LOS ANGELES, CA, USA
N184AW
BOEING 737-277
N141UA
BOEING 747SP
A BOEING 747SP COLLIDED WITH THE TAIL OF A BOEING 737. THE 737 WAS LINED UP ON A PARALLEL TAXIWAY AWAITING DEPARTURE. THE 747 WAS TAXIING FROM A TERMINAL GATE TO MAINTENANCE. THE 747 WAS BEING OPERATED BY TWO MECHANICS. ONE OF THE MECHANICS WAS NOT QUALIFIED TO TAXI THE 747. NO. 4 ENG HUNG START AND WAS NOT RUNNING DURING TAXI. THE NO. 4 ENG HYD SYS WAS SWITCHED OFF. THE NO. 4 HYD SYS IS THE PRIMARY POWER FOR THE ACFT BRAKE SYS. THE 747'S INERTIAL NAV SYS (INS) IS REQUIRED TO OPERATE WHILE TAXIING FOR SPEED REFERENCE. THE INS WAS ALSO SWITCHED OFF. THE 747 SPEED BECAME EXCESSIVE ON PARALLEL TAXIWAY. WHEN MECH ATTEMPTED TO STOP THERE WAS NO BRAKE POWER. 747 R WING COLLIDED WITH TAIL OF 737. THE AIRLINE MAINT SUPERVISOR OF 747'S WAS AWARE OF THE MECH NON-QUAL AND THE NO. 4 ENG NOT OPERATING. DECISION WAS MADE TO LET THE ACFT TAXI CONTRARY TO PROCEDURES.
FAILURE OF THE QUALIFIED MECHANIC TO INSURE THE OPERATION OF THE AIRCRAFT BRAKES PRIOR TO TAXIING AND HIS FAILURE TO UTILIZE THE EMERGENY BRAKE SYSTEM TO PREVENT THE COLLISION. CONTRIBUTING TO THIS ACCIDENT WAS THE DECISION OF AIRLINE MAINTENANCE SUPERVISORS TO ALLOW A NON-QUALIFIED MECHANIC TO PERFORM RIGHT SEAT/FLIGHT ENGINEER PANEL DUTIES. ALSO CONTRIBUTING WAS THE QUALIFIED MECHANICS FAILURE TO USE THE AIRCRAFT'S INERTIAL NAVIGATION SYSTEM FOR CROSS REFERENCE OF TAXI SPEED.
Source: NTSB Aviation Accident Database
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