What happened
During a nighttime approach, the flight crew abandoned the established instrument approach procedure to continue the descent using visual references. This transition led to a collision with mountainous terrain. During the approach, the crew demonstrated several errors in managing flight tasks, including the use of an incorrect frequency for pilot-controlled lighting and the communication of inaccurate descent altitudes and approach headings. Additionally, the crew incorrectly believed the airport was obscured by cloud cover, despite receiving weather data that indicated otherwise. The aircraft descended below the required altitudes during this phase of flight.
Findings
Investigations revealed that the crew did not conduct a proper briefing or review of the instrument approach procedure before departure. The crew's performance was marked by several cognitive deficiencies, such as descending below safe altitudes and losing situational awareness regarding the surrounding terrain. A significant factor was the black hole phenomenon, where the lack of visual cues over dark, featureless terrain created a false perception that the aircraft was at a higher altitude than its actual position. This illusion likely prompted the crew to fly a lower approach, compromising terrain clearance. While a ground proximity warning device may have issued an alert, the specific timing of any such warning remains undetermined. While the crew's errors were consistent with the effects of fatigue, investigators could not definitively confirm the exact role of fatigue-related impairment in these specific task failures.