By adopting this twin-motor form we bring in new disadvantages. One of these is due to the fact that the heavy motors are now located some distance from the center of gravity of the machine. This requires stronger supporting members between the motor and the body. It also makes the lateral control comparatively logy for now the heavy masses are far from the center of gravity, resisting the pilot’s efforts to use the lateral control. The second disadvantage in the twin-motor type results from possible stoppage of either motor. In this case, of course, the propelling force is some distance off center and is also reduced to one-half its value requiring energetic exercise of the control wheel to maintain equilibrium. It is reported, however, that twin machines can continue to fly and even climb with only one motor running. In this country the twin-motor type has not developed as was hoped at first, and on the European firing lines it is not so numerous as the single-motor tractor type.
Marine Airplanes.—The possibility of mechanical flight having once been established and wheels having been applied to the airplane so that it could start from and land on the ground, the logical next step was to substitute some form of boat for the wheels so that flights could be made over the water.
Experiments were made in France by M. Fabre in this direction and in this country by G. H. Curtiss. The latter, in his flight down the Hudson from Albany to New York, equipped his airplane with a light float to provide against forced landing in the river. Pursuing this general idea he made some experiments under the auspices of Alexander Graham Bell’s Aerial Experiment Association, in which a canoe was substituted for the wheels, and in which an attempt was made to start from the surface of the water. Success did not come at first and this plan gave no satisfaction. Curtiss next turned his attention to the hydroplane type of boat and made a series of experiments at San Diego. The hydroplane appeared to be much better adapted to his purpose than the canoe had been, and he was able to obtain success.
Fig. 12.—Thomas Type H. S. seaplane. Double pontoons.
Speed 47 to 82 mi. per hr.; climbing ability 270 ft. per min.; 135 h.p.; weight, fully loaded 2,600 lbs.
Fig. 13.—Curtiss Model F flying boat.
Speed 45 to 65 mi. per hr.; climbing ability 150 ft. per min.; 90 h.p.; weight fully loaded 2,100 lbs.
The Hydro-airplane (or “Seaplane”).—From analogy to the airplane one might at first imagine that a suitable hydroplane would have a wide span and fore and aft length; but such proportion would give a very poor stability on the water, and would require auxiliary hydroplanes in the same way that an airplane requires auxiliary guiding surfaces. So Curtiss, with his customary eye for simplicity and convenience, adopted a type of hydroplane which had the general proportions of an ordinary boat, i.e., was long and narrow, thus obviating the necessity of auxiliary hydroplanes at the tail of the machine. To prevent the machine’s tipping over sidewise, “wing pontoons” were attached at the lower wing tips to prevent capsizing.