Amphibious Assault Vehicle

Overview

An amphibious assault vehicle carries an infantry section across open water from an amphibious ship to a defended beach, drives up out of the surf, and keeps fighting inland as a tracked armored personnel carrier. It is one of the few vehicles asked to be a competent boat and a competent armored vehicle at the same time, and almost every design choice trades between those two jobs. The reference pattern is the long-serving USMC AAV7 and its replacement the ACV: a boxy, buoyant hull seating about 21 embarked marines plus a crew of three, swimming at roughly 13 km/h and then moving at up to about 70 km/h on roads.

The vehicle exists to solve the moment when a landing force is most exposed, the run-in from the horizon to the waterline. During that run the Marine Propulsion and the watertight integrity of the Buoyant Hull keep the troops alive and moving, and the Navigation Unit holds the column on its assigned beach lane when no landmarks are in sight.

Hull and buoyancy

The Buoyant Hull is a welded aluminum-alloy box with a boat-formed bow, built from armor plate such as 5083 and 7039 because aluminum gives useful protection at a weight light enough to float. The Hull Structure displaces enough water to support a laden vehicle of roughly 26 to 30 tonnes while leaving usable freeboard, and the Buoyancy Cell foam blocks in the hull voids preserve reserve buoyancy if a compartment is holed. Every penetration is closed by the Hull Seal Set set, and crew enter through dogged Watertight Hatch units that seal against surf.

Protection is layered to keep the swim weight down. The base hull stops splinters and small arms, and a removable Appliqué Armor Kit kit of ceramic Ceramic Armor Panel tiles bolts on to defeat heavier rounds when the buoyancy budget allows. Underneath, a V-shaped Belly Plate deflects mine and IED blast away from the troop floor.

Swimming to shore

Afloat, thrust comes from two stern Waterjet Unit units rather than the older method of using the tracks as paddles, because jets give more speed and far better control. Each jet draws water through a hull-bottom inlet protected by an Intake Grille, accelerates it with the Jet Impeller, and expels it through the Jet Pump Housing nozzle. Steering and reversing are done by the Steering Deflector buckets, aimed by the Waterjet Steering Control from the driver tiller, which is why the vehicle can hold a heading in a cross-current.

Before entering the water the driver raises the Bow Trim Vane at the bow. That plate holds the nose up, splits the bow wave, and stops water washing over the front deck, the single change that lets a heavy tracked vehicle swim at all rather than plough under. Water that does get aboard through seals, the ramp, and breaking surf is cleared by three electric Bilge Pump units, each started automatically by its Bilge Float Switch. The engine breathes through the raised Air Intake Mast mast so it keeps running with the lower hull submerged. The gap between water speed and land speed is large: about 13 km/h afloat against roughly 70 km/h on a road, which is why the swim is the slow, dangerous part of any landing.

Powerpack and running gear

A single marinized Diesel Engine of roughly 300 to 400 kW does both jobs. The Cross-Drive Transmission is a cross-drive unit that delivers regenerative steering to the tracks on land, and the Marine Power Take-Off clutch switches engine power between the final drives and the waterjet shafts during the surf transition, the few seconds when the vehicle is neither fully swimming nor fully driving. Cooling air for the Cooling Pack is ducted through the snorkel path so the engine does not overheat while floating.

On land the Running Gear runs on torsion-bar suspension, each Road Wheel sprung by a Torsion Bar with Rotary Damper units at the end stations. The Track Assembly grousers also bite into wet sand as the vehicle climbs out of the surf onto the beach, the transition where many amphibians bog down.

Troops and weapon

The Troop Compartment seats about 21 marines on folding Troop Seat with restraint harnesses. They debark through a powered Stern Ramp at the stern, sealed afloat by the Ramp Seal and driven by the Ramp Actuator cylinders, with a small Personnel Door for individual exit. Overhead protection while embarked comes from the sealed hull and the NBC Protection System.

Fire support is a roof-mounted Remote Weapon Station that the gunner operates from under armor, carrying either a .50 caliber heavy machine gun or a 40 mm automatic grenade launcher on the Weapon Cradle. The stabilized Sight Package with its Thermal Imager lets the crew engage through smoke and spray, and the Weapon Control Unit applies ballistic offsets and inhibits fire over friendly arcs.

Crew, electronics, and survivability

The driver and commander work from the Crew Stations with Vision Periscope vision for closed-hatch operation. The Electrical and Comms group runs the radios and the Crew Intercom that keeps crew and troops linked over engine and surf noise. Beyond armor, survivability rests on the Fire Suppression System system, which floods the engine bay within milliseconds of a Flame Detector trigger, and the Emergency Dewatering Pump, a high-capacity dewatering pump for when flooding outpaces the bilge pumps in heavy surf. Variants split between troop carriers, command vehicles with extra radios in place of seats, and recovery versions, but all share the same buoyant hull, waterjet drive, and powerpack.