Investigation Summary
The approach to Moscow was conducted at night under challenging conditions. During the final approach, the crew reported an altitude of 400 meters, which was considered normal by controllers. However, the radar observer noted that the aircraft deviated slightly to the left of the approach ground line during its final turns. The aircraft never appeared on the glide path radar, suggesting it was already dangerously low. Post-crash analysis revealed that the two primary altimeters were set to different barometric references. The captain's altimeter was set to QFE (990 mb), which would read zero at airport elevation, while the co-pilot's altimeter was set to 1013 mb (standard pressure or QNH). This divergence was a direct violation of Austrian Airlines' standard operating procedures. Because the internal mechanisms were destroyed, investigators could not rule out a technical failure, but the evidence strongly pointed toward a failure in cockpit coordination and altimeter cross-checking.
Final Conclusions
The Russian Board of Inquiry, in a report dated 5 October 1960, concluded the accident was caused by an approach flown below the minimum safe altitude. The board cited three potential reasons for the error: a technical deficiency in the altimeters, the documented divergent barometric settings, or a simple misreading of the instruments by the crew. The investigation noted that the captain had departed from usual airline practice by having mismatched settings, but the specific reason for this deviation could not be determined.
Photographic Evidence (1)
Video Analysis
Failure to Crosscheck (Austrian Airlines Flight 901) - DISASTER BREAKDOWN — An analysis of how mismatched altimeter settings and a lack of cockpit cross-checking led to the crash of a Vickers Viscount near Moscow in 1960.
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Airframe & Maintenance
Crew Experience
Captain
Aged 36, identified as Erwin Wilfing. Total flight time exceeded 2,000 hours; 1,752 hours were on the Viscount type.
First Officer
Aged 39, identified as Ferdinand Freisleben. Total flight time exceeded 2,000 hours; 459 hours were on the Viscount type.
Systems & Failure Modes
Altimeter
Pressure-based instruments used to measure altitude; the two units on Flight 901 were found with divergent barometric sub-scale settings.
NDB (Non-Directional Beacon)
Ground-based radio transmitters used for navigation; the crew used beacons 'MR' and 'M' to align with the Sheremetyevo approach corridor.
Interesting Facts
- 01The aircraft was a nearly new Vickers Viscount, having flown only 1,273 hours since its first flight in February 1960.
- 02The left altimeter was found set to QFE 990 mb, while the right was set to 1013 mb.
- 03Initial impact occurred with trees 380 meters before the main crash site, lopping off tops 4 meters from the peak.
- 04The aircraft lost its left landing flap during the initial tree contact, causing it to roll left before the wing struck the ground.
- 05The flight carried 6 crew members and 31 passengers; 31 people in total were killed, including 5 crew members.
- 06The aircraft was observed deviating slightly to the left of the approach ground line during its final turns.
Safety Actions & Advisories
Cockpit Standardization
The accident highlighted the critical need for standardized altimeter settings and rigorous cross-checking between pilots during the approach phase.