Accident Description
The aircraft was completing its approach to Moscow-Sheremetyevo Airport at night under poor weather conditions. After executing its fourth turn on the approach, the crew continued descending below the glide path. The aircraft struck trees and crashed in a wooded area located 11 kilometers short of runway 07. The aircraft was destroyed. Five crew members and 26 passengers were killed, while six other occupants sustained serious injuries. At the time of the accident, visibility was limited due to night conditions, fog, and rain.
Investigation Findings
The official investigation determined that there were no technical deficiencies in the aircraft itself, nor any meteorological phenomenon involved in the accident. Austrian observers participating in the investigation expressed the opinion that the accident was related to altitude measurement. Evidence from radio communications and examination of the wreckage indicated that the crew believed they were flying at the normal approach altitude. The erroneous altitude measurement could be attributed to one of three potential causes: a technical deficiency of either of the two altimeters, divergent altimeter settings, or omission of altimeter reading or erroneous reading of the altimeters.
The internal mechanisms of both altimeters were so heavily damaged that it could not be determined whether they were functioning accurately at the time of the accident. Both altimeters were set to the correct atmospheric pressure, but their settings differed: the left altimeter was set to QFE 990 millibars, while the right altimeter was set to 1013 millibars. Given the prevailing atmospheric pressure conditions, these settings could have corresponded to both QNH and standard pressure. Such divergent settings are at variance with the usual procedures of Austrian Airlines. The reasons prompting the flight captain to depart from standard practice could not be ascertained.
Probable Cause
The official probable cause, as reported, states: The investigations revealed that there were no technical deficiencies in the aircraft itself or a meteorological phenomenon involved in the accident. The Austrian observers participating in the investigation of the accident were of the opinion that the accident was related to altitude measurement, inasmuch as it was apparent from radio communications as well as from the examination of the wreckage that the crew believed that they were flying at the normal approach altitude. The erroneous altitude measurement may be attributed to: a technical deficiency of either of the two altimeters, the divergent settings of the altimeters, or omission of altimeter reading or erroneous reading of altimeters. The internal mechanism of both altimeters was so heavily damaged that it could no longer be ascertained whether, at the time of the accident, the altimeters were functioning accurately. Both altimeters were set to the correct atmospheric pressure but their settings differed, namely the left altimeter was set at QFE 990 millibars and the right altimeter at 1013 millibars, which in view of the prevailing atmospheric pressure conditions, could have corresponded both to QNH and to the standard pressure setting. Such divergent settings are at variance with the usual procedure of Austrian Airlines. The reasons prompting the flight captain to depart from the usual practice could not be ascertained. It was not possible to reach a categorical conclusion as to which of the three causes were responsible for an approach below the minimum flying altitude.