Vance Harral

Roger, the conversation has multiple tangents at this point. I remain unconvinced there is any cooling/heating rate concern in a normally aspirated 4-cylinder Lycoming, in any maneuver one might fly in the course of any training or traveling flight. Prolonged glides, ATC slam dunks, commercial maneuvers, training for engine failures or emergency descents, etc. Just based on personal experience. I acknowledge the operating envelope is bigger for higher horsepower and/or turbocharged engines, that might venture into the flight levels where OAT can potentially be 40 below (on either temperature scale). I still think the concern is oversold in the environment where almost all of us bug smashers fly our piston-powered airplanes. But again, I'm in no position for anyone to lend weight to my opinions. I don't own a TSIO-anything, have a limited amount of instruction given in M20Ks, Bonanzas, etc., and have only been above FL180 in a piston airplane a couple of times.

This is an emergency approach and landing (a.k.a. simulated engine failure), Task IX.B in the commercial pilot ACS. Emergency descents (Task IX.A) are not flown at Vg, as the purpose is not to travel the farthest distance, but rather to get on the ground as soon as possible; and not necessarily on a runway (think cabin fire). The ACS requires following AFM/POH procedures, if published. Those procedures nearly always require closed throttle, full prop, and steep deck angles at relatively high speeds. I don't have a 252 manual, what does that manual prescribe for an emergency descent?

Data point: I've been letting the prop drive the engine on a fairly regular basis for decades. Most commonly during emergency descent training, as required for the commercial certificate. This is especially interesting in multi-engine training. The emergency descent in a light twin is brutal: props full forward, throttles full idle, gear down, pitch and bank for just below the gear speed (139 KIAS in a Duchess). This results in an eye-watering deck angle and a discomforting howl of air and engine noise, but it's required to meet the ACS standard. I've never flown a glider towplane, but based on watching them at one of our local airports (Pawnees and Super cubs), the profile is about the same. Counterpoint: essentially all of my experience involves 4-cylinder Lycomings. The 6-cylinder Continental in turbo Mooneys is a somewhat different design, and is certainly more expensive to overhaul. I'm in no position to advise or criticize owners of those engines.

I dissent, primarily because this a nonsensical statement. "Nicer" doesn't mean anything with respect to a machine, there is no way to measure the cost or risk of it. If you're asserting that rapid power reductions may cause immediate damage, or reduce time to overhaul, or incur higher maintenance costs, just say that. Then we can all talk about why that might or might not be true. Let's agree on that for the purposes of this discussion. But what are the potential negatives of an easy letdown independent of the engine? You've already noted one, which is difficulty complying with ATC instructions, and in the worst case that could lead to a certificate action and suspension that may or may not be more painful to you than dents in your wallet. There are other risks, ranging from life and death (difficulty deconflicting with a traffic threat), to lifestyle (you don't get your family to the bathroom quick enough and they decide they don't really want to fly around in little airplanes any more). It feels like you want to hear that super pilots always have some risk-free way to avoid large power changes. But it just ain't so. You're occasionally going to have to either make large power changes, or accept other risks in order to avoid them. Up to you to decide how those other risks stack up against a difficult-to-quantify engine maintenance risk. I recognize I'm showing my hand here, and for what it's worth, that's based on a couple of personal experiences. One is 21 years of flying an engine I own (exact same model as yours), and paying absolutely no attention whatsoever to cooling rates. Lots of power-off 180s, steep spirals, slam dunk descents from ATC, etc. Engine is currently running strong at 2500 hours and 31 years since overhaul. The other is spending much of the last year giving multi-engine instruction, during which I make the ultimate large power reduction about every other flight: shutting down an engine altogether! No catastrophic failures or early overhauls on that airplane so far. My experiences are only anecdotes, but others here have provided other anecdotes, and at some point it adds up to data.

Let's talk about "this is how I learned" for a minute, because it's really interesting. One of the topics flight instructors are taught is the Law of Primacy. Or more generally and formally, the Law of Primacy in Persuasion. Paraphrased, it says that when debatable subjects are discussed (e.g. shock cooling, prop driving the engine, lean of peak ops), what your hear first is "sticky" in a way that is difficult to overcome in subsequent learning, no matter how much evidence is presented to the contrary. So I'm completely sympathetic to your feelings about "this is how I learned". But it's so important for all of us in this game to remember a few critical things: Flight instructors can be wrong, particularly on debatable subjects (I'm a CFI, consider me exhibit number one - I've been wrong a lot!) Technology and understanding changes over time. Data is more important than opinions. Respectfully suggest you try to let go of what you were taught when you were introduced to complex airplanes, and form a fresh opinion based on instrumentation and data. If you draw the same conclusion you were originally taught, you can feel reasonably good it's an informed opinion, rather than just what you happened to hear first. Others here have already pointed out where you might get data: CHTs from your own airplane on engine shutdown, and maintenance stories from skydiving operators, glider towplanes, and light twins used for multiengine training (the multi-engine rating requires an actual shutdown of an engine in flight, so training airplanes cage one powerplant about every other flight).

The question is too vague to provide meaningful advice. What are you hoping to achieve by forming a single ownership LLC to operate the aircraft?

That was @gsxrpilot, who no longer participates here. I'm friends with Paul, see him frequently. He sold his 252 earlier this year, but as far as I know there were never any ill effects from his trips to Burning Man in it. He did wash it carefully after each trip. As with any soft field, investigation of conditions on the day of landing is important. A beach or playa that's fine one day may be inadvisable on another.

About the only antidote I've found for this is the IFR XC flight in the aeronautical experience requirements for the instrument rating. I had a great one with a student this weekend in which all kinds of real-world ambiguity was dealt with: departure procedures, negotiating amendments to enroute and approach clearances, actually allowing the student to miss radio calls when I could safely do so, etc. I'm convinced that newly-mined IR pilots (including myself back in the day) would be in much better shape if they actually had to fly three or four such flights in pursuit of the rating, rather than only one. But that's an expensive proposition both in dollars and time. So like most instrument instructors, I wind up spending a lot of time with my IR students flying the same small set of approaches at nearby airports, often without actually filing IFR due to time constraints. I don't feel great about it. Simulators can help a little - I try to get my IR students a few sessions in our Redbird AATD that involve unfamiliar airports, and cross-country flights in which we fast-forward through the enroute portion. But in the end, I just have to explain to them that the training environment is inherently disposed toward glossing over some things that will come up in real-world IFR flying.

Yet another configuration setting that might benefit from standardization. If I was in charge (which I'm definitely not), all traffic systems would have a fixed filter that is based on minutes to convergence. Nothing more than 5 minutes away would ever be shown, under any circumstances. The boxes have enough information about relative closure rates to implement this already, but the filters are currently based on distance rather than time, and the distances and filter are all completely configurable by each user.

Ah, good that you bring this up. While this sort of hybrid navigation approach is cool when performed properly, it's also a recipe for instrument students to simply not tune the ILS/VOR at all. This happened on a training flight day before yesterday. The student clicked right though the pop-up about the GPS approach being "for situational awareness only", and simply never tuned the VOR for the approach at all, on either radio. Some navigators can auto-switch to the ground-based navaid, but even in those that are capable, whether it does so or not is actually a configuration setting that varies from airplane to airplane. Again - a problem of UI changes and lack of standardization. These days, I teach my instrument students that one should have a constant, low-level paranoia about nav radios. In addition to periodically checking things like fuel remaining, engine status, one should also be regularly questioning what source is driving the HSI, what leg of the flight plan is active, and what mode the autopilot is in. RMIs to both ground-based navaids and GPS waypoints can be very useful, but they're another thing to teach that just wasn't really available in GA for most of instrument flying history. Furthermore, whether an RMI is displayed or not is yet another configuration/preference setting.

My anecdotal observations are the same as you've read about elsewhere. But to put them in my own words: No more effort required to obtain basic competence in a specific aircraft that has dual G5s and a GNS/GTN radio or similar, vs. steam. Specifically, these "modern" avionics aren't making it harder for newbie pilots to keep the greasy side down and navigate to a nearby airport under VFR conditions for a $100 hamburger; and students are no more intimidated by seeing them in the cockpit the first time than in the old days. Not surprising given the dominance of modern electronics in our everyday lives. Standardization is a problem for renters and instructors, with each new product changing the UI in non-trivial ways from prior products. In 1990, the most sophisticated thing you'd likely find on a NAV/COM was a flip-flop button. Times are wildly different now. Recall that one of our biggest advocates for high-end avionics - the honorable @donkaye, MCFI - frequently mentions how he brings his personal portable avionics with him on training flights to "normalize" the environment. That's completely understandable and not a criticism, but it also points to a training challenge. Because of (2), there is more sensitivity by individual pilots to the individual aircraft they prefer to rent than I recall being previously true in rental environments. We have a pair of 172s at our local flight school that differ from each other only in that one is equipped with a GTN650 and another with a GNS430. The underlying logic in the boxes is the same but the UI is different, and pilots are understandably more intimidated by this than in the old days when the difference would have been a KX-155 vs. a KX-170. As a result, when airplane X goes down for maintenance, students are somewhat more likely to cancel instead of switching to airplane Y. That has a small impact on training, so I'd say it results in more effort for trainees, but only for indirect reasons of scheduling. This isn't an issue at a giant part 141 school with a fleet of identically-equipped aircraft, but that's not the environment I operate in. Teaching GPS nav is easy because essentially everyone comes to the table with positive transference from GPS guidance on their phone. There was no such analog in the 1980s for pilots trying to master VOR and ADF navigation, so that's gotten better. Definitely less effort to teach primary VFR radio nav. Teaching secondary radio nav seems harder because there's no positive transference (a lot of newbie pilots have never even tuned a frequency on a car radio). I'm not sure this is significantly different from reluctance to learn secondary nav in other eras, though. I wasn't excited about learning how to fly ADF approaches in 2004, though I eventually came to appreciate them. I'm sure the same was true of VOR vs. 4-course range. Moving beyond the basics, "mastery" of an avionics stack is definitely more difficult now. Mostly this is because there's more capability, e.g. you can't fly a VNAV profile with a KX-170 and a Brittain autopilot, so VNAV just wasn't a thing to master back in the day. But see the next list item below about "mode confusion". Anyway, a great viewpoint on this sort of thing is to start with this is @midlifeflyer's list of "GPS tasks pilots don't know how to do". He's correct that most pilots don't know how to do the things on the list. They wouldn't have had to back in the day. Note that many of them involve understanding how to make a GPS navigator work more like a VOR, which is a thing we may wish wasn't necessary, but is sometimes important to fly IFR in a system with a lot of historical inertia. Finally, and perhaps most importantly, the multi-functionality of MFDs and all-in-one com/nav/gps/transponder devices is a distraction that I'd like to see go away. One of the biggest barriers to avionics mastery is getting pilots to be comfortable when their displays are in a different mode than they're used to: different pages on an MFD, reversionary modes on a PFD, not to mention the "all in one" ness of a sophisticated EFB such as Foreflight. Anxiety about this is entirely understandable - one is nervous that you won't be able to get your gizmo back to the mode you're used to. But LCD displays are so cheap and ubiquitous now that it would be better if we had a dozen, small, independent displays with no mode settings, vs. the typical setup of a small handful of large displays that do "everything" in various modes. I'm hopeful this will change in the future (for cars as well as airplanes). On that last point, a great example of it from my personal experience involves VOR navigation. I can eventually convince primary students they have to understand VORs - at least for their check ride - even though I know they don't really want to and hope to never use them. But I have scant luck convincing them to use the #2 NAV radio and its mechanical CDI to do so. You'd think it would be an easy sell. The steps are just: dial frequency, press audio panel button to ident, turn CDI knob. But for whatever reason, most of them think it's "better" to click a mode knob/button to set the #1 GPS/NAV/COM to VLOC mode, click another dial or button to select nav frequency tuning, wait for the unit to auto-identify the frequency (made more complicated on the GTN navigators by the fact they display the identifier from their database before they display an auto-morse-code ident); then click the menu button on their G5 HSI, roll over to OBS selection, dial a course, then back out of the menu mode. All this so they can get green needles on an LCD display rather than use the mechanical CDI. I never criticize this, as it's part of "mastering" the avionics. But it takes some effort not to visually roll my eyes or make a snarky comment, especially when they get all screwed up halfway through the process.

Well, that's an interesting question. Thanks for asking it. I do feel some responsibility as a flight instructor to positively influence safety for the pilot population as a whole. But I'm not impractical about it. There certainly can be products and technologies that make you better and/or safer, but not me; and vice versa. I'm not out to ban or even criticize them just because they doesn't help everyone equally. I also understand your argument that maybe certain technologies benefit only the cream of the pilot crop - which includes us, natch - with our numbers being so small that the overall needles don't move even though the improvement for a special group is very real. But I think if you're being honest with yourself, you have to consider a couple of other possibilities, that are frankly more likely. The first is the possibility you only think something makes you safer when it really doesn't. I observe this pretty regularly instructing a gen-pop pilot clientele: over-dependence on iPads, comfort in backup instrumentation they've never trained with, reliance on cliches like "speed is life", and "the only time you have too much fuel is when you're on fire", etc. There's no question folks using high end technology feel more safe with it, and that has some benefits independent of actual safety. But when I can muster the energy to debate, I find a lot confirmation bias about safety - just brute force statements that this or that gizmo is "obviously" safer. And I get that - it's just human nature. People who spend a lot of money on high-end avionics (or brand new cars or home security systems, etc.) nearly always remain convinced it made them safer. But since it would be very painful to admit the investment might have been worthless, almost none of them are really open to external evaluation of this thesis. Like you - they're simply not persuaded by statistics (or anything else). I'm not immune to this myself, of course. The avionics I have in my airplane surely must be the absolute sweet spot of capability and safety vs. cost. The second issue is more complicated, but worth raising. It's the possibility that even if you're actually safer by yourself with certain equipment, others are inappropriately emboldened by it to do things that make them more risk to you. e.g. a pilot with inadequate training and/or situational awareness showing up in your IFR cloud bank or busy traffic pattern, who would not have otherwise been there. The canonical example of this is the pilot who is not instrument proficient (I care not whether they are "legal") inappropriately relying on an autopilot to get them through the clouds. As an active instructor who doesn't necessarily focus on Mooney-specific training, I observe a certain degree of technology mis-use on a pretty regular basis. I'm sure that experience colors my thinking about avionics, and creates bias. But the only way I know of to combat my own bias is to look for statistically significant changes in the accident data (not year-to-year blips on counts so small as to be meaningless, such as AOPA sometimes touts). I'm just not seeing anything meaningful there. And I think it's likely because technology just doesn't help as much as we want to think it does. So I'm sympathetic to questions like the one in this thread about what's really needed for a particular mission - high-end avionics for IFR, turbochargers for mountain flying, and so forth. In summary, I guess I'd say yeah, I'm not very interested in safety systems and technologies that can't move the needle on overall accident statistics, and I'll likely continue to be a skeptic when that's the case. But I'm just some guy on the internet, certainly not the arbiter of what others should put in their cockpit. To that end... Me too. But the value of debate is not in changing someone's point of view - just in getting them to think more deeply about it. I'm sure anyone reading my post here is smart enough to draw reasonable conclusions and make reasonable choices. I like to think I'm helping them do so.

But... the four weasel words at the end of your sentence are the crux of the matter. It is not only possible, but in fact common, for the mis-use of technology to wind up causing more trouble than the original problem the technology was supposed to fix. A case where I notice this commonly in modern-day GA ops is the mis-use of traffic displays. I really wish the FAA and/or industry training providers would provide better guidance on how to actually use them. There is a prevalent, dangerous assumption in our community that proper use of traffic displays is "obvious", but I've seen clients do some truly moronic things in response to something they saw (or think they saw) on an iPad. I have opinions about this, of course, but my opinions and actions might be moronic as well - who knows? Meanwhile, we're 5 years into mandatory ADS-B out in rule airspace, and I can find absolutely no evidence in the McSpadden report or other sources that the midair collision rate has changed at all.

If it's "really hard to show statistically", that means it's not much of an actual safety improvement in practice. On this we can agree. I especially appreciate @AndreiC's comment that in a universe of finite "safety dollars", the bias should be toward proficiency with equipment you already have, rather than an equipment upgrade that is dubiously advertised as providing inherently more safety.

Agree with @kortopates that you're over-simplifying a complex question, though the conclusions I draw are somewhat different than his. Within the realm of my experience (lots of steam and glass in piston aircraft, very little turboprop and zero jet time), I just don't care much whether information is displayed as pixels on a screen driven by a digital computer, or plastic and metal needles and rings driven by analog op-amps. i.e. I don't care about "glass", i.e. I agree with you. But if you start looking at reliability and redundancy, things get more complicated as Paul notes. One aspect of this is the power source, which is typically singular for a vacuum-powered instrument (one vacuum pump), but typically triple redundant for a glass instrument (alternator + ship's battery + internal backup battery). In this respect, glass is better than steam not because of pixels, but because you'd need a second steam instrument and/or a standby vacuum system to achieve the same level of power backup with steam gauges. If you actually have that power redundancy in your steam gauge setup, then I'm back to not caring. But standby vacuum and/or a spare electric-powered mechanical AI is not very common in the airplanes I fly. It's more expensive and more invasive to install than a second G5 or GI-275, and therefore the market dynamics just make it unlikely to be there. Another aspect is how different your scan has to be when primary attitude fails. If, say, a G5 ADI fails, and you have a G5 HSI right below it, the HSI can be reverted to an ADI and the location where you look for attitude information doesn't change much. However, the loss of the HSI means navigation "needles" are only available on the EFIS, which most people aren't used to looking at. Backup mechanical AIs are usually located somewhere outside the basic 6-pack layout, so the scan changes a bit more, but the needles on your vintage CDI/HSI are right where they've always been. The worst case, arguably, is big-screen PFD/MFDs, where you now have to look all the way on the other side of the panel for backup. It's hard to say which of these is the most distracting, but see my note about training below. Regarding the reliability of the instruments themselves, I'm a bit of a contrarian about this idea of replacing "unreliable" vacuum pumps with "reliable" electronics. First, I work in the electronics and software industry and I know all kinds of ways a supposedly reliable electronic system can fail, so this gives me a sense of paranoia others lack. I'm not sure why people assume electronic instruments won't fail, and I've never actually seen statistical data on it. Anecdotally, I'll point out that I fly half a dozen heavily used flight school airplanes with dual G5 setups, and I've seen as many failures in these systems as I've seen failed vacuum pumps in steam gauge panels. The failures mostly have to do with heading data on the G5 briefly going yellow due to what I assume is vibration-induced inaccuracy, but in one case the magnetometer in the wing came loose, rendering heading data completely incorrect despite the displayed heading not going yellow or red. it's also worth pointing out that the wires which connect the output of a GPS/NAV radio to an indicator are equally likely to break or burn up, regardless of whether that indicator is steam or glass. But I think the real bottom line is this: anything that changes the critical information displayed or the place it's shown, is extraordinarily distracting if you've never seen it before. The only fix for this is training for likely failures. People that fly instruments in steam gauge airplanes are somewhat likely to seek out "classic partial panel" training using needle/ball/airspeed to keep the greasy side down, and if you actually practice this intensively, it just doesn't seem that hard to me, though I admit I've never had a real vacuum instrument failure in actual IMC. Conversely, people that fly glass panels seem less likely to train for various failure modes, because they seem more sure that failures are a theoretical bogeyman rather than a real possibility. They also seem to assume things like automatic reversion of an HSI to an ADI, or the use of an iPad to get attitude information will be inherently manageable, and underestimate just how distracting it actually is the first time. To that end, I won't sign off someone for an instrument ride without a couple of hours flying in some sort of non-standard redundant mode, be it steam or glass-based. Pilots that get this kind of training during pursuit of the rating, and who keep it up in safety pilot sessions and IPCs, tend to do well, regardless of steam vs. glass. Pilots that don't, don't.

Understood and agreed. But I'm confident the likelihood of being affected by such testing is less (or at most the same) as the likelihood of you having a problem with your own specific equipment, as discussed. Therefore, the presence of these NOTAMs doesn't change flight planning (or avionics planning). If you fly with GPS at all, you're accepting a small possibility of a GPS outage, regardless of whether government testing is happening, and therefore regardless of NOTAM or no NOTAM. Sidetrack: This sort of thing is the main reason why the NOTAM system is fundamentally broken and is increasingly being ignored, even though we all know it's "wrong" to do so. There is no requirement for a NOTAM to rise to any particular threshold of risk, so the system has become more about liability protection for people on the ground than about risk management for pilots. Two days ago, I flew from Amarillo to Denver with a student. I just re-studied the briefing. It contains 6 GPS testing NOTAMs, 16 UAS NOTAMs, and 37 NOTAMs for unlit towers (tower operators never fix lights any more, as that actually costs money, issuing a NOTAM is free). Half of the people reading this are saying to themselves, "Wow, Vance is actually still checking NOTAMs, what a nerd!" Lest you think this is some sort of anti- (or pro-) GPS rant, I note that the same briefing contains 36 NOTAMs about ground-based NAVAIDs being either unserviceable or unmonitored: VORs, DMEs, etc. The unmonitored devices are nearly always still working, but it's up to pilots to determine so on their own rather than expecting help from "the system". The ones marked unserviceable are a lot less likely to be functional, but sometimes they still are. So anyone doing real-word flying has to develop filters to sort the NOTAM wheat from the chaff, e.g. to find that runway closure that's hidden in an avalanche of junk NOTAMs. The EFB companies have boldly taken on the task of trying to provide situation-specific NOTAM data where critical (e.g. pop-up when you look at an approach plate), and I very much appreciate it. But the governing body apparently doesn't understand or doesn't care about the problem. To quote Robert Sumwalt of the NTSB, "NOTAMs are just a pile of garbage".

Yahbut... these "GPS testing" NOTAMs essentially never result in actual outages, and people who fly regularly see them as NOTAM noise to be ignored. I know that sounds sketchy, but people who fly nationwide on a regular basis know GPS testing NOTAMs are present essentially all the time. They remind me of UAS NOTAMs, which is to say that yes, something is there, and yes there are corner cases where the thing could cause you to have a bad day; but you can't change your actual operations as a result of the NOTAM except to not fly at all. The likelihood of your aircraft being unable to navigate via GPS is almost exactly the same whether a GPS testing NOTAM is present or not, just like the likelihood of you having a mid-air collision with a small object is the same regardless of whether there is a UAS NOTAM in your area of operation.

Having flown a variety of piston-powered equipment, I'll opine that big displays are more about entertainment/cool factor, and resale value, than capability. I wouldn't hesitate to fly a "micro EFIS" system (dual G5s, Aspen, whatever) in any situation where I'd fly with "TV screens" (Dynon, G500, G3X, etc.) And that's coming from a guy old enough to need corrective lenses to see the small stuff. You might also consider that people who have upgraded more than once over the last 20 years seem to have an easier time upgrading individual small displays than big PFD/MFD setups. Hard to say if that will be true in the next 20 years, though. But it's certainly OK to buy stuff just because it's cool. If big displays are important to you (or you think they'll be a better resale investment), more power to you.

At the risk of being "that guy", I don't understand why these claims are always exaggerated. RC-Allen vacuum powered gyros weigh 2.7 lbs and a Rapco vacuum pump specs out at 4.75. The PVC hoses (usually) and clamps that connect the stuff weigh about 1lb max, so total of about 11 lbs. That gets replaced with dual G5s and a GAD29 plus wiring plus an engine accessory cover plate that adds up to about 3 lbs, so the delta is less than 10 lbs. Take one less gallon of fuel or spend a few weeks skipping hamburgers and hitting the gym, and it's break even. There are valid reasons to remove the vacuum system in an upgrade, but massive weight savings isn't one of them.

No, an "omni indicator" doesn't have anything to do with heading in this context. You're asking about autopilot heading functionality, which is independent of autopilot nav tracking functionality. A Brittain "AccuTrak" unit is not capable of following a heading from a DG bug or any other heading source, it only follows courses. However, a Brittain "AccuFlite" unit is capable of following a heading, and some airplanes have both the AccuTrack and the AccuFlite, with the latter interfaced to a DG or HSI with heading bug. There are other Brittain autopilots where a single unit performs both heading and nav tracking (e.g. the B-5 in our airplane), but the AccuTrack/AccuFlite are separate units. I don't know much about the AccuFlite unit. In particular, I don't know what type of signal the AccuFlite wants to see from the DG/HSI. I vaguely recall there are a couple of different "vintage" signal protcols for heading - one DC-based and one AC-based. Maybe, but I wouldn't count on it without further research. Again, I think some heading interfaces use AC signaling.

Nav tracking in Brittain autopilots relies on a +/- 5V DC differential input that signals course deviation. The installation manual specifies this input should be driven by the output of an "omni indicator". In the era when Brittain was still supporting products, that phrase was generally understood to be a CDI or HSI that produced an analog output signal indicating deviation. For example, in the King KI-208/209 installation manual it's the "lateral deviation" signal output by the unit. Modern (and not-so-modern) GPS navigators typically implement a +/- 5V DC analog lateral course deviation output (note: you may have to enable this output in the configuration settings). The Garmin 175 has such an output. It is designed to drive older HSI/CDI instruments that rely on analog inputs, not autopilots. But it coincidentally happens to be the same signal the Brittain autopilot needs for nav tracking. The electrical engineer in me thinks one should probably install some sort of isolator/repeater if you connect it this way, since Garmin never tested it with the load presented by a Brittain autopilot. But in practice, it's probably fine. So... If your Garmin 155 is presently driving an "omni indicator" (CDI or HSI), which you plan to retain in your Garmin 175 installation, and which implements analog deviation outputs that are connected to your autopilot, then you wouldn't have to change any of the connections to the autopilot. You'd only have to interface the 175 to your existing CDI/HSI, and there is essentially no question about the legality of such an installation. If your Garmin 155 has its analog outputs wired directly to the autopilot rather than through a CDI, you'll be able to do the same with the 175, and its even easier than connecting via a CDI/HSI. But whether this new installation (and your existing installation) are "legal" depends on whether the person doing the work interprets the connectivity diagrams in the Brittain and Garmin manuals as restrictive, or merely representational. There has been some arguing about this in the past on Mooneyspace and elsewhere, but all of it (including posts by me) is bloviation. The only person whose opinion matters in practice, is your installer's I bring it up only because you might want to ask your installer about this as part of the investigation process, before you put down a deposit. You don't want to wind up with your airplane in their shop, torn up and halfway through the work, and only then be told, "Uh, we can't legally hook up to your autopilot". Sadly, you can't necessarily rely on the shop to study this kind of issue up front. A lot of avionics shops don't really study the work of a particular installation until they actually have the airplane apart.

About 18 months ago, some nut job in the town where our airport is located used a flight tracking site to identify our airplane as the one that was "shooting energy beams into his house". He drove to the airport and started yelling threats at my partner while he was filling up the airplane at the self-serve pump, which can be seen through the fence of the public parking lot outside the FBO. Cops were called, but they let everyone go due to complexities I won't go into here. The guy took photos of our airplane and my partner, and subsequently began a campaign of social media ire in which he offered a cash reward for identifying information about the pilot(s). His social media acquaintances dug into the ownership info, and it eventually led to pictures of my airplane partner, as well as pictures of my house, being posted on his Facebook page, with accompanying threatening commentary. My partner never actually flew over his house, but of course that didn't matter. The person in question is not what you'd call a model citizen, a cursory search turned up a conviction for menacing with a firearm. Needless to say, this was disconcerting. We filed for a TRO, which was promptly granted, but it required time off work and paying the county sheriff to serve the notice. Making that TRO permanent required we actually meet the SOB in a courtroom. A protective order doesn't provide any actual protection, of course, just justification to arrest and try someone for violating it. I had to explain all this to my wife and daughter, which they understandably weren't thrilled about, and we didn't allow anyone to be home by themselves for several months. I purchased security cameras for my home, informed my town police, etc. A few months later, the guy called the flight school where I give instruction, and although he was only calling by coincidence rather than to harass me personally, it met the letter of the law with respect to violating the order. So I reported it, and a warrant was issued for his arrest. But after one attempt to pick him up (the cops knocked on his door, he didn't answer), nothing further was done. I understand why - there are tons of outstanding warrants on various individuals in any given locality, and the cops have to prioritize their time and effort. They're not going to carry out a Waco-style raid on one crazy guy who violated a PRO on a couple of other grown-ass men. Nothing is going to happen to this guy until/unless he gets pulled over for speeding or whatever. It's been long enough without incident that I don't spend time worrying about this any more. The guy has moved on to other craziness (in some cases other pilots in other airplanes). But it's been an ordeal I wouldn't wish on others, and illustrates why making aircraft data completely public is problematic, even if you think "tracking flights is not a problem." When I tell this story to people who aren't pilots, I ask them to think how they'd feel if anyone they happened to drive by in their car on a public street could look up their name and address from their license plate number. Sometimes the light bulb clicks on in their head, but in most cases I think they still believe aircraft movement and ownership information should be public.

One of our local flight schools seem to think static wicks are safety devices that protect pilots from "energy surges": https://www.facebook.com/share/v/16MF2QwcbV/

I think one thing poorly understood in these debates is how likely your airplane is to lose GPS signal, vs. availability of the GPS network overall. The reliability of GPS as a system is very good, legitimate stories about jamming and spoofing not withstanding. There are many redundant satellites, the receivers have excellent discrimination, and overall hardware and software availability is very reliable. Widespread outages are essentially unheard of - any such thing would immediately make national news as shipping deliveries were disrupted, Uber drivers didn't arrive, etc. Because of this, there's an understandable tendency to think a GPS-nav-only airplane isn't a big deal. But GPS nav failure in an individual airplane is a different analysis. Antennas and cabling break, faulty COM radios generate harmonics that disrupt GPS receivers, etc. You also get the occasional, rogue interference in a small local area (sometimes near your airport) from some moron trying to disrupt tracking by his employer or parole officer, or whatever. I won't say these sorts of problems are frequent, but they're not unheard of. Most of us that have used panel-mounted GPS in a variety of airplanes for many years have seen an incident or two. When it happens, you can ask ATC or the CTAF or whoever, "Hey, what's going on with GPS?", but all you get is the verbal equivalent of a shoulder shrug, and reports that it's working for others. That's a pretty lonely feeling in VMC, can't imagine what it would feel like in IMC.

Just to update this story, we ordered and received the LW-15473 pump, and our mechanic installed it today. Ground ops are normal, fuel pressure gauge shows 25 psi with just the engine driven pump, increases to about 27 with the boost pump on, all looks good. Test flight will have to wait for better weather, but I don't anticipate any problems. At the (small) risk of affecting my core trade-in, I disassembled the old pump to look at the diaphragms. Comments from @cliffy and @N201MKTurbo seem spot on - it would not be difficult to self-overhaul the pump if we could get a kit to do so, but the combination of market and paperwork makes that a hassle. Anyway, while I was not able to actually find a breach in the main diaphragm, it was clearly on its last legs - the outer edges of the diaphragm were brittle, with a consistency more like cardboard than rubber. Lousy piece of junk only lasted 31 years, guess they just don't make things like they used to.