What happened
On July 17, 1973, a SATA Convair CV-640, registration HB-IMM, was operating a charter flight from Zurich to Tromsø, Norway, with a planned refueling stop in Oslo. During the approach to Tromsø, the crew elected to land on runway 19, a decision influenced by better navigational aids and the runway's upward gradient. The approach was conducted under challenging conditions, including a 10-knot tailwind, a steep 4-degree glide path, and a wet runway surface.
Upon touchdown, the aircraft experienced an extremely hard three-point landing. The impact was severe enough to damage all three landing gear struts and cause propeller tips to strike the runway. The aircraft subsequently lifted off again, landing a second time on its nose gear. The force of the impact ruptured hydraulic lines, rendering both the normal and emergency braking systems ineffective. As the aircraft continued to roll, it drifted left, exited the runway, and came to rest on its belly in soft ground, approximately 8 meters from the runway edge. The impact caused the left propeller to be torn from the engine.
The investigation
Investigators examined the wreckage, the flight crew's records, and the local meteorological conditions. The investigation confirmed that the aircraft was airworthy and the crew held valid licenses. Technical analysis of the wreckage revealed that the landing gear had been pushed backward into the wing structure and that the fuel tanks had been ruptured.
Regarding the approach, the investigation found that the crew lacked instrument approach charts for the alternative runway 01, which would have provided a more favorable headwind and higher cloud base. Furthermore, the investigation scrutinized the aircraft's fuel reserves, finding that the expected fuel remaining over Tromsø did not meet ICAO minimum standards.
Findings
- The crew extended the landing flaps to 40°, exceeding the operational limit of 33° for this aircraft type during landing.
- There was a lack of coordination between reducing engine power and managing the aircraft's pitch during the flare.
- The approach was complicated by a 10-knot tailwind and a steep 4-degree glide slope.
- The crew did not possess the necessary approach charts for runway 01, preventing a safer landing alternative.
- Improper coordination of power reduction and flap extension was the primary factor in the loss of control during the flare.