Wright R-540 Whirlwind

R-540 Whirlwind
	Wright R-540 Whirlwind installed in a Travel Air 16E at the Historic Aircraft Restoration Museum
Type	Air-cooled 5-cylinder radial piston engine
National origin	United States
Manufacturer	Wright Aeronautical Corporation
Major applications	Various light aircraft
Produced	1929-1937
Number built	around 500

The Wright R-540 Whirlwind was a series of five-cylinder air-cooled radial aircraft engines built by the Wright Aeronautical division of Curtiss-Wright. These engines had a displacement of 540 in³ (8.85 L) and power ratings of around 165-175 hp (123-130 kW). They were the smallest members of the Wright Whirlwind engine family.

Design and development

Wright introduced the J-6 Whirlwind family in 1928 to replace the nine-cylinder R-790 series. The J-6 family included varieties with five, seven, and nine cylinders. The five-cylinder version was originally known as the J-6 Whirlwind Five, or J-6-5 for short. The U.S. government designated it as the R-540; Wright later adopted this and dropped the J-6 nomenclature.

Like all the members of the J-6 Whirlwind family, the R-540 had larger cylinders than the R-790. The piston stroke of 5.5 in (14.0 cm) was unchanged, but the cylinder bore was expanded to 5.0 in (12.7 cm) from the R-790's bore of 4.5 in (11.4 cm). While the R-790 was naturally aspirated, the R-540, like the other J-6 engines, had a gear-driven supercharger to boost its power output.

Wright gradually refined the R-540, using suffix letters to indicate successive versions. For example, the R-540A had 165 hp (123 kW), while the R-540E of 1931 had power boosted to 175 hp (130 kW) thanks to an improved cylinder head design. Wright sometimes named these versions according to their power, e.g. "Whirlwind 165" or "Whirlwind 175".^[1]

The engine was built in Spain as the Hispano-Suiza 5Q or Hispano-Wright 5Q without modification apart from the use of Hispano's patented nitriding finishing process.^[2]

Operational history

The R-540 was the smallest, least powerful member of the Whirlwind family and was designed for light aircraft. One of the more popular types to use it was the Curtiss Robin, a light civil utility aircraft. A few were also used in prototype military trainer aircraft that were evaluated by the U.S. Army but not put into production.

The R-540 sold well at first, with over 400 engines being built in 1929.^[3] However, with the impact of the Great Depression, sales plummeted, and only about 100 further examples were built over the next eight years.^[3] Wright finally ceased production of five-cylinder Whirlwinds in 1937,^[3] concentrating on larger engines and leaving the market for small radials to companies like Kinner and Warner.

Since R-540 engines were found solely in light aircraft, they weren't often used for groundbreaking flights. However, there were a couple of noteworthy exceptions which took advantage of the Whirlwind family's reputation for high reliability. In 1935, the brothers Al and Fred Key set a new flight endurance record of 653 hours, 34 minutes in the Curtiss Robin J-1 Ole Miss, flying over Meridian, Mississippi, from June 4 to July 1. Their plane was refueled and resupplied in flight, and they could perform simple engine maintenance by walking out on a small catwalk extending between the cabin and the engine. Douglas "Wrong-Way" Corrigan's famous unauthorized transatlantic flight from New York City to Dublin, Ireland on July 17–18, 1938, used a Curtiss Robin with an R-540 built from the parts of two used engines.^[4]

Applications

Engines on display

Wright R-540 engines on display are uncommon, but there is one at the Strategic Air and Space Museum (formerly the Strategic Air Command Museum) near Ashland, Nebraska.^[5] Another is on display at the Shannon Air Museum in Fredericksburg, Virginia.

Specifications (R-540E)

Data from FAA type certificate data sheet for the R-540E;^[6] dimensions from Curtiss-Wright (1983).

General characteristics

Type: 5-cylinder supercharged air-cooled radial piston engine
Bore: 5.0 in (127 mm)
Stroke: 5.5 in (140 mm)
Displacement: 540 cu in (8.85 L)
Length: 41.1 in (104.4 cm)
Diameter: 45.0 in (114.3 cm)
Dry weight: 420 lb (191 kg)

Components

Valvetrain: 2 valves per cylinder, pushrod-actuated
Supercharger: gear-driven, 7.05:1 impeller gear ratio
Fuel type: 65 octane
Reduction gear: Direct drive

Performance

Power output: 175 hp (130 kW) at 2,000 RPM at sea level
Specific power: 0.324 hp/cu-in (14.7 kW/L)
Compression ratio: 5.1:1
Power-to-weight ratio: 0.417 hp/lb (0.685 kW/kg)

References

Notes

^ Curtiss-Wright (1940)
^ Lage (2004) pp.152-163
^ ^a ^b ^c Summary of Wright Engine Shipments: 1920 to 1963 (PDF), archived from the original (PDF) on March 3, 2016, retrieved December 10, 2009. Transcribed from Wright Aeronautical documents by Robert J. Neal T; available from the Aircraft Engine Historical Society's reference page Archived 2010-02-04 at the Wayback Machine.
^ Forden (1958) p.84
^ Aircraft Engines, archived from the original on 2017-07-28, retrieved 2008-09-11. This personal collection of museum aircraft engine photos includes a photo of a Wright R-540 under the SAC Museum section. (The page mislabels it as a "Wright R-540 J-5"—there never was a five-cylinder version of the J-5.)
^ FAA, ATC 23 data sheet

Bibliography

Curtiss-Wright (1940), Wright Engines - Past and Present (PDF), pp. 12–13, archived from the original (PDF) on February 15, 2010, retrieved December 10, 2009. Available from the Aircraft Engine Historical Society's reference page Archived 2010-02-04 at the Wayback Machine.
Forden, Lesley (1958), "Whatever Became of the Curtis Robin", Flying, vol. 62, no. 4, pp. 54–84
Lage, Manual (2004), Hispano Suiza in Aeronautics, Warrendale, USA: SAE International, ISBN 0-7680-0997-9
Curtiss-Wright (1983), Historical Engine Summary (Beginning 1930) (PDF), p. 1, archived from the original (PDF) on October 31, 2010, retrieved December 10, 2009. Available from the Aircraft Engine Historical Society's reference page Archived 2010-02-04 at the Wayback Machine.
Federal Aviation Administration, Approved Type Certificate No. 23 (ATC 23) data sheet, retrieved December 10, 2009. Available from the FAA's Regulatory and Guidance Library Archived 2016-11-12 at the Wayback Machine.
USAF Air Materiel Command (January 1, 1950), Model Designations of USAF Aircraft Engines: Section I, Reciprocating Engine Characteristics (PDF), p. 8, retrieved December 10, 2009. Available from the Aircraft Engine Historical Society's reference page Archived 2010-02-04 at the Wayback Machine.