"The natural fore and aft stability is very much strengthened by placing the load well forward. The center of gravity near the front and a tail or rudder streaming to the rear secures stability as an arrow is balanced by the head and feathering. The adoption of this principle makes it almost impossible for the aeroplane to turn over.
The Matter of Lateral Balance.
"All successful aeroplanes thus far have maintained lateral balance by the principle of changing the angle of incidence of the wings.
"Other ways of maintaining the lateral balance, suggested by observation of the flight of birds are—extending the wing tips and spilling the air through the pinions; or, what is the same thing, varying the area of the wings at their extremities.
"Extending the wing tips seems to be a simple and effective solution of the problem. The tips may be made to swing outward upon a vertical axis placed at the front edge of the main planes; or they may be hinged to the ends of the main plane so as to be elevated or depressed through suitable connections by the aviator; or they may be supported from a horizontal axis parallel with the ends of the main planes so that they may swing outward, the aviator controlling both tips through one lever so that as one tip is extended the other is retracted.
"The elastic wing pinions of a bird bend easily before the wind, permitting the gusts to glance off, but presenting always an even and efficient curvature to the steady currents of the air."
High Winds Threaten Stability.
To ensure perfect stability, without control, either human or automatic, it is asserted that the aeroplane must move faster than the wind is blowing. So long as the wind is blowing at the rate of 30 miles an hour, and the machine is traveling 40 or more, there will be little trouble as regards equilibrium so far as wind disturbance goes, provided the wind blows evenly and does not come in gusts or eddying currents. But when conditions are reversed—when the machine travels only 30 miles an hour and the wind blows at the rate of 50, look out for loss of equilibrium.
One of the main reasons for this is that high winds are rarely steady; they seldom blow for any length of time at the same speed. They are usually "gusty," the gusts being a momentary movement at a higher speed. Tornadic gusts are also formed by the meeting of two opposing currents, causing a whirling motion, which makes stability uncertain. Besides, it is not unusual for wind of high speed to suddenly change its direction without warning.
Trouble With Vertical Columns.