Vance Harral

That's a fair question and I don't have an answer for it. I don't hold an A&P certificate. I'm not skilled in the art of trim tube repair or the legal responsibilities of an A&P, and I didn't ask questions about the alloy and heat treatment when the repair was proposed. ... but it remains true that a licensed A&P with a long-time practice and a good reputation made the repair, logged it, and signed it off (most likely based on experience with similar repairs). That makes it legal for me to operate the airplane. Even if this particular repair can be traced to some black-and-white regulation, others can't. I've spoken with enough mechanics to understand at certain points they're simply obligated to make reasonable interpretations of regulations that cannot cover every possible situation - just as pilots must do with the regulations governing operating of aircraft. I'm sure there are "conservative" and "liberal" mechanics in this respect. I respect the spectrum and try to be careful, but I don't lie awake at night worrying about it either.

I agree with your "it depends" assessment. As another example similar to yours, one of the tubes for the elevator trim system in our airplane runs through a nylon grommet, and is subject to wear as described in Service Bulletin M20-185. On the first annual after we bought the airplane, our A&P/IA inspected this tube and found it worn beyond the limits described in the SB. The SB (not an AD) prescribes replacement of the tube, but the mechanic had the tube built up with a weld instead, per techniques described in AC 43.13. He judged this satisfactory because the tube isn't subject to bending or tension or compression loads, only torsion. It was significantly faster and less expensive than replacement. Another Mooney owner I spoke with about this insisted it was an "illegal" repair, but there's simply no basis for that position. Service bulletins aren't mandatory, so replacement of the tube isn't mandatory. The mechanic used approved data from AC 43.13 to make and sign off a repair he believed adequately addressed the problem, which by definition makes the repair legally airworthy. It's fine to debate whether it's a good idea vs. replacing the tube, but it's not "illegal". (For what it's worth, that repair was made 14 years ago and has held up just fine - including a detailed inspection just this year when we overhauled our trim system).

First photo definitely looks like rust on steel components. The others are harder to tell. I've taken various control rods out of our airplane over the years that looked awful in-situ, but that turned out to be nowhere near as bad as I feared. Sometimes, discoloration is just "gunk" - build-ups of dirt, grime, lubrication, etc. Where there is actual corrosion, it's sometimes just "light surface corrosion" that can be cleaned and repainted with minimal trouble once the rod is completely out of the aircraft. Scotch-brite or similar abrasives as others above have suggested. Even if there's pitting, it's not necessarily a deal-breaker. The parts in question can be bead blasted and repainted per techniques in AC43-13 Chapter 6, if they're not "bad". But defining "bad" seems complicated to me, and maybe just boils down to the mechanic's judgement. The oft-cited ten percent wall thickness is a reasonable standard, but note that AC 43-13 and the infamous Mooney SB 208 use this with respect to structural steel tubing, which is not the same as control pushrods. Our own very experienced A&P has been known to look at discolored spots here and there and say things like, "Well, yeah, that might rust all the way through in another 50 years or so. You don't need to do anything about it this year." This used to make me more nervous until I pulled and cleaned and carefully inspected a few such rods. In our case there was nothing of concern, but I don't mean to be cavalier about it - I still think you don't really know until you look closely. In summary, I'm not sure "horrified" is an appropriate reaction by your mechanic. I don't think you were in any particular danger flying this airplane the last year. But it would probably be good to pull the rods out of the airplane and have a close look at them. Odds are they won't require anything other than cleaning, paint, and new AN hardware. Not particularly expensive in the grand scheme of things. Just the thoughts of a pilot and owner who likes to assist with maintenance, though - I'm not an A&P.

Before you disassemble/extract too much to get to the hose running down the left side of the cockpit... you might start by taking out the left (pilot) side carpet panel in the baggage compartment. This is pretty easy and will expose "some" of the tubing, which you can examine for cracks and holes. In particular, you can check if any of the screws holding that carpet panel in place were accidentally screwed into the autopilot tubing. That was the primary source of initial leaking we found when resurrecting our Brittain autopilot. If so, it's possible to patch such holes without replacing all the tubing. If you have a borescope - and from the video above it looks like maybe you do - you can run it down the left side between the skin and the interior panel from the baggage compartment and possibly find other problems, though it might be a tight fit past the roll cage tubing. Good luck with your debug.

Point taken. I guess I don't understand if the "bet" is just for fun, or if he's contemplating ordering parts in advance, or otherwise spending time/money without knowing what's wrong. That's the sort of judgment call mechanics are often pilloried for here, but I suppose it's less of a sin if it's the owner themselves speculating.

Don't bet. Diagnose. It's statistically likely to be leaking servo seals and statistically unlikely to be the poly tubing being "brittle", but that doesn't mean much on any particular airplane. You also didn't mention a couple other possibilities, both of which we found on our airplane when resurrecting the Brittain system: bad seals at the interface between the poly tubing and the servos, and specific damage to the poly lines caused by interior panel screws being inadvertently screwed into the poly lines. There's really no way to know without proper debug and diagnosis.

Concur with your opinion on the side stick. At first it seems nice, and I'm sure there are good side-stick implementations in other aircraft. But the way the control rods are connected makes it feel "springy" in a way that's fatiguing, and also makes it seem like the aircraft is just never quite trimmed for wings level. It's not a pleasant airplane to hand-fly, IMO. The conventional wisdom (snark) seems to be that you don't buy an airplane like that to hand fly it, you buy it to go places, and you let the autopilot do most of the work. I don't actually have a problem with that philosophy, I just don't understand why the control system is designed the way it is. Perhaps there are good reasons for it: tradeoff with the autopilot implementation or whatever. It would be interesting to compare it with the Lancair/Columbia/TTX side-stick implementation, but I've never flown one of those. The cabin and seatbelts are certainly comfortable - on par with automobiles, and stellar compared to most GA aircraft I've flown. Definitely a nice airplane with lots of nice features, and no surprise Cirrus sells a ton of 'em.

Removing the servo from the wing isn't particularly difficult if you're willing to disconnect the aileron rod link. If you do, you can swing the aileron up out of the way, and there's a clever hole right there into which you can insert a socket wrench extension. Leads right to the nut on the back of the servo.

OK, I think I understand the difference of opinion now. People are using the dots by the "Nose up" and "Nose Down" lettering as a reference. Those are not "stops" on the indicator, but anything printed on the indicator can be a reference, of course. It may be coincidentally true that in a particular make and model that's rigged according to the service manual, that the nose up stop is hit at about the point the indicator is next to the nose up dot and vice versa for the nose down dot. If so, then sure, I agree you can estimate whether the takeoff trim setting is correct just based on the travel between those points. Assuming you know one '77J is rigged properly, you can compare it with another, for example. Here's why I think you need to be careful about using this as a shade-tree rule: Eric has a '77J, I have a '76F, and Hank has a '70C. We all appear to have exactly the same trim indicator. It's probably the exact same silkscreened lexan part, with the nose up/down "dots" and takeoff "trapezoid" in the exact same place. Best as I can tell from looking in the parts manual, all three of these models use the same worm gear and "nut" (rectangular aluminum piece) mechanism to control the up/down stops and to set the trim indicator. They all also have the same nose up limit spec: -5.25 to -5.75 degrees. But the '70C has a nose down limit of +1.00 to +2.50 degrees and a trim spec of -1.25 to -1.75 degrees, while the 76F and 77J have a nose down limit of +0.50 to +1.00 degrees and a trim spec of -2.00 to -2.50 degrees. It's simply not possible for these different airplanes to all be rigged properly and have their pitch stops correspond to the up/down dots on the same trim indicator. They can't even have the same range of travel on the indicator, since the '70C must traverse 8.25 degrees of range while the others only traverse 6.75 degrees. By definition, if our airplanes are rigged properly, they can't show the same indication on the indicator at the pitch stops, and therefore at least one of us can't really use the "stops at the dots = takeoff indicator OK" rule of thumb. I don't actually know where the trim indicator stops relative to the up/down dots at the max travel limits on my airplane. But I submit it's irrelevant, except maybe as compared to exactly the same make and model - and even then you'd be inventing a "reference" that Mooney didn't use. More importantly, there certainly isn't any rule of thumb that applies across different models, since they have different stops and trim settings, and in some cases even a different indicator. All that said, it's not like having the trim indicator 1/4" off from where it's supposed to be is a life-and-death event. As has already been mentioned, the optimum practical setting for takeoff varies both with loading and personal preference for control feel. I don't think Eric, Hank et. al have dangerous ideas here. But I hope the details above illustrate why the shade-tree method can give you non-trivially different results than the procedure in the service manual.

We live in a low-humidity area and have been fortunate never to have had problems with water in our static/pitot lines. However, I do press the drain buttons every few preflights just to make sure they're not stuck. The question I have is, how well do these drains actually work? The diameter of the passage with the button pressed in seems so small as to be insufficient to break the surface tension of any water in the lines. In the pitot line you at least have the benefit of a tiny amount of ventilation due to the vent port of the pitot tube itself. But the static system is supposed to be sealed. If I injected a small amount of water in the static lines, I can't imagine it draining out that button drain without somehow pressurizing the lines behind the slug of water. I'm starting to question whether there's ever any benefit in pressing these drain buttons during a normal preflight, or if they're only there to provide an opening when blowing the lines dry from some other point in the system.

I'd have to see a picture of your trim indicator to understand this statement. In my F model, there is no "top" or "bottom" of the indicator window. The window is just a clear section of Lexan, whose only limits are the edge of the Lexan itself. The indicator slides in a channel behind the Lexan. If you disconnect the wire that drives the indicator, you can slide the indicator all the way out of the window in either direction - there is no mark or limit that would tell you the indicator is at the "top" or "bottom". So my concern is you have some shade-tree concept of the top/bottom of the window that's not actually a measurable or defined thing. To be clear, I'm not the kind of guy who says anything other than the procedure in the maintenance manual must be useless/dangerous/whatever. But having recently disassembled the mechanism, I'm convinced your sanity check isn't helpful. Not only are the issues I've already described pertinent, the tolerances are a lot tighter than it seems you may think. Per the maintenance manual above, the permissible tolerance on the incidence settings are only 1/2 degree. This is not the sort of thing you can reasonably estimate by how close the vertical stab is to the dorsal fin, or how far extended the piano hinge is.

Could be due to getting the mains off before the nosewheel, but that's easy to test just by using additional up trim (as others have pointed out, optimum trim position depends on CG) or brute force to raise the nose at a slower - but reasonably safe - speed. What's more interesting is to see if the shimmy is dependent on ground speed, i.e. the rotational speed of the tire. If so, it may simply be a balance issue.

No, that's not a reasonable assumption. The trim "nut" that hits the stops which control the upper and lower trim travel limits, connects to the wire which drives the trim indicator with either a set screw or jam nut. It's entirely possible for this set screw/jam nut to get loose and allow the wire to slip, such that the trim indicator is significantly off even though the travel limits are correct. And there is no measurably defined "top" or "bottom" of the trim indicator window you can use as a reference. The only defined reference in the trim indicator window is the takeoff position mark. You only know the trim indicator is rigged correctly when it matches the takeoff mark at the defined stab incidence. I know getting the travel boards and removing the belly panels to access the mechanism is a pain, but please don't substitute shade-tree methods for the procedure in the maintenance manual. If you have any concern your trim indicator isn't reading correctly, use the correct procedure.

I've replaced several placards on our airplane, and had really good results from http://www.engravers.net Their 0.020 black Lexan with silver text is an excellent match for the factory original placards. I believe the originals were metal, but the Lexan looks the same, and IMO holds up better over time as it's more resistant to dings and bends.

And yes, it technically requires having the elevator travel board to do the job per the maintenance manual. There are other ways to measure incidence if you're clever, but we used a borrowed travel board.

We just went through this on our M20F after replacing the bearings for the trim jack screw. The process for rigging the pitch trim is covered in section 6-4 of the maintenance manual. The trim indicator should match the takeoff mark when the horizontal stabilizer is set to a particular angle of incidence. I've attached the page of the maintenance manual that shows the correct incidence angle, which depends on the model and serial number.

Feel like I should put a bookend on this topic, though there isn't much else to report. Test flight was uneventful with no landing gear issues. Some final notes I recorded about R&R'ing the gear: The best setup for removing the trunion bearing bolts at the rear of the wheel wheel is a 3/8" socket driver, a 6" extension, and a universal joint between the extension and the driver (not between the extension and the socket itself). By far the most annoying bolt/nut to reinstall is the one that connects the gear spring assist bracket to the gear leg. Everything else is a distant second - even the bolt that connects the retract rod to the bellcrank in the belly. There's just no way to get your fingers up above the trunion to install the spring bracket bolt in the proper direction, and no set of pliers in most tool chests with the correct angle to hold the bolt, no matter where you put the gear in the retract cycle. I coulda used a set of pliers with a side (not perpendicular) bend, or maybe an 8-year old with small hands. Pay careful attention to the direction of bolt installation in the parts manual - I got a couple of them backwards on the first pass and had to re-do after a second look. Note that while I've found bolts installed backwards on occasion and think in most cases it probably doesn't matter, there are definitely places where clearance of bolt head vs. nut is an issue. Don't get too carried away with paint quality on the walking beams & retract tubes - it's extraordinarily difficult to reinstall these without a nick or scrape here and there. Take pictures of the squat switch installation before disassembly, as re-installation isn't as obvious as you might think, and the parts manual isn't much help. If you have a 76-ish M20F, remember that some of the assemblies in the airplane are actually found in the M20J parts manual. Hope this thread is helpful to anyone who takes on a similar project.

Sure appreciate all the confessions in this thread, I've made similar errors. Worth remembering if you're ever on the verge of air rage about "that idiot who didn't even make position reports in the pattern!" Might be an honest mistake on their part, and might be you that has the frequency wrong or the audio panel mis-set or whatever.

I can agree with this concept for recent airframes, e.g. comparing an SR22 G5 (0-5 years old) against an SR22 G3 (5-10 years old). When every specimen is multiple decades old, I don't think it holds water. After a certain amount of time, condition is independent of calendar age. To pick an absurd example, shall we also agree the Wright Model E is less expensive to maintain than the Wright Flyer? After all, the former is 10 years newer!

Some of this is arguably accurate, some of it is arguably hogwash. I submit there is no meaningful difference in airframe age between the vast majority of F and J models. The very newest J models were made 20 years ago, and most of them are over 30 years old. That's more than enough time for ham-fisted mechanics to strip nut plates, scofflaw owner to ignore hoses and brake replacements, fuel tanks to leak and not be patched or resealed, etc. Amongst airplanes that are actually for sale, I'm confident you'll find roughly equal numbers of good and bad specimens of each flavor. As others have mentioned, the oil change thing is dependent on the specific F model. It takes approximately 5 minutes to de-cowl later F models for an oil change: about a dozen cam-locs on each cheek panel, 6 screws and a few more cam-locs for the top. In contrast, some of the structures on all J models are more trouble to deal with than those on any F model. Recessed inspection panels, sloped windshields with no access to avionics, gap and hinge seals, inner gear doors, etc. are all nice aero mods, but require more effort to work with. Prop spinner backplates on the J are more fragile, and while there are fewer screws involved, the one-piece belly has its own issues with wear-and-tear, particularly with requiring two people or some sort of jack/prop/assist to remove it without cracking it. I sure hope J model owners aren't using the lack of an AD to ignore lubricating rod ends. This is good practice on any airframe and is specifically called out in the J maintenance manual as a 100-hour requirement. Can't argue with the complaints about flap pumps, but the J isn't immune to the parts-made-of-unobtanium issue either. No-back clutch spring kits for the J model gear actuator were essentially impossible to find for a number of years. The "siamese" Magneto on the Lycoming A3B6D engine variant is somewhat unique to the Mooney M20J, and while I don't have any particular safety concerns about flying behind one, I'm not sure it's a good parts bet for the next 20 years vs. more conventional mags. None of this is meant to suggest the J isn't a great airplane. It is, which is why it commands a price premium in the market vs. the F. But don't kid yourself that the purchase premium is somehow offset by cheaper maintenance costs. jetdriven is a smart guy and makes lots of good contributions here, but I just can't agree with his opinion on this. You're not going to save money maintaining a J vs. maintaining an F.

This is an electric gear model, not manual. Nose gear rigging is measured by travel delta from unloaded to locked. Ours was roughly in the middle of the 0.030 - 0.070 range for ITT actuators. Everything in the system is connected, so I understand how changes to the main can affect the nose and vice-versa. But ours didn't change much. As for "higher is better", I would not have adjusted the mains toward higher preloads if they were already in range, even at the low end. But two turns of the rod ends was below the minimum limit, so I went with one turn even though it's on the high side.

Finished the basic reassembly this morning, next up was rigging. I was unsurprised to find the rigging way out of spec. When we checked last year, the preload torque in the down-and-locked position was right at the minimum of 240 in-lbs. With the new bushings and everything tightened up, I measured the torque at 360 in-lbs - way above the max spec of 280 in-lbs. This makes sense. Taking the slop out of the links effectively lengthens the mechanism, resulting in more force on the springs. I wound up turning the main retract rods in (i.e. shortening them) one full turn. As others have observed here on Mooneyspace, measuring gear preload isn't exactly the most precise of procedures, particularly for electric gear. It's not that the instructions in the manual aren't clear, but in practice there are several challenges. The first is the instruction to take a torque reading "the instant the joint begins to move". This is pretty subjective. You can eyeball it, or try to do something scientific like catching a sheet of paper in the interface and watching for it to fall. But both of those methods seem to have a lot of variation in repeated experiments. The second is the torque reading itself. I have access to both beam-type and click torque wrenches. With the beam type, it's difficult to look at the gauge and the motion of the links at the same time. The clicker is a little better, but the "click" itself tends to nudge the links into motion. Next, as the manual mentions, preload varies depending on whether the gear is extended manually until "the moment the gear down light illuminates", vs. being extended electrically. The manual says to check after manual extension, but even that varies from iteration to iteration. Finally, there is the issue of the rod ends only being adjustable in atomic increments (half turn or full turn, depending on whether you're willing to reset the stops). In the end, I found that with full turn increments, one turn in resulted in an average torque right at (a little over if I'm being honest) the max limit, while two turns had an average torque below the lower limit, so I left it at the higher setting. I'm comfortable with this because the bungee springs are nowhere near "bottomed out", and the collective wisdom in the shop was that it's better to be a little on the high side vs. the low side. Cycled the gear up and down several times and pleased to say everything seems normal. Still need to install the mud guards, clamp/zip tie the hoses and squat switch wiring, and reinstall the wheels (new tires are on order). But I can finally see light at the end of the tunnel.

Nah, you need to read the rest of the thread. The bolt is the one spec'd in the parts manual, and matches the measurement tolerances for said bolt. The whole design is an "as required" arrangement that varies from hand-build airplane to hand-built airplane. A longer bolt obviously wouldn't work, and a shorter one wouldn't have the required shoulder length. There's a reason the shims behind the baby shoe bracket are spec'd "as required" rather than a specific size.

Coming back together. As usual, more blood, sweat and tears (and cursing) trying to get all the bolts and nuts back on vs. getting them off. Particularly frustrating today trying to reinstall the bolts and nuts for the rod ends inside the belly. There just isn't any room in there to work with. I must've dropped and fished out nuts and bolts a dozen times over the course of several hours... It's also essentially impossible to get everything reinstalled without scuffing up the new paint a bit, but it still looks 10x better than before.

No, see my post above about which side the head goes on.