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61-503: Few details are available on its formation, but it is reported to have been established by Viyacheslav Eshba , originally operating several Yak-52 trainer aircraft armed with machine guns. Its first combat mission was conducted on 27 August 1992, which has come to be celebrated in Abkhazia as "Aviation Day." The Abkhaz Air Force claims to have made 400 operational flights during the 1992-1993 Abkhaz-Georgian war . Abkhaz combat losses during

122-469: A ZALA drone on 8 June 2024. Images posted on social media suggest that at least one Yak-52 has downed up to eight drones. The Yak-52's low stall speed allows the plane to pursue drones and carry out maneuvers at slower speeds, enabling a machine gunner in the plane's rear seat to engage drones at close range. While the Yak-52 was never intended to serve as an air-to-air combat platform, improvisation during

183-618: A Yak-52 has reportedly attained 6 kills against Orlan 10/30 series drones and 2 against Zala 421-16E drones. Two more kills are attributed to lightning striking one UAV in front of the Ukrainian pilots, and another to a drone encountering a birdstrike . Data from Jane's All The World's Aircraft 1993-94 General characteristics Performance Related development Propeller (aircraft) In aeronautics , an aircraft propeller , also called an airscrew , converts rotary motion from an engine or other power source into

244-460: A bent aluminium sheet for blades, thus creating an airfoil shape. They were heavily undercambered , and this plus the absence of lengthwise twist made them less efficient than the Wright propellers. Even so, this was perhaps the first use of aluminium in the construction of an airscrew. Originally, a rotating airfoil behind the aircraft, which pushes it, was called a propeller, while one which pulled from

305-468: A childhood fascination with the Chinese flying top, developed a model of feathers, similar to that of Launoy and Bienvenu, but powered by rubber bands. By the end of the century, he had progressed to using sheets of tin for rotor blades and springs for power. His writings on his experiments and models would become influential on future aviation pioneers. William Bland sent designs for his "Atmotic Airship" to

366-457: A craft that weighed 3.5 long tons (3.6 t), with a 110 ft (34 m) wingspan that was powered by two 360 hp (270 kW) steam engines driving two propellers. In 1894, his machine was tested with overhead rails to prevent it from rising. The test showed that it had enough lift to take off. One of Pénaud's toys, given as a gift by their father , inspired the Wright brothers to pursue

427-416: A fixed-pitch prop once airborne. The spring-loaded "two-speed" VP prop is set to fine for takeoff, and then triggered to coarse once in cruise, the propeller remaining coarse for the remainder of the flight. After World War I , automatic propellers were developed to maintain an optimum angle of attack. This was done by balancing the centripetal twisting moment on the blades and a set of counterweights against

488-467: A large number of blades. A fan therefore produces a lot of thrust for a given diameter but the closeness of the blades means that each strongly affects the flow around the others. If the flow is supersonic, this interference can be beneficial if the flow can be compressed through a series of shock waves rather than one. By placing the fan within a shaped duct , specific flow patterns can be created depending on flight speed and engine performance. As air enters

549-528: A low- drag wing and as such are poor in operation when at other than their optimum angle of attack . Therefore, most propellers use a variable pitch mechanism to alter the blades' pitch angle as engine speed and aircraft velocity are changed. A further consideration is the number and the shape of the blades used. Increasing the aspect ratio of the blades reduces drag but the amount of thrust produced depends on blade area, so using high-aspect blades can result in an excessive propeller diameter. A further balance

610-402: A military trainer, the development of the aircraft incorporates a number of features to be found on the early postwar fighters: notably the cockpit tandem layout (instrument panel, seat design, cockpit opening system), tail design, tricycle landing gear, fuselage mixed construction (monocoque with steel tube construction), inner flaps, controls position, access panels on sides of the fuselage, even

671-415: A propeller efficiency of about 73.5% at cruise for a Cessna 172 . This is derived from his "Bootstrap approach" for analyzing the performance of light general aviation aircraft using fixed pitch or constant speed propellers. The efficiency of the propeller is influenced by the angle of attack (α). This is defined as α = Φ - θ, where θ is the helix angle (the angle between the resultant relative velocity and

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732-453: A propeller suffers when transonic flow first appears on the tips of the blades. As the relative air speed at any section of a propeller is a vector sum of the aircraft speed and the tangential speed due to rotation, the flow over the blade tip will reach transonic speed well before the aircraft does. When the airflow over the tip of the blade reaches its critical speed , drag and torque resistance increase rapidly and shock waves form creating

793-450: A sharp increase in noise. Aircraft with conventional propellers, therefore, do not usually fly faster than Mach 0.6. There have been propeller aircraft which attained up to the Mach 0.8 range, but the low propeller efficiency at this speed makes such applications rare. The tip of a propeller blade travels faster than the hub. Therefore, it is necessary for the blade to be twisted so as to decrease

854-571: A small coaxial modeled after the Chinese top but powered by a wound-up spring device and demonstrated it to the Russian Academy of Sciences . It was powered by a spring, and was suggested as a method to lift meteorological instruments. In 1783, Christian de Launoy , and his mechanic , Bienvenu, used a coaxial version of the Chinese top in a model consisting of contrarotating turkey flight feathers as rotor blades, and in 1784, demonstrated it to

915-417: A spring and the aerodynamic forces on the blade. Automatic props had the advantage of being simple, lightweight, and requiring no external control, but a particular propeller's performance was difficult to match with that of the aircraft's power plant. The most common variable pitch propeller is the constant-speed propeller . This is controlled by a hydraulic constant speed unit (CSU). It automatically adjusts

976-698: A swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached several radial airfoil -section blades such that the whole assembly rotates about a longitudinal axis. The blade pitch may be fixed, manually variable to a few set positions, or of the automatically variable "constant-speed" type. The propeller attaches to the power source's driveshaft either directly or through reduction gearing . Propellers can be made from wood, metal or composite materials . Propellers are most suitable for use at subsonic airspeeds generally below about 480 mph (770 km/h), although supersonic speeds were achieved in

1037-531: Is a Soviet primary trainer aircraft which first flew in 1976. It was produced in Romania from 1977 to 1998 by Aerostar , as Iak-52 , which gained manufacturing rights under agreement within the former COMECON socialist trade organisation. The Yak-52 was designed as an aerobatic trainer for students in the Soviet DOSAAF training organisation, which trained civilian sport pilots and military pilots. Currently

1098-447: Is between 10 and 50 bars (145 and 725 psi) and an emergency circuit is reserved for lowering the undercarriage if the normal supply is exhausted or the compressor fails. Additionally both main and reserve bottles can be charged from a port on the ground with compressed air, usually from a scuba type air bottle. The ground steering/braking arrangement, especially, takes some adjustment for flyers accustomed to hydraulics , because

1159-680: Is difficult to accurately provide due to a number of factors including Abkhazia's disputed status, a lack of official available information, multiple conflicts over the course of its existence, and the regular involvement of Russian aircraft and pilots in the conflicts and region. In general, the air force has relied on aircraft inherited from the former Soviet forces based in Abkhazia with possible reinforcement in recent years by Russia with second-hand aircraft. No traditional contracts for aircraft purchases by Abkhazia have been reported. Several different markings have been reported. Yakovlev Yak-52 The Yakovlev Yak-52 ( Russian : Яковлев Як-52 )

1220-451: Is hydraulic, with engine oil serving as the hydraulic fluid. However, electrically controlled propellers were developed during World War II and saw extensive use on military aircraft, and have recently seen a revival in use on home-built aircraft. Another design is the V-Prop , which is self-powering and self-governing. On most variable-pitch propellers, the blades can be rotated parallel to

1281-472: Is suitable for airliners, but the noise generated is tremendous (see the Antonov An-70 and Tupolev Tu-95 for examples of such a design). Forces acting on the blades of an aircraft propeller include the following. Some of these forces can be arranged to counteract each other, reducing the overall mechanical stresses imposed. The purpose of varying pitch angle is to maintain an optimal angle of attack for

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1342-409: Is that using a smaller number of blades reduces interference effects between the blades, but to have sufficient blade area to transmit the available power within a set diameter means a compromise is needed. Increasing the number of blades also decreases the amount of work each blade is required to perform, limiting the local Mach number – a significant performance limit on propellers. The performance of

1403-489: Is used to help slow the aircraft after landing and is particularly advantageous when landing on a wet runway as wheel braking suffers reduced effectiveness. In some cases reverse pitch allows the aircraft to taxi in reverse – this is particularly useful for getting floatplanes out of confined docks. Counter-rotating propellers are sometimes used on twin-engine and multi-engine aircraft with wing-mounted engines. These propellers turn in opposite directions from their counterpart on

1464-538: The French Academy of Sciences . A dirigible airship was described by Jean Baptiste Marie Meusnier presented in 1783. The drawings depict a 260-foot-long (79 m) streamlined envelope with internal ballonets that could be used for regulating lift. The airship was designed to be driven by three propellers. In 1784 Jean-Pierre Blanchard fitted a hand-powered propeller to a balloon, the first recorded means of propulsion carried aloft. Sir George Cayley , influenced by

1525-563: The McDonnell XF-88B experimental propeller-equipped aircraft. Supersonic tip-speeds are used in some aircraft like the Tupolev Tu-95 , which can reach 575 mph (925 km/h). The earliest references for vertical flight came from China. Since around 400 BC, Chinese children have played with bamboo flying toys . This bamboo-copter is spun by rolling a stick attached to a rotor between one's hands. The spinning creates lift, and

1586-459: The Russo-Ukrainian war has led to the platform attaining kills against UAVs . On April 27, 2024, over Odesa, Ukraine , footage emerged from the perspective of a Russian drone showing a Yak-52 being flown by Ukrainian pilots with the canopy open. The first crew member, the pilot, flew circles around the drone as the second crew member attacked the drone with a shotgun . Through this method,

1647-403: The Tupolev Tu-95 propel it at a speed exceeding the maximum once considered possible for a propeller-driven aircraft using an exceptionally coarse pitch. Early pitch control settings were pilot operated, either with a small number of preset positions or continuously variable. The simplest mechanism is the ground-adjustable propeller , which may be adjusted on the ground, but is effectively

1708-523: The Great Exhibition held in London in 1851, where a model was displayed. This was an elongated balloon with a steam engine driving twin propellers suspended underneath. Alphonse Pénaud developed coaxial rotor model helicopter toys in 1870, also powered by rubber bands. In 1872 Dupuy de Lome launched a large navigable balloon, which was driven by a large propeller turned by eight men. Hiram Maxim built

1769-655: The M14PF engine designated & three blade propeller, an electric start, and modern instruments. On April 16, 2004, a modernised variant Yak-52M was flown in Russia. It is fitted with modernised M-14Kh engine, three-blade propeller, and other modifications. Despite being unarmed, a Yak-52 was used by Ukraine during the Russian invasion of Ukraine to shoot down a Russian Orlan-10 reconnaissance drone over Odessa in April 2024, and to shoot down

1830-503: The Yak-52 are now produced. The replacement of the existing Soviet avionics , fitting of a three-blade propeller and the M14PF 298 kW (400 hp) upgrade to the usual 360 hp M14P engine, and conversion to conventional "tail-dragger" landing gear (Yak-52TD) are some of the modifications made to the standard aircraft. There is also a factory-produced Yak-52TW tail-dragger version by Aerostar. The TW has an extra 120 L (32 US gal) of fuel capacity in two extra wing tanks,

1891-540: The Yak-52 is responsive and very capable as an aerobatic aircraft. Yet it is also easy to fly and land. It has been used in international aerobatic competition up to the Advanced level. It is stressed to +7 and –5 Gs, rolls (to the right) at well more than 180 degrees/second (measured up to 352 degrees/second to the right), and is capable of every manoeuvre in the Aresti catalog . The Yak-52, like most Soviet military aircraft,

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1952-491: The Yak-52 is used in the Fédération Aéronautique Internationale (FAI) World Aerobatic Yak 52 Competition, a popular powered aircraft one-design World Aerobatic Championship. A descendant of the single-seat competition aerobatic Yakovlev Yak-50 , the all-metal Yak-52 is powered by a 268 kW (360 hp) Vedeneyev M14P nine-cylinder radial engine . Since the aircraft was designed to serve as

2013-399: The air in the propeller slipstream. Contra-rotation also increases the ability of a propeller to absorb power from a given engine, without increasing propeller diameter. However the added cost, complexity, weight and noise of the system rarely make it worthwhile and it is only used on high-performance types where ultimate performance is more important than efficiency. A fan is a propeller with

2074-428: The aircraft maintain speed and altitude with the operative engines. Feathering also prevents windmilling , the turning of engine components by the propeller rotation forced by the slipstream; windmilling can damage the engine, start a fire, or cause structural damage to the aircraft. Most feathering systems for reciprocating engines sense a drop in oil pressure and move the blades toward the feather position, and require

2135-400: The aircraft uses differential braking controlled by rudder pedals and a hand-operated lever on the control stick. The tricycle landing gear is retractable, but it remains partially exposed in the retracted position, affording both a useful level of drag in down manoeuvres and a measure of protection should the aircraft be forced to land "wheels up." A number of "westernised" versions of

2196-405: The airflow to stop rotation of the propeller and reduce drag when the engine fails or is deliberately shut down. This is called feathering , a term borrowed from rowing . On single-engined aircraft, whether a powered glider or turbine-powered aircraft, the effect is to increase the gliding distance. On a multi-engine aircraft, feathering the propeller on an inoperative engine reduces drag, and helps

2257-410: The angle of attack of the blade gradually and therefore produce uniform lift from the hub to the tip. The greatest angle of incidence, or the highest pitch, is at the hub while the smallest angle of incidence or smallest pitch is at the tip. A propeller blade designed with the same angle of incidence throughout its entire length would be inefficient because as airspeed increases in flight, the portion near

2318-407: The blade pitch in order to maintain a constant engine speed for any given power control setting. Constant-speed propellers allow the pilot to set a rotational speed according to the need for maximum engine power or maximum efficiency, and a propeller governor acts as a closed-loop controller to vary propeller pitch angle as required to maintain the selected engine speed. In most aircraft this system

2379-440: The blade rotation direction) and Φ is the blade pitch angle. Very small pitch and helix angles give a good performance against resistance but provide little thrust, while larger angles have the opposite effect. The best helix angle is when the blade is acting as a wing producing much more lift than drag. However, 'lift-and-drag' is only one way to express the aerodynamic force on the blades. To explain aircraft and engine performance

2440-403: The blade tips approach the speed of sound. The maximum relative velocity is kept as low as possible by careful control of pitch to allow the blades to have large helix angles. A large number of blades are used to reduce work per blade and so circulation strength. Contra-rotating propellers are used. The propellers designed are more efficient than turbo-fans and their cruising speed (Mach 0.7–0.85)

2501-599: The civil war are uncertain, but include a Yak-52 on a reconnaissance mission near Sukhumi on 4 July 1993. In the autumn of 2001, Abkhazia's air force was reported to comprise 250 personnel, 1 Su-25 , 2 L-39 , 1 Yak-52 , and 2 Mi-8 . The display of three L-39s at a parade in 2004 suggests a possible recent acquisition. In February 2007 a Russian website reported that Abkhazia has 2 Su-27 fighters, 1 Yak-52 , 2 Su-25 attack aircraft, 2 L-39 combat trainers, 1 An-2 light transport, 7 Mi-8 helicopters and 3 Mi-24 helicopters. However, an undated 2007 Abkhaz source gave

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2562-460: The dream of flight. The twisted airfoil (aerofoil) shape of an aircraft propeller was pioneered by the Wright brothers. While some earlier engineers had attempted to model air propellers on marine propellers , the Wright Brothers realized that a propeller is essentially the same as a wing , and were able to use data from their earlier wind tunnel experiments on wings, introducing a twist along

2623-575: The duct, its speed is reduced while its pressure and temperature increase. If the aircraft is at a high subsonic speed this creates two advantages: the air enters the fan at a lower Mach speed; and the higher temperature increases the local speed of sound. While there is a loss in efficiency as the fan is drawing on a smaller area of the free stream and so using less air, this is balanced by the ducted fan retaining efficiency at higher speeds where conventional propeller efficiency would be poor. A ducted fan or propeller also has certain benefits at lower speeds but

2684-431: The feathering process or the feathering process may be automatic. Accidental feathering is dangerous and can result in an aerodynamic stall ; as seen for example with Yeti Airlines Flight 691 which crashed during approach due to accidental feathering. The propellers on some aircraft can operate with a negative blade pitch angle, and thus reverse the thrust from the propeller. This is known as Beta Pitch. Reverse thrust

2745-463: The front was a tractor . Later the term 'pusher' became adopted for the rear-mounted device in contrast to the tractor configuration and both became referred to as 'propellers' or 'airscrews'. The understanding of low speed propeller aerodynamics was fairly complete by the 1920s, but later requirements to handle more power in a smaller diameter have made the problem more complex. Propeller research for National Advisory Committee for Aeronautics (NACA)

2806-557: The fuselage – clockwise on the left engine and counterclockwise on the right – however, there are exceptions (especially during World War II ) such as the P-38 Lightning which turned "outwards" (counterclockwise on the left engine and clockwise on the right) away from the fuselage from the WW II years, and the Airbus A400 whose inboard and outboard engines turn in opposite directions even on

2867-414: The hub would have a negative AOA while the blade tip would be stalled. There have been efforts to develop propellers and propfans for aircraft at high subsonic speeds. The 'fix' is similar to that of transonic wing design. Thin blade sections are used and the blades are swept back in a scimitar shape ( scimitar propeller ) in a manner similar to wing sweepback, so as to delay the onset of shockwaves as

2928-483: The inventory for the Abkhazian Air Force as 16 MiG-21 , 46 Su-25 , 2 L-39 , 1 Yak-52 , and 2 Mi-8 . In March 2008, a military aviation enthusiast website repeated this inventory but added 9 Mi-24/35 attack helicopters. In 2021, President Aslan Bzhania announced intentions to modernize the air force. An accounting of exact types, quantities, and service dates for aircraft serving in the Abkhazian Air Force

2989-400: The length of the blades. This was necessary to maintain a more uniform angle of attack of the blade along its length. Their original propeller blades had an efficiency of about 82%, compared to 90% for a modern (2010) small general aviation propeller, the 3-blade McCauley used on a Beechcraft Bonanza aircraft. Roper quotes 90% for a propeller for a human-powered aircraft. Mahogany was

3050-488: The location of the radio antenna and overall dimensions of the airplane, which extensively match the Yakovlev Yak-17 UTI jet fighter trainer (NATO code name Magnet). The aircraft has fuel and oil systems permitting inverted flight for as long as two minutes. The engine drives a two-bladed counter-clockwise rotating, variable pitch, wood and fiberglass laminate propeller . At 998 kg (2,200 lb) empty weight,

3111-432: The other wing to balance out the torque and p-factor effects. They are sometimes referred to as "handed" propellers since there are left hand and right hand versions of each prop. Generally, the propellers on both engines of most conventional twin-engined aircraft spin clockwise (as viewed from the rear of the aircraft). To eliminate the critical engine problem, counter-rotating propellers usually turn "inwards" towards

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3172-417: The pilot to pull the propeller control back to disengage the high-pitch stop pins before the engine reaches idle RPM . Turboprop control systems usually use a negative torque sensor in the reduction gearbox, which moves the blades toward feather when the engine is no longer providing power to the propeller. Depending on design, the pilot may have to push a button to override the high-pitch stops and complete

3233-553: The propeller blades, giving maximum efficiency throughout the flight regime. This reduces fuel usage. Only by maximising propeller efficiency at high speeds can the highest possible speed be achieved. Effective angle of attack decreases as airspeed increases, so a coarser pitch is required at high airspeeds. The requirement for pitch variation is shown by the propeller performance during the Schneider Trophy competition in 1931. The Fairey Aviation Company fixed-pitch propeller used

3294-411: The same force is expressed slightly differently in terms of thrust and torque since the required output of the propeller is thrust. Thrust and torque are the basis of the definition for the efficiency of the propeller as shown below. The advance ratio of a propeller is similar to the angle of attack of a wing. A propeller's efficiency is determined by Propellers are similar in aerofoil section to

3355-410: The same wing. A contra-rotating propeller or contra-prop places two counter-rotating propellers on concentric drive shafts so that one sits immediately 'downstream' of the other propeller. This provides the benefits of counter-rotating propellers for a single powerplant. The forward propeller provides the majority of the thrust, while the rear propeller also recovers energy lost in the swirling motion of

3416-524: The toy flies when released. The 4th-century AD Daoist book Baopuzi by Ge Hong (抱朴子 "Master who Embraces Simplicity") reportedly describes some of the ideas inherent to rotary wing aircraft. Designs similar to the Chinese helicopter toy appeared in Renaissance paintings and other works. It was not until the early 1480s, when Leonardo da Vinci created a design for a machine that could be described as an "aerial screw" , that any recorded advancement

3477-445: The wood preferred for propellers through World War I , but wartime shortages encouraged use of walnut , oak , cherry and ash . Alberto Santos Dumont was another early pioneer, having designed propellers before the Wright Brothers for his airships . He applied the knowledge he gained from experiences with airships to make a propeller with a steel shaft and aluminium blades for his 14 bis biplane in 1906. Some of his designs used

3538-442: Was designed to operate in rugged environments with minimal maintenance. One of its key features, unusual in western aircraft, is its extensive pneumatic system. Engine starting, landing gear , flaps , and wheel brakes are all pneumatically actuated. Spherical storage bottles for air, replenished by an engine driven compressor, are situated behind the rear cockpit and contents displayed on the instrument panels. The operating pressure

3599-600: Was directed by William F. Durand from 1916. Parameters measured included propeller efficiency, thrust developed, and power absorbed. While a propeller may be tested in a wind tunnel , its performance in free-flight might differ. At the Langley Memorial Aeronautical Laboratory , E. P. Leslie used Vought VE-7s with Wright E-4 engines for data on free-flight, while Durand used reduced size, with similar shape, for wind tunnel data. Their results were published in 1926 as NACA report #220. Lowry quotes

3660-506: Was made towards vertical flight. His notes suggested that he built small flying models, but there were no indications for any provision to stop the rotor from making the craft rotate. As scientific knowledge increased and became more accepted, man continued to pursue the idea of vertical flight. Many of these later models and machines would more closely resemble the ancient bamboo flying top with spinning wings, rather than Leonardo's screw. In July 1754, Russian Mikhail Lomonosov had developed

3721-447: Was partially stalled on take-off and up to 160 mph (260 km/h) on its way up to a top speed of 407.5 mph (655.8 km/h). The very wide speed range was achieved because some of the usual requirements for aircraft performance did not apply. There was no compromise on top-speed efficiency, the take-off distance was not restricted to available runway length and there was no climb requirement. The variable pitch blades used on

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