FLC OF AN MLG ACR ACFT RETURNED TO LAND AFTER THE LNDG GEAR DID NOT RETRACT COMPLETELY DURING THE FIRST FLT AFTER A LNDG GEAR MAINT REPAIR.

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WORKING IN IND IN THE BAL CHK HANGAR ON MLG ACFT; I HAD ROUTINE WORK CARDS REQUIRING SVCING THE MAIN LNDG GEAR UPSTOP DAMPERS. I FOLLOWED THE JOB CARD STEP BY STEP TO THE POINT OF GETTING THE UPSTOP DAMPERS TO THE PROPER DIMENSION REQUIRED FOR INSTALLATION. AFTER INSTALLATION OF BOTH DAMPERS; THE PAPERWORK HAS NO PROVISION OF AN OPERATIONAL CHK OF THE UPSTOP DAMPERS. THE ONLY THING A MECH OR AN INSPECTOR CAN DO IS COMPRESS THE DAMPER BY HAND; AS NOTED ON THE INITIAL INSPECTION ON THE JOB CARD; WHICH HAS NO SPECIFICS ON HOW MUCH RESISTANCE SHOULD OR SHOULDN'T BE ON THE DUMPER PISTON. I HAVE HAD THIS JOB CARD BEFORE AND HAVE HAD NO PROBS WITH THE SVCING OF THE DAMPERS. EVIDENTLY THE ACFT DEPARTED THE FIELD AND HAD A L GEAR UNSAFE WARNING WHEN ATTEMPTING TO RETRACT THE GEAR AND HAD TO RETURN TO THE FIELD. I THINK THAT THE SVCING PAPERWORK SHOULD INCLUDE A PROVISION TO PERFORM AN OPERATIONAL CHK OF THE UPSTOP DAMPERS BY DOING A GEAR EXTENSION AND RETRACTION. BY DOING THE JOB AS IT'S WRITTEN NOW; ONLY LEAVES DOUBT IN YOUR MIND THAT THE DAMPER WILL PERFORM AS IT SHOULD. TO CORRECT THE PROB LINE MAINT RESVCED THE L MAIN UPSTOP DAMPER AND PERFORMED AN OPERATIONAL CHK BY EXTENDING AND RETRACTING THE GEAR LEAVING NO UNKNOWNS ABOUT THE OP OF THE UPSTOP DAMPER.