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On Oct. 31, 1978, the now iconic Sikorsky UH-60A Black Hawk first entered U.S. Army service. In the 40 years since, the manufacturer has delivered more than 4,000 of the type across a range of variants, with that fleet collectively logging more than 14 million flight hours. The S-70 has served within every branch of the U.S. armed forces (in which it is designated the H-60), flown for the defence forces of many other nations, and has become an increasingly common sight in civilian colors as it proves its capability in firefighting, policing, search-and-rescue (SAR) and utility roles.
Conceived in 1972 as the YUH-60A, the helicopter was designed to meet the Army’s UTTAS (Utility Tactical Transport Aircraft System) requirements for a twin-engine successor to the Bell UH-1 “Huey.” Designated the “Black Hawk” following the Army’s tradition of naming military helicopters after Native American warriors and tribes, the aircraft would ultimately prove its worth in all five branches of the U.S. armed forces (Army, Navy, Marine Corps, Air Force and Coast Guard), as well as with more than 40 civil and military organizations in more than 30 allied nations.
Throughout the aircraft’s first 40 years, the one constant has been its ongoing evolution, with the current production Black Hawk family — the UH-60M “Mike,” naval MH-60R “Romeo,” and the S-70i built by Sikorsky’s subsidiary PZL Mielec of Poland — vastly more capable than the original versions of the type. Later this year, the new-generation HH-60W “Whiskey” combat SAR (CSAR) will join an expanding portfolio that also includes a new-generation armed Black Hawk and the S-70i Firehawk for aerial wildfire suppression.
Sikorsky’s record production year for the S-70 family was in 2014, when 186 of the type were delivered to U.S. government and foreign customers. In 2018, the company plans to deliver 107 S-70 family models.
With the Army planning to operate the rotorcraft through 2070 (after the future vertical lift joint-multi-role medium rotorcraft enters service), and former military Hawks finding a new lease of life in the civilian sector, the longevity of the Black Hawk family appears assured.
Sikorsky military helicopters
In 1943, the two-seat Sikorsky R-4 became the first military helicopter to enter production, with the U.S. Army Air Force (USAAF) placing an initial order for 29 aircraft. The R-4 was the first helicopter to serve with the USAAF (later USAF), Navy, Coast Guard and the United Kingdom’s Royal Navy and Royal Air Force.
Sikorsky’s military helicopter sales steadily increased after the Second World War, with the debut of the piston-engine S-51, S-52, S-55, S-58 and S-56, and the turbine-powered S-61, S-62, SH-3, HH-3, CH-53 and CH-54.
The Vietnam War was the first American conflict where helicopters were used extensively to move troops and weapons across the battlefield, with almost 12,000 deployed between 1965 and 1975. More than 5,000 of these were destroyed — and the majority of these losses were Bell UH-1 Hueys.
Conceived in the late 1960s to develop a faster, better-armored helicopter, the UTTAS program had extremely demanding requirements for performance, maneuverability, maintainability, reliability and survivability.
The primary mission was to transport a fully-equipped infantry squad of 11 men (weighing 240 pounds/110 kilograms each), plus a gunner, pilot and co-pilot on a two- to three-hour mission at high altitudes (4,000 feet/1,220 meters) and hot temperatures (95 F/35 C). It needed to fly at a minimum cruise speed of 145 knots, climb vertically within the range of 450 feet/140 meters per minute to 550 feet/170 meters per minute at maximum weight, and be able to operate in any likely theater of war.
In addition, the UTTAS had to be capable of transporting four stretcher cases internally, along with medics and medical equipment. It also had to be able to sling a 105-mm howitzer (weighing 8,000 lb./3,630 kg) on its external hook and carry the weapon’s five-man crew and 50 rounds of ammunition.
Many at Sikorsky believed that winning the UTTAS competition was essential for the company’s long-term survival, since most of its U.S. military production contracts were drawing to a close and the Army hadn’t ordered a Sikorsky helicopter since the last CH-54 Tarhe was delivered.
The Army issued its request for proposals for the UTTAS in 1972. It shortlisted Sikorsky and Boeing, with the manufacturers called to produce three prototype YUH-60s and YUH-61s, respectively, to take part in a multi-year fly-off competition.
The prototype YUH-60A first flew on Oct. 17, 1974, powered by a pair of 1,500-shaft-horsepower General Electric T-700 turboshafts specified by the Army. The heart of the UH-60’s versatility was its rotor system — the most efficient such system that Sikorsky had ever developed. It had a fully articulated rotorhead with flexible elastomeric bearings attached to four composite main rotor blades, which had titanium spars.
The Vietnam War had highlighted the need for the next generation of military helicopters to be capable of high-speed nap-of-the-earth (NOE) terrain following to survive modern threats, such as the shoulder-fired surface-to-air missiles carried by Soviet air defenses in Eastern Europe.
It was this that led to one of the Army’s most challenging performance requirements: a 1.75 g turn throughout a forward flight distance of 1,100 feet, followed by a pushover to 0 g while terrain following. It was the UH-60’s rotor that allowed it to perform this exacting maneuver.
The low disk loading of the rotor also provided the UH-60 with good autorotation characteristics, and it was significantly quieter than the Huey system, which was audible six miles (10 kilometers) away.
A variable incidence horizontal stabilator was later added to production aircraft to optimize the fuselage attitude for various cruise speeds. Another technological innovation was a bearingless cross-beam tail rotor. Spanning a diameter of 11 feet, it was canted by 20 degrees to produce 400 lb. (180 kg) of lift at the tail in normal flight. This design allowed a 14 percent reduction in the size of the main rotor diameter (to 53 feet, 8 inches/16.36 meters) and produced a better center of gravity range, which allowed the passenger cabin to be shifted rearward under the rotor and the fuselage to be shorter than would otherwise have been possible.
Sikorsky also invested a lot of time to meet the Army’s rapid air transport requirement, which sought an aircraft that could easily fit in a cargo aircraft without being disassembled. The UH-60’s key features included the shorter fuselage, a rotor mast that could be lowered, folding main rotor and tail pylon, kneeling main landing gear, and a removable horizontal stabilator.
Because of this, the UH-60A could be prepared and loaded into a cargo aircraft in less than 1.5 hours, and unloaded and test flown in less than 2.5 hours. One UH-60A could fit in a Lockheed C-130 Hercules, the C-141 Starlifter could accommodate two, and six Black Hawks could be carried in a C-5A Galaxy.
Building in combat survivability and crashworthiness also required a lot of innovation. The UH-60A’s airframe and dynamic systems were specifically engineered to protect the aircraft’s occupants from ballistic threats and accidents, with a redundant flight control system, a triple redundant hydraulic and electrical system, and ballistically tolerant cockpit, cabin, rotor blades, drive shafts and critical systems.
The crashworthy features of the aircraft included energy absorbing landing gear and seats that together could withstand an impact at 42 feet per second, a robust airframe that kept high mass components (such as the transmission) retained in 20/20/10 g crash conditions, and self-sealing fuel tanks and lines to reduce the risk of post-accident fires.
The Black Hawk enters service
The UH-60A met the Army’s challenging targets, and was declared the winner of the UTTAS competition on Dec. 23, 1976. It became the first major Army weapon system to be awarded a multi-year production contract in 1981, resulting in tremendous cost savings to Sikorsky and its customers. More than 1,000 UH-60A Black Hawks were delivered to Army and Army National Guard units between 1978 and 1989, on the basis of 15 UH-60As replacing every 23 UH-1s.
To expand the Black Hawk’s capabilities, Sikorsky quickly developed a series of upgrades. The first was a deicing system for the main and tail rotors, followed by countermeasures to reduce the threat of infrared-seeking surface-to-air and air-to-air missiles. The hover infrared suppressor subsystem reduced the aircraft’s engine exhaust signature during all phases of flight by mixing cool air with the exhaust plume.
The battlefield capabilities of the Black Hawk were greatly enhanced when Sikorsky developed the external stores support system (ESSS) for carrying auxiliary fuel tanks and various weapons systems. The ESSS was qualified to carry 5,000 lb. (2,270 kg) per side, including two 450-US gallon (1,700-liter) tanks on the inboard pylons and two 230-US gallon (870-liter) tanks on the outboard pylons, which combined to give the Black Hawk an impressive range of 1,100 nautical miles (1,770 kilometers), allowing it to self-deploy over great distances.
The ESSS was subsequently qualified to carry various weapon systems externally, including the Hellfire, Stinger, Maverick and Sidewinder missiles, and 2.75-inch unguided rocket pods.
The first combat missions for the UH-60A were Operation Urgent Fury in Grenada in 1983 and Operation Just Cause in Panama in 1989. The first large-scale deployment of Black Hawks to the Middle East was during Operation Desert Storm — the first Gulf War in 1991 — when approximately 400 Black Hawks flew more than 44,000 hours between them.
Desert Storm introduced a number of field upgrades, including the enhanced ballistic armored subsystem to protect occupants from small arms fire; blade erosion protection kits designed to protect main and tail rotor blade leading edge surfaces; APU inlet particle separators; the climate heat aircraft protection system to reduce blade and airframe surface temperatures; environmental aircraft protection covers to protect windscreens and avionics bays from heat buildup; and enhanced tactical air navigation and GPS.
Editor’s note: This is part 1 of a 5-part series. Read part 2 here.