But neither in connection with the exhibit of the Langley plane nor in any report of the Smithsonian Institution was there any hint of the fundamental changes made at Hammondsport, without which the plane could not possibly have carried its weight. One of these changes had to do with the supporting posts on the wings. Professor Langley had not known--indeed, no one knew until the Wrights’ wind-tunnel experiments established the facts--where the center of the air pressure would be on a curved surface, and consequently he had failed to place his wing-trussing posts where they were most needed. In the attempts to fly the machine over the Potomac, in 1903, the wing that bore the greater part of the weight had each time collapsed at the moment the apparatus left the starting platform. (Lacking the knowledge about curved surfaces that later was available, those in charge of the 1903 trials had blamed the trouble on the launching apparatus.) At the Hammondsport tests, the trussing posts were moved thirty inches rearward. This brought the guy posts almost exactly in the same plane with the center of pressure on the wings and thus eliminated the backward pull that had wrecked the machine in the 1903 tests. Three fundamental changes were made in the design of the wings themselves: (1) The camber was greatly changed; (2) the shape of the leading edge was entirely different; (3) the aspect ratio--the ratio of span to chord--was increased. These three features are the most important characteristics in determining the efficiency of a wing. The change of the camber of itself may increase the efficiency of a wing by thirty per cent. And not only were the wings changed as to design, but they were strengthened by various means of reinforcing and trussing not used by Langley. Even the cloth on the wings was improved by varnishing, to make the wings more efficient. Langley had not used varnish on the cloth. Numerous changes were made in other parts of the machine. The large fixed vertical keel surface, situated below the main frame in 1903, was entirely omitted in 1914. This omission improved the machine’s stability. A different kind of rudder was used. The position of the “Pénaud tail” used by Langley was raised about ten inches to increase the stability of the machine, and was connected to a modern steering post, to give better control. The forward corners of the original Langley propellers were cut off in the manner of the early Wright propellers to increase their efficiency. As the system of control Langley had used was not adequate, the aileron system, covered by Wright patents, a system unknown to Langley, was added.