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Engineers redesign Howitzer recoil system to make gun safer, simpler, more reliable

Soldiers of the 3rd Battalion, 319th Airborne Field Artillery Regiment, perform a function test on a M119A3 Howitzer during a readiness training exercise on June 15 at the Hohenfels Training Area in Germany.

 

 

 

 

By Cassandra Mainiero, Picatinny Arsenal

After a year of redesigning the recoil system on the M119A3 Howitzer, engineers at Picatinny Arsenal in New Jersey have made the weapon safer, simpler, and more reliable while also reducing the cost of the recoil system.

The M119A3 Howitzer is a lightweight, direct and indirect fire support asset used by the U.S. Army and National Guard's infantry brigade combat teams.

Since 1976, the howitzer has been used by the British Army, where it was designed and is currently known as the L118 105-mm howitzer. It has been part of the U.S. Army throughout the past three years, and its predecessors, the M119, M119A1, and M119A2, played significant roles in Operations Enduring Freedom and Iraqi Freedom.

However, issues with the howitzer's recoil system have resulted in reliability, maintainability, and manufacturing problems. Some issues include weapon stability, seal leakage, warfighter safety, and complexity of manufacturing weapon components.

The weapon system is managed by the Project Manager for Towed Artillery Systems, PM TAS, within the Program Executive Office Ammunition at Picatinny Arsenal. Engineering support for the modified recoil system was provided by the U.S. Army Armament Research, Development, and Engineering Center, or ARDEC, also at Picatinny.

The Tank-Automotive and Armaments Command, or TACOM, is located in Warren, MI, and provided logistics support for the recoil effort. The manufacturing support was provided by Rock Island Arsenal -- ?Joint Manufacturing and Technology Center, or JMTC-RIA, in Rock Island, IL.

ARDEC engineers have been reconstituting the legacy recoil system to make it more user friendly and cost efficient. The program is currently entering full-rate production of the modified recoil system on the M119A3 Howitzer.

The recoil system is the part of the weapon that controls the backward momentum of a gun after it fires and returns it back to its original firing position. It is a complex system, because it includes various moving parts and requires constant weapon maintenance and adjustment during normal and combat operations.

"Several reports from Afghanistan regarding high-maintenance burdens on the M119A2 recoil system drove PM TAS to initiate the redesign effort," said Keith Gooding, Program Manager from Picatinny's PM TAS. "Partnered with ARDEC, TACOM, and JMTC-RIA, PM TAS embarked on a mission to address the Afghanistan reports. The result is a safer, more reliable howitzer for our Soldiers."

Redesigning the recoil system
One of the main issues with the legacy recoil system is its linkage between the buffer and recuperator. The buffer (a damping system) absorbs the reaction force of the fired howitzer and brings it to a controlled resting position. The hydropneumatic recuperator (a nitrogen gas spring system) increases the gas pressure and returns the system back to its original firing position.

But in the legacy recoil system, the buffer and recuperator were hydraulically tied together (meaning they were jointly operated by a fluid), and hence there was frequent seal or oil leakage.

This caused additional maintenance and premature wear of the system's metal parts.

To resolve this issue, ARDEC engineers disconnected the two parts, so that they function as independent systems and reduced the gas pressure. They also replaced the working hydraulic fluid with a silicon brake fluid and added an external fluid replenisher onto the system.

Silicon brake fluid is used in the howitzer's brakes. The addition of the brake fluid in the recuperator and buffer means that there is now an established commonality throughout the weapon system.

Fixing maintenance problems
Meanwhile, the fluid replenisher helps to compensate for the system's fluid volume changes with temperature.

The M119A3 Howtizer at Picatinny Arsenal. It is a direct and indirect fire support asset used by the U.S. Army and National Guard's infantry brigade combat teams.

 

 

 

 

"Temperature causes fluid expansion," explained Pete Lionetti, an ARDEC mechanical engineer.

"In the past, when the recuperator heated up, it [the fluid] would expand. When it was done, the fluid would have to go somewhere, so it would go into the buffer, and this caused a lot of maintenance issues.

"If the gun got too hot, you would have to bleed off the fluid. If the gun cooled down, then you had to add fluid," Lionetti continued. "So we added the external replenisher, and all it does is pick up the extra fluid."

Additionally, the group reduced the complexity of both the buffer and recuperator. The buffer's front head? (originally a single piece?) ?was converted into a two-piece head, which allows for misalignment within the system.

To simplify the system, engineers re-used the original recuperator's body and cylinder, but removed some of the internal components (a stuffing box assembly, rod, piston, and nitrogen bottle).

The simplified recoil system allows the weapon to return to battery (its original position before firing) in a shorter amount of time: less than 2 seconds at maximum elevation, and less than 1 second at lower elevation. It also reduces the weapon's overall weight and cost.

"The legacy system consisted of approximately 124 parts and costs about $60,000 to manufacture," said Maj. Wade Perdue, the M119A3 product director.

Yet the modified recoil system consists of only 75 parts (47 from the legacy and 28 new components) and costs about $40,000 to manufacture.

Safer for soldiers, too

The ability to reduce the complexity of both components is possible because of two other system modifications: the SLOS and the length of the recoil stroke.

The Suspension Lockout System, or SLOS, is an easily installable, field-deployable mechanism used to stabilize the M119 during high-angle firing. High-angle firing is often used for firing into deep or high terrains, such as mountainous or urban areas.

The original length of the legacy recoil stroke varied depending on the elevation of the gun, ranging anywhere from 14.5 in. to 42 in.

Now, though, the recoil is fixed at 25 in. The combination of the SLOS and the fixed recoil system helps to reduce the stress on the carriage and lower buffer rod forces, resulting in responsive fires and making it safer for the Soldier.

"The system was designed to shoot only at a quadrant of 1244 [mils elevation], meaning it only pivots up and down to a certain height, in a combat emergency," said Perdue.

"So, our engineers at ARDEC took on the effort to allow that gun to shoot at that quadrant in any environment."

"In the legacy system, it [the system] would jump up off the ground and almost flip over," added Perdue. "But, with the fixed recoil and the SLOS, you get more stability out of the gun, and the displacement is greatly reduced. This means that the gun crew can have a quicker response to fire, unlike the old days, where the gun crew would have to move the gun back into position before firing again."

"Plus, when you shoot at a higher quadrant, the tube comes back out of battery a lot further, which is dangerous because the breech will slam the ground and, if Soldiers are inside the trail, they could get hurt," continued Perdue.

Other past upgrades on the M119A3 included digital fire control, increased low-temperature capability, and the M20 breech, which helps with system maintainability.

As a result, ARDEC engineers have been able to reconstitute a system that is simpler, safer, and more reliable.

They've also been able to establish partnerships with PM TAS and Rock Island. In doing so, the recoil redesign project on the M119A3 will be fielded to warfighters in the coming year.

The Fixed Recoil and SLOS are currently being fielded to Massachusetts-Vermont Army National Guard (1-101 FA) this month.

The U.S. Army Armament Research, Development and Engineering Center is part of the U.S. Army Research, Development and Engineering Command, which has the mission to ensure decisive overmatch for unified land operations to empower the Army, the joint warfighter, and our nation. RDECOM is a major subordinate command of the U.S. Army Materiel Command.

Published August 2016

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