Investigation Summary
The flight was a multi-stop domestic service that had departed Malmo with stops in Kristianstad, Vaxjo, and Jonkoping. During the final leg to Stockholm, the aircraft encountered icing conditions. The Vickers Viscount utilized a thermal anti-icing system that relied on heat from the engines. However, the crew operated engines two and three at a reduced power setting during the descent, which caused the temperature of the anti-icing air to drop below the threshold necessary to prevent ice buildup on the tailplane. As the aircraft reached 1,150 feet (350 meters), and the crew extended the flaps to 40 degrees, the disrupted airflow over the iced horizontal stabilizer caused a tailplane stall. This resulted in an uncontrollable nose-down pitch. The aircraft entered a near-vertical dive, impacting a residential parking lot at a speed of approximately 210 knots and an angle of 110 degrees.
Final Conclusions
The Swedish Statens haverikommission (SHK) concluded that the primary cause was a stabilizer stall due to ice accretion. The report highlighted that the de-icing system's failure was a direct result of insufficient engine power settings. Furthermore, the investigation cited deficiencies in the pilot's flight manual regarding the operation of the de-icing system and the specific effects of ice on the stabilizer. The crew had also not been adequately warned about the severity of icing conditions in the Stockholm area that morning.
Photographic Evidence (1)
Video Analysis
Linjeflyg Flight 618 Aftermath Footage | 15 January 1977 Kälvesta, Sweden — Historical news footage showing the wreckage of SE-FOZ in the Kälvesta parking lot and the recovery efforts following the crash.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Systems & Failure Modes
Thermal Anti-Icing System
A system that uses heated air from the engines to prevent ice formation on leading edges. On the Viscount, this system requires specific engine power settings to maintain effective temperatures.
Horizontal Stabilizer
The tail surface responsible for pitch stability. Ice buildup here can cause a 'tailplane stall,' which leads to an abrupt, uncommanded nose-down pitch, especially when flaps are extended.
Interesting Facts
- 01The aircraft was being wet-leased by Linjeflyg from Skyline due to delays in Fokker F28 deliveries.
- 02The impact occurred at a speed of 210 knots and an angle of 110 degrees.
- 03The horizontal stabilizer was found inverted in the wreckage, one of the few recognizable parts.
- 04The accident led to the eventual bankruptcy of the operator, Skyline, after Linjeflyg terminated their contract.
Safety Actions & Advisories
Flight Manual Revisions
The investigation recommended updating the Vickers Viscount flight manuals to provide clearer instructions on maintaining engine power for anti-icing and better information on the risks of tailplane icing.