The manoeuvres of getting off and landing are to me the beginning and the send of flight; they separate the sheep from the goats; the aristocrat of the flying world uses them for the display of his genius, leaving his would-be imitators to find what consolation they can in the amusement with which they innocently provide the onlookers.

In commercial flying the manoeuvres of getting off and landing are still the most obvious calls on the pilot's skill; and who shall deny the splendid response? But a determination to ease the pilot's task is not thereby for an instant to be excused. This, one of the most urgent problems before applied design to-day, lies in the conflicting requirements of ease and safety in getting off and landing and those of economy and usefulness in full flight. To assist in the statement of this problem is the object of my Paper. These are the manoeuvres perhaps about which most has been said, and, from the pilot's point of view, least written. Since first a heavier-than-air machine left the ground, they have never failed as a topic of conversation throughout the whole flying community; and this has tempted me to analyse them on the basis of my own experience and that of the many pilots I have known.

In a recent article in “ Engineering ” the writer has given an account of the principles which govern the design of aeroplane control surfaces, making special reference to wing ailerons. Included in the information presented were data on the properties of wing ailerons of the ordinary unbalanced form, but varying in span and chord length and fitted to wing tips of different plan forms. From these data several conclusions of practical importance were drawn, some of them finding general application in the design of control surfaces, and it may be useful to give a résumé of these before proceeding to deal with the balancing of control surfaces.

(i) All ailerons and elevators become relatively inefficient for movements above about 15° to 20° from the normal position, owing to a sudden reduction in the slope of the curve relating moment on machine with angle of aileron or elevator. For movements up to about 15° or 20° the moment is nearly proportional to the angle.

It has been suggested that strut fittings could be made neater, on a staggered aeroplane, if the spar web were given the same stagger. Then the principal axes of the section are not in the direction of either the loading or the supports. The result may be an increase of both bending and shear stress; not more than it is possible to provide for, but involving an increase of weight likely to be more than the gain in the fitting.