The First Flight: December 17, 1903
Kitty Hawk, North Carolina
by Orville Wright
“The flights of the 1902 glider had demonstrated the efficiency of our system for maintaining equilibrium, and also the accuracy of the laboratory work upon which the design of the glider was based. We then felt that we were prepared to calculate in advance the performance of machines with a degree of accuracy that had never been possible with the data and tables possessed by our predecessors. Before leaving camp in 1902 we were already at work on the general design of a new machine which we proposed to propel with a motor.
Immediately upon our return to Dayton, we wrote to a number of automobile and motor builders, stating the purpose for which we desired a motor, and asking whether they could furnish one that would develop eight-brake horsepower, with a weight complete not exceeding 200 pounds. Most of the companies answered that they were too busy with their regular business to undertake the building of such a motor for us; but one company replied that they had motors rated at 8 h.p. according to the French system of ratings, which weighed only 135 pounds, and that if we thought this motor would develop enough power for our purpose, they would be glad to sell us one. After an examination of the particulars of this motor, from which we learned that it had but a single cylinder of 4-inch bore and 5-inch stroke, we were afraid that it was much overrated. Unless the motor would develop a full 8 brake horsepower, it would be useless for our purpose.
Finally, we decided to undertake the building of the motor ourselves. We estimated that we could make one of four cylinders with a 4-inch bore and 4-inch stroke, weighing not over two hundred pounds including all accessories. Our only experience up to that time in the building of gasoline motors had been in the construction of an air-cooled motor, 5-inch bore, and 7-inch stroke, which was used to run the machinery of our small workshop. To be certain that four cylinders of the size we had adopted (4″ x 4″) would develop the necessary 8 horsepower, we first fitted them into a temporary frame of simple and cheap construction. In just six weeks from the time the design was started, we had the motor on the block testing its power. The ability to do this so quickly was largely due to the enthusiastic and efficient services of Mr. C.E. Taylor, who did all the machine work in our shop for the first as well as the succeeding experimental machines. There was no provision for lubricating either cylinders or bearings while this motor was running. For that reason, it was not possible to run it more than a minute or two at a time. In these short tests, the motor developed about nine horsepower. We were then satisfied that, with proper lubrication and better adjustments, a little more power could be expected. The completion of the motor according to drawing was, therefore, proceeded with at once.
While Mr. Taylor was engaged with this work, Wilbur and I were busy in completing the design of the machine itself. The preliminary tests of the motor having convinced us that more than 8 horsepower would be secured, we felt free to add enough weight to build a more substantial machine than we had originally contemplated.
Our tables of air pressures and our experience in flying with the 1902 glider enabled us, we thought, to calculate exactly the thrust necessary to sustain the machine in flight. But to design a propeller that would give this thrust with the power we had at our command, was a matter we had not as yet seriously considered. No data on air propellers was available, but we had always understood that it was not a difficult matter to secure an efficiency of 50% with marine propellers. All that would be necessary would be to learn the theory of the operation of marine propellers from books on marine engineering, and then substitute air pressures for water pressures. Accordingly, we secured several such books from the Dayton Public Library. Much to our surprise, all the formulae on propellers contained in these books were of an empirical nature. There was no way of adapting them to calculations of aerial propellers. As we could afford neither the time nor expense of a long series of experiments to find by trial a propeller suitable for our machine, we decided to rely more on theory than was the practice with marine engineers.”