Curtiss AT-5a NACA Cowling - GPN-2000-001724

The NACA cowling is a type of

aerodynamic Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...

fairing used to streamline

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ...

s installed on

airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad ...

s. It was developed by

Fred Weick Fred Ernest Weick (1899–1993) was an airmail pilot, research engineer, and aircraft designer. Working at the NACA, he won the 1929 Collier Trophy for his design of the NACA cowling for radial air-cooled engines. Weick's aircraft designs inc ...

of the

National Advisory Committee for Aeronautics The National Advisory Committee for Aeronautics (NACA) was a United States federal agency founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its assets ...

(NACA) in 1927. It was a major advance in

aerodynamic drag In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding ...

reduction, and paid for its development and installation costs many times over due to the gains in

fuel efficiency Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device ...

that it enabled.

History and design

The NACA

cowling A cowling is the removable covering of a vehicle's engine, most often found on automobiles, motorcycles, airplanes, and on outboard boat motors. On airplanes, cowlings are used to reduce drag and to cool the engine. On boats, cowlings are a cove ...

enhanced speed through drag reduction while delivering improved engine cooling. The cowling consists of a symmetric, circular airfoil that is wrapped around the engine. In a normal planar airfoil, like a wing, it is the difference in airspeed, and their associated changes in pressure, on the top and bottom of the surface that produces lift. In the case of the NACA cowl, the ring-shaped airfoil is positioned so this lift effect is forward, producing thrust. This thrust does not counteract the total drag of the cowl, but greatly reduces its overall value. The difference in airspeed on the two sides is due not only to the shape of the airfoil, but also the presence of the cylinders on the inside surface, which serves to further slow the airflow. Nevertheless, the total airflow through the cowl is generally greater than it would be with no cowl as the air is sucked through the cowl by the air flowing around it. This has the side-effect of keeping the fast moving air primarily on the cylinder heads where it is most needed, as opposed to flowing between and into the cylinders and crankcase where it does little for cooling. Furthermore, turbulence after the air passes the free-standing cylinders is greatly reduced. The sum of all these effects reduces drag by as much as 60%. The test conclusions resulted in almost every radial-engined aircraft being equipped with this cowling, starting in 1932. The test aircraft, a Curtiss AT-5A Hawk biplane, featuring a Wright Whirlwind J-5 radial engine, reached an airspeed of equipped with the NACA cowling compared to without it. The idea that the NACA cowling produced thrust through the Meredith effectMeredith, F. W: "Cooling of Aircraft Engines. With Special Reference To Ethylene Glycol Radiators Enclosed In Ducts", Aeronautical Research Council R&M 1683, 1936. is fallacious—although in theory the expansion of the air as it was heated by the engine could create some thrust by exiting at high speed, in practice this required a cowling designed and shaped to achieve the high-speed exit of air required (which the NACA cowling was not), and in any case, at 1930s airspeeds, the effect was negligible.Becker, J.
''The high-speed frontier: Case histories of four NACA programs, 1920- SP-445, NASA (1980), Chapter 5: High-speed Cowlings, Air Inlets and Outlets, and Internal-Flow Systems: The ramjet investigation
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References

Other source

*Aeronautic exhibit in

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Found ...

, Washington, D.C.

External links

Abstract of NACA TN 301 report and .pdf file

Archive of NACA reports 1917-1958
{{Aircraft components Aerodynamics Aircraft components

Cowling A cowling is the removable covering of a vehicle's engine, most often found on automobiles, motorcycles, airplanes, and on outboard boat motors. On airplanes, cowlings are used to reduce drag and to cool the engine. On boats, cowlings are a cove ...

History and design

See also

References

Other source

External links