The official document reproduced below, although in the nature of things destined soon to be out–of–date, is placed on record here, not because in a year or two it may read like Chaucer (to adapt Colonel Sykes’ happy expression, when speaking of the instructions issued in 1910, at the meeting of the 4th February), but because it is the first published attempt at official standardising of aircraft requirements. It is not proposed to subject it here to any detailed criticism, but it may be pointed out that the “minimum factor of safety of 6,” which is required, is not a factor of safety at all of anything like 6 in the ordinary engineering sense, but merely denotes the margin between the minimum and maximum stresses which are anticipated.