Vance Harral

Thanks to all for the replies so far. I'm open to suggestions on a different lubricant. The official maintenance manual isn't helpful here, as this is one of those cases where the 1976 F was actually designed with some J-model parts. The yokes and shafts in our airplane are factory original (as far as I know from the logs). Hence AD 77-17-04 still technically applies by model and serial number, even if it's arguably unintentional. The F maintenance manual calls for powdered graphite lubricant on the "control column bearing ball", but our airplane doesn't have a ball at that spot like the older models do. The J maintenance manual calls for Triflo (teflon) spray, which I'm willing to try. I confess I assumed there wasn't much difference between Triflo and garden-variety silicone spray, but perhaps I'm mistaken. As for lubricants that last "a long time", my general rule of thumb is heavier lubricants (more oil/grease content) last longer, but they're also more prone to gathering dirt and dust. I've considered trying something like LPS-1 or LPS-2 on the yoke shafts, but I just don't want oily stuff around the interior. Sooner or later it gets on your fingers, then on the upholstery, then on the avionics screens, etc. But again, I'm no expert here - open to suggestions. The thing is, we've been using silicone spray on the yoke shafts per mechanic's advice for over a decade, and this problem has only cropped up in the last couple of years. That's what makes me think the block is wearing.

In photo 1 below, the red arrow points to the phenolic block which supports the right side yoke shaft, just aft of the panel. It's mounted to the steel tubing that also holds the instrument panel itself. Photo 2 is a shot from many moons ago during an avionics upgrade, which shows the block a little more clearly (in the red circle). Periodically when moving the elevator during preflight inspection, the yoke shaft "chatters" in this block. It's been doing so for a couple of years now. When it does, we break out the silicone spray, use it to lubricate the yoke shafts, and the chattering goes away for a while. But it always comes back. At one point I took a close look and found what's arguably a little excess play in the block. As far as I know it's original equipment, and I suspect it's worn a bit over 40 years of service. This seems to be a likely root cause of the chattering. So I dutifully ordered a new phenolic block from LASAR to replace it. But the mechanic and I gave up on the job when we discovered there is (apparently) no way to do so without disassembling the instrument panel, like in photo 2. If I had a time machine, I'd certainly go back and replace it during the avionics upgrade! Has anyone figured out a way to replace these things easily? It's simple enough to unscrew the block from the steel tubing, but then you just have a loose block which you can't slide off the shaft. It won't slide off the back end due to the control linkage welds. It won't slide off the front end (after removing the yoke) because it won't fit through the hole in the instrument panel. I think some year models have a bigger hole in the panel here - maybe ours could be dremeled out as a minor mod? Or I guess we could just wait for the next avionics upgrade, but that's likely a long time away. Anyway, this seems like the kind of thing someone has a clever solution for. Any experts out there? Alternatively, is there a different cause/fix for the chattering problem? I was just guessing a new phenolic block would fix it, I don't really know that for certain. The yoke shaft itself is in good shape (recent inspection per AD 77-17-04), and I'm confident it's binding at the phenolic block, not anywhere else in the linkages. I suppose it's possible there's just dirt and grime in the block, and the play would otherwise be OK without it. But I'm not sure how you'd clean it out without causing more problems than you're solving. Any tips or advice would be appreciated.

Yeah, the nut plates are spendier, but fortunately it seems the screw is usually the cause of binding vs. the nut plate. I like the washer idea, but I confess we don't bother with it. A lot of that has to do with the paint on our airplane being pretty old and beat up (still looks good from 50' away!). The paint is already worn away under the screw head on most of our panels. I'll probably feel differently about it if we ever get the airplane prettied up with fresh paint. For all you guys with less-than-pristine cosmetics, there's a certain luxury in not having a showpiece when you're in the maintenance hangar. I'm able to get inspection plates and belly panels off a lot quicker, since I don't have to be quite so paranoid about the occasional paint scratch from a slipped bit. It's been nice to learn screw-craft on a less-pretty airplane. After 12 years of owner-assist annuals, I like to think I've reached the point where I can make pretty good judgement calls on where I can use drill drivers vs. breaking out the hand tools, when I need a new bit, etc.

Thanks for the great info, Steve (and danders). The labor doesn't look too bad, especially with some owner-assist grunt work. I like to do as much of that as possible, and I have a mechanic who's amicable to that. But I also have a day job, so my DIY work typically has to be carved up into 2-3 hour chunks. Makes it a little harder to commit to bigger jobs, just due to the total downtime if things stretch out. That's actually our biggest barrier to a "no apologies" overhaul of the gear hardware. As a partnership, we have a general obligation to try to minimize downtime, so everyone can fly. Not that we skimp on maintenance, but the partnership results in a reasonable and appropriate amount of "if it ain't broke don't fix it" pressure. We take a certain pride in the idea our airplane is a work (fun) horse, not a showpiece. Congratulations on having chosen an airplane in the optimum serial number range. We're pretty far across the country from each other, otherwise I'd suggest a 1976 M20F meet-up this year! Maybe we still should - we have airplanes at our disposal, after all...

That looks great, Chupacabra. Can you and/or deanders share the approximate hours of labor involved (which I'm sure is the bulk of the cost, not the paint/alodyne)? I know it's "a lot", but would like to get an approximate number to use as a basis for discussion with my airplane partners.

I agree, the value is in the information, not the media on which it's contained. But it'll be tough to get to full-value acceptance of digital copies, because value is market-driven, not mandated. After all, the regs already allow you to discard most of the information typically found in an airframe logbook. I think there are likely to be curmudgeons for some time who think a digital copy is somehow more subject to shenanigans than paper, and/or that a lack of paper demonstrates a lower standard of care. Even buyers who don't care either way may want to protect themselves against said curmudgeons when they sell in the future. Hence there's value in paper logs with respect to sales price, or at least to the number of buyers willing to consider the aircraft. As for me, I'm not sure why curmudgeons think paper forgeries are more difficult than electronic ones. But I'm not going to discard our paper logbooks just to stand on principle. [Note: all due respect to curmudgeonry, I'm occasionally a curmudgeon myself. ]

I've always wondered about this. If I understand you correctly, the paint shop didn't remove the trusses, but rather painted them in place? Did they strip the old paint off first, or just "scuff and shoot"? Seems like it would be difficult to paint the gear in-situ, without getting paint into all the moving parts.

We keep our log books in a plastic case, on a shelf in the (locked) hangar next to the airplane. The shelf and case protects them against a minor rain leak. The assumption is any event which destroys the logs in a locked hangar is likely to destroy the airplane, too. Seems reasonable enough for a 4-person partnership and a $55K airplane. I might be more paranoid if I was the sole owner of a late-model Acclaim. I make digital copies of the logs after every annual, and occasionally between annuals if significant work is done. These get backed up to a cloud service I can access from anywhere, which is convenient and useful. It also provides a backup should something happen to the paper log books. Most aircraft owners I know keep digital copies of their logbooks as a backup, which is certainly good from a practical standpoint. I've always wondered what it means from a value standpoint, though. Most buyers will deduct substantial value for anything other than "complete" logs, and some won't even consider anything less - even on a 50-year old airplane (a little silly IMO, but to each their own). As such, I've always wondered about the value of digital logs. Not sure how the typical buyer would respond to an ad reading something like "complete logs available in digital form, paper logs available for last 2 years".

We went to all SS screws a while back and I do notice they occasionally bind up going in or out, even when new. But I always assumed it was just a random thing, not particular to SS screws. Certainly no worse than dealing with a corroded cad-plated screw. In practice, these bind-ups aren't a big deal. I've never had one bind up so badly I couldn't remove it easily with a good hand screwdriver (well, not including a couple of "pilot errors" where I cross-threaded the screw). We made a project a couple years ago of replacing all the inspection and belly panel screws with new, correct hardware. Ever since then, we've kept a little bin of fresh screws and nut plates readily available. Any time a screw binds up or cams out, I just replace the screw and/or the nut plate with hardware that doesn't bind. We probably wind up replacing a dozen or so screws per annual, for trivial effort and cost.

Lots of variation depending on year model. I think it's most useful to compare the first year of the J (1977) to the last year model of the F (1976). The cabin, interior, and instrumentation between these two models are identical, right down to the quadrant throttle. In fact, some of the minor hardware on our 1976 F is actually represented only in the J parts manual (e.g. the door latch mechanism). But the J has an impressive set of airframe drag reductions vs. the F: more sloped windshield, improved cowl design, and various scoop/seal changes most people agree improve looks as well as performance. Combined with a minor change in the engine/prop combination, the J cruises 10-15 knots faster than a similarly loaded F, and commands a commensurate price premium. It's about 1 AMU per knot of cruise speed, same as most speed mods. :-) The further apart the year models get, the more variation you have in engine, gear and flap systems, cabin size, etc.; as well as cost. I'm not sure it's useful to generically compare "J-model vs. pre-J model". Too much variety for a short discussion.

If it helps any, here are some specs on our 1976 M20F, which does have a Garmin GTN 650, but no ADSB solution yet: http://www.harral.net/aviation/N7028.html Every year we meet as a partnership, look at comps, and decide what we think the airplane would sell for. The airplane is not for sale, but we do this to establish a value for insurance, as well as a value to use should one of the partners decide to exit the partnership. We had our annual valuation meeting just a couple of weeks ago, and the number we came up with was $55K. The airplane has "average" paint and interior, and a runout engine for valuation purposes (over 1800 hours SMOH).

On a related note, I'm seeking advice about inspecting/cleaning/painting our main gear trusses. As shown in the attached photo, they're filthy, and the paint on them has significant cracks. The dirt and cracks in the paint could easily disguise cracks in the trusses themselves, which concerns me. I've asked a couple of different mechanics about it and all they do is probe a few spots with a dental pick, sign it off, and tell me it's extremely unlikely to be a problem. The no-apologies fix would be a full rebuild and powder coat as deanders is doing, but that's arguably excessive for a '76 model with only 2800 hours that's almost always been hangared. I also found this site, which suggests the trusses can be sanded, cleaned, and repainted in-situ: http://www.mooneyland.com/say-no-to-ugly-legs/ At our upcoming annual, I figure at bare minimum I'd like to really clean the wheel wells and trusses with a solvent and/or pressure wash, but not sure if that might have adverse affects. I've had it suggested by knowledgeable mechanics there's such a thing as "too clean" for moving parts exposed to dirt and dust - that the film of oil and grease actually helps keep grit out of spaces where it can do damage. All I really know about the trusses at this point is they look ugly. Would like to hear what others do in the way of care, maintenance, and inspection.

We got a new steering horn assembly from LASAR 2.5 years ago, which, along with new rod ends, eliminated an ongoing nosewheel shimmy problem. This was the "final" repair after first trying checking nosewheel tire pressures, then checking nosewheel alignment per Service Bulletin M20-202, and even installing a new LASAR bushing. Only the new steering horn and rod ends solved the problem. Haven't had an issue since, in hundreds of takeoffs and landings. Note that LASAR actually sells three different steering horn assemblies. I call them the "factory early" model, the "factory late" model, and the "LASAR PMA" model. You can see the factory early/late model steering horns in this photo: http://www.lasar.com/mod-details.asp?id=30. The late model is the beefier one on the bottom. I'm not sure what year Mooney switched from the early to late model, but our 1976 M20F already had a late-model steering horn, which we replaced with the same part. Older models can be upgraded to the late-model horn, but it requires modification of the tubular structure in the nose wheel to which the horn attaches. My understanding is it involves grinding/welding/drilling. LASAR also advertises a PMA-approved replacement horn, which you can see here: http://www.lasar.com/mod-details.asp?id=20. At the time we were buying, LASAR steered us away from that one. It wasn't clear to me if they were having problems with it or just didn't have any in stock.

The math above gives you an average acceleration of 7.59 ft/sec2. That doesn't mean the airplane is accelerating at a constant 7.59 ft/sec2 throughout the takeoff roll. Again, you're using a constant value for "A" in your V=AT equation, but in reality the value varies with time. The correct math would integrate A as a function of time rather than treating it as a constant value. Doing that requires you to know how A varies with time, which is a complex equation. But as Carusom says, acceleration in cars and piston airplanes generally decreases as velocity increases. Using a fixed value of 7.59 ft/sec2 is giving you an optimistic answer of a 19% increase in ground roll for a 6 knot tailwind, when the reality is closer to 30%.

No, acceleration isn't linear. As noted in my Cessna POH example above, a 6 knot tailwind - which is about a 10% increase in rotation speed - results in a 30 percent increase in takeoff roll.

The effect of a tailwind is much larger than many people think at first glance. The takeoff performance charts for a Cessna 172 indicate takeoff distance decreases 10% for each 9 knots of headwinds, but increases 10% for each 2 knots of tailwind. A more general rule of thumb states that a tailwind which is 10 percent of the takeoff airspeed will increase the takeoff distance approximately 21 percent, and that matches the 172 with a normal takeoff rotation speed of 55 KIAS pretty closely. A Mooney will be a little different than those numbers, but not substantially so. My M20F POH shows a ground roll of 834' at gross weight, sea level, standard conditions. If you apply the 172 numbers with 6 knots of wind, that becomes 778' with a headwind, but 1084' with a tailwind - a difference of 300'. But as mentioned above, the climb gradient in ft/nm once you take off also suffers. If you're trying to get over the canonical 50' obstacle, the delta is closer to 500'. That's with a 6 knot wind, which a lot of pilots would consider "light and variable". You can do the numbers yourself with 10 knots. All that said, I don't think your downwind takeoff was "unsafe", since the intersection upwind takeoff is close to a wash at sea level on a standard day. Good to know the turn radius, though. 41 feet is a little more than one wingspan, so that's one reference point to understand the turn radius while taxiing.

I'll add to the chorus of those who say a wet rate works better than you might initially expect. While it's true different partners might fly the airplane in such a way one uses less fuel than another, those differences tend to be on the order of a few dollars and hour, and lost in the noise of other airplane expenses. If you try to "fix" this by renting dry and having everyone pay for their own fuel, the "fill it up" rule turns out to be a pain from time-to-time. Fuel pump at the home drome temporarily out of service? Long line at the pump? Tough luck, you have to hang out until it's ready, or return to the airport later and taxi back to the pump before anyone else flies the airplane. Want to take off with less than the standard fuel level to accommodate more passengers/baggage? You can't ask your buddy to skip his refuel unless you write him a check. If you fly together and split the time, you either have to run the pump twice or one of you has to write the other a check. Get an emergency message in flight? In a wet-rate partnership, you could skip the fuel-up, put the airplane away with 30+ gallons in the tanks, and no big deal. Of course, it's not a big deal in a dry rate partnership either, if everyone is reasonable, it's just more of a pain. The paramount issue isn't how you pay for gas, but rather respect, reasonableness, and an eye toward the big picture. I don't need to make every penny come out in my favor, and I wouldn't want to partner with someone who's going to gripe about a hundred dollars of differential fuel expenses over the course of a multi-thousand dollar year of aircraft ownership.

I think the '67 is worth a look. Seems good on paper, priced to sell, and it's listed on many different for-sale sites, which suggests a motivated seller. First question I'd ask is how many hours it's flown recently. The low-time engine is attractive, but only if those 93 hours have been put on in the last couple of years.

I think the '67 is worth a look. Seems good on paper, priced to sell, and it's listed on many different for-sale sites, which suggests a motivated seller. First question I'd ask is how many hours it's flown recently. The low-time engine is attractive, but only if those 93 hours have been put on in the last couple of years.

I expect one of our turbocharged brethren will be along shortly with a different opinion. I understand the appeal of a vernier throttle in turbo'd engines, particularly like those in the original 231 with the fixed wastegate. In the absence of a perfect upper-deck pressure controller (and even the later -MB engine and the aftermarket Merlyn mod aren't perfect), it can be tough to avoid "bootstrapping", and the vernier throttle helps with that. The one guy I know well and fly with regularly in a 262 conversion seems to like his vernier throttle. As with push/pull knobs vs. throttle quadrant, I'm sure it's something you get used to relatively quickly. I just don't have a lot of experience with them, particularly sitting in the right seat.

Nothing wrong with verniers and digital readouts, provided they're used appropriately. It's not so much about having a "better feel" for the airplane as it is knowing when precision is important and when it's not. As an instructor, I occasionally see pilots with these setups fly head-down in the traffic pattern or lose their scan on an IFR approach, because they're e.g. fixated on an MP gauge that reads 15.3" which they think needs to read exactly 15.0. In the first place, they're confusing precision with accuracy. But more importantly, they're spending too much energy on things that aren't important in that phase of flight, to the detriment of safety. Not saying this is something you do, carusoam, just intended as a general comment. This is a good example of precision vs. accuracy. No piston engine tachometer is accurate to within 10 RPM, despite some tachs having 10 RPM precision. If a digital tach reads 2550 RPM, the prop isn't actually turning exactly 2550 RPM. So it makes no difference if it reads 2540 RPM instead, especially in a high workload situation. This isn't something that's meaningful to "fix". To be clear, my point isn't to disparage vernier controls or discourage precision. It's useful and fun to set the controls as precisely as possible in cruise and try to exactly match book performance numbers, and vernier controls make that easier. But cruise is the time to do that, when you have plenty of spare brain cycles and low probability of traffic conflicts. When things get busy, a different approach is better. It's the difference between "give the throttle vernier three CCW twists every 1000' in descent" (good) vs. "maintain 21.0 MP throughout the descent using the vernier throttle" (not so much). I do have a love/hate relationship with vernier throttles, at least the common type with a push-button to disengage the vernier. I like to be able to easily and quickly add or subtract just a tad of power in the flare when necessary. Seems very awkward to do this with a push-button vernier throttle, but maybe that's just due to minimal time making landings in such airplanes. My understanding is there are aftermarket friction verniers that don't have the push knob which I think would be better for throttle control, but I've never actually laid hands on one.

We have a '76 F with the quadrant. I was indifferent when we bought the airplane, have no complaints about it 12 years later. I agree it's easier to make fine prop and mixture adjustments with a vernier, and that might be particularly helpful in a turbocharged airplane prone to "bootstrapping" behavior. On the other hand, go-arounds are simpler with the quadrant, and I've grown to like it in our normally-aspirated airplane. For what it's worth, I don't have any particular trouble adjusting the prop within 50 RPM or fuel flow within 0.1 gph. I rest the heel of my hand on the quadrant frame, and ever so slightly nudge the control, then wait (the patience requirement is the same regardless of vernier or quadrant). I won't say it's as easy as fine control with a vernier, but it's not particularly difficult, either. Fine adjustments are only needed in low-stress situations anyway, almost always after you level out in cruise.

Bear in mind those speeds are based on a level turn which necessarily requires greater than 1G of load. That's a little different from the descending, approximately 1G turn typically flown in the pattern. Not saying your caution in unwarranted, of course, just that descending turns in the pattern aren't exactly the same scenario used to produce that table in the POH.

This statement suggests a certain lack of finesse. I can vary descent rate by varying the amount of rudder used in a slip, it's certainly not "full rudder or nothing". Much easier and quicker to adjust vs. changing flaps or power, too, though I tend to avoid that technique with passengers who aren't pilots just due to the funny look and feel for them. To be fair, your J has less drag than my F. But I've seen light slips used in everything from Cubs to TBMs. I wouldn't teach "full rudder or nothing" in any airframe, whether draggy or slippery. Generally agree, though cavalier statements like "nothing to worry about" always give me pause. Prefer to just say that the amount of backpressure required to induce a stall from a slip while trimmed in the landing configuration is, well, "impressive" in my F model. Let's not muddy the waters - whether the aircraft is climbing, level, or descending is irrelevant. Only AOA matters (as you've pointed out in many threads). Again, agree you're very unlikely to have problems without significant pulling on the yoke.

You can stall a Mooney in a slip, causing an incipient spin. Full stop, end of story. Been there, done that (under carefully controlled circumstances as part of CFI training). There is plenty enough rudder and pitch authority to do so. What's being discussed in this thread is how likely you are to enter an inadvertent, cross-controlled stall from an intentional slip on final, and how difficult the recovery would be. The answers are, "not likely", and "less so than from a skidding stall". Exactly how "likely" you are to stall while slipping on final is hard to quantify. But I certainly wouldn't hesitate to use intentional slips on final. Just a moderate slip in descending flight, at a low angle of attack, is very effective in increasing descent rate without increasing airspeed. The difference in control displacement and control "feel" between that benign maneuver, vs. actually entering a cross-controlled stall from a slipping turn, is significant. In my airplane, a slipping stall in a descent requires full rudder to the floor, and an almost unbelievable amount of back pressure (with the airplane trimmed normally for final approach). To me, it feels so far outside the realm of normal control pressures that it's hard to believe anyone could do so inadvertently. But I felt the same way about a skidding stall, and the NTSB reports are full of such accidents, so caution is always warranted. As others have noted, a stall from a slip causes the airplane to roll toward the high wing. By the time you've applied recovery inputs, the airplane is essentially wings level. If you don't apply recovery inputs, you'll eventually enter a spin, but it takes a few seconds. A stall from a skidding turn, in contrast, causes the airplane to roll toward the low wing. You can recover without exceeding 60 degrees of bank if you're primed for it to happen and immediately apply recovery inputs. But if you're not expecting it, I'd wager nearly every pilot will wind up inverted before they have time to register what just happened.