Cessna 172 N22088 accident near Cintrona, Puerto Rico

Probable cause

Maintenance personnel’s inadequate inspection of the airplane, which resulted in inflight the failure of the right aileron carry through cable due to wear, reduced effectiveness of the airplane’s ailerons, and a subsequent loss of control.

NTSB analysis

The pilot had completed a check out flight earlier in the day, and the accident flight was her first solo flight in the accident airplane. She departed the airport where the airplane was based, flew to another airport and performed a touch-and-go landing, then flew to the airport nearest the accident site where she again performed a touch-and-go landing. Upon departure from that airport, while making a turn likely to return to the airport where the airplane was based, the pilot transmitted a mayday call over the common traffic advisory frequency. In the mayday call the pilot reported a loss of control. The airplane then began a descending right turn until impacting a tree and the ground in a mango orchard.

Postaccident examination of the wreckage revealed that the right aileron carry through cable had fractured, and that 62% of strands on one side of the fracture and 60% of strands on the other side of the fracture failed due to wear. The other strands on the cable failed due to overstress. Based on these findings, it is likely that the wear of this cable progressed to the point where it could no longer support the stresses of flight, resulting in the in-flight failure of the right aileron carry through cable. With this cable failure, the closed loop aileron system would be interrupted and the control inputs from the pilot would only tension a single cable run. This would result in the aileron on the unloaded side tending to float toward its zero hinge-moment (aerodynamically neutral) position, while the aileron on the loaded side would remain responsive to pilot input. The pilot would retain partial roll control; however, control effectiveness would be reduced because only the lift-increasing aileron would be actively driven, while the opposing surface would not provide a corresponding aerodynamic response. Due to a lack of available flight data, this investigation could not determine how much control the pilot would retain, and if the pilot would have retained enough control to make a safe landing.

A review of the airplane’s maintenance logbooks found that the left aileron carry through cable had been replaced about 6 months prior to the accident while the airplane was undergoing an annual inspection. The maintenance log entry documenting the inspection and the cable replacement did not note a reason that the cable was replaced. Given the degree of wear observed on the right aileron cable that was observed after the accident, it is likely that the condition had developed over a prolonged period of time. These wear indications, like fractured cable strands, should have prompted maintenance personnel to replace the cable prior to its failure on the accident flight.

The results of postmortem toxicological testing indicated that the pilot had used the sedating antihistamine medication diphenhydramine, but provided no clear evidence that impairing effects of that medication were impairing the pilot at the time of the accident. The toxicological testing also detected ethanol in blood, but not in vitreous fluid, indicating that the detected ethanol likely was from postmortem sources, and not alcohol consumption.

Text from the NTSB. Open the NTSB docket for ERA25FA082 for the full record.