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116-496: The Bristol Pegasus is a British nine-cylinder, single-row, air-cooled radial aero engine . Designed by Roy Fedden of the Bristol Aeroplane Company , it was used to power both civil and military aircraft of the 1930s and 1940s. Developed from the earlier Mercury and Jupiter engines, later variants could produce 1,000 horsepower (750 kilowatts) from its capacity of 1,750 cubic inches (28 L) by use of

232-411: A 14-cylinder twin-row version of the firm's 80 hp Lambda single-row seven-cylinder rotary, however reliability and cooling problems limited its success. Two-row designs began to appear in large numbers during the 1930s, when aircraft size and weight grew to the point where single-row engines of the required power were simply too large to be practical. Two-row designs often had cooling problems with

348-451: A 9-cylinder 980 cubic inch (16.06 litre) displacement diesel radial aircraft engine, the 225 horsepower (168 kW) DR-980 , in 1928. On 28 May 1931, a DR-980 powered Bellanca CH-300 , with 481 gallons of fuel, piloted by Walter Edwin Lees and Frederick Brossy set a record for staying aloft for 84 hours and 32 minutes without being refueled. This record stood for 55 years until broken by

464-685: A 9-cylinder radial diesel aero engine, was used in the M1A1E1 , while the Continental R975 saw service in the M4 Sherman , M7 Priest , M18 Hellcat tank destroyer , and the M44 self propelled howitzer . A number of companies continue to build radials today. Vedeneyev produces the M-14P radial of 360–450 hp (270–340 kW) as used on Yakovlev and Sukhoi aerobatic aircraft. The M-14P

580-678: A build-it-yourself kit. Verner Motor of the Czech Republic builds several radial engines ranging in power from 25 to 150 hp (19 to 112 kW). Miniature radial engines for model airplanes are available from O. S. Engines , Saito Seisakusho of Japan, and Shijiazhuang of China, and Evolution (designed by Wolfgang Seidel of Germany, and made in India) and Technopower in the US. Liquid cooling systems are generally more vulnerable to battle damage. Even minor shrapnel damage can easily result in

696-668: A consequence of a favourable landing gear arrangement, having been fitted with double wheels, the bomber could operate from austere airstrips as well as rough fields or meadows. Typically amongst bombers of the late 1930s, its defensive armament consisted of only three machine guns , which subsequently proved too weak against enemy fighters in combat. Starting with a presentation at a salon in Belgrade in June 1938 and in Paris in November,

812-537: A consistent every-other-piston firing order can be maintained, providing smooth operation. For example, on a five-cylinder engine the firing order is 1, 3, 5, 2, 4, and back to cylinder 1. Moreover, this always leaves a one-piston gap between the piston on its combustion stroke and the piston on compression. The active stroke directly helps compress the next cylinder to fire, making the motion more uniform. If an even number of cylinders were used, an equally timed firing cycle would not be feasible. As with most four-strokes,

928-399: A few French-built examples of the famous Blériot XI from the original Blériot factory — to a massive 20-cylinder engine of 200 hp (150 kW), with its cylinders arranged in four rows of five cylinders apiece. Most radial engines are air-cooled , but one of the most successful of the early radial engines (and the earliest "stationary" design produced for World War I combat aircraft)

1044-653: A force was established, it was met with controversy and heavy criticism from officers who were sceptical that Poland required any bomber aircraft at all. Despite this unpromising lack of interest, a separate service, known as the Wojska Lotnicze ( Polish Air Force ), had been formed during 1918. During the Polish–Soviet War of 1919, there had been proposals mooted for the formation of a specialised bomber group equipped with modified Breguet 14 B2 biplanes ; however, these were not quickly followed up upon due to

1160-527: A fraction of their maximum bomb load (typically 800 kg or 8 x 100 kg bombs), which limited their effectiveness. During the invasion of Poland , from 4 September onward the planes of the Bomber Brigade were attacking German armoured columns in day attacks, forced by the desperate situation to perform this mission for which they were not designed (the original plans to bomb targets inside Germany were quickly abandoned). Most notably, they hampered

1276-526: A geared supercharger . Further developments of the Pegasus created the fuel-injected Bristol Draco and the diesel Bristol Phoenix , both types being produced in limited numbers. In contrast, by the end of production over 30,000 Pegasus engines had been built. Aircraft applications ranged from single-engine biplanes to the four-engined Short Sandringham and Sunderland flying boats . Several altitude and distance records were set by aircraft using

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1392-457: A lack of understanding and appreciation amongst senior officers. During April 1920, the first Polish bomber squadron was stood up at Poznań–Ławica Airport , Greater Poland , equipped with a variety of captured ex-German aircraft such as Gotha G.IVs , AEG G.IVs , and Friedrichshafen G.IIIs . However, following the end of the conflict with the Soviets , this bomber squadron was amalgamated with

1508-419: A loss of coolant and consequent engine overheating, while an air-cooled radial engine may be largely unaffected by minor damage. Radials have shorter and stiffer crankshafts, a single-bank radial engine needing only two crankshaft bearings as opposed to the seven required for a liquid-cooled, six-cylinder, inline engine of similar stiffness. While a single-bank radial permits all cylinders to be cooled equally,

1624-439: A metal-covered airframe. The late A series (designated Abis) and B series aircraft received a double vertical stabilizer which improved flight stability and increased the field of fire of the dorsal gunner. The aircraft was quite small for its bomb load and range; its carrying capacity was achieved in part by a lift-generating, airfoil-shaped fuselage, which was an innovative feature (previously used e.g. on PZL.26 sports plane). It

1740-462: A name upon the bomber, Łoś . Production of the Łoś commenced during the winter of 1936-1937. During 1938, the first 10 serial aircraft were manufactured, designated as PZL.37A; these were furnished with a single vertical stabilizer. The next 19 interim aircraft were constructed to the PZL.37A bis standard, having been outfitted with the newer twin tail configuration. All of these aircraft were powered by

1856-670: A number of captured planes underwent testing by both Nazi Germany and the Soviet Union. Relatively few PZL.37s fell into German hands, probably only two aircraft; this is partially due to the efforts of Polish factory workers who scrapped roughly 30 PZL.37s that remained in factories in Okęcie and Mielec, under the pretext of cleaning up the area, during October 1939, before the German authorities were able to reconnoiter. There are no surviving PZL.37 aircraft. An original PZL Pegaz 20 engine of

1972-677: A number of experiments and modifications) enough cooling air to the rear. This basic concept was soon copied by many other manufacturers, and many late-WWII aircraft returned to the radial design as newer and much larger designs began to be introduced. Examples include the Bristol Centaurus in the Hawker Sea Fury , and the Shvetsov ASh-82 in the Lavochkin La-7 . For even greater power, adding further rows

2088-606: A pair of 300 kg bombs in one of the fuselage bomb bays, it could not carry bombs larger than 110 kg. When flown at the maximum loadout, the majority of the weight of the bombs was carried inside the wings. There were no provisions for mounting bombs on the outside of the aircraft. During the invasion of Poland in 1939, 110 kg was the maximum weight used, since the 300 kg bombs were available only in small quantities, and were difficult to load at improvised airfields with little infrastructure. 50 kg bombs were also used. Maximal bomb load taken from soft surface runways

2204-535: A piston engine can be calculated by multiplying the charge per cylinder by the number of cycles per second; the Mercury improved both and thereby produced more power for a given size. The primary advantage was a much improved power-to-weight ratio due to better volumetric efficiency . The Pegasus was the same size, displacement and general steel/aluminium construction as the Jupiter, but various improvements allowed

2320-510: A power-to-weight ratio near that of contemporary gasoline engines and a specific fuel consumption of roughly 80% that for an equivalent gasoline engine. During WWII the research continued, but no mass-production occurred because of the Nazi occupation. By 1943 the engine had grown to produce over 1,000 hp (750 kW) with a turbocharger . After the war, the Clerget company was integrated in

2436-704: A reconnaissance-orientated squadron. During 1920, the Polish Air Force heavily benefited from an extensive re-armament and expansion programme headed by General Włodzimierz Zagórski , under which the formation of dedicated bomber regiments was envisioned. Accordingly, an order was placed for 32 French-built Farman F.68 BN.4 Goliath twin-engined night bombers , with which it was intended to equip and launch these squadrons. An additional pair of army co-operation squadrons were repurposed as light bomber units instead, equipped with French Potez XV B2 aircraft. Unfortunately, Zagórski's reforms were abandoned following

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2552-888: A reserve base in Małaszewicze and in a factory in Warsaw – Okęcie ). Twenty-six or twenty-seven Polish Air Force PZL.37s (17 from the Bomber Brigade and ten training ones) were withdrawn in 1939 to Romania . During October 1940, these aircraft were seized by the Romanian government and 23 of these aircraft would be used by the Romanian Air Force in the 4th Group, consisting of the 76th and 77th bomber escadres. Some were uparmed with four machine guns (the Polish PWU machineguns were still used). About one third were lost in crashes due to lack of experience of Romanian pilots with

2668-704: A similarly sized five-cylinder radial four-stroke model engine of their own as a direct rival to the OS design, with Saito also creating a series of three-cylinder methanol and gasoline-fueled model radial engines ranging from 0.90 cu.in. (15 cm ) to 4.50 cu.in. (75 cm ) in displacement, also all now available in spark-ignition format up to 84 cm displacement for use with gasoline. The German Seidel firm formerly made both seven- and nine-cylinder "large" (starting at 35 cm displacement) radio control model radial engines, mostly for glow plug ignition, with an experimental fourteen-cylinder twin-row radial being tried out -

2784-478: A single bank (or row) and an unusual double master connecting rod. Variants were built that could be run on either diesel oil or gasoline or mixtures of both. A number of powerhouse installations utilising large numbers of these engines were made in the U.S. Electro-Motive Diesel (EMD) built the "pancake" engines 16-184 and 16-338 for marine use. Zoche aero-diesels are a prototype radial design that have an even number of cylinders, either four or eight; but this

2900-420: A total of 8 compact bomb bays located in the central section of the wings (which had space for a maximum of 16 bombs). This arrangement of bomb bays imposed considerable restrictions on the types of bombs that could be carried, especially in the wing bays which were quite small due to the need to fit between the ribs of the wing. The maximum load was 2,580 kg (2 × 300 kg and 18 × 110 kg). Apart from

3016-599: Is also used by builders of homebuilt aircraft , such as the Culp Special , and Culp Sopwith Pup , Pitts S12 "Monster" and the Murphy "Moose" . 110 hp (82 kW) 7-cylinder and 150 hp (110 kW) 9-cylinder engines are available from Australia's Rotec Aerosport . HCI Aviation offers the R180 5-cylinder (75 hp (56 kW)) and R220 7-cylinder (110 hp (82 kW)), available "ready to fly" and as

3132-645: Is closed while moving from Kemble Airport to Filton. There is also an engine on display at the Brooklands Museum at Weybridge. As of October 2010 two Bristol Pegasus engines remain airworthy in England. They power the two Fairey Swordfish aircraft operated by the Royal Navy Historic Flight . Data from Lumsden. Related development Comparable engines Related lists Radial engine The radial configuration

3248-412: Is not problematic, because they are two-stroke engines , with twice the number of power strokes as a four-stroke engine per crankshaft rotation. A number of radial motors operating on compressed air have been designed, mostly for use in model airplanes and in gas compressors. A number of multi-cylinder 4-stroke model engines have been commercially available in a radial configuration, beginning with

3364-627: The Kawasaki Ki-100 and Yokosuka D4Y 3. In Britain, Bristol produced both sleeve valved and conventional poppet valved radials: of the sleeve valved designs, more than 57,400 Hercules engines powered the Vickers Wellington , Short Stirling , Handley Page Halifax , and some versions of the Avro Lancaster , over 8,000 of the pioneering sleeve-valved Bristol Perseus were used in various types, and more than 2,500 of

3480-646: The May Coup led by Józef Piłsudski . Throughout the 1920s and 1930s, some officials within Poland remained interested in the establishment of a national bomber force, in some cases for prestige value rather than in terms of strict military value. During 1927, the Department of Aeronautics authorised the development of the Lublin R-VIII , a large single-engined reconnaissance bomber. In the following year,

3596-466: The PZL P.11 ). Upon its introduction to service, it was popularly considered to be not only the most modern and effective weapon then possessed by Poland, but also to be one of the most advanced bombers then operational in the world. From mid-1938 onwards, interest was expressed by various nations in potential export sales of the PZL.37; in response to this highly favourable reception, PZL, being keen to meet

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3712-435: The PZL.3 . The bomber was to be powered by an arrangement of four Bristol Jupiter radial engines positioned in tandem pairs and armed with a pair of side-mounted gun turrets in addition to an internally-stowed bombload of 3,000 kg (6,613 lb). However, during December 1930, all work on this concept was abandoned as an economy measure and the construction of a prototype was abandoned. Reportedly, technical data for

3828-736: The Pegas . Approximately 32,000 Pegasus engines were built. The Pegasus set three height records in the Bristol Type 138 : in 1932, 1936 and 1937. It was used for the first flight over Mount Everest in the Westland Wallace , and in 1938 set the world's long-distance record in Vickers Wellesleys . In service the Pegasus was generally reliable with the exception that the valves were prone to failure. The valves were operated by rocker-boxes, which were lubricated by oil pads on

3944-595: The Pegasus XVIII ) and 100-octane fuel. This gave rise to the claim "one pound per horsepower" reflecting the excellent power-to-weight ratio. Some notable users of the Pegasus were the Fairey Swordfish , Vickers Wellington , and Short Sunderland . It was also used on the Anbo 41 , Bristol Bombay , Saro London , Short Empire , Vickers Wellesley and the Westland Wallace . Like the Jupiter before it,

4060-544: The Polish Armed Forces would be of questionable value. Instead, it was decided to develop the nation's aviation assets to principally function as a means of providing aerial support to the newly formed Polish Land Forces . As such, a relatively minimal budget was allocated for aviation matters while no dedicated doctrine in respect to air power was developed, neither was an effective bomber force pursued in any form throughout much of this period and, when such

4176-532: The Rutan Voyager . The experimental Bristol Phoenix of 1928–1932 was successfully flight tested in a Westland Wapiti and set altitude records in 1934 that lasted until World War II. In 1932 the French company Clerget developed the 14D, a 14-cylinder two-stroke diesel radial engine. After a series of improvements, in 1938 the 14F2 model produced 520 hp (390 kW) at 1910 rpm cruise power, with

4292-638: The SNECMA company and had plans for a 32-cylinder diesel engine of 4,000 hp (3,000 kW), but in 1947 the company abandoned piston engine development in favour of the emerging turbine engines. The Nordberg Manufacturing Company of the United States developed and produced a series of large two-stroke radial diesel engines from the late 1940s for electrical production, primarily at aluminum smelters and for pumping water. They differed from most radials in that they had an even number of cylinders in

4408-499: The Westland Lysander , Bristol Blenheim , and Blackburn Skua . In the years leading up to World War II, as the need for armored vehicles was realized, designers were faced with the problem of how to power the vehicles, and turned to using aircraft engines, among them radial types. The radial aircraft engines provided greater power-to-weight ratios and were more reliable than conventional inline vehicle engines available at

4524-470: The rudder seizing (due to being aero-dynamically overbalanced) and consequent total loss of control. Following the implementation of some structural changes, the PZL.37B became a highly reliable aircraft. By the outbreak of the Second World War , roughly 92 PZL.37 bombers had been produced and delivered to the Polish Air Force, and a further 31 were in different phases of production. Prior to

4640-670: The American Pratt & Whitney company was founded, competing with Wright's radial engines. Pratt & Whitney's initial offering, the R-1340 Wasp , was test run later that year, beginning a line of engines over the next 25 years that included the 14-cylinder, twin-row Pratt & Whitney R-1830 Twin Wasp . More Twin Wasps were produced than any other aviation piston engine in the history of aviation; nearly 175,000 were built. In

4756-633: The American Evolution firm now sells the Seidel-designed radials, with their manufacturing being done in India. PZL.37 %C5%81o%C5%9B The PZL.37 Łoś ('moose') was a Polish twin-engined medium bomber designed and manufactured by national aircraft company Państwowe Zakłady Lotnicze (PZL). It is sometimes incorrectly referred to as "PZL P.37", but the letter "P" was reserved for fighters of Zygmunt Puławski 's design (such as

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4872-607: The American single-engine Vought F4U Corsair , Grumman F6F Hellcat , Republic P-47 Thunderbolt , twin-engine Martin B-26 Marauder , Douglas A-26 Invader , Northrop P-61 Black Widow , etc. The same firm's aforementioned smaller-displacement (at 30 litres), Twin Wasp 14-cylinder twin-row radial was used as the main engine design for the B-24 Liberator , PBY Catalina , and Douglas C-47 , each design being among

4988-673: The British-developed Bristol Pegasus XII B radial engine , which was produced in Poland under licence . The main production variant, the PZL.37B (or: Łoś II), was furnished with the twin tail arrangement along with newer Pegasus XX engines. During autumn 1938, production of the PZL.37B commenced for the Polish Air Force . During the initial period of service, 2 prototypes and 6 serial aircraft were lost in separate crashes; these had been caused by several technical problems, most of which involved

5104-635: The Centaurus and rapid movement to the use of turboprops such as the Armstrong Siddeley Python and Bristol Proteus , which easily produced more power than radials without the weight or complexity. Large radials continued to be built for other uses, although they are no longer common. An example is the 5-ton Zvezda M503 diesel engine with 42 cylinders in 6 rows of 7, displacing 143.6 litres (8,760 cu in) and producing 3,942 hp (2,940 kW). Three of these were used on

5220-692: The German single-seat, single-engine Focke-Wulf Fw 190 Würger , and twin-engine Junkers Ju 88 . In Japan, most airplanes were powered by air-cooled radial engines like the 14-cylinder Mitsubishi Zuisei (11,903 units, e.g. Kawasaki Ki-45 ), Mitsubishi Kinsei (12,228 units, e.g. Aichi D3A ), Mitsubishi Kasei (16,486 units, e.g. Kawanishi H8K ), Nakajima Sakae (30,233 units, e.g. Mitsubishi A6M and Nakajima Ki-43 ), and 18-cylinder Nakajima Homare (9,089 units, e.g. Nakajima Ki-84 ). The Kawasaki Ki-61 and Yokosuka D4Y were rare examples of Japanese liquid-cooled inline engine aircraft at that time but later, they were also redesigned to fit radial engines as

5336-617: The Gnome and Le Rhône rotary powerplants, and Siemens-Halske built their own designs, including the Siemens-Halske Sh.III eleven-cylinder rotary engine , which was unusual for the period in being geared through a bevel geartrain in the rear end of the crankcase without the crankshaft being firmly mounted to the aircraft's airframe, so that the engine's internal working components (fully internal crankshaft "floating" in its crankcase bearings, with its conrods and pistons) were spun in

5452-513: The Japanese O.S. Max firm's FR5-300 five-cylinder, 3.0 cu.in. (50 cm ) displacement "Sirius" radial in 1986. The American "Technopower" firm had made smaller-displacement five- and seven-cylinder model radial engines as early as 1976, but the OS firm's engine was the first mass-produced radial engine design in aeromodelling history. The rival Saito Seisakusho firm in Japan has since produced

5568-478: The Jupiter. Although other piston configurations and turboprops have taken over in modern propeller-driven aircraft , Rare Bear , which is a Grumman F8F Bearcat equipped with a Wright R-3350 Duplex-Cyclone radial engine, is still the fastest piston-powered aircraft . 125,334 of the American twin-row, 18-cylinder Pratt & Whitney R-2800 Double Wasp , with a displacement of 2,800 in (46 L) and between 2,000 and 2,400 hp (1,500-1,800 kW), powered

5684-402: The PZL.3 was later received by French manufacturer Potez . During the 1930s, discussions were held regarding a potential replacement of Poland's Fokker F.VIIs. Numerous concepts were explored by the Department of Aeronautics, the most impressive submission was deemed to have been made by Polish aeronautical engineer Jerzy Dąbrowski , who had produced the initial proposals that would lead to

5800-500: The PZL.37 during spring 1934 and submitted to the department in July 1934. The concept was of a very quick monoplane bomber manned by a crew of four, featuring all-metal stressed-skin construction and powered by a pair of radial engines capable of producing 800-1,200 hp. The airframe was aerodynamically clean and was to be capable of very high performance, far in advance of contemporary bombers; wind tunnel testing using scale models of

5916-578: The PZL.37 met with a huge interest. For export purposes, new variants were developed: the PZL.37C with Gnome-Rhone 14N -0/1 radial engines of 985 cv (971 BHP, 724 kW), maximum speed 445 km/h and the PZL.37D with 14N-20/21 of 1,065 cv (1,050 BHP, 783 kW), maximum speed 460 km/h. In 1939, 20 PZL.37Cs were ordered by Yugoslavia , 12 by Bulgaria , 30 PZL.37Ds and license by Romania and 10, raw materials and parts for next 25 and license by Turkey and, finally, 12 aircraft for Greece . The Belgian company Constructions Aéronautiques G. Renard

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6032-521: The PZL.37's handling and its high wing loading, and due to engine faults. About 15 were used in combat against the Soviet Union from 22 June 1941. Among others, they first operated in Bessarabia , while they were later used to conduct bombing missions targeting Kiev and Odessa . Some of the bombers were lost on these missions, mostly due to anti-aircraft fire. Because of a lack of spare parts,

6148-521: The PZL.37s of the Bomber Brigade actively participated in the defence of Poland. By 1 September, they had been deployed to rural improvised airfields, so they were not destroyed on the ground by the Germans in their initial attack on the main Polish airbases. However, because of this move away from developed airfields to short fields with poor surfaces, during the campaign the planes could take off with only

6264-509: The PZL.37s that had been evacuated from Poland were seized by the Romanian government and 23 of these aircraft were subsequently used by the Royal Romanian Air Force in the invasion of the Soviet Union . Throughout the majority of the interwar period , the dominant military philosophies and practices within the leadership of Poland was that aircraft were of a secondary importance and a separate air-oriented service within

6380-515: The Pegasus was also licensed by the PZL company in Poland . It was used on the PZL.23 Karaś and PZL.37 Łoś bombers. In Italy Alfa Romeo Avio built both the Jupiter (126-RC35) and the Pegasus under licence, with the engine based on the Pegasus designated as the Alfa Romeo 126-RC34 with the civil version as the 126-RC10. In Czechoslovakia it was built by Walter Engines and was known as

6496-693: The Pegasus. The Bristol Siddeley company reused the name many years later for the turbofan engine used in the Hawker Siddeley Harrier and which became known as the Rolls-Royce Pegasus when Rolls-Royce took over that company. Two Bristol Pegasus engines remain airworthy in 2010, powering Fairey Swordfish aircraft operated by the Royal Navy Historic Flight (became Navy Wings in March 2019); other examples are preserved and on public display in aviation museums . The Pegasus

6612-399: The Polish Air Force had roughly 86 PZL.37s in total, but less than a half of those actually saw active combat use due to aircraft being used by training units, being in maintenance, or having been held in reserve. The bombers suffered from a high attrition rate due to lack of fighter protection, and the final Polish combat missions were performed on 19 September. In October 1940, around 26-27 of

6728-491: The Polish Air Force had roughly 86 PZL.37s in total, but less than a half of those were used in combat. 36 PZL.37Bs were in four bomber escadres of a Bomber Brigade: the 11th, 12th, 16th and 17th escadres (two escadres with nine aircraft each, constituted a group, in Polish : dywizjon ; the PZL.37 were in groups X and XV). The remainder of the Bomber Brigade's aircraft were PZL.23 Karaś . About 50 remaining PZL.37s were assigned to

6844-595: The Second World War, the PZL.37B Łoś was widely considered to be one of the most advanced bombers then operational in the world. It was able to carry a heavier bombload than considerably larger aircraft, such as the British-built Vickers Wellington , though over shorter range and the dimensions of the individual bombs were limited. Being smaller than most contemporary medium bombers, the Łoś was relatively fast and easy to handle. As

6960-619: The United Kingdom the Bristol Aeroplane Company was concentrating on developing radials such as the Jupiter, Mercury , and sleeve valve Hercules radials. Germany, Japan, and the Soviet Union started with building licensed versions of the Armstrong Siddeley, Bristol, Wright, or Pratt & Whitney radials before producing their own improved versions. France continued its development of various rotary engines but also produced engines derived from Bristol designs, especially

7076-400: The advance of the XVI Army Corps near Częstochowa and Radomsko . During these engagements, the PZL.37 suffered heavy losses as a result of a lack of adequate fighter protection, which was further amplified by the operational tactics employed, usually flying missions in units of no more than three aircraft at a time. The last combat flights took place on 16 September. During the campaign,

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7192-467: The aircraft were extremely encouraging. During October 1934, the instruction to proceed with the proposal, initially designated P.37 , was received by PZL. An express priority was placed upon performance over armament and equipment, relying upon its high speed for its defence; as such, only a single 7.7 mm machine gun was allocated to each turret position instead of the twin-guns and 20 mm dorsal cannon previously considered. On 14 April 1935,

7308-446: The animated illustration, four cam lobes serve all 10 valves across the five cylinders, whereas 10 would be required for a typical inline engine with the same number of cylinders and valves. Most radial engines use overhead poppet valves driven by pushrods and lifters on a cam plate which is concentric with the crankshaft, with a few smaller radials, like the Kinner B-5 and Russian Shvetsov M-11 , using individual camshafts within

7424-486: The bomber role, the first of which being delivered during 1929, despite condemnation of the aircraft's poor defensive armament, limited payload capacity, and excessive weight. Despite not being approved for further development, PZL decided to independently continue refining their designs for a multi-engined night bomber. These studies, led by aircraft engineer Wladyslaw Zalewski , developed an advanced concept for an all-metal low-wing cantilever monoplane bomber known as

7540-427: The combat units were reinforced with several other aircraft, and about 46 PZL.37s were used in combat. Of the Bomber Brigade aircraft, ten PZL.37s were shot down by fighters, five shot down by enemy anti-aircraft artillery , two bombed on the ground and a further ten lost in other ways. A number of not fully completed, training or reserve PZL.37s were also destroyed on airfields and in factories (18 PZL.37s were bombed in

7656-460: The compression stroke, this liquid, being incompressible, stops piston movement. Starting or attempting to start the engine in such condition may result in a bent or broken connecting rod. Originally radial engines had one row of cylinders, but as engine sizes increased it became necessary to add extra rows. The first radial-configuration engine known to use a twin-row design was the 160 hp Gnôme "Double Lambda" rotary engine of 1912, designed as

7772-502: The crankcase and cylinders revolved with the propeller. It was similar in concept to the later radial, the main difference being that the propeller was bolted to the engine, and the crankshaft to the airframe. The problem of the cooling of the cylinders, a major factor with the early "stationary" radials, was alleviated by the engine generating its own cooling airflow. In World War I many French and other Allied aircraft flew with Gnome , Le Rhône , Clerget , and Bentley rotary engines,

7888-572: The crankcase for each cylinder. A few engines use sleeve valves such as the 14-cylinder Bristol Hercules and the 18-cylinder Bristol Centaurus , which are quieter and smoother running but require much tighter manufacturing tolerances . C. M. Manly constructed a water-cooled five-cylinder radial engine in 1901, a conversion of one of Stephen Balzer 's rotary engines , for Langley 's Aerodrome aircraft. Manly's engine produced 52 hp (39 kW) at 950 rpm. In 1903–1904 Jacob Ellehammer used his experience constructing motorcycles to build

8004-408: The crankshaft takes two revolutions to complete the four strokes of each piston (intake, compression, combustion, exhaust). The camshaft ring is geared to spin slower and in the opposite direction to the crankshaft. Its cam lobes are placed in two rows; one for the intake valves and one for the exhaust valves. The radial engine normally uses fewer cam lobes than other types. For example, in the engine in

8120-435: The demands, developed additional variants that were intended for the export market, such as the PZL.37C (which was to be powered by a pair of Gnome-Rhone 14N -0/1 radial engines ). An improved enlarged derivative, known as the PZL.49 Miś , was also developed for the Polish Air Force. The Łoś was extensively used in the defense of Poland during the invasion of Poland by Nazi Germany in September 1939. On 1 September 1939,

8236-481: The department issued its approval of a full-scale wooden mock-up of the aircraft, authorising the construction of a pair of prototypes along with a structural test frame. During early 1936, the necessity of revising the design's structure delayed the construction of the partially-assembled first prototype. During May 1936, the prototype commenced ground testing and taxiing trials; however, on 15 June, while being rolled out for its intended first flight, an engine failure

8352-408: The department ordered Polish aviation manufacturer Państwowe Zakłady Lotnicze (PZL) to make preparations towards the development of a heavy multi-engined night bomber; while numerous proposals and design studies were made by both PZL and private factories, but none were approved for further development by the department. Instead, it was decided to procure a number of Dutch-built Fokker F.VII to meet

8468-486: The early 1920s Le Rhône converted a number of their rotary engines into stationary radial engines. By 1918 the potential advantages of air-cooled radials over the water-cooled inline engine and air-cooled rotary engine that had powered World War I aircraft were appreciated but were unrealized. British designers had produced the ABC Dragonfly radial in 1917, but were unable to resolve the cooling problems, and it

8584-461: The engine nacelles. The undercarriage was double-wheeled, complete with independent suspension for each wheel. The bomber was powered by a pair of Bristol Pegasus radial engines; the PZL.37A model had Pegasus XII B engines (normal power: 860 BHP (873 cv, 642 kW), maximum: 940 BHP (953 cv, 701 kW)), the PZL.37B variant had Pegasus XX engines (normal power: 905 HP (918 cv, 675 kW), maximum: 970 BHP (984 cv, 723 kW)). Originally, it

8700-566: The fast Osa class missile boats . Another one was the Lycoming XR-7755 which was the largest piston aircraft engine ever built in the United States with 36 cylinders totaling about 7,750 in (127 L) of displacement and a power output of 5,000 horsepower (3,700 kilowatts). While most radial engines have been produced for gasoline, there have been diesel radial engines. Two major advantages favour diesel engines — lower fuel consumption and reduced fire risk. Packard designed and built

8816-630: The four-engine Boeing B-29 Superfortress and others. The Soviet Shvetsov OKB-19 design bureau was the sole source of design for all of the Soviet government factory-produced radial engines used in its World War II aircraft, starting with the Shvetsov M-25 (itself based on the American Wright Cyclone 9 's design) and going on to design the 41-litre displacement Shvetsov ASh-82 fourteen cylinder radial for fighters, and

8932-441: The initial PZL.37A version possessed a maximal speed 10 per cent higher than the originally planned 360 km/h. The modified profile was viewed as highly successful and was later re-used for other projects (sometimes in further modified form; e.g. PZL.46 Sum , PZL.49 Miś , PZL.50 Jastrząb ). The bomber's offensive payload was spread across a two-section bomb bay set within the fuselage (providing space for up to 4 bombs) and

9048-408: The instrumentation panel, overheating of the cylinder heads, and criticism of the cockpit's lack of space, however, test pilots were typically highly impressed with the aircraft. In response to the feedback from the first prototype's testing, several improvements and other modifications were made, some of which were introduced on the original prototype while more extensive changes were introduced upon

9164-620: The largest-displacement production British radial from the Bristol firm to use sleeve valving, the Bristol Centaurus were used to power the Hawker Tempest II and Sea Fury . The same firm's poppet-valved radials included: around 32,000 of Bristol Pegasus used in the Short Sunderland , Handley Page Hampden , and Fairey Swordfish and over 20,000 examples of the firm's 1925-origin nine-cylinder Mercury were used to power

9280-447: The late-war Hawker Sea Fury and Grumman F8F Bearcat , two of the fastest production piston-engined aircraft ever built, using radial engines. Whenever a radial engine remains shut down for more than a few minutes, oil or fuel may drain into the combustion chambers of the lower cylinders or accumulate in the lower intake pipes, ready to be drawn into the cylinders when the engine starts. As the piston approaches top dead center (TDC) of

9396-665: The majority used a geared supercharger, either single-speed or two-speed. Variant differences included compression ratios , propeller reduction gear ratios and accessories. Note: Bristol Pegasus engines can be viewed installed in aircraft at the Royal Air Force Museum London and the Imperial War Museum Duxford . An unrestored Pegasus recovered from the sea bed is in the care of the Bristol Aero Collection, which

9512-487: The massive, 58-litre displacement Shvetsov ASh-73 eighteen-cylinder radial in 1946 - the smallest-displacement radial design from the Shvetsov OKB during the war was the indigenously designed, 8.6 litre displacement Shvetsov M-11 five cylinder radial. Over 28,000 of the German 42-litre displacement, 14-cylinder, two-row BMW 801 , with between 1,560 and 2,000 PS (1,540-1,970 hp, or 1,150-1,470 kW), powered

9628-436: The maximum engine speed to be increased from 1,950 to 2,600 rpm for take-off power. This improved performance considerably from the Jupiter's 580 hp (430 kW), to the first Pegasus II with 635 hp (474 kW), to 690 hp (510 kW) in the first production model Pegasus III , and eventually to the late-model Pegasus XXII with 1,010 hp (750 kW) thanks to the two-speed supercharger (introduced on

9744-548: The opposing direction to the crankcase and cylinders, which still rotated as the propeller itself did since it was still firmly fastened to the crankcase's frontside, as with regular umlaufmotor German rotaries. By the end of the war the rotary engine had reached the limits of the design, particularly in regard to the amount of fuel and air that could be drawn into the cylinders through the hollow crankshaft, while advances in both metallurgy and cylinder cooling finally allowed stationary radial engines to supersede rotary engines. In

9860-595: The production leaders in all-time production numbers for each type of airframe design. The American Wright Cyclone series twin-row radials powered American warplanes: the nearly-43 litre displacement, 14-cylinder Twin Cyclone powered the single-engine Grumman TBF Avenger , twin-engine North American B-25 Mitchell , and some versions of the Douglas A-20 Havoc , with the massive twin-row, nearly 55-litre displacement, 18-cylinder Duplex-Cyclone powering

9976-409: The rear bank of cylinders, but a variety of baffles and fins were introduced that largely eliminated these problems. The downside was a relatively large frontal area that had to be left open to provide enough airflow, which increased drag. This led to significant arguments in the industry in the late 1930s about the possibility of using radials for high-speed aircraft like modern fighters. The solution

10092-532: The remaining planes were withdrawn from the front in October 1941; after this, the type was mainly used for training. During April 1944, the 76th escadrille returned to combat, with nine aircraft, but it was withdrawn from the front on 3 May 1944. After Romania joined the Allies, on 1 September 1944, German aircraft destroyed five PZL.37s on the ground during retaliatory attacks against Romanian targets. Additionally,

10208-432: The reserve XX group, training units or in repairs. As a consequence of there only having been a few months available to train the crews and complete the equipping of the bombers, the planes were not fully ready when the war broke out. For example, the extra internal fuel tanks for the type were not yet in service, thus the maximum range of the bomber that had been quoted in specifications was in practice not achievable. Only

10324-465: The same is not true for multi-row engines where the rear cylinders can be affected by the heat coming off the front row, and air flow being masked. A potential disadvantage of radial engines is that having the cylinders exposed to the airflow increases drag considerably. The answer was the addition of specially designed cowlings with baffles to force the air between the cylinders. The first effective drag-reducing cowling that didn't impair engine cooling

10440-479: The second prototype designated as PZL.37/II. This second prototype featured the adoption of twin-vertical stabilizers, a re-worked cockpit and an altered ventral gun position amongst other changes, functioned as a representative aircraft of the anticipated production bomber and performed its first flight during autumn 1936. Suitably impressed, the department accepted the aircraft for production, placing an initial order for 10 pre-production aircraft, as well as bestowing

10556-600: The time. This reliance had a downside though: if the engines were mounted vertically, as in the M3 Lee and M4 Sherman , their comparatively large diameter gave the tank a higher silhouette than designs using inline engines. The Continental R-670 , a 7-cylinder radial aero engine which first flew in 1931, became a widely used tank powerplant, being installed in the M1 Combat Car , M2 Light Tank , M3 Stuart , M3 Lee , and LVT-2 Water Buffalo . The Guiberson T-1020 ,

10672-476: The top of the cylinder heads. In hot climates the lubrication deteriorated which could lead to seizing of the valves. Also if a problem developed with the engine and the pilot shut it down it was not possible to "feather" the propeller and so it would continue to rotate creating drag and continue to turn the engine which had no lubrication being forced through it by the oil pump. The Pegasus was produced in many variants, early prototype engines were unsupercharged but

10788-553: The type used in PZL.37 Łoś is in the collection of the Polish Aviation Museum in Kraków . This engine was sent from Poland to the United States in the spring of 1939 to be exhibited at the 1939 New York World's Fair and thus survived the war, and was returned to Poland in 2006. A 1:1 scale non-flying model of PZL.37 Łoś was assembled at PZL Mielec factory, in the factory hall used to construct these bombers before

10904-456: The type. The Polish military were not allowed to establish an arrangement with Iran due to "lack of production abilities". Nevertheless, the outbreak of the war acted to prevent the production of any of these aircraft. At that time, PZL developed the next variant for the Polish Air Force, the PZL.49 Miś , but this was not completed before the war. Possessing slightly bigger dimensions, the Miś ("Bear")

11020-492: The ultimate examples of which reached 250 hp (190 kW) although none of those over 160 hp (120 kW) were successful. By 1917 rotary engine development was lagging behind new inline and V-type engines, which by 1918 were producing as much as 400 hp (300 kW), and were powering almost all of the new French and British combat aircraft. Most German aircraft of the time used water-cooled inline 6-cylinder engines. Motorenfabrik Oberursel made licensed copies of

11136-402: The uppermost one in the animation, has a master rod with a direct attachment to the crankshaft. The remaining pistons pin their connecting rods ' attachments to rings around the edge of the master rod. Extra "rows" of radial cylinders can be added in order to increase the capacity of the engine without adding to its diameter. Four-stroke radials have an odd number of cylinders per row, so that

11252-456: The war. The dimensions of the model were determined only from photographs as very little of the original blueprints for the aircraft survive; nevertheless, the model's external shape matches the original very closely. It was constructed from aluminium and steel leftovers from aircraft under construction at the factory and was presented to the public in September 2012. The interior of the plane

11368-623: The world's first air-cooled radial engine, a three-cylinder engine which he used as the basis for a more powerful five-cylinder model in 1907. This was installed in his triplane and made a number of short free-flight hops. Another early radial engine was the three-cylinder Anzani , originally built as a W3 "fan" configuration, one of which powered Louis Blériot 's Blériot XI across the English Channel . Before 1914, Alessandro Anzani had developed radial engines ranging from 3 cylinders (spaced 120° apart) — early enough to have been used on

11484-410: The world), but this is disputed – its shape which resembled laminar flow wings developed in later years, but this was largely fortuitous, and at any rate achieving the laminar flow regime would have required additional construction features (most importantly extremely smooth wings shaped with extreme precision) which the aircraft simply lacked. However, the profile did display lower drag than expected and

11600-512: Was carried out in the US, and demonstrated that ample airflow was available with careful design. This led to the R-4360 , which has 28 cylinders arranged in a 4 row corncob configuration. The R-4360 saw service on large American aircraft in the post- World War II period. The US and Soviet Union continued experiments with larger radials, but the UK abandoned such designs in favour of newer versions of

11716-420: Was commonly used for aircraft engines before gas turbine engines became predominant. Since the axes of the cylinders are coplanar, the connecting rods cannot all be directly attached to the crankshaft unless mechanically complex forked connecting rods are used, none of which have been successful. Instead, the pistons are connected to the crankshaft with a master-and-articulating-rod assembly. One piston,

11832-473: Was designed by Sir Roy Fedden as the follow-on to the Bristol Aeroplane Company 's very successful Bristol Jupiter , using lessons learned in development of the Mercury . Although having a capacity (25 L) almost 15% smaller, the Mercury produced about as much power as the Jupiter, through a combination of supercharging to improve the "charge", and various changes to increase the operating RPM . The power of

11948-683: Was developed in 1922 with Navy funding, and using aluminum cylinders with steel liners ran for an unprecedented 300 hours, at a time when 50 hours endurance was normal. At the urging of the Army and Navy the Wright Aeronautical Corporation bought Lawrance's company, and subsequent engines were built under the Wright name. The radial engines gave confidence to Navy pilots performing long-range overwater flights. Wright's 225 hp (168 kW) J-5 Whirlwind radial engine of 1925

12064-597: Was granted permission to perform the license production of between 20–50 aircraft for the Second Spanish Republic ; however, the venture was abandoneded due to the victory of the opposing Nationalists in the Spanish Civil War . In addition to the Belgian venture, it is known that Denmark , Estonia , Finland and Iran were all at various stages of negotiation for their own acquisitions of

12180-402: Was intended for a popular wing profile, designed by Ryszard Bartel (also used in many other successful Polish airframes incl. PZL P.11 ) to be used for the aircraft; however, the requirement of providing bomb storage with the internal space of the wings necessitated modification to the design. Some publications claim the resulting profile displayed laminar-flow properties (one of the first in

12296-453: Was introduced with the BMW 801 14-cylinder twin-row radial. Kurt Tank designed a new cooling system for this engine that used a high-speed fan to blow compressed air into channels that carry air to the middle of the banks, where a series of baffles directed the air over all of the cylinders. This allowed the cowling to be tightly fitted around the engine, reducing drag, while still providing (after

12412-483: Was not considered viable due to the difficulty of providing the required airflow to the rear banks. Larger engines were designed, mostly using water cooling although this greatly increased complexity and eliminated some of the advantages of the radial air-cooled design. One example of this concept is the BMW 803 , which never entered service. A major study into the airflow around radials using wind tunnels and other systems

12528-471: Was not reproduced, except the bombardier's position in the nose. Currently the model is exhibited outdoors on the grounds of the Mielec factory.( 50°18′36″N 21°27′40″E  /  50.31000°N 21.46111°E  / 50.31000; 21.46111 ) A number of crash sites of PZL.37 Łoś shot down in September, 1939 have been identified and aircraft parts have been recovered from them. One crash site has

12644-746: Was not until the 1920s that Bristol and Armstrong Siddeley produced reliable air-cooled radials such as the Bristol Jupiter and the Armstrong Siddeley Jaguar . In the United States the National Advisory Committee for Aeronautics (NACA) noted in 1920 that air-cooled radials could offer an increase in power-to-weight ratio and reliability; by 1921 the U.S. Navy had announced it would only order aircraft fitted with air-cooled radials and other naval air arms followed suit. Charles Lawrance 's J-1 engine

12760-620: Was reduced to about 800–1200 kg. During early 1938, the Polish Air Force started to receive the Łos A variant; it was followed by deliveries of the improved PZL.37B to operational units, which had been slowed by delays in supply of the Pegasus XX engines and other equipment, during the autumn of 1938. It was planned that by April 1939, the air force should have 128 aircraft but less than half had been accepted into service and half of those were early production not up to standard and issued to conversion training units. On 1 September 1939,

12876-548: Was shorter and had smaller wings than its German and French counterparts but carried comparable bomb load and defensive armament. The crew consisted of four: pilot, commander-bombardier, radio operator and a dorsal gunner. The bombardier was accommodated in the glazed nose, with a forward-firing machine gun. The radio operator sat inside the fuselage, above the bomb bay , and he also operated the ventral machine gun during combat. The Łoś featured retractable main undercarriage , which retracted into purpose-built alcoves located within

12992-454: Was sustained prior to the attempt, resulting in its delay. On 30 June 1936, the first PZL.37/I prototype, which was fitted with a single vertical stabilizer, performed its maiden flight successfully. In August 1936, the initial factory tests were completed, after which the first prototype participated in official airworthiness and service trials. These revealed a handful of shortcomings, including rear fuselage flutter , excessive vibration on

13108-545: Was the Salmson 9Z series of nine-cylinder water-cooled radial engines that were produced in large numbers. Georges Canton and Pierre Unné patented the original engine design in 1909, offering it to the Salmson company; the engine was often known as the Canton-Unné. From 1909 to 1919 the radial engine was overshadowed by its close relative, the rotary engine , which differed from the so-called "stationary" radial in that

13224-709: Was the British Townend ring or "drag ring" which formed a narrow band around the engine covering the cylinder heads, reducing drag. The National Advisory Committee for Aeronautics studied the problem, developing the NACA cowling which further reduced drag and improved cooling. Nearly all aircraft radial engines since have used NACA-type cowlings. While inline liquid-cooled engines continued to be common in new designs until late in World War II , radial engines dominated afterwards until overtaken by jet engines, with

13340-409: Was to be fitted with Bristol Hercules II radial engines of 1,350 bhp (1,370 cv, 1,007 kW), capable of a maximum speed of 520 km/h along with the addition of an upper turret. The PZL.37 Łoś was a twin-engined all-metal monoplane medium bomber . The first production variant PZL.37A was relatively conventional in layout, being outfitted with low-set wings, a single vertical stabilizer, and

13456-474: Was widely claimed as "the first truly reliable aircraft engine". Wright employed Giuseppe Mario Bellanca to design an aircraft to showcase it, and the result was the Wright-Bellanca WB-1 , which first flew later that year. The J-5 was used on many advanced aircraft of the day, including Charles Lindbergh 's Spirit of St. Louis , in which he made the first solo trans-Atlantic flight. In 1925

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