Yves le Prieur

Yves Paul Gaston Le Prieur (23 March 1885 – 1 June 1963) was an officer of the French Navy and an inventor.

Le Prieur followed his father in joining the French navy. As an officer he served in Asia and used traditional deep sea diving equipment. He studied Japanese and became sufficiently proficient to be promoted to military attaché and translator at the French Embassy in Tokyo. While there he became the first Frenchman to earn a Black Belt in judo, and the first person to take off in a plane, a glider, from Japanese soil in 1909.

The glider, named Le Prieur No. 2 after an earlier No. 1 unmanned prototype, was 7.2 m long, 7.0 m wide, and weighed 35 kg. The frame was made of Japanese bamboo, which was covered with calico. Le Prieur had designed the glider in collaboration with Shirou Aibara, a Lieutenant of the Japanese Navy, and Aikitsu Tanakadate, a professor at Tokyo Imperial University. The first flight took place in December 1909 just to the East of the University of Tokyo at Shinobazu Pond with Le Prieur sitting on the glider's main wing. The first flight covered 200 m at an altitude of 10 m.

During the First World War he invented the plane-mounted Le Prieur rocket launcher for bringing down observation balloons. This weapon system, which allowed an airplane to fire a single volley of rockets in close succession (the design planned for simultaneous launch, but technical unreliability made it impossible in 1916) was remarkably effective against the German observation balloons, and was only phased out when tracer rounds and incendiary bullets for the on-board machine guns (with similar efficiency and larger ammunition capacity) became widespread among the Allied air forces near the very end of the war.

Le Prieur also patented a number of designs for mechanical lead computing sights for both ship to ship and anti-aircraft guns.

In 1925 Le Prieur saw a demonstration at the Industrial and Technical Exhibition in Paris of a diver using a breathing apparatus invented by Maurice Fernez. The Fernez breathing apparatus consisted of a simple T-shaped rubber mouthpiece. On one side this was connected to a long tube down which air was pumped from the surface. On the other side of the mouthpiece, excess and exhaled air escaped from a simple rubber "ducks bill" valve. The diver's nose was pinched by a pair of spring clamps ("pince nez") to prevent ingress of water, and his eyes were protected by small goggles with rubber surrounds.

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