The S-55 was the first transport helicopter to receive Civil Aeronautics Administration 's (forerunner of today's Federal Aviation Administration) approval for commercial operation and enter scheduled passenger service.
Sikorsky manufactured near 1300 S-55s in ten years of continuous production commencing in 1949 and was also build under license in Great Britain by Westland as the Whirlwind in France by Sud-Est and in Japan by Mitsubishi,
Sikorsky manufactured near 1300 S-55s in ten years of continuous production commencing in 1949 and was also build under license in Great Britain by Westland as the Whirlwind in France by Sud-Est and in Japan by Mitsubishi,
Derivatives & Versions
| S-55 | 1949 | Commercial version with 600HP P&W R-1340 Wasp engine. |
| YH-19 | 1949 | The first of the five YH-19 prototypes capable of carrying ten passengers in addition to a crew of two first flew on 10 November 1949 and was characterized by a blunt-ended fuselage, which lacked the broad, triangular fillet connecting the fuselage to the tail boom which distinguished all the later series aircraft. |
| H-19A Chickasaw | 1950 | USAF version of the YH-19 powered by a 600hp P&W R-1340-57 Wasp engine. |
| HO4S-1 | 1950 | US Navy version of the S-55 powered by a 600hp P&W R-1340-57 Wasp engine. |
| S-55A | 1950 | Commercial version with 800HP Wright R-1300-3 Cyclone engine. |
| HO4S-2 | 1951 | Navalized SAR version of the H-19B powered by a 700hp Wright R-1300-3 Cyclone engine. |
| HRS-1 | 1951 | USMC version of the HO4S-1 with P&W R-1340-57 Wasp engine for eight troops, 60 built, plus one static airframe used for testing. |
| S-55B | 1951 | Improved commercial version with 800HP Wright R-1300-3 Cyclone engine. |
| H-19C Chickasaw | 1952 | US Army version of the H-19A with 600HP P&W R-1340-57 Wasp engine for troop transport duties. |
| HO4S-3 | 1952 | Re-engined US Navy & Canadian version with 700HP Wright R-1300 Cyclone engine. |
| HRS-2 | 1952 | USN/USMC HRS-1 with equipment changes, 101 built. |
| → Whirlwind | 1952 | During 1950, the Royal Navy had received 10 rescue (HAR. |
| Whirlwind HAR.21 | 1952 | Ten Sikorsky HRS-2 for UK Royal Navy as Whirlwind HAR. |
| Whirlwind HAS.22 | 1952 | Fifteen Sikorsky HO4S-3 for UK Royal Navy as Whirlwind HAS. |
| H-19B Chickasaw | 1953 | USAF version of the H-19A powered by a 700hp Wright R-1300-3 Cyclone engine. |
| H-19D Chickasaw | 1953 | US Army version of the H-19B powered by 700HP Wright R-1300 Cyclone engine. |
| HRS-3 | 1953 | Improved HRS-2 with a 700HP Wright R-1300-3 Cyclone engine. |
| S-55C | 1953 | Improved commercial version with 800HP Wright R-1300-3 cyclone engine. |
| H-19D-3 | 1956 | US Army improved version of the H-19D. |
| HRS-3Z | 1956 | VIP version of HRS-3 for France. |
| H-19D-4 | 1957 | H-19D-3 with equipment changes for France. |
| HO4S-3G | 1957 | Specialized SAR version of HO4S-3 for USCG. |
| → S-55 | 1958 | |
| S-55T | 1969 | Designation applied to aircraft modified with a 650 shp Garrett AirResearch turboshaft and other updated equipment. |