M9 Armored Combat Earthmover

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M9 ACE (Armored Combat Earthmover)
M9 ACE (Armored Combat Earthmover)
General characteristics
Crew	1
Length	6.2 m
Width	3.2 m
Height	3 m
Weight	24.4 tonnes
Armour and armament
Armour	mm
Main armament	None
Secondary armament	None
Mobility
Power plant	Cummins V903C, 8 cylinder, diesel 295 hp ( kW)
Suspension	Hydropneumatic
Road speed	50 km/h
Power/weight	hp/tonne
Range	320 km

The M9 (ACE) Armored Combat Earthmover is a United States 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 U.S. combat engineer battalion will contain 22 ACES - seven per company plus an operational readiness float. The United States 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.

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