Sikorsky S-70 (the second name is UH-60 Black Hawk) – a multi-purpose helicopter, which was intended as a replacement for the Bell UH-1, was able to carry 11 military personnel in night outfit.
The beginning of the development of this helicopter dates back to 1966, along with the launch of the Utility Tactical Transport Air System (UTTAS) program. The US government has presented the leading helicopter companies Boeing-Vertol, Bell, Sikorsky, and Lockheed the technical requirements for the construction of a new multifunctional helicopter UTTAS. The new device was to replace the outdated at that time multi-purpose Bell UH-1 and transport CH-46 Sea Knight, which were in service with various parts of the country’s air force.
In 1971, the UTTAS program, which was the development of a multi-purpose helicopter for the various needs of the Air Force, was approved. According to its requirements, the new apparatus was required to carry from 11 to 15 personnel of the military personnel in the rifle compartment, have a crew of three, be equipped with a twin-engine power plant, and ensure that it can be transported assembled by Lockheed S-141 and S-130 aircraft.
The UTTAS program has become the most expensive in the history of American helicopter engineering. In 1972, an order was received for the production under this program of 1,100 machines that were planned to be manufactured before 1985. The initial cost of UTTAS, including the costs of the purchase and further operation of multi-purpose helicopters, was initially estimated at $ 2.7 billion, then this figure increased to $ 6,5 billion. The cost of one copy also increased from $ 2 to $ 5.8 million.
At the first stage of the competition, representatives of the US Air Force eliminated seven of the nine firms, leaving Sikorsky and Boeing-Vertol, which were allowed to collect test samples of the helicopter. The first contracts were concluded for the assembly of three devices for flight tests and one for static ground. After the final determination of the manufacturer, another contract for 5 machines must be concluded to continue the test cycle.
Each manufacturer at this stage was allocated an amount of $ 61 million.
As part of the UTTAS program, Sikorsky introduced the YUH-60 prototype and the Boeing-Vertol introduced the YUH-61. The first flight of the experimental YUH-60 took place on 10/17/1976 after passing a series of flight and static tests. Sikorsky was recognized as the winner of the competition and immediately offered her a contract to build the first series of helicopters of 15 units, which were called UH-60A.
The main criteria that influenced the choice in favor of the Sikorsky UH-60A are lower operating costs and a lower technical risk of using a helicopter.
Sikorsky UH-60 has become the basis for creating several modifications of helicopters for various purposes. The program for their production was first expanded to 1434 units, and then to 2127 units. The average price of one helicopter was $ 7.25 million. In the early summer of 1994, the 2000th machine of the N-60 line rolled off the assembly line. At that time 1295 helicopters of this family were put into service with the army, 78 were transferred to the Air Force and 207 were exported to 21 countries of the world.
The Sikorsky S-70 helicopter is built on a single-rotor scheme with two gas turbine engines, a tail rotor, and a three-leg landing gear type.
The fuselage is designed as a semi-monocoque, is an all-metal construction. The material of the fuselage structure is mainly used light metal alloys. Composite materials (fiberglass, Kevlar) were used in the construction of the control cabin, doors, lantern, hood, and cowlings of engines.
You can get inside the double crew cabin through the resettable side doors. The crew cabin is equipped with armored seats. The dimensions of the cargo compartment are 4.95 x 2.21 x 1.87 m, volume – 11.6 m³. On both sides of the cabin, doors are measuring 1.5 x 1.75 m. Ten cargo paratroopers or six wounded with a stretcher can be placed inside the cargo compartment.
At the rear, the fuselage goes into the tail boom in the form of a monocoque, which has an asymmetric profile, and an end beam bent upwards with a stabilizer and tail rotor attached to it. The direct stabilizer, controlled, has a span of 4.37 m. The stabilizer installation angle is changed using the control system, which receives signals about lateral acceleration, air, and angular velocity. In the self-rotation mode, the stabilizer installation angle is -6, and in the hover mode +34.
The tail boom can be folded for easy transport or to save parking space. The fuselage is equipped with a shockproof design that can withstand overloads of 10g vertical impact and 20g – frontal. The helicopter is equipped with a rescue winch, the cable of which is 69 m long and has a carrying capacity of 270 kg. The load hook can support up to 3630 kg on an external sling.
Helicopter landing gear tricycle, fixed. Each support has one wheel.
The main racks of lever type are equipped with two-chamber shock absorbers. The chassis pneumatic-hydraulic shock absorption system allows you to absorb impact on the ground without touching the fuselage, equal to 40g overload.
The helicopter has a four-hazard rotor, articulated mounting of the blades. The screw sleeve has a monolithic design, made of titanium alloy and equipped with elastomeric dampers and bearings that do not require lubrication. This reduces maintenance work by up to 60%.
The blades have a rectangular shape. Spars with oval cross-section are made of titanium alloy, in the tail part they have a cellular filler “Nomex”. The butt part and the trailing edge of the blade are made of composite graphite materials, the casing is made of fiberglass. There is a titanium pad on the nose of the blade, and fiberglass counterweights are placed along with the nose. The tip of the blades is swept in shape and made of Kevlar.
Sikorsky S-70 incorporates an anti-icing system of the rotor blades, pendulum self-adjusting bushings of sleeve vibrations, a rotor brake.
The four-blade tail rotor has a diameter of 3.35 m and hinged-free mounting of the blades. The end beam with it is tilted at an angle of 20 degrees to the side to increase the centering range and create a component of vertical thrust. The tail rotor bushing is represented by two cross-shaped beams.
The blades are rectangular, in their composition are composite materials based on graphite epoxide. Similarly to the rotor, the steering blades are also equipped with elements of an electric anti-icing system.
The power plant includes two turboshaft gas turbine engines General Electric T700-GE-700. They are placed in nacelles on both sides of the pylon. The engine was tested in combat operations in Vietnam.
The modular transmission design simplifies maintenance. The main gearbox can operate for 30 minutes without lubrication.
The fuel system includes internal standard fuel tanks with a capacity of 150 liters. The installation of an additional internal tank with a capacity of 440 liters is provided. The helicopter options NN-60 and MN-60 can be understaffed with dropping tanks on wing-shaped high-mounted pylons, the maximum amount of fuel loaded into Sikorsky S-70 fuel tanks is 3545 liters. The helicopter is equipped with a refueling rod in the air.
- Powerplant: 2 x GTE General Electric T700-401 1285kW take-off power
- Rotor diameter: 16.36m
- Fuselage length with refueling bar: 17.38m
- Height: 5.13m
- Take-off weight: 9980kg
- Empty weight: 5735kg
- Top speed: 268km / h
- Cruising speed: 237km / h
- Static ceiling, excluding the influence of the earth: 3170m
- Dynamic ceiling: 5790m
- Flight range: 600km
- Ferry range: 2220km