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18 FLY MAGAZINE April 1913

"In the specification the surfaces of the planes are described as 'normally substantially flat' and in the claims they are referred to as 'normally flat,' and it is stated that when the supporting surfaces are made of cloth or other flexible fabric a curvature is imparted to the planes by the resistance of the air. But the patentees did not limit themselves to the precise details of construction, and they stated in their specification that the same might be modified without departing from the principle of invention. The patentees evidently believed that the curved surfaces would be made normally flat in view of the flexibility of the material originally used by them, and that to their surfaces there would be imparted a curvature by air pressure. They were required by law merely to state the best manner known to them of embodying their invention in a complete practical structure, and were not limited to the specific form, or to the best form known to them, if their claims were broad enough to entitle them to equivalents. . . .
"The defendants assert that curved surfaces impart lifting advantages to the planes and also increase the stability of the planes and that the patentees purposely refrained from disclosing the best form of their apparatus intending by a faulty description to mislead the public. In answer, however, it suffices that the evidence does not support any such view.
"To the aeroplane later constructed by the complainant there has been added a supplemental lever for turning the vertical rudder, which, as shown by the evidence, is used to increase the swing of the machine in one direction or another when the conditions are such as to necessitate turning the rudder further to the right or left to retard the speed of the right or left wings than can be done by using the cradle. This alteration or additional feature was not necessary to the practicability or operativeness of the invention, such rudder still being relied upon in connection with the warping instrumentality.
"Defendants further contend that the patient is silent regarding the use of a motor and that therefore it was never intended to pass beyond the gliding machine stage, but this is incorrect as the specification expressly alludes to flying either by the application of mechanical power or gravity. Moreover, the use of motors in aerial machinery was not a new idea, and was never regarded as a knotty problem.
"There was much discussion at the bar as to claim 3, which does not include the vertical rudder as an element. The important feature thereof is that the lateral marginal portions of the planes must be capable of movement to different angles relatively to the normal plane of the aeroplane and about an axis transverse to the line of flight, the purpose of said movements being to present to the atmosphere different angles of incidence. It was argued that without the co-operation of the vertical rudder the claim was wholly impracticable. The complainant company, to the contrary, rejoins that there is shown a sub-combination which is valid and which should be sustained. There is evidence that the marginal ends of the supporting planes are capable of moving simultaneously in different angular relations to the plane and to each other without the assistance of the vertical rudder, but the result was not satisfactory as the machine in its flights skidded to the side, an imperfection which has been remedied by the used of the vertical rudder in conjunction with the ailerons. It is not essential to the validity of claim 3 that all parts of the machine, or all parts specified in other claims, which are necessary to its operativeness should be included therein, and resort must be had to the specification for a disclosure of the parts necessary to insure the practicability of a patended device.
"In the Wright structure a new and novel result was attained simply by having the ailerons on the ends of the planes without the supplemental feature of the vertical rudder. The warping feature is, in fact, the essential part of the machine while the vertical rudder insuring successful flying is a valuable adjunct without which lateral balance could not be restored. The employment, in a changed form, of the warping feature or its equivalent by another, even though better effects or results are obtained, does not avoid infringement. In such circumstances, as I read the authorities, the claim is valid as a combination. . . .
"It is next contended that defendants' aeroplane does not infringe claim 3, as its ailerons do not move in either direction above or below the normal plane of the body portions, but any such alteration, however, is immaterial, as defendants' planes move at different angles relative to the aeroplane and to each other and attain the substantial result of the Wright patent.
"Claim 7 is for the elements of (1) an aeroplane, (2) means for moving the ailerons in different directions, (3) a vertical rudder, and (4) means for operating the rudder, causing it to 'present to the wind that side thereof nearest the side of the aeroplane having the smaller angle of incidence and offering the least resistance to the atmosphere, substantially as described.' The description of the modus operandi of the rear rudder plainly discloses its object and purpose and is not restricted to the warping ropes or wires. Claim 14 includes the horizontal rudder with means for presenting its under side to the resistance of the air currents, while claim 15 specifies the location on the aeroplane of the vertical and horizontal rudders. . . .
"This brings me to the final question of whether or not there is in defendants' machine a tendency to spin or swerve which is checked or counteracted by the operation of its vertical rudder. Upon this phase of the case considerable oral testimony was given bearing upon the practical and theoretical sides. Notwithstanding the construction to which the claims are thought entitled, if the defendants operated their aeroplane upon a different principle, using means which were old in aerial navigation or foreign to complainant's, then infringement cannot be sustained. . . .
"The testimony of witnesses who have flown the defendants' aeroplane and swear that the rear rudder is not in fact used for recovering lateral balance, but that such function is performed solely by the ailerons, would ordinarily be entitled to greater weight than the opinions of experts or the contradictory testimony of witnesses who ere on the ground or in other flying machines observing the movements of the defendants' machine, or than the statements made by other in relation to the manner in which such machine should be or had been operated, and would in this case, were it not that there is cogent evidence tending to modify or qualify their denials of the use of the vertical rudder except for steering. Willard concedes that the rear rudder is turned to the high side to gain additional restoring power; that is is used as 'a separate agent to accomplish a desired result more quickly or more positively.' In the Curtiss letter in evidence it is substantially admitted that the rear rudder is turned toward the high side at times to assist in balancing the machine by steering or turning. . . . 
"it is true that none of the claims specifically state that the vertical rudder should be turned to the high side to recover the balance of the machine or to keep it balanced, yet in claim 7, 14, and 15 means are included for moving it to the side of least resistance which the evidence shows was the
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