The B-1B secondary power subsystem is a derivative of the subsystem used in the B-1A aircraft. In the B-1B, the earlier design has been modified to add an onboard alternate cross-bleed start capability for the main propulsion engines. The normal start system also has been changed from a hydromechanical link between each APU and the two related engines to a combination of a hydromechanical link and a pneumatic link.
During this redesign, the APU starting and the APU/ADG coupling limitations revealed during the original B-1A RDT&E program also were addressed.
Development and preliminary qualification tests on the redesigned subystem throughout the required operating environment indicate that the revised configuration meets all design objectives.