JR Potts, AUS 173d AB (Updated: 3/26/2015):
The ATC boats converted from LCM-6 landing craft developed in the 1950s for ship-to-ship and ship-to-shore use. The converted LCM designs added 0.25 inch armor plating in many areas to protect the superstructure from critical damage caused by rockets. The upgraded armored ATC made up about half of the river craft deployed by the United States during the Vietnam War, in effect making the ATC the "workhorse" of the river war. Some ATCs had helicopter decks added and became ATC(H). These installations allowed helicopters to land on the boats themselves for swift evacuation of wounded soldiers. The Mobile Riverine Force (MRF) started with three basic boat types: (1) the ATC boat ("Tango Boat") - this served as the most useful boat; (2) the "Monitor", a floating artillery platform of the MRF and, (3) the Command and Communications Boat (CCB), the so-called "Charlie Boat". Each squadron of boats had a Tango boat converted into a boat for refueling to be used by all of the above.
The ATCs fuel capacity (using fuel oil or gasoline) was 1,200 gallons with space for 300 gallons of lube oil with a mixing tank holding 500 gallons. The boat was equipped with a portable tank and transfer pump that required hoses for the fuel exchange. The ATC full load displacement was 155,000 lbs with a cargo weight of 130,000 lbs. A sling was installed for hoisting fuel containers onboard. She maintained a semi-flat bottom with 2 x 6-cylinder diesel engines each having 225 horsepower at 2,100 rpm for emergency use and 165 horsepower at 1,800 rpm for continued use. ATCs fielded 2 x 24-inch D by 17-inch P by a 2-inch bore with a right-hand rotation propellers. The cargo well was 9'6" x 22'6" with a clear overhead and 9'6" x 31' 6" with a clear dock.