Pratt & Whitney Hornet

	Pratt & Whitney Hornet


	The Pratt & Whitney R-1690 Hornet.

In the mid 1930s, Pratt & Whitney produced five basic engines:

	•	The single-row Wasp Junior.
	•	The single-row Wasp.
	•	The single-row Hornet.
	•	The double-row Twin Wasp.
	•	The double-row Twin Wasp Junior.

The Pratt & Whitney Hornet was a 9 cylinder, single-row, air-cooled radial engine. Horsepower ranged from 525 hp to 1,050 hp depending on the model and configuration. It was produced in two ranges:


	•	The R-1690 Hornet A.
	•	The R-1860 Hornet B.

The series began with the R-1690 Hornet A in 1926 following production of the air-cooled R-1340 Wasp. It was enlarged in 1929 as the R-1860 Hornet B, but it was not a commercial success. The Hornet competed with its own Pratt & Whitney R-1830 Twin Wasp and the Wright Cyclone R-1820. Even though the Hornet was cheaper and simpler than the Twin Wasp, the Twin Wasp was a much more powerful engine and the Hornet's larger diameter was its main drawback. In the end, the Twin Wasp became a more sought after engine and the Hornet was dropped from production. ¹ Production was a modest 2,944 engines produced from 1926 to 1942 and it was used in a range of aircraft that included the Boeing B-9 and Boeing Model 299. By 1934, the Sikorsky S-42 was using four Hornets rated at 750 hp each.² The Hornet was also built under license in Italy as the Fiat A.59 and in Germany as the BMW 132 which powered the Junkers Ju-52.³

Specifications:
Pratt & Whitney Hornet

Displacement: 1,690 cu. in. (27.7 liters) 1,860 cu. in. (30.5 liters)

Date: 1926 1929

Cylinders: 9 9

Configuration: Single-row, air-cooled radial Single-row, air-cooled radial

Horsepower: 525 hp (392 kW) 575 hp (429 kW)

RPM: 1,900 1,950

Bore and Stroke: 6.1 in. (156 mm) X
6.4 in. (162 mm) 6.3 in. (171 mm) X
6.8 in. (171 mm)

Diameter: 54.41 inches (1,382 mm) 54.41 inches (1,382 mm)

Weight: 800 lbs. (362 kg) 860 lbs. (390 kg)

Specifications:
Pratt & Whitney Hornet
Displacement:	1,690 cu. in. (27.7 liters)	1,860 cu. in. (30.5 liters)
Date:	1926	1929
Cylinders:	9	9
Configuration:	Single-row, air-cooled radial	Single-row, air-cooled radial
Horsepower:	525 hp (392 kW)	575 hp (429 kW)
RPM:	1,900	1,950
Bore and Stroke:	6.1 in. (156 mm) X 6.4 in. (162 mm)	6.3 in. (171 mm) X 6.8 in. (171 mm)
Diameter:	54.41 inches (1,382 mm)	54.41 inches (1,382 mm)
Weight:	800 lbs. (362 kg)	860 lbs. (390 kg)

Endnotes:

1. Herschel Smith. A History of Aircraft Piston Engines. Manhattan, Kansas: Sunflower University Press, 1993. 107.
2. The Pratt & Whitney Aircraft Story. Pratt & Whitney: 1950. 77.
3. Herschel Smith. 134-136.