Upon occasion it is required to find the drag of aircraft components which are normally retracted in level flight, such as flaps and undercarriages. The usual method of obtaining this drag from flight tests, is to measure speeds in level flight under known engine conditions with the component retracted and then with the component down. The difference of speed so obtained, together with the known test conditions then yields an answer. The disadvantage of this method is that, as the difference of speed is usually large, incidence changes and airscrew and engine assumptions cause discrepancies in the results. The difference of power between different engines of a type can be ± 5 per cent. A method is proposed which will enable most of the disadvantages of the older method to be overcome.

Glass Cloth/Polyester resin laminates similar to those described by Irving and Saunders (Journal, February 1954) have been used at the University Engineering Laboratory, Cambridge, in the manufacture of blades for an axial flow compressor. In the first experiments, an existing aluminium stator blade was used as a pattern, and a mould was made by pouring molten type metal round this pattern, held in a steel sided moulding box.

A simple cumulative fatigue damage law is used to estimate the endurance of a number of typical structural components when subjected to the alternating wing loads encountered by an aircraft in flight. A method is developed to study the fatigue damage in terms of infinitesimally small intervals of alternating load and the corresponding fatigue strength. Recent gust data are used in conjunction with the complete fatigue strength diagrams of 13 simple components. The fatigue damage is studied for the ranges of altitude (i) up to 12,000 ft., and (ii) above 30,000 ft. In each case it is found that the damage rate curve, which gives the intensity of fatigue damage at any gust velocity, takes a characteristic form, with a well-defined range of gust velocities giving the greatest fatigue damage. This leads to a simplification of the whole problem, and it is found, finally, that the life of the structure is governed—in so far as the cumulative law is correct—almost entirely by that gust velocity, which, when applied alone to the structure, gives an endurance of about two million cycles. The results of the survey are compared with the design criteria suggested by Walker and the lives estimated by Williams.

The carpet and lattice methods of plotting the relationship between three and four variables respectively, developed by R. F. Sargent, of the National Physical Laboratory, have been described previously by A. H. Yates, who gave examples related to the presentation of aerodynamic and engine performance data. Outside these fields there appears to be still some lack of appreciation of the usefulness of this form of graphical representation, although it is capable of wide application. The writer has found both carpet and lattice plotting of great value in connection with the preparation of structures data sheets, and is convinced that interpolation is generally rendered easier and more accurate if graphical data are presented in this way. In one particular instance it was found possible to develop a nomogram in the form of an “ extended lattice ” plot, which gave in graphical form a direct solution to a set of equations which could be solved otherwise only by continuous approximation.

It was a great revelation to me to read Lieut.-Comdr. Graham's study of the “Safety Devices on Wings of Birds,” reprinted in the Journal of the Aeronautical Society of January, 1932. I had always believed that the gaps formed by the tip feathers on a bird's wing were not strictly comparable to slots, because from a superficial observation of birds’ wings, it appeared that the slots were running in the wrong direction, namely, from the top to the lower surface of the wing. Lieut.-Comdr. Graham's outstanding contribution is his discovery of the reason for the emargination of the web of the slot forming wing tip feathers. There can be no doubt that this arrangement is aerodynamically equivalent to a multi-slotted wing.