What was found
(CAN) AFTER TAKEOFF GEAR LEVER SELECTED UP, RED NOSE GEAR UNSAFE LIGHT REMAINED ON. NOSE GEAR APPEARED TO RETRACT PARTIALLY. QRH CARRIED OUT, SAME CONDITION REMAINED. GEAR SELECTED DOWN AND AIRCRAFT SAFELY LANDED. MAINTENANCE TROUBLESHOOTING FOUND NOSE OLEO FLAT WITH PISTON CHROME DAMAGE. NOSE LANDING GEAR OLEO PISTON ASSEMBLY CHANGED. GEAR SERVICED AND OPERATIONALLY CHECKED SERVICEABLE.