EricJ

Bushings are one of the easiest parts to make under Owner Produced Parts. A properly made bushing wouldn't need to be replaced until worn.

My main concern will be airframe parts, especially skins, which the factory has tooling and drawings for but I doubt Lasar will.

Mine's been stickered since the 406 MHz ELT was installed about seven years ago. The sticker gets replaced every two years when the registration gets renewed. It's the same with PLBs, and you get the same stickers for them, too. I keep the sticker on my PLB since it has the registration expiration date, etc.

Pretty much. A legal opinion letter from an FAA attorney written specifically to help interpret a reg has a ton of weight. If you stand in front of a judge and say you relied on this legal opinion from the FAA to help guide your actions, that's a pretty strong defense. The downside is the judge may not agree with how far somebody may be willing to go with their interpretation, e.g., overhauling a motor is probably not covered by Coleal. So care must be taken in deciding how far one is willing to go with it, and the Coleal letter even says that pilots must exercise "good judgement" in determining what is or isn't Preventive Maintenance. It's something more than what is listed in Part 43 Appendix A(c), but how much more is not defined.

Yup. This is why getting an A&P/IA that will work with you is important if you want to do more stuff on your own. The IA's signature at annual basically blesses things that came before that, but it still won't stop somebody else from demanding that something be undone or removed before they'll sign it off. Even, "my FSDO said it was okay" may not work in a different district, even if you have something in writing from the previous FSDO. If you find a good A&P/IA/shop that you like working with, keep them as long as you can. When I was a teenage lineboy at a US flying club in Europe, our DPE was a German lady whose husband was a PanAm 747 Captain and ex-AF fighter pilot. They had a 1960 Cessna 210, and the airspeed indicator was out of an F-104 that her husband had scrounged when he was in the AF. It had a piece of red tape where the redline should be, which was all it needed to be legal. They always thought it was cool to have that in there, and I always thought it was cool, too. They had a place here in AZ that they had moved back to and I used to see them once in a while, as she was still a DPE operating out of Goodyear airport. The last time I talked to her several years ago she was an angry hen because her new IA had made her take out that ASI and replace it with one that had all of the color arcs, etc. Nobody had bothered her about that ASI for over fifty years, but she finally ran across somebody who wouldn't sign it off unless it had all of the markings on it. I wish I'd had my IA at the time, but I didn't, so couldn't help her. So, yeah, you're always at the mercy of the next guy. It may not matter at all who said what or when or how at any time in the past. The entire VARMA program is an effort to try to help mitigate that at least from a parts substitution perspective, but it won't help if somebody has a problem with an owner-performed repair, like wiring, or something like that.

My understanding has always been that flutter is just another example of resonance. Many mechanical systems have resonance. The Tacoma Narrows bridge collapse was an example, too. The last time I was teaching engineering I used this video to show how mechanical resonance can be destructive, so pay attention to it. Helicopter peeps know all about ground resonance. Flutter is bad mojo for these reasons.

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.