On Nov. 27, 1969, a unique AC-130A gunship arrived at Ubon Air Base in Thailand for a secret mission called Operation Coronet Surprise. The aircraft—itself codenamed “Surprise Package”—helped solidify the role of the gunship in the Air Force’s arsenal.
By the late 1960s, the flying branch was concerned gunships were too vulnerable to be widely useful. Converting transports to attack aircraft was definitely a revolutionary idea.
The Air Force also had few points of reference for designing and using the new planes. Pilots and aircrews were learning gunship tactics on the job … and the results were mixed.
While troops loved the original AC-47 gunships, the planes were also relatively primitive. Modified World War II-era transports, the AC-47s needed flares to see in the dark and were vulnerable to enemy fire.
The AC-47s had no problem defending friendly fire bases in South Vietnam, but they were deathtraps over the Ho Chi Minh Trail. The Air Force halted missions over Laos after losing four of the slow, twin-engine aircraft in early 1966.
The four-engine AC-130 was a dramatic improvement over the AC-47, but was still vulnerable to the extensive enemy air defenses along the Trail. In May 1969, one of the new gunships took two hits from a 37-millimeter anti-aircraft gun and crashed during an emergency landing attempt.
The flying branch hoped that Surprise Package would settle the argument. The evaluation over Laos would help decide whether gunships could operate effectively in the face of stiff enemy resistance.
In August 1969, the Air Force turned the eighth AC-130A into a flying laboratory full of cutting-edge electronics and new weapons. The crew named the unique gunship Thor, after the Norse god of thunder and lightning.
The most visible changes were the new Bofors guns and a large antenna on the nose called Black Crow.
The 40-millimeter Bofors—old Navy anti-aircraft guns—were welcome additions. Thor used the added shooting range to fly higher and farther away from anti-aircraft fire.
The Black Crow was supposed to track the electromagnetic waves emitted by truck engines. The system could also detect enemy radar signals.
Inside, Thor also had additional night-vision equipment and advanced radars. Most importantly, a digital computer took all the information and told the crew where to shoot.
The new systems produced impressive results. During the 38-day Coronet Surprise evaluation, Thor flew 33 missions and blew up almost 200 enemy trucks.
The secretive nature of the program caused a number of problems. Ground crews often had no idea how to fix the experimental equipment when it broke—and there were no spares.
Thor remained in Thailand after the evaluation ended and continued to hunt alone along the Ho Chi Minh Trail. The Surprise Package aircraft would also alert nearby fighter-bombers to possible targets.
Between November 1969 and April 1970, Thor destroyed or damaged over 800 trucks. The other seven AC-130s each destroyed or damaged just 357 trucks on average in the same period.
Thor was shot down on Dec. 21, 1972 over Laos. Two members of the crew parachute to safety, but the other 14 died in the crash.
The program ended, but the aircraft had made its mark. The Air Force installed many of the Surprise Package upgrades on other AC-130s, old and new.
To this day, AC-130s use advanced radars and infrared video cameras to find their targets. Of course the technology has improved since 1969.
Thor’s successors have become a distinctive hallmark of American air power.