Only by shifting operational hoists from unit to unit, as required, were the hoist mission requirements adequately met. Flying conditions in Vietnam proved to be a great threat to the safety of medical aircraft and crew in 1967 than combat damage resulting from enemy action. Though some accidents were caused by the failure pilots to react properly to a critical condition, the most prevalent causes of serious accidents were weather and poor visibility. Most of the medical pilots were instrument qualified with either a standard Army qualification or a tactical qualification. However, after arriving in Vietnam units did not stress instrument flying proficiency which left the average aviator with a minima1 ability to cope with actual instrument con­ditions suddenly thrust upon him. Upon recognizing this situation corrective action was taken by the Commanding General, 44th Medical Brigade, requiring every medical aviator to practice instrument flying in conjunction with assigned missions on a monthly basis. Protective equipment for air crews was in severe shortage in 1967 as a result of additional aviation units being assigned to Vietnam. New stocks of ballistic helmets and chest protectors were not available in Vietnam or in the United States. Consequently, the 44th Medical Brigade redistributed assets throughout all medical aviation units with the guidance that the equipment would be shared by all crew members to the maximum extent. The nature of tactical operations in Vietnam established that helicopter ambulance detachments were more suitable than air ambulance companies for supporting stability operations. The company was too large for centralized operations in Vietnam and the platoons had little or no capability for sustained independent operations. Detachments proved to be much better suited for Vietnam since they were small, capable of sustained independent operations, and could be easily moved from one location to another as the tactical situation dictated. Medical Regulating Medical regulating in Vietnam was divided into the four distinct phases which had existed since the 44th Medical Brigade arrived in Vietnam in 1966. During 1967 the phases became more distinct because of increased efficiency which resulted from the application of experience to medical regulating and establishing a more definitive in-country aeromedical evacuation system. Phase I involved the evacuation of patients from the site of injury to the nearest tactical, division level (Echelon/Role II) medical treatment facility. Phase II overlapped Phase I and included the evacuation of patients from the site of injury or the division forward