Bell 61

The Bell 61 was the only tandem rotor type designed by Bell. it was developed as an anti-submarine warfare helicopter for the US Navy. First flew on March 3, 1953. Two prototypes XHSL-1 were built plus one ground test vehicle. Urgent needs made the Navy assigned 234 Bureau Numbers and signed a contract for the first 160 including 18 for the Royal Navy. Performance and production issues forced that only 50 HSL-1 were built. The HO4S (Sikorsky S-55), which the HSL-1 had been intended to replace remained in service until the introduction of the HSS-1 (S-58). Only a few were delivered to the US Navy and used for test purpose only. Proposed civil variants models D-116, D-216 and D-238 they did not go beyond the planning phase

Ambitious order book from the US Navy was scaled back by cancellation of some contracts.