Riout 102T Alérion Ornithopter.
French engineer René Louis Riout was interested in ornithopters—aircraft that used flapping wings to achieve flight. His first ornithopter, the DuBois-Riout, was originally built in 1913, but testing was delayed because of World War I. The aircraft never achieved sustained flight and was destroyed in an accident in 1916.
After the war, Riout designed a new ornithopter that had two sets of flapping wings. He continued to refine his ornithopter design, but no one was interested in producing such a machine. Riout worked for a few other companies, including a time with Bernard Aircraft Company from 1927 to 1933.
In 1933, Riout presented his ornithopter designs and research to the STAé or Technical Service of Aeronautics. Riout’s presentation included designs and models of two- and four-wing ornithopters.
The models weighed 100 gram and 500 gram and performed flights up to 100 meters. As a result of these tests, STAé ordered a 1/5-scale model with wings powered by an electric motor.
The 1/5-scale model was built in 1934. From 11 November 1934 to 1 February 1935, the model underwent 200 hours of testing in the wind tunnel near Paris, France. The successful tests established the feasibility of Riout’s design and indicated the ornithopter would be capable of 200km/h if it were powered by a 90hp engine.
The ornithopter was designated Riout 102T Alérion. The word alérion is the name of a mythical bird about the size of an eagle. Behind the cockpit were two pairs of flapping wings. The two-spar wings had metal frames and were fabric-covered.
The Riout 102T had a 8m wingspan and was 6.4m long. The ornithopter weighed 500kg empty and 630kg fully loaded.
After some preliminary testing, the 102T was moved to the wind tunnel at Chalais-Meudon in early 1938. First, tests lasting two minutes with the wings stationary were conducted. These tests were followed by wing flapping tests.
On 12 April 1938, the Riout 102T was in the wind tunnel undergoing a flapping test with a wind velocity of 130km/h. When the engine speed was increased to 4500rpm, one wing folded, quickly followed by the other three. The outer third of all the wings bent, with the right wings folding up and the left wings folding down.
There was no interest to fund repairs or continue the project after the aircraft was damaged. The damaged wings were discarded, but the fuselage of the 102T was somehow preserved.
Today, the Riout 102T Alérion is undergoing restoration and is on display at the Espace Air Passion Musée Régional de l’Air in France.