OK001
1976-JUL-28 · Zlaté piesky lake, near Bratislava, Czechoslovakia

ČSA Czechoslovak Airlines — Flight OK001

ČSA Flight 001 crashed into the Zlaté piesky lake during an unstabilized approach to Bratislava-Ivanka Airport. After an excessively fast and steep descent, the crew improperly used thrust reversal in flight, leading to the failure of engine number 3. During the subsequent emergency, the crew mistakenly feathered the propeller of the functioning number 4 engine. While attempting a go-around on only two engines, the crew tried to restart the number 4 engine at a critically low altitude and speed, causing the aircraft to bank sharply and plunge into the lake.

Aircraft
Ilyushin Il-18V
Registration
OK-NAB
Phase
Approach
Cause
Pilot Error
Souls on Board
79
Fatalities
76
Origin → Dest
Prague-Ruzyně International Airport (PRG) → Bratislava-Ivanka Airport (BTS)
Report
Final Report

Investigation Summary

The accident was characterized by a series of severe procedural deviations. The approach was highly unstabilized, with a descent rate of 22 m/s (more than double the standard 10 m/s) and speeds fluctuating wildly between 435 km/h and 225 km/h. In an attempt to shed speed, the crew deployed full flaps directly from the retracted position and engaged reverse thrust on the inner engines (2 and 3) while still at an altitude of approximately 1,000 meters. This unauthorized use of reverse thrust caused the number 3 engine to fail. In the ensuing confusion, the crew mistakenly feathered the number 4 engine instead of the failed number 3. This left the aircraft with both engines on the right side producing no thrust. During the attempted go-around, the crew's decision to restart the number 4 engine at just 40 meters altitude created massive asymmetric drag and torque that they could not counteract, leading to a terminal loss of control.

Final Conclusions

The investigation concluded the crash was caused by multiple pilot errors, including the unauthorized use of thrust reversal in flight, improper flap management, and the erroneous feathering of a healthy engine. The immediate cause of the impact was the attempt to restart the number 4 engine at an altitude and speed insufficient to maintain control under asymmetric thrust conditions.

Photographic Evidence (1)

© Wikimedia Commons

Video Analysis

No video analysis linked for this case file yet.

Airframe & Maintenance

Engines
Ivchenko AI-20K

Systems & Failure Modes

i

Thrust Reversal

Engaged by the crew at an altitude of 1,000 meters to slow the aircraft, leading to engine failure.

i

Propeller Feathering System

Used to stop a propeller from spinning to reduce drag; the crew feathered the wrong engine (No. 4) during the emergency.

i

Ivchenko AI-20K Engines

Turboprop engines; the number 3 engine failed due to improper manipulation of thrust levers.

Interesting Facts

  • 01The aircraft was an Ilyushin Il-18V manufactured in 1959.
  • 02Four passengers were initially pulled from the wreckage alive, but one died of his injuries the following day, leaving three survivors.
  • 03The descent rate during approach was 22 m/s, significantly higher than the required 10 m/s.
  • 04Flaps were moved from 0 degrees directly to the full landing position, violating standard procedures.
  • 05The crash remains the deadliest aviation accident in the history of modern-day Slovakia.

Safety Actions & Advisories

Thrust Reversal Procedures

Reinforcement of flight manuals to strictly prohibit the engagement of thrust reversers while airborne.

Location

Zlaté piesky lake, near Bratislava, Czechoslovakia · 48.1819, 17.1900

Case File History

  1. New evidenceUpdated event timeline and findings.

Related Cases

Case ID · csa001-1976Last updated · Filed

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