Initially procured in 1956, the Sikorsky (model S-56) CH-37A/CH-37B, with a crew of three, was a large medium lift transport helicopter. Clam shell doors in the nose provided access to a cargo compartment that could accommodate two jeeps or a 105mm howitzer. The Mojave could carry 26 troops or 24 litters in the MedEvac role. The CH-37 had a single five-bladed main rotor and a metal four-bladed tail rotor. The CH-37 was powered by two Pratt & Whitney R-2800-54 2100 hp pistons engines and had a speed of 131 mph (114 knots).
Production of the S-56 ended in May 1960, but Sikorsky was engaged until the end of 1962 in converting all but four of the H-37A's to H-37B (later CH-37B) standard. Improvements in this version included the installation of Lear auto-stabilisation equipment and the ability to load and unload while the helicopter was hovering.
In February 1963, the Department of the Army quickly and quietly snatched up a large group of soldiers from a variety of locations and set them down at Fort Benning, Georgia, where they became part of the innovative 11th Air Assault Division (Test) (11th AAD). The idea was to create a combat force "freed from the tyranny of terrain" by exploiting the capabilities of Army aviation.
Initially, the medium lift helicopter available to the division was the venerable CH-37, Mojave. The then brand new CH-47, Chinook, did exist; but very few of these "Hooks" were available, and they were experiencing the "teething" problems normally associated with new equipment. Both helicopters could carry a howitzer as an internal or external load. In the continental United States, Redlegs favored the former approach. After all, an inadvertently dropped howitzer sling load makes a terrible mess on the ground and might even damage a howitzer.
One early experiment in ammunition resupply occurred during an 11th AAD Artillery firing demonstration at Fort Benning. In a cooperative effort involving aviation, support command, and field artillery elements, soldiers trucked ammunition to a small airstrip. There, they broke it down into a variety of helicopter loads and moved it to the firing battery via a combination of internal and external shipments using both the CH-37 and CH-47 helicopters. The demonstration clearly showed that ammunition could be loaded very quickly into a helicopter using various pieces of cargo handling equipment. Unfortunately, unloading at the battery position relied exclusively on the strong backs and legs of battery personnel. Sling-loading ammunition using a nylon mesh sling was the way to go.
On 31 May 1965 the 3d Battalion, 319th Artillery, as part of Task Force SURUT, participated in the largest air assault conducted in Vietnam to that date. The task force, consisting of the 319th reinforced by a cavalry troop, an engineer platoon and a composite platoon made up of volunteers from the support battalion, secured a landing zone (LZ) and guided in CH-37 Mohave helicopters carrying the howitzers. Up to this point in the war, the Mohaves had been doing yeoman duty as all-purpose aircraft. So smoothly and efficiently did this initial move go that three hours later these same howitzers mounted preparation fires on another LZ for Task Force DEXTER, a reinforced infantry element of the 173d Brigade. This was the first such operation ever conducted in actual combat by a US Army unit-one that had been in Vietnam less than 30 days.
It was used for aircraft recovery in Vietnam. That the CH-37 did not see more extensive service in Vietnam is primarily the result of its replacement in the Army inventory by the turbine-powered Sikorsky CH-54 Tarhe, a machine that weighed slightly less than the CH-37 but which could carry nearly four times as many troops or five times as much cargo. The last CH-37 was withdrawn from Army service in the late 1960s. The CH-37 was replaced by the CH-47D Chinook, but of course the CH-47 did not have CH-37's heavy-lift capability.
During the period July 1957 through November 1966 there were 264 CH-37 mishaps reported, to include accidents, incidents, forced landings, and precautionary landings. Of these, 29 were major accidents and four were minor accidents. There were 47 incidents, 89 forced landings, and 95 precautionary landings. Review of the major accidents indicated that pilot factors accounted for 48.3% of the major accidents, while materiel failures or malfunctions were responsible for 37.9%. Weather, supervision, and maintenance were responsible for the remaining 13.8%. Many incidents, forced landings, and precautionary landings are recorded with cause factors not reported. This results from reporting units failing to provide supplemental information as it becomes available. Reports of this nature, without supplemental data, are of little use to the aviation safety program and all units reporting similar mishaps are urged to follow through with supplemental data as soon as it becomes available.
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