H-34 2.75-Inch Aerial Rocket Weapons System

In 1955 the Army studied a "helicopter gunship" concept which yielded fabrication and testing of different types of helicopter armament. The objective of this project was to provide responsive suppressive fire support for troops being transported by helicopter, particularly at the time of landing when they were most vulnerable. Weapons inaccuracy caused by the helicopter's instability proved to be the most difficult problem to overcome. The Army achieved outstanding results in 1958 when it loaded an H-34 helicopter with forty 2.75 inch and 2.5 inch rockets, nine machineguns, and two 20 mm cannons.

The 2.75-Inch (Modified) Aerial Rocket Weapons System was under development for the HU-1B helicopter, the Army's first gunship. This model served in Vietnam in various roles including armed support, carrying sixteen 2.75-inch rockets. The UH-1B model did not begin its user evaluation testing until 28 November 1960, and saw service in large numbers by June of 1963.

The 2.75-Inch (Modified) Aerial Rocket Weapons System mounted on the H-34 offered an immediate capability to fullfill the Army's requirement for an area fire weapons system with 48 rockets [three times the load of the HU-1B]. The 2.75-Inch Aerial Rocket Weapon System, mounted on the H-34, was conceived, designed, and fabricatd with a view toward giving the Army an immediate field capability for helicopter armament on helicopters currently in use throughout the military system. The Aviation Board recommended that a program be initiated to permit funding of this weapon system; however, this project was not formally established by the Weapons Systems Management Office of the Transportation Corps. Without formal recognition, funds could not be allocated nor authority granted to enter further developement or combat service.

In 1961 tests were conducted on a series of armament systems capable of rapid mounting and demounting on Army helicopters. The armament system consisted of weapons and ammunition from current weapons systems of advanced design, together with synchronized sighting, mounting, and firing devices providing for elevation, depression, and traverse where required. Mountings were provided to permit attachment of various combinatiors of weapons to fit the mission. The systems would be employed as elevated firing platforms in support of offensive and defensive ground combat operations. The systems would provide for full utilization of new weapons and ammunition and the maneuverability of Army helicopters.

The Army's capability for launching rockets from helicopters had been limited to those equipped to fire 4.5-inch rockets for demonstration and training purposes. Adoption of the 4.5-inch rocket for Army use from helicopters was not advisable due to the weight imposed by the rocket system, the limited supply of rockets, and the fact that the rockets were no longer in production. Ordnance Corps investigations revealed that the 2.75-Inch Folding Fin Aircraft Rocket (FFAR) offered the best potential for providing an immediate helicopter rocket-firing capability. This rocket was lighter in weight than the 4.5-inch rocket, was in production, and was a standard item of supply for the US Air Force, Navy and Marine Corps.

The 2.75-inch aircraft rocket was designed to be launched from a high-performance airplane. To insure rocket stability immediately upon leaving the rocket pod, the rocket required a higher aircraft speed than that attained by Army helicopters. Since the helicopter did not have this speed capability, it was necessary to modify the rocket to obtain a spin in order to achieve stability upon launch by averaging thrust misalignment. Tests by the US Navy indicated that the zero-airspeed launch dispersion of 40-50 mils experienced with the standard rocket was reduced to 10-12 mils by this nozzle-scarfing modification.

During April 1961, two hundred 2.75-inch (modified) aerial rockets were evaluated by Aviation Board personnel in coordination with Ballistic Research Laboratories (BRL), Aberdeen Proving Grounds, using an H-21 helicopter as the weapons platform. Results of the evaluation verified that the modified 2.75-inch aerialrocket was suitable for use as helicopter armament.

An H-34 (serial number 56-4299) assigned to the Aviation Board was equipped with a 2.75-inch rocket system which was developed and fabricated by the Army Ordnance Missile Command (AOMC), Redstone Arsenal, Alabama. The equipment was received 28 August 1961. The 2.75-Inch (Modified) Aerial Rocket Weapons System mounted on an H-34 helicopter was evaluated by the Aviation Board during the period 27 September 1961 to 21 January 1962. Technical assistance was furnished by AOMC.

The rocket-pod-suspension frame was attached at hard points on either side of the helicopter. The lower attaching points required replacement of the original sling attaching brackets with brackets modified to incorporate an attaching lobe. The upper forward attaching points require removal of the existing steps and replacement with steps modified to incorporate two attaching lobes.

The bomb rack utilized with this installationis a type MA-4A with a rated capacity of 2000 pounds and a 14-inchspan between attaching points. The rocket pod was a 24-tube modular pod which consisted of four six-tube modules. Each module was attached by steel pins to the adjacent module(s). The entire pod was then hung by an adapter bracket to the bomb rack on each side of the helicopter. The pod was wired to the fire-control panel and trigger through a cannon plug on the skin of the aircraft.

The 2.75-inch FFAR is a standard Navy Type Mark IV Mod VI which was modified to imparta ballistic spin of approximately five revolutions per second byscarfing the thrust nozzles at a 24-degree angle. This modification imparted sufficient spin to the rocket to average out thrust mis-alignment and stabilize the rocket with the assist of the extended fins. The rocket measured 43.7 inches in length and 2.75 inches in diameter, and weighed 10.1 pounds. It was available with HE and AT warheads.

The system was found to be compatible with the H-34. The total weight of this system with 48 rockets was 1350 pounds. Center of gravity was not adversely affected, and no control problems or unusual flight attitudes were evident. The system proved to be trouble-free throughout the test and appeared to be durable enough for sustained use under tactical conditions. The system when fired during forward flight was accurate. Firing of a full complement of rockets resulted in an impact area measuring approximately 40 x 400 meters at an opening range of 1500 meters-from an absolute altitude of 150 to 200 feet and 70 knots IAS. As with any fixed helicopter-mounted weapons system elevated for in-flight firing, hover fire was difficult and resulted in inaccuracies.

A two-hour period of ground instruction and in-flight firing of at least 144 rockets should be sufficient to train an aviator/gunner to employ the system effectively. The helicopter crew chief required 16 hours of on-the-job training in system functioning, safety precautions required, rocket handling, and care and cleaning of the system.

To simplify logistics, the Army segregated its two large helicopters geographically. The CH-34s served the eastern United States and Europe. The CH-21s served the western United States and Asia. When the war in Southeast Asia began, the Army sent CH-21s to support operations because Southeast Asia was in the CH-21 region. This kept Army Choctaws out of the war. The Army’s weapons experience showed that the CH-34 was marginal as an offensive weapons platform because of its relatively weak structure. Later, UH-1 Hueys did have the strength to be effective offensive gunships.

The helicopter took more evolutionary steps toward the modem attackhelicopter during the French - Algerian War. The French, like the British in Malaya, found the use of helicopters to be very beneficial in counterinsurgency operations. The French, though, believed that the only way to provide sufficient protection from small arms fire during the landing of assault troops was to improve both armament and armor protection. The weaponry suppressed the ground fire while the armor protected the crew and the aircraft. The French used the results of the US Army tests of 1958 as the basis for their armament, eventually mounting two .30 caliber machine guns and seventy-two 37 mm rockets.

In the war fought from 1954 to 1962, the French forces in Algeria pioneered troop assault, large-scale resupply, and especially the gunship role. The H-34 sometimes had forward-firing rockets and machine guns, as well as side-firing 50 caliber machine guns and even a 20 mm cannon firing through the door on the port side. The H-34 proved the best gunship of the war. These "Pirates," as the gunships were known, often provided the most responsive and effective air support for troops in the field.

The French also experimented with anti-tank missile systems starting in 1958. The French believedthat the tank presented a larger target silhouette to an aerial platform which in turn permitted a wider array of angles for attack.67 The French began arming one in every six helicopters. Once armed, these helicopters carried no troops andfocused solely on providing close air support to an assault landing.