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Further Reading

YH-16 Transporter

The experimental Piasecki-designed PV-15 (XH-16), was developed for the Army Air Forces as a long-range transport and rescue aircraft.The Piasecki YH-16 Transporter with a twin-rotor design had provisions for up to 43 troops. This helicopter was to have a direct influence on the progress of the Marine Corps' forthcoming helicopter program. It appealed to all services because it had a gross weight of 46,000 pounds and a useful load capability of 14,000 pounds or 40 passengers. The tandem design XH-16, with two engines driving the two 82-foot diameter rotors, was the largest helicopter in the world. Although development of this gigantic helicopter was started by Piasecki in 1946, almost concurrent with the HJP-1, its first flight would not occur until more than seven years Iater. The development of this transport and rescue helicopter was accelerated in response to the Korean War.

On 09 July 1947 the Commandant made an important change relating to the helicopter's characteristics by specifying only one size helicopter of a 5,000-pound minimum payload capability. It eliminated the requirement for the helicopter to be accommodated by the ship's elevator and stowed on the hangar deck and listed the overall dimensions as "small as possible." The design proposal for a 3,500-pound helicopter was cancelled. In order that the early landing may he provided with necessary continuity, it is necessary that communications vehicles, recoilless weapons, and initial resupply he provided at an early hour and, ideally, that these should be followed by artillery. This required a payload of approximately 5,000 pounds.

The Chief of the Bureau of Aeronautics cast the assault helicopter transport program into the development doldrums by linking it with the Air Force's XH-16 program. The CNO was informed by BuAer on 24 December 1947 that additional studies indicated the development of a large helicopter meeting the requirements of the Marine Corps was feasible, but it would involve a four- or five-year program and require considerably more funds than could be obtained in view of the continuing budget curtailments.

"It now appears," the Bureau Chief stated ". . . that the assault helicopter characteristics are very similar to those of the XH-16 helicopter contemplated by the Air Force . . . and insofar as the basic helicopter is concerned, are almost identical. In view of this fact, effort on the assault helicopter will be undertaken on the basis of joint Air Force/Navy development of the XH-16.

By the end of 1947, the new Marine program appeared to have a sense of direction and momentum. Organizationally, the first helicopter squadron had been formed in December for the purpose of determining the operational feasibility of the vertical envelopment concept. Plans for execution of the concept in terms of aircraft were based upon the eventual acquisition of a very large helicopter - the Piasecki XH-16. In preparation of a concept, the special group designated as the Helicopter and Transport Seaplane Board had been formed to develop a tentative doctrine for the employment of helicopters in amphibious operations.

Unfortunately, two years later, the whole process had reached a developmental plateau which jeopardized the entire helicopter program. Lack of continued progress could be attributed to the inability to realize that the helicopter manufacturers were unable to comply with their own predictions for meeting the specifications and requirements which they had so willingly accepted. Additionally, an exceptionally long developmental period was required once the decision on the type of helicopter was made and the money budgeted to coincide with its development.

The Navy and Air Force were developing jointly the Piasecki XH-16. Because of the time required to perfect fully such a large helicopter, and its doubtful ability to operate from small aircraft carriers, it appeared advantageous for the Marines to proceed with an additional project for the development of a small helicopter which will meet the Marines minimum requirements, which will be suitable for carrier operations, and might well be more easily and quickly obtained.

By mid-1949 the Navy and Air Force were developing jointly the Piasecki XH-16. The XH-16 represented a large step forward in helicopter technology and would require extensive component and flight testing after the anticipated completion date of the first test aircraft in 1952. This would preclude the construction of production models for an appreciable length of time since only two experimental aircraft were being built. By January 1950 the XH-16's lengthy development period was seen as seriously retarding the Marine Corps helicopter program and although it was not desired to divert funds for its support, emphasis was placed on allocation of funds toward the proposed 3,000 pound payload helicopter. The diversion of the remaining XH-16 Navy research and development funds was also viewed as meeting with CNO approval provided the Navy could be persuaded to terminate its support of the XH-16 project.

After a discussion, it was determined that the helicopter program of the future should be composed of two parts. First, and as the longer-range solution, the Marine Corps should continue with the program to obtain a carrier-based assault helicopter which would meet the requirements of AO-17501 (XHR2S-1), as was recommended by the March 1950 helicopter conference, and simultaneously attempt to persuade the Army and Air Force to cancel the XH-16 project and join with the Marine Corps in developing the XHR2S-1.

Piasecki had continued the development of its XH-16, originally the Marine Corps' hope for a large assault transport helicopter. However, it too - although still under construction - would soon join the list of unsuccessful ventures. The first model of Piasecki's XH-16 was truly a flying crane as it was designed to carry its load in detachable "pods. " Piasecki's second XH-16 had a large cabin and was the type which had interested the Marine Corps as an assault transport. Both aircraft failed primarily because the state of power plant and transmission development had not advanced sufficiently to match the demand.