I am guessing. I would think that prior to the Wrights, early manufacturers would have used a flat surface as an airfoil. By definition symmetrical, but only due to lack of test or inspiration perhaps. Technically, Lilienthal employed flexible canvas wings?? Also technically symmetrical. The Rogallo comes to mind, I owned a Manta, it certainly was symmetrically airfoiled. For all his fame, Bernoulli predated all wings, his data was applied, and linked to fluid research.
The first Boomerang was perhaps flat, to be updated by a bright hunter in the outback
Some old guys may remember the 'Thermic50', or the junior 'Ringmaster' ?
Not on the list, but Vultee's model 51 and derivatives (V.54, BT-13, BT-15 etc.) had a symmetrical airfoil - probably NACA 0015. The V.51 first flew in March 1939 per Wikipedia.
And (I'm speculating here) the earlier Vultee SE transports (V-1A...) likely also used the same airfoil.
EDIT: While the Vultees are not listed, the Universal Products XBT-16 shows a "NACA 0018-64 mod" root airfoil. Inasmuch as the XBT-16 was a BT-13 modified to use major components made of molded plywood vs aluminum, I'd expect the other Vultees used the same airfoil.
I am guessing. I would think that prior to the Wrights, early manufacturers would have used a flat surface as an airfoil.
Eksplain? Airfoils well before the Wrights were already cambered... the whole notion of camber as against flat-plate was understood already.
Originally Posted by Jane-DoH
What were the first airplanes in the world ever to use a symmetrical airfoil cross-section?
Interesting question.... what made you ask it? I'll have to pull out my textbooks (from 45 years back) to check, but my memory is that just about any asymmetric airfoil is more efficient, and that about the only use for symmetric airfoils was on aerobatic-type aircraft, that spent half their flying time upside-down anyway.
(BTW, Jane, my question is meant seriously, since this is TechLog, not JB.)
Of course there was camber before the Wright's, but I was trying to suggest symmetricals?? Canvas is an airfoil, and simply because its shape in flight is "cambered", so is its 'under panel', hence the symmetrical requirement for the question?? A solid plane doesn't warp or curve in flight, for purpose of discussion, so it is a flying symmetrical?? No? F-104? I have gazed down the hard points at the tip at the "S" curve. For purposes of discussion, even though it "curves" it is very close to "symmetrical" as it is so very thin in section. This opinion wants a little leeway. Do you still have that nifty pic of the wing??
I have no idea for sure, but here is a clue: Gehard Fieseler in the early 1930's in Germany. Fieseler became a leading light in European aerobatics; the aerobatic judging system he devised was the first to use coefficients of difficulty and was adopted internationally. He became the highest-paid airshow pilot in Europe, which allowed him to buy a small glider factory at Kassel. One of the first aircraft he produced was his special aerobatic machine, the Tiger, which introduced the first symmetrical airfoil (or wing section), now an essential feature of aerobatic machines. He later went on to start a business that built FW190's during the war.
The P-51 used the NACA 45-100 which was supposed to be a laminar airfoil but never achieved that status due to manufacturing tolerances. Was not a symmetrical airfoil.
From a NASA report
One of the major emphases of the documentary record is the experience of the North American P-51 Mustang, one of history’s most remarkable airplanes and the first aircraft to employ a NACA laminar-flow airfoil. More than any other case study, the Mustang’s performance in the war demonstrates how the NACA’s laminar-flow airfoils proved to be a success, despite also being a failure. The record of this magnificent fighter plane confirmed expectations of appreciable improvements in speed and range as a result of the low-drag design, but practical experience with this and other aircraft using advanced NACA sections in the 1940s also showed that the airfoil did not perform as spectacularly in flight as in the laboratory. Manufacturing tolerances were off far enough, and maintenance of wing surfaces in the field were careless enough, that some significant points of aerodynamic similarity between the operational airfoil and the accurate, highly polished, and smooth test model were lost. Because the percentage drag effect of even minor wing surface roughness (e.g., dirt, dead bugs, and the dusty footprints of airplane crewmen) increased as airfoils became more efficient, laminar flow could be maintained in actual flight operation only in a very small region near the leading edge of the wing.
Still, the Mustang’s airfoil section turned into an excellent wing. Ironically, this development was due to its high-speed performance rather than its low-drag. In “one of those rare instances in the history of technology in which a system becomes a success because it unexpectedly excels at something for which it was not originally designed,” a decade of dedicated airfoil research by the NACA resulted, not in what Eastman Jacobs and his colleagues were after, but in something else, almost as good.27 Not only were the NACA’s 6-series laminar-flow airfoils used with great success on the Mustang, they were also to be employed on just about every other high-speed airplane that came after it, up to the time that sophisticated computer-aided design took over and started customizing advanced airfoil shapes in the 1980s.
Jane-DoH uses the term "crest" I think to describe the point of maximum thickness of the airfoil. In the P-51's case the max is at 45% chord - unusually aft for that day, when most airfoils had max thickness at 25 or 30% chord. And there was a distinct inflection at the 45% point so the thickness decreased rapidly as the air flowed aft.
I've been searching for a profile drawing of the NACA 45-100 to illustrate this - not successfully so far.
I meant the thickest part of the wing. I actually thought that area was formally called the crest...
In the P-51's case the max is at 45% chord - unusually aft for that day, when most airfoils had max thickness at 25 or 30% chord. And there was a distinct inflection at the 45% point so the thickness decreased rapidly as the air flowed aft.
So the only reason these characteristics were incorporated into the wing was to produce laminar flow, or were these characteristics also implemented to reduce wave drag?
Completely tangential to this technical conversation:
I find it most interesting that the NACA research on early laminar-flow airfoils found its first implementation in an aircraft designed for the export market. The British were visiting US manufacturers, and as the story goes, they asked NAA to become a second source for the Curtiss Kittyhawk. NAA countered with their own design, the NA-73, incorporating US taxpayer-funded research, and won the British contract.
Glad it all worked out in the end, but did NAA or the British ever compensate the US government for that research? There are modern examples of US manufacturers doing so when government-funded projects are reborn in the civil market (GE paid a royalty on CF6's for their TF39-based content, for example).