What happened
On November 29, 1961, a DH-114 Heron MK 2, registered as PH-VLA, was conducting a commercial cargo flight from Frankfurt to Zurich. While approaching Runway 16 at Zurich-Kloten, the crew was alerted by the control tower to heavy fog patches, which reduced visibility to 100 meters at the start of the runway.
During the approach, the crew had swapped their usual roles, with the captain acting as co-pilot and the co-pilot acting as the pilot flying. As the aircraft crossed the runway threshold, it entered a dense fog bank that obscured the runway. The co-pilot decided to initiate a go-around and instructed the captain to apply full power. However, the captain did not hear the command. In the ensuing confusion, the co-pilot retracted the landing gear while focusing on the instruments. Without the expected engine power, the aircraft was unable to climb and was forced to perform a belly landing. The aircraft slid approximately 250 meters along the runway.
The investigation
The investigation established that there were no mechanical or technical failures regarding the landing gear or the aircraft's systems. The crew confirmed the aircraft was in good working order. Investigators examined the flight sequence from the outer marker to the touchdown, noting that the crew's altitude estimates during the fog encounter were likely inaccurate. The investigation also noted that the captain's attention was diverted by an attempt to tune the Automatic Direction Finder (ADF) during the final moments of the approach.
Findings
- The primary cause of the accident was that the captain failed to hear the go-around command issued by the co-pilot.
- The captain's attention was diverted by tuning the ADF, an instrument that was not critical during the final landing phase.
- The decision to initiate a go-around was prompted by sudden visibility loss due to a fog bank at the runway threshold.
- The co-pilot retracted the landing gear without ensuring the engines had reached the required power setting, contributing to the belly landing.