AN MD-80 ACFT BEING WORKED BY A CONTRACT MAINT PROVIDER MECHANICS FOR A NLG DOWN AND LOCKED INDICATOR PIN THAT WAS PROTRUDING IN FLIGHT; FAILED TO DOCUMENT THEY BROKE THE SAFETIES AND ADJUSTED THE NLG SYSTEM.

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ACFT WAS BROKE HERE. THE NOSE LNDG GEAR DOWN AND LOCKED INDICATOR PIN THAT WAS PROTRUDING INFLT; WHEN GEAR WAS UP AND LOCKED. THE CONTRACT MAINT TECH; WORKED ON IT UNTIL EARLY THE NEXT MORNING. WHEN WE ARRIVED; WE WERE TOLD BY MAINT CTL TO PROCEED WITH THE ADJUSTMENT AS SPELLED OUT IN THE MAINT MANUAL. CONTRACT MAINT HAD SHORT SIGNED THAT THE GEAR PINS WERE INSTALLED. WE JACKED THE ACFT AND BEFORE WE GOT MUCH FURTHER MAINT CTL HAD A SHIFT CHANGE AND WE WERE ASKED TO OPEN IT UP AND LOOK FOR ANYTHING CATCHING; RUBBING; ETC. WE OPENED IT ALL UP AND INSPECTED/MANIPULATED/JIGGLED ALL WE COULD GET OUR HANDS ON. WE SWUNG THE GEAR MULTIPLE TIMES AND COULD NOT FIND A PROB. THE PIN RETRACTED WITH THE GEAR AND POPPED UP WHEN THE GEAR WAS DOWN AND LOCKED; EVERY TIME. WE CLOSED IT UP AND CALLED IT GOOD. HERE IS OUR PROB. I SPOKE WITH THE CONTRACT MAINT TECH AND WAS TOLD THEY HAD BROKE THE SAFETIES AND ADJUSTED THE SYS. THEY SWUNG THE GEAR AND TESTED THE SYS. NO WHERE WAS THAT DOCUMENTED; NOR WERE WE INFORMED OF THIS FACT. WE DID NOT CHK THE SAFETIES; OR THE GAPS/RIGGING OF THE SYS. WE WERE LOOKING FOR SOMETHING HUNG UP OR BINDING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THAT NONE OF THE WORK PERFORMED BY THE CONTRACT PROVIDER MECHANICS WAS EVER DOCUMENTED. THIS MAINT ON THE NOSE LANDING GEAR (NLG) SYSTEM INCLUDED BREAKING THE SAFETIES; ADJUSTING THE SYSTEM AND SWINGING THE NLG; ALL WITHOUT ANY DOCUMENTATION. REPORTER ALSO STATED; WHEN HE AND ANOTHER MECHANIC; WHO ARE THE CARRIER'S EMPLOYEES; TOOK OVER THE WORK FROM THE CONTRACT PROVIDER; THEY WERE NEVER INFORMED OF THE MAINT WORK ALREADY PERFORMED -- JUST THAT THE GEAR PINS WERE INSTALLED. FOLLOWING INSTRUCTIONS FROM THEIR MAINT CONTROL THEY DID A VISUAL OF ALL COMPONENTS; MECHANISMS; CABLES; BRACES; NLG LINKS; INCLUDING SWINGING THE NLG. THE NLG DOWN AND LOCKED INDICATOR PIN EXTENDED; AS IT SHOULD; DURING THE DOWN CYCLE AND RETRACTED DURING THE UP AND LOCKED CYCLE. REPORTER ADDS; HE FOUND OUT LATER; AFTER THE ACFT HAD DEPARTED; OF THE UNDOCUMENTED MAINT WORK AND HIS CONCERNS FOR THE NLG SYSTEM MECHANICAL SAFETIES THAT WERE NEVER VERIFIED. HE NOTIFIED HIS COMPANY AND THE ACFT WAS GROUNDED AT A DOWNLINE STATION TO HAVE A FULL NOSE GEAR SAFETY INSPECTION. THE ACFT WAS LATER FLOWN TO THEIR MAINT BASE FOR ANOTHER INSPECTION. REPORTER CONCLUDES BY SAYING THAT OTHER FELLOW MECHANICS HAD PREVIOUSLY RAISED CONCERNS ABOUT THIS PARTICULAR MAINT PROVIDER'S PRACTICES; BUT; HE NEVER GAVE IT MUCH THOUGHT ABOUT IT UNTIL THIS HAPPENED TO HIM.