What happened
On December 1, 1985, an Air France Boeing 747-228B Combi, registration F-GCBC, was operating flight AF-091 from Paris to Santiago, with scheduled stops in Rio de Janeiro and Buenos Aires. After an uneventful flight from France, the aircraft landed at Rio de Janeiro–Galeão International Airport at 08:34 local time.
Immediately following touchdown, the crew applied reverse thrust. However, the aircraft failed to maintain its centerline and veered toward the right side of the runway. The aircraft traveled approximately 2,000 meters from the touchdown point before exiting the paved surface. It proceeded 765 meters across a grassy area, striking a drainage ditch and a concrete stop. The impact caused the landing gear to collapse backward, with the left wing main gear being torn away. The aircraft then slid 275 meters across a cargo apron, rotating on its fuselage and engines, until it struck a light pole. During the excursion, engines 2, 3, and 4 operated at maximum reverse thrust, while engine 1 surged to maximum forward power. The aircraft sustained extensive damage and was declared a total loss. There were no fatalities among the 265 passengers and 17 crew members, though the aircraft was destroyed.
The investigation
The CENIPA investigation focused on the mechanical failure of the engine number 1 thrust reverser and the subsequent loss of directional control. Investigators analyzed the Digital Flight Data Recorder (DFDR) and Cockpit Voice Recorder (CVR), which revealed that while engines 2, 3, and 4 successfully deployed reversers, engine 1 remained in a closed position while simultaneously accelerating to maximum forward thrust.
The investigation examined the maintenance history of the aircraft, specifically focusing on the pulley support and the components of the thrust reverser control system. Investigators also reviewed the crew's performance, the aircraft's maintenance records, and the existing training and documentation provided by the manufacturer.
Findings
- Mechanical Failure: A failure occurred in the thrust reverser control cable (T1B-5) for engine 1. Due to vibrations from the hydraulic pumps and an unauthorized use of an aluminum pulley instead of the recommended phenolic version, an abrasive agent (alumina) formed, causing the cable wires to wear down. Eventually, 43 wires broke, and the remaining strands failed under the tension of the reverse thrust application.
- Maintenance Deficiencies: The maintenance of the pulley support was inadequate. The use of an unauthorized aluminum pulley and the reuse of an insufficient bolt length caused the side flange of the support to become loose, increasing the relative movement between the cable and the pulley.
- Operational Factors: The pilot applied maximum reverse thrust before confirming the effective transition of all reversers. Additionally, the crew did not recognize the abnormal engine 1 acceleration until the aircraft had reached a point of irreversibility.
- Training and Documentation: The Aircraft Flight Manual (AFM) lacked specific instructions regarding a thrust reverser failure associated with uncommanded engine acceleration. Furthermore, simulator training programs did not include this specific emergency scenario, leaving the crew without specific preparation for such an event.