Wednesday 16 December 2009

Breguet Br 940/941, French Amazing Blown wings Plane

Louis Breguet, an aristocrat of the Aeronautical Industry was one of those "Master-Strategists".

By selecting his engineers, he knew that his directives would be followed to the letter. He was appreciated and esteemed by all. His influence and his authority were recognized. One of his most devoted colleagues was Georges Ricard.

A passionate for research, he imagined way back in 1948 an aircraft possessing characteristics and performances out of the conventional realm. He created the concept of an airplane capable of short field takeoff and landing (STOL).

He found the technical solution and invented "l'aile soufflée" (which can be approximately translated as the ventilated or blown wing). This was accomplished by equipping the prototype with full span "Venetian blinds" or slotted flaps, which could be extended up to an angle of 97 degrees. The engines powered over-sized propellers, producing an enormous airflow which was deflected downward by the flaps, creating additional lift.

As simple as the concept seemed, the technical application was not. The flaps system had to be designed to eliminate all risks of asymmetry. A single actuator was required, and would be designed by Jacottet-Leduc. Likewise, the synchronization of the Ratier-Figeac propellers had to be full proof, even in case of one of the Turboméca "Turmo II" engine failure. Consequently, Hispano-Suiza developed a concept of single transmission. Finally, to cancel all propeller adverse effects, the inboard engines rotated clockwise, and the outboard engines counter-clockwise.

A 1/75-scale model permitted the first investigations; followed in1954 with a 1/6 motorized radio controlled model, extensively tested in free flight in the private wind tunnel owned by Breguet in his Villacoublay factory. This first phase of studies took place under the greatest of secrecy, despite being financed by a government grant of 210 millions Francs. It was evident that Louis Breguet wanted to avoid "leaks" leading to potential competition. The wing of the prototype Breguet 940 being tested was entirely equipped with the Turboméca "Turmo II" turboprops, for a long bench-test program of endurance and reliability for this concept. In the meanwhile, the 940 prototype was being built at the Villacoublay factory since 1957.

After the ground tests, this compact and rustic looking prototype performed its first flight on the 21st of May 1958 at the Villacoublay airport. Bernard Witt and test mechanic Georges Evrard made a 25 minutes prudent flight in a classic configuration to evaluate the characteristics of this 7 tons aircraft.

In 1959, several flights confirmed the interest for this concept. In June, Witt even made a demonstration at the Le Bourget airshow, resulting in a general amazement while performing unusual low speed maneuvers.

On the 23rd of February 1960, Breguet received an order for a serie prototype with a more refined design capable of transporting 48 passengers or metric tons of freight. It had to be powered by four Turboméca "Turmo III D" of 1200 horsepower each.

This aircraft performed its first flight on the 1st of June 1961 at the Toulouse-Colomiers airport where Breguet owned an industrial plant. The flight-testing would hence continue on a constant basis.

McDonnell Aircraft Corporation intrigued by this revolutionary program establishes contact with Breguet, and on the 6th of June 1962 signed an important agreement of cooperation regarding the 941 and its eventual derivatives.To satisfy the "need of the cause", the airplane received a new livery as required by the American firm whom baptized the STOL "McDonnell 188", and the Breguet 941.01 name would only remain on the vertical fin! Spectacular demonstrations in the big urban areas were conducted during this campaign that ended on the 21st of June 1969. During the four months when the airplane was operational, it flew 350 hours.

Demonstrations would continue in France with the participation of the civilian aeronautics, airports managers, and the French Air Force. It was now a question of developing new and original navigation systems adaptable to the 941, and to integrate it without problem into the existing air traffic presently used. This specialized equipment had been tested successfully during the American campaign.

Let us not forget that the era was 1969…still a long way to solve the navigational problems as it is today with the use of satellites and GPS.
Why is it, that after so many convincing experiments, so many proofs of reliability of the 941, so many evident advantages offered for the problems of air traffic control in zones of high density air traffic, why is it indeed that the Breguet 941 did not succeed?
Too advanced, too far ahead of its time? Maybe.
Too many unknown from an economical standpoint? There is no denying that the technical solutions adapted to the aircraft were complex and expensive, resulting in high maintenance costs.
Too many problems in urban areas? It is a valid argument. Where to establish landing areas? How to determine the flight path to reach those "mini airports" without provoking the reaction of the local populace regarding noise and danger?

Taking into consideration that commercial airlines exploitation of the Breguet would not be feasible, but that the aircraft already built presented a rich potential, they were transferred to the French Air Force. They would now display the French tricolors on their military camouflage.
This "miracle aircraft" which permitted to fly missions night or day, in areas of difficult access where no other aircraft could operate rapidly seduced the military crews. The last of the Breguet 941s reached the end of their potential 1n 1974, after flying and amazing the aircraft Industry for fourteen years.
The Company McDonnell-Douglas was likewise seduced by the Breguet 941 since they later applied its technology to their four-engine YC 15, introduced in flight at the 1977 Le Bourget airshow. Yet, this prototype would be also abandoned.

And so it is, that aeronautical technology very often results in bitter deception

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