The H-19 Chickasaw holds the distinction of being the U.S. Army's first true transport helicopter and, as such, played an important role in the initial formulation of Army doctrine regarding air mobility and the battlefield employment of troop-carrying helicopters. The H-19 underwent live service tests in the hands of the 6th Transportation Company, during the
Korean War beginning in 1951 as an unarmed transport helicopter. Undergoing tests such as
medical evacuation, tactical control and frontline cargo support, the helicopter succeeded admirably in surpassing the capabilities of the
H-5 Dragonfly which had been used throughout the war by the Army. The U.S. Marine Corps (USMC) made extensive use of the H-19 in the Korean War. It was designated as the HRS in USMC service. Marine Squadron
HMR-161 arrived in Korea on 2 September 1951 with 15 HRS-1 helicopters. The new helicopter squadron started operations upon arrival. On 13 September 1951, during Operation Windmill I, HMR-161 transported of gear and 74 Marines onto a ridge in the
Punchbowl area. A week later HMR-161 shuttled 224 recon company marines and of supplies to a remote hilltop in the same area. Their performance continued to improve and in Operation Haylift II on 23–27 February 1953, HMR-161 lifted of cargo to resupply two regiments. Although HMR-161 helicopters were operating in "hot" landing zones near enemy troops, they did not lose any helicopters to enemy fire. HRS-1 helicopters were also used to relocate rocket launcher batteries; the rockets created a dust cloud when fired, making the launcher a target for
counter-battery fire, so launchers and crews were moved twice a day. Each HRS-1 helicopter carried four rocket launchers and extra rockets as external cargo, with the crew in the cabin. The HRS-1 helicopter proved to be durable and reliable in Korean service. One reportedly flew home after losing of main rotor blade to a tree. HMR-161 reported 90% aircraft availability. The success of helicopter operations with the USMC prompted the service to seek a
military light utility vehicle that the HRS could lift, leading to the development of the aluminum-bodied,
M422 Mighty Mite in the early 1950s. However, developmental issues delayed deployment of the M422 until 1959, by which time the HRS was being replaced by utility helicopters capable of lifting standard U.S. light utility vehicles, rendering the M422 unnecessary anddue to its unique designa
supply chain liability. The Mighty Mite was only produced in small numbers and was mostly withdrawn from service by the late 1960s. The U.S. Air Force (USAF) ordered 50 H-19A's for rescue duties in 1951. These aircraft were the primary rescue and medical evacuation helicopters for the USAF during the Korean War. The Air Force continued to use the H-19 through the 1960s, ultimately acquiring 270 of the H-19B model. ace
Joseph C. McConnell; the actual rescue was conducted using a different H-19. On 1 September 1953,
Sabena used the S-55 to inaugurate the first commercial helicopter service in Europe, with routes between Rotterdam and Maastricht in the Netherlands and Cologne and Bonn in
West Germany. Pakistan ordered eight S-55s in 1956 to equip
search and rescue squadrons of the
Pakistan Air Force. They saw service during the
1965 Indo-Pakistani War, flying various missions including
counterintelligence operations at Karachi in co-operation with the
Army. They were retired from service in 1971. The H-19 left U.S. military service when the CH-19E was retired by U.S. Navy squadron
HC-5 on 26 February 1969. Surplus H-19s were sold on the open market, and civil interest was sufficient that Sikorsky (and later
Orlando Helicopter Airways or OHA) offered conversion kits allowing a military surplus H-19 to be commercially operated under a standard
Federal Aviation Administration type certificate as an S-55B.
Turboshaft conversions were also offered by aftermarket modification companies. In the mid-1980s, the U.S. Army sought an economical helicopter to simulate the sound and
radar signature of the Soviet
Mil Mi-24 during exercises. OHA sold the Army fifteen modified
S-55/Mi-24s with a new five-bladed rotor system, which was quieter than the original three-bladed rotor and made the aircraft sound similar to an Mi-24. The piston engines and original Sikorsky tail rotors were retained. OHA also produced the
S-55QT Whisper Jet, an extra-quiet civil conversion based on the five-bladed S-55/Mi-24, but using an
Garrett TPE331 derated to from the S-55T, which lowered the aircraft's empty weight by . The aircraft were also outfitted with special intake and exhaust silencers,
carbon fiber noise-absorbing engine compartment doors, and a transparent
Plexiglas floor. Five aircraft were built in 1999 to comply with strict
National Park Service noise limits for
Grand Canyon aerial tours; however, the aircraft were only used in this role for two years because it was difficult for pilots in the high-mounted cockpit to communicate with tourists in the main cabin. After being retired from sightseeing, the helicopters were used in utility and lift roles. ==Variants==