Like the Boeing-Vertol YUH-61A, the Sikorsky Model S-70 was developed in response to the Army's 1972 requirement for a simple, robust, and reliable Utility Tactical Transport Aircraft System (UTTAS) helicopter intended to eventually replace most of the Army's UH-1 Iroquois. In August 1972 both Sikorsky and Boeing-Vertol were awarded Army contracts for the production and initial testing of three UTTAS prototypes, the Sikorsky machines (serial numbers 73-21650 through -21652) being designated YUH-60A. The first example made its maiden flight in October 1974, and all three prototypes entered competitive testing against the Boeing-Vertol YUH-61A in March 1975. The YUH-60A was declared the winner of the UTTAS competition in December 1976, and almost immediately thereafter the Army awarded Sikorsky a contract for the first fifteen production UH-60A Blackhawks.

The Blackhawk's general shape and external dimensions were dictated by the Army's requirement that one complete UTTAS helicopter be air transportable within the cargo bay of a single C-130 Hercules (with the additional requirement that two helicopters fit within a single C-141 Starlifter, and six within each C-5 Galaxy). The UH-60 is thus a long and low-set craft with a streamlined pod-and-boom layout, and is characterized by a downward-sloping tail boom fitted with a moving stabilator, a sharply-swept vertical tail, and a four-bladed anti-torque rotor canted twenty degrees off the vertical to produce added lift and thus allow a reduction in the main rotor diameter. The tips o1 each of the Blackhawk's four fully-articulated, high-lift main rotor blades are swept twenty degrees to reduce control loads and the effects of high Mach numbers, and all four blades can be manually folded. The UH-60A can be fitted with an External Stores Support System (ESSS) consisting of two stub wings, one fixed to either side of the central fuselage above and just forward of the main cabin doors. These stub wings can carry auxiliary fuel tanks, electronic countermeasures (ECM) equip-ments, machine gun, cannon or rocket pods, up to sixteen Hellfire anti-tank missiles, or four M-56 landmine dispensers.

The UH-60's design also incorporates a variety of structural features that allow the aircraft to remain in flight after sustaining heavy damage and that provide maximum protection for the crew and passengers in a crash or while under hostile fire. In the Blackhawk these features include an immensely strong yet flexible and crashworthy cabin box, wheeled landing gear able to absorb very heavy vertical impacts, extensive armour plating around the cockpit and dynamic components, self-sealing fuel tanks, widely-separated and redundant electronic and hydraulic systems, and main rotor blades that can withstand hits by explosive or incendiary projectiles up to 23mm in size.

The first production UH-60A was delivered to the Army in 1979, with the aviation components of the 101st and 82nd Airborne Divisions being the first frontline units to transition to the new helicopter. The Army awarded Sikorsky the first of two multi-year Blackhawk construction contracts in early 1982, and by early 1988 more than 900 examples were in Army service in the utility transport, aeromedical evacuation, and special warfare-support roles. The Army also acquired examples of two electronic warfare (EW) Blackhawk variants, designated EH-60A and EH-60B. Development of the former began in October 1980 when Sikorsky was awarded an Army contract to modify one UH-60A (probably 79-23301) for evaluation under the Quick Fix II EW programme. The modifications included preparation of the airframe for later installation of the AN/ALQ-151 multi-role tactical EW system, the addition of four dipole antennae mounted in pairs on either side of the tailboom, and the installation of a deployable whip antenna beneath the aft section of the main cabin. The EH-60A was also equipped with the AN/ALQ-144 infrared countermeasures set and flare/chaff dispensers in addition to the standard AN/APR-39(V)1 radar warning receiver. The YEH-60A EW Blackhawk flew for the first time in September 1981, and in October 1984 the Tracor Aerospace Group won an Army contract for the conversion of forty UH-60A to EH-60A standard. Flight testing of a planned 132 production -A model EW Blackhawks began in April 1986, though budget restraints ultimately led the Army to acquire only 66 production machines. The last of these was delivered in September 1989, and soon afterwards the type's designation was changed from EH-60A to EH-60C.

While the EH-60C is intended to locate, classify and disrupt enemy signals traffic, the EH-60B was developed specifically to carry the Stand-Off Target Acquisition System (SOTAS) radar. The EH-60B was characterized by the long box-shaped SOTAS scanner mounted below the main cabin, and was equipped with backward-retracting main landing gear legs to allow the SOTAS antenna to rotate a full 360 degrees in flight. The sole EH-60B prototype made its maiden flight in February 1981, but the SOTAS development programme was cancelled the following September and the aircraft was subsequently converted to EH-60A/C standard.

The UH-60A underwent its baptism of fire during the 1983 U.S. invasion of Grenada, and there proved itself to be a dependable and capable successor to the Huey. The Blackhawks deployed to Grenada were fired upon by weapons ranging from small arms to 23mm cannon, and in the Army's official report on the conflict the craft's sturdy construction, mechanical reliability, and ability to absorb significant damage and still fly were singled out for special mention.

Further development of the UH-60 continues as the manu-facturer seeks to improve the basic airframe and the Army works to adapt the Blackhawk to a wider variety of operational tasks. In January 1988 the Army accepted the first of nine UH-60A machines especially equipped for use by the commanders-in-chief (CINCs) of various Army commands. These 'CINC Hawks' are fitted with additional radio equipment, satellite communications gear, M-130 flare and chaff dispensers, and other airborne survivability equipment. And in September 1987 Sikorsky submitted a proposal for a Blackhawk derivative intended specifically to support the Army's special operations forces. This aircraft, the MH-60K, will feature a long-range fuel system incorporating both additional internal tankage and the pylon-mounted auxiliary fuel tanks of the Air Force HH-60 combat rescue helicopter, and will have uprated engines, a 'glass' cockpit built around multiple CRT displays, advanced communi-cations and navigation equipment, Forward-Looking Infrared Radar (FLIR), an air-to-air refuelling probe, heavier defensive armament, and additional troop seating. Sikorsky has announced its intention to begin flight testing the MH-60K in early 1989, and current Army planning calls for the acquisition of up to twenty-one aircraft. And in the summer of 1986 Sikorsky began preliminary design work on what was originally called a B-model Blackhawk incorporating an advanced composite main rotor system with larger-diameter blades, more powerful engines, the stronger gearbox developed for the Navy's SH-60B Seahawk variant, a redesigned nose intended to improve pilot visibility, a modified cockpit with improved instrumentation, and upgraded electronics. By late 1988 this aircraft had entered the final design definition stage with the designation UH-60M.

S.Harding "U.S.Army Aircraft since 1947", 1990

Designed for the US Army's UTTAS (Utility Tactical Transport Aircraft System) programme, the Sikorsky S-70 was intended as a replacement for the Bell UH-1 and as such had to be capable of carrying an 11-man infantry squad and its equipment. The first example was flown in YUH-60A prototype form on 17 October 1974 and was selected as the winner of the design competition, trumping the Bell 240 and Boeing Vertol 179, on 23 December 1976. This victory was vital to the continued financial well-being of Sikorsky, as the projected order of 1,107 UTTAS helicopters, beginning in 1978, would revive its falling order book. The first production contract covered 15 UH-60A Black Hawk helicopters; a further 353 were the subject of a fixed-price option, and an April 1982 contract covered the acquisition of 294 more for delivery up to 1985.

Powered by two 1163kW General Electric T700-GE-700 turboshaft engines, the first production UH-60A flew on 17 October 1978, and entered service with the 101st Airborne Division (Air Assault) in June the following year. It soon proved far superior to the UH-1H, able to carry loads of up to 20 and to cope with external loads of up to 2000kg. With the addition of External Stores Support System (ESSS) pylons the UH-60A can carry stores such as Hellfire missiles and long-range fuel tanks on pylons, and M60 machine-guns in the forward area of the cabin. The US Army has introduced a plethora of versions into service for assault, Medevac, electronic warfare and special operations, all of which are detailed in the variants list below.

When the US Navy's LAMPS (Light Airborne Multi-Purpose System) programme required a helicopter with a capability superior to that of the Kaman Seasprite that won the LAMPS Mk I contract, substantial commonality with the UH-60A meant that significant economies could result from selection of the navalised S-70L, the SH-60B Seahawk. This version has chin-mounted surveillance radar, ESM (electronic support measures) equipment, a starboard-side pylon for MAD (magnetic anomaly detection) equipment, a sonobuoy launcher, automatic rotor folding, tail pylon folding and modified landing gear. The first of five prototypes flew on 12 December 1979, followed by the first production aircraft on 11 February 1983; initial deliveries were made on 24 March. The first US Navy unit to deploy operationally was HSL-41 at North Island, San Diego, California. The SH-60B will operate from frigates and destroyers, while the SH-60F derivative now entering service is an SH-3H Sea King replacement. By 1993 a total of 1,816 H-60/S-70s had been built for customers in 20 nations.

VARIANTS

YUH-60A: three prototypes entered for UTTAS competition with a further three built after Sikorsky had won; extensively modified during test flights resulting in new tail shape, upper fuselage fairing, cabin windows, and rotor shaft

UH-60A: initial production version of Black Hawk assault transport for US Army; manually folding tail boom for C-130 transport; steadily improved over the years through the addition of a rescue hoist, ESSS provision from the 431st production aircraft (retrofitted), M60D machine-guns replaced by M134 Miniguns, infra-red suppresses fitted to exhausts, wire strike protection above cockpit, accident data recorder, Tracor AN/ARN-148 Omega navigation system, satellite communications transceiver and GPS also added; in use with US Customs service as UH-60A 'Pot Hawk' for anti-drug surveillance; delivered to Bahrain Amiri Air Arm, Fuerza Aerea Colombiana, Philippine air force and Royal Saudi land forces; 'Credible Hawk' UH-60As delivered to USAF in mid-1980s as initial combat rescue version to replace HH-3s with ARRS; detail differences from Army Black Hawks include much of the equipment later added to Army UH-60As; 11 'Credible Hawks' ordered initially, and subsequent procurement and upgrade programme repeatedly cut back

GUH-60A: non-flyable instructional airframes

JUH-60A: aircraft temporarily detached for test purposes

EH-60A: as part of the US Army's Special Electronics Mission Aircraft programme, TRW equipped a single

YEH-60A with Quick Fix IIB emitter location gear and associated antennas; funding allocated for 40 aircraft, later designated EH-60C

HH-60A: single development aircraft for USAF HH-60D

MH-60A: 30 UH-60As modified for special operations use pending the delivery of the dedicated MH-60A; nicknamed 'Velcro Hawk' due to the haphazard addition of equipment; now withdrawn from all active-duty units, bar the Oklahoma Air National Guard, and replaced by MH-60L

VH-60A: initial designation for nine USMC VIP aircraft, later allocated VH-60N designation

UH-60B: Sikorsky designation for an improved Army transport version of the Black Hawk with a CRT cockpit, improved engines and other new features; most of these elements were included in the UH-60L

YEH-60B: UH-60A modified for a proposed Stand-Off Target Acquisition System with an underslung rotating sensor in a canoe faring; first flown on 6 February 1981, but proposed acquisition of 78 aircraft abandoned to provide funding for J-STARS

YSH-60B: five Seahawk prototypes for US Navy to fulfill LAMPS Mk III requirement

SH-60B: production ASW Seahawk for US Navy; fitted with RAST probe, 25-tube sonobuoy launcher, towed MAD bird on stub wing to port, AN/APS-142 radar, ALQ-142 ESM system under nose, single-piece pilot's windscreen, folding tailboom; primary armament two Mk 46 torpedoes; aircraft subject to phased upgrade programme involving addition of new weapons capability and avionics

EH-60C: production Quick Fix II-equipped aircraft designed to locate and jam enemy radio transmissions; fitted with antenna array on tailboom and folding whip aerial under fuselage; plans to acquire 130 EH-60Cs later cut to 66

CH-60E: proposed Marine Corps troop-carrying version, not proceeded with as Corps squad size too great for cabin

HH-60D: 'Night Hawk' combat rescue version for USAF, fitted with NVG-compatible cockpit, refuelling probe, ESSS provision, IR jammer, HIRSS exhaust suppressor, rotor de-icing, colour weather radar; subsequently fell victim to procurement cuts and only one development aircraft completed, later used in HH-60A development

HH-60E: proposed reduced specification HH-60D for USAF; not proceeded with in favour of HH-60A

HH-60G: initially designated MH-60G, HH-60G aircraft at first not fitted with full MH-60G special operations equipment but optimised for SAR instead; subject to upgrade when funds allow

SH-60F: dubbed 'Ocean Hawk', the SH-60F provides inner ASW screening for US carrier battle groups; less heavily equipped than SH-60B

MH-60G: 'Pave Hawk' full-specification combat rescue/special operations aircraft for USAF, converted from existing aircraft; fitted with Bendix colour weather radar, Doppler navig-ation, GPS, INS, moving map display, new HF, VHF and satellite comms, IR jammer, threat-warning system, chaff/flare dispensers, FLIR, refuelling probe, IR strobes, ESSS, HUD, digital databus and additional guns; first MH-6OGs delivered to 55th SOS in December 1987 and all aircraft subject to a rolling modification programme to reach full capability

HH-60H: 'Rescue Hawk' combat rescue/special operations version for US Navy

HH-60J: Jayhawk, ordered by USCG as a replacement for HH-3F on SAR duties

UH-60J: replaced KV-107s in Japan Air Self-Defence Force service and S-61As of the Japan Maritime Self-Defence Force; essentially a Sikorsky S-70A-12 (UH-60L), they differ from US aircraft in being optimised for rescue missions; equipped with rescue winch to starboard, external fuel tanks, Japanese avionics and weather radar, turret-mounted FLIR; first aircraft built by Sikorsky, two more assembled by Mitsubishi which will build the remaining 26 on order entirely in Japan; operational from March 1992

MH-60K: Army special operations version similar to Air Force MH-60G but equipped to a higher standard from the outset; fitted with Texas Instruments FLIR, night vision imaging system, moving map display, OBOGS, T700-GE-701C engines, main rotor brake, and a comprehensive self-defence suite including missile plume detector, radar warning receiver, chaff and flare dispenser, IR jammer, radio jammer and laser warning receiver; prototype flew on 10 August 1990 and the first of 22 currently funded aircraft was delivered in spring 1992; 38 further MH-60Ks are required for Army and ANG units

UH-60L: improvements to UH-60As saw the basic weight of the aircraft increased by 25%; to remedy this situation Sikorsky developed the T700-210C-powered UH-60L which became the standard production transport version for the US Army from October 1989; 190 aircraft ordered, with modifications being retrofitted to UH-60As

MH-60L: UH-60Ls temporarily modified for special operations duties with US Army; replaced stop-gap MH-60As, and referred to as 'Velcro Hawks'; transferred to Reserve units after their replacement by MH-60Ks

VH-60N: 'Presidential Hawk' VIP transports delivered to HMX-1 at MCAS Quantico, originally as VH-60A; fitted with weather radar, extra sound-proofing and VIP cabin, shrouded exhausts, and extensive avionics and communications improvements

UH-60P: 100 UH-60Ls ordered by the Republic of Korea Army, with improved gearbox and main rotor brake; first Sikorsky-built aircraft handed over on 10 December 1990; the next 19 assembled from CKDs, with a further 80 to be built by Korean Air

UH-60Q: 'Dustoff Hawk', Medevac version utilising UH-60L airframe, with purpose-designed medical interior

S-70A: bulk of export Black Hawks delivered using civilian designation with numerical suffix allocated to each customer; deliveries made to Saudi Arabia, Philippines, Thailand, Australia, Jordan, Japan, Brunei, Turkey, Korea, Egypt, Mexico, Hong Kong, Morocco, and Rolls-Royce/Westland in the UK; Royal Saudi land forces received 21 S-70A-1 Desert Hawks and a further eight S-70A-L1 Medevac versions, all optimised for desert operations; 39 S-70A-9s were delivered to the Royal Australian Air Force, with a further 38 assembled by Hawker de Havilland in Bankstown, NSW

S-70B-6: ASW version for Greece, to be delivered commencing in 1995

S-70C: designation allocated to civilian versions of Black Hawk; applied to VIP-configured Brunei aircraft and also to Black Hawks and Seahawks for Republic of China, to circumvent restrictions on 'military' exports

S-70C(M)-1: Thunder-hawk, essentially SH-60F standard aircraft delivered to Republic of China navy from 1993 onwards

WS-70: S-70/UH-60 built under licence by Westland Helicopters in UK; offered in anticipation of RAF requirement to replace Wessex and Puma transport helicopters

D.Donald "The Complete Encyclopedia of World Aircraft", 1997

- The original UH-60A prototype first flew on 17 October 1974.

- Black Hawks entered service with the 101st Airborne Division in 1979.

- Though the US Marine Corps has not adopted the UH-60, they fly nine VH-60N presidential transport helicopters.

- Black Hawks moved more than a million soldiers during the Gulf War.

- In a tragic 'friendly fire' mishap, F-15 fighters shot down two US Army UH-60s in Iraq on 14 April 1994, killing 26.

- The Army is developing a UH-60Q medical evacuation model of the Black Hawk.