What happened
On November 18, 1999, at 08:45 local time, a Fokker 100, registration PT-MQL, was performing a scheduled flight from Congonhas (CGH) to Santos Dumont (SDU) in Rio de Janeiro. The aircraft was carrying 100 passengers and 6 crew members.
During the approach to runway 20L, the aircraft touched down on the PAPI ramp before reaching the runway threshold. Following the initial contact, the left main landing gear strut fractured. After a slight subsequent rise in the aircraft, a second impact caused the left landing gear to detach completely from the airframe. The aircraft then veered left off the runway into a grassy area, where the left wing made contact with the ground. The pilot, after confirming there was no fire, ordered a normal evacuation through the main door. All 100 passengers and 6 crew members escaped without injury.
The investigation
The CENIPA investigation examined the flight data recorder (FDR) and cockpit voice recorder (CVR), as well as the fractured landing gear components. Technical analysis by the Institute of Technological Research (IPT) revealed that the fractures originated near the adapter and bolt holes of the left landing gear. The analysis identified two failure patterns: one resulting from high stress during the impact and another caused by pre-existing cracks. The investigation also noted that the aluminum alloy used in the gear showed susceptibility to intergranular corrosion, likely due to a failure in the heat treatment process.
Operational analysis revealed that the flight crew did not adhere to the company's "Sterile Cockpit" procedure, as they engaged in non-operational conversation during the descent. Furthermore, the FDR indicated a tailwind component that increased the sink rate, which the crew failed to correct effectively. The investigation also noted that the pilot's approach profile deviated from the standard operating procedure (SOP) to intentionally touch down near the 500-foot mark.
Findings
- Human Factors: The crew's attention was diverted by a vessel crossing the final approach path, which impaired their perception of the increasing sink rate. Additionally, the crew failed to maintain a sterile cockpit environment.
- Material Factors: The left landing gear suffered from pre-existing cracks potentially caused by intergranular corrosion due to improper heat treatment of the aluminum alloy.
- Operational Factors: An unexpected tailwind increased the descent rate, and the pilot's decision to fly a steeper, non-standard approach profile contributed to the touchdown occurring before the runway threshold. The crew's failure to properly coordinate the monitoring of the aircraft's descent rate while observing the vessel also contributed to the incident.