With all transport vehicles a light structure weight is of prime importance. Light weight vehicles require less power to accelerate, less braking to stop, less power to climb hills. The power /weight ratio broadly determines the ability of a vehicle to get out of difficulties, avoid collision and, generally speaking, settles the vehicle's performance characteristics.

This is particularly true of the aeroplane where, with a third dimension of travel, the effect of gravity is present to a degree unknown to sea or land travel, even in mountainous countries.

Weight saving thus becomes of paramount importance in aircraft design and leads inevitably to the conclusion that nothing should be carried in the aeroplane to fulfil a service which can be satisfactorily and safely performed on the ground.

A further result, and one that most concerns us here, arises from this weight factor. In many trades a great deal of the technical execution of the work in detail is carried out in accordance with the superintendent's or foreman's knowledge and craftsmanship, and whether there is a little more—or less— material used is a matter for commercial considerations of cost, rather than one of necessity to save weight in order to fulfil performance.