Energy storage substations using flywheels for energy storage have been demonstrated to be practical for application to aircraft, but a practical method for introducing energy to and extracting energy from the flywheel has not been demonstrated for utility applications. A program is under way to design, build, and test a mechanical power package (MPP) for operating the B-1 bomber main landing gear. This program is being sponsored by the Air Force under Contract F33615-75-C-2011. The MPP will include a mechanical infinitely-variable traction transmission for input and extraction of energy, and will also be used to investigate certain methods for reducing energy loss. This paper reports these methods and summarizes the test program.