ACR MLG ACFT NOSE GEAR STUCK IN THE DOWN POS DURING RETRACTION AFTER TKOF AND RETURNED TO LAND.

Narrative

AT THE END OF MY REGULAR SHIFT; I WAS ASKED; AND ACCEPTED; AN 8-HRS OVERTIME ALONG WITH 3 OTHER MECHS; TO FINISH REPACKING A MAIN GEAR STRUT ON AN MLG WHICH WERE DISASSEMBLED DURING MY REGULAR SHIFT. AFTER THE STRUT WAS DISASSEMBLED; A LOWER BEARING WHICH HOUSED ONE OF THE SEALS WAS FOUND TO BE CORRODED AND NEW ONE TO BE SENT IN LATER THAT MORNING. AROUND XA00 AM THE NEW LOWER BEARING ARRIVED. AS WE GATHER OUR TOOLS TO BEGIN THE WORKS; THE MAINT MGR IN CHARGE IMMEDIATELY SET AN ETR (ESTIMATE TIME COMPLETION) FOR XX00. WE PROCEEDED TO REASSEMBLE THE STRUT USING MAINT MANUAL AND IPC AS REFS. SINCE WE HAVE NO MEANS OF LIFTING THE PISTON INTO THE STRUT; WE HAVE TO INSERT THE PISTON BY LOWERING THE ACFT AND THUS THE STRUT OVER THE PISTON. BY THIS TIME OUR ETR HAD PASSED. WE THEN INFORMED THE LEAD MECH THAT WE WOULD BREAK FOR LUNCH. AFTER CONSULTING WITH THE MAINT MGR; OUR LEAD INFORMED US THAT HE IS VERY UPSET THAT WE DIDN'T MEET THE ETR; AND DISPLEASED WITH THE FACT THAT WE'RE BREAKING FOR LUNCH. ANOTHER ETR WAS SET FOR US FOR XY00; THIS TIME THE ACFT WAS ACTUALLY PLACED ON SCHEDULE. THE PROCESS OF LOWERING THE ACFT ONTO THE PISTON; ALTHOUGH DIDN'T GO SMOOTHLY WE SEE NO EVIDENCE TO SUGGEST THAT ANYTHING WAS ABNORMAL. AFTER REASSEMBLING THE STRUT WE THEN SVCED AND INFLATED THE STRUT; A THOROUGH LEAK CHK WAS PERFORMED. AFTER SATISFIED WITH THE WORKS; WE THEN PLACED ACFT IN SVC AT APPROX XZ00. AT AROUND ZZ30 SAME ACFT TOOK OFF FROM THE FIELD. SHORTLY AFTER TKOF FLC RPTED AN UNSAFE GEAR UP INDICATION ON THE SAME LNDG GEAR; AND RETURNED ACFT TO THE FIELD. INVESTIGATION REVEALED THAT THE UPPER BEARING ASSEMBLY WHICH LIMITS THE EXTENSION OF THE PISTON WAS CRACKED; AND ALLOWED THE STRUT TO OVEREXTEND PREVENTING NORMAL RETRACTION. I SUSPECT THAT THE UPPER BEARING ASSEMBLY WAS DAMAGED AT SOME POINT WHEN THE ACFT WAS BEING LOWERED ONTO THE PISTON. SUPPLEMENTAL INFO FROM ACN 227290: AFTER INSTALLING THE NEW UPPER STRUT BY A METHOD WE WERE VERY UNCOMFORTABLE WITH WHICH INVOLVED LOWERING THE ACFT ONTO THE LOWER STRUT BECAUSE THE STATION ONLY HAS 1 JACK TO DO THE JOB PROPERLY; THAT JACK HAS BEEN OTS FOR APPROX 1 YR SITTING IN OUR GND SUPPORT SHOP.