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XR-4C Hoverfly |
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Photo: Robert Deering 10/23/2006 National Air and Space Museum Dulles International Airport (IAD) Chantilly, Virginia |
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Igor Sikorsky's XR-4 represents two significant milestones. It was the prototype for the world's first mass-production helicopter and was the prototype for the first successful production single-rotor helicopter. The success of this aircraft paved the way for the large-scale introduction of more advanced rotorcraft into military and civilian service. The XR-4 represents the culmination of Igor I. Sikorsky's attempts to create a practical helicopter. This work began in 1909 but did not reach fruition until thirty years later. In addition to its successful service life, the XR-4 ushered in training practices and procedures that became standard in all future rotary winged operations in America.
Sikorsky began to develop the XR-4 when the U. S. Army Air Corps asked for a more advanced version of his successful VS-300 proof-of-concept helicopter, to compete with the Platt-LePage XR-1. The XR-1 was the first practical helicopter funded by the Air Corps, but technical problems were keeping it grounded. Meanwhile, Sikorsky's VS-300 was demonstrating performance and ease of control well beyond that of the XR-1. On December 17, 1940, the Air Corps awarded a $50,000 contract to Sikorsky for production of the XR-4. This occurred simultaneously with the ongoing flight-testing of the VS-300. Sikorsky made numerous changes in construction as he optimized the configuration of the VS-300. Originally, Sikorsky designed the XR-4 with two small lifting rotors on the tail-boom, in addition to the anti-torque rotor, to provide lateral and longitudinal control, as he had done in the design of the VS-300. Sikorsky eventually developed a cyclic pitch change mechanism for the VS-300, and was able to eliminate the tail-mounted lifting rotors. This change carried over to the XR-4 under construction, and created a much more capable and efficient machine, as well as giving the world its first look at what would become the conventional configuration for future helicopters. After careful evaluation, the Air Corps officially accepted the aircraft on May 30, 1942. In May 1943, the XR-4 demonstrated shipboard helicopter operations from the deck of the SS "Bunker Hill." During the war, the R-4B saw limited service, primarily in the Pacific theater. The company incorporated lessons learned from operating the XR-4 and its brethren and designed the R-5 and R-6. These new helicopters could outperform the underpowered R-4. They were also easier to fly and maintain. The R-4 was soon relegated to training duties when these new rotorcraft began entering service. The type disappeared from service shortly after war ended. While the R-4 had a short operational career, it served to introduce the military and potential civilian operators to the possibilities and the limitations of the helicopter. |
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