What happened
On August 12, 2014, a Rans S-7 Courier, registration 974-GL, was conducting a local sightseeing flight over Réunion Island. During the flight, the pilot encountered significant turbulence while passing over the Cimendef mountains. While descending toward Cambaie, the right rudder pedal suddenly dropped, causing the aircraft to enter asymmetric flight.
The pilot discovered that the right rudder control cable had snapped. Because the broken end of the cable near the rudder was within reach of the passenger, the pilot instructed the passenger to hold and pull the cable to maintain directional control. This arrangement allowed the crew to return to Cambaie and perform a landing without further issues. However, shortly after touchdown, the passenger lost their grip on the cable. The aircraft veered left off the runway at approximately 60 km/h, resulting in the left wing striking a tree and causing heavy damage to the Rans S-7 Courier.
The investigation
The BEA examined the control system of the aircraft, noting that the rudder cables run from the rear pedals, through guide pulleys, to the rudder. The investigation focused on the broken stainless steel cable, which was found to have failed at a pulley. Microscopic analysis revealed that 67% of the examined strands showed evidence of progressive fatigue failure. The pulleys also showed signs of excessive tension and cable misalignment.
Regarding maintenance, the aircraft had completed 6,313 flight hours since its 2006 introduction. The most recent maintenance, performed just two weeks prior, did not specifically include an inspection of the rudder control cables. Notably, the owner reported that this specific cable had failed at the same location three times since 2006. Furthermore, the maintenance manual provided by the French importer did not specify required cable tension or specific monitoring procedures, unlike the manufacturer's recommendations which suggest following FAA Advisory Circular AC 43.13-1B.
Findings
- The runway excursion was caused by the loss of rudder effectiveness following the fatigue failure of the right rudder control cable.
- The passenger's temporary ability to hold the cable allowed for a safe return to the airfield, but the loss of manual tension during landing led to the excursion.
- The maintenance manual provided to the operator lacked critical information regarding cable tension and specific inspection intervals.
- The operator had been aware of the recurring failure of this specific cable but had not implemented new maintenance measures or reported the recurring issue to the manufacturer.