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

radial Radial is a geometric term of location which may refer to: Mathematics and Direction * Vector (geometric), a line * Radius, adjective form of * Radial distance, a directional coordinate in a polar coordinate system * Radial set * A bearing f ...

aero engine designed and built by the

Curtiss Aeroplane and Motor Company Curtiss Aeroplane and Motor Company (1909 – 1929) was an American aircraft manufacturer originally founded by Glenn Hammond Curtiss and Augustus Moore Herring in Hammondsport, New York. After significant commercial success in its first decades ...

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 cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...

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 c ...

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 Physica ...

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 The Bristol Hydra (also known as the Double Octagon) was an experimental 16-cylinder, twin-row radial aircraft engine built by the Bristol Engine Company. It is a relatively rare example of a radial with an even number of cylinders per rowit ...

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, whi ...

. Further similar engines are the

Armstrong Siddeley Hyena The Armstrong Siddeley Hyena was a British aero engine developed by Armstrong Siddeley. Designed in the 1930s, it was an unusual experimental radial engine with inline cylinder banks. It was flown using an Armstrong Whitworth A.W.16 fighter a ...

and the much larger

Armstrong Siddeley Deerhound The Armstrong Siddeley Deerhound was a large aero engine developed by Armstrong Siddeley between 1935 and 1941. An increased capacity variant known as the Boarhound was never flown,Gunston 1989, p.18. and a related, much larger, design known a ...

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 Th ...

* Thomas-Morse XP-13 Viper

Specifications (H-1640)

References

Notes

Bibliography