Natural Stability and the Parachute Principle in Aeroplanes

The S & C Series No. 39 NATURAL STABILITY IN AEROPLANES W. LeMAITRE 1 s 6 d Net
NATURAL STABILITY
BY W. LeMAITRE Hon. Sec., Aeroplanes Building and Flying Safety
WITH 34 ILLUSTRATIONS
LONDON E. & F. N. SPON, Ltd., 57 HAYMARKET
New York SPON & CHAMBERLAIN, 123 LIBERTY STREET
1911
Since there is nothing new under the sun, it is useless to pretend that there is anything new in the design here advocated or the theories advanced. Both are rather the result of a commonsense consideration of the different points of all flying machines, natural and artificial, and an endeavour to select from the great number of good points those which seem most likely to blend together into a practical machine. The conclusions reached are the result of a quite independent investigation, carried on over three years by means of numberless experiments, and the writer has endeavoured to make no single statement which he cannot by some experiment amply prove.

NATURAL STABILITY IN AEROPLANES
In considering the whole question of aviation, it becomes evident that the one point to strive for at the present juncture is stability. If we are ever to have a practical flying machine, that is, a machine which we can use as we do a yacht, a motor car, or a bicycle, it must be one that we can trust to keep its balance by reason of the natural forces embodied in it, and without any effort of control on the part of the pilot. It may be objected that a bicycle does not do this, and this is true, but, on the other hand, the upsetting of a bicycle is a very small matter, whereas the tilting of an aeroplane mostly means sudden death to its occupant, and it is probable that if the same consequences followed the tilting of a bicycle, bicycles would soon have been made with four wheels.
At present aeroplanes are the most unstable of all things. The least gust, the least shifting of weight, the slightest difference in the density of the strata of the supporting air, and the machine sways, and if not instantly corrected by the pilot the sway becomes a tilt, the tilt a dive, and the rest is silence. The first aeroplanes, the Wrights’ for instance, were so unstable that twenty minutes in one of them was as much as the most iron-nerved man could stand, the continual strain being too exhausting to keep up for any length of time. By throwing out extensions and outriggers in all directions we have altered that to a certain extent, but only to an extent—we have not yet got rid of it. The monoplane is probably the most unstable, as might be expected from its smaller surface, but the bi-plane runs it pretty closely.