No missions were attempted on April 17, but the next day the effort resumed. Captain Don B. Jensen’s Hercules began taking multiple hits as the airplane approached the drop zone. The right wing caught fire; one engine was shot out and another set afire; all communications were lost. Jensen managed to jettison the load and steer the airplane away from An Loc to a crash landing in a swamp near Lai Khe. After helping each other from the wreckage, the crew members were picked up by U.S. Army helicopters. Jensen’s C-130 was the third transport to be lost at An Loc; the other two were VNAF C-123s.

After the initial low-level airdrops failed, the airlifters decided to try a new tactic. Since 1969, C-130s in Vietnam had been using the MSQ-77 Skyspot ground radar to deliver 15,000-pound BLU-82 bombs. The C-130 bombers had proved quite accurate–as accurate as any airplanes dropping bombs in Southeast Asia. Perhaps the ground radar could be used to direct cargo drops as well. The new technique was designated GRADS, for ground radar aerial delivery system.

To maintain line of sight with the ground radar, the drop planes were required to fly at least 4,000 feet above the ground. Yet, while radar could provide release accuracy, no reliable delayed-action parachute release mechanisms existed within South Vietnam; the loads would be plagued by the same drift problems encountered by the VNAF C-123s.

The first GRADS drops were flown on the night of April 19. Guided by the Skyspot site at Bien Hoa, the crews released their loads at 8,000 feet above ground level. Unfortunately, the results were disappointing; reports from the ground revealed that only 2 of 26 tons dropped were recovered. Over the next four days, C-130 crews flew six more GRADS drops, but only a small percentage of the loads were recovered.

An observer who watched drops from another airplane discovered the problem–less than half of the HALO (high attitude, low opening) delayed-opening parachute release mechanisms were functioning properly. The system would have to be improved before the GRADS drops would be satisfactory. Since the defenders of An Loc still had to be supplied, the 374th Wing returned to low-level container drops, this time at night.

Although Air Force C-130 crews stateside were trained in night-drop techniques, such training was suspended during tours in Southeast Asia, and no night drops had been flown in years. Yet the cloak of darkness would make the approaching C-130s invisible to the Communist gunners on the ground, and hopefully ensure their success. Air support was provided by AC-130 gunship crews on station over the besieged city.

Achieving some degree of surprise on the first two nights of drops, the American C-130 crews managed to put 120 out of 170 tons of supplies on or near the drop zone. Drop crews approached An Loc at 1,000 feet, then descended to their 600-foot drop altitudes for their release. Some crews opted for low-altitude approaches, followed by a pop-up to the drop altitude.

To counter the now successful airlift effort, the Communists gunners turned to barrage tactics, throwing up a curtain of fire in the path of the approaching C-130s and saturating the air over the drop zone with exploding shells. Evidently the enemy gunners were receiving sample warning of the approaching transports. On the third night of drops, the fourth C-130 over An Loc was shot out of the sky after entering the wall of fire; it crashed a mile from the drop zone.

An Loc was beginning to look more and more like Dien Bien Phu as the NVA gunners managed to thwart the airlifters’ efforts at supplying the besieged base. Further drops on the night of April 25 were canceled after the loss of the airplane and crew, and poor weather the next evening prevented the 10 missions scheduled for April 26. Meanwhile, plans were made for a 10-plane daylight drop mission at 600 feet, a plan Colonel Iosue termed ‘plain suicide.’ FAC pilots operating over An Loc agreed, and the planned drop was canceled.

On April 27, two airplanes made successful daytime drops, but both were shot up. Colonel Iosue was reluctant to expose his crews to the deadly daylight missions, in part because in 1972 only a few Pacific Air Force crews were qualified for drop missions. The same crew members were being used repeatedly for the most dangerous airdrop missions of the war. To counteract the danger, the C-130 crews wore flak vests and helmets while the loadmasters in the rear of the airplane developed their own protection–they filled a garbage can with tie-down chains and stood in it during the drops!

Over a seven-day period, the C-130 crews flew 37 drop missions, all at night. U.S. advisers on the ground reported that 35 tons of supplies were recovered, 96 tons ‘possibly recovered,’ and another 350 tons were termed ‘probably lost.’ Even worse, the intensity of the enemy barrages over the drop zone continued to increase. More than half of all missions took hits. On the night of May 3 a third C-130 was shot down, and all six crewmen aboard were lost.

After the loss of the third C-130 and the second crew over An Loc, the U.S. Air Force reluctantly discontinued further night drops and turned once again to the high-altitude, low-opening method. As before, there were problems. Some chutes opened high, allowing the loads to drift into Communist hands; others failed to open at all and sent the bundles crashing to the ground. Then another problem arose to face the airlifters: On April 29, the Communists fired an SA-7 Strella missile in Quang Tri province, near the DMZ. The possibility of SA-7s in the vicinity of An Loc ruled out a return to low-level drop techniques. Another method had to be developed.

On May 8, a C-130 crew made the first high-velocity drop at An Loc. Instead of using a standard parachute to allow a load to descend slowly to earth, the high-velocity method used a slotted drag chute that was designed to stabilize but not retard the speed of the load during descent. Though the cargo would hit the ground at about four times the speed of a normal drop, special packing allowed safe delivery of most commodities needed by the defenders at An Loc.

The advantage of the high-velocity method was the heretofore unprecedented accuracy. Of 140 bundles dropped on 11 missions May 8-10, 139 landed within the drop zone. Fortunately, there were no chute malfunctions. The higher altitudes allowable with the high-velocity method permitted the C-130 crews to operate above 10,000 feet-out of range of the SA-7s that made their appearance around An Loc on May 11. Finally a method to keep An Loc supplied had been discovered. The high-velocity method was used to deliver supplies to the defenders of An Loc until the troops were finally relieved.

While the An Loc resupply effort was the most dramatic of the Easter Offensive for airlifters–and undoubtedly the most difficult of the war–the springtime invasion saw other major supply efforts as well. To combat the invading North Vietnamese Army (NVA) troops, U.S. Air Force C-130 and VNAF C-123 crews hauled troops into threatened regions throughout the country. Airdrops, seemingly a thing of the past in Vietnam, once again became routine.

A major NVA target in the Central Highlands was the city of Kontum. On April 24, the NVA closed the roadway from Pleiku, cutting off the city from all ground resupply. Airlift became the city’s sole source of ammunition, equipment and especially–fuel. A major American contribution was the C-130 ‘bladderbird,’ a transport containing a giant rubber bladder in the back. The C-130 bladderbirds brought in badly needed fuel for the defenders’ helicopters and rolling stock.

One C-130 bladderbird, crewed by Lt. Col. Reed C. Mulkey’s 50th Tactical Air Squadron crew, was stranded on the ground at Kontum when a rocket knocked out the landing-gear tires and caused other major damage. Despite incessant shelling and sniper fire, a three-man repair party flew in to make the damaged airplane airworthy again. The repair project was severely hampered when NVA shelling destroyed a VNAF C-130 parked nearby, creating an explosion hazard. More maintenance personnel were brought in on April 30 to complete the repair job, and after working through the night with flashlights, the ground crewmen had the airplane airworthy again the next day. Colonel Mulkey’s crew returned from Tan Son Nhut to fly the airplane to safety. Further shelling caused additional damage to the C-130, but Mulkey and his crew were able to fly the airplane to Pleiku.

Enemy shelling increased constantly at Kontum until, by early May, daytime landings were extremely hazardous. To thwart the Communist gunners, the Air Force switched to night operations, with the four-engine C-130s flying supplies in and hauling out refugees on the return flights to Pleiku and Tan Son Nhut. Transport operations were coordinated with support from the AC-130 gunships circling overhead, just as they were at An Loc. VNAF C-123s operating to and from the mountain base suffered many losses. By May 16, three of the damaged Providers were stranded at Kontum after being hit by shelling. To make room for arriving transports, all three were bulldozed off the ramp.

The Communists launched a major effort to overrun Kontum, and by May 25 they had penetrated the airfield. When a C-130 took small-arms fire from three directions on landing, the decision was made to switch to airdrops for resupply. In the interim, supplies continued to arrive aboard U.S. Air Force and VNAF Chinook helicopters. By this time, the American C-130 crews and VNAF C-123 and C-119 crews had gained significant experience in airdrop techniques–not only at An Loc but also in support of garrisons at Ben Het, Dak Pek and Mang Buk, all of which had come under attack in preceding weeks and had to be kept supplied from the air. The HALO techniques developed at An Loc had come into wide usage. Further enhancement of airdrop technology came about with the arrival in late May of Tactical Air Command C-130 crews from the base at Little Rock, Ark., and Pope Air Force Base, N.C., in airplanes equipped with the new all-weather aerial delivery system, known as AWADS.

Airdrops commenced at Kontum on the afternoon of May 27. Over the next week and a half more than 75 missions were flown, all by U.S. Air Force C-130s, with great success. Nearly all the bundles were reported to have landed within the designated drop zone. By June 8, the Communist forces had begun to fall back, and night landings resumed. To complement the air-landed deliveries, 374th Wing C-130s continued daytime airdrops, using the high-altitude techniques that had proved to be the salvation of An Loc.

By midsummer the Communist offensive had been defeated, thanks in large measure to the efforts of the American and Vietnamese airlifters. Yet this effort had not been without cost. The U.S. Air Force C-130 force sustained the loss of four airplanes between April 18 and May 17, the first C-130s to be lost in combat since 1969. The VNAF transports were also hard-hit, with two C-123s lost at An Loc in late April, another at Quang Tri on May 1, and three others destroyed on the ground at Kontum.

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This article was written by Sam McGowan and originally published in the December 2000 issue of Vietnam Magazine.

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