Although the 787 is designed to perform a normal gate turn with two 90 Kva GPUs, Boeing recommends that a third 90 Kva GPU be available for non-normal engine start in case of an inoperative auxiliary power unit.
Similar to existing airplanes, the 787 utilizes power from the APU for normal engine starts. The 787 is different in that it uses electrical power for engine starts, rather than pneumatic power used on existing airplanes. If the APU is inoperative, an engine start can be performed using a minimum of two 90 Kva external ground power units. (Information from Boeing Commercial Airplanes, 2/25/2008)
INITIAL TEST FLIGHT
The initial test flight on Dec. 16, 2009 culminated with the MDG5 being selected to power the Dreamliner once it had landed. This was a successful conclusion to the MDG5 program, which had started three years before.