A certain amount of harm may be done by bomb-dropping, machine-gun fire, the raining of steel darts, etc.; but an aeroplane at a height cannot take an intimate and decisive part in a fray, as, for an example, cavalry charging, or infantry with the bayonet. It might prove of enormous and overwhelming value if at any critical moment, or at any critical point, it were possible to let loose a few squadrons of aeroplanes each mounting one or more machine guns, to bring short-range concentrated fire to bear, or alternatively to make an attack by the aid of bombs or hand-grenades. The scene that would ensue, for example, on a congested line of retreat would be indescribable: horses thrown into hopeless confusion or stampeded, mechanical transport lorries holed in a dozen or more vital points, water-jackets or radiators damaged, cylinders pierced, etc., gun teams wiped out, infantry decimated; in brief, chaos over endless miles of high road.
§ 14. Armour for Low-Altitude and Point Blank Range. The question arises whether it is possible for the aeroplane to fly at a sufficiently low altitude to act effectively in the manner indicated without exposing itself to immediate destruction. The matter is entirely a question of armour; the unarmoured portions of the machine, which derive their immunity from their transparency to rifle-fire, are no worse off at point-blank range than at 2000 ft, or 3000 ft, altitude. Taking the altitude as 500 ft. (a reasonable maximum for the effective execution of the duties contemplated), the thickness of armour necessary is approximately 5⁄32 in. (4 mm.) for the British service Mark VI. ammunition, or slightly over ¼ in, in the case of the pointed Mauser bullet, the latter thickness representing a weight of 10 lb, per sq. ft. It is evident that the problem of giving complete protection to the motor, pilot, and gunner will become a
31
