An attack helicopter is a military helicopter with the primary role of an attack aircraft, with the capability of engaging targets on the ground, such as enemy infantry and armored vehicles. Due to their heavy armament they are sometimes called helicopter gunships.
Weapons used on attack helicopters can include autocannons, machine-guns, rockets, and guided missiles such as the Hellfire. Many attack helicopters are also capable of carrying air to air missiles, though mostly for purposes of self-defense. Today's attack helicopter has two main roles: first, to provide direct and accurate close air support for ground troops, and the second, in the anti-tank role to destroy enemy armor concentrations. Attack helicopters are also used to supplement lighter helicopters in the armed scout role. In combat, an attack helicopter is projected to destroy around 17 times its own production cost before it is destroyed.
Background and development
Low-speed, fixed wing aircraft like the military version of the Piper J-3 Cub, the L-4 Grasshopper, had been used later in World War II following Operation Overlord by a few U.S. Army artillery spotter units over France, field-outfitted with either two or four bazooka rocket launchers attached to the wing struts, against German armored fighting vehicles. During the summer of 1944, U.S. Army Major Charles Carpenter managed to successfully take on an anti-armor role with his rocket-armed Piper L-4. His L-4, named Rosie the Rocketeer, armed with six bazookas, had a notable anti-armor success during an engagement during the Battle of Arracourt on September 20, 1944, knocking out at least four German armored vehicles, as a pioneering example of taking on heavy enemy armor from a slow-flying aircraft. This role was something that was also likely to be achievable after World War II, from the increasing numbers of post-war military helicopter designs. The only American helicopter in use during the war years, the Sikorsky R-4, was only being used for rescue and were still very much experimental in nature.
In the early 1950s various countries around the world started to make increased use of helicopters in their operations in transport and liaison roles. Later on it was realised that these helicopters, successors to the World War II-era Sikorsky R-4, could be armed with weapons in order to provide them with limited combat capability. Early examples include armed Sikorsky H-34's in service with the US Air Force and armed Mil Mi-4 in service with the Soviet Air Forces. This trend continued into the 1960s with the deployment of armed Bell UH-1 Iroquois' and Mil Mi-8's during the Vietnam War. These helicopters proved to be moderately successful in these configurations, but due to a lack of armor protection and speed, they were ultimately ineffective platforms for mounting weapons in higher-threat ground combat environments.
Since the 1960s various countries around the world started to design and develop various types of helicopters with the purpose of providing a heavily armed and protected aerial vehicle that can perform a variety of combat roles, from reconnaissance to aerial assault missions.
By the 1990s, the missile-armed attack helicopter evolved into a primary anti-tank weapon. Able to quickly move about the battlefield and launch fleeting "pop-up attacks", helicopters presented a major threat even with the presence of organic air defenses. The helicopter gunship became a major tool against tank warfare, and most attack helicopters became more and more optimized for the antitank mission.
In the mid-1960s the U.S. Army concluded that a purpose-built attack helicopter with more speed and firepower than current armed helicopters was required in the face of increasingly intense ground fire (often using heavy machine guns and anti-tank rockets) from Viet Cong and NVA troops. Based on this realization, and with the growing involvement in Vietnam, the U.S. Army developed the requirements for a dedicated attack helicopter, the Advanced Aerial Fire Support System (AAFSS). The aircraft design selected for this program in 1965, was Lockheed's AH-56 Cheyenne.
As the Army began its acquisition of a dedicated attack helicopter, it sought options to improve performance over the continued use of improvised interim aircraft (such as the UH-1B/C). In late 1965, a panel of high-level officers was selected to evaluate several prototype versions of armed and attack helicopters to determine which provided the most significant increase in capability to the UH-1B. The three aircraft ranked highest during the evaluation; the Sikorsky S-61, Kaman H-2 "Tomahawk", and the Bell AH-1 Cobra, were selected to compete in flight trials conducted by the Army's Aviation Test Activity. Upon completion of the flight evaluations, the Test Activity recommended Bell's Huey Cobra to be an interim armed helicopter until the Cheyenne was fielded. On 13 April 1966, the U.S. Army awarded Bell Helicopter Company a production contract for 110 AH-1G Cobras. The Cobra had a tandem cockpit seating arrangement (vs UH-1 side-by-side) to make the aircraft a smaller frontal target, increased armor protection, and greater speed.
In 1967, the first AH-1Gs were deployed to Vietnam, around the same time that the Cheyenne successfully completed its first flight and initial flight evaluations. And while the Cheyenne program suffered setbacks over the next few years due to technical problems, the Cobra was establishing itself as an effective aerial weapons platform, despite its performance shortcomings compared to the AH-56, and design issues of its own. By 1972, when the Cheyenne program was eventually cancelled to make way for the Advanced Attack Helicopter (AAH), the interim AH-1 "Snake" had built a solid reputation as an attack helicopter. In June 1972 the USMC began deploying AH-1J SeaCobra Attack Helicopters for combat operations in South Vietnam.
During the late 1970s the U.S. Army saw the need of more sophistication within the attack helicopter corps, allowing them to operate in all weather conditions. With that the Advanced Attack Helicopter program was started. From this program the Hughes YAH-64 came out as the winner. The prototype YAH-64 was first flown on 30 September 1975. The U.S. Army selected the YAH-64 over the Bell YAH-63 in 1976, and later approved full production in 1982. After purchasing Hughes Helicopters in 1984, McDonnell Douglas continued AH-64 production and development. The helicopter was introduced to U.S. Army service in April 1986.
Today, the US attack helicopter has been further refined, and the AH-64D Apache Longbow demonstrates many of the advanced technologies being considered for deployment on future gunships. The US Marine Corps also continued to employ attack helicopters in the direct fire support role, in the form of the AH-1 Super Cobra. While helicopters were effective tank-killers in the Middle East, attack helicopters are being seen more in a multipurpose role. Tactics, such as tank plinking, showed that fixed-wing aircraft could be effective against tanks, but helicopters retained a unique low-altitude, low-speed capability for close air support. Other purpose-built helicopters were developed for special operations missions, including the MH-6 for extremely close support.
Soviet Union and its successor states
During the early 1960s, Soviet engineers started experimenting with various designs aimed at producing an aerial vehicle that can provide battlefield mobility for infantry and provide fire support to army forces on the ground. The first of these concepts was a mock-up unveiled in 1966 in the experimental shop of the Ministry of Aircraft's factory number 329 where Soviet designer, Mikhail Leont'yevich Mil, was head designer. The mock-up, which was designated V-24, was based on another project, the V-22 utility helicopter, which itself never entered production. The V-24 had an infantry transport compartment that could hold eight troops sitting back to back, and a set of small wings positioned to the top rear of the passenger cabin, capable of holding up to six missiles or rocket pods and a twin-barrel GSh-23L cannon fixed to the landing skid.
These designs were proposed by Mil to the Soviet armed forces, and while he had the support of a number of strategists, he was opposed by several more senior members of the armed forces who believed that conventional weapons were a better use of resources. Despite the opposition, Mil managed to persuade the defence minister's first deputy, Marshal Andrey A. Grechko, to convene an expert panel to look into the matter. While the panel's opinions were mixed, supporters of the project eventually held sway and a request for design proposals for a battlefield support helicopter was issued.
The development of gunships and attack helicopters by the US Army during the Vietnam War convinced the Soviets of the advantages of armed helicopter ground support doctrine, which had a positive influence on moving forward with the development of the Mil Mi-24. After several mock-ups were produced, a directive was issued on 6 May 1968 to proceed with development of a twin-engine design of the helicopter. Work proceeded under Mil until his death in 1970. Detailed design work began in August 1968 under the codename Yellow 24. A full scale mock-up of the design was reviewed and approved in February 1969. Flight tests with a prototype began on 15 September 1969 with a tethered hover, and four days later the first free flight was conducted. A second prototype was built, followed by a test batch of ten helicopters. A number of other design changes were made until the production version Mi-24A entered production in 1970, obtaining its initial operating capability in 1971 and was officially accepted into the state arsenal in 1972.
In 1972, following completion of the Mi-24, development began on a unique attack helicopter with transport capability. The new design had a reduced transport capability (3 troops instead of 8) and was called the Mil Mi-28, and that of the Ka-50 attack helicopter, which is smaller and more maneuverable and does not have the large cabin for carrying troops.
In 1977, a preliminary design of the Mil Mi-28 was chosen, in a classic single-rotor layout. Its transport capability was removed and it lost its similarity to the Mi-24. Design work on the Mi-28 began under Marat Tishchenko in 1980. In 1981, a design and a mock-up were accepted. The prototype (no. 012) was first flown on 10 November 1982. In this same time frame, Kamov was also attempting to submit its own designs for a new helicopter to the military, which they had designed throughout the early and mid 1980s. In 1984, the Mi-28 completed the first stage of state trials, but in October 1984 the Soviet Air Force chose the more advanced Kamov Ka-50 as the new anti-tank helicopter. The Mi-28 development was continued, but given lower priority. In December 1987 Mi-28 production in Rosvertol in Rostov on Don was approved. After several prototypes were built, production ceased in 1993 with additional development continuing into the 21st century. Changes in the military situation after the Cold War made specialized anti-tank helicopters less useful. The advantages of the Mi-28N, like all-weather action ability, lower cost, and similarity to the Mi-24, have become more important. In 2003, the head of Russian Air Force stated that the Mi-28N and Ka-50 attack helicopters will become the standard Russian attack helicopter. The first serial Mi-28N was delivered to the Army on 5 June 2006.
People's Republic of China
In 1979, the Chinese military studied the problem of countering large armor formations. It concluded that the best conventional solution was to use attack helicopters. Eight Aérospatiale Gazelle armed with Euromissile HOT were procured for evaluation. By the mid-1980s, the Chinese decided a dedicated attack helicopter was required. At the time, they used civilian helicopters converted for the military; these were no longer adequate in the attack role, and suitable only as scouts. Following this, China evaluated the Agusta A129 Mangusta, and in 1988 secured an agreement with the USA to purchase AH-1 Cobras and a license to produce BGM-71 TOW missiles; the latter was cancelled following the Tiananmen Square protests of 1989 and the resulting arms embargo. The color revolutions prevented the purchase of attack helicopters from Eastern Europe in 1990 and 1991; Bulgaria and Russia rejected Chinese offers to purchase the Mil Mi-24.
While attempting to import foreign designs failed, war games determined that attack helicopters had to be commanded by the army, rather than the air force. This led to the formation of the People's Liberation Army Ground Force Aircraft (PLAGFAF), with an initial strength of 9 Harbin Z-9s. The PLAGFAF conducted tactical experiments that would help define the future Z-10's requirements. Research also decided that anti-tank missiles like the BGM-71 TOW were inadequate, and favored an analogue to the AGM-114 Hellfire.
The Gulf War highlighted the urgent need for attack helicopters, and revalidated the assessment that a purpose-built design was needed. (At the time, the Chinese military depended on armed utility helicopters such as the Changhe Z-11 and Harbin Z-9.) Also, it demonstrated that the new attack helicopter would need to be able to defend itself against other helicopters and aircraft. The military perceived that once the new attack helicopter entered service, the existing helicopters would be used as scouts.
The Armed Helicopter Developmental Work Team (武装直升机开发工作小组) was formed to develop a new medium helicopter design, as opposed to basing the new design on the light helicopters then in service. The 602nd and 608th Research Institutes started development of the 6-ton class China Medium Helicopter (CHM) program in 1994. The program was promoted as a civilian project, and was able to secure significant Western technical assistance, such as from Eurocopter (rotor installation design consultancy), Pratt & Whitney Canada (PT6C turboshaft engine) and Agusta Westland (transmission). The Chinese concentrated on areas where it could not obtain foreign help. The 602nd Research Institute's called its proposed armed helicopter design the WZ-10 (Wu Zhi (武直)-10).
The 602nd Research Institute was assigned as the chief designer, while Harbin Aircraft Manufacturing Corporation (HAMC) of China Aviation Industry Corporation II (AVIC II) was assigned as the primary manufacturer. Nearly four dozen other establishments participated in the program. According to Chinese sources, the initial test flights were concluded on December 17, 2003, whereas according to other sources they were completed nine months earlier in March 2003. According to Jane's Information Group, a total of 3 prototypes had completed over 400 hours of test flights by this time. By 2004, 3 more prototypes were built, for a total of 6, and a second stage of test flights were concluded on December 15, 2004. In one of the test flights the future commander-in-chief of the People's Liberation Army Ground Force Air Force (PLAGAF), Song Xiangsheng (宋湘生), was on board the prototype. A third stage of intensive test flights followed, taking place during both day and night. By January 2006 weaponry and sensor tests, including firing of live ammunition, had taken place. The helicopter was introduced to the general public in December 2010 and subsequently entered service with the People's Liberation Army.
France, Germany and Spain
In 1984, the French and West German governments issued a requirement for an advanced multirole battlefield helicopter. A joint venture consisting of Aérospatiale and MBB was subsequently chosen as the preferred supplier. According to statements by the French Defence Minister André Giraud in April 1986, the collaborative effort had become more expensive than an individual national programme and was forecast to take longer to complete as well. In July 1986, a government report into the project alleged that the development had become distanced from the requirements and preferences of the military customers the Tiger was being developed for.
Both France and Germany reorganised the programme. Thomson CSF also took over the majority of the Tiger's electronic development work, such as the visual systems and sensors. Despite the early development problems and the political uncertainty between 1984 and 1986, the program was formally relaunched in November 1987; it was at this point that a greater emphasis on the attack helicopter's anti-tank capabilities came about. Much of the project's organisational framework was rapidly redeveloped between 1987 and 1989; such as the installation of a Franco-German Helicopter Office to act as a program executive agency in May 1989.
Due to the end of the Cold War and subsequent defence budgets decreases in the 1990s, financial pressures led to further questions regarding the necessity for the entire program. In 1992, Aérospatiale and MBB, among other companies, merged to form the Eurocopter Group; this led to considerable consolidation of the aerospace industry and the Tiger project itself. A major agreement was struck in December 1996 between France and Germany that cemented the Tiger's prospects and committed the development of supporting elements, such as a series of new generation missile designs for use by the new combat helicopter.
On 18 June 1999, both Germany and France publicly placed orders for an initial batch of 160 Tiger helicopters, 80 for each nation, valued at €3.3 billion. On 22 March 2002, the first production Tiger was rolled out in a large ceremony held at Eurocopter's Donauworth factory; although production models began initial acceptance trials in 2003, the first official delivery to the French Army took place on 18 March 2005; the first official Tiger delivery to the Germany followed on 6 April 2005. Germany reduced its order to 57 in March 2013. In 2008 OCCAR estimated the project cost at €7.3 billion. France's FY2012 budget put their share of the project at €6.3bn (~US$8.5bn), implying a programme cost of €14.5bn (~US$19.5bn) to the three main partners. At FY2012 prices, their 40 HAP cost €27m/unit (~US$36m) and their 40 HAD €35.6m/unit (~US$48m), including development costs the French Tigers cost €78.8m (~US$106m) each.
The Indian Army deploys the Mil Mi-35 and HAL Rudra as of 2014. During the Kargil War in 1999, the Indian Air Force and the Indian Army found that there was a need for helicopters that can operate at such high-altitude conditions with ease. Limitations from operating with high payloads and restricted maneuverability of Mil Mi-35 led India to the develop the HAL Light Combat Helicopter and HAL Rudra for multi-role high-altitude combat operations. These helicopters will be used by the Indian Air Force and the Indian Army's Aviation Corps.
In 1972, the Italian Army began forming a requirement for a light observation and anti-tank helicopter. Agusta had initially studied the development of a combat-orientated derivative of their existing A109 helicopter, however they decided to proceed with the development of a more ambitious helicopter design. In 1978, Agusta formally began the design process on what would become the Agusta A129 Mangusta. On 11 September 1983, the first of five A129 prototypes made the type's maiden flight; the fifth prototype would first fly in March 1986. The Italian Army placed an order for a total of 60 A129s.
The Rooivalk project began in early 1984 under the auspices of the Atlas Aircraft Corporation, a predecessor of Denel Aviation. Faced with the increasingly conventional nature of the South African Border War, the South African Defence Force recognised the need for a dedicated attack helicopter and accordingly set along the process of developing a suitable aircraft.
The Atlas XH-1 Alpha was the first prototype to emerge from the program. It was developed from an Aérospatiale Alouette III airframe, retaining that helicopter's engine and dynamic components, but replacing the original cockpit with a stepped tandem one, adding a 20 mm cannon on the nose and converting the undercarriage to tail-dragger configuration. The XH-1 first flew on 3 February 1985. The results were ultimately good enough to convince Atlas and the SAAF that the concept was feasible, opening the door for the development of the Rooivalk.
During the Rooivalk's development it was decided to base the aircraft on the dynamic components of the Aérospatiale Super Puma, a larger and more powerful helicopter. These components were already used on the Atlas Oryx, a local upgrade and modification of the Aérospatiale Puma.
Unfortunately the development of the Rooivalk continued until after the conclusion of the South African Border War and defence budgets were slashed due to parliamentary changes to the requirements of the national air force. This resulted in an extensive development and production period beginning in 1990 until 2007, during which 12 aircraft were produced for use by the South African Air Force. These aircraft were subsequently upgraded to the Block 1F standard by 2011. The upgrade involves improved targeting systems and other avionics which enable the helicopter to use guided missiles for the first time. The Mokopa ATGM was qualified as part of the upgrade process. Gearbox components were improved and cooling problems with the F2 20 mm cannon were also addressed.
On 1 April 2011, the South African Air Force received the first five of eleven (one of the twelve aircraft originally delivered to the SAAF was written off after an accident) Block 1F upgraded Rooivalk. The ninth and tenth Rooivalk attack helicopters were delivered in September 2012 following their upgrade to the Block 1F initial operating standard. The eleventh and final Rooivalk was delivered on 13 March 2013.
The 1990s could be seen as the coming-of-age for the U.S. attack helicopter. The AH-64 Apache was used extensively during Operation Desert Storm with great success. Apaches fired the first shots of the war, destroying enemy early warning radar and SAM sites with their Hellfire missiles. They were later used successfully in both of their operational roles, to direct attack against enemy armor and as aerial artillery in support of ground troops. Hellfire missile and cannon attacks by Apache helicopters destroyed many enemy tanks and armored cars.
The "deep attack" role of independently operating attack helicopters came into question after a failed mission, during the 2003 Gulf War attack on the Karbala Gap. A second mission in the same area, four days later, but coordinated with artillery and fixed-wing aircraft, was far more successful with minimal losses.
In 2011, France and Britain sent Eurocopter Tiger and AgustaWestland Apache attack helicopters to Libya. The primary objective of the 2011 military intervention was to protect civilians in accordance with UN Security Council Resolution 1973. Within days of the Apaches deployment, it had completed a variety of tasks such as destroying tanks, checkpoints held by pro-Gaddafi forces and vehicles carrying ammunitions loyal to Muammar Gaddafi. The attack helicopters were reported to be far more effective than the fighter jets which had previously been given the task of completing the aforementioned tasks.
In 2013, the South African National Defence Force announced that it would deploy Denel Rooivalk attack helicopters to the Democratic Republic of the Congo to support the United Nations Organization Stabilization Mission in the Democratic Republic of the Congo. This was the first combat deployment for the helicopter. Three helicopters from 16 Squadron SAAF were deployed to the region and since November 2013 it was involved in heavy fighting alongside the United Nations Force Intervention Brigade, against rebels operating in North Kivu, in particular the M23 militia, which consisted of hardened former government troops equipped with relatively heavy weaponry such as main battle tanks and anti-aircraft weaponry. During its first ever combat mission it proved to be instrumental in routing the rebels from their hilltop strongholds during an offensive by the United Nations Force Intervention Brigade and the Military of the Democratic Republic of the Congo.
Modern examples include:
- AgustaWestland AW129
- Bell AH-1 Cobra
- Boeing AH-64 Apache
- CAIC WZ-10
- Denel Rooivalk
- // Eurocopter Tiger
- HAL Light Combat Helicopter
- Harbin Z-19
- Kamov Ka-50/Ka-52
- / Mil Mi-24 "Hind"
- Mil Mi-28
|Helicopter||First Flight||Length||Rotor diameter||Height||Empty weight||Power|
|Agusta A129 Mangusta||1983||12.3 m (40 ft)||11.9 m (39 ft)||3.4 m (11.2 ft)||2,500 kg (5,500 lb)||2×664 kW (890 shp)|
|/ TAI/AW T-129||2009||13.45 m (44 ft)||11.9 m (39 ft)||3.45 m (11.3 ft)||2,900 kg (6,400 lb)||2×1,014 kW (1,360 shp)|
|Bell AH-1G Cobra||1966||16.2 m (53 ft)||13.4 m (44 ft)||4.1 m (13.5 ft)||2,600 kg (5,700 lb)||1×820 kW (1,100 shp)|
|Bell AH-1Z Viper||2000||17.8 m (58 ft)||14.6 m (48 ft)||4.1 m (13.5 ft)||5,600 kg (12,300 lb)||2×1,340 kW (1,800 shp)|
|Boeing AH-64 Apache||1975||17.7 m (58 ft)||14.6 m (48 ft)||3.9 m (12.8 ft)||5,200 kg (11,500 lb)||2×1,490 kW (2,000 shp)|
|Denel Rooivalk||1990||18.7 m (61 ft)||15.6 m (51 ft)||5.2 m (17.1 ft)||5,700 kg (12,600 lb)||2×1,420 kW (1,900 shp)|
|// Eurocopter Tiger||1991||14.0 m (46 ft)||13.0 m (43 ft)||3.8 m (12.5 ft)||3,100 kg (6,800 lb)||2×873 kW (1,170 shp)|
|HAL-LCH||2010||15.8 m (52 ft)||13.3 m (44 ft)||4.7 m (15.4 ft)||2,250 kg (5,000 lb)||2×1,067 kW (1,430 shp)|
|/ Kamov Ka-50/-52||1982 (Ka-50)||16.0 m (52 ft)||14.5 m (48 ft)||4.9 m (16.1 ft)||7,700 kg (17,000 lb)||2×1,641 kW (2,200 shp)|
|Mil Mi-24||1969||17.5 m (57 ft)||17.3 m (57 ft)||6.5 m (21.3 ft)||8,500 kg (18,700 lb)||2×1,600 kW (2,150 shp)|
|Mil Mi-28||1982||17.0 m (56 ft)||17.2 m (56 ft)||4.7 m (15.4 ft)||8,600 kg (19,000 lb)||2×1,636 kW (2,190 shp)|
|Helicopter||Max. Speed||Cruise Speed||Range||Ceiling||Rate of Climb|
|Agusta A129 Mangusta||280 km/h (170 mph)||230 km/h (140 mph)||510 km (320 mi; 280 nmi)||4,700 m (15,000 ft)||10.2 m/s (33 ft/s)|
|/ TAI/AW T-129||315 km/h (200 mph)||270 km/h (170 mph)||561 km (350 mi; 300 nmi)||6,096 m (20,000 ft)||14 m/s (46 ft/s)|
|Bell AH-1G Cobra||230 km/h (140 mph)||570 km (350 mi; 310 nmi)||3,500 m (11,000 ft)||6.3 m/s (21 ft/s)|
|Bell AH-1Z Viper||410 km/h (250 mph)||300 km/h (190 mph)||690 km (430 mi; 370 nmi)||6,100 m (20,000 ft)||14.2 m/s (47 ft/s)|
|Boeing AH-64 Apache||290 km/h (180 mph)||270 km/h (170 mph)||480 km (300 mi; 260 nmi)||6,400 m (21,000 ft)||12.7 m/s (42 ft/s)|
|CAIC WZ-10||300 km/h (190 mph)||270 km/h (170 mph)||800 km (500 mi; 430 nmi)||6,400 m (21,000 ft)||10.2 m/s (33 ft/s)|
|Denel Rooivalk||310 km/h (190 mph)||280 km/h (170 mph)||740 km (460 mi; 400 nmi)||6,100 m (20,000 ft)||13.3 m/s (44 ft/s)|
|// Eurocopter Tiger||290 km/h (180 mph)||260 km/h (160 mph)||800 km (500 mi; 430 nmi)||4,000 m (13,000 ft)||10.7 m/s (35 ft/s)|
|HAL-LCH||330 km/h (210 mph)||260 km/h (160 mph)||700 km (430 mi; 380 nmi)||6,500 m (21,000 ft)||12.0 m/s (39 ft/s)|
|/ Kamov Ka-50/-52||315 km/h (200 mph)||270 km/h (170 mph)||550 km (340 mi; 300 nmi)||5,500 m (18,000 ft)||10.0 m/s (33 ft/s)|
|Mil Mi-24||335 km/h (210 mph)||450 km (280 mi; 240 nmi)||4,500 m (15,000 ft)|
|Mil Mi-28||320 km/h (200 mph)||270 km/h (170 mph)||440 km (270 mi; 240 nmi)||5,700 m (19,000 ft)||13.6 m/s (45 ft/s)|
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