What was found
THE ACFT LANDED WITH AN UNSAFE NOSE GEAR INDICATION. THE SUBSEQUENT INVESTIGATION DETERMINED THAT THE NOSE GEAR LOCK PIN LEVER SEPARATED FROM THE ACFT SOMETIME DURING TRAINING FLIGHT. A MORE DETAILED INSP OF LANDING GEAR COMPONENTS REVEALED THAT THE LOCK LEVER, PN 16537-3 AND LOCK PIN, PN 165171 WAS MISSING, POSSIBLY DUE TO THE ROLL PIN, PN MS1656227 AND COTTER PN, PN MS24665-73 LOOSENING OR BREAKING AWAY, DETACHING THE LOCK PIN LEVER FROM THE DOWN LOCK ACTUATOR RESULTING IN A FAILURE OF THE DOWN LOCK MECHANISM.