Dennis McGinn, the assistant secretary of the Navy for energy, installations and environments, is briefed on the Medium Tactical Vehicle Replacement Auxiliary Power Unit, a new generator in development, during a tour of Marine Corps Base Quantico on Feb. 6, 2014. The MTVR-APU is attached to the cab of a 7-ton truck and can be used to power radio, navigation and weapon systems like the M777A2 Howitzer. - Dennis McGinn, the assistant secretary of the Navy for energy, installations and environments, is briefed on the Medium Tactical Vehicle Replacement Auxiliary Power Unit, a new generator in development, during a tour of Marine Corps Base Quantico on Feb. 6, 2014. The MTVR-APU is attached to the cab of a 7-ton truck and can be used to power radio, navigation and weapon systems like the M777A2 Howitzer.