United States General Accounting Office

GAO Report to the Chairman, Committee on

National Security, House of

Representatives

December 1995 ARMY AND MARINE

CORPS M198 HOWITZER

Maintenance Problems

Are Not Severe Enough to

Accelerate Replacement

System

GAO/NSIAD-96-59

GAO United States

General Accounting Office

Washington, D.C. 20548

National Security and

International Affairs Division

B-262208 

December 27, 1995

The Honorable Floyd Spence

Chairman, Committee on National Security

House of Representatives

Dear Mr. Chairman:

As you requested, we obtained information on the Marine Corps’ and

Army’s reported maintenance problems with the M198 155-millimeter

(mm) towed howitzer to determine whether these reported problems

justify accelerating the development of a replacement weapon. We also

obtained information regarding the Marine Corps’ and the Army’s planned

development of a new, light-weight 155-mm howitzer.

Background Active and reserve Marine Corps artillery units use the M198 howitzer for

all direct support, general support, and reinforcing artillery missions.

Army light cavalry units use the M198 for direct support, whereas airborne

and airmobile infantry units use the M198 only for general support and

reinforcing missions. The M198 howitzers, first delivered to the services in

1979, are approaching the end of their 20-year service life.

Marine Corps and Army users of the M198 want to replace the

15,600-pound howitzer with a lighter-weight weapon to ease the

operational burden on crews and to improve air and ground mobility. The

Marines have found it difficult to tow the M198 over soft terrain, and only

their heavy-lift helicopter can move the weapon by air. With the Marine

Corps leading the development of a new light-weight howitzer, in

September 1995, the two services signed a joint operational requirements

document calling for a 155-mm howitzer that (1) weighs 9,000 pounds or

less and (2) fires munitions at least 30, but preferably 40, kilometers.

Initially, the Marine Corps wanted to accelerate development of a

light-weight howitzer to enable fielding by 2001 or earlier but found that

acceleration would be too costly. The Marine Corps now plans to field the

first light-weight howitzers in fiscal year 2002, and the Army in fiscal year

2005. The Marine Corps wants to buy 598 of the light-weight howitzers and

the Army 347. Development and procurement of these weapons is

estimated to cost about $1.4 billion.

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B-262208 

Results in Brief By themselves, the maintenance problems with the M198 howitzer do not

justify accelerating the development of a replacement. Although Army and

Marine Corps users of the M198 have experienced recurring maintenance

problems with the howitzer, some of these problems have been resolved,

and solutions to most of the remaining problems have been identified but

not funded. Even with these problems, availability of the M198 reported by

Army and Marine Corps units over the last 6 years averaged about

93 percent and 89 percent respectively.

The Marine Corps believes that the poor mobility of the M198 is a more

important reason than maintenance for replacing it with a lighter-weight

weapon. However, the anticipated air mobility improvements are

dependent on the ability of the MV-22 medium-lift aircraft, now in

engineering and manufacturing development, to lift a 9,000-pound

howitzer. So far, the developmental aircraft has not shown that it can lift

that weight.

Current light-weight howitzer candidates will fire projectiles to 30

kilometers, the same range as the M198. To achieve the objective firing

range of 40 kilometers, the weight of the new howitzer would have to be

increased, but an increase in weight could negate mobility improvements.

A new munition, the XM982, currently being developed by the Army

independent of the light-weight howitzer development program and

scheduled to become available in fiscal year 1998, is expected to achieve

the desired 40-kilometer range. However, it has not yet been tested in the

competing light-weight howitzer prototypes.

Despite Reported

Maintenance

Problems, Availability

Rates Remain High

Marine Corps and Army users of the M198 howitzer have reported a

variety of recurring maintenance problems. Some of the more serious

problems have been resolved. According to the Marine Corps and Army

weapon system managers, solutions have been identified for most of the

other problems, but funds have not been provided to make the fixes. Data

compiled from Marine Corps and Army equipment readiness reports

indicate that despite these problems, the availability of the M198 has not

been substantially affected. Although some units reported availability

dropping below 70 percent in some instances, this condition was usually

corrected within a few months.

Users of the M198 Report

Recurring Maintenance

Problems

In 1994, a joint Marine Corps and Army team of experts visited five major

active duty Marine Corps and Army artillery units to identify and quantify

the problems with the M198 howitzer, as reported by using units. This

Page 2 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
B-262208 

team found 15 recurring problems. The most serious recurring problems

reported were the following:

• Trunnion bearings were worn or had disintegrated. Worn or disabled

bearings affect the alignment of the gun tube and the accuracy of

projectiles fired from the howitzer. Improper alignment could cause

projectiles to miss the target and could endanger friendly troops.

• When firing the howitzer with the maximum powder charge, cracks were

discovered in the towers of the upper carriage. These towers hold the gun

tube in place. If the cracks in the towers are too severe, the gun tube could

back up too far during recoil and injure the crew.

• Travel locks crack and sometimes break when the M198 is being towed. If

the locks were to break completely during movement of the M198, the gun

tube could fall to the ground. Broken travel locks may damage the M198’s

elevation mechanism and equilibrators and make the weapon inoperable.

• Leaks found in recoil mechanism seals could limit howitzer operations. A

properly operating recoil mechanism absorbs the shock of the weapon

when it is fired and returns the tube to the proper position. Severe leaks

might cause metal contact, which could result in seizure of parts and

general failure of the recoil mechanism.

• Tires are prone to blowouts because they were not rated to carry the

weight of the howitzer. According to the Army weapons manager, during

1994, users of the M198 reported about 25 to 30 blowouts a month. When a

blowout occurs, the howitzer cannot be fired, and crews must either wait

for a new tire to be mounted by direct support maintenance personnel or

use one of the prime mover’s tires.

In addition, delays in the delivery of certain parts have had an adverse

effect on the availability of the M198 fleet.

Some Reported Problems

Have Been Resolved, but

Others Have Not

According to the Army and Marine Corps weapons managers who are

responsible for maintaining the M198 howitzer, problems with the

trunnion bearings, upper carriage towers, and recoil mechanisms have

been or are being resolved. They also said that they have identified

potential fixes to the travel locks and the tires but have not been provided

the funds to implement them.

Problems Resolved or Being

Resolved

Trunnion bearings can now be replaced by maintenance units located near

the users. Until recently, only depot-level repair shops could replace these

bearings, but authority to replace the bearings was delegated to the Marine

Page 3 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
B-262208 

Corps’ fourth echelon maintenance units and the Army’s general support

units, which are generally collocated with users.

In January 1994, the Marine Corps and the Army completed a modification

intended to keep upper carriage towers from cracking. According to the

M198 weapons managers, users have not reported any cracks in the towers

since the repairs were completed.

Unresolved Problems According to the Department of Defense (DOD), the cause of recoil

mechanism leaks is not entirely understood. For howitzers in long-term

storage, leaks have been attributed primarily to seals that failed if the

mechanism was not exercised regularly. Exercisers for the recoil

mechanism are being developed and are expected to be fielded by

June 1996. However, the cause of leaks found in howitzers used on a daily

basis has not been determined.

According to the Army weapons manager, the Army’s Armament and

Chemical Acquisition and Logistics Activity (ACALA) has considered

installing a shock-absorbing system on the M198 to resolve the problem of

cracks in the travel lock area. However, ACALA has not been provided the

estimated $750,000 needed to fully study this potential solution. The

manager said that although the Army and Marine Corps could simply

strengthen the travel lock area, stress would be transferred to other points

of the howitzer that could be more difficult to identify and repair.

Users have asked for better tires for the M198. According to the Army

weapon system manager, several manufacturers have recently offered the

Army tires that may be capable of supporting the weight of the M-198. The

Army is testing these tires. However, the weapons manager has not been

provided funds to buy them.

Reported Availability of the

M198 Remains High

Although recurring maintenance problems are reported, availability data

reported by using units to Marine Corps and Army weapons system

managers indicate that the M198 fleet has a high availability rate. The

availability rate reported by Army users from January 1989 through

August 1995 averaged about 93 percent. During the same period the

availability rate reported by Marine Corps M198 units averaged 89 percent.

Army artillery unit officials said that the M198 could have relatively high

equipment availability rates and recurring maintenance problems at the

same time. If a problem can be repaired within 24 hours, it is not reflected

Page 4 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
B-262208 

in equipment readiness reports. Our examination of one active Army

battalion’s maintenance records (June 1993 to March 1995) showed that

seven of its 24 M198s had problems that rendered them inoperable for

more than 10 days. Of the seven, two were inoperable for 30 and 39 days,

respectively. However, according to the maintenance officer of this

battalion, a majority of the problems were fixed within 24 hours.

Users and Weapon

Managers Differ

About the Projected

Service Life of the

M198

There is no consistent view regarding the state of the M198. Some users of

the M198 believe that these weapons will not last until a new howitzer is

fielded in fiscal year 2002. Officials of the Army’s 18th Field Artillery

Brigade expressed concern that the howitzer may not last its expected

20-year service life without a significant life-extension or product

improvement program. They said that to reduce maintenance problems

and extend the service life of the M198, about half of their oldest weapons

are being sent to ACALA to be rebuilt and are being replaced with newer

M198s from lower priority Army Reserve and National Guard units.

Similarly, the Marine Corps has begun to rotate newer M198s from

maritime prepositioning stocks to active artillery units. According to the

1st Marine Division, the M198’s 20-year service life is overly optimistic

because maintenance problems already identified may be symptomatic of

other problems that have not yet been identified. In addition, a former

artillery battalion commander of the division noted that the division’s

M198s receive the greatest use because in addition to providing direct

support, general support, and reinforcing missions, they also lend their

M198s to other Marine artillery units for training in the rough terrain of 29

Palms, California.

Contrary to the views of Army and Marine Corps users, the Army’s M198

weapons manager told us that the M198 can be maintained in service

indefinitely, since direct or general support repair facilities can replace

almost all parts, and enough M198-unique parts are available to meet the

services’ peacetime needs for 2-1/2 years. However, according to DOD,

nonavailability of common user parts procured and distributed by the

Defense Logistics Agency has created some significant delays in the repair

of some M198s.

The Marine Corps’ weapons manager does not believe that the M198s can

be sustained indefinitely but said that recent initiatives to repair major

problems have improved the availability of the howitzer. Availability rates

Page 5 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
B-262208 

for the Marines’ M198s have remained above 91 percent from May through

August 1995.

The Army and Marine

Corps Are Developing

a Lighter-Weight

Howitzer

According to users, Marine Corps doctrine, and systems development

officials, poor mobility of the M198 is the main reason requiring its

replacement. A new, light-weight howitzer, currently in development, is

expected to be easier to operate and move on the ground and in the air.

However, a howitzer weighing 9,000 pounds may not be capable of firing

munitions any farther than the M198. To achieve ranges beyond those of

the M198, the new howitzer would have to be made heavier, or a new

family of extended-range munitions would need to be developed. The

XM982, an extended-range rocket-assisted projectile currently being

developed under a separate program and expected to be usable in the new

howitzer, may achieve the desired 40-kilometer range.

Moving the Heavy M198

Around the Battlefield Is

Difficult

The 5-ton truck assigned as the Marine Corps’ prime mover of the M198

has difficulty towing the 15,600-pound howitzer over soft terrain such as

sand. According to an artillery systems development official, although the

Gulf War was the perfect situation for artillery because there was no mud,

the Marine Corps found it difficult to move the M198 by land and air

during Operation Desert Storm. To resolve the problem, the Marine Corps

is remanufacturing its 5-ton truck fleet with a stonger power train and a

22,000-pound towing capacity, which will allow it to move the M198 over

most types of terrain. This program is funded, and the first

remanufactured vehicles are expected to be delivered in fiscal year 2001.

The Marines can now airlift the M198 only with its CH-53E heavy-lift

helicopter and only under optimal weather conditions. The Marine Corps

has assumed that its new medium-lift aircraft now in engineering and

manufacturing development, the MV-22 Osprey, will be able to lift the new

light-weight howitzer. However, Osprey prototypes have not demonstrated

that they can lift the required 8,300 pounds or demonstrated their ability to

lift actual cargo.1

 Program officials are optimistic that the Osprey will be

able to lift a 9,000-pound load safely but told us that they do not know

whether a howitzer can be made sufficiently aerodynamic and stable to

allow for its safe movement by the Osprey.

1

Navy Aviation: V-22 Development—Schedule Extended, Performance Reduced, and Costs Increased

(GAO/NSIAD-94-44, Jan. 13, 1994).

Page 6 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
B-262208 

Although it uses the same truck, the Army has had fewer problems towing

the M198 than the Marine Corps. The Army’s 18th Airborne Corps

successfully transported the M198 in the sand throughout Operation

Desert Storm. Army and Marine Corps officials told us that the reason for

the difference may lie in how the two services use the M198. The Marine

Corps uses the M198 for direct support and general support missions. The

direct support mission requires the M198 units to closely follow supported

units, often over difficult terrain. The Army uses the M198 only for general

support missions, which may allow firing units to avoid difficult terrain.

The Army has no problem lifting the M198 with its medium-lift CH-47D

helicopter, a system the Marine Corps does not own. The CH-47D can lift

up to 22,000 pounds of cargo and easily carries the M198, its crew, and a

limited load of ammunition, in all but the hottest weather.

Light-Weight Howitzer May

Not Fire Any Farther Than

the M198

The Army and Marine Corps have been testing two light-weight howitzer

prototypes, and a third is expected to be available for a shoot-off in fiscal

year 1996. While these prototypes are expected to meet the weight

requirement, they probably will not fire beyond 30 kilometers. DOD said

that targets beyond 30 kilometers can be attacked with the extended range

Multiple Launch Rocket System, by aircraft, or by a new rocket-assisted

projectile currently in development.

According to the Joint Operational Requirements Document (JORD) for a

new light-weight howitzer, it must be able to fire projectiles 30 kilometers,

which is the same range as the M198’s. The Army agreed to this range,

although it had initially desired a light-weight howitzer with a range of up

to 40 kilometers to enable counterfire against other countries’ artillery that

can currently fire to that distance. The JORD now states that 40 kilometers

is the desired range.

However, views within the Marine Corps artillery community have differed

on what the range should be. On one hand, several Marine Corps officials

told us that mobility is the primary reason for wanting a lighter-weight

howitzer. Those artillerymen with a direct support mission favored

mobility over range. On the other hand, artillerymen with general support

and reinforcing missions said they need additional range to accomplish

their counterfire mission. One artillery battalion commander told us that

the Marine Corps should not invest in a new howitzer that will not fire

projectiles to distances significantly greater than the M198.

Page 7 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
B-262208 

Not having the mobility problems of the Marine Corps, the Army had

wanted to take a more measured approach to the development of a

light-weight howitzer to gain additional range. However, according to an

official of the Program Executive Office for the light-weight howitzer

development program, the Army concluded that insistence on a

40-kilometer range could delay the howitzer’s development up to 3 years.

To avoid such a delay, the Army and Marine Corps agreed that the JORD

would specify a minimum range of 30 kilometers and a desired range of 40

kilometers.

According to DOD, technical and simulation work led to the determination

that the optimal range for a towed weapons system is 30 kilometers. The

JORD working group, composed of user representatives and technical

experts, determined that a towed howitzer weighing 9,000 pounds and

firing 40 kilometers was not technically feasible. In addition to requiring a

longer development time, achieving a 40-kilometer range would require a

propellant development program, which would greatly increase the cost

and risk of the light-weight howitzer development program.

Under another program, the Army is developing the XM982, a 155-mm

rocket-assisted projectile that is expected to fire to a range of 40

kilometers. Since the XM982 is not be a precision-guided projectile, it will

not be used for close support missions. If it successfully reaches the

desired 40-kilometer range, the XM982 will primarily be used for

counterfire missions.

Agency Comments

and Our Evaluation

In written comments (see app.I) DOD agreed that maintenance problems of

the M198 alone do not warrant accelerating a replacement and stated that

accelerating the acquisition strategy would be cost prohibitive.

DOD disagreed on two counts with our conclusion that even with the

remaining problems the M198 availability rate remains high. First, DOD

stated that operational reliability of the M198 over the last 2 years provides

a much more realistic picture than the average availability we calculated

for a 6 year period. Army officials said that operational reliability refers to

the reliability of individual parts of the M198. However, according to the

Army weapons manager, operational availability data on the M198 fleet is

incomplete because it has not been systematically collected. He said that

the availability data reported in the Unit Readiness Reporting system

remains the most reliable indicator of the condition of the M198 fleet.

Page 8 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
B-262208 

Second, DOD said that the variability, rather than the average, of the

operational reliability and availability should be considered. DOD said that

between April 1991 and June 1994, the average availability rate for Army

units was 91 percent and for generally the same period the rate for the

Marine Corps was 88 percent. However, DOD said that during these

periods, the rate dropped to 72 percent in some Army and 69 percent in

some Marine Corps units. Our review of Army data indicates that the

lowest availability rate reported for the overall M198 fleet was 80.7 percent

in the fourth quarter of fiscal year 1991, but that the rate recovered to

91.7 percent the following month. Individual Army battalions and separate

batteries reported availability rates as low as 37 percent for any one

month, but in all cases, including for school support and reserve

component units, availability was restored to levels above 90 percent

within 3 months.

We did not review availability reports from individual Marine Corps

battalions and batteries but analyzed average monthly availability rates of

M198s reported to the weapons manager by each of the four Marine

Expeditionary Forces (MEF) from May 1993 through September 1995.

According to this data, the lowest availability rate was 68.1 percent, as

reported by the 2d MEF in June 1993. However, this unit reported a

90.3 percent availability 3 months later.

DOD stated that we appear to argue against the need for the light-weight

howitzer. We were not asked for and are not offering an opinion about

whether a lighter-weight howitzer is needed. Our objectives were to

determine whether maintenance problems with the M-198 justify

accelerating the development of a replacement and to describe the current

light-weight howitzer development program.

Technical comments provided by the DOD have been incorporated in this

report as appropriate.

Scope and

Methodology

To obtain information on the current status of the M198 howitzer, we

interviewed officials and reviewed documents from the Office of the

Assistant Deputy Chief of Staff of the Army for Operations and Plans in

Washington, D.C.; the Marine Corps Combat Development and Marine

Corps Systems Commands in Quantico, Virginia; the U.S. Army Armament

and Chemical Acquisition and Logistics Activity, Rock Island, Illinois; and

the Marine Corps Logistics Base, Albany, Georgia. We obtained an

operational perspective and discussed maintenance issues with officials

Page 9 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
B-262208 

from the Army’s 18th Airborne Corps and its subordinate units at Fort

Bragg, North Carolina, and Fort Campbell, Kentucky, and with officials

from artillery and support units of the 1st and 2nd Marine Divisions at 29

Palms, California, and Camp Lejeune, North Carolina. Finally, officials of

the Joint Program Management Office, at Picatinny Arsenal, New Jersey;

the Army staff; and the Army Field Artillery School, Fort Sill, Oklahoma,

provided us with information on the Lightweight 155-mm Howitzer and

XM982 development programs.

We conducted our review between May and October 1995 in accordance

with generally accepted government auditing standards.

We are sending copies of this report to the Secretary of Defense, the

Secretaries of the Army and the Navy, and the Commandant of the Marine

Corps.

Please contact me at (202) 512-3504 if you have questions about this

report. The major contributors to this report are listed in appendix II.

Sincerely yours,

Richard Davis

Director, National Security

 Analysis

Page 10 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
Page 11 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
Appendix I 

Comments From the Department of Defense

Page 12 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
Appendix I 

Comments From the Department of Defense

Page 13 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
Appendix II 

Major Contributors to This Report

National Security and

International Affairs

Division, Washington,

D.C.

Jess T. Ford, Associate Director

Richard J. Price, Assistant Director

Anton G. Blieberger, Evaluator-in-Charge

Robert H. Goldberg, Senior Evaluator

Karen S. Blum, Communications Analyst

Norfolk Field Office R. Gaines Hensley, Assignment Manager

Connie W. Sawyer, Jr., Senior Evaluator

(701070) Page 14 GAO/NSIAD-96-59 Army and Marine Corps M198 Howitzer
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