MECHANIC DESCRIBES THE EVENTS THAT LED TO A R MAIN GEAR UP LANDING AND ACFT DAMAGE ON A PIPER CHIEFTAIN PA31-350 ACFT.

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I WAS INSTRUCTED TO INSTALL A BUSHING ONTO THE MAIN ATTACH FITTING FOR THE R-HAND MAIN LNDG GEAR ACTUATOR. THE BUSHING HAD BEEN CANNED FOR ANOTHER ACTUATOR ON ANOTHER ACFT THAT WAS FOUND TO BE MISSING. WHEN I WENT TO INSTALL THE BUSHING I ALSO HAD TO INSTALL THE BOLT. THIS BOLT AND BUSHING IS THE MAIN ATTACH POINT FOR THE ACTUATOR. THE BOLT GOES THROUGH A SWIVEL ARM FOR THE UP-LOCK HOOK AND THEN A BRACKET THEN THE ACTUATOR THEN ANOTHER BRACKET. I INSTALLED THE BOLT AND SECURED IT; THEN INSPECTED THE REST OF THE ACTUATOR AND MADE SURE EVERYTHING WAS SECURE. THE BOLT AND BUSHING WERE THE ONLY THINGS THAT HAD BEEN REMOVED OR LOOSENED. I BELIEVED THE ACTUATOR WAS SECURE; SO I WENT TO GO GET AN INSPECTOR TO CHK OVER MY WORK; AS REQUIRED BY MY COMPANY. I DID NOT WITNESS THE INSPECTOR INSPECT MY WORK; HOWEVER; HE SAID HE DID. I FINISHED UP THE PAPERWORK AND SIGNED OFF THE ACFT LOGBOOK. MY MISTAKE WAS THAT I DID NOT PERFORM A RETRACTION TEST. I FELT IT WASN'T NECESSARY BECAUSE I DID NOT CHANGE THE RIGGING OF THE ACTUATOR AND THAT THE BOLT WAS THE ONLY PART THAT HAD BEEN REMOVED AND I WAS SURE IT WAS SECURE. THE FOLLOWING DAY THE ACFT HAD TO MAKE AN EMER LNDG WITH THE R MAIN GEAR UP CAUSING EXTENSIVE DAMAGE TO THE ACFT AND PUTTING THE PLT IN GREAT DANGER. IF I HAD DONE A RETRACTION TEST AND WITNESSED THE INSPECTOR INSPECT MY WORK THIS INCIDENT WOULD HAVE BEEN AVOIDED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: WHEN THE THRU BOLT WAS INSTALLED; IT APPEARED THE BOLT HAD PROPERLY GONE THROUGH THE RIGHT MAIN LANDING GEAR ACTUATOR HOUSING ATTACH HOLE. BUT THAT IS NOT WHAT ACTUALLY HAPPENED. THE THRU BOLT HAD ACTUALLY PASSED OVER THE ACTUATOR HOUSING HOLE WITH LITTLE; IF ANY; NOTICEABLE OFFSETTING OF THE ACTUATOR THAT WOULD CATCH ANYONE'S EYE. EVEN THE INSPECTOR NEVER NOTICED THE SUBTLE DISCREPANCY. REPORTER STATED THAT ALTHOUGH THE INSPECTION OF THE BUSHING AND ACTUATOR INSTALLATION IS A REQUIRED RII ITEM; THE GEAR SWING IS NOT REQUIRED AND GENERALLY LEFT TO THE MECHANIC TO DETERMINE IF NECESSARY. AT THE SAME TIME; HIS COMPANY IS EMPHASIZING THE IMPORTANCE OF GETTING THE ACFT SERVICEABLE AND THE ADDITIONAL TIME THE GEAR SWING WOULD TAKE TO PERFORM. AS A RESULT; THE GEAR SWING WAS NOT ACCOMPLISHED AS A PRECAUTION. WHEN THE ACFT DEPARTED; THE GEAR UP SEQUENCE WAS FINE. BUT WHEN THE FLIGHT CREW EXTENDED THE GEAR; THE RIGHT MAIN LANDING GEAR ACTUATOR HOUSING FELL; PREVENTING THE UPLOCK HOOK FROM RELEASING THE R GEAR; FORCING A GEAR UP LANDING.