Narrative:

This is in reference to #2 power brake cable snapping during a maintenance repos taxi from terminal to maintenance hangar. Upon further investigation, maintenance found the cable for #2 power brake was improperly routed through a fairlead, instead of being between fairlead and pulley assembly, cable was found over the fairlead. During the heavy check (40K) maintenance performed approximately 2 weeks earlier, I was tasked with delegate inspector for the removal and replacement of #2 power brake control valve while in the 40K process a write-up was generated for brakes unequal. Upon troubleshooting, found only 2000 psi being applied to right/south brake system. The brake control valve was changed. Upon removal of valve, found valve pivot arm mount bolt overtorqued, not allowing valve to open fully. Once valve was installed, I inspected the installation of power control valve and cable. During this process, all cable parameters (tensions) were within limits, all travel checks were within limits of maintenance manual. Suspecting no other problems the task was complete.

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Original NASA ASRS Text

Title: A DEHAVILLAND DASH 8 ON TAXI TO HANGAR FOR MAINT HAD #2 PWR BRAKE CABLE FAIL DUE TO INCORRECT ROUTING OF CABLE THROUGH THE BRAKE PULLEY BOX.

Narrative: THIS IS IN REF TO #2 PWR BRAKE CABLE SNAPPING DURING A MAINT REPOS TAXI FROM TERMINAL TO MAINT HANGAR. UPON FURTHER INVESTIGATION, MAINT FOUND THE CABLE FOR #2 PWR BRAKE WAS IMPROPERLY ROUTED THROUGH A FAIRLEAD, INSTEAD OF BEING BTWN FAIRLEAD AND PULLEY ASSEMBLY, CABLE WAS FOUND OVER THE FAIRLEAD. DURING THE HVY CHK (40K) MAINT PERFORMED APPROX 2 WKS EARLIER, I WAS TASKED WITH DELEGATE INSPECTOR FOR THE REMOVAL AND REPLACEMENT OF #2 PWR BRAKE CTL VALVE WHILE IN THE 40K PROCESS A WRITE-UP WAS GENERATED FOR BRAKES UNEQUAL. UPON TROUBLESHOOTING, FOUND ONLY 2000 PSI BEING APPLIED TO R/S BRAKE SYS. THE BRAKE CTL VALVE WAS CHANGED. UPON REMOVAL OF VALVE, FOUND VALVE PIVOT ARM MOUNT BOLT OVERTORQUED, NOT ALLOWING VALVE TO OPEN FULLY. ONCE VALVE WAS INSTALLED, I INSPECTED THE INSTALLATION OF PWR CTL VALVE AND CABLE. DURING THIS PROCESS, ALL CABLE PARAMETERS (TENSIONS) WERE WITHIN LIMITS, ALL TRAVEL CHKS WERE WITHIN LIMITS OF MAINT MANUAL. SUSPECTING NO OTHER PROBS THE TASK WAS COMPLETE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.