Incident Overview
On May 3, 2015, at 1415 eastern daylight time, a Cessna 525B, registration N784JS, experienced a collapse of the nose landing gear during towing at Teterboro Airport (TEB), Teterboro, New Jersey. The airplane was unoccupied at the time and sustained minor damage. Visual meteorological conditions prevailed.
Sequence of Events
The airplane had landed and was taxied to the ramp, where it was secured. The captain initially set the parking brake as part of the Shutdown Checklist, then released it a few minutes later when wheel chocks were in place. The first officer exited, assisted the passenger in deplaning, performed a safety walk-around, and then locked the airplane. Both flightcrew members left the airport to eat. They were later informed by phone that the nose landing gear had collapsed. Upon returning, the captain observed the tug still connected via the tow bar, with the nose landing gear resting on the closed doors and the tow bar. The captain re-entered the airplane and found the landing gear selector in the down position and the parking brake released, both considered normal.
Tug Operator Account
The individual attempting to tow the airplane reported that he connected the tug and "lightly gave the tug gas to move the tug. As I gave the tug some gas, the nose gear on Citation N784JS collapsed." A copy of his statement is included in the NTSB public docket.
Postincident Inspection
An FAA airworthiness inspector examined the airplane and tow bar, noting that the shear pin of the tow bar was not sheared. A lug of the nose landing gear actuator was found fractured near the airframe attach point. Visual inspection revealed evidence of elongation at the fractured actuator lug. The inspector also reported that the brake pucks were loose, consistent with the brakes not being applied. The nose landing gear actuator was retained for further examination.
Technician Observations
A Textron Aviation technician arrived several hours after the event and found the cabin and accessory doors locked. After being provided a key by a flightcrew member, he unlocked the cabin door and left nose compartments but did not enter the airplane, then relocked the cabin door. He also checked the wheels and brake rotors, finding them free to move, indicating the brakes were off.
Actuator History
The operator reported that the nose landing gear actuator was installed on December 19, 2011, at an airplane total time of 5,548 hours and 4,113 cycles. At the time of the incident, the airplane had accumulated 1,935 hours and 1,264 cycles since installation.
Materials Laboratory Findings
The NTSB Materials Laboratory examined the nose landing gear actuator. The end attachment fitting was fractured on either side of the bearing. Magnified visual examination revealed fracture features and deformation patterns consistent with overstress separations at both locations. The fractures were consistent with tensile force along the actuator axis. No evidence of pre-existing cracking or corrosion was noted. The material was identified as 7075 aluminum alloy in the T73 temper condition, with hardness and electrical conductivity consistent with that specification.
Conclusion
The incident involved the collapse of the nose landing gear during towing, with the actuator lug fracturing due to overstress. No probable cause was determined in the source material.