What happened
On August 18, 1970, a Tupolev 124 operated by Ceskoslovenske Aerolinie (CSA), registration OK-TEB, was performing a scheduled flight from Prague to Zurich. During the approach to Zurich Airport, the aircraft touched down on runway 16 with its landing gear still retracted. The resulting belly landing caused the aircraft to come to a halt after 175 meters. While the impact caused a fire that was quickly extinguished by airport fire services, there were no fatalities or injuries among the 14 passengers and 6 crew members. The aircraft sustained heavy damage, though the passengers, cargo, and mail remained undamaged.
The investigation
The investigation examined the cockpit procedures, the mechanical state of the aircraft, and the crew's performance. Investigators found that the aircraft was in good technical condition, though the cabin pressure regulation system was malfunctioning, requiring manual operation. The investigation also reviewed the crew's experience and the airline's operational procedures. It was noted that the crew had been on duty for several hours without a break for food, which may have impacted concentration. Furthermore, the investigation found that checklists were not being used regularly on this flight, and the crew had not performed a final check of critical flight parameters before landing.
Findings
Several contributing factors led to the landing gear failure:
- The flight mechanic failed to extend the landing gear after receiving the command from the captain.
- The landing gear warning horn had been intentionally deactivated by the captain to prevent distractions during the approach briefing.
- The flight mechanic was distracted by the need to manually manage the malfunctioning cabin pressure regulation.
- The landing gear indicator lights on the Tupolev 124 remained red during flight, making it difficult for the crew to distinguish between the retracted and extended states.
- There was a lack of clearly defined roles and responsibilities regarding cockpit coordination and cross-monitoring among the crew members.
Safety action
While the report does not list specific regulatory changes, it emphasizes the necessity of clearly defined duties for every crew member during critical flight phases. The investigation highlights that effective teamwork and mutual monitoring are essential to prevent such errors, especially in complex aircraft environments.