The US Navy Designed a New 105mm Gun for AC-130 and delivered it to the US Air Force to replace the Gunship’s M102 Howitzer and M137A1 recoil mechanism

The US Navy Designed a New 105mm Gun for AC-130 and delivered it to the US Air Force to replace the Gunship’s M102 Howitzer and M137A1 recoil mechanism

By Dario Leone
Jan 19 2022
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Naval Surface Warfare Center Dahlgren Division engineers designed, developed and delivered an upgraded 105mm Gun Aircraft Unit specifically made with the AC-130 gunship in mind.

Naval Surface Warfare Center Dahlgren Division (NSWCDD) engineers at Dahlgren, Va., designed, developed and delivered an upgraded 105mm Gun Aircraft Unit (GAU) specifically made with the AC-130 gunship in mind.

The 105mm GAU allows warfighters on the ground to complete their missions more effectively and safely while the AC-130 provides close air support, air interdiction and force protection.

The new weapon replaces the former gun system and positively impacts the warfighters’ ability to operate and maintain the system in the field.

“This has become a much more reliable system with less maintenance,” said Matthew Buckler, NSWCDD Battle Management System (BMS) Gun Weapons System lead mechanical engineer, in a NAVSEA news release. “If we can get a system that’s more reliable, that’s more repeatable, that works and that allows the warfighter to complete their mission every time – that’s a huge benefit for the warfighter.”

From the start of the design effort, the Dahlgren engineers behind the 105 mm gun worked directly with the warfighter to get real-time feedback from experienced gunners and technicians.

Engineers on the GAU project traveled to Air Force bases Wright-Patterson, Robins, Eglin, Hurlburt Field and Cannon throughout development for testing and direct collaboration with the warfighter. Gunners and technicians also came to Dahlgren to provide insight on the hardware’s performance after testing.

The US Navy Designed a New 105mm Gun for AC-130 and delivered it to the US Air Force to replace the Gunship’s M102 Howitzer and M137A1 recoil mechanism
Naval Surface Warfare Center Dahlgren engineers (left to right) Thomas Houck, Matthew Buckler and Gregory Fish inspect the new 105mm Gun Aircraft Unit after testing. The weapon is specifically designed for the most lethal gunship, the AC-130J.

The previous iteration of the AC-130’s 105mm gun system comprised the M102 Howitzer and M137A1 recoil mechanism. Designed for easy transport by helicopters or light vehicles, the M102 105mm cannon first saw service in Southeast Asia with the US Army in 1966. The M102’s light weight made it well-suited for use on AC-130 gunships. Both the M102 Howitzer and M137A1 recoil mechanism are no longer supported by the Army, meaning that an upgrade was necessary due to obsolescence and advancements in technologies since the original recoil mechanism was designed.

The upgrades to the 105mm GAU are sweeping, however, the engineers at Dahlgren were careful to ensure that the functionality, accuracy and usability of the weapon remain largely the same.

Throughout the iterative design process, Buckler said the team encountered challenging yet navigable obstacles and tackled each issue as it came.

“We’ve described [the development process] as peeling back an onion,” said Buckler. “You get the most immediate issue and solve that one. Then when you solve that one, something else becomes more important and you kind of just keep peeling it back until you’ve essentially solved all of your major issues and you can live with whatever the maintenance interval may be.”

When a weapon fires thousands of rounds and its recoil accelerates to 350G’s, or 350 times the force of gravity, maintenance is a natural consequence of operation. The engineers that led the GAU development also oversee the maintenance training to the warfighters.

The AC-130 is a C-130 converted to a gunship, primarily for night attacks against ground targets. All gunships evolved from the first operational gunship, the AC-47, to the AC-119, and then the AC-130A which was the basis for the modern C-130 Hercules gunship.

The US Navy Designed a New 105mm Gun for AC-130 and delivered it to the US Air Force to replace the Gunship’s M102 Howitzer and M137A1 recoil mechanism
Naval Surface Warfare Center Dahlgren engineers (left to right) Matthew Buckler, Gregory Fish and Thomas Houck stand in front of the new 105mm Gun Aircraft Unit they helped develop for the AC-130 gunship.

The AC-130 gunship has a combat history dating to Vietnam. Gunships destroyed more than 10,000 trucks and were credited with many life-saving close air support missions. During Operation Urgent Fury in Grenada in 1983, AC-130s suppressed enemy air defense systems and attacked ground forces enabling the successful assault of the Point Salines Airfield via airdrop and air land of friendly forces.

AC-130s also had a primary role during Operation Just Cause in Panama in 1989 when they destroyed Panamanian Defense Force Headquarters and numerous command and control facilities.

During Operation Desert Storm, AC-130s provided close air support and force protection (air base defense) for ground forces. Gunships were also used during operations Continue Hope and United Shield in Somalia, providing close air support for United Nations ground forces. Gunships also played a pivotal role in supporting the NATO mission in Bosnia-Herzegovina. The AC-130 provided air interdiction against key targets in the Sarajevo area.

In 1997, gunships were diverted from Italy to provide combat air support for US and allied ground troops during the evacuation of American noncombatants in Albania and Liberia. AC-130s were also part of the buildup of U.S. forces in 1998 to convince Iraq to comply with UN weapons inspections.

In 1999, AC-130s were involved in combat operations in Kosovo, where the first ever employment of the radar system to identify and attack targets was used. More recently, AC-130 gunships have supported operations Iraqi Freedom and New Dawn and have been employed in support of operations Enduring Freedom and Resolute Support. Finally, AFSOC gunships have also played a pivotal role in the recent uprisings in the Middle East. Gunships provide armed reconnaissance, interdiction and direct support of ground troops engaged with enemy forces.

Photo credit: U.S. Air Force and U.S. Navy

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Dario Leone

Dario Leone

Dario Leone is an aviation, defense and military writer. He is the Founder and Editor of “The Aviation Geek Club” one of the world’s most read military aviation blogs. His writing has appeared in The National Interest and other news media. He has reported from Europe and flown Super Puma and Cougar helicopters with the Swiss Air Force.

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