The HR3S was a USMC assault helicopter project, as XHR3S-1, in competition with Boeing-Vertol HRB. Only a mock-up was built, but the design evolved into CH-3C and civil version S-61R.

Military planners are faced continually with the problem of obsolescence of combat equipment. This is particularly true of aircraft. In the late 1950s when the Marine Corps was faced with the problem of maintaining three combat ready divisions and aircraft wings under a severely restricted budget, it had to prepare for the replacement of the aircraft being introduced into service. General McCutcheon touched on this subject and although his remarks were made almost a decade later, they were just as appropriate for this period as they were then. He said, "Aviation is a dynamic profession. The rate of obsolescence of equipment is high and new aircraft have to be placed in the inventory periodically in order to stay abreast of the requirements of modern war." In relation to the helicopter program, this involved suitable replacements for the piston-engine-powered HR2S, HUS, and HOK models.

Despite the tightening budget, the Commandant on 9 January 1958 informed the CNO that the Marine Corps required a replacement for its light (HUS) helicopter fleet. General Pate noted the inadequacy of the HUS-1 to fulfill future assault requirements and requested that 210 troop and cargo versions of the Navy's newest ASW helicopter, the twin-jet engine HSS-2, be procured during the 1962-1966 time frame. At the time, there appeared to be no other helicopter available which was competitive with the Sikorsky-built aircraft from either a cost or technical viewpoint.

The recommended designation for the transport version of the HSS-2 was HR3S-1. It was not until 16 March 1959 that the CNO published Operational Requirement Number AO-17501, the second revision of the new transport. One year later, on 7 March 1960, he issued Developmental Characteristic Number AO-17501-2, VTOL Assault Transport Helicopter, as Appendix II to the 1959 operational requirement. This second revision spelled out a requirement for a helicopter capable of carrying a payload of 4,000 pounds, or 17 combat-equipped troops, over a 100-nautical mile radius. Additional requirements specified that it have multi-engines, a rear loading ramp, automatic blade-folding capability, carry a crew of three, and cruise at a speed of not less than 125 knots. It further stated that the specifications listed in the developmental characteristics had to be met by a modification of a helicopter already developed and that it must be ready for operational evaluation by 1963.

While detailed specifications for the HR3S-1 were being developed by BuAer, Sikorsky discovered that in order to modify the HSS-2 to a rear ramp-loading transport, an extension to the forward fuselage would be necessary. Due to the delay caused by this problem, the HR3S was now being compared to another aircraft.

The Vertol Corporation had developed the YHC-lA transport for the Army and the commercial version of this helicopter, the 107M, offered a high degree of competition to the Sikorsky HR3S. As a result, BuWeps representatives in June 1960 gave a presentation in which the capabilities of both helicopters were outlined. In the proceedings, the HR3S-1 was shown to be a significantly cheaper aircraft and to have obvious logistics and training advantages; however, the Vertol 107 was presented as being fully as adequate, technically, as the HR3S-1 to accomplish the assault mission.

On 1 July 1960, the Director of the Marine Corps Landing Force Development Center at Quantico, Brigadier General William R. Collins, (and a former president of the Tactics and Techniques Board), informed General David M. Shoup, the Marine Corps' 22d Commandant, that the Development Center was monitoring closely the progress of both helicopters and that the data given at the BuWeps briefing differed considerably from that available at the development center. General Collins pointed out that "there was a considerable divergence which, if valid, shows the Vertol 107 in a much more favorable light. It appears to be in the best interest of the Marine Corps to make a more comprehensive evaluation of the two aircraft." Accordingly, the general recommended that a comparative flight evaluation be conducted between the Vertol 107 and the Sikorsky HR3S-1.

As a result of the pressure generated at Quantico for an objective comparison between the two competing designs, BuWeps assured the Commandant on 8 September that proposals from both Vertol and Sikorsky would be obtained. The next month BuWeps sent invitations for bids to the two companies. The following February, BuWeps announced its decision, declaring Vertol's design as the winner of the competition. Subsequently, the first flight of the HRB-1 was scheduled by Boeing-Vertol for June 1962 with delivery to FMF units projected for early 1964.

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Page last modified: 07-07-2011 02:33:10 ZULU