Vance Harral

Yes, in this kind of arrangement, the shop is supposed wire the audio lines of your "second" radio to the COM1 inputs of the GMA 35c, and the GTN750 to the COM2 inputs (i.e. wire them "backwards" relative to normal use). The GMA 35c is then programmed to logically swap the two COM devices in software for normal operation, such that the GTN appears to be COM1. But if power to the GMA35c is subsequently lost, the internal relays that close will wind up connecting the second radio to your headset, avoiding the problem of having a working COM2 radio that you can't select because the COM1 GTN you would otherwise use to select it is offline. Note that this concept is often misunderstood or not correctly implemented by avionics shops, you can find several complaints about it on Beechtalk. Having said that, the engineer in me is pretty skeptical about this stuff. It's neat to demonstrate that when you turn off power to your audio panel, internal mechanical relays close that short radio wiring directly to your headset. But a simple loss of power is not the only manner in which an audio panel can fail, and in fact I doubt it's even the most common failure mechanism (anecdote: I've never had an audio panel lose power, but I've logged several occurrences of headset jack failure, which requires a completely separate backup strategy). Furthermore, this idea of making COM2 the "failsafe" instead of COM1 is all well and good, but it's not clear to me there's any kind of rollover mechanism that makes COM2 the failsafe only if COM1 loses power at the same time your audio panel loses power. I think it's one or the other, exclusively; and I figure if you're unlucky enough to lose power to both your audio panel and only one of your two COM radios, Murphy's law dictates that whichever COM radio died will be the one that's wired as the audio panel failsafe. Accordingly, I'm not sure why the "swap the COM inputs" trick actually buys you much. I'd advise you to not worry too much about it and just squawk 7600 and carefully get on the ground NORDO in the event of a problem. But if you've got the coin for a GMA35c, you probably have a GTX-345R remote transponder too, that you can't control if your GTN goes offline.

I think I'm agreeing with you when I say that wiring stuff up on the bench is a somewhat uninteresting experiment, and not indicative of the labor to actually install the system. In addition to not having to worry about routing, you also don't have to secure anything in a way that will hold up to years of airframe vibration. For us, feeding wire through nooks and crannies of the airframe was not really all that labor intensive either. The real bear is that unless you're (re)building the entire system from scratch, you have to disassemble the D-shell connectors that are already plugged into existing components in-situ, to add new pins (and if you're doing the work cleanly, to remove old ones as well). That's not something you're going to get a handle on with bench testing. In our case, getting access to the D-shell connectors for the GTN-650 ARINC connections was extremely difficult, and we had to de-socket over a dozen of those micro-sized pins for the no-longer-needed GI-106 connection as well (a lot of shops simply don't do that sort of thing, they just cut the wires). The transponder D-shells were a little more accessible but not much. Again, there's sort of a Mooney tax here due to the limited space behind the panel. Depending on how prior work was installed, it can be incredibly difficult to add new work without damaging anything - especially since some of the newer Garmin gizmos have the configuration ROM embedded in the connector, with tiny, fragile wires. If you damage any existing work you have to repair it, which is a lot harder than installing new stuff from scratch. And the damage may not be apparent until you start trying to bring up the system after initial installation, in which case you have to debug, then go back and disassemble things again. You can probably guess how I know all this. None of the work strikes me as particularly difficult, just tedious and time consuming. Again, pros make fewer mistakes, and I'm not trying to justify exorbitant shop rates that seem to be based on what the market will bear rather than dollars-per-hour labor. I'm just scarred by the experience of thinking it would take X amount of time, being "smart" enough to plan for 2X, and then discovering once again that things often wind up taking about double your 2X estimate. Like doing your own plumbing at home, the labor cost often seems more reasonable once you've actually tried doing the job yourself (successfully or not).

Almost the same at the flight school where I teach, except for better or worse, no engine monitor, just traditional single-cylinder CHT/EGT. But 2x G5 and GNS-430 seems to be a common standard for the time being, for reasonably equipped for IFR (including actual IMC). I wouldn't hesitate to take such an airplane into any weather the airframe itself is capable of handling.

Not trying to justify the shop's quote, but if you're installing a G5 HSI, the G5 unit and its 4 connections (pitot, static, CANBUS, RS-232 or GPS antenna) is only a fraction of the work. If you want the HSI to actually show heading you have to mount and wire a magnetometer, and if you want it to show nav information, you have to interface it to a navigator, which is a multi-wire thing that almost always has to be done through a GAD29 box that you have to mount somewhere. There's an OAT probe option which gives you true airspeed data that may be in the shop quote. If you want altitude data sent to the transponder for serial altitude encoding, that's another G5 -> GAD29 -> transponder connection. Autopilot interface is another GAD29 connection. All this stuff involves disassembling existing connectors and adding additional pins to them. The mechanical mounting of the magnetometer and GAD is some of the work, and the addition of pins/crimps/solder joints to connect up the nav box and transponder and OAT probe is quite a lot of work. And while we joke a little about the "Mooney tax", the tight space behind the panel in the average Mooney really does make the job worse. You have to build a shelf behind the panel for the GAD29, or alternatively put it in the tail cone and remove the interior to run the wiring up to the panel. That's what I thought too, but it took me a little over two weeks of working more-or less full time (not including weekends). I'm slow, though, and of course it goes faster if you've done it before. Again, not trying to justify the shop's quote, which I agree sounds exorbitant even at 80+ hours of labor. But bottom line, there's a big difference between an ADI vs. an HSI installation for any of the G5/GI-275/AV-30. Again, @Jake@BevanAviation hit the nail on the head when he pointed out that it's all about the connectivity you want, and that's mostly on the HSI side. You can whittle down the cost by connecting less stuff, but only at the tradeoff of reduced capability.

Same "slop" in our 1976 M20F. Like others have mentioned, tape of some sort around the tube is a good idea. Our actually had a small groove worn in it, but according to the IA who looked at it, not enough to warrant replacement. The tape has kept it from wearing further.

Kudos to @Jake@BevanAviation for replying, you should weigh anything he has to say more heavily than anything I have to say. He's a pro and I'm a rank amateur. Having said that, note that the G5 clearance and yoke shaft issues I mentioned wouldn't be an issue in your panel if you leave it as-is rather than cutting a new one. You could also get full connectivity of your STEC autopilot and your GNC355 to a pair of G5s, though doing so would require a GAD29C interface box which retails for about $500 and requires a little extra wiring. Not trying to steer you away from the GI-275, just making sure you know the G5 is definitely a capable option that would save you a little money. Exactly how much is hard to say, especially if you contract with an avionics shop - you just have to get quotes and see. For a little while when the GI-275 was new, shops seemed to be quoting more labor to install it vs. the G5, even though the actual installation complexity was the same or less. My guess is that was a temporary thing that's no longer true. Maybe a little what-the-market-will-bear-for-new-toys, and a little uncertainty when the shops hadn't yet done many installations.

Contrary to some of their other gizmos, Garmin sells and publishes installation manuals for the G5 and GI-275 to end users; and the nature of the STC is such that the devices can be installed by an A&P, some of whom are amicable to supervising an owner doing the work. This is frequently a bad idea, leading to terrible installations (e.g. https://www.reddit.com/r/avionics/comments/yj8101/another_bad_g5_install/). But if you and your A&P are very comfortable with electronics technician skills, and willing to carefully read and meticulously follow the entire installation manual, it's a way to work around the presently exorbitant cost and lead time of having an avionics shop do it. The devices and the wiring/tools to install them can be purchased from several vendors (https://www.steinair.com is my favorite, but no affiliation, just a satisfied customer). Be sure to purchase the certified version of the instrument that comes with an STC download, not the cheaper version that is only legal in experimental aircraft. As for the units themselves, I have a lot of time flying with dual G5s, and a little time with the GI-275. The GI-275 has more features, a higher resolution display, and requires no physical panel modifications in the average vintage Mooney. The EIS version of the -275 provides engine monitor functionality, and can make for a cosmetically attractive panel along with the ADI and HSI flavors if you go all-in on Garmin. People who have the -275 seem very satisfied. But I think it's not a no-brainer choice, partly due to higher cost and shorter battery life vs. the G5, and partly due to the fact the physically smaller display with more stuff on it can appear cramped to those of us with aging eyes. The G5 gets you a simpler and physically larger display that I find easier on the eye in use, despite its lower resolution. It also saves you on the order of 1 AMU per unit vs. the GI-275, and the square form factor is arguably a nicer cosmetic match for the higher end JPI/EI engine monitors if that's your preference. But before you get too excited about that, take a look at your physical panel. In a lot of vintage Mooneys, a dual G5 ADI/HSI setup in the standard six-pack locations requires slightly ovaling out the panel holes with a file, due to clearance issues. Also, the lower-right-side physical knob of the G5 HSI often winds up close to the yoke shaft in kind of an awkward position. Those issues are mitigated if you cut a big rectangle in the panel and flush mount them, but then you have the extra time/expense/hassle of the flush mount and the panel cut to accommodate it. Bottom line, I'm sure you'd be happy with either, but this is not one of those cases where it's a no-brainer to go with the newer instrument. Suggest printing out some life-size, life-resolution pictures of each, and taping them to your panel, to see what it looks and feels like from the pilot's seat.

If Concorde themselves recommend a battery tender, they're obviously the best source of info. That said, my anecdotal experience matches Mike's - we have absolutely no need for the things. We've had 3 Concorde batteries over the last 19 years, so average lifetime of over 6 years. The airplane flies 75-100 hours per year and typically flies at least once a week, but occasionally sits for periods of up to a month. Sometimes we "tax" the battery during maintenance (e.g. gear cycles), then charge it up with a cheap automotive battery charger after. That's the extent of our stewardship. This behavior would be considered downright abusive by the BatteryMinder crowd, but the only battery problems we've ever had didn't actually involve the battery (left the master on once, another time the shower-of-sparks system went kaput and we ran the battery all the way down trying to start the airplane, got the airplane started both times via jump from a car). We do perform capacity tests, though our test method consists only of "leave the stuff in the airplane turned on and measure voltage with a meter". This is all anecdotal, so not trying to sway anyone's opinion. Just providing a data point that I kinda don't get the Battery Minder religion, at least for airplanes that fly on a regular basis. I might feel differently if the airplane sat for months at a time, or if we lived somewhere with 110 degree summers. But for our specific situation, given our actual experience, there's just no justification for the extra cost and hassle of a tender (which is admittedly minimal). Again, though, if Concorde themselves recommend a tender, that's obviously the gold standard.

At the risk of thread drift... I think the horse has already left the barn in this particular case. It's true there is still no regulatory definition of "congested area", but recent enforcement actions have established precedent for increasingly conservative interpretations. See https://pilot-protection-services.aopa.org/news/2016/january/15/congested-area, whose money quote is, "In enforcement actions, the FAA has successfully declared that a congested area includes a group of people on an airport ramp, sunbathers on a beach, a small subdivision covering less than a quarter mile, and traffic on an Interstate highway." There are also a few LOIs already issued that reference specific NTSB cases with very conservative interpretations. Where the rubber hits the road for me on this is teaching 8s on pylons to commercial students. An increasing number of them are taking advantage of the TAA clause in the experience requirements to take the check ride and execute essentially all their commercial training in 172s and PA-28s. On a day with even a light breeze, these airplanes achieve less than 100 knots ground speed at full power, making their pivotal altitude when headed upwind below 900' AGL. Teaching in a major metropolitan area, I've more or less accepted there's no practical way to teach the maneuver without being in a 91.119 gray area at best. I try to mitigate this by never orbiting one "pylon" more than once or twice, then moving on to some other area. I certainly feel a little better about it in a Mooney, where it's possible to keep the pivotal altitude above 1000' AGL.

In other words, you're not actually interested in physics, only your gut feel based on life experience. I get it, none of us have time to run a free body analysis for every decision we make in our life. I don't do it when I'm deciding how hard I can brake on a bike, or whether I can jump over a log. But let's be honest: you don't really have any idea what happens to a Mooney in a given set of ditching circumstances. You're just projecting other "stuff" onto a completely different scenario, and assuming it makes sense. Often that strategy works, but sometimes it doesn't, and this is one of the latter cases. I hope so too, but if either of us need to ditch, does doing it with the gear up make us more likely to catch a wingtip on a swell and suffer a hard yaw that slams heads against side windows? Maybe better to leave the gear down so all the impact force is in the direction the seatbelts are designed to restrain, right? See, I can play the "what if" game too. To repeat, the only serious study I can find says gear position doesn't make any difference in survivability (regardless of whether the airplane flips or not), so you should focus your energy on other things: touching down at minimum speed, having the correct size life jackets, etc. If you've got a more in-depth look at it that says something different, I'm all ears. But if all you've got is "gut feel", then meh. For now, I remain convinced that the usual blather about landing gear, high wing vs. low wing, etc. is just noise. It certainly isn't useful, and it possibly distracts people from understanding from what's really important about ditching.

If the physics are so predictable, and your understanding of them so complete, why didn't the Caravan in the video flip over? I'll look forward to your free body dynamics diagram which computes the rotational acceleration imparted by the landing gear impacting the water, showing it to be greater (or less) over the full 180 degrees of rotation, vs. the drag of the forward fuselage as it enters the water and resists the rotational force transferred from the landing gear. Be sure to define your assumptions about speed and impact angle at the moment of touch down, as well as whether the water is smooth or rough and the subsequent effect on the co-efficients of friction.

Well, this is the problem with talking about this sort of stuff. You've formed a reasonable opinion based on "common sense", nothing wrong with that. But now you're rejecting an actual analysis based on jabbing at whatever insufficiency you can find in it, rather than finding or producing a better analysis that addresses your concern of sample size, or whatever your next objection is. I'm sure your opinion isn't swayed by the article I posted, but I suspect your opinion wouldn't be swayed by any study no matter how good, because it defies a "common sense" perception of the risk you've already formed. I get it, I'm sure I have the same biases about other stuff. Sure, here's a video of a Caravan going into the drink: For those who don't care to watch, the airplane stayed upright and everyone got out. The folks who got out hold onto the wing rather than standing on top of it, but I assume we're not so pedantic as to argue that's the critical part of the question. The NTSB report says one person died, but the listed cause of death as "acute cardiac arrhythmia due to hyperventilation". i.e. it wasn't the crash itself that did them in. On that we agree! I assume you're familiar with Michael Caine's quip about the film? For those who aren't, it's "I have never seen it, but by all accounts it is terrible. However, I have seen the house that it built, and it is terrific."

The only serious look at this I've ever found, concluded that the configuration and position of landing gear in a ditching event has no statistical impact on survivability: http://www.equipped.org/ditchingmyths.htm. High wing or low wing, gear up/down/welded, just doesn't influence what matters. For those who don't want to read the whole article, the one-liner is, "How often does the airplane flip over because the gear caught in the water? We don't really know. But even if all the airplanes flipped--highly unlikely--the occupants still manage to egress safely. Conclusion: It may not matter much."

Sure, a lot of the 130K airplanes are trainers, but so are a lot of the theoretical 50 airplanes you're postulating will be lost in a natural disaster. Yes, a lot of registered airplanes are unairworthy, but as @McMooney points out, so are a lot (most?) of the airplanes "lost" in said disasters. Using your own numbers, a loss of 20 Mooneys from a fleet of 7500 is 0.26%, which is still a rounding error - it would take 40 years of a major disaster every single year to affect even 10% of the Mooney fleet. That's really an irrelevant concern, given the rate at which Mooneys (and other piston singles) exit the fleet for other reasons. It seems to me you're just complaining about the general decline of GA, and the disproportionate impact on the Mooney fleet due to the failure of the brand as a new airplane manufacturer. I'm sympathetic to that, and worried about it myself. But the impact of hurricanes, floods, volcanoes etc. is irrelevant to that concern. To the extent Mooney (and piston GA in general) might die, natural disasters aren't going to be even a meaningful contributor, much less the primary cause.

While I understand the emotional sentiment, the math ain't mathin'. From your own data, if there are 143,000 piston aircraft in the country, a loss of 50 would represent 0.035 percent of the fleet, which is indeed a rounding error. Per GAMA, the industry built 1,909 new piston airplanes in 2023. The idea that a theoretical 50 unit loss from a natural disaster somehow represents a "catastrophic loss" for the fleet that "won't be replaced", just ain't so. Natural disasters have essentially nothing to do with the decline of piston GA. More importantly, airplane owners in the paths of hurricanes have all kinds of concerns, of which their airplane is only one, and not necessarily the most important. Whether to expend time, money, and energy to move it is their business and no one else's. That said, it's certainly true that lost Mooneys aren't replaced with new Mooneys. And none of this data changes my sympathy for those in the path.

+1 I teach my students that the NOTAM system is not designed to give valuable information to pilots, it's designed to shield people on the ground from liability. No matter how small the risk, no matter how far-fetched the scenario that would actually lead to maiming and death, everyone on the ground just wants to be able to say, "Well, I posted a NOTAM." Tower operators don't fix lights any more, because they know it's cheaper and easier to just keep re-filing that NOTAM (some of the ones in my area have been up for years). Same with VORs, cranes, etc. When I can't sleep at night, I sometimes wonder if it would be feasible to band together as pilots and simply boycott the NOTAM system. To announce to the government and the public at large (including the media), "We refuse to use this broken system. The people responsible for managing it are putting you at risk." Back to the subject at hand, I think @Hank is missing something important about that, "unnecessary government gibberish" in the Q line. The info sheet from Sporty's says that line is intended in part to support, "the automated filtering of NOTAMs". I hold out a bit of hope that in the future, one might be able to configure Foreflight or Garmin Pilot or 1-800-WX-BRIEF or whatever to simply not tell me about UAS below 400', unlit towers, instrument procedures for VFR flights, and so forth. I'll sign any waiver they want me to sign to do so.

This seems like the sort of thing Mooneyspacers could collectively fund in a way that doesn't take much cash out of any particular person's pocket. I'd pledge $100 or more toward the effort, and I'd bet there are dozens of others that would too.

Thanks for your tireless efforts, Matt.

I have very little - but not zero - time behind a GI275 set up as an HSI. It's a beautiful display, has moving map features, etc. I didn't have any trouble with the menu logic, though I'm a nerd and worry slightly that less nerdy pilots may get the thing scrolled onto a data-dense page they have trouble recovering from in IMC. To me, the primary drawback vs. the G5 is the round vs. square format. I appreciate that the round format is one of the primary selling points of the 275, but the square-format G5 has corners into which additional information can be packed without giving up screen real estate traditionally dedicated to the HSI itself. As the pics below show, the round format requires things like distance/ETE/HDG/CRS to sit on top of compass numbers, the course pointer, etc. Garmin did a perfectly reasonable job of this, but there's just no getting around the fact that some of the displayed data covers up stuff that doesn't have to be covered in a square format. That said, everything's a trade-off. If you'd never seen a square-format HSI you wouldn't care about the "packing" of information. And the higher display resolution of the 275 is going to be favored vs. the lower-res but physically larger G5, by lots of pilots with good near-distance vision. I'm pretty sure no one has installed a 275, hated it, and gone back to a G5. They're both great instruments. I'd be curious to know if Garmin relocated the control knob from lower right to lower left because there are so many airplanes with the yoke shaft close to the lower right corner of the DG/HSI.

I like the dual G5s and think they're an economical solution. Older tech than GI-275s, but superior in some ways (I like the square display and larger physical screen size, albeit with fewer pixels). Be aware that if you don't cut a whole new panel, the rotating knob on the G5 HSI will wind up very close to your yoke shaft, which is an annoyance I didn't understand until after ours were installed. It'll be slightly closer to the yoke shaft than the adjustment knob on your current DG, and you'll use it in flight a lot more often to set a heading bug. I don't think we would have done anything differently if I'd known about this in advance, but I think about it almost every time I work with it. You either use your left hand - a little awkward if you're right handed - or you have to scrunch your right hand down along the yoke shaft to turn the knob. @Ragsf15e has solved this problem with a panel that mounts the G5s to the right of the yoke shaft. Another solution is to go with GI-275s which have their control knob on the left side rather than the right; but that's significantly more money and a physically smaller screen in exchange for some nicer features and capabilities.

This sort of thing is always a little surprising, but it's not that uncommon. An engine with multiple cylinders will often continue to produce power even after throwing a rod. A few years ago, I worked for a company that had a data center with an emergency backup diesel generator. They hadn't tested it in ages, which is obviously not great management. Anyway, one day the power went out, the generator cranked up, and after a few minutes it broke a rod in such a manner that the flailing rod sawed the crankcase completely in half. But because of the way the engine was mounted, the crankshaft was still fairly well supported. It ran like that for a couple of hours before anyone went over to investigate the noise they had previously assumed was just normal.

You are correct, and Yetti's statement is simply wrong for M20E models of S/N 21-1181 and on. The positive lead of the gear warning sonalert is connected to an output pin of one pole in the DPTP uplimit switch, and the input pin of that pole is connected to the gear unsafe light, hence why the light can extinguish with the disabling of the gear horn CB. But the wiring of the gear horn is a little complicated - its positive lead is connected to several things, including the throttle position sense switch, and I agree with other speculators that a mis-placement of that switch is the likely cause of your problem. I understand people are just trying to help, but I really wish folks here would stop making blanket statements about electrical wiring without identifying specific models and serial numbers, and ideally referencing schematics. Mooney changed the electrical wiring of the C/E/F models several times over the production run, in some cases changing the logic of the test and warning circuitry. What is true in one "Vintage Mooney" isn't necessarily true in another. You have to look at the schematics to give advice.

Circuit breakers definitely wear out, especially if they are manually pulled from time to time. Agree that it's not particularly likely to be the problem, but it's definitely in the the set of things to check and/or consider replacing.

On that we agree. We know they wear, but not at a rate of concern provided they're inspected and maintained. I do think the speculation on how many years they might last is pointless, as it's not calendar time that causes them to wear. Are you certain of that? Some closed, lubricated systems effectively form a constant thin film between the meshing surfaces, such that the surfaces never actually touch. I'm mostly ignorant in such matters, and not claiming the 40:1 gears last "forever". But I could believe it's possible to design a set of gears with a high enough ratio that the force between gear teeth is never sufficient to entirely displace the lubricant.

Every time you post this hypothesis that only poorly-maintained 20:1 gears wear out, I'm going to counter with my anecdotal story that our 20:1 gears wore to the point of failing the SB M20-190B inspection, despite regular maintenance and proper regreasing per the associated SB/AD, over many years of ownership. We knew this was coming, as the backlash in the gear set got progressively worse over a period of multiple inspections. Wear is obviously a function of gear cycles, and we put more on our airplane than most. So I'm not surprised there are airframes with the original 20:1 gears, and lots more hours than ours. I'm sure it's also true that poorly maintained gears wear faster. But the 20:1 gears absolutely do wear out, even when maintained properly.