Vance Harral

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.

Great job on being so thorough with your checks. Given all that you've done, the amount of water remaining in the tank may not be zero, but it's almost certainly unmeasurably small. We got water in our tanks a few years back and were concerned. But in the end we didn't do anything other than sumping until the tank and gascolator drains showed no more evidence of water. We talked to an experienced mechanic about it at the time. His take was that a tablespoon or two of water sloshing around in the very bottom of a tank after sumping wasn't going to make the engine quit, even if small portions made their way to the pickup lines. He said you have to pick up a pretty big slug of water for the engine to noticeably quit making power. That still sounds a little cavalier when I put it in writing, and I don't mean to minimize the concern. But it does make some common sense. Water passing through the fuel system isn't destructive by itself, it's just not combustible fuel. How big of a deal it is depends on how much water there is. A few drops that pass through the system in under a second aren't going to ruin your day. A half gallon that takes 3 minutes to flow is obviously a different story.

I haul back on the yoke when crossing major divots on any surface, mostly due to muscle memory from flying several different brands of nose-draggers. But I'm not sure it has much effect in a Mooney. The nose gear strut isn't an oleo like many other airplanes. The amount of tail downforce from full-aft elevator at taxi power and low speed doesn't seem like it would uncompress the nose gear shock disks much, if any. I can't say I've detected any change in attitude from the cockpit in our F model when I move the elevator around at taxi power, but maybe I'm not looking closely enough. Anyone ever actually measured this? Maybe rough surfaces in Mooneys should be treated like speed bumps in cars. Either hit 'em really slow, or really fast!

Beautiful airplane, and they're all great shots. But I think the combination of light, colors, and background scenery are best in #5. I also like how the pilot shows up only in silhouette. Not that you aren't a handsome man, of course! ;-)

For what it's worth, our 1976 F has headrests for both front and back seats. Like your airplane, ours does not have a split rear seat, just the single rear seat. Here's a picture of the rear seat with the headrests: http://www.harral.net/photos/Jalbums/N7028/slides/i.html The front seats are separated, of course, but the headrest design is identical. The headrest itself is nothing more than a U-shaped aluminum tube onto which you slide a cushion. The receptacle in the seatback is just a pair of slightly larger diameter tubes which the headrest tubes slide into. In our airplane, the receiving tubes don't stick up past the top of the seatback. There is just a pair of little holes in the upholstery on top of the seatback, with the receiving tubes slightly below the cuts in the fabric. If some previous owner lost your headrests (or they were never installed to begin with), it would be easy for an upholsterer to cover the place where they go, either on accident or on purpose. I expect there's a good chance your seats have the receiving tubes, and they're just covered over. If you press down firmly on the top of the seatback upholstery, you might feel the top of the receiving tubes. Then if you're brave, you can cut through the upholstery to verify.

While engine management is a significant issue, there are a few more mundane differences that are important to note. One I was a little surprised by is the different sight picture in the flare due to the longer nose. The difference in length from the pilot seat to the nose of the spinner between an F and a K may not be that significant in measured inches, but it just looks different to me in the flare.

Concur. The idea that aviation insurance companies nitpick trivial maintenance issues as an excuse to to deny claims is a myth. For further insight, here's a paper on the subject from Avemco: https://www.avemco.com/Articles/ART0006-2011.pdf Their claim denials are for issues any reasonable person would agree are legitimate: pilot not approved on the policy, in-flight claim on a policy with no in-flight coverage, etc. Avemco is just one aviation insurance company, but the market is small (lots of agents, but not many underwriters). If any company was nit-picking claims, word would get around quickly. Disclaimer: haven't been an Avemco customer for many years and have never had an insurance claim. Not trying to shill for Avemco, just doing a little myth-busting.

For the sake of closure... I satisfyingly/unsatisfyingly report the fuel selector has not resumed its leak in the last week, including through a couple of cautious flights kept to the vicinity of airports. Everyone's best guess is the strainer simply didn't seat properly at one point, either due to a small piece of debris which has been flushed out, or a slight "edge" in the mechanism somewhere that has been scraped smooth or just usually doesn't catch the moving parts. If the latter, the problem may return. But the risk of doing nothing at this time seems less than the risk of a maintenance induced failure R&Ring a critical part which is not actually failing in any observable way at this time.

Since you specifically asked... First, the sample size of contributors on Mooneyspace is almost certainly too small to be meaningful, especially since respondents are self-selecting rather than random. That's the biggie. But even if we set that aside, you should be interested in failure rate per hour flown, not per pilot. In other words, kpaul's "vote" based on 5000 hours should count 5x that of someone with 1000 hours of exposure, and 50x that of someone with 100 hours. Next, the poll doesn't separate pilot experience from equipment flown. If your poll shows zero failures for "airfoil shaped probe sensors", that's much more likely to mean none of us have flown with such a device than to mean those devices are ultra-reliable. On a related note, some of the technologies you mention are so new there's simply no meaningful failure data for them yet, at least not in the GA fleet. Finally, since your poll doesn't allow one to select multiple options, it can only be meaningful if all the options are mutually exclusive. You have multiple overlapping choices, and that distorts the data. I'm sure some people are going to read this as the nit-picking rant of a pedant. But data gathering and analysis is a pretty sophisticated science, requiring significant effort to get right. The way you've constructed the poll suggests you don't understand it very well, and I cringe at the idea that you think you're going to get meaningful data from it. If I come off as a grumpy old man who happens to have taken some graduate-level statistics courses that most people don't care about, well, that's just the risk of posting on the internet. To the extent people share anecdotes of particular failures like I did, I think that's helpful to everyone. I don't want to be a jerk about you starting the thread - anyone is free to contribute, of course. But please don't draw any conclusions about the reliability of various AOA technologies from your poll. It's not meaningful.

I'm not inclined to vote in the poll because I don't think it's well designed and I suspect you have a preconceived agenda. But by way of anecdote, I've had the vane-type stall warning sensor fail in our M20F. Went up to practice stalls and was able to go all the way to the break without the stall warning going off on the first attempt. It operated normally on subsequent attempts, as well as back on the ground. Possible failure modes include the vane being stuck and not actuating the switch, or the vane moving but not making good electrical contact. I suspect it was the latter. Failure of electrical switch vane sensors is not an uncommon problem, and a shot of contact cleaner sprayed into/around the vane is the typical advice. We do this as a matter of course at every annual, but I know from experience the device can still fail. Ideally, a pilot makes use of all available information, including control feel, airspeed indicator, and stall warnings and AOA devices if so equipped.

Swapping probes is always reasonable, but that sawtooth pattern looks too small in amplitude and and too regular in frequency to immediately blame on a bad probe or connection. Politely disagree with carusoam that the thermal mass of the cylinder doesn't allow for such fluctuations in real life. If I'm reading your graph correctly, the variation is only 20-30 degrees, spaced over 2-3 minutes. That is quite possibly a "real" CHT change. Recommend you sift through the monthly puzzlers on the Savvy Analysis site, where they show a graph each month and explain the root cause. I just spent a little time looking there, as I think I've seen this sawtooth pattern before, but I was unable to find an exact match.

Thanks for the advice, all. In the usual way of "the broken appliance doesn't malfunction for the repairman", we're unable to see any leaking this morning. :-| This of course doesn't mean the unit doesn't need a rebuild, but it could also mean the strainer pull shaft simply got slightly stuck open on the last preflight. Advice from the mechanic is to let it sit a while and see if the staining returns. Letting it sit on the ground a few days is a pretty low-risk maneuver while we mull over our options.

Actually, I was hoping to avoid that if possible. I'm aware fuel will stream out once the source lines are disconnected from the selector, but was hoping there's a way to plug the lines with just a small amount of fuel loss. Completely draining the tanks would be a pain. Tips anyone?

Scrubbed a flight today due to discovery of a fuel leak around the fuel tank selector/strainer. Got a whiff of fuel on opening the cabin, and discovered a large drop of fuel and a blue stain on top of the strainer stem in the cabin. On looking under the belly, found obvious signs of leaking: blue stains on the strainer drain and nearby panels. Pulled the belly panel and found more blue staining on and near the selector (photos below). I'll be working with our local mechanic on the problem tomorrow, but wanted to solicit advice from anyone who's dealt with this. An article on Don Maxwell's site says, "Fuel selector valve leaks are evident by stains around the fuel selector stem. In most cases these leaks are repaired by disassembling the selector and replacing the O-rings." A prior thread on Mooneyspace discusses having LASAR rebuild the selector, or ordering a rebuild kit from LASAR or Don Maxwell. But that same thread suggests there are multiple causes of leaks, some simpler to fix than others. I've removed the sediment bowl and checked the screen during owner-assisted annuals in the past, including replacing the O-rings there. But I've never removed or disassembled the selector itself, and not sure what other seals might be further inside. My mechanic says he's never pulled the strainer stem in a Mooney, so it's going to be a new experience for both of us. Any advice on what to look for? I'm not opposed to sending the whole thing off to LASAR for overhaul, but we haven't had any of the trouble that typically leads to an overhaul, e.g. difficulty turning the selector valve or pulling the strainer. Just this newly discovered leak. If it's a simple matter of replacing a standard O-ring, that seems preferable to an overhaul. Comments and advice appreciated.

Mostly north up, but track up is fine. I try to be flexible, especially since CFI work and being in a partnership mean I don't always get to choose. I think this has gotten to be less of a deal with modern navigators and iPad apps that make it easier to pan the map relative to your ownship symbol. I was a north-up bigot in the days when track-up put your ownship at the bottom of the screen and it was a lot of trouble to look at stuff behind you (helpful when flying outbound legs and procedure turns on instrument approaches). Here's a trivia question: of those who prefer north-up, how many of you are model airplane pilots? I've always thought people already comfortable with the mental gymnastics of transposing their "eyes" into a virtual cockpit oriented in another direction, are likely to prefer north-up.

The "violent wing drop" is only caused by a stall in the cross-controlled condition. If you don't stall, no wing drop. Again, don't want to give anyone the impression I think a properly executed slip is a dangerous maneuver. Entering an uncoordinated stall during a slipping approach isn't meaningfully more likely than entering a coordinated stall during a normal approach.

While it's true that power+attitude directly influences AOA at the wing, I can't agree with this statement. I'm going to link to the BruceAir video again. The pilot specifically says he is "bringing back the power" prior to demonstrating the spin from a slipping turn. The nose appears level or slightly below the horizon for most of the turn (though I admit it's difficult to tell). But it looks to me like the aircraft enters a spin from a descending, power-off turn, in direct contradiction to your statement above. Now, this is an aerobatic airplane specifically designed to snap and spin easily, and it's fair to point out most GA airframes don't behave exactly this way. But I still think your blanket statement is confusing and not really correct, and that the video demonstrates as much. To be clear, I'm not arguing a power-off slipping turn is a risky maneuver. I see them done all the time in taildraggers without incident. I practice and use forward slips in my Mooney, too, though I choose to wait until the base-to-final turn is complete before doing so. I'll also say my experience with stalls from slipping turns is limited to a few iterations in a couple of airframes, and always involved prompt recovery rather than allowing the spin to develop. That's not a broad experience base, and I can easily believe some airplanes - e.g. a fat, straight-wing Cherokee - might do nothing worse than mush and wobble in a stable, descending, power-off, slipping stall. But that would be a characteristic of the airframe, not a blanket statement, so I feel obliged to disagree with the gist of your post. I'm always learning, comments and rebuttals are welcome.

No, that's not correct. A slipping stall still results in an incipient spin. It's just that the incipient spin rolls you toward wings level instead of away from wings level. Therefore, application of prompt recovery technique results in you breaking the stall about the time the wings are level with the horizon, This makes it easier/faster to level the wings with the rudder, and you don't lose as much altitude. But if you don't apply prompt recovery technique, you'll continue the outside snap roll and wind up in a spin opposite the direction you would spin from a skidding turn. Here's a video that shows a one turn spin from a slipping turn. The airplane snap rolls left, away from the right turn:

Tough to ballpark, we didn't take data and the training was several years ago. I can tell you I remember it wasn't necessary to get right up to the hairy edge of a straight ahead stall with buffeting, etc. before kicking rudder. The instruction I got was to reduce power to idle, raise the nose smoothly to maintain altitude until hearing the stall warning (this particular Citabria was so equipped), then kick the rudder. So the "margin" was at least as much as the difference between the stall warning and the actual stall speed. Given the ease with which we entered spins, I suspect I could have initiated the spin with rudder-only input even several knots faster than stall warning speed. It's helpful to do some guestimate math to get a feel for the numbers. Based on my recollection and looking at some spin vidoes online, the yaw rate in a spin in the Citabria appears to be about 180 degrees per second. It's probably fair to guess the yaw rate you can induce by stomping on the rudder is in the same ballpark as the spin rate, which suggests you can (temporarily) accelerate the wings about 180 degrees per second with a rudder stomp. With a wingspan of 33.5', that means the wingtips have a relative differential velocity of about 53 feet per second when you kick full rudder, i.e. the outside wing is suddenly moving 53 fps faster than it was before, and the inside wing 53 fps slower, for a difference of about 100 fps. 100 fps is 68 mph. That's a dramatic difference in velocity between the inside and outside wing tip at GA speeds, with a commensurate difference in lift. Now, the yaw doesn't cause critical AOA to be exceeded by itself. But the significant differential lift on the two wingtips induces a significant rolling moment, and the resulting drop on the inboard wing is, I'd guess, the main factor which causes the inboard wing to stall. Blanking of the inboard wing by the fuselage as the yaw is established is a contributing factor. And if you try to correct the rolling motion with aileron, it just stalls the inboard wing worse. The video linked to above also discusses the swept wing effect causing the center of pressure of lift to move outboard on the outside wing and inboard on the inside wing. On that, I'll just have to take the gentleman's word. But the point is there are multiple factors which cause the inboard wing to stall deeply and the outboard wing to stall lightly (or not at all). The discussion reminds me of left-turning propeller effects, which are not due to a single factor, but rather caused by a combination of P-factor, spiral slipstream, and in some cases torque and gyroscopic force. I'd guess this is the reason PTK and jetdriven have contrary evidence with respect to evidence of buffeting: there are a lot of factors at play, and you may or may not feel buffeting during spin entry, depending on the airplane, the conditions, and the spin entry technique. I just don't think you're going to get even a ballpark number for this. Too many factors at play: rudder size, travel, shape, rudder moment, how fast/hard your control inputs are, whether you're subconciously inputting aileron as well, your current CG, etc. I certainly don't think you can develop a numeric rule of thumb like "an extra 11 knots of airspeed speed protects me against a skidding stall". Hence the focus on teaching coordinated turns. No disagreement from me on this. Both airspeed and AOA indicators are proxies for "true" AOA (which may vary at different points along the wing). An AOA indicator is a better proxy. But whether this difference in accuracy can actually reduce the stall/spin rate across the fleet is a more complicated question. My guess is that as with motorcycle helmets, anti-lock brakes, airbags, and full airframe parachutes, the safety improvement is undermined to some degree by the human tendency for risk homeostasis.

Concur this isn't a one-axis problem. I'm sure there's some variation in indicated stall airspeed during a stable, constant rate coordinated turn vs. a stable, constant rate skidding (or slipping) turn. But as the linked video discusses, the event that causes the stall may be the movement of rudder or aileron controls at a critical moment, rather than increasing pitch input and/or reducing airspeed. The effective change in AOA caused by the rudder and/or aileron input triggers the stall in these cases. The most obvious demonstration of this to me was my spin training. We performed spin entry in the Citabria by slowing to MCA, then simply pressing one rudder pedal all the way to the floor to trigger the stall and resultant spin, with no additional backstick. In other words, the stall/spin was initiated entirely with yaw input, not pitch input. It generated a nice, crisp entry that I'm sure looks good in competition aerobatics, and was certainly sufficient for learning spin recovery. But I'm not sure it was a good demonstration of the inadvertent spin entry we worry about as instructors. Sure was fun, though! Anyway... this discussion of how much "sooner" a stall occurs in a skidding turn isn't meaningful, IMO. It seems to assume you're in stable skidding turn, with a specific, constant amount of crossed aileron and rudder input, then you ease back on the yoke to the break. You can run that experiment, and in fact that's the way my instructor had me perform cross-controlled stalls. But I don't think that's how most stall/spin accidents happen, at least not in Mooneys. In particular, the amount of elevator backpressure required to induce the stall under those conditions is enormous (I'd estimate 20+ lbs of force, and that's based on being trimmed for a stable 500 fpm descent). You'd think would be a huge clue you're about to cause something bad to happen. On the other hand, if you start out in a coordinated turn, then kick in a bunch of ill-advised rudder and simultaneously apply opposite aileron and just a little bit (or no) of backpressure, I can see a surprise snap roll occurring. Because of this, I'm not enamored of using a steep turn to final to bleed off energy. I understand the aerodynamic argument, and believe it's technically "correct", especially with respect to a descending turn at relatively lower load factor. But much like inducing an accelerated stall from rapid pitch input, one can induce a stall from rapid uncoordinated roll/yaw inputs over a wide range of indicated airspeed and G load (i.e. the fact that you're not "loading up the wing" doesn't necessarily protect you). Not an issue if you "never" fly uncoordinated, of course. But we all make mistakes, and those mistakes are more likely at steeper bank angles. As a specific example from my own bag of experience, I've learned that a coordinated turn in the pattern with a healthy crosswind can give the appearance of a slip or skid, based on ground track. I caught myself applying inappropriate rudder under those conditions once. I was genuinely making an attempt to stay coordinated, but using the wrong reference (my eyes, instead of my butt and the slip/skid ball). It was night time, which aggravated the visual illusion, but I make no excuses. It was a mistake worth noting. I agree with 201er's point that airspeed is an error-prone proxy for AOA. But lest anyone get too enamored of AOA technology, note that an AOA indicator may very well let you down in a slip/skid scenario too. There are a couple of different GA AOA sensor technologies, and I don't know which one 201er has. But to my knowledge, none of of them are designed to account for sudden aileron or rudder input. I'd wager any of the GA AOA devices would be "late" in going yellow/red during a spin initiated by rudder or aileron input.