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AN attempt is made here to summarize the present state of the theory of wind tunnel wall interference in a form that will be of some value to those using wind tunnels. The type of wind tunnel work frequently carried out without a complete knowledge of the corrections is also mentioned as it is of interest to those asking for, and using, wind tunnel results. A list of the most useful published reports on the subject is given at the end of the article, it is, however, by no means a complete guide to the literature of the subject, much of which is contained in academic volumes not usually available to the engineer using a wind tunnel.

THE Fourth International Congress for Applied Mechanics was held this year at Cambridge from July 3rd to July 9th, under the Presidency of Professor C. E. Inglis, O.B.E., F.R.S. At a conversazione at the Engineering Laboratory, by invitation of Professor Inglis and the staff of the University Engineering Department, members of the Congress were enabled to exhibit their own apparatus. A visit to the Cavendish Laboratory was also arranged for those especially interested in Atomic Physics.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodies as issued

THIS report gives a general solution of the problem of the calculation of the Glauert loading of wings with discontinuities of incidence. The three existing variations of the original theory, the Glauert solution, the Gates' least squares solution, and the Lotz' solution, are not entirely satisfactory and may involve a considerable amount of labour. The present solution divides the Fourier series representing the circulation into two parts: (a) a standard solution representing the discontinuities, which includes the slowly convergent part of the solution, and which is expressible as a precise infinite series dependent only upon the position of discontinuities along the span, and (b) a secondary solution due to plan form, aspect ratio, slope of section lift curve, and so on, which is the quickly convergent part of the solution and usually requires a terminated scries of only from four to six terms. Once the standard solution has been computed, the remaining work is little more than for the standard Glauert solution for a flat wing.

Calculations have been carried out on two elliptic wings, with ratios of major to minor axis 2·5 and 5 to 1 respectively, in order to demonstrate the use of vortex lattice theory in calculating lr and nr by lifting plane theory for wings of arbitrary plan form. Special tables of downwash, required in order to allow for the curvature of the wake, are included, and the origin of the formulae by which these are derived in a form applicable to linear theory is fully described. For the first wing, the calculated results for lr and nr and for local aerodynamic centre, load coefficients, and local lift coefficients are given for the Glauert‐Wieselsberger lifting line solution as well as for lifting plane solutions with three, six and nine control points respectively. The main work on the second wing is concerned with a six‐point lifting plane solution. The results show that there is not a serious difference between lifting line and lifting plane theory, excepting that the former does not give reliable values for the local a.c. For straight wings the six‐point lifting plane solution gives excellent accuracy. The method is applicable to wings of arbitrary plan, but the field of sweptback wings is unexplored and it should not be assumed without check that the relation of accuracy to number of control points is always the same. A further investigation is also required on the formula for nr when sweepback is present. The calculated value of lr for the 5 to 1 elliptic wing is in close agreement with the measured value for this wing obtained by Wieselsberger on a whirling arm. The report is concerned mainly with the calculation of spanwise load grading and local aerodynamic centre, and extension to detailed pressure distribution may require the use of more variables.

IN a series of articles entitled “Tailless Aircraft and Flying Wings”, concluded last month, the evolution of the tailless aeroplane and the flying wing was treated. The different trends of the development were classified, and a short discussion of the difficulties which had been experienced during experimental work given.

The following series of articles presents a new geometrical system of determining the lateral stability of aeroplanes. The method is intended to appeal particularly to engineers on account of two advantages: it is simple and rapid in operation, and gives a clear insight into the several factors governing the stability. Thus, whereas in the classical method stability calculations entail the drawing and analysis of quartic curves, the results are here obtained, and with greater generality, merely by the use of curves of the second degree. Furthermore, the effects of typical changes in design characteristics may easily be assessed with the minimum of effort. The fundamental analysis is essentially mathematical and follows the treatment first laid down by G. H. Bryan in 1911 and since developed by Bairstow, Glauert, Jones and Bryant. Physical explanations are included where possible to amplify the underlying principles.

THE basic theory of stability has undergone no important modification since the publication of Professor G. H. Bryan's book on Stability in Aviation in 1911. The stability equations derived therein serve to‐day with the difference that axes and symbols have now been standardised and with the additional refinement of a non‐dimensional form of the stability equation introduced by H. Glauert. Due to the vastly increased knowledge of aerodrynamic characteristics, however, the stability derivatives are more readily assessable in any particular design case. This applies more particularly to longitudinal stability calculations which may, and indeed often arc, carried through with no wind tunnel tests available apart from a lift and drag curve for the aerofoil section used. There has also been some extension of the use of stability charts for deriving an approximate knowledge of the behaviour of the aeroplane when it receives a disturbance. These charts are exceedingly useful for obtaining periodic time and damping factor, but the assumptions on which they are based should be clearly realized.

THE advantages and disadvantages of the fixed wing for gyroplanes are examined. On the simplest assumptions an expression for the percentage load taken by the fixed wing of a gyroplane is derived. The values so arrived at are compared with those found by experiment and the discrepancy between the two is explained in terms of the increased downwash at the centre of the disc of the gyroplane. It is shown that as much as 50 per cent of the weight of the aircraft can be taken by the wing at top speed with moderate wing area and the most suitable setting. The advantages of an adjustable wing from the point of view of rotor speed control are pointed oat. The Lift/Drag of the combination is raised by 2 over the L/D of the rotor alone. The stability of gyroplanes is discussed.

The theory of the drag duo to the formation of a vortex street behind a body has been developed by Karman, and an attempt has now been made to extend the analysis to the case of a flow in a channel of finite breadth, but for simplicity the analysis is confined to the case when the breadth of the vortex street is not more than one‐sixth of the breadth of the channel. The formula obtained for the drag of the body is similar to that given by Karman and involves two parameters which must be determined experimentally.