Maintenance on P&W R-2800 engine of C-46
The Pratt & Whitney R-2800 Double Wasp was a highly significant and advanced aircraft engine used extensively during World War II. This engine was a critical component of many American fighter planes, bombers, and transports, contributing significantly to the Allied war effort.
Key Features and Design
Configuration and Displacement: The R-2800 featured 18 air-cooled cylinders arranged in two rows. It had a total displacement of 2804 cubic inches (46 liters), achieved with a bore of 5.75 inches and a stroke of 6.0 inches. This design provided a robust platform for generating substantial power.
Bearings and Crankshaft: Unlike previous Pratt & Whitney engines, the R-2800 used plain silver-lead-indium bearings for the crankshaft main and master rod bearings. It also featured a three-piece built-up crankshaft, which allowed for one-piece master rods. The propeller thrust bearing was of the ball thrust type, and the rocker arms were supported by roller bearings.
Cooling and Materials: The engine used advanced cooling techniques, including chrome molybdenum steel alloy cylinder forgings with aluminum cooling muffs shrunk onto the barrels. The heads were cast aluminum, with a design optimized for cooling efficiency. Pratt & Whitney engineers also focused on the cylinder head’s fin design, making them deeper to improve heat dissipation.
Supercharging and Carburetion: The R-2800 was equipped with a single-stage, often two-speed, supercharger. For certain applications, two-stage supercharging was also developed, especially for Navy aircraft. The engine used the Bendix injection carburetor, with early models employing the PT-13 three-barrel carburetor and later models using the improved PR-58. The supercharger impellers featured a sophisticated fuel distribution system, ensuring efficient mixture distribution and reducing induction icing risks.
Performance: The R-2800 started with a power output of 1850 horsepower and exceeded 100 hp per cylinder, a significant milestone at the time. Improvements in fuels, cooling, and supercharging technology allowed the engine’s performance to increase over its production life, reaching up to 2400 horsepower in later models.
Applications: The engine was used in many iconic aircraft, including the Vought F4U Corsair, Republic P-47 Thunderbolt, Grumman F6F Hellcat, and Douglas A-26 Invader, among others. These aircraft were crucial in various roles, from air superiority and ground attack to reconnaissance and transport.
Manufacturing and Innovations
The R-2800 was produced in large numbers and benefited from numerous manufacturing innovations. The use of magnesium castings for various components helped reduce weight, and the extensive use of aluminum and sophisticated mounting systems helped manage vibration and stress, enhancing the durability and performance of both the engine and the airframe.
In conclusion, the Pratt & Whitney R-2800 was a marvel of engineering that combined robust design with advanced technology, setting new standards for aircraft piston engines during World War II. Its reliability, power, and adaptability made it one of the finest piston engines ever built, significantly contributing to the success of Allied air operations.