What was found
ONCE SELECTING GEAR TO UP POSITION ON TAKEOFF, PROX SYS 1 FAULT STATUS CAME UP FOLLOWED BY A GEAR DISAGREE MASTER WARNING, RAN QRH GEAR WAS SELECTED DOWN AND MESSAGE EXTINGUISHED, RETURNED TO FIELD. SERVICED NLG SHOCK STRUT WITH NITROGEN AND OIL REF AMM 12-12-32. . PERFORMED NLG EXTENSION/RETRACTION PER 32-30-00. MDC FLAGGED B1-007408 (NG CENTER #1 SENSOR OUT-OF RIG). ALSO FOUND EXCESSIVE SAND/DIRT COATING SENSOR AND TARGET. CLEANED AND REGAPED NG CENTER SENSOR REF AMM 32-61-05. ALSO FOUND NLG SHOCK STRUT NEEDED PROPER SERVICE. SERVICED NLG SHOCK STRUT WITH NITROGEN AND OIL REF AMM 12-12-32. . PERFORMED NLG EXTENSION/RETRACTION PER 32-30-00, NO DEFECTS NOTED / MAR 14, 2021. REFER TO CP: 22458485 FOR CORRECTIVE ACTION.