EricJ

Sounds like something is binding or there's an issue with the motor. I'd get it up on jacks and do some gear swings with the belly off and see what's up. Edit: Wait, never mind. If it's the gear warning popping that's going to be something different. First thing to check is to open up the ceiling panel where the Sonalerts are and make sure it's not contacting the metal roof. That's an easy place for a short and an easy fix if that's what it is.

+1 on Bruce Taylor at Air Power Accessories. He is very experienced with the dual mags, and talked me out of doing an overhaul and just doing a 500-hour for some good reasons. Mine was done in February for about $1800 and it's been fine. Bruce is very good to work with. Highly recommend.

There are a few Js out there that have STCs with turbos. My understanding is that none of the kits are available any more, but you might find an airplane with one installed for sale somewhere.

Those are the details you learn in the manuals for the individual props. Most composites have repair methods and repair limits. Metal props do, too.

Same as other composite props, like MT or wood or whatever. They usually have a leading edge that is nickel or stainless or something.

There's not a lot more efficiency that can be squeezed out of modern propeller designs, so most of the innovations now are on reducing weight and reducing noise. Don't expect anything to give you a significant increase in speed without somehow putting more power into it.

That's what the article said they were using, presumably to better handle the time variance and non-stationarity, which is something that wavelets can be good at. I suspect it could be done with more traditional means, and the article mentioned short-time FFTs, etc. I think if the signal always looked like it does in Figure 1 it'd be pretty straightforward, but the corner cases and time variance, etc., probably led to their alternative approach into the buzzword algorithms. But if it works, more power to them.

Yeah, I was wondering where they were computing the wavelet transforms for the respiration, or however they're actually doing it.

Yeah, I've done a bunch of deployed projects with software radios running on RPis over the last ten years, and they're doing a lot more processing and wind up not using much of the total available resources. It's crazy what you can get done for a few bucks these days. And now I see people are writing libraries to offload typical signal processing stuff into the GPU in the RPi (e.g., FFTs), so it's getting interesting. I have a hard time keeping up with the actual state-of-the-art any more since I'm no longer in it full time.

Yeah, I was wondering how much computational bandwidth a pulse ox has to have to be able to do that, unless it's sent offline to a separate display or something.

I can imagine that makes a decent noise.

Was just gonna say, they're far enough apart in frequency to be generally separable if not orthogonal. The characterizations shown in the article demonstrate that it's fairly practical. Probably don't even need a wavelet, but if that approach works, great. Sometimes I think wavelets get used just because they make good buzzwords in the presentations or even in the marketing materials. Pretty cool, though!

Absolutely. Wing spars seem especially susceptible, and send a borescope down between the interior and the pilot's side window to check the condition of the steel tubing (plus anywhere else that's handy). If you're not seeing any paint get pushed up in spots by surface corrosion, and the inspection goes well, then you're probably in good shape. If the controls don't have a lot of slop and the rod ends don't have a lot of play, that's a good sign, too. If things have been kept lubricated it can minimize the likelihood of future failures. If your engine is running well, not using excessive oil, compressions are good, operating temperatures are good, then it's probably good to go for a while, too. There are enough piston-engine airplanes in Europe that I'd be surprised if avgas got outright banned for a long time. It might get more expensive, but it's doing that everywhere.

I do gear first for this reason, sometimes even before any power application, unless I'm too close to the ground. The gear-in-transit-up speed on my airplane is not far from instrument approach speed, and when I first got the airplane it'd blow the breaker if you tried to pull the gear up at anything over 90 knots (it's better now). On a go-around or a missed approach it made it difficult to apply full power and not pitch up excessively to keep the speed down, so I got used to either pulling the gear up first, or going to about half power, stabilizing, then gear up, then full power and deal with whatever the flaps need. There's such a variety in airplane behavior and good practice for stabilizing things that I don't think there's one rule to apply to everything.

I had an IA that I worked with before I got my IA, and even before I got my A&P we could get the entire process done in a couple days. Only a day and a half was with the IA, the first half day was me opening up the airplane and getting it ready for the inspection. As others have mentioned, a key to being able to do that is to not have any deferred maintenance. If the airplane is in good shape, the inspection shouldn't be an arduous task. And my IA was not prone to let anything slide, and wasn't even that thrilled about an owner-assisted annual other than getting some slave labor opening things up and putting it back together. It is definitely good experience for an owner, though, and I highly recommend it when the situation allows for it.

I've not used that one, but I used a couple of the other paid services when in A&P school. The FAA DRS is pretty easy to use once you figure it out, so I've not felt the need to try anything else.

I would suggest not poking the bear.

A good way to do this is to use the FAA Dynamic Regulatory System to do AD searches. It's what I use for annual inspections, etc. There are some online vids on hints to make it easy to use. https://drs.faa.gov/browse Click on ADs, then Final Rules. Under product type select Aircraft, then under Subtype select Small Airplane. Under Model select M20J. You don't need to select a Make and it's actually easier if you don't. That will give you a comprehensive AD list for M20Js. You can then go back and select Engines or Appliances or Propeller under Product Type (hit Clear first to restore the full list), and find ADs for those. You can then go through and find which ADs apply to your specific M20J and which don't. Yes, it can be a lot of work, but once you've done it once you just need to check for new ones after that.

Many ADs are specific to serial numbers and installed equipment, so there isn't going to be one spreadsheet relevant to all J models. Just fyi.

Be careful what you wish for. A re-do of the existing list could open the door for somebody claiming it is again a comprehensive list. The Coleal letter gives a lot of wiggle room for good judgement and coordination with maintenance personnel. I think that's a preferrable method.

The beauty of the Coleal letter is that it pretty much leaves what is or is not Preventive Maintenance up to the operator/owner under some very general guidelines. My takeaway has been that if you coordinate with your regular A&P/IA and if they bless you changing brake pads (for example) as preventive maintenance, I'd think you're good to go. I also think that's not an unreasonable thing to do for the reasons mentioned previously. The IA's blessing matters, since they have to sign off the condition of everything at the end of the year. A similar thing is doing "supervised" maintenance under your A&P's supervision. An A&P can "supervise" anybody doing anything and sign it off. The person doing the work should make the logbook entry with their certificate and signature, and then the A&P signs off the return to service. There is very little distance, in my opinion, between being supervised doing a brake change and doing a brake change under PM, for somebody the A&P deems competent to do so. For the PM case it's the opinion of the guy that signs off the annual that matters, so my advice is to coordinate with them, too, if they're not your regular A&P. FWIW, any maintenance is supposed to be logged in the aircraft maintenance records, so anything somebody chooses to do under PM should be recorded in the usual aircraft records with the name and certificate type and number of whoever did the work. This allows the IA to know what's up at the end of the year, and to make certain everything is okay. If you've previously coordinated with the IA, then there aren't any surprises.

My 77 J has no beacon, just strobes.

Nicely done! The pics are great.

This thing can be handy for holding adel clamps shut for installation. I've used mine a number of times and saved a fair amount of aggravation. https://www.aircraftspruce.com/catalog/topages/handeeclamp.php

dh/dl is hydraulic drop per length that the fluid travels through the media. If the input pressure is the same and the depth of the media is the same, the drop will be the same. That's why stacking filters doubles the drop, because it doubles dl. And the point of pleating is that it increases the area of the filter media within a particular volume without increasing dl. No, it doubles dl. The air gap between them is just an air gap.