From 1965 to 1970 the U.S. Army in Vietnam perfected techniques of aeromedical evacuation that helped save the lives of hundreds of thousands of Americans and Vietnamese, both friend and foe, both soldiers and civilians. Many of the techniques had been worked out in the early years of U.S. involvement in Vietnam, from 1962 to 1965, when only the 57th and 82d Medical Detachments offered air ambulance service to the U.S. and South Vietnamese Armies. After the buildup of American forces began in 1965, the helicopters, procedures, and rescue equipment were improved and sometimes tested on mass casualties. Refinements of the system were made after the Tet offensive in 1968, and Army air ambulances evacuated more patients in 1969 than in any other year of the war. Then, as it began to withdraw its forces from Vietnam, the U.S. Army set up a training program to pass on its skills in air ambulance work to the South Vietnamese Army and Air Force. Assisting the development of the helicopters and rescue equipment and acquiring the skills needed to use them demanded exceptional imagination, dedication, and compassion, both of U.S. Army medical personnel and the South Vietnamese who learned from them.

When it entered the Vietnam War the U.S. Army lacked a satisfactory aircraft for medical evacuation. As early as 1953 the Aviation Section of the Surgeon General's Office had specified the desirable characteristics of an Army air ambulance. It was to be highly maneuverable for use in combat zones, of low profile, and capable of landing in a small area. It was to carry a crew of four and at least four litter patients, yet be easily loaded with litters by just two people. It had to be able to hover with a full patient load even in high altitude areas, and to cruise at least ninety knots per hour fully loaded. But in 1962 the Army's basic utility aircraft, the UH-1B made by Bell Aircraft Corporation, still did not meet these standards. It was, however, a small craft with a low profile, and the Army's MSC pilots could console themselves with the fact that the Huey was a far better air ambulance than the one their predecessors had flown in the Korean War. It had nearly twice the speed and endurance of the H-13 Sioux, and it

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could carry patients inside the aircraft, allowing a medical corpsman to administer in-flight treatment.

In almost all other respects it was less than perfect. One of its major problems was the comparatively low power of the engine. The critical factor in planning all helicopter flights with heavy cargoes is what pilots know as "density altitude"-the effective height above sea level computed on the basis of the actual altitude and the air temperature. The warmer the air, the less its resistance to the rotor blades and the less lift they produce. Because of its lack of fixed wings, which permit a powerless glide, a helicopter whose engine quits or fails to produce adequate power at a high density altitude can easily crash. Given enough forward airspeed and height, most helicopters, including all the Huey models, can drop to the earth and still land if the power falls, using the limited lift produced by the freely-spinning rotor blades. But this maneuver, called an autorotation, is virtually impossible to execute in a low-level, hovering helicopter. A writer for the Marine Corps suggests that this explains "...why, in generality, airplane pilots are open, clear-eyed, buoyant extroverts and helicopter pilots are brooders, introspective anticipators of trouble."

Although the A- and B-model Huey engine often lacked enough power to work in the heat and high altitudes of South Vietnam, it was much stronger than earlier Army helicopter engines. A great advance in helicopter propulsion had come in the 1950s with the adaptation of the gas turbine engine to helicopter flight. The piston-drive engines used in Korea and on the Army's UH-34 utility helicopters in the 1950s and early 1960s had produced only one horsepower for each three pounds of engine weight. The gas turbine engines installed on the UH-1 Hueys, which the Army first accepted in 1961, had a much more favorable efficiency ratio. This permitted the construction of small, low-profile aircraft that was still large enough to carry a crew of four and three litter patients against the back wall of the cabin. But the high density altitudes encountered in II Corps Zone in Vietnam meant that the UH-1A and UH-1B with a full crew-pilot, aircraft commander, crew chief, and medical corpsman-often could carry no more than one or two patients at a time.

In the early 1960s, shortly after the first U.S. Army helicopters were sent to South Vietnam, the Army began to use an improved ver-sion of the UH-1B: the UH-1D, which had a longer body with a cabin that could hold six litter patients or nine ambulatory patients. The longer rotor blade on the UH-1D gave it more lifting power, but high density altitudes in the northern two corps zones, where U.S. troops did most of their fighting, still prevented Dust Off pilots from making full use of the aircraft's carrying capacity. Finally in 1967 the commander of the 4th Infantry Division registered a complaint about his aeromedical evacuation support.

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The 498th Medical Company, which served this area, had performed 100 hoist missions from July 1966 to February 1967 but had aborted 12 of them, 3 because of mechanical failures of the hoist and 9 because of the inability of the helicopter to hover. In March 1967 at Nha Trang, the staff of I Field Force, Vietnam, held a conference of various personnel involved in aeromedical evacuation in northern Vietnam. The conference noted the low engine power of the UH-1D's working in the Central Highlands, especially of those with the 498th Medical Company and the Air Ambulance Platoon of the 1st Cavalry.

In July 1967 the arrival at Long Binh of the 45th Medical Com-pany (Air Ambulance), equipped with new, powerful UH-1H's marked the end to the Huey's propulsion problem. Headquarters, I Field Force, Vietnam, soon conducted a test of the engine power of the UH-1D, the Kaman HH-43 "Husky," and the new UH-1H with an Avco Corporation T-53-L-13 engine. The study showed that the maximum load of an aircraft hovering more than about twenty feet above the ground (out of ground effect) on a normal 95º F. day in the western Highlands was 184 pounds for the UH-1D with an L-11 engine, 380 pounds for the Husky, and 1,063 pounds for the UH-1H with an L-13 engine. This meant that on such a day the UH-1D could not perform a hoist mission; the Husky could pull at most two patients.; and the UH-1H could pull five hoist patients. The L-13, rated at 27 percent more horsepower than the L-11, consumed 9 percent less fuel. The other air ambulance units in Vietnam obviously had to start using the UH-1H.

On 21 January 1968 the last UH-1D air ambulance in the U.S. Army, Vietnam, left the 57th Medical Department and became a troop transport in the 173d Assault Helicopter Battalion at Lai Khe. Now the entire fleet of air ambulances had powerful UH-1D's, solving many of the problems caused by high density altitudes, hoist missions, and heavy loads. Also, unlike most of the UH-1D's, the UH-1H's were fully instrumented for flight at night and in poor weather. They proved to be rugged machines, needing comparatively little time for maintenance and repairs. Like the earlier models, the H-models came with skids rather than wheels, to permit landing on marshy or rough terrain. The UH-1H's only important departure from the 1953 specifications of the Aviation Section was its inability to sustain flight if part or all of one rotor blade were missing. It was a single-engine craft with only two main rotor blades; the loss of all or part of one main blade would create an untenable imbalance in the propulsion system. And the Army version of the UH-1H had a flammable magnesium-aluminum alloy hull. Still, in most ways the UH-1H proved to be an ideal vehicle for combat medical evacuation.

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The terrain in Vietnam - a mixture of mountains, marshy plains, and jungles- dictated the use of the helicopter for almost all transport. The changes in the design of the UH-1 Iroquois and its equipment during the Vietnam conflict stemmed largely from the problems presented by that difficult terrain. Early in the war the 57th Detachment recognized the need for some means of getting troops up to a helicopter hovering above ground obstacles that prevented a landing. The 57th sorely needed such a device for use in heavily forested areas, where until then medical evacuations had required moving the wounded and sick to an open area or cutting a pickup zone out of the jungle. During three military operations against the Viet Cong in War Zone D from November 1962 to March 1963, the South Vietnamese Army and their American advisers became acutely aware of this problem. The thick jungles in the area made resupply and medical evacuation by helicopter extremely difficult. Some of the South Vietnamese units carried their wounded for as long as four days before finding a suitable landing area for the UH-lAs. The problem was most acute when soldiers were wounded in the first few days of an operation, before reaching their first objective. This forced the ground commander either to delay his mission while sidetracking to a pickup zone, to carry the wounded with the assault column, or to leave the casualties behind with a few healthy soldiers for protection

In attacking this problem, the armed services and their civilian contractors devised two fanciful and ultimately unsuccessful devices. Each entailed loading the helicopter while it hovered above the obstacles that surrounded the wounded below. The XVIII Airborne Corps at Fort Bragg devised a collapsible box-like platform that the ground troops were to strap to the upper reaches of a large tree. After the helicopter had dropped the platform to the soldiers on the ground, they would climb the tree, attach the platform, bring up the wounded, and wait while the helicopter moved into a hover just above the platform and the crew extended a rigid ladder four feet below the aircraft skids. Supplies would then be moved down and wounded or sick soldiers up the ladder. Tests revealed the absurdity of the device: wounded troops could hardly be moved to the top of a tree with ease, and the platform itself proved difficult to secure in the upper reaches of dense, multi-layered jungle.

A variation on this theme, the "Jungle Canopy Platform System," consisted of two stainless steel nets and a large platform. From the hovering helicopter the crew would unroll the nets onto the top of the jungle canopy, so that they intersected at midpoint; then the crew would lower the platform onto the intersection of the nets and signal the pilots to land on it. Troops and supplies could then move to and from the aircraft. The 1st Cavalry Division tested the device in Viet-

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nam during noncombat operations; actual combat reports on it could not be obtained because no unit would use it under those conditions. Without the platform the nets worked well for deploying troops but proved unreliable for other uses, such as medical evacuation. The test report concluded: "Based on commanders' reluctance to use the system, there appears to be no current requirement for the Jungle Canopy Platform System."

Despite these two failures, the Army did develop a piece of supplemental equipment for the Huey that both advanced the art of medical evacuation and placed extraordinary new demands on the air ambulance pilots: the personnel rescue hoist. The hoist was a winch mounted on a support that was anchored to the floor and roof of the helicopter cabin, usually just inside the right side door behind the pilot's seat. When the door was open, the hoist could be rotated on its support to position its cable and pulleys outside the aircraft, clear of the skids, so that the cable could be lowered to and raised from the ground. After a UH-1 was outfitted with the necessary electrical system, the aircraft crew could quickly install or remove the hoist. On a hoist mission, while the aircraft hovered, the medical corpsman or crew chief would use the hoist cable to lower any one of several types of litters or harnesses to casualties below. If a wounded soldier and his comrades were unfamiliar with the harness or litter, the crew chief would sometimes lower a medical corpsman with the device; then the hoist would raise both the medic and the casualty to the helicopter. The standard hoist eventually installed on the UH-1D/H could lift up to 600 pounds on one load and could lower a harness or litter about 250 feet below the aircraft.

As early as November 1962 the Surgeon General's Office had said that the Army's air ambulances needed a hoisting device. Under further pressure from the 57th Medical Detachment, the Surgeon General had the Army contract with Bell Aircraft Corporation and the Breeze Corporation for the personnel rescue hoist. The U.S. Army Medical Test and Evaluation Activity experimented with the new hoist at Fort Sam Houston in April and May 1965 and recommended that it be adopted with minor modifications.

In May 1966 the first hoists began arriving in Vietnam, and on 17 May, Capt. Donald Retzlaff of the 1st Platoon, 498th Medical Company, at Nha Trang, flew the first hoist mission in Vietnam. But within a week the hoist proved unreliable, prone to jam and break during a lift. After being grounded for two months for repairs and redesigning, the hoist, now modified, went back into service. It continued to be a maintenance problem for the rest of the war, but it functioned well enough to save several thousand lives.

Although air ambulance pilots began to use the hoist in Vietnam in August 1966, their commanders soon complained about the ex-

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traordinary hazards it brought to their work. The UH-lD was already burdened with a heavy single sideband (high frequency) radio and a navigation system; the extra weight of the hoist com-pounded the problem of the underpowered L-11 engine. Since the crew chief worked on the same side of the aircraft as the hoist, the helicopter was heavily overweighted on one side, and a strong gust of wind from the other side could endanger the craft's stability. The operation also demanded great strength and concentration of the pilots, especially if winds were gusting or if trees or the enemy forced a downwind or crosswind hover. The danger of mechanical troubles was obvious: almost by definition no emergency landing site was nearby, and even if it were, the ship usually was hovering at a height that precluded an autorotational touchdown in an emergency.

Adding to the tenseness of such a mission, the crews knew that the most vulnerable target in the war was a helicopter at a high hover. The precautions that had to be taken against sudden enemy fire proved especially taxing on the pilots. The men in the rear of the aircraft cabin would set the intercom switches on their helmets to "hot mike," allowing them to communicate with the rest of the crew without depressing their microphone buttons. While working the hoist or putting down suppressive fire the crew chief and medical corpman could keep the pilot informed of his nearness to trees or other hazards. While listening to this chatter, the pilots also had to be in radio contact with the people on the ground. In December 1966 an officer of the 1st Cavalry Division in the Central Highlands complained:

We are very dissatisfied with the hoist and any of its associated equipment. Mainly because we've been shot up pretty badly twice during Operation THAYER while in position for hoist extraction. Fortunately so far we've had only two crew members slightly wounded. On both occasions the VC haven't fired a shot in the last ten to thirty minutes. Then, just as the hook enters the pickup site, he cuts loose. He is so close to our troops on the ground ... the armed escort ships can't fire for fear of hitting our own troops.

The hook on the end of the hoist cable could accept several types of rescue devices. A traditional rescue harness worked well for pulling up lightly injured soldiers, but it proved difficult and often impossible to lower through the thick upper vegetation of Vietnam's forests and jungles. Seriously wounded soldiers usually had to be placed in the rigid wire Stokes litters and raised horizontally; but this too caused problems in thick jungles and forests. For the lightly wounded and the less seriously wounded, the air ambulances almost always used a device designed early in the war- a collapsible seat called the forest penetrator, which could easily be lowered through dense jungle canopy. Developed by the Kaman Corporation, the penetrator weighed twenty pounds, and had three small, paddle-like seats that

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could be rotated upwards to lock into place against the sides of the penetrator's narrow, three-foot long, bullet-shaped body. Once to the ground, the seats could be lowered and the wounded strapped on with chest belts. Although the version accepted by the Army had no protection for the casualty's head as he was raised up through the foliage, this seldom proved a problem. The first eight forest penetrators arrived in Vietnam in mid-June 1966, but extensive testing of the device with the new hoists was delayed until September and October. Medical personnel then found the device satisfactory and it became the normal means of lifting a conscious casualty. Unconscious soldiers were often lifted head up, in a device known as the semi-rigid litter: a flexible canvas jacket with a lining of wood straps and a rigid head cover.

Even when the penetrator was used, a hoist mission took considerably longer than usual at the pickup zone. Pilots flying the first missions found their ships often subject to accurate enemy fire. On 1 November 1966 the 283d Detachment at Tan Son Nhut got a request from a ground unit not far outside Saigon's noise and bustle. The unit had casualties deep under the jungle and needed a hoist to get them out. In the 283d, Capt. James E. Lombard and 1st Lt. Melvin J. Ruiz had the only ship fitted with a hoist.

As soon as they left the ground at Tan Son Nhut they radioed the ground unit and asked whether it had any gunships standing by or had asked for any. The unit answered that it had requested them but had no idea how long they would take getting there. Three minutes later Lombard and Ruiz arrived over the pickup site. Lombard told the troops on the ground that he would have to have gunship support before he could land. He radioed a gunship unit at Bien Hoa, a five minute flight away, and asked them to launch a team to cover his mission. He was told there would be a thirty minute delay. The ground unit commander than started a sales pitch: there had been one sniper, but they had got him, the area was secure now, they had two critically wounded. Lombard agreed to come down.

The ground unit popped a smoke grenade, and the Dust Off ship came to a hover over the spot where wisps of colored smoke drifted up through the trees. The crew chief played out the hoist cable. The forest penetrator was ten feet below the skids when an automatic weapon opened up on the helicopter from the right side. Bullets whined and zinged through the aircraft, and the pilot's warning lights lit up like a Christmas tree. Lombard broke off the hover. The hydraulics were gone and the crew heard crunching and grumbling sounds from the transmission. They headed east toward a safe haven at Di An, a four minute flight away. Suddenly the engine quit. Luckily within reach of their glide path lay an open area to which they shot an autorotation. With the controls only half working, Lombard had to make a running landing, skidding along the ground. The ship tipped

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well forward on its skids then rocked back to a stop. The engine compartment was on fire. The crew got out as fast as possible, the pilots squeezing between the door frame and their seats' sliding armor side plates, which were locked in the forward position. They started to run from the aircraft when they realized that their rifles and ammunition were still inside. The medical corpsman dashed back inside, grabbed the rifles and bandoliers, jumped back out, and distributed the arms.

They looked around and decided that they had overflown the enemy, who now separated them from the friendly unit with the casualties. Rather than head into a possible ambush, they started toward a knoll in the direction of Lon Binh. Unknown to them another platoon of the friendly company was out on a sweep headed in their direction. On the ground the crew was completely out of their environment. Their loaded M16's cocked on automatic, they were ready to shoot the first blade of grass that moved. Suddenly they heard the thump, thump, thump of troops running toward them. They stopped, waited, then saw U.S. troops coming at them through the bush.

They all went back to the landing zone, where they set up a small defensive perimeter. Later that afternoon, the platoon that had called in the request cut its way out of the jungle and joined them. Its two wounded had died on the way out. The company commander radioed Di An and asked its mortars to start laying a protective barrage around the perimeter. The first salvo landed on the company and wounded many of them. The commander radioed for another Dust Off. Two hours later as dusk approached, a Dust Off ship from the 254th Detachment flew in with a gunship escort. In several trips it evacuated nineteen wounded soldiers, the two dead, and the crew from the 283d. Lombard and Ruiz had flown the first of many hoist missions that resulted in the downing of an air ambulance. But the hoist had clearly added a new dimension to utility of the helicopter in Vietnam. Despite the new danger it brought to their work, the air ambulance crews responded with courage and dedication.

Air ambulances received their missions either aloft in the aircraft, at the ambulance base, or at a standby base, usually near or at a battalion or brigade headquarters. The coverage given by the ambulances was either area support (to all allied units in a defined area) or direct support (to a particular unit involved in an operation). Direct support, in effect, dedicated the aircraft to a particular combat unit, and it usually relieved the aircraft commander of the need to receive mission authorization from his operations officer. Both air ambulances organic to combat units and nonorganic aircraft flew direct support missions.

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Most air ambulance missions, however, originated during area support. An American or allied patrol would take casualties, usually in daylight, from enemy sniper fire, mines, or other antipersonnel devices. The patrol commander and medical corpsman would decide whether the casualties needed to be evacuated by helicopter. If a Dust Off or Medevac aircraft were needed, the patrol would, if its radio were powerful enough, send its request directly to the air ambulances or their operations control. If this were not possible, the patrol would use its tactical radio frequency to send the request back to its battalion headquarters. Whichever method was used, the request had to contain much information: coordinates of the pickup site, the number and types (litter or ambulatory) of patients, the nature and seriousness of the wounds or illness, the tactical radio frequency and call sign of the unit with the patients, any need for special equipment (such as the hoist, whole blood, or oxygen), the nationality of the patients, visual features of the pickup zone (including any smoke, lights, or flares to be used by the ground unit), the tactical security of the pickup zone, and any weather or terrain hazards. The first four elements were critical: with them a mission could be flown; without them no air ambulance could guarantee a response.

Two elements of any request were open to considerable interpretation by the ground commander and his medical corpsmen: the seriousness of the medical problem and the security of the pickup zone. Three levels of patient classification were used: urgent, priority, and routine. Urgent patients were those in imminent danger of loss of life or limb; they demanded an immediate response from any available air ambulance. Priority patients were those with serious but not critical wounds or illness; they could expect up to a four-hour wait. In theory a medical corpsman had to ignore the suffering of a patient in determining his classification: a soldier in great pain, with a foot mangled by a mine, warranted, if his bleeding were stanched, only a priority rating. In practice, despite the considerable efforts of aeromedical personnel, any patient bleeding or in great pain usually received an urgent classification. just as many patients were overclassified, many dangerous pickup zones were reported as secure, and this too was understandable. Although some air ambulance units tried to fight the policy, Army doctrine limited the ground unit's responsibility in reporting on a pickup zone: if the unit's soldiers could safely stand up to load the casualties, the pickup zone could be reported as secure. So the air ambulance crew could never be sure that the airspace more than ten feet above the ground would be safe. It was highly important for an aircraft commander approaching a pickup zone to establish radio contact with the ground unit and learn as much as possible about enemy forces near the zone.

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If the ground unit with the patient had to send its evacuation request through its battalion headquarters, the headquarters would make sure the request had all essential information and then either send it directly over the established air ambulance radio frequency or, if it lacked the proper radios, forward it to brigade headquarters, who almost always could communicate directly with the air ambulance operations officer.

Once an air ambulance received an urgent request, its personnel dropped any priority or routine tasks and headed toward the pickup zone. The aircraft commander performed a variety of duties of such a mission. He supervised the work of the pilot and two crewmen, and worked as copilot and navigator. En route he monitored both the tactical and air ambulance frequencies, and talked to the ground unit with the patient. Once over the pickup zone, he surveyed the area and decided whether to make the pickup, with due regard to urgency, security, weather, and terrain. If he decided to land he had to choose directions and angles of approach and takeoff. If problems developed at the pickup zone he had to decide whether to abort the mission. Once the pickup was made, he had to choose and receive confirmation on the suitability of a destination with medical facilities. He usually sat in the left front seat, leaving the right seat to the pilot, who needed a view of the hoist on the side and the flight control advantages of the right side position. Usually the commander left the en route flying to the pilot, but sometimes flew the final approach and the takeoff, especially at an open pickup zone. During a hover on a hoist mission he and the pilot alternated on the controls every five minutes.

This practice of flying with two pilots originated in the early days of U.S. military involvement in Vietnam. Since the Korean War, helicopter detachments had flown with one pilot in the cockpit. The transportation aviation units which were in Vietnam when the 57th medical detachment deployed there in 1962 already had made it a policy to fly their H-21's with two pilots in the cockpit. There were convincing reasons. If a solo pilot were wounded or killed by enemy gunfire his crew and ship would probably be lost, but a second pilot could take over the controls. A solo pilot also stood a good chance of getting lost over the sparsely populated Vietnamese countryside, where seasonal changes in precipitation produced great changes in the features of the terrain, making dead reckoning and pilotage difficult even for a pilot with excellent maps and aerial photographs. A second pilot could act as a navigator en route to and from a pickup zone.

The 57th quickly learned the value of two-pilot missions and asked for authorization to fly them. The denial they received referred to the official operator's manual for the UH-1, which said that the helicopter, although equipped for two pilots, could be flown by one. Nevertheless, with seven aviators and only four aircraft, and one of those

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usually down for maintenance, the 57th usually flew their missions with two pilots up front. All the air ambulance units that followed adopted this practice, and eventually they obtained authorizations to do so.

Besides the two pilots, an air ambulance usually carried a crew chief and medical corpsman. The crew chief's most important preflight duty was preventive maintenance: keeping the aircraft flight-worthy through proper and timely inspections and repairs. He also had to make sure that the aircraft had all essential tools, equipment, and supplies on board. The medical corpsman's only vital preflight duty was to supply the craft with the small amount of medical supplies that could be used in the short time taken by most evacuation flights: a basic first aid kit, morphine, intravenous fluids, basic resuscitative equipment, and scalpels and tubes for tracheostomies. At the pickup zone the crew chief and corpsman often worked together to load the casualties. If the hoist had to be used, one of them would operate it on the right side of the aircraft while the other stood in the opposite door, armed with a rifle to suppress enemy fire and to see that the aircraft stayed at a safe distance from obstacles. Once the patients were loaded, the crew chief helped the corpsman give their medical aid.

The standard operating procedure of an air ambulance unit usually required one aircraft crew to be on alert at all times in "first up" status, ready to respond immediately to an urgent request. Like all ambulance crews, the men sprang into action as soon as the siren in their lounge went off. Most units practiced often to cut the precious minutes needed to get their aircraft, warm the engine, and lift off. Many could get off in less than three minutes, unless the unit commander demanded a certain amount of preflight planning. Once aloft, the aircraft commander would open his radio to the Dust Off frequency and receive his assignment from the radio operator back at the base.

He then turned the ship toward his objective, and at some point en route switched to the tactical frequency of the ground unit with the casualties. This allowed him to reassure the unit that help was on the way, assist the medical aidman on the ground in preparing for the evacuation, and check with the ground commander on dangers from the terrain, weather, or enemy. The method of approach to the pickup zone varied. Some units specified a standard approach, such as a steep, rapid descent from high altitude. But some of the most respected commanders believed in letting the aircraft commander use the many variables of the situation to determine the fastest, safest means of getting down to the wounded.

On the ground the medical corpsman and the crew chief usually left the aircraft, put the patients on litters, and loaded them onto the ship. About half the time the casualty would not have received any medical treatment before he reached the air ambulance. When the hoist first went into operation, medical personnel publicized it and

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offered training in its use to ground combat and medical personnel. This reduced the likelihood that the medical corpsman would have to be lowered during a hoist mission to help load the patients, allowing either the corpsman or the crew chief to put down suppressive fire while the other lowered and raised the hoist cable. A few units, especially the organic air ambulances, routinely carried a fifth crewman during a hoist mission-a gunner to protect the ship, its crew, and its casualties.

Once the patients were aboard and safely secured, the pilot took off. The corpsman tried to find and treat the most serious patient, and report the nature of the problem to the aircraft commander. The decision on where to fly the patients then entered the medical regulating network. The aircraft commander radioed the nearest responsible medical regulating officer, who confirmed or altered the commander's choice of destination. This choice was based on the commander's knowledge of the specialized surgical capabilities of the hospitals in his area and on his daily morning briefing as to the current surgical back- log in these hospitals. Standard practice was to take the most serious patient directly to a nearby hospital known to have all the equipment and care he immediately needed. If that hospital then determined that he needed more sophisticated care than it could offer, he was backhauled as far to the rear as possible. A secondary objective was to take the patient to the hospital in the area that had the smallest surgical backlog, to reduce the time between wounding and the start of surgery. The supporting medical group in each area of operations usually assigned, at least after 1966, a forward medical regulating officer to each combat brigade headquarters, and those regulators kept aware of the most current surgical backlogs in all nearby hospitals. Since they had more current information on surgical backlogs than the aircraft commanders, the regulators had the authority to change the commander's choice of destination.

Since most pickups were made within range of a surgical, field, or evacuation hospital, the ambulances usually overflew the battalion aid stations and division clearing stations, which could offer only basic emergency treatment that was already available on the helicopter, and deposited the patients at a facility that offered definitive resuscitative treatment. Although the less serious patients often found themselves overevacuated, the practice saved thousands of patients who demanded immediate life-saving surgery.

The effective functioning of an air ambulance depended heavily on its bank of four radios: FM, UHF, VHF, and single sideband (high frequency). The FM radio contained the frequencies of the Dust Off operations center, the tactical combat unit, and most hospitals. VHF and UHF were infrequently used. And the single sideband contained the medical regulating frequencies. The ambulance would

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usually stay on its Dust Off frequency for flight following until he approached the pickup zone, when it would switch over to the tactical frequency of the unit with the casualties. After the pickup the ambulance would switch briefly to the frequency of the forward medical regulator, which was closely monitored by his group medical regulating officer. Then the ambulance would switch back to the Dust Off frequency for flight following until it approached the hospital, when it would switch to the hospital's frequency, usually on the FM radio, to warn the doctors of the approach.

Although most of these procedures for area support missions also applied for direct support missions, there were a few important differences. Early in the war the 57th and 82d Medical Detachments, under the operational control of aviation battalions in the Delta, flew many such missions. The battalions would warn the detachments of planned airmobile operations and their requirements for aeromedical support. During a combat insertion, one or more Dust Off ships orbited near the landing zones at two or three thousand feet, out of effective small arms range, with the pilots monitoring the helicopter- to- ground talk on the FM band, helicopter gunship talk on UHF, and any airplane- to- gunship talk on VHF. If a patient pickup became necessary during a ground fight, the command- and-control helicopter of the flight would designate two gunships to accompany the Dust Off ship into and out of the area. The gunships would switch over to the Dust Off frequency and make a slow pass over the area to draw fire, find the source, and suppress it. Then Dust Off would go in covered by the gunships. Later in the war organic air ambulances sometimes accompanied the flight of transport helicopters into the landing zones, and stood by waiting for casualties. More often they orbited the area of operations or stood by at the nearest battalion or divisional clearing station. While affording excellent aeromedical coverage for the supported unit, direct support missions limited the ability of the air am-bulances to respond to emergencies elsewhere.

All helicopter pilots in Vietnam had to cope with problems for which they might be unprepared or poorly equipped. By the nature of their work, air ambulance pilots experienced such problems more often than transport and gunship pilots. Except for the Medevac helicopters of the 1st Cavalry Division, the air ambulances carried no armament heavier than the pilots' M16 rifles, and most of the air ambulance missions were executed by a single ship rather than a well-prepared team, known as a "gaggle." Soldiers were shot and injured without regard to the terrain or weather, and the air ambulances were

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expected to make their way to the casualties as soon as possible. The poor navigation equipment on the Hueys and the shortage of instrument- trained pilots early in the war exacerbated the difficulty of coping with South Vietnam's weather. While maintenance problems. plagued all the helicopter crews in South Vietnam, the special demands of air ambulance work, such as hoist missions, compounded the problems. Speed was important to inbound as well as outbound flights, making stops for refueling a dangerous luxury. While few of these problems could be totally solved, the air ambulance units often found ways to minimize them. When refueling during a mission could not be avoided, the unit often called ahead to an established fuel depot and made an appointment for refueling at an en route landing strip. When a unit was jointly based with a gunship battalion, arrangements could sometimes be made for an armed escort, especially on a hoist mission.

One of the problems that persisted throughout the war was the expectation that the air ambulances would transport the dead. Nothing in USARV regulations authorized the ambulances to carry the dead; but both ARVN and American soldiers expected this service. Nonmedical transport helicopters and gunships often evacuated both the dead and the wounded. If Dust Off ships had routinely refused to carry the dead even when they had extra cargo space, the combat units might have decided to rely exclusively on their transports and gunships to evacuate both the wounded and the dead, resulting in a marked decline in the care provided the wounded. Combat operations might also have suffered, for ARVN soldiers often would not advance until their dead had been evacuated. So most air ambulance units practiced carrying the dead if it did not jeopardize the life or limb of the wounded.

The language barrier also hampered the work of the air ambulance crews. Almost one-half the sick and wounded transported by the air ambulances could not speak English, and the crews usually could not speak enough Vietnamese, Korean, or Thai to communicate with their passengers. Early in the war USARV regulations prohibited a response to an evacuation request unless an English-speaking person were at the pickup site to help the air ambulance crew make its approach and evaluate the patients needs, or unless the requesting unit supplied the air ambulance an interpreter. But the scarcity of good interpreters in the South Vietnamese Army meant that Dust Off evacuated many Vietnamese whose needs were only vaguely understood. Even when the air ambulance unit shared a base with an ARVN unit, the language problem proved serious. A former commander of the 254th Detachment remembered such an experience:

The periodic attacks on the airfield were experiences to behold. Trying to get

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from our quarters to the airfield was the most dangerous. The Vietnamese soldiers responsible for airfield security didn't speak English and with all the activity in the night-vehicles driving wildly about, people on the move, machine gun fire and mortar flares creating weird lighting and shadows - the guards were confused as to who should be allowed to enter the field and who, had no reason to enter. If one could get to the field before the road barriers and automatic weapons were in place all was well. Later than that, one might just as well not even try to get on the field. We had several instances of the guards turning our officers back at gunpoint! We tried to get ID cards made but the Vietnamese refused to issue any cards. We sometimes felt we were in more danger trying to get to the airfield during alerts than we were picking up casualties.

The pilots and crews also had to contend with the ever-present danger of a serious accident. Until later in the war most of the pilots lacked the instrument skills needed to cope with the poor visibility typical of night missions and weather missions. The DECCA navigation system installed in the UH-IB's and UH-ID's proved virtually useless early in the war. More pilots died from night- and weather-induced accidents than from enemy fire.

To cope with this danger, most of the pilots new to Vietnam quickly learned the virtue of a cool head and even a sense of humor. One former commander of a unit recalled the day that his alert crew at Qui Nhon received a request for the urgent evacuation of an American adviser who had fallen into a punji trap. (Such traps held sharpened wood stakes driven into the ground with the pointed ends facing up, often covered with feces, onto which the victims would step or fall.) It was late afternoon, approaching dusk, but Maj. William Ballinger and his pilot scrambled on the emergency call. They flew down the coast then turned inland to the pickup point. The casualty turned out to be a Vietnamese lieutenant with no more than a rash. Since they were already there, the crew picked him up and started back to Qui Nhon.

On the way down the weather had turned bad, and when they headed north rain began. Night fell and the rain grew worse. Wondering whether they should set down or continue, they called the Qui Nhon tower operator and asked for the local weather. The operator reported a 3,000 foot ceiling and five miles visibility. The pilots thought they were in the middle of an isolated storm and they expected to break out shortly. After flying on and still not clearing the storm, they radioed the tower again and got the same report. Now their visibility was so bad they had to drop low and fly slowly up the beach. As they passed a point they knew to be only five miles from Qui Nhon, with the rain still pelting down, they again radioed the tower operator and got the same report: ceiling, 3,000 feet and five miles visibility. Ballinger asked for the source of the weather report,

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and the operator replied, "This is the official Saigon forecast for Qui Nhon." Ballinger told the man to look outside the tower and then tell him what the weather was. The operator replied, "Oh, sir, you can't see a damned thing out there." The pilots had to fly low and slow to the base and were relieved when their skids touched the runway. Only then could they indulge in a good laugh.

Night missions quickly became a major problem in themselves. The difficulties of such missions in a rural society were obvious: roads and population centers rarely were well lighted enough to aid in navigation to a pickup zone; terrain, especially in mountainous areas, became a great danger to ambulances that lacked adequate navigation instruments; and adequate lighting at the pickup zone rarely existed. In the dry season a landing light reflecting off the dust thrown up by the rotorwash could quickly blind a pilot just before touchdown. Throughout the war a considerable number of pilots and commanders refused to fly night missions or else flew them only for urgent cases. Others, however, thought that night flying offered many advantages that at least compensated for its problems. A few, such as Patrick Brady, even preferred night missions.

Early in the war the 57th Detachment routinely flew night evacuations, so much so that at one staff meeting General Stilwell, the Support Group commander, asked why the 57th could fly so well at night when few others could or would. He quickly learned that one of the aids used by the 57th was the AN/APX-44 transponder, which allowed Air Force radar stations to follow the aircraft at night or in bad weather and vector them to and from a pickup site. Early in 1964 General Stilwell charged the medical detachment with the task of conducting a test on the feasibility of making combat assault insertions at night. In the Plain of Reeds the pilots experimented with parachute flares, tested the available radio and navigation equipment, and concluded that although night missions were suitable for medical evacuation they were not suitable for combat assaults.

Night missions called for a few specialized techniques. En route at night to a pickup zone an air ambulance would fly with either its external rotating beacon or position lights on. Once below 1,000 feet on its approach to the zone, it would douse these lights and dim its interior instrument panel lights as soon as the ship drew within range of enemy fire. About five hundred feet from the touchdown, the pilot would briefly turn on his landing light to get a quick look at the pickup zone. Then he would douse the landing light until the last 200 feet of the approach. In an article in Army Aviation Digest, Capt. Patrick Brady recommended a final descent at right angles to the ground unit's signal, since a pilot could see much better through the open side window than through the windshield, especially one covered with bulletproof Plexiglas. On the ground the soldiers would

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use flashlights, small strobe lights, or vehicle headlights to mark the pickup zone. Some lights, such as flares, burning oil cans, and spotlights, tended to blind the pilot on final approach. A pilot in contact with soldiers on the ground would try to warn them of this early enough to allow a change of lights if necessary. On takeoff the lighting sequence on the ambulance would be reversed.

While night magnified the dangers of weather and terrain, Captain Brady correctly noted that it reduced the danger of enemy fire. Although the enemy would always hear the approach of the noisy Huey, he could rarely see it in the dark. An exhaust flame or the moonlight would sometimes betray a blacked-out aircraft, but the enemy could rarely direct accurate fire at the ship. Only night hoist missions allowed the enemy to get an accurate fix on an air ambulance, and the extreme hazards of hovering an aircraft close to ground obstacles at night made even the best air ambulance pilots avoid such missions unless a patient were in imminent danger of loss of life.

A scarcely less dangerous form of night mission, a night pickup in the mountains in bad weather, was also beyond the capacity of most air ambulance pilots. Brady, however, developed a technique for such a mission that made it feasible if not safe for a highly competent pilot. One night in the fall of 1967, in Brady's second tour in Vietnam, his unit, the 54th Detachment at Chu Lai, received a Dust Off request from a 101st Airborne Division patrol with many casualties in the mountains to the west. Heavy rains and fog covered the area, and after a few attempts Brady decided that he would never get to the casualties by trying to fly out beneath the weather. He would have to come down through the fog and rain with the mountains surrounding him. He took his aircraft up to 4,500 feet and vectored out to the mountains on instruments. As he approached the mountains he took his ship up to 7,000 feet. From his FM homing device he knew when he was directly over the pickup site. Then he radioed an Air Force flare ship in the area and asked its pilot to meet him high above the pickup zone and foul weather below. The Air Force pilot agreed and at Brady's suggestion took his plane to 9,000 feet directly overhead and began to drop basketball-size parachute flares, larger and brighter than the Army's mortar and artillery flares. Brady picked one out and started to circle it with his ship, dropping lower and lower into the fog, rain, and mist. The flare's brilliant light reflecting off the fog and rain wrapped the Dust Off ship in a ball of luminous haze. Brady dropped still lower, gazing out of his open side window, alert for the silhouette of crags and peaks. Suddenly the ship broke through the clouds. Brady recognized the signal lights of the unit below him, and settled his ship onto the side of the mountain. He picked up the casualties and took off. Now that he was under the clouds he could see better, and he managed to fly back to Chu Lai at low level. Back at

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the base the rain was so heavy he could hardly see to land. While the patients were being unloaded, and the ship readied for a second trip out to the mountains, the 54th's commander, Lt. Col. Robert D. McWilliam, went out to Brady's ship and through the left window and asked the copilot how it was going. The young lieutenant just shook his head and said he couldn't believe it. Knowing that the man was gung-ho, McWilliam thought he would not leave the ship until the mission was over. He asked him, "Would you like me to take over for you?" Instantly the man was out of the aircraft, and McWilliam took his place.

As he and Brady flew back to the mountains, the ground controller vectored them into the middle of the thunderstorm. Lightning flashed around them, but Brady flew on to the pickup site, where he again managed to get down through the clouds using the Air Force flares. But this time he could not find the 101st patrol before the flares burnt out. Flying around in the dark only a few hundred feet off the valley floor, he and McWilliam strained to see the signal light of the beleaguered unit. just as they saw it, an enemy .50-caliber machine gun opened fire on them. Brady jerked his craft around to avoid the fire, and he and McWilliam lost the signal. Having lost the enemy fire as well, they circled for several minutes trying to find the signal again Suddenly the .50-caliber opened up at them again, and Brady knew that the U.S. forces had to be near. He managed to stay in the area this time, and soon the signal light flashed again. The Dust Off ship landed and flew out more casualties.

Dust Off pilots often used Army artillery flares to light their pickup zone. But Major Brady had performed a far from standard night mission, using Air Force flares to descend through fog and rain in the mountains. In an article he wrote for Army Aviation Digest, Brady noted that such a mission did have its dangers, especially if the flares burned out before the ship had broken through the clouds. He wrote: "Nothing is more embarrassing than to find yourself in the clouds at 1,500 feet in 3,000-foot mountains and have the lights 90 out." The pilot's only recourse then was to climb as steeply as possible; if he tried to maintain position while waiting for another flare to come down, he ran the risk of drifting into the side of a mountain. Brady had demonstrated two qualities-imagination and courage-that helped many Dust Off pilots cope with the challenges of combat aeromedical evacuation.

Although pilot error and mechanical failure accounted for more aircraft and crew losses in Vietnam than enemy fire, the air ambulance pilots worried more about the latter danger than the other

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more controllable ones. Once the buildup got under way in 1965, any air ambulance pilot who served a full, one-year tour could expect to have his aircraft hit by the enemy at least once. When hoist missions became a routine part of air ambulance work in late 1966, enemy fire became especially dangerous. Although the pilots devised ways of reducing the danger, such efforts barely kept pace with improvements in enemy weaponry and marksmanship.

Before the buildup began the pilots had little more than homemade weapons to fear. In 1962 and 1963 the 57th Air Ambulance Detachment suffered less from enemy fire than the nonmedical helicopter units, partly because of the limited number of missions the unit flew in this period. The unit's five ambulance helicopters flew a total of only 2,800 hours those two years, and no pilot or crewman was wounded or killed in action. To get their minimum flight time and provide themselves some insurance against a lucky enemy hit, the pilots started flying two ships on each mission. But once the buildup got under way in late 1964 the unit went back to single ship missions, and most of the division and nondivisional air ambulance units that later joined them also followed this practice.

The return to single-ship missions demanded a few unorthodox procedures. International custom and the Geneva Conventions, which the United States considered itself bound to observe, dictated that an ambulance not carry arms or ammunition and not engage in combat. But in Vietnam the frequent enemy fire at air ambulances marked with red crosses made this policy unrealistic. Early in the war the crews started taking along .45-caliber pistols, M14 rifles, and sometimes M79 grenade launchers. The ground crews installed extra armor plating on the backs and sides of the pilots' seats. The hoist missions, introduced in the late fall of 1966, produced a high rate of aircraft losses and crewmember casualties. Although at this stage of the war gunship escorts for air ambulance missions were still hard to arrange, only the Air Ambulance Platoon of the 1st Cavalry responded to the new danger by putting machine guns on their aircraft. At first the unit simply suspended two M60's on straps from the roof over the cargo doors. Later they installed fixed mechanical mountings for the guns. A platoon aircraft also usually carried a gunner as a fifth crewmember to handle one of the M60's. Later in the war many of the air ambulance units, both divisional and nondivisional, tried to arrange gunship escorts, especially for hoist missions, to pickup zones that had been called in as insecure. Throughout the war, however, such escorts proved hard to obtain, because aeromedical evacuation was always a secondary mission for a gunship in a combat zone.

None of these defensive measures reduced the rate of air ambulance losses in the war; they only prevented it from approaching a prohibitive level. Most of the Viet Cong and North Vietnamese

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soldiers clearly considered the air ambulances just another target. A Viet Cong document captured in early 1964 describing U.S. helicopters read: "The type used to transport commanders or casualties looks like a ladle. Lead this type aircraft I times its length when in flight. It is good to fire at the engine section when it is hovering or landing." Fortunately Viet Cong weapons early in the war made a helicopter kill virtually impossible. Late in 1964, however, the North Vietnamese began to supply the Viet Cong with large amounts of sophisticated firearms: Chinese Communist copies of the Soviet AK47 assault rifle, the SKS semiautomatic carbine, and the RPD light machine gun. The introduction of these new enemy weapons in 1965-66 and of the hoist missions in late 1966 caused a dramatic increase in 1967 in the rate of enemy hits on air ambulances. Only in April 1972, however, when the United States was well along in turning the war over to the South Vietnamese, did the air ambulance have to contend with the Soviet SA-7 heat-seeking missile. This antiaircraft device was about five feet long, weighed thirty-three pounds, and had a range of almost six miles. A pilot had little warning of the missile's approach other than a quick glimpse of its white vapor trail just before it separated the tail boom from his aircraft. This weapon downed several air ambulances in the last year of U.S. participation in the war.

The missile also disrupted the most elaborate effort the Army made during the war to reduce the losses of air ambulances: a change of their color. The 1949 Geneva Conventions did not require that air ambulances be painted white, and for their first nine years in Vietnam the Army's air ambulances were the standard olive drab, medically marked only by red crosses on small white background squares. Early in the war many of the pilots thought that the crosses improved the enemy's aim at their ships, and the unit commanders had to resist pressure to remove the markings. Arguing that they would be unable to keep aircraft that looked like transports dedicated to a medical mission, the commanders prevailed, and the red crosses remained for the rest of the war.

By mid-1971, however, the high loss rate for air ambulances over the last six years produced much doubt about the olive drab color scheme. Believing that making the aircraft more distinctive might be the answer, the Army Medical Command in Vietnam secured approval. in August to paint some of its aircraft white. The Command also was allowed to try to persuade the enemy that the white helicopters were for medical use only and should not be fired on. Thousands of posters were to be distributed and millions of leaflets dropped over enemy-held territory. The most elaborate leaflet read:

Some new medical helicopters not only have Red Cross markings on all sides but they also are painted white instead of green. This is to help you recognize them

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better than before in order to give the wounded a better chance to get fast medical help. Like all other medical helicopters, these new white helicopters are not armed, do not carry ammunition, and their only mission is to save endangered lives without distinction as to civilians or soldiers, friend or foe.

MEDICAL HELICOPTERS ARE USED FOR RESCUE MISSIONS AND THEY ARE NOT ENGAGED IN COMBAT. YOU SHOULD NOT FIRE AT THEM.

An enemy soldier still intent on bringing down any U.S. helicopter would now find the white helicopters excellent targets against a background of forests, hills, or mountains. All armaments now had to be removed from the ambulances, and gunship escorts could no longer furnish close support. Unless the information campaign were successful, the air ambulances would encounter more rather than less resistance. But the risk, while undeniable, seemed justifiable in view of combat loss statistics: from January 1970 through April 1971 the air ambulance combat loss rate was about 2.5 times as great as that for all Army helicopters. Something had to be done.

The test program for white helicopters, begun on 1 October 1971, soon produced encouraging preliminary results. In November the Army medical command received permission to paint all of its remaining fifty air ambulances white. However, the drawdown of U.S. forces was now in full swing. The test, which terminated the following April, had begun too late in the conflict and with too few helicopters to produce conclusive results. The white helicopters at least had not proven any more dangerous than those painted olive drab. On 28 April 1972 the MACV Surgeon recommended to the Surgeon General that white helicopters continue to be used for medical evacuation by the dwindling number of Army units in Vietnam.

But in the same month the enemy's introduction of the heat-seeking SA7 missile to South Vietnam put Army medical planners in a new quandary. To navigate properly, most air ambulance pilots could not fly to and from a pickup zone at altitudes low enough to enable the enemy on the ground to discern the white color and the red crosses. Except at the pickup zone, the white ambulances were as vulnerable as any other Army olive drab aircraft. Between 1 July 1972 and 8 January 1973 the enemy fired eight heat-seeking missiles at white air ambulances. The only protection against the SA7 was a new paint that reflected little of the engine's infrared radiation but dried to a dull charcoal green. In January 1973 USARV/MACV Support Command directed that all U.S. Army air ambulances in Vietnam be painted with the new protective paint. Research began on a white protective paint, but before any significant progress could be made the war ended.

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By early 1968 the basic techniques of aeromedical evacuation developed during the Vietnam War had been perfected. The helicopters, rescue equipment, and operating procedures were now ready for a full test of their utility. Their first trial came in February 1968 when the enemy launched a coordinated assault on allied bases and population centers throughout the country. With little warning the Dust Off system had to cope with thousands of casualties in all four Corps Zones. The enemy offensive resulted in more helicopter ambulances being shipped to South Vietnam, and by January 1969 the system was only one platoon short of its peak strength. That year Dust Off carried more patients than in any other year of the war. Although the fighting then began to wane for U.S. forces, the Dust Off system still had to face two more ordeals: large operations in Cambodia and Laos. The final years of Dust Off in Vietnam proved to be the most difficult, and they earned helicopter evacuation a lasting place in modern medical technology.