What happened
During the final approach to the runway, the captain observed an unsafe nose landing gear indication on the cockpit's multi function display unit (MFDU). Following standard procedures, the captain abandoned the approach and attempted to recycle the gear, but the indication persisted. The aircraft subsequently landed on runway 13R, rolled out, and came to a stop on the runway; no evacuation was initiated.
A maintenance crew met the aircraft on the runway and installed locking pins in the landing gear. A series of simultaneous communications occurred between the flight crew, the maintenance crew, a maintenance supervisor, and a maintenance crew chief. During these discussions, the flight crew asked if it was necessary to strap the gear. After searching the maintenance manuals, the supervisor informed the crew that strapping the gear was not required prior to towing.
However, a maintenance crew chief advised personnel that strapping was necessary, but no strap was available at the airport. Despite a placard located on the nose landing gear door, the maintenance crew attempted to tow the aircraft without the gear being strapped. During the towing operation, the nose landing gear collapsed, causing the nose of the aircraft to come to rest on the towbar. The passengers were deplaned and moved to the terminal via bus.
The investigation
An examination of the nose landing gear was conducted, but investigators could not determine why the down-lock plunger engaged while the nose landing gear was in the extended position.