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Developing the Aileron

Explorer A

(Photo by Steve Wiggins) Many people are familiar with the large flaps on airplane wings and their role in producing lift/drag.  But have you ever noticed the smaller hinged sections on the outboard part of the wings?  These are ailerons (French for “little wings”), and they are an important part of the modern airplane—albeit relatively unknown to the general population.  

Practical Significance

  Ailerons work in opposition to bank an aircraft.  For example, the right aileron may deflect upward and the left downward in order to cause a flight path to curve.  Yes, contrary to popular belief, ailerons are largely responsible for turns—NOT rudders.  The function of a rudder is primarily to control the position of an aircraft’s nose, but I digress. . . Lift force (F) generated by ailerons is applied at the aerodynamic center of the aircraft some distance (L) from its center of gravity to create a torque defined as Torque = F × L about the plane’s center of gravity.  Equal forces/distances result in a lack of net torque and unequal forces result in net torque rotating an aircraft about its center of gravity.  All of this is good and well, but how did the aileron come to be?  The answer begins with a particularly astute English gentleman!  

Historical Background

  2 While there are still conflicting claims over who first invented the aileron, some aspects of its history are irrefutable.  Matthew Piers Watt Boulton patented a revolutionary lateral flight control system all the way back in 1868, but it was soon forgotten with practical aircraft still years away.  In the mid to late 1800s, visionaries such as John Montgomery, Clement Ader, and Hugo Mattullath suggested a form of “wing warping” to control flight and applied the concept to kites with some success. However, it was Wilbur and Orville Wright who combined wing warping with a rudder to counteract differential drag and achieve coordinated turns!  With their radical combination of technologies and a forward-thinking patent including lateral control by mechanical means, the Wrights set in motion a new school of thought that French experimenter Robert Esnault-Pelterie subsequently expanded. Esnault-Pelterie bridged the gap between wing warping and ailerons.  He was concerned by the “excessive strains on the wiring” caused by wing warping designs of the Wrights, as explained in a January 1905 talk before the Aéro-Club de France.  To alleviate the problem, Esnault-Pelterie’s original design featured two surfaces—deus gouvernails horizontaux (horizontal rudders)—placed between the wings, ahead of the leading edge. 3 The editor of L’Aérophile, a French aviation magazine described as the leading aeronautical journal of the world around 1910, pioneered the use of the word “aileron” in July of 1908.  Soon thereafter, Henri Farman—inspired in the aftermath of Wilbur Wright’s flying demonstrations at LeMans in August of 1908—implemented the first recognizable modern aileron on his Farman III biplane!  Farman was the first to make ailerons an integral part of the wing, with four flap-like ailerons at the outboard trailing edges of each set of wings.   Ailerons in use on contemporary airplanes echo those of times past, and it is important to consider the work of those early aviators that has allowed for such maneuverability in the present.  Are you curious about another feature of our airplanes?  Let us know in the comments below, and we’ll be sure to get the full scoop for you!