![Daimler D II](https://upload.wikimedia.org/wikipedia/commons/5/52/Daimler_D_II.jpg)
In
aviation
Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot air ...
, an inline engine is a
reciprocating engine
A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...
with
bank
A bank is a financial institution that accepts deposits from the public and creates a demand deposit while simultaneously making loans. Lending activities can be directly performed by the bank or indirectly through capital markets.
Because ...
s of cylinders, one behind another, rather than rows of cylinders, with each bank having any number of cylinders, although more than six is uncommon. The major reciprocating-engine alternative configuration is the
radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ca ...
, where the cylinders are placed in a circular or "star" arrangement.
The term "inline" is used somewhat differently for aircraft engines than automotive engines. For automotive engines, the term ‘inline’ refers only to straight engines (those with a single bank of cylinders). But for aircraft, ‘inline’ can also refer to engines which are not of the straight configuration, such as V, H, or horizontally opposed.
Inline engine configurations
;
Straight
Straight may refer to:
Slang
* Straight, slang for heterosexual
** Straight-acting, an LGBT person who does not exhibit the appearance or mannerisms of the gay stereotype
* Straight, a member of the straight edge subculture
Sport and games
* Str ...
: Engines with a single bank of cylinders which can be arranged at any angle but typically upright or inverted, (e.g. upright
ADC Cirrus
The ADC Cirrus is a series of British aero engines manufactured using
surplus Renault parts by the Aircraft Disposal Company (ADC) in the 1920s.
The engines were air-cooled, four-cylinder inline types. They were widely used for private and li ...
, inverted
de Havilland Gipsy Major
The de Havilland Gipsy Major or Gipsy IIIA is a four-cylinder, air-cooled, inverted inline engine used in a variety of light aircraft produced in the 1930s, including the famous Tiger Moth biplane. Many Gipsy Major engines still power vintag ...
).
;
V:Engines with two banks of cylinders with less than 180° between them driving a common crankshaft, typically arranged upright or inverted (e.g. upright
Liberty L-12
The Liberty L-12 is an American water-cooled 45° V-12 aircraft engine displacing and making designed for a high power-to-weight ratio and ease of mass production. It saw wide use in aero applications, and, once marinized Marinisation (also m ...
, inverted
Argus As 410
The Argus As 410 was a German air-cooled inverted V-12 light aircraft engine that was first produced by Argus Motoren in 1938.
Design and development
The engine marked a departure from earlier Argus engines in that it had new construction tech ...
).
![LionEngine](https://upload.wikimedia.org/wikipedia/commons/4/46/LionEngine.jpg)
;
O or Horizontally Opposed: Engines with two banks of cylinders arranged at 180° to each other driving a common crankshaft, almost universally mounted with banks horizontal for aircraft use, or with crankshaft vertical for helicopter use, (e.g. horizontally mounted
Continental O-190
The Continental O-190 (Company designations C75 and C85) is a series of engines made by Continental Motors beginning in the 1940s. Of flat-four configuration, the engines produced 75 hp (56 kW) or 85 hp (63 kW) respectively. ...
, vertically mounted
Franklin 6ACV-245).
![NapierDagger](https://upload.wikimedia.org/wikipedia/commons/b/b4/NapierDagger.JPG)
;
W:Engines with three banks driving a common crankshaft, arranged so that first and last banks are 180°or less apart, (e.g. upright
Lorraine 12Eb
The Lorraine 12E Courlis was a W-12 (broad arrow) aero engine produced by the French company Lorraine-Dietrich during the 1920s and 1930s.
Variants
;12E:
;12Eb:
;12Ebr:
;12Ed:
;12Edr:
;12Ee:
;12Ew:The standard Eb fitted with a supplementary su ...
, inverted
Napier Lioness).
;
X: Multiple bank engines with four banks arranged around a common crankshaft, usually spaced evenly, (e.g. evenly spaced
Rolls-Royce Vulture
The Rolls-Royce Vulture was a British aero engine developed shortly before World War II that was designed and built by Rolls-Royce Limited. The Vulture used the unusual " X-24" configuration, whereby four cylinder blocks derived from the Ro ...
, unevenly spaced
Napier Cub
The Napier Cub was an unusual and very large experimental 16-cylinder 'X' pattern liquid-cooled aero engine built by the British engine company D. Napier & Son. The Cub was the only Napier 'X' engine design. First flown on 15 December 1922 ...
).
![Jumo205 cutview](https://upload.wikimedia.org/wikipedia/commons/2/22/Jumo205_cutview.JPG)
;Fan: Engines with more than three banks with 180° or less between first and last bank, akin to W engines.
''Note:'' Fan engines with single cylinder banks, typically from Anzani, are usually regarded as variants of the
Radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ca ...
.
![King-Bugatti](https://upload.wikimedia.org/wikipedia/commons/b/b8/King-Bugatti.jpg)
;
U:Engines with two banks of cylinders side by side driving separate crankshafts geared to a single output, (e.g.
Bugatti U-16
The Bugatti U-16 was a 16-cylinder water-cooled double-8 vertical in-line "U engine", designed by Ettore Bugatti in 1915-1916 and built in France in small numbers. The US Bolling Commission bought a license to build the engine in the US, and sm ...
).
;
H:Engines with four banks of cylinders driving two crankshafts geared to a single output, in effect, two Opposed engines coupled together and mounted either horizontally or vertically, (e.g. horizontally
Napier Sabre, vertically
Napier Dagger
The Napier Dagger was a 24-cylinder H-pattern ''(or H-Block)'' air-cooled engine designed by Frank Halford and built by Napier before World War II. It was a development of the earlier Napier Rapier.
Design and development
The H-Block has a ...
).
;
Opposed piston
An opposed-piston engine is a piston engine in which each cylinder has a piston at both ends, and no cylinder head. Petrol and diesel opposed-piston engines have been used mostly in large-scale applications such as ships, military tanks, and ...
:Two-stroke engines, typically compression ignition/Diesel, with a single bank of cylinders driving two crankshafts where the pistons travel towards each other forming single combustion chambers, (e.g.
Jumo 207).
:Deltic: Engines with three banks of opposed piston cylinders arranged in a triangle with three crankshafts geared to drive a single output,(e.g.
Napier Deltic
The Napier Deltic engine is a British opposed-piston valveless, supercharged uniflow scavenged, two-stroke diesel engine used in marine and locomotive applications, designed and produced by D. Napier & Son. Unusually, the cylinders were disp ...
)
:Rhomboidal: Engines with four or more banks of opposed piston cylinders arranged in a square with four crankshafts geared to drive a single output,(e.g.
Jumo 223)
''Note:'' There is no theoretical limit to the number banks in an opposed piston engine, limitations include cost, complexity and reliability.
;Multiple bank:Engines with more than two banks, arranged around a common axis and/or crankshaft with more than 180° between first and last banks.
:Star: Multiple bank engines with an even number of banks (more than four) arranged around a common axis and/or driving a common crankshaft with more than 180° between first and last banks, (e.g.
Jumo 222
The Jumo 222 was a German high-power multiple-bank in-line piston aircraft engine from Junkers, designed under the management of Ferdinand Brandner of the Junkers Motorenwerke.
Such was the projected performance of the engine compared to con ...
,
Dobrynin VD-4K
The Dobrynin VD-4K was a Soviet six-bank, 24-cylinder, turbo-compound, inline engine developed after the end of World War II. It was superseded by turboprop engines before it could be widely used.
Development
The VD-4K, originally designated as t ...
).
![Jumo 222 E links](https://upload.wikimedia.org/wikipedia/commons/b/b7/Jumo_222_E_links.JPG)
:
Inline Radial: Multiple bank engines, usually liquid-cooled, with an odd number of banks (three or more) arranged around a common axis and/or driving a common crankshaft with more than 180° between first and last banks, (e.g. air-cooled
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 ...
, liquid-cooled
BMW 803).
''Note'' The BMW 803 is not only an inline radial engine but is also a coupled engine with two engines arranged back to back on a common axis driving separate co-axial propellers through a common gearbox.
Inverted engine
![Argus AS 10 Aviaticum](https://upload.wikimedia.org/wikipedia/commons/f/f2/Argus_AS_10_Aviaticum.JPG)
An upright engine has the cylinder heads directly above the crankshaft. By contrast an inverted engine has the cylinder heads directly beneath it. In the inverted V layout, the cylinders angle downwards instead of upwards.
For an aero engine, advantages of the inverted layout include improved access to cylinder heads and manifolds for the ground crew,
having the centre of mass of a multi-bank engine lower in the engine and, for engines mounted in the nose, improved visibility for the pilot and placing the widest part of a multi-bank engine closer to the midline of the fuselage, which is typically its widest point.
The
Hirth HM 60
The Hirth HM 60 was a four-cylinder inverted air-cooled inline aircraft engine designed in 1923 and first sold in 1924. The engine was of very high quality, and its sales success contributed to Hirth's rapid pre-war expansion. It was a popula ...
four-cylinder inverted inline engine was introduced in 1924, and inverted designs saw increasing popularity through the late 1920s and 30s. Widespread examples included the inline
de Havilland Gipsy Major
The de Havilland Gipsy Major or Gipsy IIIA is a four-cylinder, air-cooled, inverted inline engine used in a variety of light aircraft produced in the 1930s, including the famous Tiger Moth biplane. Many Gipsy Major engines still power vintag ...
used in the
de Havilland Tiger Moth
The de Havilland DH.82 Tiger Moth is a 1930s British biplane designed by Geoffrey de Havilland and built by the de Havilland Aircraft Company. It was operated by the Royal Air Force (RAF) and other operators as a primary trainer aircraft. ...
, and the inverted-V
Daimler-Benz DB 601
The Daimler-Benz DB 601 was a German aircraft engine built during World War II. It was a liquid-cooled inverted V12 engine, V12, and powered the Messerschmitt Bf 109, Messerschmitt Bf 110, and many others. Approximately 19,000 601's were pr ...
used in the
Messerschmitt Bf 109
The Messerschmitt Bf 109 is a German World War II fighter aircraft that was, along with the Focke-Wulf Fw 190, the backbone of the Luftwaffe's fighter force. The Bf 109 first saw operational service in 1937 during the Spanish Civil War an ...
.
References
Citations
Bibliography
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Piston engine configurations
Aircraft piston engines