What happened
A passenger flight traveling from Yerevan-Erebuni Airport toward Stepanakert Airport was operating with an increased weight due to the presence of 30 ticketed passengers and 13 unregistered individuals. Because of this heavy load, the captain requested a flight level of 4,500 meters, which was approved by air traffic control, despite the standard route altitude being between 5,100 and 6,600 meters.
During the flight, the crew transitioned from the control of Kafan Airport to the Stepanakert controller. The Kafan controller instructed the aircraft to maintain 4,500 meters until the descent phase. However, the aircraft descended to 3,900 meters while flying through a cloud layer that had an upper limit of only 3,000 to 3,300 meters. The flight crew did not communicate their precise coordinates, and the controller did not utilize radar to verify the aircraft's position.
At 10:08, the captain requested a frequency change to Stepanakert, providing an inaccurate report that the aircraft was maintaining 3,900 meters. Because the Kafan controller could not see the aircraft on radar and lacked direct communication with the Stepanakert facility, the handoff was permitted. Upon contacting Stepanakert, the captain requested a further descent to 2,400 meters. The Stepanakert controller, lacking radar monitoring capabilities, authorized a descent to 3,000 meters near the NDB. At 10:09:57, the aircraft struck a rocky mountain slope at an altitude of 2,520 meters. The crash resulted in 47 fatalities.
Findings
- The aircraft was operating significantly below the cloud ceiling while descending.
- The flight crew provided inaccurate altitude information to air traffic control.
- The controller at Kafan Airport failed to verify the aircraft's position via radar.
- The Stepanakert controller lacked the radar infrastructure necessary to monitor the aircraft's flight path and altitude.