What happened
On February 18, 2022, a Cessna 172 S, registered F-OOOO, was performing a cross-country flight near Saintes-Terre-de-Haut, Guadeloupe. The flight, operated by Aéro-Club de l'Aviation Civile de la Guadeloupe, was intended to demonstrate the local area to a passenger. During the initial climb following a touch-and-go, the pilot attempted to level the wings after encountering light turbulence. At this moment, the crew heard a snapping noise, and the pilot discovered that the control wheel no longer provided resistance when turned to the right.
While the pilot could still maintain left roll control, the right roll control was non-functional. The pilot successfully managed the aircraft by prioritizing yaw control to maintain direction and returned to Pointe-à-Pire - Le Raizet airport for an emergency landing. During subsequent maintenance inspections of the aircraft, a second failure occurred when the left flap control cable fitting also ruptured.
The investigation
The BEA examined the control systems and the failed components. The investigation focused on the aileron and flap control cables, which were found to have ruptured at their attach fittings. Laboratory analysis of the fittings, made of AISI 303 Se stainless steel, revealed corrosion pitting on the outer surfaces and branching cracks beneath the fracture surfaces.
Chemical analysis identified traces of chlorine and oxygen within the cracks. The investigation also reviewed the maintenance history and the effectiveness of existing safety communications from the FAA and EASA. It was noted that while the maintenance workshop followed scheduled programs, they were not actively monitoring the specific Safety Information Bulletins (SIB/SAIB) related to this phenomenon.
Findings
- The primary cause of the aileron control failure was stress corrosion cracking of the cable attach fitting, likely accelerated by the warm, humid, and salt-laden environment of Guadeloupe.
- The failure of the aileron fitting resulted in a loss of right roll control, creating a high risk of in-flight loss of control.
- The secondary failure of the left flap control cable fitting was also attributed to stress corrosion cracking.
- A lack of visibility regarding FAA and EASA safety bulletins contributed to the maintenance workshop's inability to identify the risk.
- The absence of a mandatory Airworthiness Directive (AD) for the Cessna 172 fleet meant that inspections for this specific metallurgical vulnerability were not strictly required.