As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) NLG DID NOT EXTEND UPON GEAR DOWN SELECTION. TRIED EMER EXTENSION PROCEDURES WITH NO HELP. ACFT LANDED WITH THE NLG IN THE UP POSITION. NO INJURIES TO 41 PAX OR 4 CREW MEMBERS. INVESTIGATION REVEALED THAT ONE OF THE NLG DRIVE ARM ASSEMBLY SELF-LOCKING NUT WAS MISSING.