AN SA319 HELI WAS INADVERTENTLY FLOWN PAST THE 50 HR LIMIT FOR A TAIL ROTOR PITCH CHANGE LINK BEARING INSPECTION. REQUIRED AIRWORTHINESS DIRECTIVE INSPECTION.

Narrative

PLT OVERFLEW AN AIRWORTHINESS DIRECTIVE (98-24-35). AIRWORTHINESS DIRECTIVE IS RELATED TO TAIL ROTOR PITCH CHANGE LINK BEARING WEAR; AND IS A RECURRING 50 HRS TIME-IN-SVC REQUIREMENT. THE PLT CHKS THESE ITEMS DURING ALL PREFLT AND POSTFLT INSPECTIONS FOR 'NO MOVEMENT ALLOWED (AXIALLY AND RADIALLY)'. THIS GUIDELINE IS RECOMMENDED BY THE MANUFACTURER; AND TAUGHT AT THE FACTORY SAFETY COURSE. THE AIRWORTHINESS DIRECTIVE SPECIFIES THE USE OF DIAL INDICATOR TO MEASURE THE ACTUAL AMOUNT OF PLAY IN THE BEARING. SCHEDULING AND ANTICIPATING MAINT IS CHALLENGING. IN GENERAL; MAINT OPS ARE SCHEDULED ON WKENDS. MAINT IS CARRIED OUT AT A FACILITY LOCATED IN ZZZ1 (APPROX .5 HR FLT OR 1.5 HR DRIVE AWAY). THIS AREA IS ROUTINELY AFFECTED BY WIDESPREAD DENSE 'TULE FOG;' WHICH BLANKETS THE AREA AND FREQUENTLY DOES NOT READILY BURN OFF. DURING THE WK AND WKEND PRIOR; THE ARPT WAS COMPLETELY FOGGED IN TO BELOW EVEN MVFR CONDITIONS. (CONDITIONS OF 1/4 MI VISIBILITY AND INDEFINITE CEILING 100 FT PREVAILED FOR MOST OF THE WK AND WKEND.) MAINT WAS SCHEDULED BASED UPON THE ANTICIPATED HRS USAGE FOR THE ACFT; HOWEVER; SEVERAL EVENTS SAW THE ACFT FLYING MORE FREQUENTLY AND AFFECTED THE PLANNED SCHEDULE. THE PLT WAS UNAWARE OF HOW QUICKLY THE INSPECTION DUE TIME HAD ARRIVED. THE PLT CONTRACTED WITH ANOTHER MECH FAMILIAR WITH THE MAKE/MODEL OF HELI AND EXPERIENCED WITH THE AIRWORTHINESS DIRECTIVE TO CONDUCT THE INSPECTION. NO DEFICIENCIES WERE NOTED AND THE ACFT WAS RETURNED TO SVC. IN THE MECH'S OPINION; THE BEARINGS ARE STILL VERY NEW AND SHOW NOWHERE NEAR THE MAX PLAY SPECIFIED IN THE AIRWORTHINESS DIRECTIVE. HE FELT THAT; WHILE PROCEDURALLY INCORRECT; THE OVERFLT OF THE AIRWORTHINESS DIRECTIVE DID NOT POSE A SAFETY RISK. THIS WAS LARGELY DUE TO THE LOW TOTAL TIME ON THE ACFT.