In our latest installment of ‘TWZ TV,’ we take a look back at the A-10 Warthog’s defining weapon, the 30mm GAU-8A Avenger cannon. Early on it wasn’t all roses for the Warthog’s iconic big gun, far from it actually. The Avenger did its best to blind its pilot while suffocating and rattling apart the host platform it was bolted into. It took engineering trial and error to see the GAU-8 go from a major basket case to the iconic close air support daemon it is today.
Check out the full story in the video below:
TRANSCRIPT:
There are few airplanes as iconic as the U.S. Air Force’s A-10 Warthog, and one very big, both figurative and literal, reason for that lies in its massive armor- shredding 30mm gatling gun that sprouts from its chin — the GAU-8-A Avenger cannon.
But as legendary as that gun has become, much of the A-10’s early development was spent ensuring that its cannon killed the enemy, and not Warthog’s pilot.
In other words, the newborn A-10’s big tusks resulted in some serious teething problems.
This is the story of how the A-10 overcame the Avenger’s woes and in doing so, became the feared ‘flying gun’ it is today.
How The A-10’s Avenger Cannon Went From Terrible To Terrifying
In 1971, the United States Air Force hired General Electric and Philco-Ford to build competing prototype cannons for its A-X program that aimed to field the Close Air Support plane of the future. Not only were these companies developing the guns, but they were also developing the ammunition and link-less feed systems, as well as devising how to integrate them into the competing Northrop Y-A-9 and Fairchild Republic Y-A-10 prototype aircraft.
These weapons were an integral, and literally huge, part of the airplanes that would carry them. So much so that according to the official Air Force case study of the A-10’s development, it quickly became clear that the A-X airframe would need to be designed around the gun, rather than visa-versa.
The Avenger Takes Flight
During the A-X development, the guns weren’t ready for the fly-off between the two competing prototype aircraft. Instead, the Air Force provided the smaller 20mm M61 Vulcan cannon that was in widespread use for the head-to-head trials, which the Fairchild Republic design ultimately won. So, Northrop’s Y-A-9 never even had the chance to fly with the Avenger.
In 1973, General Electric won the separate gun competition with its seven hundred pound, seven-barrel rotary cannon… it dwarfed a Volkswagen Beetle once you added in the ammo drum and feed system. The Air Force did also briefly consider arming the A-10 with the Oerlikon 3-0-4-R-K 30mm revolver cannon, however it had a much lower rate of fire and was significantly less reliable than the GAU-8. The Oerlikon offering suffered a malfunction once every 900 rounds, while the Avenger suffered one every 9,000 rounds on average…a ten times increase in reliability.
Ground tests of the GAU-8 went pretty much according to plan, but once they installed it in the Y-A-10 and tried taking the gun aloft for air trials in March 1974, major problems quickly cropped up.
For context, it’s important to remember the immense power of the GAU-8/A Avenger. The gun unloads nearly 70 rounds every second and up to 3,900 rounds a minute, and each 30mm cartridge is the size of a beer bottle. The projectiles alone, whether depleted uranium, armor piercing incendiary or high explosive incendiary, weigh nearly a pound, and it takes two hydraulic motors to spin the barrels and cycle the system. And when it fires, the gun belches a thick plume of smoke and fire, violently rattling the airframe while making its signature guttural roar. (cut to “BRRRRT” in A10 b-roll)
Shake, Rattle and Choke
When the Avenger was first integrated into the A-10 airframe, the most immediate issue was that the muzzle flash from the cannon firing blinded the pilot — a particularly dangerous side effect in an aircraft designed to execute low strafing runs while pointed towards the ground. Firing the cannon also left a dark coating of soot on the forward fuselage, including the windscreen, further obstructing the pilot’s view. This alone later required the development of a window-washing function using a cleaning solution and cooled bleed air from the aircraft’s propulsion system.
The next problem was that repeated firing caused so much heat and friction that metal components in the gun mounts began to bond together. While this didn’t impact firing the gun or flying the aircraft, it made the GAU-8 difficult to remove for maintenance.
Maybe most concerning, when the gasses from firing the cannon were released, they had a tendency to flow up over the aircraft’s wings and into the A-10’s high-set T-F-34 turbofan engines, threatening to suffocate them — not a good thing to have happen at any time, but especially when flying low directly over the enemy. Also, the fumes could contain unburned gunpowder which could build-up on the engine’s fan blades.
To address these issues, engineers tried lengthening the barrels in an attempt to dissipate the blast, and they also switched from copper bonding in the ammo to plastic. Neither solution solved the problem, though the change in the ammunition did reduce wear to the gun and was ultimately adopted.
For more than a decade, work continued to develop potential solutions to the A-10’s Avenger woes. These included at least three gun gas deflector concepts.
The first simply added a shield to the end of the nose in an attempt to mitigate the blast and keep gasses away from critical components. Another design extended the overall shape of the nose itself, entirely encapsulating the cannon’s muzzle and leaving just a slit for it to shoot through. This gave the A-10 a bizarre, almost ant-eater-like appearance. The third design involved a muzzle brake that was officially known as the G-F-U-16-A Gun Gas Diverter…and unofficially as “the Tickler.” This sinister-look contraption was mounted to the end of the GAU-8’s barrels and used baffles to reduce the flash and disperse the gasses from the muzzle away from the cockpit and engines.
After testing proved the device prevented the muzzle flash from blinding the pilot and alleviated the fumes from being ingested into the engines, the device was sent out to A-10 units for installation on their aircraft.
However, solving those two issues ended up making another trademark of the GAU-8, its intense vibrations while firing, even worse due to turbulence around the muzzle of the gun. This increased stress caused cracks within the gun bay, and while those cracks were not found to be a flight safety issue, they were a maintenance nightmare.
In the end, the undeniably medieval looking Tickler was ordered removed, and it joined the other attempted remedies to fixing the A-10’s gun problems in the trash pile. While engineers were able to alleviate the flash and vibration issues to a degree, fumes getting into the engines remained an issue.
The ultimate solution came down to an idea that was both crude and ingenious.
Since the most significant issue was that gasses were getting into the engine and causing it to suffocate, engineers made it so that when the pilot pulls the trigger, it continually trips the engines’ ignition system. So even if it hiccups and stalls suddenly, it immediately restarts. Between that and the windshield washing system, the A-10 was in business of reliably ripping apart stuff on the ground with its prized cannon.
Of course, it isn’t anything new for a prototype plane and its weapons to go through some growing pains. But the tale of the initial issues with the A-10’s signature weapon, and the creative ways its designers tried to address those issues, is an amazing concession of aircraft design to a single component. It’s testament to the fact that the gun was just as important as the plane itself, if not more so, and has allowed the A-10 to earn its fearsome reputation as the last plane enemy troops want to see above them on the battlefield.
Now, after decades of service, multiple conflicts and many past reprieves from being sent to the boneyard, the end of the A-10 era is finally drawing near. The Air Force is already in the process of drawing down the type, with the intent that it will be out of service well before the end of the decade. And while employing precision guided munitions largely became the A-10’s central focus during the back half of its career, having the big 30mm cannon and a lot of ammunition at the ready proved highly valuable in many engagements during the Global War on Terror. But now you know that the Warthog’s Avenger cannon wasn’t always such a celebrated feature, and how it went from terrible to terrifying due to the hard work of those that stuck by it.
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Source Agencies
