As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT NR 4039 - AFTER TAKEOFF LEFT MAIN LANDING GEAR FAILED TO SHOW TO BE UP AND LOCKED. CREW CYCLED THE ONCE, DID NOT SOLVE PROBLEM. CREW ELECTED TO RETURN TO FIELD. AIRCRAFT LANDED WITHOUT FURTHER INCIDENT. PIT-MX INSPECTED AIRCRAFT AND DISCOVERED THE LEFT MAIN LANDING GEAR UPLOCK MICROSWITCH TO BE DEFECTIVE. REPLACED MICROSWITCH IAW MM 32-10-00. GROUND CHECKED GOOD. AIRCRAFT RETURNED TO SERVICE.