In January 1920 Damblanc and the Alerion were paid a visit by Japanese General Count Gaishi Nagaoka, seen here third from right. Damblanc is furthest right. As well as being an important figure in early Japanese aviation, Nagaoka was also renowned at the time for having the world’s second-largest moustache!

AN ALERION ROTARY WING IN THE WORKSHOP

With one of its two intended le Rhone rotary engines and only one of its rotary wings fitted, Louis Damblanc’s Alerion is prepared for testing at Villacoublay on September 14, 1920. Damblanc had dismissed the co-axial concept and was instead pursuing the idea of two laterally mounted rotors, as per Louis Lacoin’s patents.

The Alerion is prepared for testing at Villacoublay on September 14, 1920. Only one rotary wing and le Rhone engine has been fitted and the empennage, comprising fin, rudder and tailplane, is also missing.

Two views of the model of the Alerion which may have been displayed at the 6e Salon de l’Aeronautique in Paris in December 1919 and January 1920. The fuselage remained uncovered to avoid aerodynamic interference with the rotors, but presumably also to keep the machine’s weight down; it would need all the help it could get.

The Alerion begins to come together at the Institut Aerotechnique de St-Cyr during the winter of 1919-20. The rotary wings were constructed along the same lines as a conventional wing, with ribs and spars that were to be covered with fabric and doped. The undercarriage was carried on a standard V-frame with an aerodynamic fairing fitted to the axle.

Crunch! Taken a few minutes after the previous photo, this one shows the Alerion after the engine run, during which substantial damage was inflicted; the rotor was all but destroyed, as was the shaft on which it was fitted and the upper lateral support beam. It was the end of the short career of the Alerion.

One of the illustrations included in Damblanc’s 1922 patent for an intriguing helicopter design; quite how it was to work remains something of a mystery, although it may have operated on a similar basis to the later German Focke-Wulf “Triebflugel” concept.

Of more recognisably conventional configuration was Louis Lacoin’s 1926 patent describing an Alerion-type machine - but, interestingly, with what appears to be an early incarnation of the “fenestron” ducted-fan later used in various French helicopter designs.

Illustrations from Louis Lacoin’s 1915 patent for “a rotary-wing aircraft with the general shape of an aeroplane”. The tail surfaces are of conventional configuration.

This plan view from the 1915 patent of Lacoin’s machine perhaps shows the aircraft’s configuration to best advantage; note its distinctive “shamrock”-shaped rotary wings.