NACA hood

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NACA canopy on a Curtiss AT-5A at the Langley Memorial Aeronautical Laboratory (October 1928)

The NACA hood is an engine casing for radial engines on aircraft .

development

The NACA canopy 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 wind tunnels at the Langley Memorial Aeronautical Laboratory . The experimental aircraft, a Curtiss P-5 - Double Decker 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 led to the fact that practically all models that used a radial engine were equipped with a corresponding hood from 1932. More radical designs in nozzle cooler design meant that the cladding even delivered net thrust at certain heights and from certain speeds.

function

NACA hood (black and white) on a North American T-6

The hood ensures that cooling air can flow in from the front through the inlet opening , which is arranged concentrically around the propeller shaft and the crankcase, and from there over the hottest parts, i.e. the cylinders and especially the cylinder heads of the radial engine. The heated air then exits through an annular gap, which is usually provided with adjustable cooling air flaps. With these air outflow flaps at the rear end of the hood, the air throughput can be adapted to the respective engine load or the cooling requirement. The NACA hood reduces the turbulent flow behind the components of a radial engine that are otherwise free in the propeller jet or airflow and at the same time creates a clean aerodynamic transition from the engine to the fuselage or engine nacelle. As a result, the ring significantly reduces the aerodynamic drag of the engine system, while at the same time ensuring an optimal flow of cooling air.

See also

Web links

Commons : NACA hood  - collection of images, videos and audio files
  • Theodore Theodorsen, MJ Brevoort and George W. Stickle: Full-scale tests of NACA cowlings. (PDF) In: Report No. 592. National Advisory Committee for Aeronautics, 1937, accessed July 30, 2018 .

Individual evidence

  1. ^ Roger E. Bilstein: Orders of Magnitude - A History of the NACA and NASA, 1915–1990, Chapter 1: NACA ORIGINS (1915–1930) (online at history.nasa.gov)