![]() ![]() But once below that speed (with me and a CFI and half fuel) the approach noticeably steepens. One can fly a perfectly satisfactory approach at or above that speed without a problem. ![]() The Mooney 20C I flew had a very distinct change in performance at around 80 or 85 mph (it was one or the other but can't remember which). Later that same day I ended up taking a tow on a short runway, behind a weak towplane with wet wings and found that my takeoff was significantly delayed. In an older sailplane with an early laminar airfoil design, I once experienced a stall during a smooth pull-up when the wing suddenly encountered rain. They handle angle of attack changes smoothly and generally fly without any surprises. Better designs tend to be insensitive to dirt, bugs, water droplets and minor manufacturing defects. Therefore, modern airfoil designs are significantly 'better' than older ones. The design of 'good' laminar airfoils is computer intensive. I think Cessna and others may have taken advantage of this structurally but I'm thinking that they tried laminar for performance, that is, speed. The high point of laminar airfoils tend to be further back than non-laminar because it is easier to maintain laminar flow when airfoil thickness is increasing than when it is decreasing. Round headed rivets, aluminum sheet edges and even rain will act as turbulators and will tend to defeat laminar flow. Impossible with a fabric wing, difficult with wood, challenging with thinner sheet aluminum, easier with composite surfaces. Achieving laminar flow for some portion of the airfoil requires precise control/manufacture of the airfoil profile and surface smoothness. The higher performance comes with a price and some tradeoffs. Laminar airfoils can offer lower drag or higher L/D ratios. I also have 1000+ in 2 high performance sailplanes with laminar flow airfoils. I only have about 15 or 20 hours in a Mooney 20C. The reference is to the Canadair F-86 that went into the Farrells Ice Cream Parlor off the end of the departure runway at Sacramento Executive in 1972: Examples include the Cessna 177B Cardinal and 177RG Cardinal RG Grumman-American AA-1A (and all Grumman two- and four-seaters thereafter) and the outer panels of the taper-winged Piper PA-28 and PA-32 series. The sharp leading edge can also lead to more abrupt stalls.Īs a result, the airfoils of several laminar-flow light airplanes were modified with more rounded leading edges, resulting in less drag at higher angles of attack, gentler stall characteristics, and little, if any, loss of cruising speed. This is noticeable if the pilot attempts to rotate too early on takeoff drag rises sharply and, if the airplane is at all underpowered, the takeoff becomes unduly sluggish, or in extreme cases, impossible. One characteristic of "laminar" airfoils is that drag increases much more rapidly at higher angles of attack. A spar carry-through must pass through the cabin ceiling, and only laminar wings would allow the carry-through to go behind the heads of the front-seat occupants, instead of severely limiting front-seat headroom. Why? They are also the only cantilever high-wing Cessnas. The only high-wing Cessnas that have laminar airfoils are the C-177 Cardinal and (1967 and later) C-210 Centurion. By contrast, a Beech Bonanza does not have a laminar wing, and its spar carry-through goes under the front seats, interfering with rear-seat passengers' legroom. That allows the designer to stow the main spar carry-through out of the way under the rear seat. A "laminar" wing has its maximum thickness - and therefore its main spar - further aft. The main reason that the Mooney and other (mostly low-wing) light airplanes have laminar airfoils is for interior packaging. Moreover, slight airfoil contour imperfections caused by the thin metal skins and wide rib spacing of smaller light airplanes often defeats any aerodynamic benefit the laminar airfoil might offer. In the speed range of typical piston light airplanes, though, the advantage is minimal. The P-51 was one of the early applications of this type of airfoil. Laminar airfoils do have advantages in lower drag, but mostly at higher airspeeds. A sheet of plywood produces lift at a positive angle of attack, too. Despite the fact that a "laminar" airfoil looks nearly symmetrical in cross-section, it produces lift when there is a positive angle of attack. ![]()
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