M109 howitzer

M109 Howitzer
Canadian M109
Type	Self-propelled artillery
Place of origin	United States
Service history
Wars	Vietnam War Yom Kippur War Iran–Iraq War Western Sahara War Gulf War Iraq War Saudi Arabian-led intervention in Yemen
Specifications
Weight	27.5 tons
Length	30 ft (9.1 m)
Width	10 ft 4 in (3.15 m)
Height	10 ft 8 in (3.25 m)
Crew	6 (2 Loaders, Gunner, Assistant Gunner, Commander, Driver)

Shell	separate loading, bagged charge
Caliber	155 mm L/39 caliber^[1]
Breech	interrupted screw
Traverse	360°
Rate of fire	Maximum: 6 rpm Sustained: 3 rpm
Effective firing range	Conventional: 18 km (11 mi) RAP: 30 km (19 mi)

Main armament	M126 155 mm Howitzer
Secondary armament	.50 caliber (12.7 mm) M2 machine gun
Engine	Detroit Diesel 8V71T 450 hp (335.56 kW)
Power/weight	18.7 hp/t
Suspension	torsion-bar
Operational range	216 mi (350 km)
Speed	35 mph (56 km/h)

The M109 is an American 155mm self-propelled howitzer, first introduced in the early 1960s. It has been upgraded a number of times, most recently to the M109A7. The M109 family is the most common Western indirect-fire support weapon of maneuver brigades of armored and mechanized infantry divisions.

The M109 has a crew of six: the section chief, the driver, the gunner, the assistant gunner and two ammunition handlers. The gunner aims the cannon left or right (deflection), the assistant gunner aims the cannon up and down (quadrant). The M109A6 Paladin needs only a crew of four: the commander, driver, gunner and an ammunition loader.

The British Army replaced its M109s with the AS-90. Several European armed forces have or are currently replacing older M109s with the German PzH 2000. Upgrades to the M109 were introduced by the U.S. (see variants below) and by Switzerland (KAWEST). With the cancellation of the U.S. Crusader and Non-Line-of-Sight Cannon, the Paladin will remain the principal self-propelled howitzer for the U.S. for the foreseeable future.

History

The M109 was the medium variant of a U.S. program to adopt a common chassis for its self-propelled artillery units. The light version, the M108 Howitzer, was phased out during the Vietnam War, but many were rebuilt as M109s.

The M109 saw its combat debut in Vietnam. Israel used the M109 against Egypt in the 1973 Yom Kippur War and in the 1982 and 2006 Lebanon Wars. Iran used the M109 in the Iran–Iraq War in the 1980s. The M109 saw service with the British, Egyptian and Saudi Arabian Armies in the 1991 Gulf War. The M109 also saw service with the U.S. Army in the Gulf War, as well as in the Iraq War from 2003 to the present.

Upgrades to the cannon, ammunition, fire control, survivability, and other electronics systems over the design's lifespan have expanded the system's capabilities, including tactical nuclear projectiles, Cannon Launched Guided Projectiles (CLGP or Copperhead), Rocket Assisted Projectile (RAP), FAmily of SCAtterable Mines (FASCAM), and improved conventional munitions (the Dual-Purpose Improved Conventional Munition, DPICM).

Design

The M109 was developed by the Ground System Division of United Defense LP (now BAE Systems Land and Armaments).^[1]

Armament

Open breech of M109A5 howitzer

Primary: M126 (or M126A1) 155 mm Howitzer (M109), M185 155 mm Howitzer (A1/A2/A3/A4), M284 155 mm Howitzer (A5/A6)
Secondary: .50 caliber (12.7 mm) M2 machine gun, Mk 19 Mod 3 40 mm Automatic Grenade Launcher, or 7.62 mm M60, M240 machine gun or L4 machine gun

Railgun HVP

In January 2016, the U.S. Army test-fired hypervelocity projectiles originally designed for use by U.S. Navy electromagnetic railguns and found that they significantly increase the gun's range. The Army is looking into using the M109 Paladin firing the HVP for ballistic missile defense, as traditional missile interceptors are expensive and gun-based missile defense used for point defense would utilize artillery already in the inventory at a much lower cost per round.^[2]^[3] The HVP costs $25,000 per round and is capable of being fired out to 50 nautical miles (58 mi; 93 km) from a conventional cannon. It weighs 68 lb (31 kg) with a 23 lb (10 kg) flight body containing its guidance and warhead, less powerful but more agile to hit small, high-speed targets. Modifications will be needed for the Paladin to effectively shoot the HVP, possibly including different propellant to achieve higher velocities, automated reloading systems to fire quickly enough to defeat salvo launches, improved barrel life, and a new fire control and sensor system.^[4]

Variants

M109

An M109 entering South Vietnam

First produced in 1963. It had a 23 caliber 155 mm M126 gun in an M127 Howitzer Mount, and carried 28 rounds of 155 mm ammunition. It was also armed with a .50cal M2HB machine gun with 500 rounds of ammunition. Easily identified by its short barrel and a double baffle muzzle brake with a large fume extractor just behind it. Maximum range of 14 600 m.

M109A1

Replaced the M126 gun with a longer barreled, 39 caliber M185 gun, increasing maximum range to 18 100 m.

M109A2

Incorporated 27 Reliability, Availability, and Maintainability (RAM) mid-life improvements. Most notably, the long barreled 155 mm M185 cannon in the new M178 gun mount, ballistic protection for the panoramic telescope, counterbalanced travel lock, and the ability to mount the M140 alignment device. Stowage increased from 28 rounds of 155 mm, to 36 rounds; .50cal ammunition remained at 500 rounds. During M109A2 production, a slightly simplified version was also produced for export. This had minor internal changes and deleted the hull flotation feature. These were designated M109A1B.^[5]

M109A3 and M109A3B

M109A1s and M109A1Bs rebuilt to M109A2 standard respectively. Some A3s feature three contact arm assemblies, while all A2s have five.

M109A4

M109A2s and M109A3s improved with Nuclear, Biological, and Chemical / Reliability, Availability, and Maintainability (NBC/RAM) improvements, including air purifiers, heaters, and Mission Oriented Protective Posture (MOPP) gear.

The traversing mechanism's clutch is hydraulic, as compared to the electric mechanism on previous M109s, and features a manual override in the event of an electrical failure. The A4 also adds an additional hydraulic filter, for a total of two. Also included is an improvement to the engine starting equipment, greatly improving the ability to start in an emergency.

Ammunition amounts remain the same as two previous models.

M109A5

Replaces the 155 mm M185 cannon in an M178 mount with a 39-caliber 155 mm M284 cannon in an M182 mount, giving the A5 a maximum range of 23,500 meters with unassisted projectiles and 30,000 meters with Rocket Assisted Projectiles (RAP Rounds). The vehicle can carry 36 complete rounds of ammunition and has a 440 hp engine instead of the standard 405 hp engine.

M109A5 under repair

M109A5+

Various manufacturers have upgraded the fire control and other components of the M109A5. BAE Systems in York PA recently delivered 12 M109A5+ vehicles to Chile.

M109A6 "Paladin"

M109A6 "Paladin" firing at night

An M109A6 firing a shell during combat operations in Fallujah, Iraq

Overall product improvement in the areas of survivability, RAM, and armament. This includes increased armor, redesigned (safer) internal storage arrangement for ammunition and equipment, engine and suspension upgrades, and product improvement of the M284 cannon and M182A1 mount. The greatest difference is the integration of an inertial navigation system, sensors detecting the weapons' lay, automation, and an encrypted digital communication system, which utilizes computer controlled frequency hopping to avoid enemy electronic warfare and allow the howitzer to send grid location and altitude to the battery fire direction center (FDC). The battery FDCs in turn coordinate fires through a battalion or higher FDC. This allows the Paladin to halt from the move and fire within 30 seconds with an accuracy equivalent to the previous models when properly emplaced, laid, and safed—a process that required several minutes under the best of circumstances. Tactically, this improves the system's survivability by allowing the battery to operate dispersed by pairs across the countryside and allowing the howitzer to quickly displace between salvos, or if attacked by indirect fire, aircraft, or ground forces.

Ammunition stowage is increased from 36 to 39 155 mm rounds.

M109 "KAWEST"

Swiss M109 KAWEST howitzer in 2009

This Swiss improved version produced by Ruag incorporates a new Swiss-designed L47 155 mm gun with an increased firing range of up to 36 km. The L47 155 mm gun is derived from the Swiss Bison fortress gun's inertial navigation system coupled with a new gun-laying system and more ammunition storage. The KAWEST (lit. Kampfwertsteigerung = upgrade of combat capabilities) requires only 6 crew members instead of 8, and is able to fire 3-round bursts within 15 seconds or maintain a constant firing rate of over one round per minute.

Technical modifications:

Increased firing range of up to 27 km, increased rate of fire (burst of 3 rounds in 15 sec.), increased ammunition autonomy (40 rounds, 64 charges).
New electrical system increases reliability (better than Mil STD 1245A, higher operational readiness, increased mean time between failures, fault-finding diagnostics with test equipment.)
Integrated inertial navigation and positioning system, increased mobility (gears, engine), day and night operations capabilities, effective fire suppression system installed, NEMP and EMP protection. Camouflage: paint and netting.
Upgraded Swiss PzHb (Panzerhaubitze) 79 and 88 (M109A1) are known as respectively PzHb 79/95 and PzHb 88/95.

M109L52

Jointly developed by the Dutch firm RDM and the German firm Rheinmetall, the M109L52 was first revealed in 2002. The main improvement was replacing the M126 series gun with the longer 52-caliber cannon from the PzH 2000, thus the MTLS ammunition of the PzH 2000 can be used. In addition, improvements to the loading system were made. This resulted in an increase of the rate of fire to 9–10 rds/min from the original 3 rds/min, and this high rate of fire can be sustained for up to 2 minutes. A total of 35 rounds can be carried.

M109A3GNM

The current version in use in the Norwegian Army. Brigade Nord's artillery support unit, Artilleribataljonen, has three Batteries using this.

K55/K55A1

K55/K55A1 are South Korean variants of the M109, originally based on M109A2 with additional domestic augmentations, license-produced by Samsung Techwin. They are fitted with NBC protection, automatic fire extinguishing system, and a modified ammunition reception module for K56 automatic ammunition resupply vehicle.^[6] The Performance Improvement Program variant, K55A1, is a complete domestic overhaul of the K55^[7] which is further augmented by Samsung Thales with modern digital ballistic computers, multifunctional data display and controllers, GPS navigation and target acquisition system, wireless datalink equipment, and upgraded fire control storage battery and power supply unit,^[8] to closely match the US military's modernization of the Paladin into next-generation standard. Many improved technologies of the South Korean K9 Thunder were retrofitted on the K55A1. 1,040 howitzers of these variants were produced.

M109A7

Prototype

The newest M109 version for U.S. service is the M109A7, formerly known as the M109A6 Paladin Integrated Management (PIM). The M109A7 shares common components with the Bradley Fighting Vehicle such as the engine, transmission, and tracks. This creates commonality with other systems and maximizes costs-savings in production, parts inventory, and maintenance personnel. The M109A7's on-board power systems harness technologies originally developed for the Non-Line-of-Sight Cannon; the electric drive is faster than the previous hydraulic system, and the automatic rammer more consistently rams the round into the gun for consistent velocities and better accuracy. It features a 600-volt on-board power system to accommodate additional armor and future networking technologies as they become ready. The M109A7 can sustain a one round per-minute rate of fire and a maximum rate of fire of four rounds per-minute.^[9] Weighing 78,000 lb (35,000 kg), the M109A7 is 10,000 lb (4,500 kg) heavier than its predecessor, and it has the capacity grow to 110,000 lb (50,000 kg). Even with the weight increase, the M109A7 can travel faster than previous versions at 38 mph (61 km/h) and is more maneuverable than a Bradley Fighting Vehicle.^[10]

Prototypes of the vehicle underwent government testing in preparation for a low-rate initial production decision. The testing included reliability, availability, and maintainability mission testing as well as ballistic hull and turret testing. M109A7 was slated to begin low-rate initial production by 2013. The U.S. Army plans on procuring a fleet of 580 sets of M109A7 howitzers and M992A3 ammunition support vehicles.^[9]

In October 2013, the Defense Acquisition Board approved the decision to start M109A7 production. The FY 2014 budget called for $340.8 million in Paladin funding, which would be two dozen vehicle sets at $14.4 million per vehicle. The Army plans to buy 133 vehicles in 66 one-half vehicle sets starting in 2014, although one M109A7 howitzer and two supporting M992A3 ammunition carriers will be destroyed during tests. A full-rate production decision planned for February 2017.^[11]^[12] On 31 October 2013, BAE received a $668 million contract to begin low-rate initial production of the M109A7.^[13] The first M109A6 and M992A2 vehicles were disassembled and reassembled to M109A7 and M992A3 standard as part of low-rate initial production beginning in summer 2014.^[14] Low-rate production deliveries began in April 2015.^[15]

Derivatives

M992

Main article: M992 Field Artillery Ammunition Support Vehicle

The Field Artillery Ammunition Supply Vehicle (FAASV) is built on the chassis of the M109-series. It is also colloquially referred to as a "CAT" (referring to its nomenclature, CAT: Carrier, Ammunition, Tracked). It replaces the M548 supply vehicle. Unlike the M548, it is armored. This ammunition vehicle has no turret, but has a taller superstructure to store 93 rounds and an equivalent number of powders and primers. There is a maximum of 90 conventional rounds, 45 each in two racks, and 3 M712 Copperhead rounds. Until recently, much of the remaining internal crew space was taken up by a hydraulically powered conveyor system designed to allow the quick uploading of rounds or transfer of rounds to the M109-series howitzer. Most early models had an additional mechanism called an X-Y Conveyor to lift the rounds into the honeycomb-like storage racks in the front of the superstructure. A ceiling plate above the two racks can be unbolted and opened to allow the racks to be winched out of the vehicle. This vehicle is fitted with a Halon fire suppression system and a weapons mount similar to that on the M109 turret, usually mounting a Mk 19 grenade launcher for local defense against infantry and light armored vehicles. The latest models have a mounting point for two secure radios.

The hydraulic conveyor system is removed by crews as it is slower than moving the rounds by hand. Recently the army has removed the conveyor system and changed the two horizontal opening doors to two vertical doors opening from the center to provide protection to the crew during transfers.

The vehicle also contains a 2-stroke diesel powered auxiliary power unit that can power all non-automotive energy requirements on the Field Artillery Ammunition Supply Vehicle and on the howitzer when a slave cable is used to connect the two. This reduces fuel consumption when mobility is not required.

Training systems

The US Army uses the Fire Support Combined Arms Tactical Trainer (FSCATT) in two versions for initial and sustainment training of the M109A6 and M109A5.^[16] The system uses an actual surplus turret and a simulated ammunition system.

The Swiss Army uses a highly advanced KAWEST trainer from Van Halteren Metaal of the Netherlands.

The Dutch, Belgian, Thai, and Israeli Armies have various configurations of the Van Halteren Metaal LARIT M109 trainer.

Operators

Map of M109 operators in blue with former operators in red

M109 of the Egyptian Army during Operation Bright Star