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Here's one way to think about it. The flow around a finite-span wing far from the ground produces wingtip vortices and a net downwash behind the wing. As the wing nears the the ground, the ground interferes with the flow in such a way that vortices and downwash are reduced. It is as if the wing gains span. The result is that the aerodynamic force vector tilts forward. If we resolve the AF vector into a vertical component (lift) and rearward component (drag) the forward tilting increases lift and reduces drag. Skip

I think you'll find the answer near the end of this:

@Blue on Top makes excellent points ... again Years ago, Flying columnist Peter Garrison made the observation that even a child understands lift. It's angle of attack. They know this by "flying" their hand out the car window. My private pilot ground school instructor used to say that you could fly a sheet of plywood if you had the right angle of attack and enough power. I've come to the point where I think all the discussion of Newton and Bernoulli and camber and such is not very helpful to pilots. We cannot see the air and we cannot change the wing shape (excepting flaps). But angle of attack is something we can understand, visualize and control. The point of airfoil design is to use that angle of attack to generate lift efficiently my minimizing the associated drag. Skip

Try this one. A bit long and I had to watch parts of it several times to understand it (mostly ;-), but I found it pretty interesting. Skip

I'm glad @Cargil48 brought this up because this is an example of the simplifications that we've all been taught over the years that turn out not to be accurate. Here's a wind tunnel video using pulsed smoke that shows clearly what @Austintatious points out. It turns out that there are a couple of other problems with this explanation of lift. Even if you take a highly cambered airfoil (like the Clark-Y) the difference in path length isn't nearly enough to account for the difference in speed of the air over the top and bottom of the wing. Also, if you look at the Mooney root airfoil, it is curved on both top and bottom, so the path lengths are not that different at all. http://airfoiltools.com/airfoil/details?airfoil=n63215-il Skip

Agreed. And, I'm also not convinced that the Coanda effect applies since it refers to a jet of fluid and (as I understand it) has to do with the jet entraining adjacent fluid, so it might not work the same way with a 3D wing. http://thermofluids.co.uk/effect.php. But I understand that Rod was looking for some explanation as to why the air would follow the wing's curvature. I think it's easier to simply ponder, where else could it go? Skip

There all sorts of ins and outs to performance based navigation. The simplest rule is: If it's not in the database, you cannot legally fly it. The GPS manufacturers are required to eliminate approaches for which the equipment is not suitable. Also, the FAA prohibits flying a GPS approach by entering waypoints -- you have to load the approach from the database. Skip

An airfoil (2D) produces lift and drag. If you look at the airflow around it, there is an upwash ahead of the airfoil and a downwash behind it. Mathematically, half the lift comes from the upwash. There is a lot of confusion about lift because of the incomplete and over-simplified explanations (Bernoulli, Newton) we learned in private pilot ground school and the fact that a lot of drawings of airflow around a wing are incorrect. In order to understand lift, it's best to avoid cause and effect arguments. The wing forces the air to go around it. In so doing, there are velocity (speed and direction) and pressure changes. The velocity changes and pressure differences are part of the dynamics of fluid motion, and trouble brews when you try to figure out which causes which. My friend Rod Machado and I discussed this a while back and he ended up making a Youtube video about it. Skip

From a June 23, 2019 post on BeechTalk: I talked to Surefly again last week (sent mine back for an upcoming software update that changes the "wake" delay during mag switching from the current 400ms down to 10ms to minimize some of the risk of backfire/misfire some of them have). Maybe this fixes the backfire problem? Skip

From FlightAware's FAQ page: What is a position-only flight? A position-only flight is a flight for which FlightAware has not received a filed flight plan, for example a VFR flight. In those cases, if we receive position reports via ADS-B or another source, the flight can be trackable as a position-only flight. Note that position-only flights are by nature less accurate, since FlightAware has not received a filed origin, destination, or route, and the aircraft may enter and leave areas of coverage throughout the flight.

If you click on the NOAA link, you’ll find a notice that the product is discontinued.

On my current ‘94 J, the stall strips appear to be at the same location vertically and it stalls wings level with very little roll off. Years ago, I owned a ‘78 J and the stall strips were obviously in different vertical locations and it had a pretty abrupt roll off. I always wondered if they were positioned at the end of the day on a Friday before beer call Skip

I used to fly a club '64 M20C N78888. Used the radio call "seven-eight triple eight" and it always seemed to do the trick. Also flew an Archer N222XT and used the call sign "triple-two xray tango." I kind of liked the repeating triple digit numbers. I flew another plane that ended in echo whiskey and that was always a bit of a tongue twister for controllers. I often wonder how the controllers remember the Canadian ids as in: Charlie foxtrot golf india hotel. Skip

I checked with Bob Kromer and he confirmed that the stall strips are fine tuned during production flight test: Due to variations in wing manufacture between airplanes, the stall strips are taped in place on the wing leading edges for the first production test flight. Stall strip locations are defined spanwise. Vertically around the leading edge radius, they are variable in location. For first flight, they are positioned vertically at the radius center (stagnation points) of each wing leading edge radius. The production pilot then performs a variety of power-off, wing level stalls to verify the airplane meets the certification requirement of plus or minus 15 degrees roll-off during the stall maneuver. If it does with the initial stall strip locations, they are then fixed in place and secured with screws. However, in general those initial stalls show excessive roll-off in on direction. In that case, the pilot returns and will adjust the stall strip on the "heavy" wing downward about 1/4" below the wing leading edge stagnation point. Moving the stall strip downward from the leading edge stagnation point slightly delays the stall strip tripping the air flow. This causes the "heavy" wing to maintain lift a bit longer during a stall maneuver, better matching the "airflow separation angle of attack" of the light (rising ) wing during the stall. Both wings should now stall about the same time, reducing the wing drop or roll-off tendency previously seen. A good production test pilot can generally set the stall strips in two flights. Skip

According to the doc I posted a link to, the military reserves the right to use pretty much whatever code they want to “increase operational security.” So, it could have been a F-15 or something using your ICAO code.

Here's a description of how winglets work from Richard Whitcomb taken from patent US5407153A. Winglets long have been used in the aircraft industry as a method for reducing drag, the retarding forces which act on an airplane as it moves through the air. Decreased drag results in increased fuel efficiency. Winglets are small lifting surfaces attached to the outboard end of an airplane wing, commonly at or near to a vertical angle from the wing structure. Winglets function to relocate the tip vortex of an airplane wing further outboard and above the unmodified location. In flight, the substantially inward pointing load carried by the winglets relocates the wing tip vortex. Due to pressure differentials between wing surfaces at a wing tip, air tends to flow outboard along the lower surface of a wing around the tip and inboard along the wing upper surface. When winglets are added, the relocated wing tip vortex caused by the winglets produces cross-flow at the winglets, which often are perpendicular to the flow across the wing surfaces. The side forces created by such cross-flow contain forward components which reduce drag.

Actually, this is the tip of a large iceberg. Duplicates will happen, either by mistake or design, and hopefully the FAA has a plan to deal with it. In addition, this is another digital system designed without security in mind, and it is subject to malicious attack by bad actors. https://apps.dtic.mil/dtic/tr/fulltext/u2/a545599.pdf

I think this is one of several devices that have been proposed to reduce induced drag by reducing wingtip vortices. Retired Boeing engineer Doug McLean discusses why these generally don’t work in his excellent book, Understanding Aerodynamics. The gist of his argument is that these ideas are based on the fallacious assumption that wingtip vortices are the source of induced drag and that induced drag could be reduced by simply installing a localized device to reduce the vortices. But, in reality induced drag is a function of the entire 3D airflow about a finite span wing of which the vortices are one component. It is not possible to eliminate the vortices without affecting the entire lift distribution. Skip

Well, that's just beautiful, Byron. The top picture looks more like my '94, so nothing improved in 17 years

I did have the wiring put in, but the AD was still active at the time so I couldn't get the unlock to activate it. Will get that done next time it goes to the radio shop. Thanks everyone for the helpful comment and insights. Skip

It’s not just Mooney that is having trouble making a buck in aviation Rolls-Royce Cuts Expected Orders On Short Notice The Financial Times (12/16, Subscription Publication) reports that on short notice, Rolls-Royce told suppliers that it is cutting expected orders. The move could cause significant tension within the supply chain and exacerbate existing troubles at Rolls-Royce.

Point taken. I was thinking of the wing on my ‘94 J. Harmon must have put all the design effort (and weight) into the spar because the pillowing on the top of the wing is pretty obvious. But I marvel at the smoothness of a 737 wing every time I ride on one.

I think the real value of composites is in the area of drag reduction: Smoother wings and complex air-friendly shapes for fuselages. There are also a lot of negatives as has been pointed out. It’s interesting to contemplate a clean sheet design for a vintage airplane. The problem is that the old designs weren’t that bad, so improvements in an airplane like a Mooney tend to be incremental rather than monumental. It’s tough to sell a plane that is 10% better at 5x the cost of a used one when the used ones are plentiful. What GA really needs is some breakthrough that drastically reduces component and manufacturing cost without depending on high volume production. Skip

That was really interesting. It shed a lot of light on how one goes about defining a set optimum parameters then designing to them. And that was nearly 30 years ago, so I’m sure there have been advances in design tools since then. Thanks for sharing it. Skip

I think he might have meant smaller wetted area. Since he was clearly taking aim at the Bonanza, it’s interesting to compare equivalent flat plate areas (courtesy of David Lednicer): Bonanza: 3.50 ft^2 Mooney: 2.81 ft^2 Skip