What happened
On September 29, 1991, an EMB-721C, registration PT-EQC, departed from Aquidauana, MS, bound for São Carlos, SP, with three occupants on board. During the flight, the aircraft encountered adverse weather conditions characterized by low cloud ceilings and heavy convective activity, including Cumulonimbus (CB) and Stratocumulus (ST) clouds.
Witnesses near Sidrolândia, MS, reported hearing the aircraft's engine repeatedly accelerating and decelerating. Shortly thereafter, debris from the aircraft was observed falling from the sky, followed by the main fuselage, which was rotating around its longitudinal axis. The aircraft struck the ground at an angle of approximately 60 degrees, resulting in the three fatalities on board and the total destruction of the aircraft.
The investigation
CENIPA's investigation focused on the pilot's lack of preparation and the aircraft's technical status. The investigation established that the pilot was not rated for Instrument Flight Rules (IFR) and lacked experience in instrument flying. Furthermore, the aircraft was not certified for IFR operations, despite being equipped with an autopilot.
Physical evidence at the crash site, including the separation of the left wing at the fuselage attachment point and wrinkling of the airframe surfaces, indicated that the aircraft had been subjected to extreme G-loads. The investigation also noted that the aircraft's annual maintenance inspection was overdue. Additionally, the pilot had failed to file a flight plan, did not consult weather reports for the route, and maintained no communication with air traffic control.
Findings
- Spatial Disorientation: The pilot likely experienced spatial disorientation while flying in IMC, leading to extreme and improper control inputs.
- Excessive G-Load: The structural failure of the left wing and airframe deformation suggest the pilot applied excessive and inadequate control commands, exceeding the aircraft's structural limits.
- Inadequate Planning: The pilot failed to check meteorological conditions and did not prepare for the flight requirements.
- Operational Non-compliance: The flight was conducted without a flight plan, without communication with ATC, and involved an unqualified pilot entering IFR conditions.
- Psychological Factors: The pilot's personality traits, including high self-confidence and impulsivity, likely contributed to the decision to proceed into dangerous weather.