Curtiss 80-Horsepower Motor and Tractor Screw Mounted on Langley Aeroplane.
Smithsonian Report, 1914.—Zahm.
Plate 4.
Elwood Doherty Clearing the Water September 17, 1914, in the Langley Aeroplane Driven by a Curtiss 80-Horsepower Motor and Tractor Screw.
In the accompanying illustrations, [plates 1] and [2] show the appearance of the Langley flying machine after Mr. Curtiss had provided it with hydroaeroplane floats and their connecting truss work. The steel main frame, the wings, the rudders, the engine and propellers all were substantially as they had been in 1903. The pilot had the same seat under the main frame, and the same general system of control as in 1903. He could raise or lower the craft by moving the big rear rudder up and down; he could steer right and left by turning the vertical rudder. He had no ailerons nor wing-warping mechanism, but for lateral balance depended upon the dihedral angle of the wings and upon suitable movements of his weight or of the vertical rudder. And here it may be noted that Langley had placed the vertical steering rudder under and to the rear of the center of gravity. So placed, it served as a fairly good aileron by exerting a turning movement about the longitudinal axis of the machine.
After the adjustments for actual flight had been made in the Curtiss factory, according to the minute descriptions contained in the Langley Memoir on Mechanical Flight, the aeroplane was taken to the shore of Lake Keuka, beside the Curtiss hangars, and assembled for launching. On a clear morning (May 28), and in a mild breeze, the craft was lifted onto the water by a dozen men and set going, with Mr. Curtiss at the steering wheel, ensconced in the little boat-shaped car under the forward part of the frame. Many eager witnesses and camera men were at hand, on shore and in boats. The four-winged craft, pointed somewhat across the wind, went skimming over the wavelets, then automatically headed into the wind, rose in level poise, soared gracefully for 150 feet, and landed softly on the water near the shore. Mr. Curtiss asserted that he could have flown farther, but, being unused to the machine, imagined the left wings had more resistance than the right. The truth is that the aeroplane was perfectly balanced in wing resistance, but turned on the water like a weather vane owing to the lateral pressure on its big rear rudder. Hence in future experiments this rudder was made turnable about a vertical axis, as well as about the horizontal axis used by Langley. Henceforth the little vertical rudder under the frame was kept fixed and inactive.
After a few more flights with the Langley aeroplane, kept as nearly as possible in its original condition, its engine and twin propellers were replaced by a Curtiss 80-horse motor and direct-connected tractor propeller mounted on the steel frame, well forward, as shown in the photographs. It was hoped in this way to spare the original engine and propeller bearings, which were none too strong for the unusual burden added by the floats. In 1903 the total weight of pilot and machine had been 830 pounds; with the floats lately added it was 1,170 pounds; with the Curtiss motor and all ready for flight it was 1,520 pounds. But notwithstanding these surplus additions of 40 per cent and 85 per cent above the original weight of the craft, the delicate wing spars and ribs were not broken, nor was any part of the machine excessively overstrained.
Owing to the pressure of other work at the factory, the aeroplane equipped with the Curtiss motor was not ready for further flights till September. In the absence of Mr. Curtiss, who had gone to California in August, a pupil of his aviation school, Mr. Elwood Doherty, volunteered to act as pilot.