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Capital Airlines Vickers Viscount
Image by james_gordon_losangeles
The Vickers Viscount was a British medium-range turboprop airliner first flown in 1948 by Vickers-Armstrongs, making it the first such aircraft to enter service in the world. A product of the Brabazon Committee, it was a ground-breaking aircraft making use of a brand-new form of propulsion, the turboprop engine, replacing the conventional piston engine.
The Viscount was well received by the public for its favourable cabin conditions, which included pressurisation, significant reductions in vibration and noise, and large panoramic windows. Due to these unique advantages, it went on to be one of the most successful and profitable of the first generation post-war transport aircraft types; a total of 445 Viscounts were built for a wide range of international customers, including the North American market.
Development
Origins
The Viscount was developed in response to the Brabazon Committee’s Type II design for post-war use, calling for a small sized, medium range pressurised aircraft to fly its less-travelled routes, carrying 24 passengers up to 1,750 mi (2,816 km) at 200 mph (320 km/h). During discussions between the committee and Vickers’ Chief Designer Rex Pierson, Vickers advocated the use of turboprop power, believing piston engines to be a dead end in aviation. The Brabazon committee was not so convinced, but agreed to split the specification into two types, the Type IIA using piston power, which led to the Airspeed Ambassador, and the turboprop-powered Type IIB which Vickers was selected to develop in April 1945. British European Airways (BEA) was involved in the design and asked that the aircraft carry 32 passengers instead, but remained otherwise similar.
The first design in June 1945 was based on the Viking with four turbo-prop engines and 24-seat and designated the VC-2 or Type 453. Later a double-bubble fuselage was proposed to give extra underfloor cargo space. Both these early designs were not pressurised and it was soon realised that for economic operations at 20,000 ft (6,100 m) it needed pressurisation, the two early designs were abandoned and a circular cross-section variant was offered at the beginning of 1946. The resulting 28-seat VC-2 was financed by the Ministry of Supply with an order for two prototypes but before the contract for the prototypes was signed the government asked for the capacity to be increased to 32-seats, this resulted in a fuselage increase from 65 ft 5 in (19.94 m) to 74 ft 6 in (22.71 m) and an increased wingspan of 89 ft (27 m).
The contract for the aircraft to Air Ministry specification C.16/46 was signed on 9 March 1946 and Vickers allocated the designation Type 609 and the name Viceroy to the aircraft. Although George Edwards had always favoured using the Dart other engines were still being considered including the Mamba which the government specified for the two prototypes, the choice of the Mamba engine increased the gross weight of the aircraft but Vickers made sure that the engine nacelle would fit either the Mamba or Dart.
While the Dart was making better progress in development than the Mamba the government asked in August 1947 for the second prototype to be Dart-powered. The second prototype was designated as the Type 630 and was later named as the Viscount. The first prototype already under construction was converted to the Dart engine as a Type 630 as well.
The resulting Vickers Type 630 design was completed at Brooklands by Chief Designer Rex Pierson and his staff in 1945, a 32-seat airliner powered by four Rolls-Royce Dart engines providing a cruising speed of 275 mph (443 km/h). An order for two prototypes was placed in March 1946, and construction started almost immediately in the company’s Foxwarren Experimental Department. Originally to be named Viceroy after the viceroy of India, Lord Louis Mountbatten; the aircraft was renamed as Viscount following India’s independence in 1947. There was some work on replacing the Darts with the Armstrong Siddeley Mamba, but this was dropped by the time the prototypes were reaching completion. After Pierson’s death in 1948, George Edwards (later Sir George Edwards) took over as chief designer and assumed all technical control over the Viscount project.
Prototypes
Never having flown other than piston-engined aircraft I was tremendously impressed with the smoothness of the four Dart turboprop engines. As I sat in the cabin, a coin was balanced on its edge on the table…
Test Pilot Joseph Summers, commenting on flight characteristics of the Viscount.
The prototype Type 630, registered G-AHRF, made its maiden flight from the grass airfield at Wisley on 16 July 1948, piloted by Joseph "Mutt" Summers, Vickers’ chief test pilot. The design was considered too small and slow at 275 mph (443 km/h), making the per passenger operating costs too high for regular service, and BEA had placed an order for 20 piston engined Airspeed Ambassadors in 1947. Retrospectively commenting on Britain’s aviation industry, Duncan Burn stated: Had BEA committed itself to full support of the Viscount… it was quite likely that the smaller version would have gone into production… It was in a sense BEA’s lack of enthusiasm for the [Type] 630 which made possible the [Viscount’s] success.
Early flight trials, however, showed the qualities of a turboprop, resulting in a February 1949 order from the Ministry of Supply for a prototype of a stretched version with more powerful engines, the Type 700. Meanwhile, the first prototype Type 630 was awarded a restricted Certificate of Airworthiness on 15 September 1949, followed by a full certificate on 27 July 1950, which allowed the aircraft to be placed into service with BEA on 29 July to familiarise the pilots and ground crew with the new aircraft. It flew scheduled flights between London and Paris, and London and Edinburgh for a month. The 29 July flight between Northolt and Paris – Le Bourget Airport with 14 paying passengers was the first scheduled airline flight by any turbine-powered aircraft.
The second prototype Viscount, the Type 663 testbed, had two Rolls-Royce Tay turbojet engines and first flew in RAF markings as VX217 at Wisley on 15 March 1950.[16] It was demonstrated at the Farnborough SBAC Show in September and was later used in the development of powered controls for the Valiant bomber.[13] It later saw use as a test bed by Boulton Paul Ltd for the development of electronic flight control systems.
The designers then went back to the drawing board and the aircraft emerged as the larger Type 700 with up to 48 passengers (53 in some configurations), and a cruising speed of 308 mph (496 km/h). The new prototype G-AMAV first flew from Brooklands on 28 August 1950, and served as a development aircraft for the type for several years. In late August 1950, BEA placed an order for 20 aircraft; further orders would come in the following year from operators such as Air France, Aer Lingus and Misrair.
Performance and changes
One commentator, after travelling on board an Air France Viscount, wrote in 1953: "Noise level was less than that of piston engines. It was a definite relief to be rid of the rough vibrations… The turboprop is an excellent shorthaul airplane and a definite crowd pleaser. The substitution of a lower constant pitch noise and smoothness for the vibration, grunts, and groans of the piston engine gives the hesitant passenger a feeling of confidence. Another comfort feature of the Viscount was its large cabin windows, these were considerably bigger than those of later highly-pressurised aircraft. From an operator’s perspective, the Viscount also had the advantage of lower operational costs than many rival aircraft designs.
In the field of intercity transports employing the propeller turbine, the Vickers Viscount Model 700 appears to be considerably superior to anything else in its class. [It has] exceptionally fine flying qualities and is a most comfortable vehicle in which to travel.
John Watkins, Chief Technical Officer of Trans Australia Airlines.
All production Viscounts were powered by the Rolls-Royce Dart turboprop engine; Rolls-Royce extensively developed the Dart engine due to its popularity and use on the Viscount and several later aircraft. One key model was the Dart 506 engine, which had far greater fuel efficiency than earlier models, this enabled the airlines to deploy their Viscounts onto longer routes and to carry a greater maximum weight. Coupled with the availability of increasingly powerful engines Vickers continued to develop and modify the Viscount’s design; later models could carry increasing numbers of passengers and had fewer load limitations.
The Viscount’s good performance and popularity with customers encouraged Vickers to privately finance and develop an enlarged and re-engined variant of the Viscount, later designated as the Vickers Vanguard. The Vanguard drew extensively from the knowledge and design of the Viscount, and likewise maintained its advantage of lower operating costs over pure jet-powered aircraft, but its disadvantage in being slower than jet aircraft became increasingly critical as jets became more available over time.
Operational history
Regular passenger flights were launched by BEA in April 1953, this was the world’s first scheduled turboprop airline service. BEA proceeded to become a large user of the Viscount, as well the rival Handley Page Dart Herald; by mid-1958 BEA’s Viscount fleet had carried over 2.75 million passengers over 200,000 flight hours. Following BEA’s launch of the type, multiple independent charter operators such as British Eagle were quick to adopt the Viscount into their fleets. During the 1960s, the Viscount had formed the backbone of domestic air travel in Scotland.
The early operational service of the Viscount quickly proved it to have significant performance advances over its rivals, and orders rapidly rose as a result; up to November 1952 only 42 aircraft had been ordered; by the end of 1953, early on in which it had been introduced, the order book had risen to 90, and 160 by the end of the following year. Vickers was able to quickly respond to the new orders as it had gambled on such orders emerging and early on the decision had been taken to commit to a high production rate at the company’s own risk. In 1957, the Vickers production line was producing the Viscount at a rate of one aircraft every three days.
In October 1953, the Viscount 700 prototype G-AMAV achieved the fastest time (40 hours 41 minutes flying time) in the transport section of the 12,367 mi (19,903 km) air race from London to Christchurch, New Zealand. The aircraft averaged 320 mph (520 km/h) in the event, crossing the finishing line nine hours ahead of its closest rival, a Douglas DC-6A of KLM, with the latter winning on handicap. En route, equipped with extra fuel tanks, it flew 3,530 mi (5,680 km) nonstop from the Cocos (Keeling) Islands to Melbourne’s Essendon Airport in 10 hours 16 minutes.
Trans Australia Airlines (TAA) received its first Viscount in 1954, and the aircraft quickly proved profitable, leading to additional orders.[40] The Viscount proved to be an invaluable aircraft for TAA, aviation author John Gunn stating that TAA had achieved dominance on Australia’s trunk routes with its turboprop Viscounts". TAA would procure over a dozen Viscounts, and purchase later turboprop aircraft such as the Fokker F27 Friendship;[N 6] it later transitioned to jet aircraft as passenger demand outgrew the capacity of the Viscounts. In order to compete with its rival TAA, another Australian airline, Ansett-ANA also procured its own small Viscount fleet; the Viscount allowed Ansett to set out a faster and superior service than the larger TAA for the first time.
The first North American airline to use turboprop aircraft was Trans-Canada Air Lines (TCA), with a small fleet of Type 700 Viscounts. Initially, TCA was cautious of the Viscount due to the turboprop engine being a new technology, and there had been a preference for acquiring the piston-engined Convair CV-240 instead; praise of the Viscount from pilots and a promise from Vickers to make any design changes desired by TCA persuaded it to procure the Viscount instead. On 6 December 1954, the first Viscount was delivered to Canada in a large media event which including an improvised aerial display.
TCA became a prolific operator of the type, having placed multiple follow-up orders for addition Viscounts; by 1958 TCA had an operational fleet of 51 Viscounts. Aviation author Peter Pigott later wrote that: For TCA and Vickers, the Viscount was a public relations coup. Passengers loved the quiet ride and panoramic windows. No other airline in North America flew turbo-prop airliners then, and no other British aircraft was bought by American airlines in such quantity. TCA would operate the Viscount for two decades until its successor company, Air Canada, ended Viscount services in 1974, the type was replaced by the McDonnell Douglas DC-9.
TCA’s procurement of the Viscount generated considerable interest from airlines and industry figures across the United States, including American aviation pioneer Howard Hughes, Hughes purchased 15 Viscounts immediately after personally flying one. America’s Capital Airlines became an important operator of the Type 700 Viscount, using it heavily throughout the eastern U.S. routes; it was reported in 1958 that Capital had accumulated over 350,000 flight hours on its Viscounts, more than any other operator.
Continental Airlines and Northeast Airlines also became US Viscount operators.
National Airways Viscount at Wellington Airport, 1975
The first airline in Latin America to operate the Viscount was Cubana de Aviación. Cubana’s -755D Viscounts, delivered in 1956, were placed on the Havana-Miami and Varadero-Miami routes, and were successful at raising Cubana’s market share on these routes.[53] During the 1958 Cuban elections, a Cubana Viscount was hijacked by gunmen aligned with the 26th of July Movement, the aircraft crash-landed on the sea, reportedly killing 17 of the 20 occupants. When the U.S. government imposed its embargo on Cuba in 1962, Cubana decided to sell all of its Viscounts, they were replaced by Soviet-built turboprop aircraft.
South African Airways (SAA) was another major operator of the Viscount, by January 1959 it was operating on all of SAA’s domestic routes. In 1961, SAA had seven Viscounts, and acquired a further aircraft from Cuba in the following year. In 1965, SAA began receiving Boeing 727s, which had been selected the previous year as a jet-powered replacement for the Viscount. SAA sold its last Viscount to British Midland in the 1970s.
Central African Airways (CAA) had been a traditional customer of Vickers, already operating a number of Vickers Vikings when it received its first Viscount on 25 April 1956. The introduction of the Viscount roughly coincided with the opening of a major airport at Salisbury, the Viscount became the mainstay of the route between Johanesburg in South Africa, Salisbury (now renamed Harare) in modern-day Zimbabwe, and London, England. CAA had enough Viscounts to entirely replace its Viking fleet and to occasionally lease them to other operators. More Viscounts were purchased by CAA right up until 1965, at which point CAA announced its intention to procure the British Aircraft Corporation’s jet-powered BAC 1-11 successor as the long-term successor to the Viscount.
BEA, and its nationalised successor British Airways (BA), vigorously operated the Viscount on Britain’s domestic routes.
In the 1980s, British Airways began withdrawing its aging Viscount fleet; all BA Viscount operations in Scotland had ended in 1982. Former BA aircraft were often sold on to charter operators such as British Air Ferries. Some airlines chose to replace the Viscount with a newer turboprop aircraft, the Hawker Siddeley HS 748. On 18 April 1996, British World Airlines conducted the last Viscount passenger service in Britain, exactly 46 years after BEA’s inaugural flight; on board the flight were Sir George Edwards and Sir Peter Masefield.
In late 1960, the People’s Republic of China had begun negotiations with Vickers for as many as 40 Viscounts, however negotiations were protracted due to political tensions. At this point, China sought arrangements to purchase Viscounts second-hand from existing operators, and later achieved successive deals regarding the Viscount with Britain directly. The last batch of six aircraft built were for the Civil Aviation Administration of China, which were delivered during 1964; at the end of production a total of 445 Viscounts had been manufactured. Many Viscounts were refurbished and saw new service with African operators, sales of these second-hand aircraft continued into the 1990s.
Specifications (Type 810)
General characteristics
Crew: Two pilots + cabin crew
Capacity: 75 passengers
Length: 85 ft 8 in (26.11 m)
Wingspan: 93 ft 8 in (28.56 m)
Height: 26 ft 9 in (8.15 m)
Wing area: 963 ft² (89 m²)
Empty weight: 41,276 lb (18,722 kg)
Max. takeoff weight: 67,500 lb (30,617 kg)
Powerplant: 4 × Rolls-Royce Dart RDa.7/1 Mk 525 turboprop, 1,990 shp (1,484 kW) each
Performance
Maximum speed: 352 mph (566 km/h)
Range: 1,380 mi (2,220 km)
Service ceiling: 25,000 ft (7,620 m)
Wing loading: 75 lb/ft² (368 kg/m²)
Power/mass: 0.12 hp/lb (0.19 kW/kg)
M134 Minigun
Image by Alex Drennan
The M134 Minigun is a 7.62×51 mm NATO, six-barreled machine gun with a high rate of fire (2,000 to 6,000 rounds per minute). It features Gatling-style rotating barrels with an external power source, normally an electric motor. The "Mini" in the name is in comparison to designs that use a similar firing mechanism but larger shells, such as General Electric’s earlier 20-millimeter M61 Vulcan, and "gun" for a caliber size smaller than that of a cannon, typically 20 mm and higher.
The Minigun is used several branches of the U.S. military. Versions are designated M134 and XM196 by the United States Army, and GAU-2/A and GAU-17/A by the U.S. Air Force and U.S. Navy.
"Minigun" refers to a specific model of weapon that General Electric originally produced, but the term "minigun" has popularly come to refer to any externally powered Gatling gun of rifle caliber. The term is also used to refer to guns of similar rates of fire and configuration regardless of power source and caliber.
Contents [hide]
1 History 1.1 Background: electrically driven Gatling gun
1.2 Minigun: 1960s–Vietnam
1.3 Dillon Aero minigun
2 Design and variants 2.1 Gun pods and other aircraft mounts
3 Users
4 See also
5 References
6 External links
History[edit]
Background: electrically driven Gatling gun[edit]
The ancestor to the modern minigun was made in the 1860s. Richard Jordan Gatling replaced the hand cranked mechanism of a rifle-caliber Gatling gun with an electric motor, a relatively new invention at the time. Even after Gatling slowed down the mechanism, the new electric-powered Gatling gun had a theoretical rate of fire of 3,000 rounds per minute, roughly three times the rate of a typical modern, single-barreled machine gun. Gatling’s electric-powered design received U.S. Patent #502,185 on July 25, 1893.[1] Despite Gatling’s improvements, the Gatling gun fell into disuse after cheaper, lighter-weight, recoil and gas operated machine guns were invented; Gatling himself went bankrupt.[2]
During World War I, several German companies were working on externally powered guns for use in aircraft. Of those, the best-known today is perhaps the Fokker-Leimberger, an externally powered 12 barrel rotary gun using the 7.92x57mm Mauser round; it was claimed to be capable of firing over 7,000 rpm, but suffered from frequent cartridge-case ruptures[3] due to its "nutcracker", rotary split-breech design, which is fairly different from that of a Gatling.[4] None of these German guns went into production during the war, although a competing Siemens prototype (possibly using a different action) which was tried on the Western Front scored a victory in aerial combat.[3] The British also experimented with this type of split-breech during the 1950s, but they were also unsuccessful.[5]
A couple of externally powered rotary gun designs were patented although never used. During World War II, the blowback-operated Neal submachine gun that used rotating barrels firing .22LR rounds at a rate of 3000rpm was also developed as a weapon for US forces, but it was felt that existing submachine guns fulfilled its role.[relevant? – discuss]
Minigun: 1960s–Vietnam[edit]
In the 1960s, the United States Armed Forces began exploring modern variants of the electric-powered, rotating barrel Gatling-style weapons for use in the Vietnam War. American forces in the Vietnam War, which used helicopters as one of the primary means of transporting soldiers and equipment through the dense jungle, found that the thin-skinned helicopters were very vulnerable to small arms fire and rocket-propelled grenade (RPG) attacks when they slowed down to land. Although helicopters had mounted single-barrel machine guns, using them to repel attackers hidden in the dense jungle foliage often led to barrels overheating or cartridge jams.[citation needed]
A U.S. Air Force rotary-wing crewman fires a minigun during the Vietnam War.
In order to develop a weapon with a more reliable, higher rate of fire, General Electric designers scaled down the rotating-barrel 20 mm M61 Vulcan cannon for 7.62×51 mm NATO ammunition. The resulting weapon, designated M134 and known popularly as the Minigun, could fire up to 4,000 rounds per minute without overheating. The gun was originally specified to fire at 6,000 rpm, but this was later lowered to 4,000 rpm.
The Minigun was mounted on Hughes OH-6 Cayuse and Bell OH-58 Kiowa side pods; in the turret and on pylon pods of Bell AH-1 Cobra attack helicopters; and on door, pylon and pod mounts on Bell UH-1 Iroquois transport helicopters.[citation needed] Several larger aircraft were outfitted with miniguns specifically for close air support: the Cessna A-37 Dragonfly with an internal gun and with pods on wing hardpoints; and the Douglas A-1 Skyraider, also with pods on wing hardpoints. Other famous gunship airplanes were the Douglas AC-47 Spooky, the Fairchild AC-119, and the Lockheed AC-130.[citation needed]
Dillon Aero minigun[edit]
The U.S. government had procured some 10,000 miniguns during the Vietnam War. By 1975, production of spare parts had ceased with the Army in possession of a large inventory. By 1985, there were few spares left in the inventory. Units that received miniguns could not maintain them, so by the 1990s only Task Force 160 (later named the 160th Special Operations Aviation Regiment (Airborne) or 160th SOAR) and some Navy Special Boat Units kept them in regular use. Around 1995, the 160th SOAR began acquiring spare miniguns. Industry had a difficult time reproducing parts according to the original blueprints, so models that were being procured were mechanically unreliable and mixed with the inventory of working spares. This resulted in using a mixed batch of working and unreliable weapons. This fact was unknown to the 160th SOAR, and the use of miniguns that would not work shook the unit’s confidence in the system. The 160th was on the verge of dropping the Minigun from its inventory entirely, which would essentially have ended its service life in the U.S. military.[6]
Around 1990, Dillon Aero acquired a large number of miniguns and spares from "a foreign user". The guns kept failing to shoot continuously, revealing that they were actually worn-out weapons. The company decided to fix the problems encountered, rather than simply putting the guns into storage. Fixing failure problems ended up improving the minigun’s overall design.[6] Dillon’s efforts to improve the minigun reached the 160th SOAR, and Dillon was invited to Fort Campbell, Kentucky to demonstrate its products. A delinker, used to separate cartridges from ammunition belts and feed them into the gun housing; and other parts; were tested on Campbell’s ranges. The 160th SOAR liked the delinker’s performance and began ordering them by 1997. This prompted Dillon to improve other design aspects, including the bolt, housing and barrel. Between 1997 and 2001, Dillon Aero was producing 25-30 products a year. In 2001, it was working on a new bolt design that increased performance and service life. By 2002, virtually every component of the minigun had been improved, so Dillon began producing entire weapons with its improved components. The guns were purchased quickly by the 160th SOAR as its standardized weapon system. The gun then went through the Army’s formal procurement system approval process and in 2003 the Dillon Aero minigun was certified and designated M134D.[6]
The core of the M134D was a steel housing and steel rotor. To focus on weight reduction, a titanium housing and rotor were introduced, creating the M134D-T. This reduced weight from 62 pounds (28 kg) to 41 pounds (19 kg). The gun housing had a 500,000 round lifespan before it wore out, which was higher than a conventional machine gun’s 40,000 round lifespan but was a reduced time for a rotary gun. A hybrid of the two weapons resulted in the M134D-H, which had a steel housing and titanium rotor. It was cheaper with the steel component, was only one pound (450 grams) heavier than the M134D-T, and had an increased lifespan of 1.5 million rounds. The M134D-H is currently in use on various 160th Regiment platforms.[6]
Dillon also created specialized mounts and ammunition-handling systems. Initially, mounts were only made for aviation systems. Then from 2003 to 2005, the Navy began mounting Dillon miniguns on specialized small boats. In 2005, the Naval Surface Warfare Center Crane Division procured guns to mount on Humvees. Army Special Forces units on the ground in Iraq were being engaged daily, so they mounted M134Ds on vehicles. When attackers ambushed, they were engaged by the miniguns and quickly broke off the attack. Radio chatter from the enemy showed they were confused about this new weapon and were told not to attack. The Special Forces units took to concealing their weapons, because the enemy was too afraid to confront the minigun. As a further testament to the minigun’s psychological effect, regular Army units began painting and tying together six sections of PVC pipe, to make insurgents think they were armed with it and dissuade them from attacking.[6]
Design and variants[edit]
A Royal Navy minigun, separated from mounting and ammunition
The basic minigun is a six-barrel, air-cooled, and electrically driven rotary machine gun. The electric drive rotates the weapon within its housing, with a rotating firing pin assembly and rotary chamber.[7] The minigun’s multi-barrel design helps prevent overheating, but also serves other functions. Multiple barrels allow for a greater capacity for a high firing rate, since the serial process of firing/extraction/loading is taking place in all barrels simultaneously. Thus, as one barrel fires, two others are in different stages of shell extraction and another three are being loaded. The minigun is composed of multiple closed-bolt rifle barrels arranged in a circular housing. The barrels are rotated by an external power source, usually electric, pneumatic, or hydraulic. Other rotating-barrel cannons are powered by the gas pressure or recoil energy of fired cartridges. A gas-operated variant, designated XM133, a gas operated variant., was also developed.[8] It is near identical but has barrels with ports that align with the piston drive in the center of the barrel cluster. It fired over 3000 rpm but was not put into production.[citation needed]
While the weapon can feed from linked ammunition, it requires a delinking feeder to strip the links as the rounds are introduced to the chambers. The original feeder unit was designated MAU-56/A, but has since been replaced by an improved MAU-201/A unit.[9]
A U.S. Navy Special Warfare Combatant-craft Crewmen (SWCC) firing a Minigun at the Stennis Space Center in Mississippi, August 2009
The General Electric minigun is in use in several branches of the U.S. military, under a number of designations. The basic fixed armament version was given the designation M134 by the United States Army, while the same weapon was designated GAU-2/A (on a fixed mount) and GAU-17/A (flexible mount) by the United States Air Force (USAF) and United States Navy (USN). The USAF minigun variant has three versions, while the US Army weapon appears to have incorporated several improvements without a change in designation. The M134D is an improved version of the M134 designed and manufactured by Dillon Aero,[10] while Garwood Industries manufactures the the M134G variant.[11] Available sources show a relation between both M134 and GAU-2/A and M134 and GAU-2B/A.[12][13] A separate variant, designated XM196, with an added ejection sprocket was developed specifically for the XM53 Armament Subsystem on the Lockheed AH-56 Cheyenne helicopter.[14]
Another variant was developed by the USAF specifically for flexible installations, beginning primarily with the Bell UH-1N Twin Huey helicopter, as the GAU-17/A. Produced by General Dynamics, this version has a slotted flash hider. The primary end users of the GAU-17/A have been the USN and the United States Marine Corps (USMC), which mount the gun as defensive armament on a number of helicopters and surface ships. The weapon is part of both the A/A49E-11 armament system on the UH-1N; and of the A/A49E-13 armament subsystem on the USAF Sikorsky HH-60H Pave Hawk helicopter. The weapons on these systems feature a selectable fire rate of either 2,000 or 4,000 rpm. There is mention of a possible GAUSE-17 designation (GAU-Shipboard Equipment-17), in reference to the system when mounted on surface ships, though this would not follow the official ASETDS designation system’s format.[15][16]
GAU-17/A
US Army Designation
US Air Force Designation
US Navy Designation
Description
XM134/M134 GAU-2/A N/A 7.62×51 mm NATO GE "Minigun" 6-barreled machine gun
N/A GAU-2A/A N/A GAU-2/A variant; unknown differences
M134 GAU-2B/A Mk 25 Mod 0 GAU-2A/A variant; unknown differences
N/A GAU-17/A N/A GAU-2B/A variant; optimized for flexible use, uses either an MAU-201/A or MAU-56/A delinking feeder.
XM214 N/A N/A Scaled-down variant of the XM134 firing the 5.56mmx45mm NATO round.
XM196 N/A N/A M134/GAU-2B/A variant; housing modified by addition of an ejection sprocket; for use in the XM53 armament subsystem on the AH-56 helicopter
Gun pods and other aircraft mounts[edit]
SUU-11/A pod in the cargo door of an AC-47
One of the first applications of the weapon was in aircraft armament pods. These gun pods were used by a wide variety of fixed and rotary wing aircraft mainly during the Vietnam War, remaining in inventory for a period afterward. The standard pod, designated SUU-11/A by the Air Force and M18 by the U.S. Army, was a relatively simple unit, completely self-contained, with a 1,500 round magazine directly feeding delinked ammunition into the weapon. This means the Minigun fitted to the pod does not require the standard MAU-56/A delinking feeder unit.[17] A number of variations of this pod exist.
Initially on fixed-wing gunships such as the Douglas AC-47 Spooky and Fairchild AC-119, the side-firing armament was fitted by combining SUU-11/A aircraft pods, often with their aerodynamic front fairings removed, with a locally fabricated mount. These pods were essentially unmodified, required no external power, and were linked to the aircraft’s fire controls. The need for those pods for other missions led to the development and fielding of a purpose built "Minigun module" for gunship use, designated the MXU-470/A. These units first arrived in January 1967 with features such as an improved 2,000 round drum and electric feeder allowing simplified reloading in flight. The initial units were unreliable and were withdrawn almost immediately.[18] By the end of the year, however, the difficulties had been worked out and the units were again being fitted to AC-47s, AC-119s, AC-130s, and even being proposed for lighter aircraft such as the Cessna O-2 Skymaster.[19] A fit of two MXU-470/As was also tested on the Fairchild AU-23A Peacemaker, though the Royal Thai Air Force later elected to use another configuration with the M197 20 mm cannon.[20]
In September 2013, Dillon Aero released the DGP2300 gun pod for the M134D-H. It contains 3,000 rounds, enough ammunition to fire the minigun for a full minute. The system is entirely self-contained, so it can be mounted on any aircraft that can handle the weight, rotational torque, and recoil force (190 lb (86 kg)) of the gun. The pod has its own battery which can be wired into the aircraft’s electrical system to maintain a charge.[21]
MXU-470/A modules in an AC-47
Douglas AC-47 Spooky with SUU-11/A pods at Nha Trang Air Base in South Vietnam
U.S. Army Designation
U.S. Air Force Designation
Description
XM18 SUU-11/A Gun pod fitted with the GAU-2/A/M134 7.62 mm machine gun and fixed rate of fire of 4,000 RPM[22]
XM18E1/M18 SUU-11A/A SUU-11/A/XM18 variant; various improvements including additional auxiliary power and selectable fire-rate capability (2,000 or 4,000 RPM)[23]
M18E1/A1 SUU-11B/A SUU-11A/A/M18 variant; differences modified selectable fire-rate capability (3,000 or 6,000 RPM)[12]
N/A MXU-470/A Emerson Electric module for mounting a GAU-2B/A minigun; used in AC-47, AC-119G/K, and AC-130A/E/H aircraft
Main articles: U.S. aircraft gun pods and U.S. Helicopter Armament Subsystems
Various iterations of the minigun have also been used in a number of armament subsystems for helicopters, with most of these subsystems being created by the United States. The first systems utilized the weapon in a forward firing role for a variety of helicopters, some of the most prominent examples being the M21 armament subsystem for the Bell UH-1 Iroquois and the M27 for the Hughes OH-6 Cayuse. It also formed the primary turret-mounted armament for a number of members of the Bell AH-1 Cobra family. The weapon was also used as a pintle-mounted door gun on a wide variety of transport helicopters, a role it continues to serve in today.
US Navy Designation
Description
Mk 77 Mod 0 Machine gun mount for the GAU-2/Mk 25 Mod 0/GAU-17 series of machine guns; deck mount applications
Users[edit]
Afghanistan
Australia
Austria[24]
Brazil
Canada
Chile
Colombia
Finland[25]
France[26]
Georgia[27]
Iraq
Israel
Italy
Mexico[28]
Malaysia
Morocco
Netherlands
Norway
Philippines
Poland[29]
Republic of Korea
Sierra Leone
Turkey
Thailand
Pakistan
United Kingdom
United States
Tahiti[30]