14 Bis - 100 Years

Posted by : Fabiano Gallindo Tuesday, November 14, 2006

The 14-bis, also known as Oiseau de proie (French for "bird of prey"), was an early fixed-wing aircraft designed and built by Brazilian inventor Alberto Santos-Dumont. On November 12, 1906, in Bagatelle, France, it performed the first publicly witnessed unaided flight by a heavier-than-air aircraft. Earlier flights, such as that made by the Wright Brothers had required favourable wind directions, catapults or other such devices to take off.

Conception, development, and initial tests

In June of 1905, Gabriel Voisin tested a glider by having it towed by a fast boat down the Seine. The glider's wing configuration was made up of Hargrave cells, a box-kite-like structure that allowed for great lift and structural strength with minimal weight. Voisin was towed into the air and flew for over 500 feet as the boat pulled him and his aircraft. In the aviation-crazy Paris of the early 1900s, this established the Hargrave cells as a configuration to be developed into heavier-than-air aircraft, not simply into kites. Santos-Dumont lived in Paris at the time, and was by then one of the most active "aeronauts" in Europe, having developed a long series of dirigibles that displayed unparalleled agility, speed, endurance, and ease of control.

During late 1905 and early 1906, French aviation authorities, seeing the rapid development in aviation at the time, offered prizes for the first heavier-than air machines to be flown for 25 meters and for 100 meters. Ferber, a captain in the French Army, was experimenting with gliders and kept in touch with Chanute and with the Wright brothers. Voisin teamed up with Louis Bleriot to develop the boat-towed glider into a fixed-wing aircraft.

At around that time, while watching the Cote D'Azur speedboat races, Santos-Dumont noticed that Antoinette-type engines, made by Levavasseur, offered great power and were quite lightweight.

Putting all this together, Santos-Dumont designed and built a Hargrave-cell biplane powered by an Antoinette engine. This was originally done in secrecy, only known to his team of builders and craftsmen. The wings were at the very back configured in a dihedral, each wing containing three cells. The 24 hp Antoinette sat between the wings, with the pilot's compartment immediately ahead (where the pilot stood), and with the pusher-propeller immediately behind. A movable cell at the nose, actuated by cables originally manufactured for church-tower clocks, allowed for steering and altitude adjustments. This forward-mounted-mini-wing layout would later come to be called a "canard" (after a Bleriot aircraft of the same layout was said to look like a duck. This name is still used to describe aircraft with wing-like surfaces placed near the nose, whether or not they are duck-like). The structures of the Santos-Dumont biplane were made of bamboo, with Japanese silk surfaces, and joints made of aluminum, a very exotic material at the time.The aircraft was transported from Neuilly, where it was built, to Bagatelle, where it could be tested. In order to simulate flight-like conditions, Santos-Dumont attached the aircraft to the belly of his latest dirigible, the Number 14. Due to this configuration, the plane came to be known as 14-bis. The forces imposed by the aircraft pulled at the dirigible in dangerous ways, nearly tearing it and allowing for limited control. The danger of such tests caused Santos-Dumont and his team to quickly abandon them, although some constructive information was obtained that led to adjustments in the balance and weight placement of the plane.Santos-Dumont then connected a steel cable to the tops of two tall poles, one taller than the other. The aircraft was hung by a rope and attached by a pulley to the steel cable. It was then pulled by a donkey until it rested by the taller pole, and then released and allowed to slide down the cable towards the lower pole. In this manner, the center of gravity of the aircraft was established and adjusted, and much was learned about its stability. (Photographs of these tests show the vehicle being pulled up along the cable by the donkey back to the higher position. This gives the appearance that the plane was tested while being pulled by a donkey, which is not accurate).

By August 1906, the aircraft was transported back to Bagatelle, where Santos-Dumont performed what we would today call fast-taxi tests. The engine was found not to be powerful enough to safely reach flight speeds, and was replaced by a 50 hp Antoinette, a V-8 design capable of 1,500 rpm. Early September saw greater speeds in ground tests, as well as a minor accident. On the September 7, 1906, the wheels left the ground during an extremely quick hop.Announcements were made about Santos-Dumont trying for all the aeronautics prizes. Crowds and aviation authorities gathered on the morning of the September 13, 1906. Not all the cylinders were firing during an initial takeoff attempt, but quick repairs allowed for the second run to result in a 13-meter (43-foot) hop, an altitude of about 1 meter having been reached. This did not qualify for the prizes, but earned Santos-Dumont a great deal of attention.The 14-bis landed at a high angle of attack, and the propeller at the back struck the ground. Repairs were undertaken. On the 23 October, after a series of engine tests and high-speed ground runs (one of which ended as one wheel came loose, but this was quickly fixed), Santos-Dumont finally pulled the 14-bis into the air. The aircraft flew for over 200 feet at an altitude of about 10 feet. This earned Santos-Dumont the first of the aviation prizes, 3,000 francs for a 25-meter-or-greater flight.

The plane required more repairs, as the landing had again damaged it, and Santos-Dumont announced that he should be ready to attempt the 100-meter prize on November 12. The 14-bis was repaired, and ailerons were added to the middle of each outermost wing cell (similar to the aileron layout later used in the famous Curtiss Model D Pusher). These ailerons were actuated by cables attached to the pilot's flightsuit at the shoulders. Movement of the shoulders thus actuated roll control, similarly to the hip-movement roll-actuation control on the Wright Flyer.

On the morning of November 12, 1906, the crowds gathered. In a surprise to nearly all there, Voisin also brought a biplane that he and Bleriot has built, and also powered by an Antoinette. Voisin made several takeoff attempts, until one of them damaged the vehicle such that it could not be tested further before being extensively repaired.

As Santos-Dumont allowed the 14-bis to run down the field, a car drove alongside, and Henry Farman would drop a plate out of the car each time he observed the wheels of the plane to leave the ground or to touch down again. The first attempt saw a flight of 40 meters, and the second saw two brief flights of 40 and 50 meters. A hurried landing after this second attempt (rushed due to the proximity of some trees) damaged the wheel axles, and these were fixed during a lunch break. In the afternoon, further flights were of 50 meters and then 82 meters. As the sun set, Santos-Dumont attempted one more flight. In order to ensure he would not hit spectators, who by this time were present all over the field, he flew at an altitude of 4 meters. After 22 seconds, he cut the engine power and glided into a landing. He had flown for 220 meters, or over 700 feet, qualifying for the second aviation prize offered for heavier-than-air-aircraft, 1,000 francs for a flight of 100 meters or more.

Specifications (14-bis)

General characteristics