Cessna 172 N3KV accident near Lake Worth, Florida

Probable cause

Maintenance personnel’s failure to detect the corroded aileron cable during recent inspections, which resulted in the separation of the aileron control cable and a subsequent loss of airplane control during takeoff.

NTSB analysis

Airport security video recorded the accident takeoff and captured the airplane rolling right until it was in an approximate 90° right bank, then continued a right descending turn until it impacted the ground. A witness reported that the engine sounded like it was at full power from the time the airplane departed until it impacted the ground.

Examination of the wreckage revealed that there was a break in the aileron control cable system in the vicinity of the left upper door post right direct aileron cable pulley. A metallurgical examination of the break in the aileron control cable revealed that the mating fracture surfaces exhibited a woody appearance, shedding material, and pockmarks consistent with a corrosive attack. The angled fractured surfaces exhibited the same layered woody appearance, which indicated that those wires likely fractured in tension due to embrittlement and weakening from corrosive attack. If the cable was shedding material and becoming weaker, this process would have resulted in shedding material wire-by-wire and strand-by-strand over time. The remaining wires would have fractured from tensile overstress when there were no longer enough intact wires to carry the stress. It is likely that the overstress fracture occurred during the takeoff, which was consistent with the right roll as seen in the surveillance video.

According to maintenance records, the airplane was inspected in accordance with the manufacturer’s maintenance manual and with Part 43 appendix D two times during the eight months before the accident. According to both inspection checklists the aileron control cable should have been inspected. The condition and degradation of the cables should have been apparent during those inspections. Therefore, it is likely that maintenance personnel overlooked the corroded aileron control cable during the most recent inspections.

Text from the NTSB. Open the NTSB docket for ERA23FA247 for the full record.