Background
The aircraft operated a passenger service from Yerevan-Erebuni Airport to Stepanakert Airport. Besides 30 ticketed passengers, the crew boarded 13 unregistered individuals. The total occupancy was 47.
Flight History
With the heavy load, the captain requested a lower cruising altitude of 4,500 meters, which air traffic control (ATC) granted. The normal altitude for the route ranged from 5,100 to 6,600 meters, and the minimum safe altitude was 4,516 meters. At 09:59, after passing the Azizbekov NDB, the Kafan Airport controller took over. The controller instructed the crew to maintain 4,500 meters until the descent point. The crew was then cleared to descend to 3,900 meters over mountains covered by a cloud deck with an upper boundary of 3,000–3,300 meters.
The flight crew did not report their exact position, and the controller did not verify it on radar. The aircraft reached 3,900 meters at 10:07 and continued descending without informing the controller. At 10:08, the captain requested contact with Stepanakert while falsely reporting an altitude of 3,900 meters. The Kafan controller, not observing the aircraft, unaware of its actual altitude, and lacking direct communication with Stepanakert, allowed the frequency switch.
The captain then reported to the Stepanakert controller an altitude of 3,900 meters and requested descent to 2,400 meters. The Stepanakert controller, without radar, permitted descent to 3,000 meters until the NDB. At 10:09:57, while descending in clouds, the aircraft struck a rocky mountain slope at an altitude of 2,520 meters. All 47 occupants were killed.
Probable Cause
The official investigation determined the accident resulted from:
- The captain's violations of flight rules, including unsatisfactory navigation, route straightening, and premature unauthorized descent below minimum safe altitude, leading to collision with terrain.
- Violations by ATC dispatchers at Erebuni, Kafan, and Stepanakert, failing to comply with air traffic control rules and not intervening in the crew's unauthorized actions, preventing timely obstacle avoidance. A stereotype existed among Yerevan-Stepanakert dispatchers to allow crew-requested approach conditions. These violations were possible due to shortcomings in flight operations and ATC organization within the Armenian and Azerbaijani State Administrations.