NACA cowling

The NACA hood is an engine cowling for radial engines of aircraft.

The hood makes sure that cooling air can flow through the concentrically around the propeller shaft and the crank arranged inlet opening from the front and from there on the hottest items, so the cylinder, and particularly the cylinder heads of the radial engine. Then delivers the heated air from an annular gap which is provided normally with adjustable cowl flaps, back off. Through this Luftausströmklappen the rear end of the hood, the air flow to the respective motor load or the cooling requirement can be customized. The NACA hood reduces the turbulent flow behind the otherwise free-standing beam or propeller slipstream components of a radial engine and simultaneously produces a clean aerodynamic transition from the engine to the fuselage or engine nacelle. Thus, the ring reduces the air resistance of the power plant significantly, at the same time it provides an optimal flow of cooling air safely.


The NACA hood was developed by a development team led by Fred Weick at the National Advisory Committee for Aeronautics ( NACA ) in 1928 in one of the first large-scale wind tunnels. The experimental aircraft, a Curtiss P-5 biplane with a radial engine type Wright J -5, reached with the hood 220 km / h instead of 190 km / h, without anything else has been changed on the aircraft.

The results meant that virtually all the models that used a radial engine, have been equipped since 1932 with a corresponding hood. More radical interpretations in jet cooler design meant that the panels even net thrust delivered at certain altitudes above certain speeds.