The title of this paper is the result of practical experience in the maintenance of aircraft, combined with a view to trying to improve the design standard in future aircraft. In the past, engineers, especially aircraft engineers, have put up with a considerable amount of poor maintenance design and have gone on improvising time and time again as the only solution to their problems. As a result of this improvisation it is probable that those concerned with the actual design do not realise many of the difficulties experienced in the maintenance of their aerodynamically efficient aircraft.