Incident
The crew initiated an approach to Yuzhno-Sakhalinsk Airport from the southeast under marginal weather conditions characterized by low clouds. While descending at an altitude of 400 meters, the aircraft struck treetops and impacted inverted in a wooded area on the slope of Mt Komissarskaya, located 13.5 km southeast of the airport. The wreckage was discovered one day later.
Occupants and Wreckage
A passenger was found alive but seriously injured. All other 26 occupants—including the pilot Vasily Trofimovich Degtyarenko, copilot Vladimir Parkhomenko, mechanic Vyacheslav Fedorovitch Eliseikina, mechanic Daniel Epifanovich Raznotsvete, and radio navigator Piotr D. Novikov—were killed. The aircraft was totally destroyed upon impact.
Probable Cause
The official investigation determined that the radio navigator mistook two outer markers during the approach. He referenced the outer marker of Korsakov Airbase (frequency 684 kHz) instead of the outer marker of Yuzhno-Sakhalinsk-Bolchaya Yelan civil airport (frequency 670 kHz). The two markers were separated by only 13.5 km and had similar frequencies, contributing to the error. Additional factors included low-cloud-induced lack of visibility that prevented the crew from distinguishing the mountain, failure to use the radio altimeter, and an abnormal action by the crew regarding the direction finder unit.