MIL-STD-1591, MILITARY STANDARD: ON-AIRCRAFT, FAULT DIAGNOSIS, SUB-SYSTEMS, ANALYSIS/SYNTHESIS OF (03 JAN 1977) [NO S/S DOCUMENT]., This standard establishes uniform criteria for conducting trade studies to determine the optimal design for an on-aircraft fault diagnosis/isolation system, hereafter referred to as the On-Board Built-In Test System (OBBIT).