The Propeller Research Tunnel (PRT) was the first full-scale wind tunnel at the National Advisory Committee for Aeronautics ( NACA)

Langley Research Center The Langley Research Center (LaRC or NASA Langley), located in Hampton, Virginia, United States of America, is the oldest of NASA's field centers. It directly borders Langley Air Force Base and the Back River on the Chesapeake Bay. LaRC has fo ...

, and the third at the facility. It was in use between 1927 and 1950 and was instrumental in the drag reduction research of early American

aeronautics Aeronautics is the science or art involved with the study, design, and manufacturing of air flight–capable machines, and the techniques of operating aircraft and rockets within the atmosphere. The British Royal Aeronautical Society identifies ...

. In 1929, NACA was awarded its first Collier Trophy for the NACA cowling which was tested and developed using the Propeller Research Tunnel.

Purpose

The main purpose of the Propeller Research Tunnel was researching the aerodynamic efficiency of propellers on radial engine aircraft. In 1917, William F. Durand published NACA Technical Report 17 on his work with isolated propellers in Stanford University's wind tunnel, however these results did not match with the data NACA had collected for propellers connected to fuselages. Additionally, little was known about the limitations of propellers. Propellers had efficiency issues caused by loss of compression at the tips at high speeds. In 1923, Langley engineer

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 ...

, suggested NACA build a wind tunnel with a 20 foot diameter throat, capable of speeds up to 100 miles per hour in order to perform full-scale propeller tests. According to Weick, British engineers were running tests on scale propellers at the time, but were unable to obtain accurate results due to a scaling issue related to the

Reynolds number In fluid mechanics, the Reynolds number () is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be domi ...

in the smaller wind tunnels. NACA had been using the Variable Density Tunnel in order to increase the density of air to keep the Reynolds number in testing similar to the Reynolds number experienced by full-scale aircraft. However, the Variable Density Tunnel was not able to provide consistent data for propellers, so NACA built the Propeller Research Tunnel.

History

NACA began work on the Propeller Research Tunnel under direction of Director of Aeronautical Research

George W. Lewis George William Lewis (March 10, 1882 – July 12, 1948) was the Director of Aeronautical Research at the National Advisory Committee for Aeronautics (NACA) until he retired in 1947. He taught at Swarthmore College from 1910 to 1917. Biograph ...

in 1925 and completed its construction in 1927. Built using two 1000-horsepower diesel submarine engines, and an 8-blade, 27-foot diameter fan, the Propeller Research Tunnel was capable of pushing air in a 20-foot stream at 110 miles per hour. The PRT remained operational until it was demolished in 1950 when NACA needed a place to build their 8-foot Transonic Pressure Tunnel.

Use in Research

Propeller Research

The Propeller Research Tunnel was used in the development of more efficient propellers that did not lose compression at the blade tips at high speeds. NACA was also able to test full scale propellers to find a blade shape that maximized efficiency and performance where previous designs had failed.

NACA cowling

The PRT was also used to develop a way to reduce the drag produced by the exposed pistons of radial turbine engines. By testing various cowlings on full-scale models in the PRT, NACA was able to produce the NACA cowl, which won the

Collier Trophy The Robert J. Collier Trophy is an annual aviation award administered by the U.S. National Aeronautic Association (NAA), presented to those who have made "the greatest achievement in aeronautics or astronautics in America, with respect to im ...

in 1929 for its impact on aeronautics. It was predicted that the cowling, by reducing drag and increasing engine cooling, would save the American aircraft industry upwards of $5 million, and the cowling and its variants were quickly adopted by plane manufacturers.

Other

Similarly, the PRT found that engine placement and the fixed landing gear contributed greatly to drag. NACA engineers worked to create a retractable landing gear and found that multi-engine planes benefited from having their engines in-line with the leading edge of the wing. Both of these discoveries were also quickly adopted by airplane manufacturers. Data collected in the PRT was used heavily in the design of many World War II planes including the

Boeing B-17 Flying Fortress The Boeing B-17 Flying Fortress is a four-engined heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Relatively fast and high-flying for a bomber of its era, the B-17 was used primarily in the European Theater ...

Consolidated B-24 Liberator The Consolidated B-24 Liberator is an American heavy bomber, designed by Consolidated Aircraft of San Diego, California. It was known within the company as the Model 32, and some initial production aircraft were laid down as export models des ...

, and the

Douglas DC-3 The Douglas DC-3 is a propeller-driven airliner manufactured by Douglas Aircraft Company, which had a lasting effect on the airline industry in the 1930s to 1940s and World War II. It was developed as a larger, improved 14-bed sleeper version ...

References

{{reflist

External links

NASA - Propeller Research Tunnel
Wind tunnels Langley Research Center National Advisory Committee for Aeronautics