The Allison T56

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

engine has been developed extensively throughout its production run, the many variants are described by the manufacturer as belonging to four main series groups. Initial civil variants (Series I) were designed and produced by the

Allison Engine Company The Allison Engine Company was an American aircraft engine manufacturer. Shortly after the death of James A. Allison, James Allison in 1929 the company was purchased by the Fisher Body, Fisher brothers. Fisher sold the company to General Motors, ...

as the 501-D and powered the

Lockheed C-130 Hercules The Lockheed C-130 Hercules is an American four-engine turboprop military transport aircraft designed and built by Lockheed (now Lockheed Martin). Capable of using unprepared runways for takeoffs and landings, the C-130 was originally design ...

. Later variants (Series II, III, 3,5 and IV) gave increased performance through design refinements. Further derivatives of the 501-D/T56 were produced as

turboshaft A turboshaft engine is a form of gas turbine that is optimized to produce shaftpower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the exhaust ...

s for

helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...

s including a variant with a

United States military aircraft engine designation The United States military aircraft engine designation system was introduced in 1926, originally for piston engines it was expanded in the 1947 to include a separate system for jet and rocket engines. Piston engines A piston engine designation has ...

of T701, which was developed for the canceled

Boeing Vertol XCH-62 The Boeing Vertol XCH-62 (Model 301) was a triple-turbine, heavy-lift helicopter project designed for the United States Army by Boeing Vertol. Approved in 1971, one prototype reached 95% completion before it was canceled in 1975. The prototype wa ...

project.

Commercial variants (501-D)

;501-D10: The initial civil variant, which was proposed in 1955 with of power at a

brake specific fuel consumption Brake-specific fuel consumption (BSFC) is a measure of the fuel efficiency of any prime mover that burns fuel and produces rotational, or shaft power. It is typically used for comparing the efficiency of internal combustion engines with a shaft out ...

(BSFC) of , a two-stage gearbox with a reduction ratio of 12.5:1, a 14-stage

axial flow An axial compressor is a gas compressor that can continuously pressurize gases. It is a rotating, airfoil-based compressor in which the gas or working fluid principally flows parallel to the axis of rotation, or axially. This differs from othe ...

compressor with a compression ratio over 9:1, a four-stage turbine, and a , three-blade Aeroproducts A6341FN-215 propeller. ;501-D13: (Series I) Commercial version of the T56-A-1 used on the

Lockheed L-188 Electra The Lockheed L-188 Electra is an American turboprop airliner built by Lockheed. First flown in 1957, it was the first large turboprop airliner built in the United States. Initial sales were good, but after two fatal crashes that led to expensiv ...

, but using

kerosene Kerosene, paraffin, or lamp oil is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from el, κηρός (''keros'') meaning "wax", and was regi ...

as the primary fuel and JP4 as the alternate (instead of JP4 as primary and

gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...

as secondary), and with the gearbox reduction ratio increased to 13.54 from 12.5, which lowers the propeller blade tip speed by 8 percent to for the Aeroproducts 606 propeller; power rating at sea level takeoff, 14-stage axial compressor, 6 cannular combustion chambers, and 4-stage turbine; 13,820 rpm shaft and turbine inlet temperature; certified on September 12, 1957. ;501-D13A: (Series I) Similar to the 501-D13 but using a

Hamilton Standard Hamilton Standard was an American aircraft propeller parts supplier. It was formed in 1929 when United Aircraft and Transport Corporation consolidated Hamilton Aero Manufacturing and Standard Steel Propeller into the Hamilton Standard Propeller C ...

propeller; certified on April 15, 1958. ;501-D13D: (Series I) Similar to the 501-D13 except for the location of the rear mount and using D.C. generator drive; certified on December 18, 1959; used on the

Convair CV-580 Convair, previously Consolidated Vultee, was an American aircraft manufacturing company that later expanded into rockets and spacecraft. The company was formed in 1943 by the merger of Consolidated Aircraft and Vultee Aircraft. In 1953, it ...

passenger aircraft. ;501-D13E: (Series I) Similar to the 501-D13 except for the location of the rear mount; certified on December 18, 1959. ;501-D13H: (Series I) Similar to the 501-D13D but with water-methanol injection; certified on February 20, 1964; used on the USAF's General Dynamics NC-131H Samaritan. and the

. ;501-D15: A engine under development for the Lockheed Electra. ;501-D22: (Series II) Similar to the 501-D13A but with power rating at sea level takeoff, a shroud turbine, gearbox offset up, and no auto-feathering; certified on October 28, 1964. Used on the

Lockheed L-100 Hercules The Lockheed L-100 Hercules is the civilian variant of the prolific C-130 Hercules military transport aircraft made by the Lockheed Corporation. Its first flight occurred in 1964. Longer L-100-20 and L-100-30 versions were developed. L-100 pro ...

. ;501-D22A: (Series III); Similar to the 501-D22 but with power rating at sea level takeoff and air-cooled first-stage turbine blades, vanes, and stalk blades in all four turbine stages; certified on January 23, 1968. ;501-D22C: (Series III) Similar to the 501-D22A but with gearbox offset down, integral mount pads, and water-methanol injection; certified on December 27, 1968; powered the

Aero Spacelines Super Guppy The Aero Spacelines Super Guppy is a large, wide-bodied cargo aircraft that is used for hauling outsize cargo components. It was the successor to the Pregnant Guppy, the first of the Guppy aircraft produced by Aero Spacelines. Five were built i ...

. ;501-D22D: A derivative to power the proposed Lockheed L-400, a twin-engine version of the L-100. ;501-D22E: Offered in 1979 as the initial engine for Lockheed's proposed L-100-60 (a stretched derivative of the

Lockheed L-100 The Lockheed L-100 Hercules is the civilian variant of the prolific C-130 Hercules military transport aircraft made by the Lockheed Corporation. Its first flight occurred in 1964. Longer L-100-20 and L-100-30 versions were developed. L-100 pro ...

). ;501-D22G: (Series III) Similar to the 501-D22C but with power rating at sea level takeoff, a three-mount system, auto-feathering, and no water-methanol injection; certified on March 23, 1984. Used on the

;501-D36: (Series II) Re-engined powerplant for the

Royal Canadian Air Force The Royal Canadian Air Force (RCAF; french: Aviation royale canadienne, ARC) is the air and space force of Canada. Its role is to "provide the Canadian Forces with relevant, responsive and effective airpower". The RCAF is one of three environm ...

(RCAF)

CC-109 Cosmopolitan The Canadair CL-66 was a turboprop version of the civilian Convair CV-440 Metropolitan. The CC-109 Cosmopolitan or "Cosmo" in RCAF service became the standard VIP aircraft as well as replacing the Douglas Dakota and the North American B-25 Mitc ...

in 1966. ;501-D39: (Series IV) Offered for the

civil aircraft, starting in 1979 for the proposed L-100-60 as the successor engine to the 501-D22E, producing with propellers; was the commercial version of the 501-M71. ;501-H2: Engine for the proposed Vanguard Model 30

lift fan Lift fan is an aircraft configuration in which lifting fans are located in large holes in an otherwise conventional fixed wing or fuselage. It is used for V/STOL operation. The aircraft takes off using the fans to provide lift, then transitions ...

aircraft that was entered in a 1961

vertical takeoff and landing A vertical take-off and landing (VTOL) aircraft is one that can take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust-vectoring fixed-win ...

(VTOL) transport competition; powered two fans within the wings and two propellers; used a modified compressor for handling larger air flows. ;501-M1: Modified engine with new turbine blades that were hollow and air-cooled; on an experimental engine combining features of the 501-M1 with the 501-H2, ran at for nearly 2.5 hours at a turbine inlet temperature of in January 1962 under a program funded by the Air Force and Navy. ;501-M7B: Replaces the T56-A-7 on an experimental

short takeoff and landing A short takeoff and landing (STOL) aircraft is a conventional fixed-wing aircraft that has short runway requirements for takeoff and landing. Many STOL-designed aircraft also feature various arrangements for use on airstrips with harsh condition ...

(STOL) version of the Lockheed C-130E (internally designated as the GL298-7) targeted in 1963 for the

U.S. Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cl ...

; power increased by 20% over the T56-A-7 due to lowering of the gear reduction ratio from 13.54 to 12.49, propeller blade changes to take advantage of the higher resulting propeller rotational speed, and a new turbine with air-cooled first and second-stage vanes and first-stage blades, so the turbine inlet temperature can be increased from for the T56-A-7 to ; a rate engine that is restricted to and about of static thrust on the STOL C-130E, but is capable of thrust at full power and with a larger, propeller. ;501-M22: Internal designation for the T56-A-18; submitted for FAA certification under a new type certificate. ;501-M23: Submitted for FAA certification under an amended type certificate. ;501-M24: A demonstrator engine started in 1964 that was later used to derive the 501-M62B engine developed for the XCH-62 helicopter. ;501-M25: A four-stage fixed turbine engine similar to the T56-A-15, but with a increase from the T56-A-15's maximum turbine inlet temperature rating of , and a variable geometry compressor for the inlet vane and the first five

stator The stator is the stationary part of a rotary system, found in electric generators, electric motors, sirens, mud motors or biological rotors. Energy flows through a stator to or from the rotating component of the system. In an electric mot ...

vanes; investigated in 1965 to power helicopters with a

maximum takeoff weight The maximum takeoff weight (MTOW) or maximum gross takeoff weight (MGTOW) or maximum takeoff mass (MTOM) of an aircraft is the maximum weight at which the pilot is allowed to attempt to take off, due to structural or other limits. The analogous ...

(MTOW). ;501-M26: A similar to the 501-M25 but with a free turbine instead of a fixed turbine, and a two-stage gas producer turbine; based on the T56-A-18 engine. ;501-M34: A turboshaft engine targeted for a 60-70 seat commuter helicopter proposal from Lockheed-California in 1966. ;501-M56: Engine candidate for the turboprop version of the Air Force

A-X The Fairchild Republic A-10 Thunderbolt II is a single-seat, twin-turbofan, straight-wing, subsonic attack aircraft developed by Fairchild Republic for the United States Air Force (USAF). In service since 1976, it is named for the Republ ...

close air support In military tactics, close air support (CAS) is defined as air action such as air strikes by fixed or rotary-winged aircraft against hostile targets near friendly forces and require detailed integration of each air mission with fire and moveme ...

aircraft, requiring of engine power. ;501-M62B: An internal designation for the engine that became the T701-AD-700 turboshaft, which weighed and was intended to power the

heavy-lift helicopter; 15 engines built, 700 hours of component testing, and almost 2,500 hours of engine development testing completed before the helicopter project's cancellation. ;501-M69: Engine proposed for transport-type offensive anti-air (TOAA) aircraft versions of the P-3 Orion (stretched derivative) and C-130 Hercules; rated power of , equivalent installed

thrust-specific fuel consumption Thrust-specific fuel consumption (TSFC) is the fuel efficiency of an engine design with respect to thrust output. TSFC may also be thought of as fuel consumption (grams/second) per unit of thrust (newtons, or N), hence ''thrust-specific''. This fi ...

at cruise of . ;501-M71: A derivative of the T56-A-14 evaluated by NAVAIR in 1982 to achieve 10% lower fuel consumption, 24% more horsepower, smokeless exhaust, and greater reliability. ;501-M71K: (Series IV) A engine using a larger propeller to power the

-20 (L382E-44K-20) High Technology Test Bed (HTTB) for

(STOL) starting in 1989, but was destroyed when the HTTB became airborne during a ground test on February 3, 1993. ;501-M78: A demonstrator engine for

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

's Propfan Test Assessment (PTA) program. It had a modified

reduction gearbox An epicyclic gear train (also known as a planetary gearset) consists of two gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers of the two gears and rotates the planet and sun gea ...

that reversed the direction of rotation and increased the output speed from 1,020 rpm to 1,698 rpm. The engine was attached to an eight-bladed, , single-rotation Hamilton Standard SR-7L propeller. Shown as an engine at the 1983

Dayton Air Show The CenterPoint Energy Dayton Air Show is an annual event held at the Dayton International Airport in Vandalia, Ohio, eight miles north of Dayton, Ohio. From 2013 to 2019, the show has been held on a weekend in late June. Prior to 2013, and again ...

, the 501-M78 was flight-tested on a

Gulfstream II The Gulfstream II (G-II) is an American twin engine business jet designed and built by Grumman and then in succession, Grumman American and finally Gulfstream American. Its Grumman model number is G-1159 and its US military designation is C-11A. ...

aircraft beginning in May 1987. Various flight and ground testing programs were carried out on the engine testbed through June 1989. ;501-M80C: Also known as the

T406-AD-400 The Rolls-Royce T406 (company designation AE 1107) is a turboshaft engine that powers the Bell Boeing V-22 Osprey tiltrotor. The engine delivers 6,000 shp (4,470 kW). Development In 1982, Allison Engine Company, Detroit Diesel Allison ( ...

, a turboshaft engine. primarily based on the T56-A-427, but with a

free-turbine turboshaft A free-turbine turboshaft is a form of turboshaft or turboprop gas turbine engine where the power is extracted from the exhaust stream of a gas turbine by an independent turbine, downstream of the gas turbine. The power turbine is not mechanically ...

added to the single-spool engine; used on the

V-22 Osprey The Bell Boeing V-22 Osprey is an American multi-mission, tiltrotor military aircraft with both vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) capabilities. It is designed to combine the functionality of a convention ...

tiltrotor assault transport. ;PW–Allison 501-M80E: A

contra-rotating Contra-rotating, also referred to as coaxial contra-rotating, is a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque. Examples include some aircraft propellers, res ...

geared

propfan A propfan, also called an open rotor engine, or unducted fan (as opposed to a ducted fan), is a type of aircraft engine related in concept to both the turboprop and turbofan, but distinct from both. The design is intended to offer the speed an ...

engine derived from the 501-M80C/

T406 The Rolls-Royce T406 (company designation AE 1107) is a turboshaft engine that powers the Bell Boeing V-22 Osprey tiltrotor. The engine delivers 6,000 shp (4,470 kW). Development In 1982, Detroit Diesel Allison (DDA) prepared a new eng ...

turboshaft engine and intended for use on a 92-seat version of the proposed

MPC 75 MPC 75 was an aircraft project of the company "MPC Aircraft GmbH" a subsidiary of "Deutsche Airbus". Work on the project was done mainly between 1988 and 1992 in Hamburg, Germany. Predevelopment work was finished, however the project never got ...

regional aircraft; developed jointly with

Pratt & Whitney Pratt & Whitney is an American aerospace manufacturer with global service operations. It is a subsidiary of Raytheon Technologies. Pratt & Whitney's aircraft engines are widely used in both civil aviation (especially airlines) and military aviat ...

. ;501-M80R3: A turboprop engine offered as an equal partnership between Allison and Pratt & Whitney to power Lockheed's proposed successor to the P-3 Orion, which was developed for the U.S. Navy's long-range air antisubmarine warfare (ASW) capable aircraft (LRAACA) program. ;501-M80R33: A propfan engine studied for the

that was based on the

core and rated at .

Military variants (T56)

Allison T56 mobile test unit MCAS Futenma 1982

;T56-A-1: (Series I) A engine delivering and residual jet thrust, which is equal to ; single-shaft 14-stage

compressor, cannular combustion chamber with 6-cylindrical through-flow combustion liners, 4-stage axial flow turbine; 13,800-rpm shaft connected to a 2-stage

reduction gear A gear train is a mechanical system formed by mounting gears on a frame so the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission ...

with a 12.5-to-1 ratio, consisting of a 3.125-to-1 spur set followed by a 4.0-to-1 planet set. ;T56-A-1A: A engine used on the

Lockheed C-130A Hercules The Lockheed C-130 Hercules is an American four-engine turboprop military transport aircraft designed and built by Lockheed Corporation, Lockheed (now Lockheed Martin). Capable of using unprepared runways for takeoffs and landings, the C-130 ...

. ;T56-A-2: Proposed gas generator engines for the McDonnell XHCH-1 helicopter. ;T56-A-3: A engine that was paired with an Aeroproducts propeller and test flown by the

Military Air Transport Service The Military Air Transport Service (MATS) is an inactive Department of Defense Unified Command. Activated on 1 June 1948, MATS was a consolidation of the United States Navy's Naval Air Transport Service (NATS) and the United States Air Force's ...

(MATS) on a pair of Convair YC-131C twin-turboprop aircraft between January and December 1955. ;T56-A-4: A engine for the C-131D executive transport/VC-131H VIP transport; also the proposed engines for the McDonnell XHRH-1 helicopter, with propeller drive and gas generator bleed for rotor-tip pressure jets. ;T56-A-5: A turboshaft version for the Piasecki YH-16B Transporter helicopter. ;T56-A-6: Gas generator engines for the NC-130B (58-0712)

boundary layer control Boundary layer control refers to methods of controlling the behaviour of fluid flow boundary layers. It may be desirable to reduce flow separation on fast vehicles to reduce the size of the wake (streamlining), which may reduce drag. Boundary l ...

(BLC) demonstrator. ;T56-A-7: (Series II) A engine flight-tested on a U.S. Air Force Allison

Boeing B-17 The Boeing B-17 Flying Fortress is a four-engined heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Relatively fast and high-flying for a bomber of its era, the B-17 was used primarily in the European Theater ...

flying

testbed aircraft A testbed aircraft is an aeroplane, helicopter or other kind of aircraft intended for flight research or testing the aircraft concepts or on-board equipment. These could be specially designed or modified from serial production aircraft. Use of te ...

, intended for the Lockheed C-130B; also used on the C-130E; produces about of static thrust. ;T56-A-7A: (Series II) Lockheed C-130B Hercules Starting May 1959. ;T56-A-7B: (Series II) Used on the U.S. Air Force C/HC/NC-130B, MC-130E, and WC-130F; similar to -A-7A. ;T56-A-8: (Series II) Entered production in 1959; the original engine on the Grumman E-2C, using the Aeroproducts A6441FN-248 propeller. ;T56-A-9: (Series I) Used on the U.S. Air Force C/AC/DC/GC/NC/RC-130A and the C-130D. ;T56-A-9D: (Series I)

starting December 1956 and on all Grumman E-2A Hawkeyes from 1960. ;T56-A-9E: (Series I) Similar to -A-9D. ;T56-A-10W: (Series II) Water injection model that entered production in 1960. ;T56-A-10WA: (Series II) Used on the P-3A, EP-3A, and RP-3A. ;T56-A-11: Ordered for 12

Royal Australian Air Force "Through Adversity to the Stars" , colours = , colours_label = , march = , mascot = , anniversaries = RAAF Anniversary Commemoration ...

C-130s in 1958. ;T56-A-13: (Series 3.5) Enhancements that improve SFC by 7.9%, increase maximum engine torque limit operation from , and increase turbine life; tested on a C-130H

in 2012. ;T56-A-14: (Series III) Lockheed P-3/EP-3/WP-3/AP-3/

CP-140 Aurora The Lockheed CP-140 Aurora is a patrol aircraft, maritime patrol aircraft operated by the Royal Canadian Air Force. The aircraft is based on the Lockheed P-3 Orion airframe, but mounts the electronics suite of the Lockheed S-3 Viking. Aurora ( ...

from August 1962; entered production in 1964. ;T56-A-14A: (Series 3.5) Fuel efficiency and reliability upgrade,

Lockheed WP-3D Orion The Lockheed WP-3D Orion is a highly modified P-3 Orion used by the Aircraft Operations Center division of the National Oceanic and Atmospheric Administration (NOAA). Only two of these aircraft exist, each incorporating numerous features for th ...

from May 2015. ;T56-A-15: (Series III)

Lockheed C-130H Hercules The Lockheed C-130 Hercules is an American four-engine turboprop military transport aircraft designed and built by Lockheed (now Lockheed Martin). Capable of using unprepared runways for takeoffs and landings, the C-130 was originally design ...

USAF from June 1974. ;T56-A-15A: (Series 3.5) Upgrade of the T56-A-15 on the Air Force LC-130H. ;T56-A-16: (Series III) Used on the KC-130F, KC-130R, LC-130F, and LC-130R. ;T56-A-16A: (Series 3.5). ;T56-A-18: A , variant that was designed and first run in 1965; Navy-funded development with air-cooled blades and vanes in the first two stages; 50-hour preliminary flight rating test completed in 1968; turbine inlet temperature of ; introduced major

gearbox Propulsion transmission is the mode of transmitting and controlling propulsion power of a machine. The term ''transmission'' properly refers to the whole drivetrain, including clutch, gearbox, prop shaft (for rear-wheel drive vehicles), differe ...

update after 4,000 hours of back-to-back testing, featuring a double helical first gear stage, a planetary

helical gear A gear is a rotating circular machine part having cut teeth or, in the case of a cogwheel or gearwheel, inserted teeth (called ''cogs''), which mesh with another (compatible) toothed part to transmit (convert) torque and speed. The basic p ...

for the second stage, and fewer parts for the accessory gearing (compared with a first-stage

spur gear Spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk with teeth projecting radially. Viewing the gear at 90 degrees from the shaft length (side on) the tooth faces are straight and aligned parallel to ...

, second-stage planetary spur gear, and separable clamped components in the accessory gearing for the T56-A-7 gearbox); used an eight-bladed Hamilton Standard variable-

camber Camber may refer to a variety of curvatures and angles: * Camber angle, the angle made by the wheels of a vehicle * Camber beam, an upward curvature of a joist to compensate for load deflection due in buildings * Camber thrust in bike technology * ...

propeller. ;T56-A-20: Proposed in 1968 to be funded within the 1969 fiscal year component improvement program (CIP). ;T56-A-100: (Series IV) U.S. Air Force EMDP demonstrator ;T56-A-101: (Series IV) Offered for the

. ;T56-A-422: Used on U.S. Navy Northrop Grumman E-2C Hawkeye aircraft. ;T56-A-423: Used on U.S. Navy Lockheed EC-130G and EC-130Q aircraft. ;T56-A-425: (Series III) Replaced the T56-A-8 on the Grumman E-2C, using the Hamilton 54460-1 propeller;

Grumman C-2A Greyhound The Grumman C-2 Greyhound is a twin-engine, high-wing cargo aircraft designed to carry supplies, mail, and passengers to and from aircraft carriers of the United States Navy. Its primary mission is carrier onboard delivery (COD). The aircraft ...

from June 1974. ;T56-A-426: Used on the C-2A, E-2B, and TE-2A ;T56-A-427: (Series IV)

Northrop Grumman E-2 Hawkeye The Northrop Grumman E-2 Hawkeye is an American all-weather, carrier-capable tactical airborne early warning (AEW) aircraft. This twin-turboprop aircraft was designed and developed during the late 1950s and early 1960s by the Grumman Aircraft ...

upgrades from 1972. ;T56-A-427A: (Series IV) Used on the Northrop Grumman E-2D Advanced Hawkeye (AHE), which first flew in 2007.

T701

;T701-AD-700: An

powerplant developed from the 501-M62B and intended for use on the canceled three-engine

heavy-lift helicopter; air flow of , pressure ratio of 12.8:1, turbine temperature of , and power/weight ratio of 6.85:1.

References

Bibliography

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External links