During the early days of Vietnam Conflict, the US developed a special kind of attack aircraft to stop the flow of enemy troops and supplies: the gunship.
The Gunship aircraft, born from the conversion of cargo aircraft into powerful aerial weapons armed with big guns, were based on the concept of the circling attack.
In other words, the guns were mounted on the left side of the gunship so that the plane could fly a bank circle, achieving a good accuracy in strafing the target by using high velocity guns with a caliber of at least .30.
The first two types of gunships developed by the US were the twin-engine piston powered Douglas C-47 Skytrain and Fairchild C-119 Flying Boxcar, but the final leap was made relying on the size, speed and heft of the Lockheed C-130 Hercules which became known in the gunships world as the AC-130 Spectre.
The first AC-130As were deployed in Vietnam in 1968. They were armed with two 20 mm and two 40 mm cannons and they flew their first missions teamed with F-4s, which had the task to attack and destroy with cluster bombs the enemy AAA (Anti Aircraft Artillery) that opened fire against the gunship.
During the first missions the Spectre was also able to achieve an aerial victory when on May 8, 1969 an AC-130 shot down an enemy helicopter, as told by Wayne Mutza in his book Gunships The Story of Spooky, Shadow, Stinger and Spectre .
But the AC-130s were best and widely used from October 1969 to April 1970, the so called dry season, during which the NVA (North Vietnamese Army) trucks transported ammunition supplies by using the Ho Chi Minh Trail.
Spectres crews, that had the task to hunt trucks, were able to destroy and damage 25 of them in one mission: among these there were also AAA vehicles and, some times, the gunships came back to the base badly damaged. In the 1969-1970 dry season the NVA moved about 68,000 tons of provisions on the Trail, 47,000 tons of which were destroyed by the 12 deployed AC-130s with their 20 mm high density rounds and 40 mm Bofors cannons.
The 1970-1971 was even busier for the gunships since American and South Vietnamese soldiers began moving into Laos: in fact, while the numbers of AC-130s increased from 12 to 18, the western part of the Trail became filled with an always increasing number of vehicles coming from east, where interdiction sorties had concentrated. Therefore, during this period a gunship could destroy more than 25 trucks per night and the 1970-1971 dry season ended with 58,500 tons of material destroyed.
By the end of the 1971, after the NVA increased the number of the armored vehicles and the caliber of guns along the Trail, the U.S. deployed the first example of AC-130E.
As explained in detail by Wayne Mutza in his book, the new Spectre model was armed with a new more potent gun, the M102 105 mm Howitzer which replaced one of the Bofors cannons on the left side of the gunship.
The first Howitzer was installed in a gunship after it was repaired from some battle damages. Since it could fire from a distance of 12,000 meters, the Howitzer highly increased Spectre stand-off capabilities: the result was a higher kill ratio against trucks, since a vehicle hit by a 105 round had only a 10% chance to be still operable.
During its first Vietnam deployment this single howitzer-mounted AC-130E destroyed 75 trucks and damaged 92 ones with the 105, and destroyed 27 vehicles and damaged 24 ones with 40 mm fire in 32 missions.
Image credit: U.S. Air Force
The AC-130 illustrates the importance of being able to achieve air supremacy over a battlefield. Once you’ve done that, you can bring in speciality aircraft like this one. Can you imagine what a dozen or so AC-130s could have done when the U.S. Army was tied down in the hedgerows of Normandy?
A friend of mine was a Navy photographer during Vietnam and rode on one of these in combat. He was quite impressed.
The stats look impressive as always, just as the daily body count back then to the White House. Truth is, neither B52 nor Spookies could stop the flow of men, women and material traffic on the HCM trail. The technologies have improved by 1968, but the end results were basically the same as the French encountered during the spring of 1954 when they failed to stop similar traffic to a distant small place called Dien Bien Phu. A 500lb bomb did put a big hole on the trail, and a B52 will put in that many holes, but peasants below (through a lot of hardships) just built a trail around the holes over night, an unlimited de facto heart bypass. You really cannot bomb mud into mud.
Totally right – you can’t take anything away from those who have nothing to lose.
Before the AC-130, there was Black Spot:
https://medium.com/war-is-boring/the-u-s-air-forces-secret-cluster-bombing-cargo-plane-727b14269425
Left off in this is some remarkable technology, AN/ASD-5 ‘Black Crow’, which allowed the crews to identify the location of these vehicles not visually but by the radio frequency emissions of the truck’s engine.
A few minor corrections, the AC-130 was actually being developed before the AC-119 as Gunship II. The 105mm howitzers were installed along with upgraded -15 engines which changed the designation from AC-130E to AC-130H. Both of the photos are of AC-130U Spookys, a much newer airplane which went into service long after Vietnam.