As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) AFTER TAKEOFF, THE LANDING GEAR WAS NOT RETRACTABLE. EMERGENCY CHECKLIST FOR LANDING GEAR MALFUNCTION AND UNEVENTFUL RELANDING PERFORMED. THE FAULT WAS CAUSED BY AN A UNSERVICEABLE NLG CENTERING SENSOR. NOSE WHEEL CENTERING SENSOR REPLACED ACCORDING AMM 32-61-00. THE AIRCRAFT IS POST SB84-32-33.