hispano-suiza v8 aero engine

7/30/2019 Hispano-Suiza V8 Aero Engine

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Hispano-Suiza V8 Aero Engine
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HistoryWhen World War I began, production lines of the Hispano-Suiza company were stopped to allow production of war material. Marc Birkigt began work on an aero enginebased on his successful V8 automobile engine. The resulting engine, called the Hispano-Suiza 8A (or HS-8A), made its first appearance in February 1915 and was a promisingdesign.

The first Hispano-Suiza Hisso 8A kept the standard configuration of Birkigt's existing design: eight cylinders in 90 Vee configuration, a displacement of 11.76 litres (717.8 cuin) and a power output of 140 hp at 1,900 rpm. In spite of the similarities with the original design, the engine had been substantially refined. The cylinder blocks were made ofa solid piece of steel. The engine block and the cylinder heads were made of aluminium and were coated in vitreous enamel to reduce leakage. All parts subject to wear weremade redundant: spark plugs, valve springs, magnetos, etc . All moving parts were f itted in a case/oil pan to protect them.

Although engine reliability was a great concern in these opening stages of aviation, the HS-8A also provided good power-to-weight ratio and development potential. Theengine and its accessories weighed 185 kg (408 lb), making it 40% as heavy as a rotary engine of equivalent power. The design also promised far more growth potential thanrotary engines which (in spite of being the most common type then in use with airplanes) were getting close to the limits of the type. Rotary engines of increased powergenerally had increased weight, which in turn increased the already important gyroscopic torque generated by the engine's rotation. A further increase in torque wasconsidered not acceptable, and the power-to-weight ratio of the new rotary engines under development did not appeal to aircraft designers.

The new engine was presented to the French Ministre de la Guerre (Ministry of War) in February 1915, and tested for 15 hours at full power. This was standard procedure fora new engine design to be admitted in military service. However, because of lobbying by competing engine manufacturers, the H S-8A was ordered to undergo a bench test thatno French-made engine had yet achieved successfully: a 50-hour run at full speed. The HS-8A was therefore sent back to Chalais-Meudon on July 21, 1915 and tested for 50hours, succeeding against all expectations.


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In such a context, it is hardly surprising that French officials ordered production of the HS-8A to be started as soon as possible and emitted a requirement for a new single-seat high-performance fighter aircraft using the new engine. The SPAD VII was the result of this requirement and would allow the Allies to regain air superiority over theGermans.

The HS-8Aa, which entered production in July 1915, was the production variant of the basic HS-8A type, with increased power output: 150 hp (110 kW) at 2,000 rpm. EarlyHS-8A engines were plagued with various problems which required further work. The 150-hp HS-8Aa was the standard powerplant for early-production SPAD VIIs. Thedemand for the Hispano-Suiza engine was such that other manufacturers began producing it under license, in France, Great-Britain (Wolseley in Birmingham), Italy (Nagliatiin Florence and Itala/SCAT in Turin) and Russia. Total production of the HS-8Aa amounted to some 6,000 engines.

The HS-8Ab was yet another evolution of the HS-8A. By increasing the compression ratio from 4.7 to 5.3, Birkigt was able to increase the power output to 180 hp (132 kW) at2,100 rpm. The HS-8Ab began replacing the 8Aa on SPAD VIIs in early 1917.

Hispano-Suiza 8beThe HS-8Ab had been plagued by engine failures due t o the high compression ratio: piston heads were sometimes pierced and seized the engine. To further increase the poweroutput of the engine, Birkigt chose to increase engine speed. Two versions of the HS-8B were made. The first, the HS-8Ba, kept the 4.7 compression ratio of the HS-8Aa butdelivered 200 hp (147 kW) at 2,300 rpm. The second version, the HS-8Bb, had a compression ratio of 5.3. A reduction gear (3:4 ratio) was fitted to compensate for theincreased engine speed. However the reduction gear system was fragile, and often broke down, sometimes with spectacular results ending up with the entire propeller,driveshaft and driven gear parting company from the airframe. Progressive refinement of the engine brought the available power to 235 hp by the end of 1917.

The HS-8B was used to power the earliest versions of the S.E.5a, all examples of the SPAD S.XII and SPAD S.XIII, front-line versions of the Sopwith Dolphin and several otherAllied aircraft types, with its gear reduction easily identifiable in vintage WW I photos, from its use of a clockwise rotation propeller.

The HS-8F was basically an enlarged version of the HS-8B for use on bombers. The displacement was increased to 18.5 litres (1,127.3 cu in), with a power of 300 hp (220 kW)at 2,100 rpm (equal to 750 ft lbs torque). The engine now weighed 256 kg (564 lb) and was not suitable for aerobatics, hence its use on bombers and reconnaissance aircraft.Engine speed being inferior to that of the HS-8B, the reduction gear was dispensed of, hereby increasing engine reliability.

SummarySometimes referred to as the "Rolls-Royce Merlin of World War I", the Hispano-Suiza HS-8 engine was one of the most important powerplants to be produced during the First

World War. A total of 49,800 engines were built by Hispano-Suiza and French manufacturers. Derivatives of the engine were also used abroad to power numerous aircrafttypes and the engine can be considered as the ancestor of another successful engine by the same designer, the Hispano-Suiza HS-12 which served in World War Two.

MODEL 8A 8Aa 8Ab 8B 8F

Bore (mm) 120 120 120 120 140

Stroke (mm) 130 130 130 130 150

Displacement (litres) 11.76 11.76 11.76 11.76 18.47

Compression ratio 4.7 4.7 5.3 5.3 5.3

Length (metres) 1.19 1.25 1.31 1.36 1.32

Width (metres) 0.81 0.83 0.85 0.86 0.89

Height (metres) 0.77 0.81 0.87 0.90 0.88
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Weight (kg) 195 215 230 236 256

Power output (hp) 140 150 180 200/235 300

RPM 1900 2000 2100 2300 2100


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The Hispano-Suiza Engine

Fig 1. The Hispano-Suiza Aviation Engine. (Photo: Griff Wason Art & Illustration.)
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In 1915, Marc Birgikt, an automotive engine designer, created the Hispano-Suiza (Spanish-Swiss

named for the financial backers), 150 hp, V-8 water-cooled, aircraft engine. It was often referred to as

the Hisso engine, and the first plant was located in Barcelona, Spain. After outgrowing the capacity of

the original plant, Hispano-Suiza engines were built under license in England, France and the United

States. Hispano built engines were considered very good engines, but licensed built Hissos were known

to be of dubious quality.

The Hisso differed form previous aero engines, by using an cast aluminum block with screwed-insteel sleeve inserts, instead of individual steel sleeves attached to the crankcase. This type of

construction made for a stong light weight engine, although it was extremely difficult to manufacture.

Aluminum casting had not yet been fully perfected, and the precision of the long fine threaded sleeves

were beyond the capabilities of most machinists at the time.1 Some of the original engine block castings

were so poor that they were often discarded.2

The Wright-Martin built Hispano-Suiza engines incorporated some improvements made by Wright

engineers in 1922, although they had to be derated to 150 hp to be of any use. Whereas, the French

production models produced 180 hp from the start.3 The Wright built engines were of too little power

for combat use and some went into Curtiss JN-4Ds. The French and British engines were also of too

poor a quality to be used in wartime.

Wright had many problems in the beginning of production, but they claimed to have produced an

aircraft engine that operated for longer periods at higher mean effective pressures than any other typeof internal combustion engine at the time. Several types weighing less than 2-1/2 pounds per

horsepower were tested for periods of from 200 to 300 hours and required little attention. The Wright

E4, with the same crankcase assembly, the cylinders only being changed, ran for 572 hours without

attention of any kind. Compared with the original Model A, built 10 years before, the new engine with

approximately the same weight and same displacement, developed one third more power, operated at

24 per cent more speed and had 3,000 per cent greater durability.
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Fig 2. Wright 200 Horsepower Aviation Engine, Model E-4 has Eight Water-cooled Cylinders in Two

Blocks of Four.

During WW I, exhaust valves, connecting rod end bearings, and spark plugs gave the most trouble asthe exhaust valves were too thin and prone to warping. Wright modified the cylinder, as shown at Fig.

3, and the use of tulip head silchrome steel valves greatly reduced valve troubles. In this respect the

Wright-Hisso was somewhat better than the original. Refinement of details of the 1,947 cubic inches

60 degree V-type 12-cylinder Wright T-3 engine enabled it to be used satisfactorily at speeds greater

than 2,200 rpm, and to develop 750 horsepower with approximately 140 pounds mean-effective

pressure at 20 per cent less weight per horsepower than that of the original engine.


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Fig 3. Wright "Tempest" E-4 water-cooled engine viewed from the rear showing magneto mounting

and water pump location.

After the Wright E2 engine, shown at Fig. 1 went out of production, it remained a popular type for

some years. This engine had practically all of the characteristics of the Hispano-Suiza as previously

described. The improved and refined Wright E4 shown at Figs. 2, 3 and 4 is the type that had beenoperated for 310 hours, before a new cylinder assembly was required, or long enough to have driven an

airplane 31,000 miles without overhauling. After a new set of cylinders had been fitted, the other parts

were run an additional amount so that the equivalent of 57,200 miles operation was obtained with only

minor external adjustments. (This statment might be exagerated, since a continuous running engine

wouldn't be under the same strain as one used for landing and takeoffs.)

The old Model A engines developed a maximum of 175 horsepower at 1,800 rpm 4, whereas the


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latest models of the same type developed a maximum of 285 horsepower at 2,300 rpm. The bore of the

E4 cylinders was 4.710 inches, the stroke was 5.110 inches and the total displacement was 718 cubic

inches. Hissos went out of production when the this amount of horsepower was suplanted by radial air-

cooled engines.

Fig 4. Top view of the Wright "Tempest" E-4 water-cooled engine showing carburetor and induction

manifolding.

Endnotes

1. Herschel Smith. The History of Aircraft Piston Engines. (Manhattan, Kansas; Sunflower University Press,

1986.) 67.2. Ed. Fay L. Faurote.Aircraft Year Book 1919. (New York: Manufacturers Aircraft Association, Inc., 1919)

277.

3. Herschel Smith. 67.4. This was the advertised hp rate. The original Wright built Hispano-Suiza engine was derated to 150 hp.


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Return To Engine Index.

Larry Dwyer.The Aviation History On-Line Museum.All rights reserved.

Updated February 16, 2010.
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hispano-suiza v8 aero engine

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