A significant change took place in the coordinating arrangements that governed U.S. helicopter units supporting I Corps at approximately the same time that HMM-261 initiated combat support operations. Since its relocation at Da Nang, the Marine task element, along with all other aviation units in I CTZ, had received its missions from the Air Support Operations Center located within the corps headquarters. As the number of U.S. and VNAF aviation organizations assigned to I Corps grew and the total number of missions multiplied, it became necessary to modify the system of coordination and control. In accordance with a ComUSMACV directive, I Corps headquarters created an Aviation Headquarters Operations Center (AHOC) to oversee the employment of Marine and Army aircraft in the CTZ. The AHOC, which was composed of a senior Army representative, a senior Marine representative, and an operations section, was to be directed by the Commander, Task Element 79.3.3.6. Formally stated, its primary mission was to “plan, direct, and control the employment of all Army and Marine Corps Aviation Units and aircraft operations in direct support of I Corps.” The newly organized AHOC was also ordered to “participate in, and provide assistance to operational planning and the coordination of employment of USA/USMC Aviation with VNAF/USAF tactical air.”[9-6] The AHOC, therefore, was formed to supplement rather than replace the older Air Support Operations Center, which continued to direct and control all U.S. Air Force and VNAF operations over the northern provinces. It was under this arrangement that U.S. Marine and Army aviation units operated after mid-1963. HMM-261’s Marines began encountering systematic Viet Cong resistance to their operations shortly after their first combat missions in early June. A 21-aircraft assault mission into the mountains west of Da Nang was aborted on 6 July when the Marine pilots discovered that the Viet Cong had obstructed the two available landing zones with upright stakes. While inspecting one of the landing zones on a low pass, a helicopter was hit in the forward fuel cell by Communist small arms fire. The damage to the aircraft was not serious enough to force a landing, but the pilot of an escorting U.S. Army UH-1B was mortally wounded while attempting to suppress the ground fire. Ten days after the enemy forced the cancellation of the assault mission west of Da Nang, HMM-261 suffered its first aircraft loss in Vietnam. The crash, which was later attributed to mechanical failure, occurred about 37 miles southwest of Da Nang while one of the squadron’s helicopters was on a routine logistics mission. Six passengers, two American advisors and four ARVN soldiers, were injured in the accident. The squadron commander dispatched two other UH-34Ds to the scene of the crash to evacuate the wounded and insert a salvage team. The badly damaged aircraft was assessed as beyond repair and was destroyed.