Pratt & Whitney R-1340 Wasp

Pratt & Whitney R-1340 Wasp
Name	R-1340 Wasp
Type	Radial engine
National origin	United States
Manufacturer	Pratt & Whitney
First run	1925
Major applications	Boeing P-26 Peashooter, North American T-6 Texan, Vought O2U Corsair, Boeing 247
Number built	34,966
Developed into	Pratt & Whitney R-985 Wasp Junior, Pratt & Whitney R-1830 Twin Wasp

Pratt & Whitney R-1340 Wasp was a pioneering American aircraft engine that became one of the most influential radial engines in aviation history. Introduced in the mid-1920s by Pratt & Whitney, its reliable power and relatively light weight revolutionized aircraft design for both military and commercial use. The engine's success established Pratt & Whitney as a major force in aeronautical engineering and spawned an entire family of successful Wasp series engines.

Development and design

The R-1340 was developed under the leadership of Pratt & Whitney founder Frederick Rentschler and chief engineer George J. Mead. Its design was a direct response to the United States Navy's need for a reliable, high-power, air-cooled engine, overcoming the limitations and hazards of liquid-cooled powerplants like the Curtiss D-12. The engine featured a single row of nine cylinders, incorporated advanced forging techniques for its crankcase, and used sodium-cooled exhaust valves for durability. A key innovation was the use of a master-and-articulating-rod assembly, which allowed all nine connecting rods to operate on a single crankshaft journal, contributing to a compact and robust design. The successful first run in December 1925 produced 425 horsepower, exceeding its design goals and immediately impressing the United States Army Air Service.

Operational history

The R-1340 entered service in 1926 and quickly became the engine of choice for a vast array of aircraft. It powered the United States Navy's Vought O2U Corsair and the United States Army Air Corps's Boeing P-26 Peashooter, America's first all-metal monoplane fighter. Its reliability was proven on long-distance flights, including the historic 1927 Pan American Goodwill Tour led by Henry Arnold. The engine was instrumental in the development of modern airliners, powering the groundbreaking Boeing 247 and the Sikorsky S-42 flying boat. During World War II, it became the primary trainer engine for the Allies, famously powering the North American T-6 Texan.

Variants

Numerous variants were produced over the engine's long production life, distinguished by different supercharger configurations, carburetor types, and rotation directions for contra-rotating propellers. Key designations included the R-1340-S1D1, an early direct-drive model for the Boeing F4B, and the R-1340-AN1, a prevalent World War II version with a geared supercharger used in the North American T-6 Texan. The R-1340-S3H1 featured a float carburetor for inverted flight, while the R-1340-16 was developed for the Canadian Car and Foundry Hawker Hurricane. Later models, like the R-1340-B, offered increased displacement and power.

Specifications (R-1340-S1H1-G)

* **Type:** 9-cylinder single-row supercharged air-cooled radial engine * **Bore:** 5.75 in (146 mm) * **Stroke:** 5.75 in (146 mm) * **Displacement:** 1,344 cu in (22.0 L) * **Length:** 47.8 in (1,214 mm) * **Diameter:** 51.5 in (1,308 mm) * **Dry weight:** 930 lb (422 kg) * **Valvetrain:** Two poppet valves per cylinder, sodium-cooled exhaust valves * **Supercharger:** Single-speed centrifugal type, 10:1 gear ratio * **Fuel system:** Stromberg carburetor * **Cooling system:** Air-cooled * **Power output:** 600 hp (450 kW) at 2,250 rpm for takeoff * **Compression ratio:** 6.0:1 * **Power-to-weight ratio:** 0.65 hp/lb (1.06 kW/kg)

Applications

The R-1340's list of applications is extensive, underscoring its versatility. Notable military aircraft included the Boeing P-26 Peashooter, Vought O2U Corsair, Grumman JF Duck, North American T-6 Texan, Boeing-Stearman Model 75, and Vultee BT-13 Valiant. Commercial and utility aircraft powered by the Wasp were the Boeing 247, Sikorsky S-42, Lockheed Model 10 Electra, and numerous Howard DGA series aircraft. It also saw use in autogyros like the Kellett KD-1 and post-war agricultural aircraft such as the Snow S-2 and PZL-101 Gawron.

Survivors and displays

Many R-1340 engines are preserved in museums and on restored aircraft worldwide. Significant displays can be found at the National Air and Space Museum in Washington, D.C., the New England Air Museum in Windsor Locks, Connecticut, and the Royal Air Force Museum London. Numerous airworthy examples continue to operate on flying North American T-6 Texan and Boeing-Stearman Model 75 aircraft at airshows, maintained by organizations like the Commemorative Air Force. The engine is also a common static display at aviation heritage sites, including the Pearl Harbor Aviation Museum and the Yanks Air Museum.

Category:Aircraft piston engines Category:Pratt & Whitney aircraft engines Category:Radial aircraft engines