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unit required to engage in activities designed solely for test purposes.

More fundamental limitations were the rules of engagement for U.S. Army armed helicopters, which precluded testing of any tactical concepts involving "offensive" employment. Under these rules, the armed helicopters could deliver fire only after they or the escorted transport helicopters had been fired upon. In late February 1963 the rules were modified to permit the armed helicopters to initiate fire against clearly identified insurgents who threatened their safety or the safety of armed transport helicopters.

Initially, the fifteen UH-1A helicopters were armed with locally fabricated weapons systems consisting of two .30 caliber machine guns and sixteen 2.75-inch rockets. In November 1962 the unit was augmented with eleven UH-1B helicopters. The "B's" were equipped with factory installed weapons systems of four M-60 machine guns per aircraft and locally fabricated clusters of eight 2.75-inch rockets. The "B" model eventually replaced most of the less powerful "A's."

The provisional Utility Tactical Transport Helicopter company was based at Tan Son Nhut Airport on the outskirts of Saigon and was under the direct operational control of Military Assistance Command, Vietnam. From this time, it supported transport operations of the 57th, 33d, and 93d Light Helicopter Companies, all equipped with CH-21 aircraft. In the latter part of the test period, one platoon of helicopters was sent to escort the Marine H-34 squadron operating in I Corps.

The plan of test for this company called for the evaluation of the armed helicopter in the "escort" role. Although "escort" was not defined, actual experience determined that the escort role broke down into an enroute phase, that was generally flown at a relatively safe altitude, the approach phase, where the heliborne force usually descended to nap-of-the-earth heights several kilometers away from the landing zone, and the landing zone phase. It was in the landing zone phase that the armed helicopter proved most valuable.

Prior to the advent of the escort by the Utility Tactical Transport Helicopter company, transport helicopters on the "dangerous" combat support missions were being hit at a rate of .011 hits per flying hour. For similar missions escorted by the Utility Tactical Transport Helicopter company, the rate declined to .0074. During this same period of time, the hit rate for all other flying done by Army helicopters rose from .0011 to .0024. In other words, the Viet Cong effectiveness against unescorted aircraft doubled while