ERA15IA206

The unoccupied airplane was parked on the ramp with the parking brake off; ground personnel then attempted to tow the airplane. During the attempted towing, the nose landing gear (NLG) actuator attachment lug fractured, which resulted in the collapse of the NLG. Examination of the NLG actuator attachment lug revealed that the end of the attachment fitting was fractured on both sides of the bearing. The fractured surfaces exhibited features consistent with overstress separation. The reason for the overstress could not be determined.

On May 3, 2015, at 1415 eastern daylight time, a Cessna 525B, N784JS, experienced collapse of the nose landing gear during towing of the airplane at the Teterboro Airport (TEB), Teterboro, New Jersey. There were no occupants on-board at the time. The airplane sustained minor damage. The airplane is registered to JS CJ3 LLC, and operated by Superior Air Charter LLC, dba Jet Suite Air. Visual meteorological conditions prevailed at the time. The airplane was secured on the ramp at the time of the incident.After landing, the airplane was taxied to the ramp where it was secured. The captain later indicated the parking brake was initially set as part of the Shutdown Checklist, then the parking brake was released a few minutes later when the chalks were in place. The first officer reported exiting the airplane and assisted the passenger in deplaning, then performed a safety walk around. The airplane was then locked, and the flightcrew left the airport to eat. A short time later they were informed by phone that the nose landing gear had collapsed. Upon return to the airport, the captain noted the tug was still connected to the airplane via the tow bar, and the nose landing gear was resting on the closed doors and the tow bar. The captain re-entered the airplane and reported the landing gear selector was in the down position and the parking brake was released (both normal). The individual who was attempting to tow the airplane reported that he connected the tug to the airplane, 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 contained in the NTSB public docket. Postincident inspection of the airplane, and towbar by a FAA airworthiness inspector revealed the shear pin of the tow bar was not sheared, and a lug of the nose landing gear actuator was fractured near the airframe attach point. Close visual inspection of the fractured actuator lug revealed evidence of elongation. The FAA inspector also reported that they checked the brake pucks and they were loose consistent with the brakes not being applied. The nose landing gear actuator was retained for further examination by the NTSB Materials Laboratory. According to a statement from a Textron Aviation (formerly Cessna Aircraft Company) technician, when he arrived at the airplane several hours after the event, the cabin door and accessory doors were locked. One of the flightcrew members gave him a key and he unlocked the cabin door and left nose compartments. He did not enter the airplane and relocked the cabin door. The technician also stated that prior to departure he checked the wheels and felt the brake rotors and found they were free to move indicating the brakes were off. A copy of the statement from the technician is contained in the NTSB public docket. The operator reported that the nose landing gear actuator was installed on December 19, 2011, at airplane total time 5,548 hours and 4,113 cycles. Theairplane had accrued 1,935 hours and 1,264 cycles since installation at the time of the incident. According to the factual report by the NTSB Materials Laboratory concerning the nose landing gear actuator, the end attachment fitting was fractured on either side of the bearing. Magnified visual examination of the fitting revealed fracture features and deformation patterns consistent with overstress separations at both locations. The fracture locations were consistent with tensile force along the axis of the actuator, and there was no evidence of pre-existing cracking or corrosion noted. The material was identified as 7075 aluminum alloy, and the hardness and electrical conductivity were consistent with 7075 aluminum in the T73 tempter condition. A copy of the NTSB Materials Laboratory factual report is contained in the NTSB public docket.