Stability of Aeroplanes. Offprint from: The Journal of the Franklin Institute, September, 1914.

[Philadelphia]: J.B. Lippincott, 1914.

First edition, rare offprint issue, and Orville Wright’s own copy, of his discussion of longitudinal equilibrium in aircraft, or how to keep the stability of aeroplanes. “Although in learning to fly the beginner finds most difficulty in mastering the lateral control, it is his lack of knowledge of certain features of the fore-and-aft equilibrium that leads to most of the serious accidents” (from the introduction). The Wright brothers were early on aware of the importance of longitudinal control. Most of the early airplanes – the ones that could actually lift off ground – had the decisive flaw of having bad, in some cases non-existing, longitudinal control which eventually caused the airplanes to crash. In the summer of 1910, the Wright Company introduced what would become their most popular aircraft – the Wright Model B. The Model B was a pusher biplane with wing warping to control roll, like their earlier aircraft. But unlike earlier aircrafts it also had a conventional tail assembly, which gave it better longitudinal stability, and it rested on wheels rather than skids, doing away with the need to launch the aircraft from a rail. This model was produced from 1910 through 1914. In 1911 the U.S. Congress made its first appropriation for military aviation. Four airplanes were ordered and numbers 3 and 4 were Wright Model Bs. Both were accepted at Fort Sam Houston, Texas on April 17, 1911.The two brothers were also investigating automatic stability systems. They devised a mechanism that could sense changes in attitude and longitude which would make compensating adjustments to keep the aircraft flying evenly in the desired direction. It consisted of a pendulum, which sensed and controlled roll or yaw, and a vane, which sensed the aircraft’s pitch. They applied for a patent for this automatic stabilizing system on February 8, 1908.

Provenance: Orville Wright (with stamp signed by co-executor Harold S. Miller).

By 1905 the Wrights had developed a practical airplane that for the first time could be controlled by a pilot. Having achieved that goal, they decided to develop an automatic stabilizer that could fly the airplane straight without a pilot’s intervention. They were successful in their effort and were awarded the prestigious Collier Trophy by the Aero Club of America for their device on January 5, 1914. The prize recognized the most significant contribution to aeronautics made during the year of 1913 …

“The Wrights began their work on the device in secrecy sometime after 1905. Their concept was to develop an adaptive system with feedback. A change in direction of heading, automatically applies power to adjust the airplane controls in yaw, roll and pitch as appropriate, and brings the airplane back to its original heading. The 30-pound device consisted of a pendulum and vertical vane that were connected to a power source which drove servomotors. Whenever the pendulum swung out of vertical the wing warping control was activated to restore yaw and roll balance. Similarly the horizontal vane sensed pitch stability and activated the elevator control. The original power source was compressed air, then it was replaced with a battery, and in the final version, a small windmill set in motion by wind was used. The pilot could adjust the vane at any angle desired for use in climbing or descending. It could also be switched on or off by the pilot as desired.

“They applied for a patent on February 8, 1908 although the device was still in development and not been flight tested yet because of desire to maintain secrecy. The Wrights worked on the device intermittently, as time would allow. In the fall of 1911 they had progressed to the point where they decided to test it out on a new glider at Kitty Hawk. However a number of reporters also showed up, so in order to maintain secrecy on the new device, they flew the glider without using the automatic control feature. Their patent (#1,075,555) was granted October 14, 1913 although they still had not flight-tested it.

“The Wrights didn’t seem to be in any hurry in using the device until Glenn Curtiss had won the Collier Trophy two years in a row during 1911 and 1912. Curtiss had won the trophy for his development of flying boats. Orville decided Curtiss wasn’t going to win again in 1913. He decided he would use the Automatic Stabilizer to win the prize with. In the fall of 1913, Orville installed the stabilizer on a special Wright Model E airplane that utilized a single pusher propeller. He kept the details of the stabilizer secret even from the Wright Company. He purposely waited until the last day of the year to fly for the prize.

“He invited the Aero Club’s judges to Huffman Prairie to see a demonstration of his new device on a cold snowy day, December 31st. He turned up his coat collar, put on a pair of goggles and took off. He made a total of 17 flights. His most spectacular flight consisted of 7 full circles of the field with both hands held in the air. The automatic stabilizer kept the same angle of bank and almost the same altitude. He wowed the judges and was awarded the prize on February 5, 1914” (

8vo (231 x 151 mm), pp. 4. Original grey printed wrappers, a very fine copy. Preserved in a half-leather clamshell box, gilt-stamped title on spine.

Item #5648

Price: $2,000.00

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