What was found
PHX - AFTER TAKEOFF, NOSE GEAR WOULD NOT RETRACT. FOUND NOSE STRUT FLAT. REPLACED SCHRADER VALVE O-RING, MFG P/N MS28778-7, AND SERVICED STRUT WITH OIL AND AIR. EXTENDED NOSE STRUT TO FULL EXTENSION AND BACK DOWN WITH NO FINDING. NOSE LANDING GEAR CHECKS NORMAL.