section_path: Development/Upgrades and variations
section_name: Upgrades and variations
paragraph_text: Upgrades and variations
  
  After entering service, the helicopter was modified for new missions and roles, including mine laying and medical evacuation. An EH-60 variant was developed to conduct electronic warfare and special operations aviation developed the MH-60 variant to support its missions.
  
  Due to weight increases from the addition of mission equipment and other changes, the Army ordered the improved UH-60L in 1987. The new model incorporated all of the modifications made to the UH-60A fleet as standard design features. The UH-60L also featured more power and lifting capability with upgraded T700-GE-701C engines and an improved gearbox, both from the SH-60B Seahawk. Its external lift capacity increased by 1,000 lb (450 kg) up to 9,000 lb (4,100 kg). The UH-60L also incorporated the SH-60B's automatic flight control system (AFCS) for better flight control with more powerful engines. Production of the L-model began in 1989.
  
  Development of the next improved variant, the UH-60M, was approved in 2001, to extend the service life of the UH-60 design into the 2020s. The UH-60M incorporates upgraded T700-GE-701D engines, improved rotor blades, and state-of-the-art electronic instrumentation, flight controls and aircraft navigation control. After the U.S. DoD approved low-rate initial production of the new variant, manufacturing began in 2006, with the first of 22 new UH-60Ms delivered in July 2006. After an initial operational evaluation, the Army approved full-rate production and a five-year contract for 1,227 helicopters in December 2007. By March 2009, 100 UH-60M helicopters had been delivered to the Army. In November 2014, the US military ordered 102 aircraft of various H-60 types, worth $1.3 billion.
  
  Following their use in the operation to kill Osama bin Laden in May 2011, it emerged that the 160th SOAR used a secret version of the UH-60 modified with low-observable technology which enabled it to evade Pakistani radar. Analysis of the tail section, the only remaining part of the aircraft which crashed during the operation, revealed extra blades on the tail rotor and other noise reduction measures, making the craft much quieter than conventional UH-60s. The aircraft appeared to include features like special high-tech materials, harsh angles, and flat surfaces found only in stealth jets. Low observable versions of the Black Hawk have been studied as far back as the mid-1970s.
  
  In September 2012, Sikorsky was awarded a Combat Tempered Platform Demonstration (CTPD) contract to further improve the Black Hawk's durability and survivability. The company is to develop new technologies such as a zero-vibration system, adaptive flight control laws, advanced fire management, a more durable main rotor, full-spectrum crashworthiness, and damage-tolerant airframe; then they are to transition them to the helicopter. Improvements to the Black Hawk are to continue until the Future Vertical Lift program is ready to replace it.
  
  In December 2014, the 101st Airborne Division began testing new resupply equipment called the Enhanced Speed Bag System (ESBS). Soldiers in the field requiring quick resupply have depended on speed bags filled with items airdropped from a UH-60. However, all systems were ad hoc with bags not made to keep objects secure from impacts, so up to half of the airdropped items would be damaged upon hitting the ground. Started in 2011, the ESBS sought to standardize the airdrop resupply method and keep up to 90 percent of supplies intact. The system includes a hands-free reusable linear brake and expendable speed line and a multipurpose cargo bag. When the bag is deployed, the brake applies friction to the rope, slowing it down enough to keep the bag oriented down on the padded base, a honeycomb and foam kit inside to dissipate energy.
  
  The ESBS better protects helicopter-dropped supplies, and allows the Black Hawk to fly higher above the ground, 100 ft (30 m) up from 10 feet, while travelling 20 knots (23 mph; 37 km/h), limiting exposure to ground fire. Each bag can weigh 125–200 lb (57–91 kg) and up to six can be deployed at once, dropping at 40–50 feet per second (12–15 m/s). Since supplies can be delivered more accurately and the system can be automatically released on its own, the ESBS can enable autonomous resupply from unmanned helicopters.