Jetrader - September/October 2008 - 31

A 1939 Weaver Aircraft Company of Ohio airplane with the NACA cowl, which signiﬁcantly improved drag reduction manufacturers. We will address Spanish/French and German engines sometime in the future. Pratt & Whitney became notable for its radial air-cooled engines, and arguably the R-2800 was one of the most reliable piston aero engines ever built. In his 2001 masterly 718-page treatise on its design and development, Graham White describes how having gained considerable experience by the mid-1930s with smaller two-row radial engines, it was decided to develop one of 2,600 cubic inches (42.6 liters). However, this could have placed the ﬁrm head to head with the Wright R-2600, so the capacity was increased to 2804 cubic inches (45.9 liters). Luke Hobbs, a brilliant designer, joined the company in 1927. He headed up the twin-row engine programs, notably the R-2800 and R-1830— of which 178,000 of the latter were manufactured during WWII. A 1931 design, the R-1830 had a two-stage, two-speed supercharger installed on the Grumman F4F-3 in 1939—two years before the Rolls-Royce Merlin 61 on the Spitﬁre XX. Although not the best in any one performance category, such as speciﬁc weight or fuel consumption, overall the R-2800 was the best in reliability, maintenance and the ability to withstand severe battle damage, all outstanding characteristics. In WWII its A, B and C series saw service on 68 different aircraft types and variants, notably the Republic P-47 Thunderbolt (“Jug”), and the Curtiss C-46F Commando transport. A doublebubble fuselage, it was the largest twin-engine aircraft used by the allies, bigger even than the four-engine Avro Lancaster and Boeing B-17. It was marginally underpowered at 2,100hp for hot-day, high-weight takeoffs, and accidents due to engine failure were common. Pratt & Whitney got into the aero engine business when the president of Wright Aeronautical Corporation, Frederick Rentschler, had a falling out with the board of directors. He persuaded Pratt to take him on as president of a new division manufacturing radial engines, and in the move he took with him from Wright George Mead, chief engineer, and Andy Willgoos, assistant chief Photo by Bill Bath The Pratt & Whitney R-2800, a two-row, 18-cylinder, air-cooled radial design engineer for design. Taking on Wright in a Navy competition for an engine with a weight limit of 650 pounds and 400hp, the resulting 600-pound, nine-cylinder, single-row R-1340 beat the Wright submission in both weight and power. On its third test run it was delivering 425hp, which impressed the Navy enough to order 200 engines. By the start of WWII it had a takeoff rating of 600hp for a weight of 684 pounds. A Side Note A number of British airframe manufacturers had an engine division, and The Bristol Aeroplane Company was one of the better known with its sleeve-valve radial Hercules and Centaurus engines. Prior to these it manufactured radial engines with standard poppet valves actuated by push rods, of which the Pegasus nine-cylinder radial of 1,050hp powered the famous Swordﬁsh (“Stringbag”) biplane torpedo bomber of the Royal Navy Fleet air arm throughout WWII. With a speed of 130 mph carrying a 1,610 lb torpedo, crew of three, two machine guns and air interception radar, it sunk more tonnage of enemy shipping than any other aircraft with a similar role during the war. Its best-known feat to U.S. readers was the crippling of the battleship Bismark’s steering gear in the North Atlantic, so it went around in circles to eventually be sunk by the Royal Navy leaving 205 survivors out of a crew of 2,200. The November 1940 surprise attack by 20 Swordﬁshes on the Italian ﬂeet moored in the harbor of Taranto left seven warships, including three battleships, so badly damaged they abandoned control of the Mediterranean to the Royal Navy, and initially, Luftwaffe Stuka dive bombers. The Japanese took note of this and repeated it a year later at Pearl Harbor on December 7, 1941. A ﬁnal note: on February 11, 1942, three German battlecruisers made a dash up the English Channel escorted by minesweepers from Brest to the Baltic to avoid the constant attacks by the RAF on their moorings. With visibility down to near zero from a winter storm The intricately designed gear-train for a sleevevalve-drive of the Bristol Hercules engine Jetrader 31

Jetrader - September/October 2008

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