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

liquid-cooled Liquid cooling refers to cooling by means of the convection or circulation of a liquid. Examples of liquid cooling technologies include: * Cooling by convection or circulation of coolant, including water cooling * Liquid cooling and ventilat ...

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 truc ...

, piston

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 many ...

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

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

. 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 and Hawker Tempest; the first aircraft powered by the Sabre was the

Napier-Heston Racer The Napier-Heston Racer, also referred to as the Heston Type 5 Racer or Heston High Speed Aircraft J.5, Clare 1976, p. 426. was a 1940s British single-seat racing monoplane first conceived by D. Napier and Son Ltd., and built by the Heston Airc ...

, 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 The Martin-Baker MB 3 was a British prototype fighter aircraft, developed from Martin-Baker’s earlier private ventures, the MB 1 and the MB 2. The design was notable for its heavy armament of six 20 mm Hispano cannons. The fatal cras ...

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 can 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 turbine engine that drives an aircraft propeller. A turboprop consists of an intake, reduction gearbox, compressor, combustor, turbine, and a propelling nozzle. Air enters the intake and is compressed by the compressor. ...

engines such as the

Naiad In Greek mythology, the naiads (; grc-gre, ναϊάδες, naïádes) 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 ...

and Eland.

Design and development

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

Lion The lion (''Panthera leo'') is a large cat of the genus '' Panthera'' native to Africa and India. It has a muscular, broad-chested body; short, rounded head; round ears; and a hairy tuft at the end of its tail. It is sexually dimorphic; adu ...

, which had been a very successful engine between the World Wars and in modified form had powered several of the Supermarine Schneider Trophy competitors in 1923 and 1927, as well as several

land speed record The land speed record (or absolute land speed record) is the highest speed achieved by a person using a vehicle on land. There is no single body for validation and regulation; in practice the Category C ("Special Vehicles") flying start regul ...

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 and the H-24

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

. 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 (international spelling) or liter (American English 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 metre (m3 ...

). 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 displaces and its bore and stroke are both . The design traces its history to 1929 experiments at Pratt & Whitney on twin-row designs. Production be ...

''Twin Wasp'', developed about 1,200 hp (895 kW) 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 percent 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 engines would be unlikely to produce much more than 1,500 hp (1,100 kW), 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, as well as to decrease the engine's sensitivity to detonation, which was prevalent with the poor quality fuels in use at the time. Halford had worked for Ricardo 1919-1922 at their 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 2,000 hp (1,491 kW) 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 and the Bristol Centaurus 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 1,350 hp (1,000 kW). By March, they were passing tests at 2,050 hp (1,500 kW) 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, that existed from 1918 to 1964. It was under the political authority of the Secretary of Stat ...

's 100-hour test, the first production versions were delivering 2,200 hp (1,640 kW) from their 2,238 cubic inch (37 litre) displacements. By the end of the year, they were producing 2,400 hp (1,800 kW). The contemporary 1940

Rolls-Royce Merlin The Rolls-Royce Merlin is a British liquid-cooled V-12 piston aero engine of 27-litres (1,650 cu in) capacity. Rolls-Royce designed the engine and first ran it in 1933 as a private venture. Initially known as the PV-12, it was late ...

II was generating just over 1,000 hp (750 kW) 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

.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 a ...

from their 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 many large birds of prey of the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. Most of the 68 species of eagle are from Eurasia and Africa. Outside this area, j ...

. 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. The current categorisation is that a supercharger is a form of forced indu ...

, 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 2,400

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 t ...

(1,800 kW) consistently and the reputation of the engine started to improve. This was the last version to enter service, being used in the Hawker Typhoon and its derivative, the Hawker Tempest. 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, ...

s, notably by the RAF Second Tactical Air Force. The Tempest became the principal destroyer of the

V-1 flying bomb The V-1 flying bomb (german: Vergeltungswaffe 1 "Vengeance Weapon 1") was an early cruise missile. Its official Reich Aviation Ministry () designation was Fi 103. It was also known to the Allies as the buzz bomb or doodlebug and in Germany ...

( Fieseler Fi 103), 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 ''Schwalbe'' (German: " Swallow") in fighter versions, or ''Sturmvogel'' (German: " Storm Bird") in fighter-bomber versions, is a fighter aircraft and fighter-bomber that was designed and produced by the Ge ...

jet aircraft. Development continued and the later Sabre VII delivered 3,500 hp (2,600 kW) 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 four-row, 28-cylinder radial produced 3,000 hp (2,280 kW) at first and later types produced 3,800 hp (2,834 kW), 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) 2,000 horsepower (1,490 kW). ;Sabre II :(1940) 2,300 horsepower (1,715 kW). Experimental 0.332:1 propeller reduction gear ratio. ;Sabre II (production variant) :2,200 horsepower (1,640 kW). Reduction gear ratio 0.274:1: mainly used in early Hawker Typhoons. ;Sabre IIA :2,235 horsepower (1,665 kW). Revised ignition system: maximum boost +9 lbs. ;Sabre IIB :2,400 horsepower (1,790 kW). Four choke S.U. carburettor: Mainly used in Hawker Tempest V.Flight 1945, p. 551. ;Sabre IIC :2,065 horsepower (1,540 kW). Similar to Mk VII. NapierSabreIII

;Sabre III :2,250 horsepower (1,680 kW). Similar to Mk IIA, tailored for the Blackburn Firebrand: 25 manufactured and installed. ;Sabre IV :2,240 horsepower (1,670 kW). As Mk VA with Hobson fuel injection: preliminary flight development engine for Sabre V series. Used in Hawker Tempest I. ;Sabre V :2,600 horsepower (1,940 kW). Developed MK II, redesigned supercharger with increased boost, redesigned induction system. ;Sabre VA :2,600 horsepower (1,940 kW). Mk V with Hobson-R.A.E fuel injection, single-lever throttle and propeller control: used in Hawker Tempest VI. ;Sabre VI :2,310 horsepower (1,720 kW). 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 :3,055 horsepower (2,278 kW). Mk VA strengthened to withstand high powers produced using Water/Methanol injection. Larger supercharger impeller. ;Sabre VIII :3,000 horsepower (2,240 kW). Intended for Hawker Fury; tested in the Folland Fo.108. ;Sabre E.118 :(1941) Three-speed, two-stage supercharger, contra-rotating propeller; 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 multiple aircraft, including the two widely deployed fighters.

Applications - widely deployed

* Hawker Tempest * Hawker Typhoon

Applications - 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 ...

, testbed * Folland Fo.108, testbed * Hawker Fury, prototype (2 built (LA610, VP207), 485 mph) *

, prototype *

, prototype * Vickers Warwick, prototype

Restoration project and engines on display

;Under restoration: * Canadian Aviation Heritage Centre, Macdonald Campus,

McGill University McGill University (french: link=no, Université McGill) is an English-language public research university located in Montreal, Quebec, Canada. Founded in 1821 by royal charter granted by King George IV,Frost, Stanley Brice. ''McGill Univer ...

Montréal Montreal ( ; officially Montréal, ) is the second-most populous city in Canada and most populous city in the Canadian province of Quebec. Founded in 1642 as '' Ville-Marie'', or "City of Mary", it is named after Mount Royal, the triple-p ...

.CAHC "Workshop One"
Retrieved: 21 November 2009. * Sabre IIa, Serial Number 2484
Hawker Typhoon Preservation Group
RB396, UK ;Preserved on public display: * Solent Sky (example on loan from

Birmingham Museum of Science and Industry Thinktank, Birmingham (formerly known as simply Thinktank) is a science museum in Birmingham, England. Opened in 2001, it is part of Birmingham Museums Trust and is located within the Millennium Point complex on Curzon Street, Digbeth. His ...

) * Fantasy of Flight, 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 Imperial War Museums (IWM) is a British national museum organisation with branches at five locations in England, three of which are in London. Founded as the Imperial War Museum in 1917, the museum was intended to record the civil and military ...

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 th ...

(donated by Cambridge University Engineering Department) * Royal Air Force Museum London * London Science Museum * World of WearableArt & Classic Cars Museum, Nelson *

Canada Aviation and Space Museum The Canada Aviation and Space Museum (french: link=no, Musée de l'Aviation et de l'Espace du Canada) (formerly the Canada Aviation Museum and National Aeronautical Collection) is Canada's national aviation history museum. The museum is locate ...

, 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'' advertisement for the Sabre engine {{Napierengines

Sabre A sabre (French: �sabʁ or saber in American English) is a type of backsword with a curved blade associated with the light cavalry of the early modern and Napoleonic periods. Originally associated with Central European cavalry such as t ...

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