What happened
On October 9, 2012, a Beechcraft 1900D, registration F-GOPE, was performing a scheduled domestic passenger flight from Lyon Saint Exupéry to Rodez Marcillac. During the initial climb, the pilot flying noticed that inputs to the electric pitch trim control had no effect. The crew attempted to use the manual trim controls, but these were also non-functional.
To maintain control, the crew stabilized the aircraft at 5,000 feet and a speed of 140 knots. The crew decided to execute a turnaround, maintaining a speed below 140 knots throughout the descent. The aircraft landed safely on runway 36L with a 35-degree flap configuration. There were no fatalities or injuries among the six passengers and two crew members on board.
The investigation
Upon ground inspection, investigators discovered that the pitch trim cable had snapped. The cable, a seven-strand steel loop, failed at the point where it wraps around the autopilot servo-command pulleys. Analysis revealed that half of the strands had broken due to overload, while the remaining half failed due to fatigue crack propagation, likely caused by the specific stresses applied to the cable during winding around the pulley.
While the aircraft's maintenance records showed it was up to date with all scheduled inspections, the investigation found that standard visual inspections—including the use of a cloth to detect broken strands—were insufficient. A subsequent examination of another aircraft from the same operator, F-GUPE, revealed significant internal damage (up to 20% of strands broken) that was invisible to the naked eye and only detectable via detailed radiographic inspection.
Findings
- The primary cause of the incident was the fatigue failure of the steel strands within the pitch trim cable.
- The damage was undetectable through the standard maintenance procedures currently required for this aircraft type.
- Existing maintenance protocols only require replacement if visible wear or damage is detected, and the manufacturer's 2006 safety communication only recommended visual and mechanical inspections.
Safety action
- The BEA has recommended that the FAA, in coordination with the manufacturer, mandate either a modification to the pitch trim system or the implementation of regular, interval-based replacement of the pitch trim cable to prevent undetectable fatigue failures.