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 turbines , although a few have been rocket powered and in recent years many small UAVs have used electric motors .
118-472: The Rolls-Royce Falcon is an aero engine developed in 1915. It was a smaller version of the Rolls-Royce Eagle , a liquid-cooled V-12 of 867 cu in (14.2 L ) capacity . Fitted to many British World War I -era aircraft, production ceased in 1927. The Falcon was designed by R.W. Harvey-Bailey. An airworthy Falcon survives today and powers a Bristol F.2 Fighter during summer displays. Production of
236-443: A gas turbine engine offered. Thus was born the idea to mate a turbine engine to a traditional propeller. Because gas turbines optimally spin at high speed, a turboprop features a gearbox to lower the speed of the shaft so that the propeller tips don't reach supersonic speeds. Often the turbines that drive the propeller are separate from the rest of the rotating components so that they can rotate at their own best speed (referred to as
354-476: A "universal" propeller shaft, allowing either de Havilland or Rotol manufactured propellers to be used. The first major version to incorporate changes brought about through experience in operational service was the XX, which was designed to run on 100- octane fuel. This fuel allowed higher manifold pressures , which were achieved by increasing the boost from the centrifugal supercharger . The Merlin XX also utilised
472-934: A Merlin X with a two-speed supercharger in high gear generated 1,150 hp (860 kW) at 15,400 feet (4,700 m) and 1,160 hp (870 kW) at 16,730 feet (5,100 m). From late 1939, 100-octane fuel became available from the U.S., West Indies , Persia , and, in smaller quantities, domestically, consequently, "... in the first half of 1940 the RAF transferred all Hurricane and Spitfire squadrons to 100 octane fuel." Small modifications were made to Merlin II and III series engines, allowing an increased (emergency) boost pressure of +12 pounds per square inch (183 kPa; 1.85 atm). At this power setting these engines were able to produce 1,310 hp (980 kW) at 9,000 ft (2,700 m) while running at 3,000 revolutions per minute. Increased boost could be used indefinitely as there
590-618: A better efficiency. A hybrid system as emergency back-up and for added power in take-off is offered for sale by Axter Aerospace, Madrid, Spain. Small multicopter UAVs are almost always powered by electric motors. Reaction engines generate the thrust to propel an aircraft by ejecting the exhaust gases at high velocity from the engine, the resultant reaction of forces driving the aircraft forwards. The most common reaction propulsion engines flown are turbojets, turbofans and rockets. Other types such as pulsejets , ramjets , scramjets and pulse detonation engines have also flown. In jet engines
708-613: A build-up of lead in the combustion chambers, causing excessive fouling of the spark plugs . Better results were achieved by adding 2.5% mono methyl aniline (M.M.A.) to 100-octane fuel. The new fuel allowed the five-minute boost rating of the Merlin 66 to be raised to +25 pounds per square inch (272 kPa; 2.7 atm). With this boost rating the Merlin 66 generated 2,000 hp (1,500 kW) at sea level and 1,860 hp (1,390 kW) at 10,500 ft (3,200 m). Starting in March 1944,
826-419: A combustion section where fuel is added and ignited, one or more turbines that extract power from the expanding exhaust gases to drive the compressor, and an exhaust nozzle that accelerates the exhaust gases out the back of the engine to create thrust. When turbojets were introduced, the top speed of fighter aircraft equipped with them was at least 100 miles per hour faster than competing piston-driven aircraft. In
944-555: A common crankshaft. The vast majority of V engines are water-cooled. The V design provides a higher power-to-weight ratio than an inline engine, while still providing a small frontal area. Perhaps the most famous example of this design is the legendary Rolls-Royce Merlin engine, a 27-litre (1649 in ) 60° V12 engine used in, among others, the Spitfires that played a major role in the Battle of Britain . A horizontally opposed engine, also called
1062-490: A cooling system into the air duct of a hydrogen jet engine permits greater fuel injection at high speed and obviates the need for the duct to be made of refractory or actively cooled materials. This greatly improves the thrust/weight ratio of the engine at high speed. It is thought that this design of engine could permit sufficient performance for antipodal flight at Mach 5, or even permit a single stage to orbit vehicle to be practical. The hybrid air-breathing SABRE rocket engine
1180-440: A cylinder on the other side. Opposed, air-cooled four- and six-cylinder piston engines are by far the most common engines used in small general aviation aircraft requiring up to 400 horsepower (300 kW) per engine. Aircraft that require more than 400 horsepower (300 kW) per engine tend to be powered by turbine engines . An H configuration engine is essentially a pair of horizontally opposed engines placed together, with
1298-408: A flat or boxer engine, has two banks of cylinders on opposite sides of a centrally located crankcase. The engine is either air-cooled or liquid-cooled, but air-cooled versions predominate. Opposed engines are mounted with the crankshaft horizontal in airplanes , but may be mounted with the crankshaft vertical in helicopters . Due to the cylinder layout, reciprocating forces tend to cancel, resulting in
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#17328562019791416-558: A fraction of the cost of traditional engines. Such conversions first took place in the early 1970s; and as of 10 December 2006 the National Transportation Safety Board has only seven reports of incidents involving aircraft with Mazda engines, and none of these is of a failure due to design or manufacturing flaws. The most common combustion cycle for aero engines is the four-stroke with spark ignition. Two-stroke spark ignition has also been used for small engines, while
1534-407: A free-turbine engine). A turboprop is very efficient when operated within the realm of cruise speeds it was designed for, which is typically 200 to 400 mph (320 to 640 km/h). Turboshaft engines are used primarily for helicopters and auxiliary power units . A turboshaft engine is similar to a turboprop in principle, but in a turboprop the propeller is supported by the engine and the engine
1652-451: A handful of types are still in production. The last airliner that used turbojets was the Concorde , whose Mach 2 airspeed permitted the engine to be highly efficient. A turbofan engine is much the same as a turbojet, but with an enlarged fan at the front that provides thrust in much the same way as a ducted propeller , resulting in improved fuel efficiency . Though the fan creates thrust like
1770-457: A higher altitude of over 19,000 ft (5,800 m); and also improved the design of both the impeller, and the diffuser which controlled the airflow to it. These modifications led to the development of the single-stage Merlin XX and 45 series. A significant advance in supercharger design was the incorporation in 1938 of a two-speed drive (designed by the French company Farman ) to the impeller of
1888-516: A new 1,100 hp (820 kW)-class design known as the PV-12, with PV standing for Private Venture, 12-cylinder , as the company received no government funding for work on the project. The PV-12 was first run on 15 October 1933 and first flew in a Hawker Hart biplane ( serial number K3036 ) on 21 February 1935. The engine was originally designed to use the evaporative cooling system then in vogue. This proved unreliable and when ethylene glycol from
2006-560: A peak pressure of 30 MPa (300 bar). Although engine weight increases by 30%, aircraft fuel consumption is reduced by 15%. Sponsored by the European Commission under Framework 7 project LEMCOTEC , Bauhaus Luftfahrt, MTU Aero Engines and GKN Aerospace presented the concept in 2015, raising the overall engine pressure ratio to over 100 for a 15.2% fuel burn reduction compared to 2025 engines. On multi-engine aircraft, engine positions are numbered from left to right from
2124-478: A piston-engine with two 10 piston banks without a high-pressure turbine, increasing efficiency with non-stationary isochoric - isobaric combustion for higher peak pressures and temperatures. The 11,200 lb (49.7 kN) engine could power a 50-seat regional jet . Its cruise TSFC would be 11.5 g/kN/s (0.406 lb/lbf/hr) for an overall engine efficiency of 48.2%, for a burner temperature of 1,700 K (1,430 °C), an overall pressure ratio of 38 and
2242-493: A problem after some months due to the physical and mental effects of wartime conditions such as the frequent occupation of air-raid shelters . It was agreed to cut the punishing working hours slightly to 82 hours a week, with one half-Sunday per month awarded as holiday. Record production is reported to have been 100 engines in one day. Immediately after the war the site repaired and overhauled Merlin and Griffon engines, and continued to manufacture spare parts. Finally, following
2360-424: A propeller, the surrounding duct frees it from many of the restrictions that limit propeller performance. This operation is a more efficient way to provide thrust than simply using the jet nozzle alone, and turbofans are more efficient than propellers in the transsonic range of aircraft speeds and can operate in the supersonic realm. A turbofan typically has extra turbine stages to turn the fan. Turbofans were among
2478-425: A search for replacement fuels for general aviation aircraft a priority for pilots’ organizations. Turbine engines and aircraft diesel engines burn various grades of jet fuel . Jet fuel is a relatively less volatile petroleum derivative based on kerosene , but certified to strict aviation standards, with additional additives. Model aircraft typically use nitro engines (also known as "glow engines" due to
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#17328562019792596-404: A smooth running engine. Opposed-type engines have high power-to-weight ratios because they have a comparatively small, lightweight crankcase. In addition, the compact cylinder arrangement reduces the engine's frontal area and allows a streamlined installation that minimizes aerodynamic drag. These engines always have an even number of cylinders, since a cylinder on one side of the crankcase "opposes"
2714-524: Is a pre-cooled engine under development. At the April 2018 ILA Berlin Air Show , Munich -based research institute de:Bauhaus Luftfahrt presented a high-efficiency composite cycle engine for 2050, combining a geared turbofan with a piston engine core. The 2.87 m diameter, 16-blade fan gives a 33.7 ultra-high bypass ratio , driven by a geared low-pressure turbine but the high-pressure compressor drive comes from
2832-449: Is a twin-spool engine, allowing only two different speeds for the turbines. Pulsejets are mechanically simple devices that—in a repeating cycle—draw air through a no-return valve at the front of the engine into a combustion chamber and ignite it. The combustion forces the exhaust gases out the back of the engine. It produces power as a series of pulses rather than as a steady output, hence the name. The only application of this type of engine
2950-486: Is above and behind. In the Cessna 337 Skymaster , a push-pull twin-engine airplane, engine No. 1 is the one at the front of the fuselage, while engine No. 2 is aft of the cabin. Aircraft reciprocating (piston) engines are typically designed to run on aviation gasoline . Avgas has a higher octane rating than automotive gasoline to allow higher compression ratios , power output, and efficiency at higher altitudes. Currently
3068-453: Is bolted to the airframe : in a turboshaft, the engine does not provide any direct physical support to the helicopter's rotors. The rotor is connected to a transmission which is bolted to the airframe, and the turboshaft engine drives the transmission. The distinction is seen by some as slim, as in some cases aircraft companies make both turboprop and turboshaft engines based on the same design. A number of electrically powered aircraft, such as
3186-400: Is located above the cylinders, it is called an inverted inline engine: this allows the propeller to be mounted high up to increase ground clearance, enabling shorter landing gear. The disadvantages of an inline engine include a poor power-to-weight ratio , because the crankcase and crankshaft are long and thus heavy. An in-line engine may be either air-cooled or liquid-cooled, but liquid-cooling
3304-714: Is more common because it is difficult to get enough air-flow to cool the rear cylinders directly. Inline engines were common in early aircraft; one was used in the Wright Flyer , the aircraft that made the first controlled powered flight. However, the inherent disadvantages of the design soon became apparent, and the inline design was abandoned, becoming a rarity in modern aviation. For other configurations of aviation inline engine, such as X-engines , U-engines , H-engines , etc., see Inline engine (aeronautics) . Cylinders in this engine are arranged in two in-line banks, typically tilted 60–90 degrees apart from each other and driving
3422-400: Is not limited to engines with a single row of cylinders. This is typically to differentiate them from radial engines . A straight engine typically has an even number of cylinders, but there are instances of three- and five-cylinder engines. The greatest advantage of an inline engine is that it allows the aircraft to be designed with a low frontal area to minimize drag. If the engine crankshaft
3540-495: Is not the case because the output of the engine depends solely on the mass of air it can be made to consume efficiently, and in this respect the supercharger plays the most important role ... the engine has to be capable of dealing with the greater mass flows with respect to cooling, freedom from detonation and capable of withstanding high gas and inertia loads ... During the course of research and development on superchargers it became apparent to us that any further increase in
3658-430: Is of lesser concern, rocket engines can be useful because they produce very large amounts of thrust and weigh very little. A rocket turbine engine is a combination of two types of propulsion engines: a liquid-propellant rocket and a turbine jet engine. Its power-to-weight ratio is a little higher than a regular jet engine, and works at higher altitudes. For very high supersonic/low hypersonic flight speeds, inserting
Rolls-Royce Falcon - Misplaced Pages Continue
3776-608: The Air Ministry had provided a total of £1,927,000 by December 1939. Having a workforce that consisted mainly of design engineers and highly skilled men, the Derby factory carried out the majority of development work on the Merlin, with flight testing carried out at nearby RAF Hucknall . All the Merlin-engined aircraft taking part in the Battle of Britain had their engines assembled in the Derby factory. Total Merlin production at Derby
3894-452: The Air Ministry , the Ministry of Aircraft Production and local authority officials. Hives was an advocate of shadow factories , and, sensing the imminent outbreak of war, pressed ahead with plans to produce the Merlin in sufficient numbers for the rapidly expanding Royal Air Force. Despite the importance of uninterrupted production, several factories were affected by industrial action . By
4012-466: The Battle of Britain Memorial Flight , and power many restored aircraft in private ownership worldwide. In the early 1930s, Rolls-Royce started planning its future aero-engine development programme and realised there was a need for an engine larger than their 21-litre (1,296 cu in) Kestrel , which was being used with great success in a number of 1930s aircraft. Consequently, work was started on
4130-513: The QinetiQ Zephyr , have been designed since the 1960s. Some are used as military drones . In France in late 2007, a conventional light aircraft powered by an 18 kW electric motor using lithium polymer batteries was flown, covering more than 50 kilometers (31 mi), the first electric airplane to receive a certificate of airworthiness . On 18 May 2020, the Pipistrel E-811 was
4248-670: The Rutan Quickie . The single-rotor engine was put into a Chevvron motor glider and into the Schleicher ASH motor-gliders. After the demise of MidWest, all rights were sold to Diamond of Austria, who have since developed a MkII version of the engine. As a cost-effective alternative to certified aircraft engines some Wankel engines, removed from automobiles and converted to aviation use, have been fitted in homebuilt experimental aircraft . Mazda units with outputs ranging from 100 horsepower (75 kW) to 300 horsepower (220 kW) can be
4366-587: The Second Tactical Air Force (2TAF) also began using 100/150 grade fuel. This fuel was also offered to the USAAF where it was designated "PPF 44-1" and informally known as "Pep". Production of the Rolls-Royce Merlin was driven by the forethought and determination of Ernest Hives , who at times was enraged by the apparent complacency and lack of urgency encountered in his frequent correspondence with
4484-579: The Supermarine Spitfire and the Hawker Hurricane ; the latter designed in response to another specification, F36/34. Both were designed around the PV-12 instead of the Kestrel, and were the only contemporary British fighters to have been so developed. Production contracts for both aircraft were placed in 1936, and development of the PV-12 was given top priority as well as government funding. Following
4602-424: The gyroscopic effects of the heavy rotating engine produced handling problems in aircraft and the engines also consumed large amounts of oil since they used total loss lubrication, the oil being mixed with the fuel and ejected with the exhaust gases. Castor oil was used for lubrication, since it is not soluble in petrol, and the resultant fumes were nauseating to the pilots. Engine designers had always been aware of
4720-424: The oxygen necessary for fuel combustion comes from the air, while rockets carry an oxidizer (usually oxygen in some form) as part of the fuel load, permitting their use in space. A turbojet is a type of gas turbine engine that was originally developed for military fighters during World War II . A turbojet is the simplest of all aircraft gas turbines. It consists of a compressor to draw air in and compress it,
4838-494: The time between overhauls (TBO) was typically 650–800 hours depending on use. By then single-stage engines had accumulated 2,615,000 engine hours in civil operation, and two-stage engines 1,169,000. In addition, an exhaust system to reduce noise levels to below those from ejector exhausts was devised for the North Star/Argonaut. This "cross-over" system took the exhaust flow from the inboard bank of cylinders up-and-over
Rolls-Royce Falcon - Misplaced Pages Continue
4956-514: The 1,700 hp (1,300 kW) 42-litre (2,560 cu in) Rolls-Royce Vulture used four Kestrel-sized cylinder blocks fitted to a single crankcase and driving a common crankshaft, forming an X-24 layout. This was to be used in larger aircraft such as the Avro Manchester . Although the Peregrine appeared to be a satisfactory design, it was never allowed to mature since Rolls-Royce's priority
5074-560: The Bentley marque and the factory. Today it is known as Bentley Crewe. Hives further recommended that a factory be built near Glasgow to take advantage of the abundant local work force and the supply of steel and forgings from Scottish manufacturers. In September 1939, the Air Ministry allocated £4,500,000 for a new Shadow factory. This government -funded and -operated factory was built at Hillington starting in June 1939 with workers moving into
5192-804: The Clerget 14F Diesel radial engine (1939) has the same power to weight ratio as a gasoline radial. Improvements in Diesel technology in automobiles (leading to much better power-weight ratios), the Diesel's much better fuel efficiency and the high relative taxation of AVGAS compared to Jet A1 in Europe have all seen a revival of interest in the use of diesels for aircraft. Thielert Aircraft Engines converted Mercedes Diesel automotive engines, certified them for aircraft use, and became an OEM provider to Diamond Aviation for their light twin. Financial problems have plagued Thielert, so Diamond's affiliate — Austro Engine — developed
5310-550: The Falcon began in September 1916 and was so successful that it was also manufactured under licence by Brazil Straker in Bristol. Production continued until 1927, by which time 2,185 had been built. An unusual feature of this engine was the epicyclic propeller reduction gear which contained a clutch designed to limit the maximum torque , thus protecting the reduction gears. The Falcon
5428-421: The Merlin 130/131 versions specifically designed for the de Havilland Hornet . Ultimately, during tests conducted by Rolls-Royce at Derby , an RM.17.SM (the high altitude version of the Merlin 100-Series) achieved 2,640 hp (1,970 kW) at 36 lb boost (103"Hg) on 150-octane fuel with water injection. With the end of the war, work on improving Merlin power output was halted and the development effort
5546-462: The Merlin 60 series gained 300 hp (220 kW) at 30,000 ft (9,100 m) over the Merlin 45 series, at which altitude a Spitfire IX was nearly 70 mph (110 km/h) faster than a Spitfire V. The two-stage Merlin family was extended in 1943 with the Merlin 66, which had its supercharger geared for increased power ratings at low altitudes, and the Merlin 70 series that were designed to deliver increased power at high altitudes. While
5664-472: The Merlin 66-powered Spitfire IXs of two Air Defence of Great Britain (ADGB) squadrons were cleared to use the new fuel for operational trials, and it was put to good use in the summer of 1944 when it enabled Spitfire L.F. Mk. IXs to intercept V-1 flying bombs coming in at low altitudes. 100/150 grade fuel was also used by Mosquito night fighters of the ADGB to intercept V-1s. In early February 1945, Spitfires of
5782-408: The Merlin X. The later Merlin XX incorporated the two-speed drive as well as several improvements that enabled the production rate of Merlins to be increased. The low-ratio gear, which operated from takeoff to an altitude of 10,000 ft (3,000 m), drove the impeller at 21,597 rpm and developed 1,240 hp (920 kW) at that height; while the high gear's (25,148 rpm) power rating
5900-553: The Merlin ran only on 100-octane fuel, and the five-minute combat limitation was raised to +18 pounds per square inch (224 kPa; 2.3 atm). In late 1943 trials were run of a new "100/150" grade (150-octane) fuel, recognised by its bright-green colour and "awful smell". Initial tests were conducted using 6.5 cubic centimetres (0.23 imp fl oz ) of tetraethyllead (T.E.L.) for every one imperial gallon of 100-octane fuel (or 1.43 cc/L or 0.18 U.S. fl oz/U.S. gal), but this mixture resulted in
6018-514: The Merlin were the Fairey Battle , Hawker Hurricane and Supermarine Spitfire . The Merlin remains most closely associated with the Spitfire and Hurricane, although the majority of the production run was for the four-engined Avro Lancaster heavy bomber. The Merlin continued to benefit from a series of rapidly-applied developments, derived from experiences in use since 1936. These markedly improved
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#17328562019796136-516: The Merlin's components itself. Hillingdon required "a great deal of attention from Hives" from when it was producing its first complete engine; it had the highest proportion of unskilled workers in any Rolls-Royce-managed factory”. Engines began to leave the production line in November 1940, and by June 1941 monthly output had reached 200, increasing to more than 400 per month by March 1942. In total 23,675 engines were produced. Worker absenteeism became
6254-425: The Merlin's technical improvements resulted from more efficient superchargers , designed by Stanley Hooker , and the introduction of aviation fuel with increased octane ratings . Numerous detail changes were made internally and externally to the engine to withstand increased power ratings and to incorporate advances in engineering practices. The Merlin consumed an enormous volume of air at full power (equivalent to
6372-402: The Peregrine and Vulture were both cancelled in 1943, and by mid-1943 the Merlin was supplemented in service by the larger Griffon . The Griffon incorporated several design improvements and ultimately superseded the Merlin. Initially the new engine was plagued with problems such as failure of the accessory gear trains and coolant jackets. Several different construction methods were tried before
6490-520: The Spitfire used a variation of this exhaust system fitted with forward-facing intake ducts to distribute hot air out to the wing-mounted guns to prevent freezing and stoppages at high altitudes, replacing an earlier system that used heated air from the engine coolant radiator. The latter system had become ineffective due to improvements to the Merlin itself which allowed higher operating altitudes where air temperatures are lower . Ejector exhausts were also fitted to other Merlin-powered aircraft. Central to
6608-444: The U.S. became available, the engine was adapted to use a conventional liquid-cooling system. The Hart was subsequently delivered to Rolls-Royce where, as a Merlin testbed , it completed over 100 hours of flying with the Merlin C and E engines. In 1935, the Air Ministry issued a specification, F10/35 , for new fighter aircraft with a minimum airspeed of 310 mph (500 km/h ). Fortunately, two designs had been developed:
6726-557: The Wankel engine has been used in motor gliders where the compactness, light weight, and smoothness are crucially important. The now-defunct Staverton-based firm MidWest designed and produced single- and twin-rotor aero engines, the MidWest AE series . These engines were developed from the motor in the Norton Classic motorcycle . The twin-rotor version was fitted into ARV Super2s and
6844-477: The altitude performance of the Merlin engine necessitated the employment of a two-stage supercharger. As the Merlin evolved so too did the supercharger; the latter fitting into three broad categories: The Merlin supercharger was originally designed to allow the engine to generate maximum power at an altitude of about 16,000 ft (4,900 m). In 1938 Stanley Hooker, an Oxford graduate in applied mathematics, explained "... I soon became very familiar with
6962-475: The basic design of the Merlin was set. Early production Merlins were unreliable: common problems were cylinder head cracking, coolant leaks, and excessive wear to the camshafts and crankshaft main bearings . The prototype, developmental, and early production engine types were the: The Merlin II and III series were the first main production versions of the engine. The Merlin III was the first version to incorporate
7080-466: The company convention of naming its piston aero engines after birds of prey, Rolls-Royce named the engine the Merlin after a small, Northern Hemisphere falcon ( Falco columbarius ). Two more Rolls-Royce engines developed just prior to the war were added to the company's range. The 885 hp (660 kW) Rolls-Royce Peregrine was an updated, supercharged development of their V-12 Kestrel design, while
7198-500: The compression-ignition diesel engine is seldom used. Starting in the 1930s attempts were made to produce a practical aircraft diesel engine . In general, Diesel engines are more reliable and much better suited to running for long periods of time at medium power settings. The lightweight alloys of the 1930s were not up to the task of handling the much higher compression ratios of diesel engines, so they generally had poor power-to-weight ratios and were uncommon for that reason, although
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#17328562019797316-488: The construction of the Merlin supercharger and carburettor ... Since the supercharger was at the rear of the engine it had come in for pretty severe design treatment, and the air intake duct to the impeller looked very squashed ..." Tests conducted by Hooker showed the original intake design was inefficient, limiting the performance of the supercharger. Hooker subsequently designed a new air intake duct with improved flow characteristics, which increased maximum power at
7434-576: The cylinders arranged evenly around the crankshaft, although some early engines, sometimes called semi-radials or fan configuration engines, had an uneven arrangement. The best known engine of this type is the Anzani engine, which was fitted to the Bleriot XI used for the first flight across the English Channel in 1909. This arrangement had the drawback of needing a heavy counterbalance for the crankshaft, but
7552-486: The cylinders in a circle around the crankcase, as in a radial engine, (see above), but the crankshaft is fixed to the airframe and the propeller is fixed to the engine case, so that the crankcase and cylinders rotate. The advantage of this arrangement is that a satisfactory flow of cooling air is maintained even at low airspeeds, retaining the weight advantage and simplicity of a conventional air-cooled engine without one of their major drawbacks. The first practical rotary engine
7670-480: The design of the two-stage supercharger forged ahead, Rolls-Royce also continued to develop the single-stage supercharger, resulting in 1942 in the development of a smaller "cropped" impeller for the Merlin 45M and 55M; both of these engines developed greater power at low altitudes. In squadron service the LF.V variant of the Spitfire fitted with these engines became known as the "clipped, clapped, and cropped Spitty" to indicate
7788-533: The end of its production run in 1950, 168,176 Merlin engines had been built; over 112,000 in Britain and more than 55,000 under licence in the U.S. The existing Rolls-Royce facilities at Osmaston, Derby were not suitable for mass engine production although the floor space had been increased by some 25% between 1935 and 1939; Hives planned to build the first two or three hundred engines there until engineering teething troubles had been resolved. To fund this expansion,
7906-506: The engine and first ran it in 1933 as a private venture. Initially known as the PV-12 , it was later called Merlin following the company convention of naming its four-stroke piston aero engines after birds of prey . The engine benefitted from the racing experiences of precursor engines in the 1930s. After several modifications, the first production variants of the PV-12 were completed in 1936. The first operational aircraft to enter service using
8024-469: The engine before discharging the exhaust stream on the outboard side of the UPP nacelle. As a result, sound levels were reduced by between 5 and 8 decibels . The modified exhaust also conferred an increase in horsepower over the unmodified system of 38 hp (28 kW), resulting in a 5 knot improvement in true air speed. Still-air range of the aircraft was also improved by around 4 per cent. The modified engine
8142-581: The engine core is the bypass ratio. Low-bypass engines are preferred for military applications such as fighters due to high thrust-to-weight ratio, while high-bypass engines are preferred for civil use for good fuel efficiency and low noise. High-bypass turbofans are usually most efficient when the aircraft is traveling at 500 to 550 miles per hour (800 to 890 kilometres per hour), the cruise speed of most large airliners. Low-bypass turbofans can reach supersonic speeds, though normally only when fitted with afterburners . The term advanced technology engine refers to
8260-438: The engine works by having a coiled pipe in the combustion chamber that superheats the fuel (propane) before being injected into the air-fuel inlet. In the combustion chamber, the fuel/air mixture ignites and burns, creating thrust as it leaves through the exhaust pipe. Induction and compression of the fuel/air mixture is done both by the pressure of propane as it is injected, along with the sound waves created by combustion acting on
8378-415: The engine's heat-radiating surfaces to the air and tends to cancel reciprocating forces, radials tend to cool evenly and run smoothly. The lower cylinders, which are under the crankcase, may collect oil when the engine has been stopped for an extended period. If this oil is not cleared from the cylinders prior to starting the engine, serious damage due to hydrostatic lock may occur. Most radial engines have
8496-666: The engine's performance and durability. Starting at 1,000 horsepower (750 kW) for the first production models, most late war versions produced just under 1,800 horsepower (1,300 kW), and the very latest version as used in the de Havilland Hornet over 2,000 horsepower (1,500 kW). One of the most successful aircraft engines of the World War II era, some 50 versions of the Merlin were built by Rolls-Royce in Derby , Crewe and Glasgow , as well as by Ford of Britain at their Trafford Park factory , near Manchester . A de-rated version
8614-596: The first electric aircraft engine to be awarded a type certificate by EASA for use in general aviation . The E-811 powers the Pipistrel Velis Electro . Limited experiments with solar electric propulsion have been performed, notably the manned Solar Challenger and Solar Impulse and the unmanned NASA Pathfinder aircraft. Many big companies, such as Siemens, are developing high performance electric engines for aircraft use, also, SAE shows new developments in elements as pure Copper core electric motors with
8732-399: The first engines to use multiple spools —concentric shafts that are free to rotate at their own speed—to let the engine react more quickly to changing power requirements. Turbofans are coarsely split into low-bypass and high-bypass categories. Bypass air flows through the fan, but around the jet core, not mixing with fuel and burning. The ratio of this air to the amount of air flowing through
8850-428: The fuel supply line together with a diaphragm fitted in the float chamber, jocularly nicknamed " Miss Shilling's orifice ", after its inventor, went some way towards curing fuel starvation in a dive by containing fuel under negative G; however, at less than maximum power a fuel-rich mixture still resulted. Another improvement was made by moving the fuel outlet from the bottom of the S.U. carburettor to exactly halfway up
8968-526: The great Ford factory at Manchester started production, Merlins came out like shelling peas ...". Some 17,316 people worked at the Trafford Park plant, including 7,260 women and two resident doctors and nurses. Merlin production started to run down in August 1945, and finally ceased on 23 March 1946. Total Merlin production at Trafford Park was 30,428. As the Merlin was considered to be so important to
9086-492: The intake stacks. It was intended as a power plant for personal helicopters and compact aircraft such as Microlights. A few aircraft have used rocket engines for main thrust or attitude control, notably the Bell X-1 and North American X-15 . Rocket engines are not used for most aircraft as the energy and propellant efficiency is very poor, but have been employed for short bursts of speed and takeoff. Where fuel/propellant efficiency
9204-428: The level maximum speed of the Spitfire by 10 mph (16 km/h) to 360 mph (580 km/h). The first versions of the ejector exhausts featured round outlets, while subsequent versions of the system used "fishtail" style outlets, which marginally increased thrust and reduced exhaust glare for night flying. In September 1937 the Spitfire prototype, K5054 , was fitted with ejector type exhausts. Later marks of
9322-467: The major Western manufacturers of turbofan engines are Pratt & Whitney (a subsidiary of Raytheon Technologies ), General Electric , Rolls-Royce , and CFM International (a joint venture of Safran Aircraft Engines and General Electric). Russian manufacturers include the United Engine Corporation , Aviadvigatel and Klimov . Aeroengine Corporation of China was formed in 2016 with
9440-430: The many limitations of the rotary engine so when the static style engines became more reliable and gave better specific weights and fuel consumption, the days of the rotary engine were numbered. The Wankel is a type of rotary engine. The Wankel engine is about one half the weight and size of a traditional four-stroke cycle piston engine of equal power output, and much lower in complexity. In an aircraft application,
9558-481: The maximum boost pressure at which the engine could be run using 87-octane fuel was +6 pounds per square inch (141 kPa; 1.44 atm ). However, as early as 1938, at the 16th Paris Air Show , Rolls-Royce displayed two versions of the Merlin rated to use 100-octane fuel. The Merlin R.M.2M was capable of 1,265 hp (943 kW) at 7,870 feet (2,400 m), 1,285 hp (958 kW) at 9,180 feet (2,800 m) and 1,320 hp (980 kW) on take-off; while
9676-462: The merger of several smaller companies. The largest manufacturer of turboprop engines for general aviation is Pratt & Whitney. General Electric announced in 2015 entrance into the market. In this section, for clarity, the term "inline engine" refers only to engines with a single row of cylinders, as used in automotive language, but in aviation terms, the phrase "inline engine" also covers V-type and opposed engines (as described below), and
9794-433: The modern generation of jet engines. The principle is that a turbine engine will function more efficiently if the various sets of turbines can revolve at their individual optimum speeds, instead of at the same speed. The true advanced technology engine has a triple spool, meaning that instead of having a single drive shaft, there are three, in order that the three sets of blades may revolve at different speeds. An interim state
9912-463: The most common Avgas is 100LL. This refers to the octane rating (100 octane) and the lead content (LL = low lead, relative to the historic levels of lead in pre-regulation Avgas). Refineries blend Avgas with tetraethyllead (TEL) to achieve these high octane ratings, a practice that governments no longer permit for gasoline intended for road vehicles. The shrinking supply of TEL and the possibility of environmental legislation banning its use have made
10030-404: The new AE300 turbodiesel , also based on a Mercedes engine. Competing new Diesel engines may bring fuel efficiency and lead-free emissions to small aircraft, representing the biggest change in light aircraft engines in decades. While military fighters require very high speeds, many civil airplanes do not. Yet, civil aircraft designers wanted to benefit from the high power and low maintenance that
10148-424: The number of required sub-contracted parts such as crankshafts, camshafts and cylinder liners eventually fell short and the factory was expanded to manufacture these parts "in house". Initially the local authority promised to build 1,000 new houses to accommodate the workforce by the end of 1938, but by February 1939 it had only awarded a contract for 100. Hives was incensed by this complacency and threatened to move
10266-476: The oil leaks that had been a problem with the early Merlin I, II and III series. The process of improvement continued, with later versions running on higher octane ratings, delivering more power. Fundamental design changes were also made to all key components, again increasing the engine's life and reliability. By the end of the war the "little" engine was delivering over 1,600 hp (1,200 kW) in common versions, and as much as 2,030 hp (1,510 kW) in
10384-479: The point of view of the pilot looking forward, so for example on a four-engine aircraft such as the Boeing 747 , engine No. 1 is on the left side, farthest from the fuselage, while engine No. 3 is on the right side nearest to the fuselage. In the case of the twin-engine English Electric Lightning , which has two fuselage-mounted jet engines one above the other, engine No. 1 is below and to the front of engine No. 2, which
10502-432: The power-to-weight ratio is very important, making the Wankel engine a good choice. Because the engine is typically constructed with an aluminium housing and a steel rotor, and aluminium expands more than steel when heated, a Wankel engine does not seize when overheated, unlike a piston engine. This is an important safety factor for aeronautical use. Considerable development of these designs started after World War II , but at
10620-632: The premises in October, one month after the outbreak of war. The factory was fully occupied by September 1940. A housing crisis also occurred at Glasgow, where Hives again asked the Air Ministry to step in. With 16,000 employees, the Glasgow factory was one of the largest industrial operations in Scotland. Unlike the Derby and Crewe plants, which relied significantly on external subcontractors , it produced almost all
10738-511: The production of the Rolls-Royce Avon turbojet and others, the factory was closed in 2005. The Ford Motor Company was asked to produce Merlins at Trafford Park , Stretford , near Manchester , and building work on a new factory was started in May 1940 on a 118-acre (48 ha) site. Built with two distinct sections to minimise potential bomb damage, it was completed in May 1941 and bombed in
10856-402: The prototype high-altitude Vickers Wellington V bomber, Rolls-Royce started experiments on the design of a two-stage supercharger and an engine fitted with this was bench-tested in April 1941, eventually becoming the Merlin 60. The basic design used a modified Vulture supercharger for the first stage while a Merlin 46 supercharger was used for the second. A liquid-cooled intercooler on top of
10974-473: The same month. At first, the factory had difficulty in attracting suitable labour, and large numbers of women, youths and untrained men had to be taken on. Despite this, the first Merlin engine came off the production line one month later and it was building the engine at a rate of 200 per week by 1943, at which point the joint factories were producing 18,000 Merlins per year. In his autobiography Not much of an Engineer , Sir Stanley Hooker states: "... once
11092-471: The shortened wingspan , the less-than-perfect condition of the used airframes , and the cropped supercharger impeller. The use of carburettors was calculated to give a higher specific power output, due to the lower temperature, hence greater density, of the fuel/air mixture compared to injected systems. Initially Merlins were fitted with float controlled carburettors. However, during the Battle of Britain it
11210-437: The side, which allowed the fuel to flow equally well under negative or positive g. Further improvements were introduced throughout the Merlin range: 1943 saw the introduction of a Bendix-Stromberg pressure carburettor that injected fuel at 5 pounds per square inch (34 kPa ; 0.34 bar ) through a nozzle directly into the supercharger, and was fitted to Merlin 66, 70, 76, 77 and 85 variants. The final development, which
11328-431: The success of the Merlin was the supercharger. A.C. Lovesey , an engineer who was a key figure in the design of the Merlin, delivered a lecture on the development of the Merlin in 1946; in this extract he explained the importance of the supercharger: The impression still prevails that the static capacity known as the swept volume is the basis of comparison of the possible power output for different types of engine, but this
11446-425: The supercharger casing was used to prevent the compressed air/fuel mixture from becoming too hot. Also considered was an exhaust-driven turbocharger , but although a lower fuel consumption was an advantage, the added weight and the need to add extra ducting for the exhaust flow and waste-gates meant that this option was rejected in favour of the two-stage supercharger. Fitted with the two-stage two-speed supercharger,
11564-439: The time the aircraft industry favored the use of turbine engines. It was believed that turbojet or turboprop engines could power all aircraft, from the largest to smallest designs. The Wankel engine did not find many applications in aircraft, but was used by Mazda in a popular line of sports cars . The French company Citroën had developed Wankel powered RE-2 [ fr ] helicopter in 1970's. In modern times
11682-414: The two crankshafts geared together. This type of engine has one or more rows of cylinders arranged around a centrally located crankcase . Each row generally has an odd number of cylinders to produce smooth operation. A radial engine has only one crank throw per row and a relatively small crankcase, resulting in a favorable power-to-weight ratio . Because the cylinder arrangement exposes a large amount of
11800-408: The two-speed superchargers designed by Rolls-Royce, resulting in increased power at higher altitudes than previous versions. Another improvement, introduced with the Merlin X, was the use of a 70%–30% water-glycol coolant mix rather than the 100% glycol of the earlier versions. This substantially improved engine life and reliability, removed the fire hazard of the flammable ethylene glycol , and reduced
11918-567: The use of a glow plug ) powered by glow fuel , a mixture of methanol , nitromethane , and lubricant. Electrically powered model airplanes and helicopters are also commercially available. Small multicopter UAVs are almost always powered by electricity, but larger gasoline-powered designs are under development. Rolls-Royce Merlin The Rolls-Royce Merlin is a British liquid-cooled V-12 piston aero engine of 27-litre (1,650 cu in) capacity . Rolls-Royce designed
12036-403: The volume of a single-decker bus per minute), and with the exhaust gases exiting at 1,300 mph (2,100 km/h) it was realised that useful thrust could be gained simply by angling the gases backwards instead of venting sideways. During tests, 70 pounds-force (310 N ; 32 kgf ) thrust at 300 mph (480 km/h), or roughly 70 hp (52 kW) was obtained, which increased
12154-625: The war effort, negotiations were started to establish an alternative production line outside the UK. Rolls-Royce staff visited North American automobile manufacturers to select one to build the Merlin in the U.S. or Canada. Henry Ford rescinded an initial offer to build the engine in the U.S. in July 1940, and the Packard Motor Car Company was selected to take on the $ 130,000,000 Merlin order (equivalent to $ 2.83 billion in 2023 dollars ). Agreement
12272-488: The whole operation, but timely intervention by the Air Ministry improved the situation. In 1940 a strike took place when women replaced men on capstan lathes , the workers' union insisting this was a skilled labour job; however, the men returned to work after 10 days. Total Merlin production at Crewe was 26,065. The factory was used postwar for the production of Rolls-Royce and Bentley motor cars and military fighting vehicle power plants. In 1998 Volkswagen AG bought
12390-399: The years after the war, the drawbacks of the turbojet gradually became apparent. Below about Mach 2, turbojets are very fuel inefficient and create tremendous amounts of noise. Early designs also respond very slowly to power changes, a fact that killed many experienced pilots when they attempted the transition to jets. These drawbacks eventually led to the downfall of the pure turbojet, and only
12508-426: Was 1,175 hp (876 kW) at 18,000 ft (5,500 m). These figures were achieved at 2,850 rpm engine speed using +9 pounds per square inch (1.66 atm ) (48") boost. In 1940, after receiving a request in March of that year from the Ministry of Aircraft Production for a high-rated (40,000 ft (12,000 m)) Merlin for use as an alternative engine to the turbocharged Hercules VIII used in
12626-522: Was 32,377. The original factory closed in March 2008, but the company maintains a presence in Derby. To meet the increasing demand for Merlin engines, Rolls-Royce started building work on a new factory at Crewe in May 1938, with engines leaving the factory in 1939. The Crewe factory had convenient road and rail links to their existing facilities at Derby. Production at Crewe was originally planned to use unskilled labour and sub-contractors with which Hives felt there would be no particular difficulty, but
12744-725: Was also the basis of the Rolls-Royce/Rover Meteor tank engine. Post-war, the Merlin was largely superseded by the Rolls-Royce Griffon for military use, with most Merlin variants being designed and built for airliners and military transport aircraft . The Packard V-1650 was a version of the Merlin built in the United States. Production ceased in 1950 after a total of almost 150,000 engines had been delivered. Merlin engines remain in Royal Air Force service today with
12862-617: Was concentrated on civil derivatives of the Merlin. Development of what became the "Transport Merlin" (TML) commenced with the Merlin 102 (the first Merlin to complete the new civil type-test requirements) and was aimed at improving reliability and service overhaul periods for airline operators using airliner and transport aircraft such as the Avro Lancastrian , Avro York (Merlin 500-series), Avro Tudor II and IV (Merlin 621), Tudor IVB and V (Merlin 623), TCA Canadair North Star (Merlin 724) and BOAC Argonaut (Merlin 724-IC). By 1951
12980-984: Was designated the "TMO" and the modified exhaust system was supplied as kit that could be installed on existing engines either by the operator or by Rolls-Royce. Power ratings for the civil Merlin 600, 620, and 621-series was 1,160 hp (870 kW) continuous cruising at 23,500 feet (7,200 m), and 1,725 hp (1,286 kW) for take-off. Merlins 622–626 were rated at 1,420 hp (1,060 kW) continuous cruising at 18,700 feet (5,700 m), and 1,760 hp (1,310 kW) for take-off. Engines were available with single-stage, two-speed supercharging (500-series), two-stage, two-speed supercharging (600-series), and with full intercooling, or with half intercooling/charge heating, charge heating being employed for cold area use such as in Canada. Civil Merlin engines in airline service flew 7,818,000 air miles in 1946, 17,455,000 in 1947, and 24,850,000 miles in 1948. From Jane's : Most of
13098-409: Was fitted to the 100-series Merlins, was an S.U. injection carburettor that injected fuel into the supercharger using a fuel pump driven as a function of crankshaft speed and engine pressures. At the start of the war, the Merlin I, II and III ran on the then standard 87-octane aviation spirit and could generate just over 1,000 hp (750 kW) from its 27-litre (1,650-cu in) displacement:
13216-462: Was found that if Spitfires or Hurricanes were to pitch nose down into a steep dive, negative g -force ( g ) produced temporary fuel starvation causing the engine to cut-out momentarily. By comparison, the contemporary Bf 109E , which had direct fuel injection , could "bunt" straight into a high-power dive to escape attack. RAF fighter pilots soon learned to avoid this with a "half-roll" of their aircraft before diving in pursuit. A restrictor in
13334-430: Was no mechanical time limit mechanism, but pilots were advised not to use increased boost for more than a maximum of five minutes, and it was considered a "definite overload condition on the engine"; if the pilot resorted to emergency boost he had to report this on landing, when it was noted in the engine log book, while the engineering officer was required to examine the engine and reset the throttle gate. Later versions of
13452-516: Was notably used in the Bristol F.2 Fighter and Blackburn Kangaroo bomber. Note: List from Guttery and Lumsden: Bristol F.2B Fighter, D-8096 , is based at the Shuttleworth Collection and is powered by a Falcon III, this aircraft flies regularly in summer. Data from Jane's and Lumsden . Related development Related lists Aircraft engine In commercial aviation
13570-580: Was refining the Merlin. As a result, the Peregrine saw use in only two aircraft: the Westland Whirlwind fighter and one of the Gloster F.9/37 prototypes. The Vulture was fitted to the Avro Manchester bomber, but proved unreliable in service and the planned fighter using it – the Hawker Tornado – was cancelled as a result. With the Merlin itself soon pushing into the 1,500 hp (1,100 kW) range,
13688-562: Was the Gnome Omega designed by the Seguin brothers and first flown in 1909. Its relative reliability and good power to weight ratio changed aviation dramatically. Before the first World War most speed records were gained using Gnome-engined aircraft, and in the early years of the war rotary engines were dominant in aircraft types for which speed and agility were paramount. To increase power, engines with two rows of cylinders were built. However,
13806-475: Was the German unmanned V1 flying bomb of World War II . Though the same engines were also used experimentally for ersatz fighter aircraft, the extremely loud noise generated by the engines caused mechanical damage to the airframe that was sufficient to make the idea unworkable. The Gluhareff Pressure Jet (or tip jet) is a type of jet engine that, like a valveless pulsejet, has no moving parts. Having no moving parts,
13924-487: Was used to avoid the spark plugs oiling up. In military aircraft designs, the large frontal area of the engine acted as an extra layer of armor for the pilot. Also air-cooled engines, without vulnerable radiators, are slightly less prone to battle damage, and on occasion would continue running even with one or more cylinders shot away. However, the large frontal area also resulted in an aircraft with an aerodynamically inefficient increased frontal area. Rotary engines have
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