designed that bullets will pass through without doing more than local injury and without serious effect on the whole; in certain cases components will require to be duplicated in order to realise this intention. It is important to under stand clearly that any intermediate course is fatal Either the bullet must be definitely resisted and stopped, or it must be et through with the least possible resist- ance; it is for the designer to decide in respect of eaclh component which policy he will adopt. The thickness of required will depend very much upon the minimum altitude at which, in the presence of the enemy, it is desired to fly; also upou the particular type of rifle to bear There is a great deal of difference in penetrative power, for example, between the round-nosed and pointed bullets used in an otherwise strength flying power of the machine as a or the armour and ammunition brought identical cartridge.
If it were not for the consideration of the weight of no doubt that an altitude of about armour, there is 1000 ft. would be found very well suited to most of the ordinary tactical duties of the aeroplane. At such an altitude, however, the thickness of steel plate necessary becomes too serious an item for the present-day machine, allowing for the very excellent and highly efficient bullet-proof treated steel which is now altitude in question the minimum thickness that will stop a 0.303 Mark VI. round-nose bullet is 3 mm. ( in.), but if attacked by the modern pointed-nose Mauser, nothing even available; at the short of 5 mm. or 6 mm. is of avail. If we compromise somewhat in the matter of altitude and prescribe 2000 ft the minimum height for which protection is to be given, the figures become 2 mm for the 0.303 round-nosed bullet, and for the pointed as (about 14 S.W. gauge) Mauser 3 mm slightly over; at present it is not machine for the or
expected that it will pay to armour a