The M577 command post carrier, also known as the M577 command post vehicle or armored command post vehicle, is a variant of the M113 armored personnel carrier that was developed and produced by the FMC Corporation to function on the battlefield as a mobile command post i.e. a tactical operations centre, usually at the battalion level. In U.S. military service its official designation is Carrier, Command Post, Light Tracked M577.
Introduced to the U.S. Army in 1962 it soon saw operational service in the Vietnam War and more recently in the 2003 invasion of Iraq. It is used by many armies around the world and has been adapted for further uses such as an armored ambulance, emergency medical treatment vehicle and fire control vehicle. It is also used by various police forces and law enforcement agencies as a tactical response vehicle.
The M577 is easily distinguished from the M113 upon which it is based by its raised upper hull and roof-mounted auxiliary power unit (APU). Vehicles are generally unarmed.
Background The experience gained by the U.S. Army in the Second World War showed that close co-operation between infantry and armored forces is a necessity for combined-arms mechanized mobile warfare. Mobile warfare increases both the scope and size of the theatre of operations, and mobile command and control posts are necessary to co-ordinate operations at the divisional, brigade and battalion levels.
Whereas tanks and armored cars offered a level of protection against weapons fire, they usually did not provide sufficient internal room to permit the extra personnel needed to operate all the radio sets. Lightly or unarmed vehicles could be used to transport temporary structures (e.g. tents) that gave greater work space, but these structures lacked protection from direct and indirect weapons fire, and advancing front line units could exceed the communication range the command post, necessitating the dismantling and removal of the structure to a new location. Experience gained in the snow and mud in the Korean War showed the advantage of tracked over wheeled vehicles.
In 1960, no such vehicle existed in the U.S. Army inventory that was able to satisfy all of these requirements.
Development
The first four prototypes were built in February 1962 by United Defense Industries at the U.S. Army's Detroit Arsenal. They were designated the XM577, and were conversions of M113 APCs. Upon completion in March 1962 the first vehicle was shipped to the Aberdeen Proving Ground for engineering tests, while the remaining three vehicles were shipped to the Armor, Infantry and Artillery Boards for evaluation tests.
The results of all tests were generally positive, and the vehicle went into immediate production. The first batch of 270 vehicles were accepted into U.S. Army service between in December 1962 and March 1963. In March 1963 under Standard A Acceptance the XM577 was redesignated as the M577, indicating official status as a regular production vehicle. Production began on a second batch of 674 vehicles in November 1963, all of which entered service by the middle of 1964.
Design
M577 Man inside standing
Chassis and hull The M577 shares the chassis, lower hull and running gear from the M113 upon which it is based. The hull sides from the engine firewall to the rear cargo ramp were extended by for a maximum headroom in the rear compartment of , allowing operators to perform duties standing up. On the roof, the commander's cupola of the M113 APC has been replaced with circular hatch similar to the driver's hatch, and the large rectangular hatch over the troop compartment was removed. There is no external weapons stations fitted to the M577, although most vehicles were fitted with an internal rifle rack.
Electrical system Mounted to the front of the raised upper hull, centrally located to the right of the driver's hatch, is a 4.2 kW 28V 150A gasoline auxiliary power unit generator, that provides power to the M577/M1068's auxiliary equipment, dependent upon variant as specified below, without the vehicle's main engine running. The unit can be used to power two vehicles, and can be removed from its mounting basket using a lifting davit located on the vehicle's roof and operated from within or alongside the vehicle using a extension cable.
As part of the A3 upgrade, a more powerful 5.0 kW unit was fitted. Unlike the previous gasoline-fuelled unit, the new unit operates on diesel fuel, providing more hours of operation on an equivalent fuel load.
Interior The single 80 gallon internal fuel tank of the M113, located at the rear left, is replaced by two 60 gallon tanks, located each side near the rear, providing a greater operating range than a M113. They also serve as the base for fold-out tables. Radios are usually fitted along the left wall, as well as the front of the right wall. Map boards are usually fitted along the walls, along with additional storage facilities for maps and code books etc.
Overhead dome lights were fitted within the rear compartment. A personal heater is located at the front right of the compartment, which serves as an equipment heater in Arctic and winter operations.
A 5-man bench seat could be fitted to either or both sides of the rear compartment, although in some vehicles no seating was fitted whatsoever. The rearward-facing seat on the commander's station was removed. For the M1068, inward-facing individual seats for two operators replaced the bench seat. Further folding tables and chairs are often carried, stowed while the vehicle is in transit.
Equipment Equipment fitted within the rear compartment of the M577/M1068 varies according to the vehicle's purpose.
Command post vehicles Vehicles are equipped with additional radio sets as found in a standard M113 APC, to provide command and control facilities across the unit (e.g. battalion) and coordinate with other units and higher levels of command (e.g. regimental HQ). Removable antenna masts are usually carried and attached to the vehicle's roof.
In U.S. Army service, each vehicle usually carries three of four different communications suites (radio sets), each providing a specific communication network according to the communications roles they were assigned e.g. to divisional headquarters, across all vehicles within the unit (battalion), etc. The suites operated over amplitude modulation (AM), continuous wave (CW) and frequency modulation (FM), with the frequencies and number of channels, and transmission and reception range determined by the set. Communication suites were originally analogue, but with the introduction of the M577A3 and A4, have mostly been upgraded to digital. Analogue radio sets fitted to the M577 in U.S. service include:
AM/CW: AN/GRC-19 AN/VRC-24 AN/CRR-5 AN/WRC-29 FM (original): AN/VRC-3 to AN/VRC-8 AN/VRC-10 AN/VRC-13 to AN/VRC-15 AN/VRC-20 to AN/VRC-22 FM (later): AN/VRC-26 AN/VRC-46, AN/VRC-47 AN/VIC-1 Interphone: AN/DIC-1 Teletype: AN/GRC-24
Medical vehicles It must be recognized that there was no such thing as a standardized M577 medical vehicle. Vehicles were configured according to the country operating them and internal configuration and equipment varied accordingly, which was also defined as to whether they were used as an emergency evacuation (ambulance) or treatment vehicles.
In U.S. service it appears that M577s were only used as emergency evacuation vehicles very early in their operation careers, i.e. in the early years of the Vietnam War. This role was soon provided solely by M113 "armored ambulances", and the M577 was then only used as emergency treatment vehicles (e.g. battalion aid stations).
When configured as an ambulance, compared to a M113 which could be fitted with up to four litters, the extra room inside the M577 allowed it to carry two additional litters i.e. up to a maximum of six.
Other variants Vehicles configured for other roles were configured with specialized equipment accordingly e.g. M577 Fire Control Vehicles were often fitted with TACFIRE artillery control consoles.
Tent extension
A tent extension attaches to the rear of the vehicle above and around the rear cargo ramp, increasing the workspace available to operators, and in the case of the emergency treatment vehicles, to function as a field dressing station or hospital. The tent is erected over collapsible steel tubing, which is carried in brackets on the rear of the vehicle. The tent can be connected to up to four vehicles parked in a cross, to provide a common work area.
With the introduction of the M1068 SICPS Carrier, the M577-specific tent was replaced with a Modular Command Post System (MCPS) tent, which attaches to the rear of the vehicle by a "bootwall" that covers the rear of the vehicle but still has an entrance to the vehicle's interior. The MCPS tent has the advantage of being quicker and easier to erect and dismantle, provides overhead lighting and power sockets for electrical equipment, and the modular design of MCPS allows more tents to be easily connected.
Production Ownership of title for and production of the M577 has changed many times over the vehicle's history due to corporate buy-outs and take-overs. Originally produced by FMC's combat vehicles division United Defense Industries (UDI), in 1995 UDI was purchased by Harsco Corporation to become United Defense (UD). In 2005 UD was then purchased by BAE Systems (BAE). As of February 2020, the M577 is within the company's Global Combat Systems Ground Vehicles portfolio of current products in the subsidiary BAE Systems Platforms & Services.
The M577 is produced or remanufactured locally in several countries under licence from or in partnership with BAE. This includes: Australia, by Tenix Defence Germany, by Flensburger Fahrzeugbau GmbH (FFG) Italy, by OTO Melara South Korea, by Daewoo Heavy Industries Taiwan, by the Republic of China Armoured Vehicle Development Center Turkey, by FNSS Defence Systems
In total, more than 7,300 vehicles have been built, of which around 3,900 were M577A1, making the M577 the most numerous single variant of the M113 family after the APC.
Basic versions The M577 has followed a similar upgrade path to the M113 upon which it is based, resulting in the following basic versions:
M577 The original version based upon the M113 chassis. Specifications and performance are as follows: Engine Chrysler 75M5.9L V8 4-stroke gasoline @4000rpm Transmission Allison TX-200-2A4 forward, 1 reverse gears Weight (combat load) 10.8 t Power/weight 19.4 hp/t Ground pressure 0.53 kg/cm² Maximum speed road: water: Average cross-country speed not available Acceleration 0-20 mph 12.0 seconds Operating range
M577A1 The initial upgraded version based upon the M113A1, introduced in 1964. The gasoline engine was replaced with a more powerful diesel engine, providing better fuel economy and a greater operating range, as well as the reducing the fire hazard of gasoline fuel. Specifications and performance are as follows: Engine Detroit Diesel 6V-535.2L V6 2-stroke diesel @2800rpm Transmission Allison TX-100-13 forward, 1 reverse gears Weight (combat load) 11.1 t Power/weight 19.1 hp/t Ground pressure 0.55 kg/cm² Maximum speed road: water: Average cross-country speed not available Acceleration 0-20 mph 10.5 seconds Operating range
M577A2 In 1979, further upgrades were introduced based on the M113A2. Engine cooling was improved by switching the locations of the fan and radiator. Higher-strength torsion bars increased ground clearance, and shock absorbers reduced the effects of ground strikes. Increased weight affected the vehicle's freeboard when afloat, and it was no longer required to be amphibious. Four-tube smoke grenade launchers were added on each side of the trimvane on the front of the vehicle.
Specifications and performance are as follows: