CHAPTER VI.
THE AIRPLANE RADIO TELEPHONE.
Electrical science was called upon to furnish marvels and prodigies indeed during the recent war as aids to the American arms, but in no respect did it respond in more successful and spectacular fashion than it did when asked to produce a wireless telephone system that would make possible the transmission of human speech to and from moving airplanes. It is doubtful if any other branch of science enlisted for war work produced any instrument or mechanism so far in advance of what was known before the war as the airplane wireless phone was in its class.
To be sure, we had the radio telephone some time before America entered the war or even before the war broke out in Europe in 1914. Ever since the scientists began experimenting with wireless electricity it has been axiomatic that, at least theoretically, whatever you can do with wires you can do without wires. And so following the development of the wireless telegraph came the production of the wireless telephone, and the invention had been so perfected in 1915 and 1916 that in the United States Navy's official test at the Arlington Station, across the Potomac River from Washington, human speech sent out by the transmitters there was heard simultaneously at the Eiffel Tower in Paris and at the Government's own wireless station in Hawaii.
But there is a vast difference between using the wireless telephone in the quiet of the radio rooms aboard ship or in the shore stations and using it amid the roar of the powerful engine propelling an airplane. The equipment, too, that had been used on the ground was altogether too cumbersome to go into the fuselage of an airplane.
As early as August, 1910, American genius had successfully accomplished wireless telegraph transmission from airplane to ground, and in October of the same year the idea of aerial fleet command by telephone was conceived and plans for its development discussed by Army officers on duty at the International Aviation Tournament at Belmont Park, Long Island. In 1911 a message was successfully transmitted from an Army airplane over a distance of 2 miles. In 1912 the Signal Corps had increased the distance to 50 miles. Two years later, in the Philippine Islands, a message had been successfully received on an airplane in flight over a distance of 6 miles.
In 1915 the Aviation Section entered upon a definite plan of development of aircraft wireless at the Signal Corps Aviation School, San Diego, Calif. This plan was based upon the Belmont Park idea and discussions, with the voice-commanded tactical air fleet as the ultimate goal. The airplane had changed from the pusher to the tractor type, with the noise of the motor of the latter driven back by the blast of the propeller into the face of the aviator. The airplane wireless problem was thus quite completely changed. Under these new conditions, however, the development was entered upon, and it has since been continuous. In October a spring-driven dictaphone was taken into the air and a record of speech made in the noise of the motor. This was contemporaneous with the successful long-range experiments in radio telephony at Arlington, referred to above. A study of this dictaphone record convinced the aviation officers that the idea of the radio telephone for airplanes was entirely practicable. Experiments during the fall and winter with various means of driving the wireless power plant resulted in a decision to develop the air fan as a source of power rather than the gear or belt system.
This development continuing through 1916, transmission by telegraph from airplane was accomplished up to 140 miles, means for receiving in the noise of the motor were worked out, and a message successfully telegraphed between airplanes in flight. The radio telephone was under construction, and in February, 1917, the voice was first transmitted by telephone from airplane to ground. Like Alexander Graham Bell's first wire telephone, the apparatus was crude. But the door was unlocked and ready to be opened upon the new field of development.