The Curtiss H-1640 Chieftain was an unusual American 12-cylinder radial

aero engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years man ...

designed and built by the Curtiss Aeroplane and Motor Company in the mid-1920s.Gunston 1989, p. 46

Design and development

The H-1640 was an air-cooled 12 cylinder two-row radial with the cylinder rows aligned rather than staggered as in most multi-row radials. One piece

cylinder head In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinder (engine), cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas ...

s shared a single

overhead camshaft An overhead camshaft (OHC) engine is a piston engine where the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion ...

and the propeller was directly driven. By aligning the cylinders the diameter of the engine was less than more conventional radial engines, and it was thought that the use of a

Townend ring A Townend ring is a narrow-chord cowling ring fitted around the cylinders of an aircraft radial engine to reduce drag and improve cooling. Development The Townend ring was the invention of Dr. Hubert Townend of the British National Physical ...

could make the engine more aerodynamically efficient than an inline engine. The engine first ran in 1927. The H-1640 was the first airworthy 'inline radial' and was sponsored for flight testing in a range of aircraft by the U.S. Government. Among the types selected were the Thomas-Morse XP-13 and the Curtiss XO-18. Cooling problems with the rear cylinders caused the project to be canceled with few production engines being built. A similar engine is the Bristol Hydra although this engine had 16 aligned cylinders, forming an

octagon In geometry, an octagon (from the Greek ὀκτάγωνον ''oktágōnon'', "eight angles") is an eight-sided polygon or 8-gon. A ''regular octagon'' has Schläfli symbol and can also be constructed as a quasiregular truncated square, t, wh ...

. Further similar engines are the Armstrong Siddeley Hyena and the much larger Armstrong Siddeley Deerhound.

Applications

* Curtiss XP-22 Hawk *

Curtiss YP-20 The Curtiss YP-20 was an American biplane fighter project developed by Curtiss for the United States Army Air Service. Design and development In 1929, three Curtiss P-11 Hawks were ordered with 600 hp (447 kW) Curtiss H-1640 Chieftai ...

Curtiss P-6 Hawk The Curtiss P-6 Hawk is an American single-engine biplane fighter introduced into service in the late 1920s with the United States Army Air Corps and operated until the late 1930s prior to the outbreak of World War II. Design and development ...

* Thomas-Morse XP-13 Viper

Specifications (H-1640)

References

Notes

Bibliography