On 21 August 2006, a Boeing 737-500 suffered a nose landing gear collapse during towing at the Newark Liberty International Airport. A technical crew was repositioning the aircraft in visual meteorological conditions during the occurrence. No persons were injured and minor aircraft damage occurred.
The following is an extract from the official National Transportation Safety Board (USA) (NTSB) Report (NYC06IA207) on the Serious Incident:
"According to the maintenance technician seated in the cockpit, he was "riding the brakes" while the airplane was being towed at walking speed, when he felt a bump, which was followed by the collapse of the nose landing gear.
According to Continental Airlines representatives, the nose landing gear collapsed forward into the wheel well. The nose landing gear remained attached to the airplane by its primary trunnion support and upper drag brace. The lock brace assembly fractured in close proximity to the lock link. The lower drag brace was fractured near the center of its length. The tow bar shear pin was also fractured during the incident.
The nose landing gear lock actuator, upper drag brace, lower drag brace, lock brace, and retract actuator were forwarded to the National Transportation Safety Board's Materials Laboratory, Washington, D.C., for further examination. All fractures were consistent with overstress separation and no evidence of fatigue cracking or any other pre-existing conditions were found. The fracture on the lower drag brace exhibited deformation consistent with the fracture location moving downward relative to the ends. The bending deformation was consistent with the collapse of the gear following buckling of the lower drag brace."
"Examination and testing of the nose landing gear actuator assembly, lock actuator, left hand nose gear steering actuator, depressurization steering valve, and steering metering valve, which was supervised by a Safety Board investigator, did not reveal any pre-incident discrepancies.
The 737-300/-400/-500 airplane maintenance manual, page 213, alerted operators, that at a minimum, applying airplane brakes while towing the airplane could shear the towbar shear pins. Examination of the ground surrounding the airplane after the incident did not reveal any main landing gear tire skid marks."
The NTSB determines the probable cause(s) of this incident as follows:
- "An overload failure of the airplane's nose landing gear while being towed for repositioning."
- "After the incident, Boeing issued Service Letter 737-SL-09-003. The service letter discussed six previous reports of 737 nose landing gear collapse that occurred between 2004 to 2006 during pushback or towing. It also addressed current towbar design, and provided recommendations for operators intended to minimize the likelihood of nose gear damage or collapse during towing and pushback operations."
The NTSB Report is available at SKYbrary bookshelf: NYC06IA207