The North Vietnamese used the trail, a huge complex of roads covering over 1,700 square miles, to move trucks at night, when they were safe from air attack, to resupply their forces in the south. The trucks were protected by a large number of anti-aircraft guns, 23-mm and 37-mm and a few 57-mm, manned by skilled crews. Interdicting the trail was a formidable task but a vital one.
In January 1967 Terry got the go-ahead for a six-month project to modify a C-130A to carry night observation equipment, forward-looking infrared (FLIR), and side-looking radar, as well as two 20-mm Vulcan cannon and two 7.62-mm mini-guns, all of which were connected to an analog firing computer that took in all the sensor inputs to correct the pilot’s side-looking sight for wind, airspeed, and attitude.
In September the prototype AC-130A arrived in Vietnam, with Terry as the lead pilot. On one of its first missions it knocked out eight trucks, and the aircraft—now named Spectre—quickly showed it was much more effective than any other night-attack aircraft. The Air Force ordered eight more C-130As modified into AC-130s, and at the same time modified cheaper, older, twin-engine C-119s into AC-119 gunships to supplement the AC-130s and AC-47s.
But while the AC-130s were decimating the North Vietnamese trucks, its new systems were proving unreliable. The Air Force sent the aircraft back to the States for some quick maintenance in February 1968, but rushed it back into service within weeks.
The North Vietnamese responded to the improved side-firing gunship by bringing more anti-aircraft guns into Laos. The gunships predictably attacked from a left banked turn, and under certain conditions they were visible from the ground—a quarter moon with high thin overcast made a gunship look “like a fly on a movie screen,” one crew member recalls.
To watch out for anti-aircraft fire, a crew member was assigned to look out the right side away from the attack, while another crew member, the illuminator operator, literally hung out over the lowered cargo ramp in the rear, secured by cables to look out the back. Often an evasive maneuver threw him out of the aircraft and he had to pull himself back in by the tethers.
Despite these precautions, in March 1969 the first AC-130 was hit and in May the first AC-130 was lost. By mid-1969 improved North Vietnamese defenses kept AC-130s out of some areas. Still, by April 1969 the Spectres had scored 42 percent of the truck kills in Laos while flying only 3.2 percent of the sorties.
In July 1969 and again in 1971, Ron Terry, now chief of the AC-130 program, made additional changes to the aircraft to counter the increasingly potent defenses. By March 1971 the Viet Cong had moved SA-2 radar-guided surface-to-air missiles into Laos. Dodging supersonic missiles at night over the high Laotian mountains in a four-engine aircraft was a daunting task. When a missile approached, the AC-130 had to dive down into the anti-aircraft environment, then struggle back up to altitude. That year, while no Spectres were hit by missiles, one AC-130 was downed by anti-aircraft fire and 33 were hit, some seriously.
In the never-ending quest for better armament, Terry replaced the 40-mm cannon he’d added to the 1969 model with a 105-mm howitzer. Approved under the name Pave Aegis, it arrived on February 17, 1972, and became an instant hit. The howitzer fired a 5.6-pound shell instead of the 40-mm’s 10-ounce shell, was extraordinarily accurate, and had a very long range. When it hit, the shell gave a bright flash that other aircraft could use as a marker.
On March 31, 1972, the North Vietnamese began a massive offensive. For the AC-130s, interdiction became secondary as the gunships flew night and day close air support missions. The Viet Cong brought a new weapon with them—the shoulder-fired SA-7, the Saturday Night Special of surface-to-air missiles—which forced the gunships to a higher altitude, but the Spectres could still operate. On May 5, the day an SA-7 scored its first hit on an AC-130, another Spectre got credit for killing 350 enemy troops and saving 1,000 friendly forces.