What was found
AFTER TAKE OFF, NLG WOULD NOT RETRACT. NLG GREEN DOWN AND LOCKED LIGHT NEVER EXTINGUISHED. RT AND LT MLG RETRACTED NORMALLY. RED UNSAFE LIGHT ILLUMINATED. PLACED LANDING GEAR HANDLE BACK TO DOWN IAW CHECKLIST AND ALL THREE GREEN DOWN AND LOCKED LIGHTS ILLUMINATED AND RED UNSAFE LIGHT EXTINGUISHED. FOUND "A" SYS HYD RESERVOIR OVERSERVICED AND AIR IN THE SYSTEM. CYCLED GEAR AND RESERVICED HYD SYSTEMS IAW THE MM 12-10-15. OPS & LEAK CHECKED GOOD.