Aiming and Mobility of M1 Abrams

Aiming of M1 Abrams

The M1 Abrams is equipped with a ballistic fire-control computer that uses data from a variety of sources, including the thermal or daylight Gunner's Primary Sight (GPS), all computing and displaying one of three components of the ballistic solution - lead angle, ammunition type, and range to the target. These three components are determined using a laser rangefinder, crosswind sensor, a pendulum static cant sensor, data on the ammunition type, tank-specific bore sight alignment data, ammunition temperature, air temperature, barometric pressure, a muzzle reference sensor (MRS) that determines and compensates for barrel droop at the muzzle due to gravitational pull and barrel heating due to firing or sunlight, and target speed determined by tracking rate tachometers in the Gunner's or Commander's Controls Handles allowing for target speed input into the ballistic solution.

The fire-control of M1 Abrams system uses these data to compute a firing solution for the gunner. The ballistic solution generated ensures a hit percentage greater than 95 percent at nominal ranges. Either the commander or gunner can fire the main gun. Additionally, the Commander's Independent Thermal Viewer (CITV) on the M1A2 can be used to locate targets and pass them on for the gunner to engage while the commander scans for new targets. In the event of a malfunction or damage to the primary sight system, the main and coaxial weapons can be manually aimed using a telescopic scope boresighted to the main gun known as the Gunner's Auxiliary Sight (GAS). The GAS has two interchangeable reticles; one for HEAT and MPAT (MultiPurpose AntiTank) rounds and one for APFSDS and STAFF (Smart Target-Activated Fire and Forget) ammunition. Turret traverse and main gun elevation can be accomplished with manual handles and cranks in the event of a Fire Control System or Hydraulic System failure. The commander's M2 .50 caliber machine gun on the M1 and M1A1 is aimed by a 3x magnification sight incorporated into the Commander's Weapon Station (CWS), while the M1A2 uses either the machine gun's own iron sights, or a remote aiming system such as the CROWS system when used as part of the TUSK (Tank Urban Survival Kit). The loader's M240 machine gun is aimed either with the built-in iron sights or with a thermal scope mounted on the machine gun.

Mobility of M1 Abrams

The M1 Abrams is powered by a 1500 hp (1119 kW) Honeywell AGT 1500 (originally made by Lycoming) gas turbine, and a six speed (four forward, two reverse) Allison X-1100-3B Hydro-Kinetic automatic transmission, giving it a governed top speed of 45 mph (72 km/h) on paved roads, and 30 mph (48 km/h) cross-country. With the engine governor removed, speeds of around 60 mph (97 km/h) are possible on an improved surface; however, damage to the drive train (especially to the tracks) and an increased risk of injuries to the crew can occur at speeds above 45 mph (72 km/h). The tank for all intents and purposes was built around this engine. The tank can be fueled with diesel fuel, kerosene, any grade of motor gasoline, JP-4 jet fuel, or JP-8 jet fuel; the US Army uses JP-8 jet fuel in order to simplify logistics. The Royal Australian Armoured Corps' M1A1 AIM SA uses diesel fuel; it is cheaper and makes practical sense for Australian military logistics.

The gas turbine propulsion system has proven quite reliable in practice and combat, but its high fuel consumption is a serious logistic issue (starting up the turbine alone consumes nearly 10 gallons of fuel). The engine burns more than 1 gallon per mile and 12 gallons per hour when idle. The high speed, high temperature jet blast emitted from the rear of M1 Abrams tanks makes it difficult for the infantry to proceed shadowing the tank in urban combat. The turbine is very quiet when compared to diesel engines of similar power output and produces a significantly different sound from a contemporary diesel tank engine, reducing the audible distance of the sound, thus earning the Abrams the nickname, "whispering death" during its first REFORGER exercise.

Honeywell was developing another gas turbine engine with General Electric for the XM2001 Crusader program that was also to be a replacement for the AGT-1500 engine already in the Abrams tank. The new LV100-5 engine is lighter and smaller (43% fewer parts) with rapid acceleration, quieter running and no visible exhaust. It also features a 33% reduction in fuel consumption (50% less when idle) and near drop-in replacement. The Abrams-Crusader Common Engine Program was shelved when the Crusader program was canceled, however Phase 2 of Army's PROSE (Partnership for Reduced O&S Costs, Engine) program calls for further development of the LV100-5 and replacement of the current AGT-1500 engine. Future US tanks may return to reciprocating engines for propulsion, as 4-stroke diesel engines have proven quite successful in other modern heavy tanks, e.g. the Leopard 2, Challenger 2 and Merkava.

Using a high power density 330 cc Wankel rotary engine modified to use diesel and military grade jet fuel, TARDEC developed a 220-pound Auxiliary Power Unit designed to fit into the M1 Abrams, replacing an existing battery pack that weighs about 500 pounds. The new APU will also be more fuel efficient. The installation of the first APUs is expected to start in 2009.

The M1 Abrams can be carried by a C-5 Galaxy or a C-17 Globemaster III. The limited capacity (two combat-ready in a C-5, one combat-ready tank in a C-17) caused serious logistical problems when deploying the tanks for the First Gulf War, though there was enough time for 1,848 tanks to be transported by ship.