1920 crash of two Savoia S.9s

The crash of two Savoia S.9s in Switzerland occurred on 7 September 1920. The Finnish flying boats were on a ferry flight from Italy to Finland. The cause of the crash was faulty gluing of the propellers. All four crew members were killed.

Crash

After several flight hours, propeller damage occurred on both aircraft. The propellers came apart into their component parts, splintered and severely damaged the delicate structure of the flying boats. Neither crew had a chance; the crashes could not be avoided.

Reasons for the crash

The investigation report of the Zurich public prosecutor's office of 8 February 1922, accessible in the Swiss Federal Archives in Bern, concluded "that the gluing of the propeller laminations was very poor". Specialists of the Swiss Federal Air Office attributed this to the use of two different types of adhesive, which caused the propeller to break into its individual parts in flight. The propeller of Leijer's aircraft was missing, among other things, the top layer of wood, which had come loose from the layer beneath it. The fragments damaged the "Savoia" so severely that a crash was unavoidable. The casein adhesives used were also susceptible to fluctuations in humidity.

Another detail of the wreckage recovered off Zollikon made the Air Office suspicious. The report states that a cotter pin of the tubular bolt that connects the wings and the fuselage had been snipped off hard against the bolt with pliers. The Air Office did not entirely rule out sabotage in its report, but also raised the possibility of negligence by the Savoia workers. "The Savoia S.9 was a very bad aircraft," writes the Italian specialist author Roberto Gentilli. Another argument against sabotage was that the two Savoias had originally been built for the Italians.