Abstract: The paper is concerned with some principles to carry out“Military Specification of Airplane Strength and Rigidity”.The items of the specification must not be copied indiscriminately and seriousness must be upheld on which more emphasis should be put especially at the moment.The importance of establishing project specification is pointed out through prac- tice It is important to understand properly and implement the stipulations about weight and the position of gravity centre.

Key words: structural design criteria, aircraft design, weight(mass), center of gravity