section 1.2: All phases of this installation can be accomplished by a qualified A&P mechanic with the exception of the connections to the existing omni system. These connections and associated checkout must be accomplished by qualified radio technicians. So the OEM's installation manual specifically requires a radio technician for omni connections, not just any old A&P/IA. Next, from the "Electrical Schematic", Note 1: Hook-up to omni indicator is across left-right meter terminals for compatibility with specified VOR/ILS makes see sht 21 Sheet 21 turns out to list a bunch of specific CDIs the Brittain units are compatible with. So no, the installation manual doesn't actually allow interfacing to "any" CDI on the basis of an electrical interface spec; it allows interfacing to a specific list of CDIs. In other words, I think I was wrong to state that the Brittain can be legally interfaced to any CDI that provides a certain millivolt-level output. I think legally interfacing to a CDI other than those on sheet 21, requires an additional manufacturer's drawing to do so. My understanding is that Jerry provided FAA_approved drawings of this sort on request from time to time, for CDIs beyond those in the installation manual. I don't claim to understand the machinations of how the FAA was involved with these drawings, nor do I claim to understand the certification basis on which the shop that installed our GI-106 indicator connected it to the Brittain. But they signed it off on their authority as a certified repair shop. The installation manual for the autopilot doesn't provide any information at all about interfacing it to a DG with heading bug. Again, this requires a separate OEM drawing to do so. There are such drawings for specific DGs, I have one that calls out the Century G502A. Bottom line, an interface spec isn't what makes an installation legal, you need a specific drawing that references the parts in question. Jerry was working on one for the G5/GAD29B when he passed, but he did not complete it. If such a drawing is not required, he wouldn't have been going through the effort in the first place.

Me too, primarily because flying in anything other than glass smooth air generates a ton of flex cycles on the wing, some of which are on par with the loads of a hard landing. If rough landings impact sealant life, then so does turbulence.

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?

This is an interesting lesson in expectations. If the altitude hold on our Brittain maintained the selected altitude within 20' using climb rates of 50-200 fpm as shown in the OP's video, I'd consider it to be doing a fantastic job - much better than expected. For us, it's a pretty good day when it holds altitude within 100' or so, which is all it promises.

Sure, but we're talking about certification standards, not practical strategy. The original conversational offshoot was about when a certified rate-of-turn indicator is legally required, and whether or not various electronic displays are certified as primary rate-of-turn indicators for this purpose. A bit of searching around suggests to me that a pair of GI-275s are legally certified to replace the entire steam gauge 6-pack. But I couldn't actually find the installation manual, so don't quote me on it. Those same searches turn up posts that say actually getting rid of your steam gauge ASI, ALT, etc. may not necessarily be a good idea. Setting aside questions of redundancy, some people feel the size of the instrument isn't kind enough to aging eyes to be a practical replacement for every individual steam gauge. Probably not an issue if you can quickly and easily read 14pt type at 2-3 ft, but not everyone can.

Yeah... sorta. A student-oriented check list does have items that aren't necessary for an experienced pilot. For example, "TAIL - INSPECT" is adequate for an owner's preflight checklist, but a student checklist typically breaks out the individual surfaces and/or linkages. That said, the preflight checklists I write just say "INSPECT" for these items, regardless of how they're broken out, so a student is going to have to ask me what exactly they're supposed to look for, until they absorb how the system they're inspecting actually works. Similarly, I write "MIXTURE - SET FOR TAKEOFF" for students (and myself), rather than spelling out how to set the mixture. To me, that's one important difference between a "Check" list and a "Do" list. A pilot using a checklist should know how to check/do things based on their systems knowledge. The checklist is just a safeguard against tactical mental lapses. Fortunately, this philosophy is synergistic with multiple goals. Avoiding prescriptive details keeps checklists short and tidy, which in turn reduces the risk of skipping items. And as a CFI, the way a student works through such a checklist gives me a pretty good idea of their level of understanding of the systems they're checking/operating.

Not only that, but both GI 275s are powered by the same source (the alternator), so one could argue the terms of AC 91-75 aren't met. It's unclear to me if/how the backup batteries in these devices play into the AC.

I had forgotten about that AC, thanks for the reminder. Note, however, that the absence of a TC still requires two certified attitude sources. Not one primary AI and a Stratus, or GTX-345 with ADHARS, or Dynon pocket panel, or whatever.

Setting aside my own mistakes (which are many), let me give a CFI perspective on this. I've watched dozens of students miss dozens of items on checklists. In every single case, I'm able to identify something about the checklist itself which contributes to the error. So one possible snarky reply to "How many times have you missed a step on the check list?" is, "Never, with a well-designed checklist". That's not really a true statement, of course. But if you're going to pooh-pooh checklists, pointing out the foibles of a poorly-designed one is kind of a strawman argument. I actually wrote a short treatise on checklist design for a CFI candidate recently, pasted below for your consideration. First, good checklists are audience-specific: e.g. items that are helpful to a renter student pilot are distracting to an experienced owner, and vice-versa. One-size-fits-all would be simpler, and I used to think I could teach new student pilots to just grow into the kind of lightweight, streamlined checklist owners prefer. But experience has taught me differently, and given me an appreciation for the compromises made by people who write factory POH checklists. So... the checklist I give to a pre-solo student for a Cessna will work well for them, but be totally bloated for a Cessna owner; but that's fine - there isn't going to be a single checklist that works best for everyone. As an example, my normal procedures checklist for students has an item for "Taxi to Departure Runway". This is a stupidly obvious action for anyone with even a few flights under their belt, and I didn't have it there initially. But I've had no less than three different greenhorn students try to start performing pre-takeoff and runup checks while idling on the ramp, because they lack the context and experience to understand/remember that those checks are done from the run-up area. Adding an item for taxi provides an obvious, helpful separator. Second, while my student checklist is geared toward students, it still avoids detailed, prescriptive actions. e.g. it says, "Prime as needed", rather than, "Prime 3 strokes in cold weather, 1-2 strokes in warm weather, not at all if engine was recently shut down". This makes the checklist more compact, which helps avoid skipping things (see below). But it also forces students to learn the nuances of and purposes behind various actions, rather than performing them mindlessly. To put it in FAA terms, I am trying to ensure they quickly move from the rote level of learning, through understanding, to application. The end goal is for them to use checklists as actual *check* lists, rather than *do* lists. Failing to understand this is a mistake I made when I first started creating custom checklists, and that I see repeated by others - especially mid-time pilots transitioning to new aircraft. It's tempting to fill your custom checklists full of prescriptive details, but doing so winds up creating more problems than it solves. Finally, the most serious and most common checklist mistake I see students (and experienced pilots) make, is simply skipping an item outright, without realizing they've done so. Sometimes it's just an inexplicable brain fart (myself included). But I've observed a couple of specific issues caused by the design of the checklist itself, and my checklists try to avoid those: 1) Adjacent items that look almost the same are prone to getting skipped. Consider a checklist that says: Lighting - ON Headsets - ON Avionics - ON ... vs. one that says: Lights - AS DESIRED Headsets - ON Avionics - ALL ON At first glance it seems like there's no meaningful difference between these, but each line of the lower one is distinctly, visually different. Whether you're using your finger or your eyeballs or both to track to the next item, you're more likely to skip an item in the first case. This is analogous to how some old airplanes have switches that all look alike, while newer ones have distinctive shapes for landing gear, flaps, etc. Some of the wording in my checklists is designed to provide this sort of visual distinction. 2) You can teach students to use a finger or thumb as a checklist place holder to avoid skipping items, but only if the checklist mechanically supports doing so. A few checklist operations require both hands, so there is no perfect solution. But you can't thumb-track the checklist at all, if it's a big, multi-page and/or multi-column monstrosity. So within bounds of reason regarding eyesight, smaller is better, and that's why my checklists use a "long and skinny" format. 3) The more pages a checklist has, the longer it takes to find the section you care about (especially in an emergency); and the cardinal sin is a checklist that requires you to turn pages in the middle of a single sequence. For example, a lot of flight school 172s have laminated copies of the POH procedures pages in the map pocket, bound with a ring. The POH checklists themselves are fine, but the ring-bound "flip book" is unwieldy, and I've lost track of how many times I've seen a student skip items in the BEFORE TAKEOFF list because it spans two pages. For whatever reason, turning the page causes them to blow past items at the end of the preceding page and/or the beginning of the next page; and they'll often keep making that mistake even after multiple corrections. So again within bounds of reason regarding eyesight, smaller/fewer pages is better, and this is another reason for my "long and skinny" format. In summary, the whole point of having a checklist is to ensure every item on it gets checked, so anything you can do to minimize the chance of skipping items is valuable. The ergonomics of the checklist are at least as important - and maybe moreso - than what items you actually put on the list.

If you mean "traditional", standalone turn coordinators, sure. But to be clear, IFR flight requires a rate-of-turn indicator per 91.205 (except for a few exotic corner cases with three attitude indicators, one of which works through 360 degrees of pitch and roll). So you can't legally fly IFR unless something in your panel is certified as a primary rate-of-turn indicator. The G5 is certified as a primary rate-of-turn indicator, I'd bet at least a dollar that the GI-275 is too. VSI instrumentation is not required for any kind of flight, VFR or IFR.