The U.S. Marine Corps is giving 37 percent of its 1,058 AA7A1 amphibious armored vehicles a SU (survivability upgrade). All AA7s will get some refurbishment to keep nearly all the existing AA7s in service until the mid-2020s. The 1970s era AAV7s must prolong their service life until new ACV (Amphibious Combat Vehicle) can replace them in the mid-2020s.
The marines never expected the AAV7s to last this long but several attempts to develop a replacement came up short. Thus the need to extend the life of their AAV7s. The one being refurbished entered service in the early 1970s and were never intended to be in use for this long. Worse, some two thirds of the AAV7s saw service in Iraq, where they got as much use in two months as they normally did in two years of peacetime operations.
The AAV7s getting the SU treatment are another side effect of the Iraq service, where the marines found the AAV7s very vulnerable to roadside bombs and anti-vehicle mines. The SU adds special armor to the sides and bottom of the AAV7 to provide the protection similar to the thousands of MRAP (Mine Resistant Armor Protected) armored trucks soldiers and marines used in Iraq, Afghanistan and elsewhere. In addition the SU upgrade adds a new engine that is 28 percent more powerful as well as MRAP type protection on the floor of the vehicle to minimize the impact of mines or bombs on passengers and crew. This is another feature first demonstrated in MRAPS. SU cost $1.65 million per vehicle.
The 29 ton AAV7s has a crew of four (driver, commander, gunner and rear crewman) and carries 25 combat ready marines as passengers. The vehicle is armed with a 40mm automatic grenade launcher and a 12.7mm machine-gun. Top land speed is 72 kilometers an hour on roads, 32 off road and 13 in water. That is about 20 percent faster for AAV7SUs.
The main reason the AAV7s are still in use is a failed, decade long, effort to get the high-tech replacement (the EFV or Expeditionary Fighting Vehicle) to work. Back in 2011 the marines gave up on high-speed (sea skimming) amphibious assault vehicles like EFV. The marines then decided that a simpler ACV design would do to replace the AAV7s. DARPA (the Defense Advanced Research Projects Agency) was called in to help design the new vehicle. This may sound either very innovative or very desperate, and in reality it was both. In part because the marines had spent three billion dollars on the EFV and that disaster made it clear that some original thinking was required for the ACV. In the end the $12 million ACV was the EFV without most of the expensive stuff that didn't work. In effect, the ACV was be a 21st century version of the AAV7, optimized to pass all its development tests and get into service as quickly as possible. DARPA quickly did its job but the resulting ACV was still more expensive ($12 million) than the shrinking marine budget could handle all at once.
In retrospect, the marines could have just built the EFV without the high-speed capability but that was eventually considered technically and politically impractical. The problem remains that the technology simply does not yet exist yet to make the high-speed capability workable. The budget situation is grim, leaving the usually unstoppable Marine Corps running into an immovable object and improvising as best they can. The marines have asked the navy to develop a high speed amphibious craft (or “connector”) to get ACVs to shore quickly but the navy budget is also shrinking and probably unable to handle the cost of developing and building the connector. Some marine analysts point out that the need for moving amphibious vehicles 200 kilometers from ship to shore is probably unrealistic for any likely future marine operations. But that is another matter.