Amphibious Assault Vehicles
The class of vehicles known to travel on land and through water is known as the AAV, or Amphibious Assault Vehicle. The AAV7A1 is the newest Assault Amphibian in a series that started with the Roebling ALLIGATOR. The Alligator was developed over a period of 7 years, starting in 1932. The first "Gators" were a disappointment, in that the water speed was only 2.5 mph. The land speed was 25 mph. Through design changes, and by using larger engines, the water speed of the Alligator was increased to 8.6 mph by 1939. In 1940, Roebling built a new model which was designated the CROCODILE. The Crocodile had a land speed of 25 mph and a water speed of 9.4 mph.
The LVT-1 (Landing Vehicle Tracked) was a direct copy of the Crocodile, except that it was fabricated from sheet steel instead of aluminum. The LVT-1 was in production from 1941 to 1943. Being heavier, the land speed of the LVT-1 was 18 mph and the water speed was 7 mph. The LVT-1 was propelled by two endless chains fitted with cleats, both in the water and on land. The first LVT-1's were used as logistic support vehicles only. They were not armored and carried no armament, however, this soon changed and at the battle of Tarawa, bolted on armor plate was used and the vehicles were equipped with one to four 30 cal. machine guns.
The LVT-1 (Landing Vehicle Tracked) was a direct copy of the Crocodile, except that it was fabricated from sheet steel instead of aluminum. The LVT-1 was in production from 1941 to 1943. Being heavier, the land speed of the LVT-1 was 18 mph and the water speed was 7 mph. The LVT-1 was propelled by two endless chains fitted with cleats, both in the water and on land. The first LVT-1's were used as logistic support vehicles only. They were not armored and carried no armament, however, this soon changed and at the battle of Tarawa, bolted on armor plate was used and the vehicles were equipped with one to four 30 cal. machine guns.
The second generation of LVTs was the LVT-2. This vehicle was developed in 1941 and was in production from 1942 to 1945. The LVT-2 was the basic design for a series of vehicles used during World War II. This family of vehicles included the: LVTA1, LVTA2, LVT4, LVTA4, and LVTA5. A few of the LVTA5s were modified in 1949 and continued in service until the mid 1950s. This generation of LVTs was used up through the Okinawa campaign in 1945.
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The LVT-3 was developed in 1943. Production started in 1944 and continued until the end of World War II. This LVT was used during the battle of Okinawa. The LVT-3 was a bit slower; the land speed was 17 mph on land with a water speed of 7 mph which was slightly slower than the LVT-2 family, measured at 20 mph on land and 7.5 mph in water. The LVT4 and LVT3 were the first LVTs designed with rear loading ramps, also, the LVT2 family and LVT3 family of vehicles used almost identical suspension systems.
In the late 1940s LVT3s were modified into LVT3Cs. The major change was the addition of an armored cover over the cargo compartment and the installation of a small turret. Some minor changes were made to the engine ignition system during this changeover to the LVT3C, but basically the engine, transmission, power train and suspension system were the same as the LVT3. The additional weight, with no increase in engine power, resulted in lower vehicle speed, the land speed dropped to 16 mph and the water speed dropped to 6 mph. The LVT3C was used in combat during the Korean War, and was used during the Inchon landing made in 1950. The LVT3C remained in service until 1956 when it was replaced by the LVTP5.
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The LVTP5 was developed in 1950 and went into production in 1951; however, due to power train and suspension problems, the LVTP5 was not put into service until 1956. The LVTP5 was the "heavy weight" of LVTs, it weighed 40 tons combat loaded. This vehicle achieved speeds of 30 mph on land and 7 mph in the water. Again the use of a tank transmission resulted in power train problems. The LVTP5 utilized an underwater track return, this put the final drive assemblies about 3 feet below the transmission output shafts, as a result drop gear assemblies had to be used to couple the final drives to the transmission. The drop gears and the early final drives were frequent sources of failure.
As with all the LVTs up to this point, the LVTP5 was track propelled on land and in the water. The LVTP5 family of vehicles was used extensively during the Vietnam War. The LVTP5 family of vehicles remained in service until 1972, at that time they were replaced with the LVT7 family of vehicles. The LVT7 family of vehicles was an aluminum-hulled and was the first to use water propulsion jets for movement in the water, achieving a water speed of 8 mph.
The latest family of vehicles is the AAV7A1; this is not a new family, but an improved version of the LVT7 family.
These LVTs were crucial in war because of their logistical support and also defensive capabilities. They could function as roaming stations to lend radio connections with moving troops wherever they were in battle.
The latest family of vehicles is the AAV7A1; this is not a new family, but an improved version of the LVT7 family.
These LVTs were crucial in war because of their logistical support and also defensive capabilities. They could function as roaming stations to lend radio connections with moving troops wherever they were in battle.