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Eclair propeller

Eclair propellers were selected for the British Sopwith reconnaissance aircraft, the Dorand AR and, above all, the Spad, particularly the Spad VII.

Origins and context

After having coordinated construction of the Caudron G 3, Marcel Bloch (the future Marcel Dassault) was assigned to Farman aircraft flight test acceptance duties in Buc:
“My job was to fly with the pilots and then write a report on the performance and flying qualities of each aircraft”
“This led me to perform many flights as captain to check the climb times and handling of each aircraft.”

In his spare time, Marcel Bloch worked at improving the propeller of the Caudron G 3, having noted its mediocre performance. At that time he was working on his own. To build the propeller whose design he was working on, the young engineer thought of his friend Marcel Minckès, whose father was a furniture manufacturer in the Faubourg Saint-Antoine in Paris. The latter agreed. Marcel Dassault recalls: “He liked people who were bold and enterprising. So he placed at my disposal a cabinetmaker and a few lengths of walnut.”
Having secured the means to make his propeller, Marcel personally supervised the construction: “I prepared a drawing of my propeller, and I outlined the different sections, which enabled the craftsman to make the templates. I stayed at his side as he planed his propeller, in order to guide his hand towards the harmonious lines.”

The propeller was tested at Buc, by one of the Blériot pilots, then presented to the official test centre at Villacoublay: “This propeller was recognized as the best and the furniture manufacturer who had built it under my direction [Hirch Minckès] received an initial order for 50 propellers. The price of each one was 150 francs at the time. We had to give a name to our propeller; we chose ‘Eclair’.”

Spad VII with Éclair propeller
Spad VII with Éclair propeller

Production and operational experience

It initially equipped the Caudron G 3 with its 80hp Clerget engine. It was a good start, particularly as the Battle of Verdun, which had been raging since February 1916, was generating additional orders for aircraft and, consequently, propellers. Marcel Bloch was seconded to work with Hirch Minckès: “As I was starting to get overloaded, I proposed to Potez to come and work with me. He was happy to leave the Caudron design bureau.”

Since it was necessary to achieve an elevated production rate, Marcel Bloch proposed to Hirch Minckès to create a company. The latter consulted with several of his friends, including E. Dumaine, the general manager of the Clerget engine company, who encouraged him to go ahead. Hirch Minckès and his associate, Edeline, founded the Société des Hélices Eclair (Eclair Propeller Company) with Marcel Bloch and Henry Potez as technical directors, seconded from the armed forces.

Several cabinetmakers joined the team, while Clerget encouraged them by placing orders for brake propellers for his test benches. The business was growing and soon filled an entire floor of the furniture production plant on avenue Parmentier, of which they constituted a separate section. The two friends subcontracted machining work to external suppliers: “We had the blades cut externally, we glued them there and then we had to have them shaped. All the furniture manufacturers in the faubourg Saint-Antoine were involved in producing Eclair propellers.”

Caudron G.III
Caudron G.III

The association was a success. Eclair propellers were selected for the British Sopwith reconnaissance aircraft built under licence in France, the Dorand AR and, above all, the Spad, particularly the Spad VII of the most famous French ace of all, Georges Guynemer, a fact that Marcel Bloch was particularly sensitive to: “When Guynemer’s plane, ‘Vieux Charles’ (Old Charles), with its 19 victories, was put on display at the Invalides, I went to see it, and the first thing I saw, naturally, was the propeller. It was a propeller that I had designed and built. That gave me great satisfaction and perhaps a little pride.”

Success for the two sub-lieutenants came in 1917 when their company, in the space of a few months, became one of the four major propeller builders, in a field of no less than 40 manufacturers and 253 different series. The Equipment Inspectorate decided to limit the number of propeller series per aircraft to a maximum of three. The Eclair was one of them. Marcel Bloch and Henry Potez had become part of aviation legend.

Georges Guynemer
Georges Guynemer, in front of a Spad VII