120-mm Tank Gun System Safety

In the January-February 1990 issue of ARMOR, two articles addressed the safety of 120-mm ammunition for the MlAl tank.' Both articles brought out important points and demonstated genuine concern about ammunition safety, but in the context of the entire 120-mm gun system, ammunition is not the only fire safety issue. The gun itself is an important concern. As is true of ammunition, if soldiers do not check and maintain the various components of the 120-mm gun, it can also become a potential fire hazard. Good maintenance and proper training are the keys to maintain confidence in the 120-mm gun as a safe system. Since 1985, when the frrst MlAl entered the inventory, there have been three ammunition fves or premature ignition of the round before, during, and after chamber-ing. In two of these fires, three crewmen were killed. In addition, there have been 18 flarebacks (a ball of flaming gases that escape from the breech as a case base is -ejected). Flarebacks have not been fatal. The Armor Center is committed to develop well-trained soldiers, NCOs, and officers to man the MlA1. In light of recent safety concerns about the gun system, we have attacked the issue and incorporated our lessons learned into training and products exported to the field. What follows is a look at our maintenance and training concerns, and what we are doing to resolve them. Attention to the following components of the gun is essential if the system is to remain safe:. The breech of the gun must be properly assembled and cleaned. Dirty or broken firing pins, operating cams improperly adjusted (the operating cam must set as slow as is practical and still allow proper functioning), stub base deflector assembly not aligned, and carbon build-up in the chamber have all been cited in accident investigations. 0The bore evacuator on the 120- mm gun must be properly maintained. Missing, pinched, or unserviceable bore evacuator seals have been linked to system fires, including the most recent fatal ammunition fire? There is still some confusion about the seals. The blue seal (5330-12-178-0030) is good but must be replaced when servicing the bore evacuator. Replace it with anew blue seal or anew black seal (5330- 01-280-6787). The black seal is reusable if it is still serviceable, in accordance with TM 9-2350-264-10 (Change 10). The -20 states that all bore evacuator seal: will be replaced every six months during semiannual services. Crews must take care to avoid pinching the seal during installation.. The stub base catcher assembly is also a key safety item associated with the gun. Soldiers say it gets in the way and is too flimsy, but its absence was the key factor in an ammunition fire that killed two crewmen! A superheated (700°F) stub base richocheting around the fighting compartment is an accident waiting to happen. As mentioned in the ammunition articles, the combustible canister of the 120-mm round is susceptible to damage from moisture and rough handling. 0 The combustible cartridge cases will absorb moisture if stacked unprotected in inclement weather or in wet interior ammo storage bustle racks (current environmental seals are not adequate; new seam welds are already being incorporated in newer tanks and tanks undergoing rebuild).. The cartridges will swell (making loading difficult), the propellant combustion may degrade (possibly leaving burning residue in the chamber), and the structural integrity of the round may be compromised (separation of the stub base from the cartridge, for example). Even when not wet, the cartridges can be damaged during uploading and downloading at the unit level Dr at the ASPS. 0 Commanders must stress inspection and turn-in policies at all levels. Perceptions that soldiers have to shoot damaged ammunition or buy it are misperceptions and must be addressed. As one report explains, "...soldiers are being told that they will be held pecuniarily liable for damaged rounds. There are indications that crew concern over liability for damaged ammunition may have led to damaged rounds being fired."' e h a d e r scan damage rounds if the stub base deflector assembly is not properly aligned. This causes scratches on the casing, which can have a cumulative effect on rounds that are repeatedly chambered but not fired. 0The loader must also check the serviceability of the ammo racks. ARMOR - 41

Burrs on the tubes may scratch the casings. We must train soldiers to properly operate and maintain the system. Crews must be aware of the safety concerns, which are unique to the 120-mm gun system. Crews must know how to properly upload and download 120-mm ammunition. They must know what to look for when inspecting ammunition. Crews must practice misfire procedures and crew evacuation drills. Crews must train in the proper uniform (NOMEX or BDUs with sleeves down, collars buttoned, black gloves on). The Armor School and major support commands are working to help you train properly.. At the Armor School, we have reviewed all 19IVSC12-related courses to ensure that MlAl safety-specific tasks are covered. This review included the Tank Commander Certification Course (TCCC) and the Pre-Command Course (PCC).

The Weapons Department, the Directorate of Combat Development (DCD), and TRADOC System Manager-Tank (TSM-T) are coordinating with Army Materiel Command (AMC) on ammunition testing and safety developments. A series of ammunition tests has so far attributed the most recent fatal ammunition fire to a damaged cartridge contacting burning residue? The last test in this series is scheduled for completion on 22 June. 0 The Weapons Department developed a film titled "Ammunition Fires and Crew Evacuation Procedures" (PIN# 708847/TVT 17- 141), and sent it to the field in early April. This 17-minute film details safety precautions specific to the 120-mm gun and ammunition, including ammunition inspection criteria. It also provides step-by-step crew evacuation procedures. 0 Tank Automotive Command has produced Change 10 to the MlAl - 10 TM. Advance copies of this document went to the field in May. Among other tasks, this change highlights misfire procedures, ammunition inspection criteria, and bore evacuator maintenance. PM Abrams is developing anew gunner's seat, and AMCCOM is developing a gunner's emergency air source. to be maintained and operated properly to be safe and effective. The MlAl 120-mm gun system is no different. Units in the field train hard. With this fast-paced operational tempo must come an increased diligence for the oversights and shortcuts that can compromise the gun system and lead to potential disaster. Do not take the gun system for granted. Take care of it, and it will take care of you! 0 Two important changes have resulted from this ongoing review. The tank commander hatch must be open for all MlAl gunnery (a short-term ftu until a TC hatch MWO goes into effect)? The waiting time for a misfire is now 15 minutes instead of 30 minutes (30 minutes was the initial change from the two-minute waiting period)? A third change, that a crew has to fire any round it chambers, is still in effect pending the results of the last ammunition test. 9 At the unit level, the chain of command must ensure that changes to TM 9-2350-264-10-11213 (changes 1 through 10) get to the crews. A first shipment of advance copies of Change 10 to the -10 did not make it to the crews, according to a telephonic survey of 27 units in the field conducted by the Directorate of Total Armor Force Readiness, 16-21 May 90. On a more positive note, the same survey revealed that safety messages are getting to the crews and that units are conducting crew evacuation drills on a regular basis. Finally, with regard to training, we must break the habit of loaders holding a second round while the first round is chambered. A loose stub base did strike a second round that a loader was holding and caused the previously mentioned fire that claimed the lives of the gunner and tank commander." The MlAl is a great tank. Like all pieces of equipment, however, it has 42 A Notes 'Koehler, Charles, CPT, "120-mm Tank Main Gun Ammunition: An Accident Waiting to Happen?," ARMOR, January-February 1990, pp. 7-9. And "mrectorate of Combat Developments Comments on 120-mm Tank Main Gun Ammunition: An Accident Waiting to Happen?," ARMOR, January-February 1990, pp. 10-12. *Directorate of Maintenance, Weapons System Matrix Management Division, AMCCOM, Safety Statistics Summary as of 2Q N 90, April 1990, (unpublished raw data). 3AMCCOM MSG, 1522302 Dec 89, subject: M1A1 Tank and 120-mm Ammunition Firing Inspection Precautions. 4Dowalgo, J., Root Cause Analvsis. Tank Rre Problem. M1A1 Main Battle Tank, (Special Publication ARASM-SP-88003), Picatinny Arsenal, N J US. Army Armament Research, Development and Engineering Center, February 1989, p. 1. 'ibid., p. 7. 'AMCCOM MSG, 1522302 D c 89. 'lbid. 'TM 9-2350-264-10-1/2/3, Ch. 10, Tracked: 120-mm Gun. MlA1, Washington, DC: 30 December 1985, p. 2- 268. 'AMCCOM MSG, 16 Mar 90, subject: Tank Ammunition Fire. 'ODowalgo, p. 7. 1 The Directorate of Total Armor Force Readiness (DTAFR) is the proponent for TAF safety. We will include safety articles in ARMOR on a regular basis. We can be reached at AV 464-TANK (24 hr. recording) or at AV 464-

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SAFETY!

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