What happened
On December 28, 1991, at approximately 08:39 local time, an EMB 110 Bandeirante, registration PT-GKX, was performing a scheduled air transport flight from Cuiabá to Juará. While descending through flight level 075, the crew of the PT-GKX experienced a sudden impact on the rear right side of the aircraft. Upon inspection, the crew discovered damage to the right horizontal stabilizer and elevator, and observed another aircraft in an uncontrolled descent.
Simultaneously, a Beechcraft BE-36 Bonanza, registration PT-ODB, had departed from Fazenda Araputanga for Pontes e Lacerda. This flight was not known to air traffic control authorities. During the descent of the PT-GKX, its right horizontal stabilizer struck the right wingtip of the PT-ODB. The impact tore the wingtip from the Bonanza, causing the aircraft to enter an abnormal attitude. The PT-ODB subsequently struck the ground at a nearly 90-degree angle, resulting in the total destruction of the aircraft and 6 fatalities (the pilot and five passengers). The PT-GKX was able to continue its flight and land safely in Juará.
The investigation
CENIPA's investigation focused on the operational discrepancies between the two aircraft. The crew of the PT-AMD was found to be fully qualified with valid licenses and medical certificates. In contrast, the pilot of the PT-ODB was found to be operating without any formal flight training, licenses, or medical certificates.
Investigators examined the navigation and communication methods used by both parties. While the PT-GKX followed its flight plan, the investigation revealed that the pilot of the PT-ODB relied exclusively on GPS and autopilot. Furthermore, evidence suggested a critical error in altimeter setting: the pilot of the PT-ODB had a habit of zeroing his altimeter at the departure airfield rather than using standard pressure settings. This practice caused a discrepancy of approximately 1,000 feet between his perceived altitude and his actual altitude, leading to a fatal misunderine of separation.
Findings
- The pilot of the PT-ODB was unlicensed and lacked formal flight training, relying on empirical knowledge.
- A critical error in altimeter setting (zeroing the altimeter at the field) caused the pilot to believe he was at a different altitude than he actually was.
- Ineffective communication and a lack of situational awareness between the two crews prevented the avoidance of the conflict.
- The pilot of the PT-ODB relied solely on GPS and autopilot for navigation in an area with minimal navigational aids.
- The pilot of the PT-ODB operated with high self-confidence despite lacking the necessary legal qualifications and medical certification.