Lycoming XH-2470

In 1932, the engineers at Lycoming Engines became aware that the United States Army Air Corps (USAAC) wanted a high-performance engine that could produce at least one horsepower per cubic inch (46 kW/L) of engine displacement.[1] Determined to become known as a high-performance engine manufacturer, Lycoming began an experimental, high-performance engine of its own. After spending US $500,000, and after many attempts to develop a successful engine, it finally came close to the USAAC specifications with the O-1230 engine, which was a 12-cylinder liquid-cooled horizontally opposed low-profile piston engine.[2] In 1936, the single-cylinder development tests exceeded expectations, passing its 50-hour test requirement. The full-size engine was ready for testing in 1937, and was rated at 1,000 hp. Continued development of the O-1230 reached its peak when the engine was rated at over 1,200 hp (895 kW). The O-1230 was not well received by aircraft manufacturers, because it was not very reliable at that power setting.[2]

It was apparent that the O-1230 engine was uncompetitive with the high-performance air-cooled engines that were then becoming available. The US Navy began funding the development of the Lycoming engine.[3] The funding enabled Lycoming's engineers to attempt rescuing the design by proposing a 24-cylinder H-configuration engine made by stacking two of the O-1230 engines, gearing them together to one common output shaft. The new engine was the H-2470. It weighed in at 2,430 pounds and produced 2,300 hp (1,700 kW) at 3,300 rpm.[2]

The Navy specified the H-2470 for the Curtiss XF14C-1 experimental fighter.[2] After some rigorous testing the engine's poor performance led to the substitution, before the aircraft flew, of a Wright R-3350 radial engine, which was also having technical problems but was considered to be more reliable than the H-2470. The testing program was eventually terminated due to the poor performance of the aircraft.[4]

The USAAC was also interested in the H-2470, and installed and flew it in the Vultee XP-54 prototype fighter. The XP-54 was the only aircraft to actually use it for flight, but like the Navy's XF-14C, the XP-54 never went into production.[2]

• Vultee XP-54

Comparable engines

• Fairey P.24
• Napier Sabre

Related lists

• List of aircraft engines

• White, Graham, Allied Aircraft Piston Engines of World War II, SAE International, 1995
• Balzer, Gerald C., American Secret Pusher Fighters of World War II, Specialty Press. 2008
• Wagner, Ray, American Combat Planes, Third Enlarged Edition, Doubleday, 1982.
• Wegg, John, General Dynamics Aircraft and Their Predecessors, Naval Institute Press, 1990.

• XH-2470 in a test cell