The Napier Sabre is a British H-24-cylinder, liquid-cooled,

sleeve valve The sleeve valve is a type of valve mechanism for piston engines, distinct from the usual poppet valve. Sleeve valve engines saw use in a number of pre–World War II luxury cars and in the United States in the Willys-Knight car and light tru ...

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 (engine), cylinder a ...

aero engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbin ...

, designed by Major Frank Halford and built by D. Napier & Son during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

. The engine evolved to become one of the most powerful inline piston aircraft engines in the world, developing from in its earlier versions to in late-model prototypes. The first operational aircraft to be powered by the Sabre were the

Hawker Typhoon The Hawker Typhoon was a British single-seat fighter-bomber, produced by Hawker Aircraft. It was intended to be a medium-high altitude interceptor aircraft, interceptor, as a replacement for the Hawker Hurricane, but several design problems we ...

and

Hawker Tempest The Hawker Tempest is a British fighter aircraft that was primarily used by the Royal Air Force (RAF) in the Second World War. The Tempest, originally known as the ''Typhoon II'', was an improved derivative of the Hawker Typhoon, intended to a ...

; the first aircraft powered by the Sabre was the Napier-Heston Racer, which was designed to capture the world speed record. Other aircraft using the Sabre were early prototype and production variants of the Blackburn Firebrand, the Martin-Baker MB 3 prototype and a Hawker Fury prototype. The rapid introduction of

jet engine A jet engine is a type of reaction engine, discharging a fast-moving jet (fluid), jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition may include Rocket engine, rocket, Pump-jet, water jet, and ...

s after the war led to the quick demise of the Sabre, as there was less need for high power military piston aero engines and because Napier turned its attention to developing

turboprop A turboprop is a Gas turbine, gas turbine engine that drives an aircraft Propeller (aeronautics), propeller. A turboprop consists of an intake, reduction drive, reduction gearbox, gas compressor, compressor, combustor, turbine, and a propellin ...

engines such as the

Naiad In Greek mythology, the naiads (; ), sometimes also hydriads, are a type of female spirit, or nymph, presiding over fountains, wells, springs, streams, brooks and other bodies of fresh water. They are distinct from river gods, who embodied ...

and Eland.

Design and development

Prior to the Sabre, Napier had been working on large aero engines for some time. Its most famous was the

Lion The lion (''Panthera leo'') is a large Felidae, cat of the genus ''Panthera'', native to Sub-Saharan Africa and India. It has a muscular, broad-chested body (biology), body; a short, rounded head; round ears; and a dark, hairy tuft at the ...

, which had been a very successful engine between the World Wars and in modified form had powered several of the

Supermarine Supermarine was a British aircraft manufacturer. It is most famous for producing the Spitfire fighter plane during World War II. The company built a range of seaplanes and flying boats, winning the Schneider Trophy for seaplanes with three cons ...

Schneider Trophy The Coupe d'Aviation Maritime Jacques Schneider, also known as the Schneider Trophy, Schneider Prize or (incorrectly) the Schneider Cup is a trophy that was awarded first annually, and later biennially, to the winner of a race for seaplanes and ...

competitors in 1923 and 1927, as well as several

land speed record The land speed record (LSR) or absolute land speed record is the highest speed achieved by a person using a vehicle on land. By a 1964 agreement between the Fédération Internationale de l'Automobile (FIA) and Fédération Internationale de M ...

cars. By the late 1920s, the Lion was no longer competitive and work started on replacements. Napier followed the Lion with two H-block designs: the H-16

Rapier A rapier () is a type of sword originally used in Spain (known as ' -) and Italy (known as '' spada da lato a striscia''). The name designates a sword with a straight, slender and sharply pointed two-edged long blade wielded in one hand. It wa ...

and the H-24

Dagger A dagger is a fighting knife with a very sharp point and usually one or two sharp edges, typically designed or capable of being used as a cutting or stabbing, thrusting weapon.State v. Martin, 633 S.W.2d 80 (Mo. 1982): This is the dictionary or ...

. The H-block has a compact layout, consisting of two horizontally opposed engines, one atop or beside the other. Since the cylinders are opposed, the motion in one is balanced by the motion on the opposing side, eliminating both first order and second order vibration. In these new designs, Napier chose air cooling but in service, the rear cylinders proved to be impossible to cool properly, which made the engines unreliable.

Genesis

During the 1930s, studies showed the need for engines capable of developing one horsepower per cubic inch of displacement (about 45 kW/

litre The litre ( Commonwealth spelling) or liter ( American spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metres (m3). A ...

). Such power output was needed to propel aircraft large enough to carry large fuel loads for long range flights. A typical large engine of the era, the

Pratt & Whitney R-1830 The Pratt & Whitney R-1830 Twin Wasp is an American air-cooled radial aircraft engine. It has 14 cylinders, arranged in two rings of seven. It displaces and its bore and stroke are both . The design traces its history to 1929 experiments a ...

''Twin Wasp'', developed about from 1,830

cubic inch The cubic inch (symbol in3) is a unit of volume in the Imperial units and United States customary units systems. It is the volume of a cube with each of its three dimensions (length, width, and height) being one inch long which is equivalent ...

es (30 litres), so an advance of some 50 per cent would be needed. This called for radical changes and while many companies tried to build such an engine, none succeeded. In 1927,

Harry Ricardo Sir Harry Ralph Ricardo (26 January 1885 – 18 May 1974) was an English engineer who was one of the foremost engine designers and researchers in the early years of the development of the internal combustion engine. Among his many other works, ...

published a study on the concept of the

engine. In it, he wrote that traditional

poppet valve A poppet valve (also sometimes called mushroom valve) is a valve typically used to control the timing and quantity of petrol (gas) or vapour flow into or out of an engine, but with many other applications. It consists of a hole or open-ended ch ...

engines would be unlikely to produce much more than , a figure that many companies were eyeing for next generation engines. To pass this limit, the sleeve valve would have to be used, to increase

volumetric efficiency Volumetric efficiency (VE) in internal combustion engine engineering is defined as the ratio of the equivalent volume of the fresh air drawn into the cylinder during the intake stroke (if the gases were at the reference condition for density) to th ...

, as well as to decrease the engine's sensitivity to detonation, which was prevalent with the poor quality, low-octane fuels in use at the time. Halford had worked for Ricardo 1919–1922 at its London office and Halford's 1923 office was in Ladbroke Grove, North Kensington, only a few miles from Ricardo, while Halford's 1929 office was even closer (700 yards), and while in 1927 Ricardo started work with Bristol Engines on a line of sleeve-valve designs, Halford started work with Napier, using the Dagger as the basis. The layout of the H-block, with its inherent balance and the Sabre's relatively short stroke, allowed it to run at a higher rate of rotation, to deliver more power from a smaller displacement, provided that good volumetric efficiency could be maintained (with better breathing), which sleeve valves could do. The Napier company decided first to develop a large 24 cylinder liquid–cooled engine, capable of producing at least in late 1935. Although the company continued with the opposed H layout of the Dagger, this new design positioned the cylinder blocks horizontally and it was to use sleeve valves. C Sheffield23 March 1944.
2,200 h.p. Napier Sabre
''Flight'', p. 309. www.flightglobal.com. Retrieved: 9 November 2009. All of the accessories were grouped conveniently above and below the cylinder blocks, rather than being at the front and rear of the engine, as in most contemporary designs. The Air Ministry supported the Sabre programme with a development order in 1937 for two reasons: to provide an alternative engine if the

Rolls-Royce Vulture The Rolls-Royce Vulture was a British Aircraft engine, aero engine developed shortly before World War II that was designed and built by Rolls-Royce Limited. The Vulture used the unusual "X-24 engine, X-24" configuration, whereby four cylinder ...

and the

Bristol Centaurus The Centaurus was the final development of the Bristol Engine Company's series of sleeve valve radial aircraft engines. The Centaurus is an 18-cylinder, two-row design that eventually delivered over . The engine was introduced into service ...

failed as the next generation of high power engines and to keep Napier in the aero-engine industry. The first Sabre engines were ready for testing in January 1938, although they were limited to . By March, they were passing tests at and by June 1940, when the Sabre passed the

Air Ministry The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force and civil aviation that existed from 1918 to 1964. It was under the political authority of the ...

's 100-hour test, the first production versions were delivering from their 2,238 cubic inch (37 litre) displacements. By the end of the year, they were producing . The contemporary 1940

Rolls-Royce Merlin The Rolls-Royce Merlin is a British Coolant#Liquids, liquid-cooled V12 engine, V-12 Reciprocating engine, piston aero engine of 27-litre (1,650 cu in) Engine displacement, capacity. Rolls-Royce Limited, Rolls-Royce designed the engine an ...

II was generating just over from a 1,647 cubic inch (27 litre) displacement.

Production

Problems arose as soon as mass production began. Prototype engines had been hand-assembled by Napier craftsmen and it proved to be difficult to adapt it to assembly-line production techniques. The sleeves often failed due to the way they were manufactured from chrome-molybdenum steel, leading to seized cylinders, which caused the loss of the sole prototype Martin-Baker MB 3.Flight 1945, p.550. The Ministry of Aircraft Production was responsible for the development of the engine and arranged for sleeves to be machined by the

Bristol Aeroplane Company The Bristol Aeroplane Company, originally the British and Colonial Aeroplane Company, was both one of the first and one of the most important British aviation companies, designing and manufacturing both airframes and aircraft engines. Notable ...

from its Taurus engine forgings. These nitrided austenitic steel sleeves were the result of many years of intensive sleeve development, experience that Napier did not have. Air filters had to be fitted when a new sleeve problem appeared in 1944 when aircraft were operating from Normandy soil with its abrasive, gritty dust. Quality control proved to be inadequate, engines were often delivered with improperly cleaned castings, broken piston rings and machine cuttings left inside the engine.Napier Sabre
Retrieved on 17 July 2009. Mechanics were overworked trying to keep the Sabres running and during cold weather they had to run them every two hours during the night so that the engine oil would not congeal and prevent the engine from starting the next day. These problems took too long to remedy and the engine gained a bad reputation. To make matters worse, mechanics and pilots unfamiliar with the different nature of the engine, tended to blame the Sabre for problems that were caused by not following correct procedures. This was exacerbated by the representatives of the competing Rolls-Royce company, which had its own agenda. In 1944, Rolls-Royce produced a similar design prototype called the

Eagle Eagle is the common name for the golden eagle, bald eagle, and other birds of prey in the family of the Accipitridae. Eagles belong to several groups of Genus, genera, some of which are closely related. True eagles comprise the genus ''Aquila ( ...

. Napier seemed complacent and tinkered with the design for better performance. In 1942, it started a series of projects to improve its high-altitude performance, with the addition of a three-speed, two-stage

supercharger In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement (engine), displacement. It is a form of forced induction that is mechanically ...

, when the basic engine was still not running reliably. In December 1942, the company was purchased by the English Electric Company, which ended the supercharger project immediately and devoted the whole company to solving the production problems, which was achieved quickly. Napier Sabre on truck

By 1944, the Sabre V was delivering consistently and the reputation of the engine started to improve. This was the last version to enter service, being used in the

and its derivative, the

. Without the advanced supercharger, the engine's performance over fell off rapidly and pilots flying Sabre-powered aircraft, were generally instructed to enter combat only below this altitude. At low altitude, both planes were formidable. As air superiority over Continental Europe was slowly gained, Typhoons were increasingly used as

fighter-bomber A fighter-bomber is a fighter aircraft that has been modified, or used primarily, as a light bomber or attack aircraft. It differs from bomber and attack aircraft primarily in its origins, as a fighter that has been adapted into other roles, wh ...

s, notably by the

RAF Second Tactical Air Force The Second Tactical Air Force (2TAF) was one of three tactical air forces within the Royal Air Force (RAF) during and after the World War II, Second World War. It was made up of Squadron (aviation), squadrons and personnel from the RAF, other Co ...

. The Tempest became the principal destroyer of the

V-1 flying bomb The V-1 flying bomb ( "Vengeance Weapon 1") was an early cruise missile. Its official Reich Aviation Ministry () name was Fieseler Fi 103 and its suggestive name was (hellhound). It was also known to the Allies as the buzz bomb or doodlebug a ...

(

Fieseler Fi 103 The V-1 flying bomb ( "Vengeance Weapon 1") was an early cruise missile. Its official Reich Aviation Ministry () name was Fieseler Fi 103 and its suggestive name was (hellhound). It was also known to the Allies as the buzz bomb or doodlebug a ...

), since it was the fastest of all the Allied fighters at low levels. Later, the Tempest destroyed about 20

Messerschmitt Me 262 The Messerschmitt Me 262, nicknamed (German for "Swallow") in fighter versions, or ("Storm Bird") in fighter-bomber versions, is a fighter aircraft and fighter-bomber that was designed and produced by the German aircraft manufacturer Messers ...

jet aircraft. Development continued and the later Sabre VII delivered with a new supercharger. By the end of World War II, there were several engines in the same power class. The

Pratt & Whitney R-4360 Wasp Major The Pratt & Whitney R-4360 Wasp Major is an American 28-cylinder four-row radial engine, radial reciprocating engine, piston aircraft engine designed and built during World War II. At , it is the largest-displacement aviation piston engine to be ...

four-row, 28-cylinder radial produced at first and later types produced , but these required almost twice the displacement in order to do so, 4,360 cubic inches (71 litres).

Variants

Note: ;Sabre I (E.107) :(1939) . ;Sabre II :(1940) . Experimental 0.332:1 propeller reduction gear ratio. ;Sabre II (production variant) :. Reduction gear ratio 0.274:1: mainly used in early

s. ;Sabre IIA :. Revised ignition system: maximum boost +9 lbs. ;Sabre IIB :. Four choke S.U. carburettor: Mainly used in Hawker Tempest V.Flight 1945, p. 551. ;Sabre IIC :. Similar to Mk VII. NapierSabreIII

;Sabre III :. Similar to Mk IIA, tailored for the Blackburn Firebrand: 25 manufactured and installed. ;Sabre IV :. As Mk VA with Hobson fuel injection: preliminary flight development engine for Sabre V series. Used in Hawker Tempest I. ;Sabre V :. Developed MK II, redesigned supercharger with increased boost, redesigned induction system. ;Sabre VA :. Mk V with Hobson-R.A.E fuel injection, single-lever throttle and propeller control: used in Hawker Tempest VI. ;Sabre VI :. Mk VA with Rotol cooling fan: used in 2 Hawker Tempest Vs modified to use Napier designed annular radiators; also in experimental Vickers Warwick V. ;Sabre VII :. Mk VA strengthened to withstand high powers produced using Water/Methanol injection. Larger supercharger impeller. ;Sabre VIII :. Intended for Hawker Fury; tested in the Folland Fo.108. ;Sabre E.118 :(1941) Three-speed, two-stage supercharger,

contra-rotating propeller Aircraft equipped with contra-rotating propellers (CRP) coaxial contra-rotating propellers, or high-speed propellers, apply the maximum power of usually a single engine piston powered or turboprop engine to drive a pair of coaxial propellers i ...

; test flown in Fo.108. ;Sabre E.122 :(1946) 3,500 horsepower. Intended for Napier 500mph tailless fighter

Applications

The engine has been used in many aircraft, including two mass-produced fighters.

Adopted

Limited production and prototypes

* Blackburn Firebrand, only in 21 early production aircraft *

Fairey Battle The Fairey Battle is a British single-engine light bomber that was designed and manufactured by the Fairey Aviation Company. It was developed during the mid-1930s for the Royal Air Force (RAF) as a monoplane successor to the Hawker Hart and Ha ...

, test-bed * Folland Fo.108, test-bed * Hawker Fury, prototype (2 built (LA610, VP207), 485 mph) * Martin-Baker MB 3, prototype * Napier-Heston Racer, prototype *

Vickers Warwick The Vickers Warwick was a British twin-engined bomber aircraft developed and operated during the Second World War that was primarily used in other roles. In line with the naming convention followed by other RAF heavy bombers of the era, it wa ...

, prototype

Restoration project and engines on display

;Under restoration: * Canadian Aviation Heritage Centre,

Macdonald Campus The Macdonald Campus of McGill University (commonly referred to as the 'Mac Campus' or simply 'Mac') houses McGill's Faculty of Agricultural and Environmental Sciences (FAES), which includes the Institute of Parasitology, the School of Human Nutri ...

McGill University McGill University (French: Université McGill) is an English-language public research university in Montreal, Quebec, Canada. Founded in 1821 by royal charter,Frost, Stanley Brice. ''McGill University, Vol. I. For the Advancement of Learning, ...

Montréal Montreal is the List of towns in Quebec, largest city in the Provinces and territories of Canada, province of Quebec, the List of the largest municipalities in Canada by population, second-largest in Canada, and the List of North American cit ...

. Retrieved: 21 November 2009. * Sabre IIa, Serial Number 2484, Hawker Typhoon Preservation Group, RB396, UK ;Preserved on public display: *

Solent Sky Solent Sky (previously known as the Southampton Hall of Aviation) is an aviation museum in Southampton, England. The museum depicts the history of aviation in Southampton, the Solent area and Hampshire. There is a focus on Supermarine, the air ...

(example on loan from Birmingham Museum of Science and Industry) *

Fantasy of Flight Fantasy of Flight is an aviation museum in Polk City, Florida. It opened in November 1995, to house Kermit Weeks' collection of aircraft that, until Hurricane Andrew damaged many in 1992, were housed at the Weeks Air Museum in Kendall-Tamiami E ...

, Polk City, Florida * A Sabre IIA engine has been restored by the Friends Association of the Museo Nacional de Aeronáutica de Argentina and is on public display at the Engines Hall. ;Sectioned Napier engines on public display: *

Imperial War Museum The Imperial War Museum (IWM), currently branded "Imperial War Museums", is a British national museum. It is headquartered in London, with five branches in England. Founded as the Imperial War Museum in 1917, it was intended to record the civ ...

Duxford Duxford is a village in Cambridgeshire, England, about south of Cambridge. It is part of the Hundred Parishes area. History The village formed on the banks of the River Cam, a little below its emergence from the hills of north Essex. One of t ...

(donated by Cambridge University Engineering Department) *

Royal Air Force Museum London The Royal Air Force Museum London (also commonly known as the RAF Museum) is located on the former Hendon Aerodrome, in North London's Borough of Barnet. It includes five buildings and hangars showing the history of aviation and the Royal Air ...

* London Science Museum * World of WearableArt & Classic Cars Museum, Nelson *

Canada Aviation and Space Museum The Canada Aviation and Space Museum () (formerly the Canada Aviation Museum (''Musée de l'aviation du Canada'') and National Aeronautical Collection (''Collection aéronautique nationale'')) is Canada's national aviation history museum. The m ...

, Ottawa

Specifications (Sabre VA)

References

Footnotes

Notes

Bibliography

* Air Ministry. ''Pilot's Notes for Typhoon Marks IA and IB; Sabre II or IIA engine (2nd edition)''. London: Crecy Publications, 2004. * "A Real Contender (article and images)
Aeroplane
No. 452, Volume 38, Number 12, December 2010.

'' Flight and The Aircraft Engineer'' No. 1790, Volume XLIII, 15 April 1943. * Gunston, Bill. ''World Encyclopedia of Aero Engines: From the Pioneers to the Present Day''. 5th edition, Stroud, UK: Sutton, 2006. * Lumsden, Alec. ''British Piston Engines and Their Aircraft''. Marlborough, UK: Airlife Publishing, 2003. . * Mason, Francis K. ''Hawker Aircraft Since 1920 (3rd revised edition)''. London: Putnam, 1991. .
"Napier Sabre VII (article and images).
'' Flight and The Aircraft Engineer'' No. 1926, Volume XLVIII, 22 November 1945.
"Napier Flight Development (article and images on Napier's test and development centre).
'' Flight and The Aircraft Engineer'' No. 1961, Volume L, 25 July 1946. * Setright, L. J. K.: ''The Power to Fly: The Development of the Piston Engine in Aviation''. Allen & Unwin, 1971. . * Sheffield, F. C
"2,200 h.p. Napier Sabre (article and images).
'' Flight and The Aircraft Engineer'' No. 1829, Volume XLV, 13 January 1944. * Sheffield, F. C
"Napier Sabre II (article and images).
'' Flight and The Aircraft Engineer'' No. 1839, Volume XLV, 23 March 1944. * White, Graham. ''Allied Aircraft Piston Engines of World War II: History and Development of Frontline Aircraft Piston Engines Produced by Great Britain and the United States During World War II''. Warrendale, Pennsylvania: SAE International, 1995. * Reynolds, John. ''Engines and Enterprise: The Life and Work of Sir Harry Ricardo''. Stroud, UK: Sutton, 1999. * Taylor, Douglas. ''Boxkite to Jet - the remarkable career of Frank B Halford''. Derby, UK: RRHT, 1999.

External links

Napier Power Heritage Trust site

* ttp://www.airracinghistory.freeola.com/aircraft/Napier-Heston%20Racer.htm The Sabre-powered Napier-Heston Racer
The Hawker Tempest Page

A 1946 ''

Flight Flight or flying is the motion (physics), motion of an Physical object, object through an atmosphere, or through the vacuum of Outer space, space, without contacting any planetary surface. This can be achieved by generating aerodynamic lift ass ...

'' advertisement for the Sabre engine {{Napierengines

Sabre A sabre or saber ( ) is a type of backsword with a curved blade associated with the light cavalry of the Early Modern warfare, early modern and Napoleonic period, Napoleonic periods. Originally associated with Central European cavalry such a ...

Sleeve valve engines Boxer engines 1930s aircraft piston engines H engines