Key point: These gunships provided vital support to troops on the ground. Here's how they evolved to carry heavy weapons too.
The night of October 17, 1969, was a harrowing one for the South Vietnamese soldiers at Phung Hiep Army outpost. Viet Cong and North Vietnamese Army troops had attacked, showering the small base with mortar and machine-gun fire. Quickly the base was in danger of being overrun. But before the communists could attain their victory, help arrived for the beleaguered defenders.
South Vietnamese Captain Huynh Van Tong appeared in the skies over the battle at the controls of an AC-47 gunship. Flares dropped from the circling aircraft, illuminating the torn ground below. His targets identified, Tong and his crew opened fire with their three 7.62mm miniguns. Tracers leapt from the six-barreled weapons so fast it seemed as if hoses were dispensing luminous water over the battlefield. Sometimes the rounds ricocheted, flying into the air like sparks from a giant welder.
Soon ground attack aircraft appeared. Each one was ready to drop a deadly payload. Tong acted as an air controller for the waves of arriving U.S. Air Force F-100s. He directed the aircraft on their bombing runs and coordinated their actions. Even as the pilot did so, he kept his own plane in the fight, paying out his ammunition load three times during the night for a total of 63,000 rounds expended. Twice after the ordnance load was expended he returned to base, rearmed, and went back into the air. The enemy attack was repelled, and Trong received an air medal for his skill and determination.
The AC-47, affectionately known by U.S. troops as “Spooky,” was the aircraft that proved the concept of the aerial fixed-wing gunship as a close air support weapon. Fixed wing refers to a standard airplane as opposed to a helicopter or rotary wing aircraft. The first gunships such as the AC-47 were converted cargo planes. These former transport planes were prized for their endurance, being designed to stay aloft for long periods. Their size allowed them to carry substantial weapon and ordnance loads. In this case, the aircraft’s slow speed was an advantage, lengthening loiter time over a target and increasing accuracy.
Before the U.S. Air Force began testing the gunship theory, these aircraft began their lives two decades earlier as simply Douglas C-47 Skytrain cargo planes, the ubiquitous Allied transport of World War II. They were produced in the thousands and used for everything from transporting cargo to ferrying paratroopers to their drop zones. The C-47 gave excellent service throughout the war, but rapidly advancing technology and design rendered the aircraft obsolete in the years afterward. Despite being eclipsed by newer planes, the C-47 soldiered on due to its ruggedness, simplicity, and ability to operate from even the most rudimentary of airstrips.
By the early 1960s, the U.S. Air Force began experimenting with side-firing gunships for potential use in the small conflicts that seemed to be brewing everywhere during that decade. The C-47D was chosen as an easy and inexpensive platform. Early prototypes were finished in 1964, designated the FC-47D for fighter cargo. The Air Force changed the designation to AC-47D for attack cargo, allegedly due to loud complaints being put forward by traditional fighter pilots who did not want competition from what they considered an ungainly aircraft.
1930s Avionics With Cutting-Edge Weapons
The AC-47D shared the same characteristics of a standard C-47. The plane had a wingspan of 95 feet, a length of just under 64.5 feet, and sat almost 17 feet high. It was propelled by a pair of Pratt and Whitney radial engines, which produced 1,200 horsepower each. AC-47Ds had a maximum speed of 229 miles per hour but cruised at 150 miles per hour with a normal range of 1,500 miles. The AC-47 had a loiter time of seven hours, allowing it to remain over a target area for extended periods. The ideal operating altitude for the aircraft during combat missions was 3,000 feet above ground level.
What set the AC-47 apart from its more mundane cousins was the armament it carried. The cargo version was unarmed. AC-47s sported a trio of M-134 7.62mm, multi-barreled miniguns. All three weapons were trained out the left side of the plane so that their firepower could be concentrated on a single target. The original design allowed a rate of fire of 6,000 rounds per minute, but in practice this was often set at 3,000 rounds per minute. The AC-47 carried a standard load of 21,000 rounds to feed these fast-firing arms. Early versions of the aircraft sported up to 10 .30-caliber machine guns as an interim measure until a proper armament could be installed. Flares were carried to illuminate targets at night, a vital necessity since many Viet Cong/North Vietnamese Army attacks usually occurred during darkness. Between 24 and 56 flares were carried depending on mission requirements. The MK-24 flare had two million candlepower and lasted three minutes.
Simplicity was the defining feature of the AC-47. It carried no complex electronics or sophisticated fire control systems. The aircraft’s avionics and systems were essentially 1930s technology, proven and reliable. Even the flares were deployed by a crewman simply dropping them out the door when the pilot signaled by flashing the cargo compartment’s light. The plane carried a crew of seven: pilot, co-pilot, navigator, flight engineer, loadmaster, and two gunners. It flew low enough that targets were acquired visually, and aiming the fixed machine guns was simply a function of properly maneuvering the plane, a procedure that came quickly with experience.
The Concept of the Side-Firing Weapons System
But getting to this point had actually taken decades. The concept of a plane carrying side-firing guns was not new, but it had never caught on with aviation leaders or designers. One of the first people to develop the idea was Lieutenant Gilmour McDonald, an Army officer in the Coast Artillery. He suggested an aircraft with side-firing guns for attacking German U-boats; rather than dive on the target, attack, and then circle for another pass, such a plane would simply fly around the target in a circle, a technique known as a pylon turn. The aircraft’s armament would then always be pointed at the target, allowing continuous engagement. The idea found no purchase and languished until 1963, when a friend of McDonald’s, an engineer at Bell, realized the concept had merit and took it to U.S. Air Force Captain John Simons, who touted it as a method for engaging guerrilla fighters. Another version of the story claims the concept was derived from missionaries in South America, who lowered supplies in baskets from tightly turning airplanes, which kept the baskets still relative to the ground.
“We Opened Fire and It Scared Me Half to Death”
Simons’ superiors were initially skeptical but eventually gave him a C-131 transport to test the theory, now named Project Tailchaser. Funding issues prevented the program from carrying out a significant amount of testing until the arrival of Captain Ron Terry, who had just completed a tour in Vietnam in which he studied in-country air operations. Terry knew the Viet Cong often attacked at night when fast-moving fighters had difficulty tracking the elusive enemy. At the time C-47s were used to drop flares during night battles with great success. Terry looked through the project reports and stumbled upon Project Tailchaser. He went on a test flight and was convinced the idea had merit. He soon convinced a number of high-ranking officers of the method’s utility, including General Curtis Lemay, who authorized Terry to take the nine minigun prototypes to Vietnam and test the concept.
Political opposition within the Air Force almost ended the experiment before it began. Some leaders feared arming cargo aircraft would encourage the Army to do the same with its cargo planes and helicopters, diminishing the U.S. Air Force’s utility and competitiveness for budget dollars. For this reason, Terry and his people were nearly sent back home after their arrival in Vietnam. But cooler heads prevailed, and Terry was soon at work.
A pair of C-47s from the First Air Commando Squadron were armed and tested. On its first night mission, the FC-47 (as it was still known then) was called upon to defend a Special Forces base at Tranh Yend in the Mekong Delta on the night of December 23-24, 1964. After deploying several parachute flares, the plane cut loose with a three-second burst. “We opened fire and it scared me half to death,” recalled one of the crew. “I thought the guns had blown up. Flames not only came out of the muzzles but also blew back inside where they licked around the cans where the spent cartridges were going. It was really noisy too, with the din from all three guns going [simultaneously].” The plane fired a total of 4,500 rounds, and the shocked Viet Cong quickly retreated. The aircraft repeated this success 20 minutes later at another camp at nearby Trung Hung, driving the enemy off.