What happened
On December 17, 2001, a Boeing 737-53A, registration PT-SSI, operated by Rio Sul Serviços Aéreos Regionais, was conducting a flight from Rio de Janeiro (Santos Dumont) to Belo Horizonte (Pampulha). Due to adverse weather conditions at the original destination, the flight was diverted to Confins Airport (SBCF).
During the ILS approach to runway 16, the aircraft encountered significant wind fluctuations. The pilot flying reported feeling a sudden downdraft near the runway threshold that pushed the aircraft below the glide slope. The aircraft struck the ground forcefully before the runway threshold, causing the left landing gear to collapse. Following the impact, the aircraft slid approximately 1,700 meters along the runway, supported by the left engine, the left flap, and parts of the fuselage. All 106 occupants (6 crew and 100 passengers) escaped without injury, though the aircraft sustained heavy damage.
The investigation
The CENIPA investigation focused on the flight data recorder (FDR) and cockpit voice recorder (CVR) analysis. The investigation established that the aircraft was experiencing strong tailwinds during the approach segments. Flight data revealed significant variations in indicated airspeed (IAS) and engine power (N1) as the crew attempted to maintain the vertical flight path. The investigation also noted that the aircraft's sink rate and glide slope alarms triggered multiple times (three and five times, respectively) during the final approach.
Furthermore, the investigation examined the cockpit environment, finding a high degree of informality between the crew members. The analysis revealed that the co-pilot failed to perform required Standard Operating Procedure (SOP) call-outs, and the crew did not execute a missed approach despite the deteriorating flight conditions and multiple warnings.
Findings
- Wind shear/Microburst: The presence of wind shear and a potential microburst, driven by local orography and tailwinds, was a primary environmental factor.
- Failure to execute missed approach: The crew disregarded the sink rate and glide slope alarms, failing to initiate a go-around as required by SOPs.
- Loss of situational awareness: A climate of informality and high mutual trust between the experienced commander and the co-pilot led to a reduced level of alertness and a failure to challenge risky flight parameters.
- Communication breakdown: The co-pilot failed to perform essential call-outs regarding airspeed and attitude deviations, which could have alerted the commander to the worsening conditions.
- Inadequate weather assessment: The crew did not sufficiently account for the risk of wind shear given the prevailing meteorological conditions and local terrain.