Ryan ORL

I had already replaced the right magneto w/ a brand new Champion Slick for unrelated reasons (chasing mag noise, didn't solve it) I think for the impulsed mag (left) I will definitely be going SureFly to get rid of the couplings altogether.

I think when all is said and done here, there is no way I install another Slick impulse couples magneto… I will almost certainly go to a SureFly. That being said that only covers one mag… what’s involved with going to Bendix on this engine? Aren’t they larger?

Maybe I am not seeing it on their site but do they do engine work? Otherwise I’m not sure what I might be able to get their help with, we are AOG in KRAP so couldn’t get the plane itself to them in any case.

Incidentally… anyone who can recommend an engine shop somewhat near South Dakota, would love to have some other options

More of the impulse internals

tl;dr - I have had two impulse couplings destroy themselves in less than 200 flying hours, resulting in 1 and now more than likely 2 engine IRANs. Background: I had my Mooney M20J's IO-360-A3B6, equipped w/ Slick 4372 and 4370 magnetos sent for major overhaul in January 2024. It returned to service in March 2024 and had 110 trouble-free flying hours, with no adverse symptoms. In fact, we flew to Alaska and back, and everything performed perfectly. Engine ran like a top and barely used any oil and leaked not a drop for 110 hours. In July 2024, when starting up the engine at my home field self-serve pump, I heard a strange (very loud) whirring sound that I thought was an electric fuel pump sound at first (which should have been and was off, as in a normal start). The engine ran very poorly so I shut it down. After some simple investigation, we found pulling the prop through revealed the impulse coupling was very messed up. Rather than click-180-click, it was click-click-click. My home shop removed the left magneto and discovered that the impulse coupling had destructively let go, destroying the magneto drive gear, damaging the accessory drive gear(s), and rained metal debris into my accessory case, resulting in the engine being removed for IRAN and sent back to my engine shop for a warranty claim. The engine shop dutifully performed an IRAN under warranty... and apparently the magneto shop (QAA), paid for this labor, since they were the provider of the magnetos during the major overhaul. After some delays, I was back flying in October 2024 with a freshly IRAN engine and a replacement (still QAA) Slick 4372. Due to some electrical issues (unrelated to this), I have only been able fly around 80 hours since. Fast forward to this week. As I write this, I am in South Dakota and my Mooney is at KRAP. I started up the aircraft, and it ran fairly poorly. (Although without the loud whirring sound as before). A quick magneto check revealed that the left magneto was DEAD. Engine totally dies. Shut it down and inspected. On a hunch, pulled the prop around by hand. NO impulse clicks at all. Shop on field took a look and we quickly removed the magneto to find... utter carnage, again. Photos attached. It appears that the rivets failed in the impulse coupling and the pawls became stuck at high speed and the whole unit destroyed itself, breaking off large, thick metal chunks and again damaging the gears. I am at an utter loss. How could this happen again in so few flying hours. Is there anything on the engine side that could be causing this? Could a drive gear be misaligned or wrongly-sized or putting side load on the magneto drive gear or something? Looking at the accessory drive gears I see absolutely no way this should affect the impulse coupling but again I have no idea. This is getting into serious money now and nobody has any ideas what the hell might be going on here.

See everyone there!

I target 1250 with mine also. Any higher and the CHTs are unacceptable.

I have both but I keep my G3X default (and on my iPad in ForeFlight) to showing SXM always. I almost never look at the ADS-B WX in my own airplane. (But I use it often in aircraft that I instruct in) SXM weather is just better. More detail, further out, faster refresh, etc. Now, maybe that isn't worth it for the type of flying you do, but it depends. But, as a Central Florida pilot who is always contending with thunderstorms, one feature of SXM that I find absolutely crucial is the ability to look at both Composite and Base Reflectivity. ADS-B does not offer Base Reflectivity, but that is the picture that shows you better where the really nasty stuff is. I don't particularly care about precip falling up in the flight levels. Particularly after the thunderstorms have begun to dissipate, the Base vs. Composite picture can tell two very different stories. I also appreciate that SXM has the storm cell attributes, etc. It has a few nice little features like that.

Mike and GeeBee, that theory sounds very plausible to me! Will definitely report back what happens w/ the new condenser. I suspect you're right.

Going to try that and see what happens, thanks everyone!

I don't know the exact mechanism but the logic goes something like this... (Mike Busch described this calculation in general terms on a podcast once, but it basically just follows logically): First, the engine monitor has to decide whether the engine is ROP or LOP. This can probably be pretty easily approximated just from looking at whether the fuel flow is in the plausible range (given those tables) for "best power mixture". Anything less than a particular fuel flow for a given MP/RPM combo can be assumed to be LOP. If ROP - Excess fuel, air (MP) is the limiting factor. % power is given by MP/RPM table lookup. Fuel flow has little measurable impact on horsepower, probably mostly disregarded. If LOP - Excess air, fuel flow is the limiting factor. % power is computed by fuel flow and RPM only, probably using some figures from the BSFC curve.

So this is a bit of a strange problem. Starting a few months ago, I started noticing significantly diminished comms reception, and a loud rapid clicking on the comms. Some brief debugging revealed that it wasn't really comms reception at all, but rather the loud clicking noise was playing hell with the GTN auto-squelch and the problem seemed to be slowly getting worse. Some further troubleshooting revealed that the problem was only evident on the RIGHT magneto, i.e. the clicking noise disappeared entirely when running only on the LEFT magneto, and the clicking was certainly RPM dependent. It was easy enough to break squelch on COM1 and just listen to the click disappear and reappear when switching the mags. My local shop started debugging this, first checking for loose grounds (etc) and checking the magneto harness for pinching, chafing, or arcing. They found one slightly loose shield and corrected that. They did some kind of high voltage test on the harness (~110 hours old, new at my recent engine overhaul) and found no problems. There was also nothing visually obviously wrong with the harness or leads. So I did a bit of further debugging with a portable radio. The clicking was actually audible on the portable comm radio with all my aircraft electrical systems entirely turned off, in other words it was most definitely arcing somewhere, and our assumption was it was inside the magneto. Sure enough, the shop tested the condenser and found it was a bit out of spec, and they put in a known-good spare that they had while we ordered a new one and waited for delivery. That cured the clicking entirely. Comms totally quiet on either mag. Hooray! As an engineer myself I also wanted to understand what went wrong... so fortunately this also entirely made sense... a bad condenser would lead to the points arcing, case closed, I thought. The new condenser is due to arrive this week, so I am still flying on the 'spare' one. I had around 5-6 trouble-free flying hours on it. But on Saturday when I went to fly the airplane... the clicking was back! Now, we haven't had a chance to dig into this yet... we're of course going to install the new condenser, but my concern is that either I am just enormously unlucky, or something else is killing the condenser and the new one will just fail again. So does anyone have any theories on what the hell might be going on inside this magneto? The mag itself is relatively recent... 110 hours also, from the overhaul, it was an overhaul unit from Quality Aircraft Accessories. At this point I suspect there must be some other internal fault there... I am inclined to just send the whole thing out for overhaul or even try to get an exchange unit. I am honestly tired of chasing the issue. Could it also be something with my plugs on that side? I run all Tempest Fine Wires that have maybe a few hundred hours on them.

Certified Engines Unlimited in South Florida. $1500 expedite fee. To be fair they only promise 8 weeks for that but they got it done in 4.

Base IO-360-A3B6 OH cost (March 2024) was $40k plus or minus $1-2k (based on at least 8 shops I got quotes from). That assumes reusing basically everything and OH’d cylinders. Standard turnaround time 14-18 weeks plus or minus. I opted for a new camshaft and new (PMA) cylinders, plus freight and a couple minor extras. $48k for the engine shop altogether. Paid to expedite and got it in 4 weeks. I spent $14k on the rest… removing and reinstalling the engine, new everything (mounts, hoses, etc), overhauling my governor, etc etc etc.

What even is the point of the debate on who is enforcing the STC? It's obvious that it's nobody... Who is enforcing that you aren't doing all your own maintenance without an A&P? Who is enforcing that you don't install unapproved minor mods? Who is enforcing that you are actually current? Who is even enforcing that you have a pilot certificate? In 20 years of flying I have never been ramp checked by an FAA inspector. The only person who has even looked at my pilot certificate is US Customs when coming back from Canada/Bahamas. So if I was only flying domestically I likely would still not be asked. Obviously the vast majority of aviation is on the honor system. STCs, maintenance paperwork, currency records, etc.

Because you were quite transparently implying that I am some kind of shill for GAMI or G100UL. Even now-- "the script", as if I am not capable of independent thought.

I have never met or communicated with George in any way and frankly the implication is insulting. Why can't other companies make a good blend? You would need to ask them. The fact, however, is that these other companies aren't holding these things under wraps... there have been public statements on their composition and the likely limitations. These are well along the path towards certification. Whether or not it may be possible to create a 100UL blend that has no drawbacks and the exact same (or better) performance characteristics as 100LL, the fact is that nobody has done so and there is nothing like this currently in the pipeline anywhere in the world.

There are only a handful of companies working on 100UL fuels and, as far as we can tell from their public statements, the formulations they are targeting involve significant compromises on detonation margins such that modifications to engines and in-flight procedures will be required. Maybe someone comes out of left field with a new as-yet-unannounced candidate fuel (probably unlikely because these take a long time to develop), but for now the situation, based on public statements and evidence, seems to be: G100UL - Potential (or actual) materials compatibility issues with sealants and o-rings, but superior-to-100LL detonation margins Swift 100R and Lyondell/VP UL100E - Maybe (??) better materials compatibility (but with potentially ethanol-related complications) but significantly-inferior-to-100LL detonation margins I think George's point, which is fair, is that if we're talking about unleaded 100LL replacement fuels, your choice is those two buckets. There aren't any magic miracle fuels coming. So which basket of complications would you rather have? Personally, I can't buy any of these fuels in my area and I'd rather not be an early adopter anyway. But if 100LL does eventually get banned (which many feel is inevitable), I know which set of complications I would rather deal with, and it is not remotely a tough call.

It is not just about glide ratio, it is also about glide speed, which in our airplanes is quite a bit higher than a Skyhawk, Cub, etc. A very high glide speed makes your turning circle much larger, increasing the difficulty of the maneuver.

Per the Instrument ACS, DPEs are supposed to be testing on autopilot usage for aircraft that have one installed. "To assist in management of the aircraft during the practical test, the applicant is expected to demonstrate automation management skills by utilizing installed equipment such as autopilot, avionics and systems displays, and/or a flight management system (FMS). The evaluator is expected to test the applicant’s knowledge of the systems that are installed and operative during both the oral and flight portions of the practical test. If the applicant has trained using a class portable EFB to display charts and data, and wishes to use the EFB during the practical test, the applicant is expected to demonstrate appropriate knowledge, risk management, and skill." If you have an autopilot installed, you should expect a DPE on an instrument checkride to require you to demonstrate its use on at least one approach and if you struggle with it or display a lack of understanding on it, that is valid grounds for a bust. (Notice of Disapproval)

It would be (and is) just like the Bonanza. There are practically no scenarios where a turnback is workable in a Mooney, unless you happen to already be on a crosswind before the failure occurs, and there is an intersecting runway available. (Or similar) The issue is the very high best glide speed. Mooneys do have a good glide ratio, but do so at a relatively high speed, which causes the turning circle to be quite large. Conversely, I still conduct flight training in 172s semi-regularly, and I demonstrate what does and doesn't work for turnbacks in that airplane. With a 65kt (and practically even lower at typical weights) glide speed, turning back from 600 AGL is fairly easy, and often even results in being high.

In the referenced FAA Approved Model List (AML), which you did not attach here.

What's the story there? That shouldn't be possible without a badly mis-timed mag, a cracked plug insulator (pre-ignition) or some fuel flow blockage?

I would say 25 BTDC is at least moderately aggressive in the sense that Lycoming saw fit to issue a service instruction telling (asking) owners to re-time and re-mark their engines to 20 BTDC for, among other reasons, high CHTs and better detonation margins. It really isn’t rocket science though… more spark timing obviously reduces detonation margin, and so does lower octane fuel. This is true of basically any spark ignition engine out there, whether it’s in an airplane or not. I screw around with the spark tables on my project Trans Am all the time… but I have knock sensors and an EFI system that’s capable of adding and removing advance as needed. You can push the timing hard right up until you get knock (detonation), and dial it back a bit. If you want more spark advance, the only way would be higher octane fuel… you can just dump cans of toluene in your tank if you’re so inclined. In our primitive fixed advance system the only feedback we have is CHT. 25 degrees isn’t a ton of timing for most situations, but there are certainly going to be *some* manifold pressure/RPM/fuel flow combinations where it’s a bit too aggressive, and the evidence is that the CHTs get a bit high. However even if you’re fine with your temps, the situation is obviously not improved by lowering the octane several full points. It is basically definitional that your detonation margins are worse all around with lower octane fuel. It is also obvious that it is possible to cause mild detonation at high power settings by manipulating the mixture control (I assume we’re all aware of ‘the red box’). It follows then that the red box is larger with lower octane fuel, and importantly, may encompass more operationally useful MP/RPM/FF combinations! Anyway this is all a sidebar… my original point stands. Whatever leaking/sealant problems G100UL has would need to be quite severe to make running much lower octane Mogas in most of our engines the safer option, especially with timing at 25! I would be willing to pay for more than one tank strip/reseal before I just gave up the ability to get book performance numbers without cooking my engine.