Humvee

The High Mobility Multipurpose Wheeled Vehicle (HMMWV), commonly known as the Humvee, is a four-wheel drive military light truck produced by AM General.[7] It has largely supplanted the roles originally performed by the original jeep, and others such as the Vietnam-era M151 1/4 ton, the M561 "Gama Goat", their M718A1 and M792 ambulance versions, the Commercial Utility Cargo Vehicle (CUCV), and other light trucks. Primarily used by the United States military, it is also used by numerous other countries and organizations and even in civilian adaptations. The Humvee's widespread use in the Persian Gulf War, where it negotiated the treacherous desert sand with ease, helped inspire the civilian Hummer automotive marque.

History
Since the WWII era Bantam Reconnaissance Car, the United States Army had relied on jeeps to transport small groups of soldiers. The jeep was built around a requirement for a compact vehicle with a folding windshield that was actually shorter than the Volkswagen Beetle. It seated three with a 660 lb (300 kg) payload and weighed just over one ton. By the 1970s, the U.S. Army had tried larger militarized civilian trucks, but even these no longer satisfied newer requirements. In 1977, Lamborghini developed the Cheetah model in an attempt to meet the Army contract specifications.

In 1979, the U.S. Army drafted final specifications for a High Mobility Multipurpose Wheeled Vehicle, or HMMWV, which was to replace all the tactical vehicles in the 1/4 to 1 1/4-ton range,[8] namely the M151 quarter-ton jeep and M561 Gama Goat, as one "jack-of-all-trades" light tactical vehicle to perform the role of several existing trucks.[9] The specification called for excellent on and off-road performance, the ability to carry a large payload, and improved survivability against indirect fire.[10] Compared to the jeep, it was larger and had a much wider track, with a 16 in (410 mm) ground clearance, double that of most sport-utility vehicles. The new truck was to climb a 60 percent incline and traverse a 40 percent slope. The air intake was to be mounted flush on top of the right fender (or to be raised on a stovepipe to roof level to ford 5 ft (1.5 m) of water[11] and electronics waterproofed to drive through 2.5 ft (0.76 m) of water were specified. The radiator was to be mounted high, sloping over the engine on a forward-hinged hood.

Out of 61 companies that showed interest, only three submitted prototypes.[10] In July 1979, AM General (a subsidiary of American Motors Corporation) began preliminary design work. Less than a year later, the first prototype was in testing; Chrysler Defense and Teledyne Continental also produced competing designs. In June 1981, the Army awarded AM General a contract for development of several more prototype vehicles to be delivered to the government for another series of tests. The original M998 A0 series had a curb weight of 5,200 lb (2,400 kg). with a payload of 2,500 lb (1,100 kg), with a 6.2 L (380 cu in) V-8 diesel engine and a three-speed automatic transmission.

The three companies were chosen to design and build eleven HMMWV prototypes, which covered over 600,000 miles in trials which included off-road courses in desert and arctic conditions. AM General was awarded an initial contract in 1983 for 2,334 vehicles, the first batch of a five-year contract that would see 55,000 vehicles delivered to the U.S. military, including 39,000 for the Army; 72,000 vehicles had been delivered to U.S. and foreign customers by the 1991 Gulf War, and 100,000 were delivered by the Humvee's 10th anniversary in 1995.[9] Ft. Lewis, Washington and the 9th Infantry Division was the testing unit to employ HMMWV in the new concept of a motorized division. Yakima Training Center in Yakima, Washington was the main testing grounds for HMMWVs from 1985 through December 1991, when the motorized concept was abandoned and the division inactivated.

Usage in combat
HMMWVs first saw combat in Operation Just Cause, the U.S. invasion of Panama in 1989.

The HMMWV was designed primarily for personnel and light cargo transport behind front lines, not as a front line fighting vehicle.[dubious – discuss] Like the previous jeep, the basic HMMWV has no armor or protection against chemical, biological, radiological or nuclear threats. Nevertheless, losses were relatively low in conventional operations, such as the Gulf War. Vehicles and crews suffered considerable damage and losses during the Battle of Mogadishu due to the nature of the urban engagement; however, the chassis survivability allowed the majority of those crews to return to safety, though the HMMWV was never designed to offer protection against intense small arms fire, much less machine guns and rocket-propelled grenades. However, with the rise of asymmetric warfare and low intensity conflicts, the HMMWV was pressed into service in urban combat roles for which it was not originally intended.

After Operation Restore Hope in Somalia, the military recognized a need for a more protected HMMWV and AM General developed the M1114, an armored HMMWV to withstand small arms fire. The M1114 has been in limited production since 1996, seeing limited use in the Balkans before deployment to the Middle East. This design is superior to the M998 with a larger, more powerful turbocharged engine, air conditioning, and a strengthened suspension system. More importantly, it boasts a fully armored passenger area protected by hardened steel and bullet-resistant glass. With the increase in direct attacks and guerrilla warfare in Iraq, AM General diverted the majority of its manufacturing power to producing these vehicles.

Humvees were sent into Afghanistan following the 9/11 terrorist attacks, where they proved invaluable during initial operations. In the early years before IEDs became prevalent, the vehicle was liked by troops for its ability to access rough, mountainous terrain. Some soldiers would remove features from Humvees, including what little armor it had and sometimes even entire doors, to make them lighter and more maneuverable for off-road conditions and to increase visibility. With the onset of the Iraq War, Humvees proved very vulnerable to IEDs; in the first four months of 2006, 67 U.S. troops died in Humvees. To increase protection, the U.S. military hastily added-on armor kits to the vehicles. Although this somewhat improved survivability, bolting on armor made the Humvee an "ungainly beast," increasing weight and putting strain on the chassis, which lead to unreliability. Armored doors that weighed hundreds of pounds were difficult for troops to open and the newly armored turret made Humvees top heavy and increased the danger of rollovers. The U.S. Marine Corps decided to start replacing Humvees in combat with MRAPs in 2007, and the U.S. Army stated that the vehicle was "no longer feasible for combat" in 2012.[9][10]

The HMMWV has become the vehicular backbone of U.S. forces around the world. Over 10,000 HMMWVs were employed by coalition forces during the Iraq War.[citation needed] The Humvee has been described as "the right capability for its era" to provide payload mobility in protected areas, but that conflicts exposing it to full-spectrum threat environments that it was never designed to operate or be survivable in led to adding protection at the cost of mobility and payload.[9]

A U.S. Marine Corps M1123 HMMWV in 2004, equipped with a bolt-on MAK armor kit.

At the Bridgeport, California Mountain Warfare Training Center in March 1997, a test HMMWV drives through the snow, equipped with Mattracks treads.

Modifications
Humvee maintenance with engine exposed by Czech Army in Afghanistan

Humvee interior

In December 2004, Secretary of Defense Donald Rumsfeld came under criticism from U.S. troops and their families for not providing better-equipped HMMWVs.[12] Rumsfeld pointed out that, prior to the war, armor kits were produced only in small numbers per year. As the role of American forces in Iraq changed from fighting the Iraqi Army to suppressing the guerrilla insurgency, more armor kits were being manufactured, though perhaps not as fast as production facilities were capable of bringing them online. Even more advanced kits were also being developed. However, while these kits are much more effective against all types of attacks, they weigh between 1,500 to 2,200 lb (680 to 1,000 kg) and have some of the same drawbacks as the improvised armor.[13] Unlike similar-size civilian cargo and tow trucks, which typically have dual rear wheels to reduce sway, the HMMWV has single rear wheels due to its independent rear suspension coupled with the body design.

A HMMWV equipped with Raytheon surface-to-air missiles, on display at the Paris Air Show in June 2007.

Most up-armored HMMWVs hold up well against lateral attacks, when the blast is distributed in all different directions, but offers little protection from a mine blast below the truck, such as buried improvised explosive devices (IEDs) and land mines. Explosively formed penetrators (EFPs) can also defeat the armor kits, causing casualties.

The armor kits fielded include the Armor Survivability Kit (ASK), the FRAG 5, FRAG 6, as well as upgrade kits to the M1151.[14][15] The ASK was the first fielded, in October 2003, adding about 1,000 pounds (450 kg) to the weight of the vehicle.[16] Armor Holdings fielded an even lighter kit, adding only 750 pounds (340 kg) to the vehicle's weight.[17] The Marine Armor Kit (MAK), fielded in January 2005, offers more protection than the M1114, but also increases weight.[18] The FRAG 5 offered even more protection but was still inadequate to stop EFP attacks.[19] The FRAG 6 kit is designed to do just that, however its increased protection adds over 1,000 lb (450 kg) the vehicle over the FRAG 5 kit, and the width is increased by 2 feet (61 cm). In addition, the doors may require a mechanical assist device to open and close.[20]

Another drawback of the up-armored HMMWVs occurs during an accident or attack, when the heavily armored doors tend to jam shut, trapping the troops inside.[21] As a result, HMMWVs were fitted with hooks on their doors, so that another vehicle can rip the door off, freeing the troops inside.[22] In addition, Vehicle Emergency Escape (VEE) windows, developed by BAE Systems, were fielded for use on the M1114 uparmored HMMWV, with 1,000 kits ordered.[23]

A U.S. military M997 ambulance, emblazoned with the Red Cross.

The soldier manning the exposed crew-served weapon on top of the vehicle is extremely vulnerable. In response, many HMMWVs have been fitted with basic gun shields or turrets, as was the case with M113 APCs after they were first deployed in Vietnam. The U.S. military is currently evaluating a new form of protection, developed by BAE Systems as well as systems designed by the Army, which are already in theater.[24] The new gunner's seat is protected by 1.5 to 2 feet (46 to 61 cm) high steel plates with bullet-proof glass windows. Additionally, some HMMWVs have been fitted with a remotely operated CROWS weapon station, which slaves the machine gun to controls in the back seat so it can be fired without exposing the crew. The Boomerang anti-sniper system was also fielded by some HMMWVs in Iraq to immediately give troops the location of insurgents firing on them.

Another weakness for the HMMWV has proven to be its size, which limited its deployment in Afghanistan because it is too wide for the smallest roads and too large for many forms of air transport compared to jeep or Land Rover-sized vehicles (which are nearly two feet narrower). This size also limits the ability for the vehicle to be manhandled out of situations.

Alternatives
The Army purchased a purpose-built armored car, the M1117 Armored Security Vehicle also known as an armored personnel carrying vehicle (APC), in limited numbers for use by the United States Army Military Police Corps. In 2007, the Marine Corps announced an intention to replace all HMMWVs in Iraq with MRAPs due to high loss rates, and issued contracts for the purchase of several thousand of these vehicles, which include the International MaxxPro, the BAE OMC RG-31, the BAE RG-33 and Caiman, and the Force Protection Cougar,[25][26][27][28][29] which were deployed primarily for mine clearing duties. Heavier models of infantry mobility vehicles (IMV) can also be used for patrol vehicles.[30] The MaxxPro Line has been shown to have the highest rate of vehicle rollover accidents to its very high center of gravity and immense weight. The massive weight of these vehicles combined with their high center of gravity also greatly reduces their utility in off-road situations versus the HMMWV, which was the primary cause for the push for the Oshkosh M-ATV to be developed quickly.[citation needed]

Replacement and future
Main article: Humvee replacement process

The Humvee replacement process being undertaken by the U.S. military focused on interim replacement with MRAPs and long-term replacement with the Joint Light Tactical Vehicle (JLTV). The HMMWV has evolved several times since its introduction and was used in tactical roles for which it was never originally intended. The military pursued several initiatives to replace it, both in the short and long terms. The short term replacement efforts utilized commercial off-the-shelf vehicles as part of the Mine Resistant Ambush Protected (MRAP) program. These vehicles were procured to replace Humvees in combat theaters. The long term replacement for the Humvee is the JLTV which is designed from the ground up. The Future Tactical Truck Systems (FTTS) program was initiated to make an analysis of potential requirements for a Humvee replacement. Various prototype vehicles such as the MillenWorks Light Utility Vehicle, and the ULTRA AP have been constructed as part of these efforts. The JLTV contract was awarded to Oshkosh in August 2015.[31] The U.S. Marine Corps issued a request for proposals (RFP) in 2013 for its Humvee sustainment modification initiative to upgrade 6,700 expanded capacity vehicles (ECVs). The Marines plan to field the JLTV, but do not have enough funding to completely replace all Humvees, so they decided to continue sustaining their fleet. Key areas of improvement include upgrades to the suspension to reduce the amount of force transferred to the chassis, upgrading the engine and transmission for better fuel efficiency, enhancements to the cooling system to prevent overheating, a central tire inflation system to improve off-road mobility and ride quality, and increased underbody survivability. Testing of upgraded Humvees was to occur in 2014, with production and installation occurring from 2015 through 2018. Older A2 series Humvees make up half the current fleet, and 4,000 are to be disposed of through foreign military sales and transfers. By 2017, the Marines' light tactical vehicle fleet is to consist of 3,500 A2 series Humvees, 9,500 ECV Humvees, and 5,000 JLTVs, with 18,000 vehicles in total. Humvees in service with the Marine Corps will be upgraded through 2030.[32] The Marines shelved the Humvee modernization effort in March 2015 due to budget cuts.[33]

Several companies are offering modifications to maintain the remaining U.S. military Humvee fleets. Oshkosh Corporation is offering Humvee upgrades to the Marine Corps in addition to its JLTV offering, which are modular and scalable solutions providing varying levels of capabilities at a range of price points that can be provided individually or as complete solutions. Their approach is centered around the TAK-4 independent suspension system, which delivers greater off-road profile capability, improved ride quality, an increase in maximum speed, greater whole-vehicle durability, and restored payload capacity and ground clearance.[34] Northrop Grumman developed a new chassis and power train for the Humvee that would combine the mobility and payload capabilities of original vehicle variants while maintaining the protection levels of up-armored versions. The cost to upgrade one Humvee with Northrop Grumman's features is $145,000.[35][36] Textron has offered another Humvee upgrade option called the Survivable Combat Tactical Vehicle (SCTV) that not only restores mobility but improves survivability over armored Humvee levels. Although the SCTV costs more at $200,000 per vehicle, the company claims it can restore the Humvee for operational use, combining Humvee-level mobility and transportability with MRAP-level underbody protection as a transitionary solution until the JLTV is introduced in significant numbers.[37][38]

One suggested future role for the Humvee is as an autonomous unmanned ground vehicle (UGV). If converted to a UGV, the vehicle could serve as a mobile scout vehicle with armor features removed to enhance mobility and terrain accessibility, since there would be no occupants needed to protect. Because there will still be tens of thousands of Humvees in the U.S. inventory after the JLTV enters service, it could be a low-cost way to build an unmanned combat vehicle fleet. Autonomy features would allow the Humvees to drive themselves and one soldier to control a "swarm" of several vehicles.[9]

Although the Army plans to buy 49,100 JLTVs and the Marine Corps 5,500, they are not a one-for-one replacement for the Humvee and both services will still be left operating large fleets. For the Marines, 69 JLTVs will replace the 74 Humvees in all active infantry battalions to cover its expeditionary forces. The Marine JLTV order is planned to be completed by 2022, leaving the remainder of the Corps' 13,000-strong Humvee force scattered around support organizations while soft-skinned Humvees will provide support behind the forward deployed Marine Expeditionary Unit. The Army does not plan to replace Humvees in the Army National Guard, and is considering options on how many of its 120,000 vehicles will be replaced, sustained, or modernized. Even if half of the force is replaced by JLTVs, the entire planned order will not be complete until 2040. If upgrades are chosen for the remaining Humvees, the cost would likely have to not exceed $100,000 per vehicle.[39] The Humvee is expected to remain in U.S. military service until at least 2050.[40]

Design features
A U.S. Air Force airman in Southwest Asia stands in the ringmount of a FRAG 6-reinforced HMMWV in April 2010.

The Humvee seats 4 with an available fully enclosed metal cabin with a vertical windshield. The body is constructed from lightweight and rust-resistant aluminum, instead of conventional steel. It has all-wheel drive with an independent suspension and helical gear-reduction hubs similar to portal axles which attach towards the top rather than center of each wheel to allow the drivetrain shafts to be raised for a full 16 in (410 mm) of ground clearance. The body is mounted on a narrow steel frame with boxed rails and five cross members for rigidity. The rails act as sliders to protect the drivetrain which is nestled between and above the rails.[41] Raising the drivetrain into the cabin area and lowering the seats into the frame creates a massive chest-high transmission hump which separates passengers on each side and lowers the overall center of gravity compared to most trucks where the body and passengers are above the frame.[42] The vehicle also has disc brakes on all 4 wheels, and 4-wheel double-wishbone suspension. The brake discs are not mounted at the wheels as on conventional automobiles, but are inboard, attached to the outside of each differential. The front and rear differentials are Torsen type, and the center differential is a regular, lockable type. Torque-biasing differentials allows forward movement as long as at least one wheel has traction. It runs on specialized 37 × 12.5 radial tires with low-profile runflat devices. Some HMMWVs are equipped with an optional central tire inflation system (CTIS), which enables pressure to be lowered for soft ground or raised for hard pavement. While it is optimized for off-road mobility, it can drive at highway speeds of 55 mph (89 km/h) at maximum weight with a top speed of 70 mph (110 km/h).[43]

HMMWVs are well suited for air mobile operations as they are transportable by C-130 or larger combat transports, droppable by parachute, and can be sling-loaded from helicopters, though there are smaller vehicles such as the Growler which were designed to fit into smaller craft such as the V-22. In combat conditions, the HMMWV can be delivered by the Low Altitude Parachute Extraction System which pulls the vehicle out of the open rear ramp just above the ground without the aircraft having to land.

There are at least 17 variants of the HMMWV in service with the U.S. military. HMMWVs serve as cargo/troop carriers, automatic weapons platforms, ambulances (four litter patients or eight ambulatory patients), M220 TOW missile carriers, M119 howitzer prime movers, M1097 Avenger Pedestal Mounted Stinger platforms, MRQ-12 direct air support vehicles, S250 shelter carriers, and other roles. The HMMWV is capable of fording 2.5 ft (76 cm) normally, or 5 ft (1.5 m) with the deep-water fording kits installed.

A BGM-71 TOW missile being fired from a U.S. Army HMMWV.

Optional equipment includes a winch (maximum load capacity 6,000 lb (2,700 kg) and supplemental armor. The M1025/M1026 and M1043/M1044 armament carriers provide mounting and firing capabilities for the M134 Minigun, the Mk 19 grenade launcher, the M2 heavy machine gun, the M240G/B machine gun and M249 LMG.

The M1114 "up-armored" HMMWV, introduced in 2004, also features a similar weapons mount.[44] In addition, some M1114 and M1116 up-armored and M1117 Armored Security Vehicle models feature a Common Remotely Operated Weapon Station (CROWS), which allows the gunner to operate from inside the vehicle, and/or the Boomerang anti-sniper detection system. Recent improvements have also led to the development of the M1151 model, which quickly rendered the previous models obsolete. By replacing the M1114, M1116, and earlier armored HMMWV types with a single model, the U.S. Army hopes to lower maintenance costs.

The latest iteration of the Humvee series can be seen in the M1151A1 and later up-armored A1-versions. It has a stronger suspension and larger 6.5 liter turbo-diesel engine to accommodate the weight of up to 680 kg (1,500 lb) of additional armor. The armor protection can be installed or taken off depending on the operating environment, so the vehicles can move more efficiently without armor when there is no threat of attack. There is some underbody armor that moderately protects against mines and roadside bombs. Other improvements include Vehicle Emergency Escape (VEE) windows that can be quickly removed so troops inside can escape in the event of a rollover, jammed door, or the vehicle catching fire, and a blast chimney that vents the force of a bomb blast upwards and away from the occupants. The M1151A1 has a crew of four, can carry 2,000 lb (910 kg) of payload, and can tow a 4,000 lb (1,800 kg) load. On roads, it has a top speed of 80 km/h (50 mph) and a range of 480 km (300 mi).[45]