The H-19 Chickasaw holds the distinction of being the US 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. Marine Corps made extensive Korean War use of the H-19, called the HRS in USMC service.In 1956, the French Air Force experimented with arming the H-19, then being superseded in service by the more capable Piasecki H-21 and Sikorsky H-34 helicopters.
On September 13, 1951 HMR-161, during Operation Windmill I, transported 18,848 pounds of gear and 74 Marines into a ridgeline position in the Punchbowl area.
A week later HMR-161 shuttled 224 Recon Company Marines and 17,772 pounds of supplies to a remote hilltop in the same area.
The offset flapping hinges and hydraulic servos gave more positive flight control under differing loading conditions, isolated the flight controls from vibration, and lessened control forces; the H-19 could be flown with only two fingers on the cyclic control.
The YH-19 prototypes featured a blunt aft fuselage and a single starboard-mounted horizontal tailplane with a small vertical fin at its outboard end.
The first customer was the United States Air Force, which ordered five YH-19 aircraft for evaluation; the YH-19's first flight was on 10 November 1949, less than a year after the program start date. 1,281 of the helicopters were manufactured by Sikorsky in the United States.
The helicopter was initially designed as a testbed for several novel design concepts intended to provide greater load-carrying ability in combination with easy maintenance. Katzenberger, a mockup was designed and fabricated in less than one year. On 27 April 1951, the first HRS-1 was delivered to the U. Marine Corps, and on , the first S-55 was delivered to Westland Aircraft.
To reduce their exposure, men and launchers were moved twice a day.
HRS-1 helicopters 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. Air Force ordered 50 H-19A's for rescue duties in 1951.