What was found
(CAN) AC NOSE WHEEL STEERING INDICATOR SHOWED A NON-CENTRED CONDITION OF NOSE WHEEL IMMEDIATELY AFTER TAKE-OFF. AFTER SEVERAL LOW FLYOVERS TO VISUALLY CHECK CONDITION, EMERGENCY WAS DECLARED, AC WAS LANDED. POST LANDING, NOSE OLEO WAS DISCOVERED TO HAVE BECOME FULLY DEFLATED (ALTHOUGH THERE WAS NO OIL LEAKAGE), WHICH PREVENTED OLEO FROM FULLY EXTENDING, THUS NOT ALLOWING INTERNAL CENTERING DEVICE TO CENTER THE WHEEL. SOURCE OF LEAK WAS DETERMINED TO BE A LEAKING HIGH PRESSURE INFLATION VALVE (SCHRADER). WHILE VALVE IS CORRECT ONE, CALLED FOR IN PARTS MANUAL, STANDARD PRACTICE TO INSTALL MECHANICALLY CLOSED VALVES. THIS WAS DONE, OPERATION OF OLEO CENTRING DEVICE WAS CONFIRMED. (TC NR 20060209002)