Engineering Wonders of the World
Volume III

THEORY AND PRINCIPLES OF THE AEROPLANE. 11 The Wrights depend entirely on the front elevator for the maintenance of fore and aft stability. They have expressed the opinion that, as the cyclist must learn to balance his ’ cycle, so the aviator must learn to balance his aeroplane. At first the task is not easy, but practice brings a habit of doing the right thing without conscious calculation. That the lesson can be learnt without great difficulty—at least by persons naturally recep- tive—has been proved by events. Yet there is much to be said in favour Automatic c . Stability °* auiomatic stability systems, which tend to relieve the pilot of the strain entailed by constant watchful- ness. In fact, it is hard to conceive what one may style the successful commercial flying machine of the future as a contrivance which will be kept right way up only by virtue of the pilot’s unceasing vigilance. The Voisin, Farman, and some other bi- planes carry a horizontal immovable tail in the rear in addition to a front elevator ; while Fixed Tails monoP^anes of all patterns have a horizontal tail as well as a horizontal rudder, which, in the case of these machines, could not well be placed ahead of the main decks, owing to the position of the tractor screw. The tail checks sudden altera- tions of angle, and generally tends to keep th© aeroplane level. A rear horizontal rudder is, however, not so efficient as the front elevator, as it has little effect in checking the speed of the aeroplane when the latter alights. A front elevator is turned up somewhat abruptly just before the machine touches ground, and di- minishes the speed while flattening the angle of descent, so that a well-handled aeroplane alights without shock. The action is very similar to that of a bird throwing its head back and opposing its wings almost squarely to the air just as it reaches earth. The mono- plane, with its rear elevator, which has little braking effect, is apt to come down heavily and damage the wheeled carriage and the propeller. Thanks, however, to its tail, it has good longitudinal stability if the weight be properly distributed. At one time it was thought that Rear its stability was far inferior Elevators. to that of the biplane ; but M. Blériot, after many experiments, succeeded in overcoming the diving propensities of this type. Against the tail it may be urged that it decreases speed. The American biplane, the June Bug, originally carried a tail. When this was removed the speed was greatly in- creased. We may observe, too, that the biplanes with double-decked tails are not a speedy class. On the other hand, the mono- plane type of tail does not appear to militate against speed. Though it is as yet early to dogmatize on points relating to aeroplane design, it may be assumed that the tail increases longitudinal stability, but that the front control is ex- tremely valuable. The tailless biplane is more handy ” and easy to manoeuvre ; the tailed machine more stable, but less easily swung about. 1 fo counteract sideways tilting several sys- tems have been used. The first was to turn the two halves of a deck upwards to form a “ dihedral angle ” at the middle. This gave stability, Lateral but caused a rolling from side Stability, to side. The straight-edged deck is somewhat less stable, but is free from rolling. Decks with drooping ends have been used by Mr. Cody, those on his aeroplane having a dip of several inches towards the tips. A partridge when gliding droops its wings, but keeps re- markably steady, so that possibly the third form may prove to be the most suitable. At present the straight deck is in vogue. A very slight dihedral angle is used on the Antoinette monoplanes, as previously by Langley on his model aerodrome, and by Maxim for his big steam-driven machine.