What happened
On April 27, 1970, a SIAT 223 departed Altenrhein, Switzerland, on a training flight destined for Nuremberg, Germany. The aircraft, operated by SWISSAIR, was carrying a pilot and two flight students. During the approach to Nuremberg Airport, the crew was instructed by the tower to maintain a safe distance behind two approaching Boeing jets and to perform a short landing on runway 28.
As the aircraft approached the runway threshold at an altitude of approximately 30 to 50 meters, it encountered the wake turbulence generated by a Boeing jet that had just performed a go-around. The aircraft suddenly rolled violently to the right into a knife-edge attitude before transitioning into a steep descent. Despite the pilot's efforts, the control inputs were insufficient to recover the aircraft to a normal flight attitude. The aircraft struck the ground approximately 270 meters before the runway threshold, resulting in heavy damage to the landing gear, the left wing, and the left flap.
The investigation
The investigation examined the flight path, the aircraft's mechanical condition, and the environmental factors present at the time of the accident. Investigators confirmed that the SIAT 223 was properly registered and that the pilot held valid licenses. A technical inspection of the airframe and engines revealed no mechanical defects that could have contributed to the accident. The investigation also reviewed radio communications between the crew and Nuremberg Tower, noting that the crew had identified the preceding Boeing aircraft and were following instructions for a short landing.
Findings
- The primary cause of the accident was the encounter with wake turbulence produced by a heavy jet aircraft performing a go-around.
- The separation distance of approximately 3 to 4 kilometers between the aircraft and the preceding jet was insufficient to allow the vortices to dissipate.
- The aircraft was flying at a speed of 90-95 knots, which was 10-15 knots above the recommended approach speed and significantly above the stall speed for the configured flaps.
- The impact caused the left main landing gear to collapse and resulted in substantial structural damage to the wing and flaps.