As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WITH #2 ENGINE RUNNING, PARKING BRAKE SET, WHILE STARING #1 ENGINE AIRCRAFT STARTED TO MOVE FORWARD MAKING CONTACT WITH GSE (TUG) ATTACHED TO STARTING POWER UNIT. AFTER COMPLETING FUNCTION CHECK WITH SYSTEM PRESSURE AT 3000PSI PRESSURE AT THE BRAKE UNIT WOULD NOT GO ABOVE 1750PSI., MIN PRESSURE TO PASS CHECK IS 2000PSI. CHECK WAS CONDUCTED NUMEROUS TIMES WITH SAME RESULTS, RECOMMENDATION TO REPLACE VALVE ASSY., BRAKE STANDBY. MILITARY AIRCRAFT