The M9 Armored Combat Earthmover (ACE) is a US Army engineering vehicle, intended for battlefield preparation. First operational vehicles were delivered in 1986. The US Army acquired a total of 448 of these engineering vehicles. It is also in service with US Marine Corps. The M9 ACE performed exceptionally well in Operation Desert Storm.
Tasks of this combat engineering vehicle include digging positions for armored vehicles and field artillery systems, to increase their survivability. It also breaches berms, prepares anti-tank trenches, barriers, repairs roads, clears obstacles, prepares riverbanks for vehicle crossing.
Front of the M9 ACE features a 6.7 m³ capacity bowl, apron and dozer blade. This engineering vehicle has a unique hydropneumatic suspension, which allows the front of the vehicle to be, lowered, raised, or tilted. It permits dozing, excavating, grading and ditching functions. In earthmoving operations the apron and blade are lowered for digging. Also by raising it's dozer blade and using it's scrapper blade, the M9 fills itself with ballast to improve earth working efficiency. It can also dump it out as a front-end loader.
This combat engineering vehicle has a welded and bolted aluminum hull structure with selected steel and aramid-laminated plates. Hull of the M9 ACE provides protection against small arms fire and artillery shell fragments. There is also an NBC protection system for the operator.
This armored earthmover carries no defensive armament. During combat operations the M9 ACE is usually protected by an M2 Bradley infantry fighting vehicle.
The M9 ACE is operated by a single engineer.
This armored earthmover is powered by a Cummins V903C turbocharged diesel engine, developing 295 hp. Engine and transmission are located in the rear of the hull. With short preparation this combat engineer vehicle is fully amphibious. On water it is propelled by it's tracks. However later amphibious mission of the ACE was deleted and the swim related components are no longer maintained. The M9 can be airlifted by the C-130 Hercules, or larger military cargo aircraft.
All operational M9 combat earthmovers were constantly upgraded to improve their performance, reliability, durability and readiness. Improved machines might look the same from the outside, however these are completely overhauled.
Armored Combat Earthmover M91-6
The US Army's search for an armored combat earthmover, or universal engineering tractor, spanned thirty years. The resulting M9 ACE features a front-mounted dozer blade behind which is an 8.7 cubic yard (6.7m3) scraper bowl. For jobs requiring a heavier machine, the blade could be raised and the bowl could be filled with dirt, bringing the vehicle's weight up to 57,000lbs (26,000kg). Originally, a 25,000lb (11,000kg) winch was mounted in the lower rear hull, beneath the engine and transmission. This was replaced by a 35,000lb (16,000kg) model with 165' +/- 2' (50.3m +/- .6m) of 3/4" (1.9cm) wire rope. The dozer blade was positioned by adjusting the hydropneumatic suspension. The operator is stationed at the rear of the vehicle and is provided with a cupola containing eight vision blocks. After the vehicle had entered service, modifications were performed that increased the vehicle's weight to the point that swimming was no longer feasible. The amphibious requirement was therefore dropped.
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- TM 5-2350-262-10 Operator's Manual Armored Combat Earthmover (ACE) M9 (NSN 2350-00-808-7100). Washington, DC: Dept. of the Army, Jun 2007.
- Hunnicutt, R.P. Sheridan: A History of American Light Tank, volume 2. Navato, CA: Presidio Press, 1995. Reprinted with permission from Sheridan, R.P. Hunnicutt ©1995, available from Presidio Press, 505B San Martin Drive, Suite 160, Navato, CA 94945.
- Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.
- Federation of American Scientists. "Armored Combat Earthmover - (M9 ACE)." DOD 101. 19 Feb 2000. 7 Nov 2001 <http://www.fas.org/man/dod-101/sys/land/m9-ace.htm>. DOD 101
- US Army TACOM. "M9 ACE - Description and Mission." 7 Nov 2001 <http://www.tacom.army.mil/dsa/pmtaws/cbt_spt/m9ace/descrip.htm>.
- Reyes, Larry. "ACE." Email to the author. 16 May 2006.
Last updated 11 Apr 2017.
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© Copyright 2001-17 Chris Conners
Combat Engineering Vehicle – 448 Built
To put it simply, the Armoured Combat Earthmover M9, often just known as ACE, is a battlefield bulldozer. The vehicle is intended as a highly mobile, protected earth moving vehicle for combat engineers. It is a valuable support vehicle to armored, mechanized and infantry units. In combat operations, the M9 ACE can perform a number of tasks in support of friendly units. These include mobility (clearing a safe passage of blockages), counter-mobility (route-denial, the reverse of mobility tasks), and survivability tasks (constructing defensive positions). The M9 features a number of innovative features, such as a hydropneumatic suspension, a ballastable front end, and the ability to be amphibious.
The first vehicles entered service 1986, with the vehicle serving in most major operations with the United States Military ever since, most notably in The Gulf War (1990-1991) and The War in Iraq (2003-2011).
Despite all of their uses and features, the M9s were highly unreliable and, as such, loathed by the troops it was there to support. Hydraulic and mechanical failures have plagued the ACE throughout its service life. To try and salvage the tattered reputation of the vehicle, an extensive upgrade program began in 2014, and, for now at least, these upgrades keep the M9 in service.
A search for a battlefield engineering vehicle that was capable of earthmoving tasks had been sought since the mid-1950s. Initially, this led to the development of a vehicle known as the All-Purpose Ballastable Crawler, or ‘ABC’, that was developed in 1958. This nomenclature was later changed to Universal Engineering Tractor, or ‘UET’. One of the features of the UET was that it could also carry troops in the empty ballast bowl via fold-out seats. This feature was later dropped, however.
What would go on to become the M9 appeared in 1977. The Engineer Laboratory at Fort Belvoir, Virginia, with added assistance from the International Harvester Co. and Caterpillar Inc., was responsible for the initial development of the vehicle. Pacific Car and Foundry were given a contract to build no less than 15 prototypes, based on the cumulative design of the three co-developers. These were completed by the early 1980s. After some additional improvements to the design, a contract for full production was signed with Bowen-McLaughlin York (BMY, now owned by BAE Systems). In total, 566 vehicles were ordered to be built. Due to budget cutbacks, however, only 448 of the vehicles were acquired. The first vehicles entered service in 1986, with production running into 1991.
General Specifications & Features
The M9 is not your every day 50 ton/tonne, earth-scraping, lumbering brute of a bulldozer. In fact, it is the exact opposite. The ACE is lightweight at around 16 tons (16.3 tonnes), allowing it to be highly mobile. This light weight is partly due to its welded and bolted steel and aluminum construction. The M9 is 20 feet 6 inches (6.25 m) long, 10 feet 5 inches (3.2 m) wide, and 9 feet 6 inches (2.9 m) high. The ACE’s lightness and compact size allow it to be air transportable by C-130 Hercules, C-141 Starlifter, C-5 Galaxy or C-17 Globemaster cargo aircraft. It also allows it to be amphibious. In ideal conditions, the vehicle can travel in water at 3 mph (5 km/h) using the rotation of the tracks to propel it. This was a feature that mostly went unused and consequently, most vehicles have had the amphibious equipment removed or it has simply gone unmaintained.
Only the rear-most portion of the vehicle is armored. This consists of welded aluminum with selected steel and aramid-laminated plates. This armor is in place to protect the single operator. It is intended to protect him against small arms fire, shell shrapnel, or a mine detonation. It is no match for a tank shell or missile though. The operator is located at the rear left of the M9 under an armored cupola with eight vision blocks. When operating head-out, a small windscreen with integrated wiper can be folded up to protect him from dust and debris. In combat conditions, however, the vehicle is operated with all hatches closed. Due to the location of the position, visibility was extremely poor, as the Operator could not see the ground directly in front of him. The M9 also has an optional NBC (Nuclear, Biological, Chemical) protection system. The Operator enters the vehicle through a cut out at the back of the M9 that doubles as a channel for the radiator to vent out through. Once he has climbed into this channel, the operator can turn left and climb in through the cupola’s hatch.
Quite clearly, the most important feature of the ACE is its ability to move earth. This is achieved with the use of an 8.7 cubic yard (6.7 m³) blade at the front of the vehicle. The lower half of this blade, which is also known as an ‘apron’, can fold upwards for road marches and travel and is held in place via sprung latches. The blade allows the M9 to carve out hull-down positions for gun tanks, dig gun emplacements, perform route denial (creating and filling anti-tank ditches), and improving bridge approaches. It could also be used aggressively to push barricades or debris from the path of attacking allies. If needed, ‘ripper’ teeth can be bolted into the lip of the blade.
Someone familiar with the operation of bulldozers may query how such a light vehicle can be an effective earthmoving vehicle. This is where the ballastable aspect of the M9s design comes into play. Behind the apron is a large ‘bowl’, an empty space designed to hold ballast to increase the vehicle’s weight. To fill this ‘bowl’, the dozer blade is lifted via hydraulic rams. The vehicle is then driven forward, gathering material in the void. At the front of the ‘bowl’, there is a small ‘scraper’ blade on the bottom lip, making shoveling easier. The vehicle will then back off and the dozer blade ‘apron’ lowered to cover the opening. With the added ballast, the M9s weight increases by up to 8 tons/tonnes, bringing it to 24.1 tons (24.4 tonnes). The added weight allows the ACE to shift larger and heavier amounts of material without much extra effort.
The added ballast also gives the ACE equal pushing/towing strength to the Caterpillar D7, a commercial bulldozer twice the weight of the M9 (that also served in the US Military), thanks to the increased tractive effort applied by the added weight. To discard the spoil, there is a hydraulic ram propelled blade that pushes the spoil out of the bowl. The blade is guided by two supports with casters attached, these casters run in a channel and keep the blade straight. When empty, the ballast bowl can also be used to carry small loads of cargo. The vehicles head lights are placed directly on top of the ‘apron’.
The M9’s power plant and transmission are located at the very back of the vehicle. The engine, an 8-cylinder Cummins V903C diesel, is rated at 295hp and can propel the vehicle to a top speed of 30mph (48 km/h). This top speed allows the vehicle to keep up with tanks and other armored vehicles in convoys, and allows for rapid deployment.
The M9 features a hydropneumatic suspension. There are four road wheels per side, each one connected to a high-pressure hydraulic rotary actuator. Instead of rubber, which can crack or shed chunks, the wheels are surrounded by a high-tensile polyurethane (plastic) tire. The drive sprocket is mounted at the rear, slightly higher than the road wheels. There are no idler wheels. The hydropneumatic suspension is a necessary feature as, because of the ballast bowl, the dozer blade could not be lowered to meet the ground. The suspension has two modes; Sprung and Unsprung. Sprung mode is engaged for travel and allows the vehicle to travel at top speed and traverse rough terrain and minor obstacles as the suspension arms can travel to their maximum degree. Unsprung mode almost flattens the suspension and limits the travel of the suspension arms, thus tipping the vehicle forwards so the blade or mouth of the ballast bowl can meet the ground.
The M9 is completely unarmed, aside from any personal weapons the operator might carry. For defensive purposes, the ACE is equipped with eight smoke grenade launchers. These are located in two four-tube banks at the center of the M9, just behind the ballast bowl. These can also be used to provide a smokescreen for allies.
At the rear of the M9 is a two-speed winch capable of a 25,000 pound (110 kN) line pull. This can be used to rescue allied vehicles or pull itself out of a ditch (even one of its own making) if necessary. The M9 is also equipped with a towing hitch at the rear, mounted just above the winch. This can be used to tow supply trailers and other equipment. Using the hitch, the M9 has a drawbar pull of 31,000 pounds (14,074 kg) at a speed of 1.5 mph (2.4 km/h).
Thanks to the hitch, the M9 is sometimes used to tow the M58 Mine Clearing Line Charge or ‘MICLIC’. These devices are used to clear large areas of explosive devices or blast a path through obstacles by use of a rocket that tows a line of explosives. The M58 is placed in a large armored crate located on a simple two-wheeled trailer. The line is 350 feet (107 meters) long and contains 5 pounds (2.2 kg) per foot (30 cm) of C-4 explosives. A total of 1,750 pounds (790 kg) per line. The MICLIC is fired forwards over the vehicle, and if it fails to detonate electrically, it can be manually triggered by time-delay fuses along the length of the line. The line is attached to the rocket via a nylon rope and can reach a distance of 100 – 150 yards (91 – 137 meters). To put this into perspective, an American Football pitch is 100 yards long. When detonated, the charge can clear a lane 110 yards (100 meters) long, and 9 yards (8 meters) wide. This device is often towed, but two of them can be mounted directly to the Assault Breacher Vehicle (ABV).
A later addition to the M9, made with its operation in hot countries such as Iraq, was a cooling system for the Operator. One of the problems with the ACE was that the operating cab was right next to the engine, meaning the compartment would often get unbearably hot. This is not ideal in a desert climate. The cooling system took the form of a vest known as the Microclimate Cooling System or ‘MCS’, designed by Cobham. The vest is filled with a water-glycol mix and is powered by a control unit. In the case of the M9, this was placed in the entry passageway.
This was a much-needed improvement to the comfort of the operator. However, it didn’t always go right, as this light-hearted account by Specialist Andrew Patton, 9th Engineer Battalion demonstrates:
“I remember watching a friend, a guy called Nate, use it for the first time. We went out on a mission to build up a berm around an Iraqi Police station. The ACE operator worked hard for a few hours and then when his part of the mission was done he parked his ACE, closed the hatch and took a nap with the vest on but the engine off. Half an hour later the dude threw open the hatch, jumped out, threw his body armor to the ground, shed the cooling vest and stood there shivering in the 110-degree heat…apparently without the engine to heat up the compartment he actually managed to get too cold wearing the thing…”
Typically, the ACE is distributed with 22 vehicles per Engineer Battalion, equating to seven per company including an ‘Operational Readiness Float’ (all necessary equipment). Almost all of the 448 production vehicles are in service with the US Army. The United States Marine Corps (USMC) has 100 M9s in their arsenal.
A number of faults have plagued the ACE throughout its service life. Multiple mechanical failures, mostly caused by the hydraulics, have given it a highly unreliable reputation. Even with its mobility and weight-gaining features, the M9 has become viewed as useless by many troops that served with them or has simply required the use of one. The general feeling of many was: “We’d rather have the CAT”, referring to the old reliable Caterpillar D7. Even the M728 Combat Engineering Vehicle (CEV) with its attached dozer blade was a preferred choice, at least up until its retirement in the mid-to-late 1990s. The quote below displays that feeling exactly:
“Hated when one showed up to dig my battle position, they were horrible and very unreliable. Hydraulic system always breaking. Loved me the D7 CAT our engineers used. They did use them [the M9] on occasion to transport EPW’s in ‘03, so I guess they did have some use.”
– Joe Daneri, US Army, retired.
The M9 is issued in the following order:
Engineer Companies in a Heavy Divisions: 7
Armored Cavalry Regiments: 6
Engineer Companies, Heavy Separate Brigades: 6
Engineer Combat Company (Mech) Corps: 6
Headquarters and Headquarters Company (HHC),
Engineer Battalions, Light Infantry Divisions: 6
Engineer Companies, Separate Infantry Brigades (Ribbon): 4
Engineer Companies (Assault Float Bridges)(Ribbon) at Corps: 2
Engineer Companies (Medium Girder Bridge): 1
Bridge Companies (Ribbon): 1
The M9 ACE has served in the Gulf War (1990-1991), the Bosnian War (1992-1995), the Kosovo War (1998-99), the War in Iraq (2003-2011) and the War in Afghanistan (ongoing). Unfortunately, the only real records of the M9s operation in a combat zone come from the Gulf War and the War in Iraq. Even then, they are sparse details at best. None the less, what is known is presented in the following sections.
Gulf War (1990-1991)
Operation Desert Storm, the combat phase of the Gulf War, is where the M9 ACE saw the most action, performing well in combat operations. It proved highly effective as Coalition forces assaulted Iraqi units in the besieged Kuwait City. They rolled through roadblocks and smashed through Iraqi fortifications in breaching operations. Despite having a similar pushing/towing strength as the D7 Caterpillar, it was soon found that the M9 was not quite as efficient when it came to earthmoving. However, its flexibility and maneuverability were appreciated by mobile armored units, especially when traversing vast swathes of desert. This somewhat made up for the slightly less effective digging ability. The armor on the M9, though thin, was still far better than the D7, a feature appreciated by the operators.
ACEs led the way when American Forces breached the border obstacles between Saudi Arabia and Iraq, demolishing trench lines along the way. However, the reliability issues of ACE and its general shortcomings did cause problems and a number of delays. When the M9 suffered a hydraulic fault, it could take many hours, or even days if more than one went down (not a rare occurrence) to repair.
The War in Iraq (2003 – 2011)
The poor reputation of the M9 was set in concrete by the start of the Iraq War in 2003. A number did serve in the 8-year conflict, much to the chagrin of many an American soldier. By the later stages of the war, its flaws were plainly clear. It became apparent that the ACE had trouble dismantling enemy anti-tank obstacles such as berms or ditches. Due to the location of the operator in relation to the blade, he cannot see the ground he is scraping resulting in the risk, when tackling a ditch, of toppling forwards into the void.
“When digging a battle position for a Tank, they were useless in my opinion. I always preferred the CAT dozers, especially when you hit rocky subsurface. Just hope they had their rippers installed. Even the M88 was more useful than an ACE when back blading the spoil. If our mechanics weren’t busy they’d help out in some units.”
– Joe Daneri, US Army, retired.
Second to this, the lack of armor in a War full of IEDs (Improvised Explosive Devices) and RPG (Rocket Propelled Grenades) wielding insurgents began to trouble many Operators. One officer described the M9 Operator as: “Alone, Unarmed, and Unafraid”. This flaw was amended somewhat, but in a manner that didn’t make many other units happy. It became standard operation for two M2 Bradley IFVs (Infantry Fighting Vehicles) to protect the M9 as it went about its business. That is two vehicles, intended to support infantry, occupied with the protection of one vehicle, leaving infantry units without armored support. It was deemed necessary for operation success, however, as the M9 could not defend itself as it was completely unarmed.
In early-2007, a couple of famous M9s took part in an operation in Ramadi, a city in central Iraq. The aim of the operation was to install an Observation Post (OP) between Camp Ramadi and a Combat Outpost called ‘Steel’. The M9s in question were ‘Dirt Diggler’ and ‘The Quicker Pickerupper’/’Bounty’, belonging to C. Company 9th Engineer Battalion, 1st Infantry Division.
Both of these M9s have quite a story regarding their names…
“After having waited quite some time for the order to move out a bored and rebellious M9 ACE operator named Nate* pulled out a can of spray paint and shocked everybody by graffitiing his vehicle with the now famous “Dirt Diggler” name. The second ACE operator followed suit and painted his vehicle to say “The Quicker Picker Upper, Bounty”. Upon seeing the graffiti, our chain of command nearly lost its collective minds, because spray painting a military vehicle isn’t received much better than graffitiing a building. I stood at a distance and watched as everybody in Nate’s chain of command took turns exploding at him with shocked rage at what he had done. He later told me that our First Sergeant had among other things, threatened that if the paint was still there after the mission, Nate would be removing it with a toothbrush. Naturally, as a lower enlisted man, I thought this was all very funny and made a point of taking several pictures to preserve the incident…luckily for the two M9 ACE operators the spray paint rubbed off almost the instant the dozer blade touched the dirt. No one was punished for the graffiti and the rest of the company’s ACE operators took notice of this and it became a bit of a tradition of ours to graffiti the dozer blade prior to each mission…”
– Sample of a written account by Specialist Andrew Patton, 9th Engineer Battalion. Used with permission.
*This is the same Nate involved in the MCS incident
A few M9s also took part in Operation Thunder Reaper, a route clearance operation which took part in December 2007 in Mosul. The objective was to clear the major highways so they once more became usable by civilians. This consisted of scraping the roads clear with the M9s followed combat engineers repaving them where necessary. The Operation resulted in the clearance of around 10 miles (15 kilometers) of highway.
In 2014, an upgrade program that had been running for almost eight years ended. It aimed at fixing the multiple problems that made the M9 such a hated vehicle. These feelings are echoed in the quote below from Joe Klocek, the product manager for Engineer Systems at U.S. Marine Corps Systems Command, Quantico.
“There were performance issues and reliability issues that were becoming a major problem, the initial system was fielded before Operation Desert Storm, so we were dealing with some ‘70s technology.”
The ‘1970s technology’ referred to was the intricate, hard-piped hydraulic lines which so often malfunctioned resulting in lengthy periods in repair shops inactive. It also included the lever-based control systems that made precise work difficult. Visibility was another major issue with the M9, as in combat conditions, the Operator had to control the vehicle ‘buttoned up’ (all hatches closed). To quote, Klocek: “Imagine trying to punch through an anti-tank ditch, 12 feet deep and eight feet wide, and not being able to see anything.”
The visibility problems were solved by the introduction of a 360-degree camera system (consisting of 10 separate cameras) by Leonardo DRS called the Vision Enhancement System (VES). No longer is the operator blind to what’s happening directly in front of the dozer blade. The system also provides night vision.
The hydraulic levers were replaced with joysticks, allowing for vastly improved and precise control. This was accompanied by a redesign of the highly problematic hydraulic subsystems. A new, more powerful engine was also added, but the specifics of this are currently unknown. This allows it to be more effective in its bulldozing role. Other improvements include an automated track-tensioning system, improved hull construction, automated fire extinguishers, and a redesign of the internal electronics.
It remains to be seen whether the new upgrades to the M9 ACE will repair its tattered reputation, and prove itself useful to the Modern US Military.
There were other upgrade options for the M9, such as a possible remote control version using a ‘Standard Robotic System’ (SRS) by Omnitech Robotics of Colorado (as used on the M1 Panther II) but, for unknown reasons, this was not accepted. New vehicles that fulfill similar roles as the M9, such as the M105 DEUCE (DEployable Universal Combat Earthmover), also started to appear in the early 2000s, putting pressure on the M9 ACE to perform.
For now at least, the upgrades the M9 has received keep in service with the US Military for the foreseeable future. The vehicle is also currently in service with the Taiwanese and South Korean Military.
In 2009, a deal was signed with the Turkish company FNSS Savunma Sistemleri A.Ş, (a company partly owned by BAE Systems, owners of the M9 ACE patent) for the production of a local variant of the M9 ACE. The vehicle’s official designation is ‘Amphibious Armored Combat Earthmover’ or ‘AACE’. Although, it is also known as the Kunduz, and as the ‘AZMİM’ or ‘Amfibik Zırhlı Muharebe İstihkam İş Makinesi’.
The AACE is far from a straight copy of the M9, and incorporates a couple of very different features. For one, the AACE retained and elaborated on the M9’s amphibious abilities, which largely went unused and was not maintained. To propel it through the water, the AACE features two water jets, placed over the drive wheels. These jets give the dozer a top water speed of 5.3 mph (8.6 km/h), and allow it to swim against currents of 4.9 feet/sec (1.5 m/sec) in rivers or streams. It is also extremely maneuverable in the water, and able to turn 360 Degrees on the spot. Secondly, whereas the M9 is a one-man vehicle, the AACE is operated by two crew. The operating position remains at the left rear of the vehicle, but there are now two seats, one in front of the other. To accommodate this, the cupola of the M9 was exchanged for a simple two-piece hatch.
The amphibious nature of the AACE is crucial to its main task of preparing river banks during river crossing missions. It is of course also used to perform standard bulldozing tasks and operates like one in the same manner as the M9.
After four years of development, the AACE entered service in 2013. The vehicle is currently in the arsenal of the Turkish Army and has become a very popular vehicle, unlike its M9 cousin.
The Armored Combat Earthmover M9 (ACE).
M9 ACE with suspension raised.
Both illustrations were produced by Ardhya Anargha, funded by our Patreon campaign.
|Dimensions (L-w-H)||20′ 6” (6.25 m) x 10′ 5” (3.2 m) x 9′ 6” (2.9 m)|
|Total weight, battle ready||16 tons (no ballast), 24 tons (full ballast)|
|Propulsion||Cummins V903C, 8-cylinder, diesel|
|Maximum speed||30 mph (48 km/h) on road|
Discussion with Andrew Patton, former Specialist, 9th Engineer Battalion, Iraq War veteran. A written account of some of his experiences with the M9 can be found HERE.
Presidio Press, Sheridan: A History of the American Light Tank, Volume 2, R.P. Hunnicutt
Sabot Publications, M9 ACE: Armored Combat Earthmover, Chris Mrosko & Brett Avants
Armoured Vehicle Database
Military Analysis Network (Future Upgrade details)
M9 ACE (Armored Combat Earthmover)
BMY Combat Systems / United Defense LP - USA
(View other Vehicle-Related Manufacturers)
(OPERATORS list includes past, present, and future operators when applicable)
Traverse bodies of open water under own power with / without preparation. ✓Engineering
Onboard systems provide solutions to accomplish a variety of battlefield engineering tasks. ✓Special Purpose
Special purpose design developed to accomplish an equally-special battlefield role or roles.
(Showcased structural values pertain to the base M9 ACE (Armored Combat Earthmover) production variant. Length typically includes main gun in forward position if applicable to the design)
Powerplant: 1 x Cummins V903C 8-cylinder diesel engine developing 295 horsepower.
(Showcased performance specifications pertain to the base M9 ACE (Armored Combat Earthmover) production variant. Compare this entry against any other in our database)
8 x Smoke Grenade Dischargers.
(Not all weapon types may be represented in the showcase above)
M9 ACE System Improvement Plan (SIP) - Multi-phased improvement program for upgraded existing M9 ACE fleet.
M9 ACE Standardized Robotic System (SRS) - Proposed unmanned remote-controlled variant.
KM9 - Korean Army designation
Vehicle ace army
DESCRIPTION: The M9 is a highly mobile, armored, amphibious combat earthmover capable of supporting forces in both offensive and defensive operations. It performs critical combat engineer tasks such as digging hull defilade fighting positions for guns, tanks and other battlefield systems to increase their survivability. The ACE breaches berms, prepares anti-tank ditches, prepares combat roads, removes roadblocks and prepares access routes at water obstacles.
The engine, drive train and driver's compartment are laid out in the rear of the vehicle, while the front features an 8.7 cubic yard bowl, apron and dozer blade. Armor consists of welded aluminum with selected steel and aramid-laminated plates. An armored cupola containing eight vision blocks covers the driver's compartment. The vehicle hull is a welded and bolted aluminum structure with a two speed winch capable of 25,000 pound line pull. Towing pintle and airbrake connections are provided. It is equipped with a unique suspension system which allows the front of the vehicle to be raised, lowered, or tilted to permit dozing, excavating, rough grading and ditching functions. In addition, the M9 has armor protection against small arms and artillery fragmentation, a smoke screening capability and chemical-biological protection for the operator. It is capable of 30 MPH road speed, is transportable in C-130, C-141, and C5A aircraft and can swim at 3 MPH under ideal conditions [though with the deletion of the swim mission, swim related components are no longer required to be maintained for the M9 ACE].
By raising the dozer blade and using its scraper blade, the ACE can fill itself with ballast to improve dozing efficiency. Another key feature of the M9 is its unique hydropneumatic suspension system. The principal components are eight high-pressure hydraulic rotary actuators (four on each side) which connect to the roadwheel stations. During high-speed travel, this system assures a smooth ride through the use of shock-absorbing accumulators. In earthmoving operations, the operator rotates the actuators, thus lowering the apron and blade for digging.
A typical combat engineer battalion will contain 22 ACES - seven per company plus an operational readiness float. The active Army has a total of 447 M9 ACEs.
STATUS: Insufficient funds were available to purchase all Armored Combat Earthmovers (ACE) required during initial and subsequent procurements. A total of 448 systems have been fielded with 57 additional ACEs needed to complete fielding to 87 percent of Force Package II and prepositioned stocks. In addition Phase III of the System Improvement Plan has yet to be started. This phase includes a variety of track, hull and blade enhancements. Microclimatic cooling system is planned to be fielded FY 96. System Improvement Plan Phase I & II is complete. Phase III & IV is under development.
The M9 ACE System Improvement Plan (SIP) is a multi-phased program designed to improve the performance, durability, readiness and MANPRINT characteristics of the vehicle. The multi-phased nature of the program is necessitated by the available funding stream. SIP Phase 1 consisted of: bolt-on front track retainers, steel skid plates, high pressure hydraulic filters, battery box deflector, scarifier blade uplocks, scarifier blade for half the fleet, inserts for improved winches, ejector debris shield, and modified rear bump stops. Kits were applied at units by depot and DOL teams during 1993 and early 1994. SIP Phase 2 consists of: thicker roadarm retainers, preformed radiator hoses, lengthened oil drain line, redesigned parking brake linkage and steering rod, vent fan filter, tachometer/ speedometer grease fittings, inclinometers, and steel CB/GS linkage. They are funded for and installed by units or through attrition.
SIP PHASE 3 - DETAILED DESCRIPTION OF PROJECTS
Hardened track pin with modified track shoe - Current track pins bend, causing NMCM time in two different ways. They deform the bushings, resulting in track maintenance, and they are difficult to remove when bent. Harder track pins will allow higher torque which will reduce bending moment. This will reduce frequency of track failures and make pin removal easier when track needs to be separated. In addition to the hardened pins, future buys of track will also have a larger pocket for the track pin nut. This will make it easier to get a socket on the nut even after the track edges get worn.
Hydraulic troubleshooting procedures - Reformat all hydraulic troubleshooting procedures to simplify fault isolation. The ACE has an extensive and complex hydraulic system. Insufficient hydraulic troubleshooting expertise is the single largest contributor to M9 NMCM downtime. It also contributes to NMCS time because good components are being removed and replacements ordered unnecessarily. Unit mechanics require detailed and complete troubleshooting procedures which are easy to use. Goal is to cut troubleshooting time and eliminate ambiguous or faulty troubleshooting paths. No hardware changes to the vehicles are included in this project.
Actuator mounting rings - Provide a stronger mounting system for the rotary actuators. Currently, actuator mounting bolts screw into steel inserts in the aluminum hull. The inserts pull out, resulting in loose actuators, hull damage, hydraulic line failures and damage to roadarms and actuators. Under this project, steel rings will be fastened inside the hull. The actuator bolts will pass through the existing mounting points and screw into the steel rings. The field modification installs rings at the front actuator station only; however, the rings can be installed at the three other stations as well if those hull inserts should come loose.
Bowl access plates - Provide easy access to the front actuators for troubleshooting and maintenance. Front actuators, accumulators and hydraulic lines require both scheduled and unscheduled maintenance. Currently, mechanics must perform troubleshooting and repairs from underneath the ACE, working in dark and cramped conditions. This increases maintenance time and leads to leaking hydraulic fittings. Access through the bowl floor will decrease maintenance time and eliminate most causes of actuator hydraulic leaks.
Hydraulic filtration improvements - Hydraulic cleanliness is critical on the ACE. To achieve the cleanest possible hydraulic system, a more efficient return line filter and a high pressure filter at the compensating pump output will be added. Three hydraulic tests points are being added at the high pressure filters. Also as part of this project, the two compensating pump suction hoses will be modified to prevent collapse and cavitation. Finally, the compensating pump adjustment will be improved by replacing the existing adjusting clamp with an adjusting screw and jam nut.
Hub and sprocket redesign - Current hub requires two unique sprockets. The outer one tends to bend and is difficult to fabricate, resulting in producibility delays and lengthy NMCS downtime. This project will eliminate the current outer sprocket and permit use of the inner sprocket in both positions. Goal is to eliminate shortages and higher cost of outer sprockets, and reduce maintenance burden. Also, the hub will be piloted onto the final drive output shaft, reducing the shear load and resultant failure of mounting bolts.
Semi-automatic track tensioner/adjuster - Currently, the operator checks and manually adjusts track tension using a grease gun before each mission. The new system will allow the operator to adjust track hydraulically from within the driver's compartment. With the manual system, the tension setting is a compromise, since the track needs sufficient slack to allow the suspension to go from sprung mode (travel) to unsprung mode (dozing). The semi-automatic track tensioner will relax the track to change between sprung and unsprung and then re-tension the track allowing a tighter envelope. This will reduce the number of track throws and associated damage and wear to suspension components and adjacent hull components.
Final drive improvements - Design an oil level indicator and modify the output shaft. Operators cannot assess the condition or lack of oil because there is no method to check oil level. This project will permit detection of water, contamination or loss of oil. Also, the output shaft will be modified to accommodate the redesigned sprocket hub.
Improved winch - With the current winch, the ACE has a limited ability to self-recover. This project will increase winch rating from 25,000 lbs to 35,000 lbs, double cable length from 100 feet to 200 feet, and add a friction brake to enable the M9 to hold a load on a slope.
Steel dozer blade - Develop a steel replacement for the existing aluminum dozer blade. The current aluminum blade suffers damage when used in rocky terrain, is marginally suited for use with scarifier teeth, and generally wears down. Repair is difficult and involves time-consuming aluminum welding, resulting in extensive mission downtime. The complex hollow-box design also means that replacement blades are very expensive and have long leadtimes. A steel dozer blade will be less expensive, more resistant to wear and easier to repair if damaged.
Automatic blade folder - - Let the operator remotely fold or unfold dozer blade from the crew compartment. This procedure now takes up to 1/2 hour to perform, requires crew to be exposed and stops the ongoing mission. Failure to fold the blade during cross-country travel could result in vehicle damage or operator injury. This project is not a readiness enhancement, rather it offers a major performance improvement to the mission.
EMPLOYMENT CONCEPT: The M9 is capable of performing mobility, countermobility and survivability tasks in support of light or heavy forces. Tasks to be performed are the excavation and preparation/reduction of obstacles, bridging operations, battle positions, strong points, and protective emplacements for command posts, air defense, communications equipment and critical supply/logistical bunkers. Other major tasks will be route clearing and maintenance in conjunction with both defensive and offensive operations.
In Operation Desert Storm the M9 Armoured Combat Earthmover (ACE) performed exceptionally well in support of combat operations. The ACE proved to be a successful combination of armoured vehicle and combat earthmover that was capable of keeping pace with the manoeuvre units, while providing crew survivability. While not as efficient as the D7 Dozer in earth moving, its ability to move with manoeuvre forces over several hundred kilometres of desert allowed it to successfully perform a wide variety of missions such as construction of combat roads and trails, survivability positions and berms. It is however, a fallacy that the ACE can move as fast as an M1 or M2. The vehicle is governed to prevent this.
But the training of ACE operators appeared to he inadequate. Operators were unfamiliar with the techniques associated with dozing, scraping, cut and fill ops, and grading. The ACE experienced trouble in reducing the berms associated with Iraqi tank ditches (berm on enemy side). Due to the location of the driver in relation to the vehicle blade, he cannot see the blade or determine when he is about to tip over. The ACE needs a front mounted telescope or a side mounted periscope to overcome this deficiency. The ACE led the way in breaching the border berm between Saudi Arabia and Iraq, and in reducing trench-lines during the assault breach. In both instances the ACE performed extremely well. Problems were encountered, however, due to the ACE's shortcomings. One commander referred to the ACE operator as "Alone, Unarmed, and Unafraid". This highlights the ACE's major shortcomings as a piece of mobility equipment used during direct fire engagements. ACE operators, usually 19 year old PFC's, led the 7th Corps breach into hostile country, alone, unarmed and unafraid. Fortunately, they met with very light resistance. Otherwise, mortality among ACE operators would have been very high. The ACE is a single operator vehicle, without the moral and physical advantages of a crew with an NCO in charge, and without the advantage of a weapon for local suppression. Habitually, manoeuvre task forces provided two Bradley Fighting Vehicles to protect the ACE during breaching ops. While this is a high price to pay for protection of one vehicle, commanders deemed it necessary for the success of their operations. Commanders felt that the ACE needs an additional crewman and a protective weapon such as the .50 calibre's machinegun, or the Mark 19 automatic grenade launcher
BASIS OF ISSUE:
- 7 per Engineer Company in a Heavy Division
- 6 per Armored Cavalry Regiment
- 6 per Engineer Company, Heavy Separate Brigade
- 6 per Engineer Combat Company (Mech) Corps
- 6 per HHC, Engineer Battalion, Light Infantry Division
- 4 per Engineer Company, Separate Infantry Brigade (Ribbon)
- 2 per Engineer Company (Assault Float Bridge)(Ribbon) at Corps
- 1 per Engineer Company (Medium Girder Bridge)
- 1 per Bridge Company (Ribbon)
TRAINING/PERSONNEL: TRADOC instructors and New Equipment Training Teams (NETT) will be trained by the contractor. Initial training will be by NETT for Combat Engineer organizations issued the M9. Institutional training at U.S. Army Engineer Center at Fort Leonard Wood will provide training for the operator (MOS 12F) and maintainer (MOS 62B). Operator proficiency will be maintained by Training Extension Course tapes and extension training materials.
M9 Armored Combat Earthmover
Military VehiclesArmy VehiclesMarine Corps VehiclesArmy EquipmentMarine Corps Equipment
Manufacturer BAE Systems
Service US Army, US Marine Corps
Engine Cummins A903C diesel
Speed 30 mph
Range 200 miles
Combat Engineer Tasks. The M-9 Armored Combat Earthmover is a highly mobile, full-tracked, air transportable armored earthmover and represents a significant enhancement to the combat engineers' capability to support the MAGTF. The M-9 ACE can be employed in a host of engineer tasks, such as clearing obstacles, preparing defilade and survivability positions, and a myriad of engineering construction tasks including dozing, scraping, grading, hauling, towing, and winching.
The M9 ACE is a highly mobile, fully tracked armored earthmover capable of supporting forces in both offensive and defensive operations. It performs critical combat engineer tasks such as digging hull defilade fighting positions for guns, tanks and other battlefield systems to increase their survivability. The ACE breaches berms, prepares anti-tank ditches, prepares combat roads, removes roadblocks and prepares access routes at water obstacles. With the combination of its cross-country mobility and armored protection, the M-9 ACE is capable of both offensive and defensive operations in the forwarded battle area. Additionally, with a cruising range of 200 miles, air transportability, and the ability to swim, the M-9 ACE can maintain the momentum of the maneuvering forces.
The basic structure of the M9 is welded aluminum. The engine, drive train and operator's compartment are laid out in the rear of the vehicle, while the front features an 8.7 cubic yard bowl, apron and dozer blade. Armor consists of welded aluminum with selected steel and aramid-laminated plates. An armored cupola containing eight vision blocks covers the driver's compartment.
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M9 Armored Combat Earthmover
|M9 ACE (Armored Combat Earthmover)|
The upgraded M9 ACE during a bulldozing operation.
|Place of origin||United States|
|Mass||24.4 metric tons, or 36,001 lbs|
|Armor||Classified, resistant to shell splinters and small arms fire, NBC protection|
|Engine||Cummins V903C, 8 cylinder, diesel|
295 hp (220 kW)
|322 km or 200 miles|
|48 km/h or 30 mi/h|
The M9 Armored Combat Earthmover (ACE) is a highly mobile armored tracked vehicle that provides combat engineer support to front-line forces. Fielded by the United States Army, its tasks include eliminating enemy obstacles, maintenance and repair of roads and supply routes, and construction of fighting positions.
The M9 grew out of the Universal Engineer Tractor- "UET", a follow-on to 1958's All-purpose Ballastable Crawler (tractor) or "ABC". By making a small tractor/scraper, it was possible to create a lightweight vehicle that could use local material as ballast. The weight was kept low enough to allow transportation in smaller cargo aircraft, to be air-droppable, and to allow the vehicle to float and swim. Initial development was between the Engineer Laboratory at Fort Belvoir, with International Harvester and Caterpillar. Successful in testing, and exciting a good deal of interest for civilian spin-off, the concept languished after a demonstration, where key decision-makers saw the vehicle sink in front of them while demonstrating its swimming ability.
The UET was originally seen as a squad vehicle, with provision for troop seats in the bowl, and was tested as a cargo vehicle, and even as a mobile mortar carrier.
The M9 is a highly mobile, armored, amphibioustractor, dozer, and scraper. It was finally fielded in 1986, and is capable of supporting forces in both offensive and defensive operations. It performs critical combat engineer tasks such as digging hull defilade fighting positions for guns, tanks and other battlefield systems to increase their survivability. The ACE breaches berms, prepares anti-tank ditches, prepares combat roads, removes roadblocks and prepares access routes at water obstacles.
The engine, drive train and driver's compartment are biased toward the rear of the vehicle, while the front comprises an 8.7 cubic yard (6.7 m³) bowl, apron and dozer blade with a composite aluminum ejector which can unload ballast and or cargo quickly in combat or hostile conditions. Armor consists of welded aluminum with selected steel and aramid-laminated plates. An armored cupola containing eight vision blocks covers the driver's compartment. The vehicle hull is welded and bolted aluminum with a two speed winch capable of 25,000 pound (110 kN) line pull. Towing pintle and airbrake connections are provided. It is equipped with a suspension system which allows the front of the vehicle to be raised, lowered, or tilted to permit dozing, excavating, rough grading and ditching functions. The M9 is armored against small arms and artillery fragmentation, has smoke screening capability, and chemical-biological protection for the operator. Its roadspeed is 30 mph (50 km/h). It is transportable in C-130, C-141, and C-5 aircraft and can swim at 3 mph (5 km/h) under ideal conditions. Since the removal of swim missions as a task for the M9, the swim-related components are not required to be maintained.
By raising the dozer blade and using its scraper blade, the ACE can fill itself with ballast to improve dozing efficiency, it can also be ejected quickly eliminating the need for a bucket loader and dump truck. Another key feature of the M9 is its hydropneumatic suspension system. The principal components are eight high-pressure hydraulic rotary actuators (four on each side) which connect to the roadwheel stations. During high-speed travel, this system assures a smooth ride through the use of shock-absorbing accumulators. In earthmoving operations, the operator rotates the actuators, thus lowering the apron and blade for digging.
A typical combat engineerbattalion will contain 22 ACEs - seven per company plus an operational readiness float. The active Army has a total of 447 M9 ACEs.
The M9 performs mobility, countermobility, sustainability, and survivability tasks in combination with light or heavy combined arms forces. Tasks include the excavation and preparation/reduction of obstacles ie; tank ditches, berms, trees, other hasty obstacles, it can transport wire and other engineering equipment for obstacle emplacements and destruction of enemy counter mobility obstacles, in the ballast area of the bowl behind the movable apron, bridging operations, battle fortified survivability positions, for command posts, air defense, communications equipment and critical supply/logistical/waste management/and bunkers. Other major tasks include route clearance support, and maintaining defensive positions, and offensive breach capability to include transport of mine clearing line charges.
In Operation Desert Storm the ACE proved to be a successful combination of armored vehicle and combat earthmover that was capable of keeping pace with the maneuver units because the ability to fold the blade in half upwards allows for unloaded travel but decreased combat efficiency due to the manual locking pins, which were usually unnecessary unless traveling at high speeds especially with ripper teeth attached. This can sever the blade hinges when not carefully monitored. When traveling downhill at high speeds beware of the next uphill all while providing crew excellent survivability. While some operators are not as efficient as the D7 Dozer in earth moving, some can outpace heavy slow traditional dozers by scraping in clutch brake 2 or three which overcomes lack of cutting ability due to lack of mass with speed. This ability to move with maneuver forces over several hundred kilometers of desert allowed it to successfully perform a wide variety of missions such as construction of combat roads and trails, survivability positions and berms. It can, move as fast as an M1 or M2 over rough terrain, but on improved roads and hardball it is limited to a maximum of 35mph at most with some governors limited to around 27mph. The vehicle operator can adjust to prevent this.
But the training of ACE operators appeared in some units to be inadequate constrained by a lack of technical mechanical expertise and maintenance of hydraulic accumulators systems. Most operators were unfamiliar with the techniques associated with dozing, scraping, cut and fill ops, and grading. The ACE experienced some troubles in reducing the berms associated with Iraqi tank ditches (berm on enemy side). Due to the location of the driver in relation to the vehicle blade, the soldiers have difficulty seeing bottom of blade, while buttoned up through the periscope, but can determine when he is about to tip over with the assistance of the horizon and the top of the blade creating an intersecting angle or with a manual level indicating the degree of slopes that are within acceptable operational capabilities. The ACE operator can use front-mounted telescope or a side-mounted periscope or video monitors to overcome this deficiency, also as load is increased the sound frequency of the engine changes indicating load to the experienced night operators, without the use of electronic or manual gauges. The ACE led the way in breaching the border berm between Saudi Arabia and Iraq, and in reducing trench-lines during the assault breach. The ACE performed beyond its expected capability. Later studies would discover its grim success against the unequipped Iraqi forces, with ACE's of the First Infantry Divisionburying hundreds or thousands of Iraqi soldiers alive in their trenches.
Problems were encountered with the ACE's trainers and maintenance shortcomings. One commander referred to the ACE operator as "Alone, Unarmed, and Unafraid". This highlights the ACE's major shortcomings as a piece of mobility equipment used during direct fire engagements. ACE operators, unsually[check spelling] 19-year-old PFC's, led the 7th Corps breach into hostile country. Fortunately, they met with very light resistance. Otherwise, mortality among ACE operators would have been very high. The ACE is a single operator vehicle,Which section cohesion is pertinent to brigade and above mission success, without the moral and physical advantages of a crew with an NCO in leaderships, maintenance becomes difficult and self discipline and general mechanical and general electrical knowledge is a must for any lower enlisted. This lack of supervision creates highly valued subject matter experts who must understand the commanders intent and geography along with topography during hastily planned operations in austere environments, without the advantage of a weapon for local suppression. Habitually, maneuver task forces provided two M2 along with 2 M1 in diamond formation around valuable operators perhaps more.Bradley Fighting Vehicles to protect the ACE during breaching ops. While this is a high price to pay for protection of one vehicle, commanders deemed it necessary for the success of their operations. Commanders felt that the ACE needed an additional crewman and a protective weapon such as a .50 caliber machine gun or the Mark 19 grenade launcher, in their absence heavy caliber small arms such as the M249squad automatic weapon or M240 bravo are often used..
Basis of issue
- 6 per Engineer Company in a Heavy Division
- 6 per Armored Cavalry Regiment
- 6 per Engineer Company, Heavy Separate Brigade
- 6 per Engineer Combat Company (Mech) Corps
- 6 per HHC, Engineer Battalion, Light Infantry Division
- 4 per Engineer Company, Separate Infantry Brigade (Ribbon)
- 2 per Engineer Company (Assault Float Bridge)(Ribbon) at Corps
- 1 per Engineer Company (Medium Girder Bridge)
- 1 per Bridge Company (Ribbon)
TRADOC instructors and New Equipment Training Teams (NETT) will be trained by the contractor. Initial training will be by NETT for Combat Engineer organizations issued the M9. Institutional training at U.S. Army Engineer Center at Fort Leonard Wood will provide training for the operator (MOS 12F) and maintainer (MOS 91L). Operator proficiency will be maintained by Training Extension Course tapes and extension training materials.
U.S. military support vehicles — 1990 to present
Relevant lists:List of land vehicles of the U.S. Armed Forces — List of currently active U.S. military land vehicles — List of U.S. military vehicles by supply catalog designation — List of U.S. Army tactical trucks — List of U.S. Marine Corps vehicles — List of U.S. Signal Corps Vehicles
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