HEMTT’s story begins in 1978, when the US army conducts a market survey as part of its HMTT (High Mobility Tactical Truck) program. This study served to see if off-the-shelf options existed that could be procured without additional development.
Such NDI (none development items) must be products that were already in use with the US or allied armed forces. This led to truck models from PACCAR, Lockheed, and MAN being tested for adoption.
The results of the survey were positive, and as a result, efforts to procure a series of new trucks intensified. Now not only to supplement the existing fleet of GOER trucks but also to replace them in their entirety.
February 23, 1981On 11/09/1980, TACOM invited 14 vehicle manufacturers to present their technical proposals for this new truck. By February 23, 1981, only Oshkosh, MAN, AM General, and PACCAR had submitted proposals.
These four were then asked to submit bids on development and serial production costs. Only Oshkosh and AM General responded by submitting their bids. Of these, Oshkosh was the cheaper bid and was thus awarded a 5-year contract for the development of the HEMTT.
The Firm-Fixed-Price contract had a value of 251.130.318 USD (roughly 890 million USD today) and included the delivery of several prototypes and 2.140 serial production vehicles with an option for an additional 5.350 vehicles.
Oshkosh Truck Corporation, out of Oshkosh Wisconsen, had participated in this tender with its new 8×8 truck design, which boasted an “extreme” level of offroad mobility while also incorporating a high number of off-the-shelf parts, reducing expected maintenance costs.
All this while offering a 9 metric tonnes cargo capacity (10 US short tonnes). Receiving designation XM977, the new truck now entered final development to become production-ready, and the first prototypes were handed over to the US army.
Development went smoothly, and by March of 1982, the first Low Rate Initial Production (LRIP) vehicles left the production line. After this, 4 more prototype variants would be delivered to the US army with the XM978, XM983, XM984, and XM985.
- tonneneXM977; 8×8 10 tonne Cargo truck
- XM978; 8×8 10 tonne Fuel Tanker Truck
- XM983; 8×8 Tractor Unit
- XM984; 8×8 10 tonne Recovery Truck
- XM985; 8×8 10 tonne Cargo Truck for 227mm MLRS rocket pod transport
These prototypes and LRIP vehicles would then be subjected to intensive user trials. These included mobility trials at the Aberdeen Proving Grounds, where some of the prototypes drove distances of over 30.000 km.
In September of 1982, Oshkosh went over to full-rate production of the HEMTT while US army user trials were still ongoing. As a result, technical problems discovered late in the user trials made their way into the first production vehicle.
These problems were addressed in the coming years, and by 1985, the first HEMTT series trucks went out to active units stationed in West Germany.
Subsequently, HEMTT also started being used to replace older 5-tonne trucks. In these cases, 1 HEMTT replaced 2 of the older 5-tonne trucks.
Mobility-wise, the HEMMT was powered by a 445/450HP Detroit Diesel Corporation 8V92T liquid-cooled V-8 engine coupled with an Allison HT740D automatic transmission capable of bringing the vehicle to a top speed of 92 km/h.
With their 583-litre fuel tank, the vehicle managed a maximum on-road range of 483 km. This all while remaining just compact enough to be transported in a C-130 transport plane.
8 basic variants of the HEMMT entered service in 1985. These being the;
- M977; 8×8 10 tonne Cargo Truck
- M977 EPP 8×8 Truck Mounted Power Plant
- M978; 8×8 Tanker Truck Fuel
- M983; 8×8 Tractor Unit
- M984; 8×8 Wrecker/Recovery Truck
- M984E1; 8×8 Wrecker/Recovery Truck
- M985; 8×8 10 tonne Guided Missile Transporter
- M985E1; 8×8 10 tonne Guided Missile Transporter
Recapitalisation
As the HEMTT continued in US service going into the 2000’s, wear and tear started to bear its toll. When these trucks initially entered service, they were expected to only have a 20-year service life and the earlier models were starting to reach that age.
This leaves the US army with 2 choices: adopt a new truck or patch up the existing fleet in a Life Extension Programme. The US opted for the lather, which kicked off the fleet-wide Recapitalisation programme.
Starting October 2001, HEMTT’s would be returned to Oshkosh, whom would fully strip and rebuild them, replacing worn parts and repairing damage to the chassis.
The main problem with this programme was the lead time between when a truck left for Recapitalisation and when it returned to service with its unit. This led to a programme acceleration effort in December of 2002.
As a result, the time between the vehicles departure from and return to its unit was cut down to less than 100 days. Today more then 14.000 HEMTT have gone through this programme and because of it received the R3 (Recapitalisation, Repair and Return) designation.
Talking about the HEMTT’s variants will be done in 2 parts. First we will look at the chassis variants, after which we will discuss the different mission variants of the truck.
Chassis variants
- HEMTT 6×6; Canada was looking for a new heavy truck in the 1980’s. Oshkosh took part in this competition with a 6×6 model of the HEMTT truck but eventually lost against the Steyr 90 series in 1988.
- HEMTT A1: Only trucks in the M984 and M985 models were ever brought up to the A1 standard, which included the mounting of mission-specific equipment.
- HEMTT A2: These models received a new electronically controlled DDEC II version of the watercooled Detroit Diesel Corporation 8V92TA 8-cylinder diesel engine, a new Allison HD4560P/5 transmission, new seats, and two-part wheels.
Truck models in the A2 range include;
- M977A2; 8×8 10 tonne Cargo Truck
- M977A2 EPP; 8×8 Truck Mounted Power Plant
- M978A2; 8×8 Tanker Truck Fuel
- M983A2; 8×8 Tractor Unit
- M984A2; 8×8 Wrecker/Recovery Truck
- M985A2; 8×8 10 tonne Guided Missile Transporter
- M985E1A2; 8×8 10 tonne Guided Missile Transporter
- M1074A2; 10×10 palletised Load System Trucks
- M1075A2; 10×10 palletised Load System Trucks
- M1120A2; 8×8 palletised Load System Trucks
- HEMTT A2R1: Initially there were no plans to perform upgrades to the HEMTT fleet during recapitalisation, but from 2002 onwards trucks that went trough Recapitalisation would be upgraded to A2 standard. Vehicles brought to A2 standard under Recapitalisation received the A2R1 designation.
Truck models in the A2R1 range include;
- M977A2R1; 8×8 10 tonne Cargo Truck
- M977A2R1 EPP; 8×8 Truck Mounted Power Plant
- M978A2R1; 8×8 Tanker Truck Fuel
- M983A2R1; 8×8 Tractor Unit
- M984A2R1; 8×8 Wrecker/Recovery Truck
- M985A2R1; 8×8 10 tonne Guided Missile Transporter
- M985E1A2R1; 8×8 10 tonne Guided Missile Transporter
- M1120A2R1; 8×8 palletised Load System Trucks
- HEMTT A3: This was a technology demonstrator from Oshkosh and shown off to the US army at the winter exhibition of the Association of the US Army (AUSA). The vehicle was equipped with a hybrid-electric drive system, TAK-4 independent suspension, and a new load handling system. The A3 was put through an 18-month trial period with the US Army but never ended up being adopted.
- HEMTT A4: The A4 is a further upgrade to the A2 model, featuring a Caterpillar C15 diesel engine, a new Allison 4500SP automatic transmission, reworked electronics incorporating the J1939 data bus, and an air spring suspension. As part of the A4’s development, extreme care was taken to ensure parts commonality with other in-service vehicles. One such measure taken was the implementation of a common cab for all A4 models.
Production of this model started in November of 2007. At the same time, vehicles going through recapitalisation also started to be upgraded to A4 standard but did not receive their on-designation like the A2R1.
Truck models in the A4 range include;
- M977A4; 8×8 10 tonne Cargo Truck
- M977A4 EPP; 8×8 Truck Mounted Power Plant
- M978A4; 8×8 Tanker Truck Fuel
- M983A4; 8×8 Tractor Unit
- M984A4; 8×8 Wrecker/Recovery Truck
- M985A4; 8×8 10 tonne Guided Missile Transporter
- M1120A4; 8×8 palletised Load System Trucks
- M1977A4; 8×8 Pontoon Carrier
Mission variants
- M977: This is the initial cargo variant of the HEMTT, sporting a rear flatbed cargo body capable of carrying 10 short tonnes (~9 metric tonnes). At the rear end of the vehicle, a MHC977 telescoping crane is mounted to aid in the loading and unloading of the truck.
- M977 EPP: This is an M977 that has an electric power plant mounted on the cargo bed to provide power to all sorts of systems, including but not limited to radars, command posts, and air defence systems like Patriot.
- M978, the fuel tanker model of the HEMTT family, which can transport a total of 9.463 litres of fuel and has a built-in fuel pump, allowing it to refuel vehicles and aircraft by itself.
- M983: The tractor unit variant means to pull semi-trailers. It is most notably used to transport the various trailer-mounted parts of the Patriot Air Defence System
- M984 Wrecker, Recovery model equipped with a HIAB Model 8109 crane telescoping crane and a shortened rear cargo flat bed. Additionally, the vehicle is equipped with a self-recovery winch capable of pulling loads up to 27 metric tonnes.
This variant’s main purpose is to recover and repair HEMTT family vehicles as well as other lighter vehicles. Shortly after adoption, this model was replaced by the M984E1.
- M984A1: A variant of the M984 equipped with the Grove Model MHC984 telescoping crane.
- M985: A variant of the M977 that is equipped with the MHC985 telescoping crane specifically to handle the M26 rocket and ATACMS missile pods for the M270 MLRS.
- M985E1: A variant of the M977 equipped with the Model 8108 telescoping crane to handle Patriot missile cannisters.
- M1074: A 10×10 variant of the HEMTT equipped with the Multilift Mk5 load handling system, which allows the vehicle to self-load up to 16.5 metric tonnes of cargo. Additionally, this model is equipped with a material handling crane from Grove.
- M1075: A Variant of the M1074 without the Grove material handling crane.
- M1120: This is a model of the HEMTT equipped with the Multilift Mk IV LHS Load Handling System, which allows the truck to load both 20-foot shipping containers, containerised mission modules, and 20-foot flat racks. The Multilift Load Handling System can load cargo weighing up to 11,8 metric tonnes.
- HEMTT THAAD: A modified variant of the M1120 specifically designed to mount the THAAD Missile-Round Pallet launcher that carries 8 THAAD missiles.
M1142: Tactical Fire Truck variant of the HEMTT, which is equipped with a front-mounted roof turret that pumps 500 gallons per minute and a rear turret with a capacity of 250 gallons per minute. These pump from a 1,000-gallon water tank. Pumping wise, the vehicle has a pump capable of moving 1.000 gallons per minute. Lastly, there are 60 gallons of class A foam and 60 gallons of class B foam.
- M1158: A dedicated water tanker variant of the HEMTT to support the M1158. The vehicle has a carrying capacity of 2.500 gallons of water and 50 gallons of class A foam. Additionally, the vehicle is equipped with a 250 gallon per minute rear turret and a 500 gallon per minute pump.
- M1197: This is a variant of the M1120 specially adapted to carry and deploy pontoon bridge elements and small boats.
User base
With over 30.000 units built and its inclusion in both the FMS and EDA mechanisms, the HEMTT has been adopted by a total of 20 countries, including the USA. Among those 20 are;
Bahrain, Brazil, Egypt, Greece, Iraq, Israel, Jordan, Kuwait, Malaysia, Morocco, Oman, Romania, Qatar, Saudi Arabia, South Korea, Taiwan, Turkey, UAE, USA and Ukraine.
Ukraine has received several variants of the HEMTT from the US through military aid packages, including the M984A4 Wrecker, M978 fuel tanker, M1120 Load Handling System and M985 tractor unit, to name just a few.
Replacement
Despite the fleet recapitalisation efforts and introduction of new variants, the HEMTT is reaching the end of her service life. For this reason, the USA has started the Common Tactical Truck programme. The CTT programme is currently evaluating offers from 4 participating companies.
Bids are coming from Mack Defence, Navistar Defence, Oshkosh Defence, and a team made up of American Rheinmetall Vehicles and GM Defence. Each has been tasked with providing several prototype models for physical trails.
The prototypes consist of a M915 Line Haul Truck, an M1088 Medium Tractor Unit, a Palletised Load Handling System, and a Heavy Expanded Mobility Tactical Truck.
A final decision is set to be made in 2026 with a contract for up to 5,700 trucks worth 5 billion USD to be awarded to the winner.
Sources
- Tankograd American Special N3035 HEMTT Heavy Expended Mobility Tactical Truck Development, Technology and Variants—Part 1
- Tankograd American Special N3036 HEMTT Heavy Expended Mobility Tactical Truck Development, Technology and Variants—Part 2
- Battle Order – Who Fights Military-Grade Fires?
- Wikipedia – Heavy Expanded Mobility Tactical Truck
- U.S. Army – Prototyping agreements awarded for Common Tactical Truck program
- DefenceNews – US Army selects four companies to build new tactical truck prototypes
- Wikimedia – 6×6 HEMTT equipped with a cargo-handling crane.JPEG
- T M 9 – 2 3 2 0 – 2 7 9 – 1 0 -1
- PrimePortal – Heavy Expanded Mobility Tactical Truck
- M977 HEMTT – M977 Prototype
