The de Havilland Gipsy Six is a British

six-cylinder The straight-six engine (also referred to as an inline-six engine; abbreviated I6 or L6) is a piston engine with six cylinders arranged in a straight line along the crankshaft. A straight-six engine has perfect primary and secondary engine balan ...

air-cooled Air-cooled engines rely on the circulation of air directly over heat dissipation fins or hot areas of the engine to cool them in order to keep the engine within operating temperatures. In all combustion engines, a great percentage of the heat ge ...

, inverted inline

piston 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 ...

developed by the

de Havilland Engine Company The de Havilland Engine Company was an offshoot of the de Havilland aircraft building company, which started life as the 'Engine Division of the de Havilland Aircraft Company' in 1926 producing the famous de Havilland Gipsy aero-engine. The c ...

for aircraft use in the 1930s. It was based on the cylinders of the

four-cylinder The engine configuration describes the fundamental operating principles by which internal combustion engines are categorized. Piston engines are often categorized by their cylinder layout, valves and camshafts. Wankel engines are often categorize ...

Gipsy Major and went on to spawn a whole series of similar aero engines that were still in common use until the 1980s. The engines were of particular note for their exceptionally low cross-sectional area, a drag-reducing feature which made them ideal for the many racing aircraft of that period. In 1934, the basic bronze-headed Gipsy Six, rated at 185

horsepower Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are the ...

(138 kW) at 2,100 rpm was modified for use in the DH.88 Comet air racer as the Gipsy Six "R" which produced 223 horsepower (166 kW) at 2,400 rpm for takeoff. Many Gipsy Six engines remain in service powering vintage aircraft types today.

Design and development

The

De Havilland Engine Company The de Havilland Engine Company was an offshoot of the de Havilland aircraft building company, which started life as the 'Engine Division of the de Havilland Aircraft Company' in 1926 producing the famous de Havilland Gipsy aero-engine. The c ...

company had hoped to produce a version of the basic engine capable of utilising a hydraulically actuated

variable-pitch In marine propulsion, a variable-pitch propeller is a type of propeller with blades that can be rotated around their long axis to change the blade pitch. Reversible propellers—those where the pitch can be set to negative values—can also ...

(VP) airscrew based on the American Hamilton "Bracket-Type" in time for the 1934 MacRobertson Race. Since there was so little time to perfect this installation, as a compromise, a French "

Ratier Ratier-Figeac is an aircraft components manufacturer in Figeac, France. From 1926 until 1930 it also built a car with a 746 cc overhead camshaft engine. From 1959 until 1962 Ratier made motorcycles, having taken over the motorcycle business of th ...

" VP airscrew was fitted to the Comets' "R" engines, which utilised a simple air-filled bladder for a once-per-flight automatic pitch change. Later on, Comets were fitted with the Series II engine, which eliminated this crude system. Power for the "R" was increased to a takeoff rating of by increasing the

compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stati ...

s from 5.25:1 to 6.5:1, while fitting

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

alloy

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, domed-

piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tig ...

s and modified

valve gear The valve gear of a steam engine is the mechanism that operates the inlet and exhaust valves to admit steam into the cylinder and allow exhaust steam to escape, respectively, at the correct points in the cycle. It can also serve as a reversing ...

. Production of the basic fixed-pitch Gipsy Six unit began in 1935, with the engines rated at at 2,400 rpm for takeoff. This was quickly followed by production of the Gipsy Six Series II for use with the hydraulically actuated airscrews that de Havilland were by then producing under a licence acquired from

Hamilton Standard Hamilton Standard was an American aircraft propeller parts supplier. It was formed in 1929 when United Aircraft and Transport Corporation consolidated Hamilton Aero Manufacturing and Standard Steel Propeller into the Hamilton Standard Propeller C ...

in 1934. This was effectively the engine that the company did not have time to develop for the 1934 MacRobertson race, but without the significant increase in compression-ratio needed for the Comet - being 6:1 - compared to the Six-R's 6.5:1. The Series II unit, while superficially similar to its predecessor, utilised a hollow, splined

crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting ...

to permit the fitting of the VP airscrew utilising boosted pressurised oil from the engine's

dry-sump A dry-sump system is a method to manage the lubricating motor oil in four-stroke and large two-stroke piston driven internal combustion engines. The dry-sump system uses two or more oil pumps and a separate oil reservoir, as opposed to a co ...

lubrication Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology. Lubrication mechanisms such as fluid-lubric ...

system via a pilot-operated control valve. As well as differences to the

crankcase In a piston engine, the crankcase is the housing that surrounds the crankshaft. In most modern engines, the crankcase is integrated into the engine block. Two-stroke engines typically use a crankcase-compression design, resulting in the fuel/a ...

and crankshaft, different cylinder barrels, pistons and aluminium cylinder heads were utilised. There was also an added, very limited ability provided on the Series II to run accessories. The "pilot-friendly"

constant speed unit In aeronautics, a variable-pitch propeller is a type of propeller (airscrew) with blades that can be rotated around their long axis to change the blade pitch. A controllable-pitch propeller is one where the pitch is controlled manually by the ...

s (CSUs) were not available for these engines until 1939. The Series II was also equipped with AMC (Automatic Mixture Control) a

barometric A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...

device, without which it was exceedingly difficult to adjust for a correct mixture with a CSU fitted. This feature was also carried over onto the similar

Queen II ''Queen II'' is the second studio album by the British rock band Queen. It was released on 8 March 1974 by EMI Records in the UK and Elektra Records in the US. It was recorded at Trident Studios and Langham 1 Studios, London, in August 1973 wi ...

. Pilots were then able to simply select the required RPM and Boost pressure required. This reduction in over-leaning also tended to extend the TBO (time between overhauls). The twin down-draught,

Claudel-Hobson Claudel-Hobson was a series of British carburettors manufactured by H. M. Hobson Ltd. Introduced in 1908, they were widely used on British car and aircraft engines in the early 20th century. Applications included Sunbeam automobiles as well as ...

A.I.48

carburetter A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meterin ...

s were common to all these engines. The induction system was designed to automatically obviate the effects of carburetter icing - a dangerous problem that still plagues most piston engines in current worldwide use in 2008, more than 70 years later. Alfa Romeo built two engine types based on the Gipsy Six design, the

Alfa Romeo 110 The Alfa Romeo 110 was an Italian four cylinder air-cooled inverted inline engine for aircraft use, mainly for trainers and light aircraft. The Alfa Romeo 110 was based on the de Havilland Gipsy Major, with approximately 500 units produced. Deriv ...

and

Alfa Romeo 115 The Alfa Romeo 115 was an Italian six-cylinder air-cooled inverted inline engine for aircraft use, mainly for training and light planes, based on the de Havilland Gipsy Six engine. Production totalled approximately 1,600 units. Derivatives of th ...

Type history

The series of engines proved to be reliable, and the

time between overhaul Time between overhauls (abbreviated as TBO or TBOH) is the manufacturer's recommended number of running hours or calendar time before an aircraft engine or other component requires overhaul. On rotorcraft, many components have recommended or man ...

(TBO) was more than doubled within a few years. The

Achilles' heel An Achilles' heel (or Achilles heel) is a weakness in spite of overall strength, which can lead to downfall. While the mythological origin refers to a physical vulnerability, idiomatic references to other attributes or qualities that can lead to ...

of the engine, its lack of facilities for running ancillary items, an increasing requirement during the 1930s, remained so. It was subsequently addressed on the similar Gypsy Queen III and Queen II engines developed for military applications. Later developments, such as the postwar Queen 30 and Queen 70 series engines took the rated power from up to nearly . While new designs, these still used all of the same basic configurations of the original Gipsy Six of the mid-1930s and were in use by operators such as the

Royal Air Force The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and ...

(RAF) and

Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...

(RN) until the 1980s. Today, with de Havilland having long disappeared, very few of these engines remain in use and only a few specialist facilities can carry out overhauls.

Variants

;Gipsy Six I :Bronze

s, 200hp. For fixed-pitch airscrews. ;Gipsy Six Series II :Aluminium cylinder heads, designed for leaded fuel. 210 hp. For VP airscrews. ;Gipsy Six 'R' :Racing engine with high lift

camshaft A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems ...

. 220 hp. For VP airscrews. ; Gipsy Queen :Military version of Gipsy Six;- Queen I;- 200hp. Small number produced. Similar to Queen II, but not provided with facility for a VP airscrew. Queen III;- 205 hp, Military version of the Six Series I, for fixed-pitch airscrews. Queen II;- The military version of the Gipsy Six Series II was the Queen II for VP airscrews, 210hp. Both the Queen II and the Queen III had strengthened crankcases. Later versions of the Queen III & Queen II had extra facilities for driving accessories. Later Queens from the Queen 30 onwards differed substantially, and whilst looking similar were in fact entirely new engines. ;IAR 6-G1 :Licence-built by

Industria Aeronautică Română Industria Aeronautică Română (IAR) (now IAR S.A. Brașov) or Romanian Aeronautic Industry in English, is a Romanian aerospace manufacturer. It is based in Ghimbav, near Brașov, Romania. IAR was founded in 1925 with the aid of the Romanian go ...

;

:Alfa Romeo licence production/derivative

Applications

* ASJA Viking II *

Caproni Ca.308 Borea The Caproni Ca.308 ''Borea'' ("North Wind") was a small airliner built in Italy in the mid-1930s. Development The Ca.308 was a streamlined, low-wing cantilevered monoplane design of conventional configuration. Its undercarriage was not retrac ...

* Cierva W.9 * de Havilland Dragon Six *

de Havilland Dragon Rapide The de Havilland DH.89 Dragon Rapide is a 1930s short-haul biplane airliner developed and produced by British aircraft company de Havilland. Capable of accommodating 6–8 passengers, it proved an economical and durable craft, despite its rela ...

de Havilland Express The de Havilland Express, also known as the de Havilland D.H.86, was a four-engined passenger aircraft manufactured by the de Havilland Aircraft Company between 1934 and 1937. Development During 1933, talks between the governments of United ...

* de Havilland DH.88 * IAR 27 * Koolhoven F.K.57 *

Miles Mentor The Miles M.16 Mentor was a 1930s British single-engined three-seat monoplane training and communications aircraft built by Miles Aircraft Limited. Design and development The origins of the Mentor can be traced back to the Air Ministry's relea ...

Parnall Heck The Parnall Heck was a 1930s United Kingdom, British four-seat cabin monoplane built by Parnall, Parnall Aircraft Limited at Yate, Gloucestershire. Originally a Hendy design, few were built. It combined the strength and comfort of a cabin aircra ...

Percival Mew Gull The Percival Mew Gull was a British racing aircraft of the 1930s. It was a small, single-engine, single-seat, low-wing monoplane of wooden construction, normally powered by a six-cylinder de Havilland Gipsy Six piston engine. During its racin ...

Percival Petrel The Percival Q.6 was a 1930s British communications aircraft built by Percival Aircraft Limited at Luton. Originally, the Percival Q.6 was a civil transport but It was used during the Second World War by the Royal Air Force and Royal Navy as a ...

Percival Vega Gull The Percival Vega Gull was a 1930s British, four-seater touring aircraft built by Percival Aircraft Limited. It was a single-engine, low-wing (Folding), wood-and-fabric monoplane with a fixed tailwheel undercarriage. Design and development ...

* Rogožarski SIM-XII-H *

Tugan Gannet The Tugan LJW7 Gannet, also known later as the Wackett Gannet after its designer Lawrence Wackett, was a small twin-engined airliner built by Tugan Aircraft in Australia in the 1930s.Watkins 1961, p.600Australian Academy of Technological Science ...

Survivors

Gipsy Six engines remain in service worldwide as of April 2010. Twelve Gipsy Six-powered

aircraft are on the

Civil Aviation Authority A civil aviation authority (CAA) is a national or supranational statutory authority that oversees the regulation of civil aviation, including the maintenance of an aircraft register. Role Due to the inherent dangers in the use of flight vehicles, ...

register although not all are currently airworthy.G-INFO - UK CAA database - Dragon Rapide
www.caa.co.uk. Retrieved: 14 April 2010

Engines on display

A preserved Gipsy Six engine is on public display at the

Shuttleworth Collection The Shuttleworth Collection is a working aeronautical and automotive collection located at the Old Warden Aerodrome, Old Warden in Bedfordshire, England. It is the oldest in the world and one of the most prestigious, due to the variety of old a ...

Old Warden Old Warden is a village and civil parishes in England, civil parish in the Central Bedfordshire district of the county of Bedfordshire, England, about south-east of the county town of Bedford. The 2011 census shows its population as 328. The ...

Bedfordshire Bedfordshire (; abbreviated Beds) is a ceremonial county in the East of England. The county has been administered by three unitary authorities, Borough of Bedford, Central Bedfordshire and Borough of Luton, since Bedfordshire County Council wa ...

, another is on display at the

Science Museum, London The Science Museum is a major museum on Exhibition Road in South Kensington, London. It was founded in 1857 and is one of the city's major tourist attractions, attracting 3.3 million visitors annually in 2019. Like other publicly funded ...

. The

National Military Museum, Romania The King Ferdinand I National Military Museum ( ro, Muzeul Militar Național "Regele Ferdinand I"), located at 125-127 Mircea Vulcănescu St., Bucharest, Romania, was established on 18 December 1923 by King Ferdinand I. It has been at its present ...

displays an engine cut open.

Specifications (Gipsy Six I)

References

Notes

Bibliography

* Gunston, Bill. ''World Encyclopedia of Aero Engines''. Wellingborough, UK: Patrick Stephens, 1986, p. 50. . * ''Jane's Fighting Aircraft of World War II''. London. Studio Editions Ltd, 1989.

External links

Royal Air Force Museum Aero Engine Collection - Inline Engines
{{DHaeroengines Air-cooled aircraft piston engines

Gipsy Six The de Havilland Gipsy Six is a British six-cylinder, air-cooled, inverted inline piston engine developed by the de Havilland Engine Company for aircraft use in the 1930s. It was based on the cylinders of the four-cylinder Gipsy Major and w ...

1930s aircraft piston engines Inverted aircraft piston engines Straight-six engines