Vance Harral

The wires aren't soldered into the connector, they use pins which are (somewhat) removable. And I don't think Garmin ships pre-built harnesses for navigator/CDI connections. They are generally built at the avionics shop, since the distance between the navigator box and the CDI varies from airplane to airplane. The connection from the navigator to the CDI (or to a GAD29 in the case of a G5 HSI) is just a bunch of individual small-gauge wires, terminated with pins that "click" into the connectors you get from Garmin. It is definitely possible to get an individual pair of wires associated with a single differential signal backwards. You can probably guess how I know this.

The service manual for the 1976 M20F says battery voltage in a normally operating system at 80F should be 13.8 to 14.8, see below. This assumes you have the original alternator and voltage regulator, which you may not. Another catch is that you're probably not going to wire your voltmeter directly to the battery or alternator output terminals, but somewhere else in the electrical system. Depending on where and how it's tapped, there may be losses in the system that make the "normal" voltage seen on the meter slightly different than the spec'd voltage in the service manual. If you want an in-the-field data point, we've had an AV-17 voice annunciator in our 1976 M20Ffor about a decade. It has non-adjustable voltage warnings that the manual says trigger at 13.0 and 15.1V for low/high points, which is exactly what @A64Pilot suggests above. We've never had an overvoltage warning, even during an ill-advised operation once when the battery was nearly dead and we accepted the risk of a very high charge rate once we got the engine started. Low voltage warnings trigger as expected, basically any time we turn on the voice annunciator before engine start. I don't think there is any perfect answer to your question, again because behavior varies depending on where you mount the meter. But 13/15 for low/high seems very reasonable to me.

Roughly 80% of all the pilots I've flown with who have GTN/GNS navigators. Most of them have never had the startup test sequence explained to them, and they don't understand what it's intended to verify. They also don't understand why they should care about it, because they don't understand that the connectivity between the navigator and the CDI is just a pedestrian set of relatively vulnerable, small wires, that bounce around and fatigue with every bump of turbulence. Some installations are more robust than others, of course, and I've never actually seen a GTN/GNS-connected CDI go belly up in the middle of a flight. I'm probably extra sensitive to it because I wired my own. It just seems more sketchy when you're crimping the pins and routing the wires yourself; and thinking, "Really? That's it?"

I'm not sure exactly what you're asking about. The thing right below the landing gear switch is just a cheap, 3-up kitchen timer velcro'd to the panel. The thing that says "0" with the green buttons is a Sensorcon carbon monoxide detector, also velcro'd to the panel. Lots of us here on Mooneyspace have them, thanks to bold work by @DanM20C. If you're asking what my hand is on, that's the throttle in my airplane. I do understand it may look quite foreign to most Mooney drivers, who are crippled with pedestrian push/pull engine controls, being not fortunate enough to enjoy the superior throttle quadrant that was installed in select, 1970s era Mooneys.

That's appreciated, but mostly I'm glad it turned out to be something simple. To give credit where it's due, Pete Mc was the first to suggest it.

Would you be in favor of the FAA mandating $500 worth of training with a CFI on maneuvering flight instead? That would buy a lot more safety than requiring any kind of additional equipment. It's right there in the Nall (now Richard McSpadden) report. This is my beef with the topic being discussed. I don't know that I'd use the phrase "freaking out". I'm not anti-TIS-B or anti-radio. But the interest, emphasis, and money spent on midair avoidance is grossly disproportionate to the threat of what's actually killing pilots. If you have X dollars to spend on "safety", there is no rational argument for spending it on anything other than additional practice and training. That's not to say you shouldn't buy equipment for comfort, convenience, or fun, of course. Just don't lie to yourself that you're buying safety.

Maybe it'll amuse you to explain that I teach students it's a mock dogfight, at least as close as you'll get as a civilian. I was never a fighter jock like you, but "Lose sight, lose the fight" and all that - there's a lot to be said for turning toward a target rather than away from it. Not only are you more likely to see them, but in most cases, if you point your airplane at where a threat is right now, it actually increases separation by the time you get to where they were. More controversially, I can often get effective results by rocking my wings without actually changing my flight path at all. Usually this goads the other guy into doing something, and I can watch the threat actively fly away from me. The point is not to be a bully, but a little "showing off" in the name of increased visibility isn't a necessarily a bad thing. Both of these strategies are counter-intuitive. You need to think about it a lot to understand why they're effective collision avoidance. Things like this are taught to ATC controllers, radar intercept officers, and fighter jocks; but it hasn't yet made it into the Private Pilot curriculum.

If the conversation is going to turn back to training instead of who's an idiot, I'll play. Here are some observations I have from watching "self taught" pilots interact with their traffic systems, that bother me. Feedback is welcome, I'm happy to hear other opinions. First is understanding the difference between what is, and is not actually a threat. Pilots say things to me like, "You just don't realize how much traffic is out there, Vance. There's way more than you think!". So I ask them to show me, and they'll bring up some picture like this: It's an impressive image at first glance. Obviously hundreds of airplanes. But then I point out this picture encompasses over 2,500 cubic nautical miles of airspace (you can see both KOSH and KMSN in the picture, they're a little over 60nm apart, and there is no altitude filtering). Each individual blue arrow representing an airplane is about 4 square miles of area at this scale, as if every piston single was the size of an Imperial Star Destroyer. It paints a completely unrealistic picture of "all that traffic out there". Conclusion: scale matters. Set your traffic display to some single-digit number of miles, in accordance with your speed, such that you don't see anything at all until it's within a minute or two of closing on you (nothing under 10,000' is moving faster than 250 knots, and even a 500-knot closure rate is only 8 nm/min). Employ altitude filtering, too: if you really believe that device is giving you accurate, useful information, you certainly don't need to worry about targets depicted more than 2000' above/below you. If one does these things, there's often nothing on the display, which frees up a lot of cognitive energy for, you know, flying the airplane. Trouble is, lots of pilots I fly with have gotten to the point of developing such inherent anxiety about traffic, that if they can't see any threats to avoid on the display, they'll keep zooming out until they do. Second point: for something that's a real threat, what should you do about it? Most of the pilots I ask this say something like, "Well, I'll maneuver to avoid the threat based on what the display is showing me". What I want to hear is "I'll attempt to find the threat visually, then maneuver to avoid it if necessary". That's usually not what people say. But you know what? I can let that go. Reasonable people can disagree on this. What drives me nuts is that when I ask how they're going to maneuver, a lot of people tell me they're going to perform a maneuver that absolutely maximizes the chance of a midair. They say they'll turn "away" from the threat, by which they mean they'll make a turn that puts their belly to the target, guarantees they can't see the threat, and maximizes the time the two aircraft are in close proximity. Literally any other answer would be better: Climb. Descend. Turn toward the target so you can put your nose on their tail and pass behind. Speed up. Slow down. Just anything other than turning your belly to the target and carving a parabolic path right toward their track. My third gripe is the growing preponderance of pilots who use their traffic displays around uncontrolled airports to effectively declare themselves an ad-hoc controller, and make "suggestions" about what other airplanes should do. To be clear, I've got no problem with a radio call like, "N12345 is on the 45 to downwind for XX, planning to enter the pattern behind N54321". That's a nice feature of TIS-B. But in the metro area where I fly, I run into situations a few times a month where some yahoo is asking other airplanes (by call sign), "What are you doing?"; or making position calls on behalf of other airplanes they think have failed to made some "standard" announcement; or initiating a ten-sentence exchange of coordination with the aircraft nearest them, completely oblivious to the bandwidth they're taking up that prevents others from making critical position reports. CTAF procedures have always been challenging, but ADS-B is making those challenges worse, and I'm inclined to believe the net safety change is a wash at best. Once again, these are not theoretical problems I'm concerned "could" happen. They are actual behavior I'm observing on a regular basis. The people engaging in these behaviors aren't idiots, and the insidious thing is that they really believe they're making things safer. In some cases they lack critical thinking skills, but mostly what they lack is experience and/or instruction. It would be nice for the industry to address that. I can do my part as an instructor, but I'm just one guy, and unlikely to exert much influence on anyone who already has a pilot certificate.

Probably one thing we can agree on is that technologies work best when pilots receive training on how to use them, from informed and experienced sources, rather than being expected to figure it out on their own. I'm not claiming to be the best expert, but who is? None of the textbooks I'm familiar with (FAA and industry sources) have an in-depth treatment on TIS-B (there's actually more discussion of TCAS). In particular, there's no formal treatment of attention level and risk/reward, failure modes, appropriate response to threats, etc. The texts do say visual acquisition is the most important aspect of traffic avoidance, but that's not what pilots (and instructors) are actually prioritizing in the air, because traffic avoidance is not a specific element on any lesson plan I've ever seen. Engineering nerds and/or pilots with a lot of time, experience, and a skeptical nature reach better conclusions. But unless they're instructors, they have little influence and little incentive to correct bad behavior. I guess what bugs me most about it is the generic complaint about flight instruction in general: the bulk of flight instruction is performed by young and inexperienced pilots who haven't flown much outside their local area (not their fault), lack an in-depth understanding of the engineering principles (not their fault), and relative risk (maybe something they should know, but this isn't covered in the CFI curriculum until the first FIRC, by which point it's already too late). So they guess, based on what seems intuitive, and wind up passing on bad advice to the next cycle of pilots/instructors. The principle of primacy being what it is, it's very hard to undo these things. A more humorous, more benign example is the "Last call" radio transmission, which I think of as the illegitimate grandson of "Any traffic in the area, please advise." I can let that one go because while it doesn't help anything, it doesn't hurt much either. Poor use of traffic displays is of greater concern to me. It's not wrong to point out the problems with it, and it's no more appropriate to accuse those who do of being Luddites, than it is to accuse people who evangelize it of being idiots.

I'm not making theoretical arguments, I'm speaking of actual observations of actual pilots and where they spend their attention. All these other items you've listed don't draw attention disproportionate to the associated risk, the way traffic displays do. No one is arguing that ADS-B is bad and should be shelved. We are saying it's being mis-used. Too much time heads down, not enough time heads up. Blind maneuvering in response to screens, without actually acquiring the target visually. Anecdotal claims of "saves" that are far too frequent and common to have averted an actual collision, which just further spin up anxiety amongst the masses. And most importantly, actual problems caused by inappropriate focus: the aformentioned unusual attitude, landing accident, etc. I'm sure you feel this doesn't apply to you, because you don't misuse the tool, and that's fine - I have no reason to believe otherwise. But you seem to think it doesn't apply to most other pilots either. If we're going to talk about overall utility and education rather than just your personal operations, I think you need to listen to the instructors who are flying with a lot of different pilots about what we're seeing. There's a lot of not-so-good decision making going on out there with respect to collision avoidance. It's not theoretical.

The problem with this seemingly obvious statement is, it doesn't account for the possibility that using the tool increases risks other than the one the tool is designed to mitigate. I see this as an instructor, and generally agree with Wombat: people are so disproportionately concerned with reducing the tiny probability of a mid-air, that they are achieving a net decrease in safety because of it. Heck, right here on Mooneyspace this week, there is a thread from a brave soul who was willing to confess that his concerns about the tiny probability of a mid-air were a direct contributing factor to him crashing his airplane short of the runway threshold on a botched approach. I applaud his humility, and his willingness to share the very important lesson he learned. Only if you think the "cost" doesn't include the cost of distraction caused when the tool is used improperly. I know, I know... you only use traffic information properly, and this doesn't apply to you, of course. But I fly with dozens of pilots a year, and most of them are focusing an unreasonable amount of time and energy on traffic displays, to the detriment of other threats. I'm sure arguments about this will continue, but pretty soon we'll have Nall report data from years past 2020, after the ADS-B mandate for rule airspace is in effect. My prediction is there will not be any statistically significant difference in the number of mid-airs, measured across several years (the numbers are so small that you cannot attribute anything meaningful to a one year variance).

You are confused about what the GNS/GTN/GNX startup test does. This is common, and understandable. With respect to a traditional CDI such as in your and the OP's pictures, the startup test simply applies a voltage to the input pins of the CDI that control the lateral needle position relative to center, with a voltage that should drive the needle halfway across the display to the left side. That's all it's testing: the ability of that voltage to drive the needle left. It doesn't matter what you set the OBS knob to during the startup test sequence, it will stay in the same "half left" position regardless of the OBS setting. You appear to be under the impression that the startup test creates a situation where it simulates your position being east of a course of 150 TO a waypoint. Again, that's not what the test does. The test is much simpler: it just drives the needle halfway left across the display. More confusion here. A traditional CDI such as the Garmin GI-106 in the OP's picture and the King indicator in your picture does not transmit, receive, or display desired track (DTK). The DTK=150 value shown in the test is irrelevant in your and the OP's airplanes. It's there for more advanced indicators such as the HSI on a G5/GI275/G3X. The startup test does display an OBS value, which is the value it's reading from the OBS setting on the external CDI. If you rotate your OBS knob, you'll see the OBS value on the GNS/GTN/GTX screen change accordingly. This is good to check on startup because it verifies that OBS output from your CDI is being correctly received as an input to the GNS/GTN/GTX. Again, however, you can spin that knob all you want and the lateral needle position won't change during the startup test. I'd bet a dollar that the OP's lateral CDI pins are hooked up backwards, and no one has ever noticed, because the people operating the airplane aren't actually using it for navigation. Most of the VFR pilots I fly with these days don't even want to talk about CDIs, they just steer back and forth across the magenta line on their moving map. It irritates me a little, but I don't really have a problem with that for VFR ops. I try not to be an "old man" about it, and save the rants for IFR students.

The "Pitch On" knob enables the pitch damping system in a Brittain autopilot. It is a poor man's pitch hold device. It does not know the actual pitch attitude of the airplane because it is not connected to any kind of gyro. It is instead connected to a box which contains both a "G sensing device" (a weighted mass in the middle of a rubber sheet), as well as a calibrated leak (i.e. a VSI). The control system attempts to keep the airplane at 1G and constant vertical speed when enabled. The idea is that you manually set up the airplane for a certain power/pitch/performance state, which it would naturally hold in smooth air. In turbulent air, the airplane will oscillate around that state. The pitch hold system dampens those oscillations. In our airplane, the pitch hold system is part of the altitude hold system. In addition to the box with the G sensing device/calibrated leak, there is also a pressure chamber which is sealed when you enable altitude hold. That chamber provides a reference which the altitude hold system attempts to match against static air pressure. But the response time of that system would be too slow by itself to achieve precise altitude control. By working in concert with the pitch damping system, altitude hold is more precise, because the system immediately corrects for pitch deviations before the static pressure system indicates much change. It is a very clever system that works nicely when everything is exactly tuned, and all the static and vacuum system is very well sealed. Unfortunately, it is rather difficult to keep the system well-tuned and well-sealed. We've been fiddling off and on with it for 20 years. Ours "mostly" works. We generally know when/why it's out of tune, and what could be done to improve it. But it's a constant battle of chasing down small leaks in the system, cleaning dirty potentiometers, etc. Regarding your other questions, the Brittain B5 has its own heading knob. It relies on a remote compass in the tailcone to know the heading of the airplane. There is a procedure for calibrating the system, provided of course that the remote compass in the tailcone is actually working. In addition to heading mode, the B-5 can integrate with a nav head to provide course tracking for enroute and approach. This requires the device to be electrically connected to a CDI. As for how the B5 integrates with the PC system, they come together in the turn coordinator, which is the critical component of the PC system. A Brittain TC is connected to the vacuum system, and has a shuttle valve that routes vacuum to "left" and "right" lines when the TC indicates a turn to the right/left, respectively. Any time the TC senses a turn, the PC system turns the airplane back against the turn. In airplanes with a B5 or other Brittain autopilots, the lateral outputs of the autopilot electrically connect to the shuttle valve of the PC, such that it can move the valve to command a turn.

That's how an HSI would behave, but the indicator in the OP's picture is a CDI, not an HSI.

That's only the latest 100% increase. If you go back a few more years, they were about half of the "good" price from just two years ago. Shock disks have been on a ridiculous inflationary streak in the 20 years we've owned our Mooney, and there's no sign of it abating. It's so bad that I now consider the landing gear suspension to be a major design deficiency in our airplanes, vastly inferior to the oleo struts found on other models. We're at the point of needing to set aside thousands of dollars every 5-10 years just for landing gear suspension parts. Depending on how often you fly and how weight/climate affect your particular bird, that's several bucks an hour just for the shock disks alone. Compare that with $19.95 for a Piper oleo strut rebuild kit at Aircraft Spruce.

For what it's worth, all the localized rubber tubing in our Brittain system was confidently replaced by an A&P with appropriately-sized thick-wall PVC tubing from the PMA section of Home Depot about a decade ago, and has held up great. The "brand name" version of this stuff is Tygon; but Tygon or not, it's just PVC tubing. This was in an M20F with the DG in the panel rather than the tail cone, but essentially the same components. Note that I'm not talking about the rigid tubing that goes out to the servos, just the local, soft lines that run from the vacuum pump to the gyro, filters, and local vacuum breakers; i.e. the "black stuff" the OP refers to. The A&P in question (now retired) asserted that Tygon/thick-wall PVC was the modern standard of care for vacuum lines. I'm not sure LASAR would send you anything more "official" than that. I like the LASAR folks, but arguably not worth the time and trouble of working with them vs. a local supplier.

The EI R1 is a reasonable replacement for a mechanical tach: accurate, inexpensive, uses no mechanical cables. It is also, in my opinion, a pain in the a** to actually use. One of the flight school airplanes I teach in has this tach. It's difficult to read from the right seat in daylight, due to a combination of the way the backlight works (might be an installation error), and the LCD viewing angle. The ring of LEDs around the perimeter of the instrument are supposed to provide an analog-like "feel", but they aren't marked with actual numbers, and there are only 16 of them to cover a range in excess of 1600 RPM, so they feel useless to me - I never look at anything except the numeric display, which I feel like could have been better without the lame ring of LEDs around the perimeter of the face. Finally, you of course can't read the tach time on the instrument without powering it up, and the interface to read it requires cycling through two "pages" of display once you have more than 999 hours of tach time. This is probably less of an issue in an owner-flown aircraft, but I'd guess 90% of pilots at the flight school forget to make a note of tach time before turning off the master, and therefore must cycle the master again later to get tach time. This puts almost twice the wear on the master switch, and is a recipe for accidentally leaving the master on. If you're looking for an inexpensive tach that doesn't require a mechanical cable, I think the UMA TSO'd unit is a better choice: https://www.aircraftspruce.com/catalog/inpages/tso_tachometer.php

Not to be pompous about it, but I likely have more data points on G5 calibration than most pilots posting here. That's because I instruct at a couple of flight schools/flying clubs, where every aircraft has a dual G5 setup. Between that and instruction in owner aircraft, I've flown about a dozen airplanes in the last couple of years with G5s. Most of these airplanes have never had their G5s calibrated through a static system check, because the shops and/or the aircraft owners know the instrument is not primary for altitude. Despite @CChris's argument - which I agree with - the owners generally just don't want to pay for the calibration, and the shops don't want to try to bill for it unless explicitly requested. Here's where it gets interesting: based on these data points, I am convinced there is a consistent error in the "bad" direction of an uncalibrated G5 with respect to altitude, at least at field elevations here in the Denver metro area (generally around 5000'). Every single uncalibrated G5 I've flown with indicates higher than their certified mechanical counterpart. The difference ranges from +50 to +120 vs. the certified instrument, with not a single one of them indicating lower. This is an eye opener when/if you watch an instrument pilot shoot a practice approach down to 200' minimums using the G5 altitude, and subsequently point out they have descended to within 100' of the ground. I'm never surprised when different altimeters indicated different values, but I am surprised by the apparent net error in G5 altitude across many data points. Because of what I've seen, I've made it a standard part of my avionics instruction, and a point of particular interest in instrument instruction, to point out that not only is G5 altitude not certified primary, but that if you use altitude from an uncalibrated G5 on an instrument approach, you are quite likely to bust minimums - and not by just a few feet, but perhaps in excess of 100'. Anyway, I paid directly out of my own pocket to have the local shop calibrate the G5s in our partnership airplane, and would do so regardless of the outcome of arguments about whether it's legally required. I also won't fly low IMC in an airplane that hasn't had the calibration done. That beautiful EFIS display tends to draw the eyes of most of the pilots I fly with, and most of them keep using the G5 altitude no matter how many times I remind them it's not primary. I just let that go with folks that lack an instrument rating, but it gives me the heebie-jeebies with airplanes and pilots that are purportedly going to fly IMC. For me, that's the number one reason I recommend paying the shop extra to calibrate the non-primary G5 altimeter. I don't think doing so is being anal-retentive. I feel like it's required to correct what appears to be a consistent bias in the design of the instrument, in the "dangerous" direction.

The amount of oil your engine is spitting out is more than ours, but the pattern is similar. If it's new and has never happened before, it's worth debugging, and sounds like you've done that. But among the options of "what should I do about this", one is "nothing at all". Many aviation engines leak a small amount of oil for long periods of time without incident. In our case, we know it comes from a combination of the pan gasket, pushrod tube gaskets, and probably a small amount from the case half seal (thread) like you. We have chosen the "watchful waiting" approach. It's been working for over a decade. Engine is currently at 32 years and 2400 hours since overhaul. I hope I'm not giving the impression that I'm cavalier about this. The thing that bothers me most about it is not the leaking that's happening now, but the way the current leaks could mask new leaks. However, it's also true that an attempt to fix the current leaks could actually make things worse. When we look at the risk analysis in the cold light of day, it feels like the genuinely safest and most practical thing to do is nothing, until the status quo noticeably changes. Again, "noticeably changes" is a risk, because we're probably more likely to dismiss a developing problem as same-old-same-old. But it's a risk we're balancing against other risks that are equally weighty.

I notice everyone is jumping on the OP for the sin of perhaps prematurely replacing their engine. I get that, but it's possible you're all missing the point. How many of you have looked at lead times lately for actually getting an engine overhauled or receiving a factory reman? I have, though I don't claim to have turned every stone. In general, parts and lead times for engine overhaul work are very long. This idea of waiting until your engine "talks to you" through oil consumption, borescope inspections, oil analysis, metal in the filter, etc. is all well and good; but if it speaks to you any time soon, you're likely not going to get the 1-2 month turnaround time that has historically been available. These days, an airplane can easily be down for 6 months or a year with that strategy. A local club I'm affiliated with just got a quote from Air Power for a factory reman O-320-D2G in a 172. Estimated delivery date is October 2024! I expect any individual customer could do better than 1 year by calling around, beating the bushes, etc. But at least in my community of aviation friends, concerns about deciding when to overhaul the engine are trending further away from waiting until it's "actually necessary", and further toward swallowing the bitter pill of higher cost and arguably premature overhaul in exchange for predictable schedules and using preferred suppliers. Some of these folks' airplanes are just toys, but they're toys they want to have available and enjoy. In other cases, the airplane is owned by a business or club, whose entire usage model is based on dispatch availability. For those folks, a 6-month down time could effectively end the club/business. So in summary, I wouldn't pull a well-running motor off an airplane just because I was afraid of some number on a calendar or tachometer. But I might very well do so to reduce the chance of the airplane being grounded indefinitely, waiting months or years on engine parts and services. That's a real thing right now.

I don't own either unit, and I guess it depends on what "holder" you have. But it seems unlikely you'd be able to re-use a 796 holder with a 760. The two units have different physical dimensions (8.0x5.1x1.5" vs. 7.29x4.85x0.91”), and they use different power connectors.

While this doesn't directly address your issues with panel tilt and limits, my opinion on calibrating the zero airframe pitch setting of an electronic attitude indicator is that most people seem to overthink it. I'm aware Garmin prescribes a detailed calibration procedure. But remember that for most of the almost-hundred-year history of attitude indicators, you could directly adjust the zero-pitch setting of the AI using a knob right on the instrument, in flight (mostly to deal with parallax differences for pilots of different height). Nobody paid any attention to how precisely that setting matched the actual zero pitch of the airframe. You just got it close, then figured out in flight what attitude produced level flight at a particular speed on a particular day. As others have noted, this varies, so it's not like you can really train yourself to achieve level flight by always holding the airplane representation exactly on the dividing line between sky and ground anyway. Some pilots - like me - even periodically tweaked the AI in flight, as you might do with a heading bug, to mark exactly where to hold pitch on a particular flight segment. If you translate that to an EFIS, the equivalent would be to install it, leave the tare setting at zero, and go fly on a nice VFR day. Pick your normal cruise speed, hold level flight based on looking outside and at the ALT/VSI, and just note the pitch setting on the AI. Get back on the ground, change the tare setting to the opposite of that noted value, and you're done. Again, I recognize this doesn't exactly follow the calibration procedure in the installation manual, but it certainly meets the intent, and is entirely reasonable and safe.

No, this was sold. My apologies for not updating the title, I'll do so now.

It's been a few years since the last visit, but I've stopped at KTDW multiple times and always had a good experience. I'm sure KAMA is pleasant, but the typical fuel price difference tips the scales in favor of the smaller airport.

I recognize it's de rigueur to speculate on how to achieve best longevity of fuel tank sealant, given how expensive and frustrating it is to deal with seeps. But I think there is much speculation and little (or no) evidence for most of the pet theories. Even if the pet theories have merit, it's hard to say to what extent non-full tanks compete with hard landings, and operating on grass runways, and differential heating from sun exposure when unhangared, etc. as sources of decreased sealant longevity. Furthermore, the fuller the tanks when sitting, the more weight sits on the ridiculously expensive landing gear doughnuts, potentially causing them to wear faster, etc. Call me a contrarian, but my suggestion is that you pay no attention to any of this. You can't really control most of it, and even if you could, there is no serious evidence for all these pet theories about sealant longevity. Just fly the airplane in the manner that best suits your needs, keep an eye out for seeps (and other wear items), and address them when needed.