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IT seems rather strange that while the general property of wing flaps of putting up both the lift and the drag of a wing at the same time has been known for many years, so little practical application of this result has been made until quite recently.

THE purpose of these notes is to discuss the part played by flight‐testing in some of the more topical branches of aerodynamic research and to describe some of the experimental methods used. The expression “flight testing” is used in preference to “full scale” on account of the extent to which full scale tests are now made in large wind tunnels.

FROM the early clays of flying, aeroplanes have been provided with surfaces intended to give separate control about the rolling and yawing axes. In practice, however, the control surfaces themselves and the stability characteristics of the aeroplane combine to defeat the independence of rolling and yawing control. Recognition of this fact has lately resulted in attempts to arrange the stability characteristics of the aeroplane so that a combined rolling and yawing motion, of the type required in normal flying, is produced by only one control surface.

THE change from the parallel wings of the now obsolescent biplane to the tapered wings of the monoplane, usually fitted with flaps, raised a great number of problems, both aerodynamic and structural. Work on these has been pursued vigorously during the past few years, but the designer is still some considerable distance from having all his questions answered. For instance, further information is required as to the relation between wing thickness and profile drag before it can be decided what is the maximum thickness which can be used, taking both aero‐dynamical and structural considerations into account. This question is complicated by the fact that, so far as the tip sections are concerned,. the indications are that the thickness ratio has important effects on the nature of the stall, violent or gentle. So, too, will such factors as centre line camber and position of maximum ordinate affect the nature of the stall in greater or Jess degree. Added to these factors there is, of course, the important one of the taper itself, including—as is now realised—the question as to the way in which the tapering is done, that is, whether by sweeping the trailing edge forward or the leading edge back, or, as is more usual, a combination of the two.

The third term has been expressed as but in wind tunnel work it is often more convenient to measure were the omission of the dash signifies that the moment is now measured about a wind axis. The two quantities are very closely related and the measurement of one tells us almost as much as if the two were known. The latter, however, tells us either directly or indirectly what effect the addition of fin and rudder will have on the autorotation properties of the wings alone. The damping of fin and rudder being due essentially to the air flow meeting them at an angle on account of the rotation it should theoretically be possible to deduce this dynamic quantity from a simple static test of moment due to yaw angle. An experiment to test this was carried out several years ago but the static test did not give any approximation to the truth. This was ascribed at the time to the shielding of fin and rudder by the tail plane in the rotative experiment and subsequent work has amply confirmed this view. It is now known that shielding by the tail plane is by far the most important factor in determining the efficiency of the vertical surfaces at high angles of attack.

Under this heading are published regularly abstract 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.

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.

IT is shown that the down gust requirement is open to the objection that heavier loads may be taken by the front spar at lightly loaded weight than those for which the spar was designed. This is normally covered by the factor of safety of 2, but the method of calculating the loads on a basis of all up weight is not very rational. Some available data concerning the magnitudes of down gusts are reviewed and the sharp‐edged gust hypothesis briefly examined. The British requirement is compared with those of the I.C.A.N. and the U.S.A. The conclusions are that there are no very practical alternatives to sharp edged theory and while the estimate of the magnitudes of normal down gusts at 25 f.p.s. appears satisfactory and British standards of strength in this respect need not be tightened up, a modification to the requirement to meet the above objection is desirable. A suggested alternative is put forward.

THERE has been a very marked tendency of late towards simplifying the control of aeroplanes. Those who have read M. MIGNET'S book on the reasons that led him to develop his Pou de Ciel, will remember that he decided to go back to the beginning, as he himself had found the complications of the normal triple control confusing and complicated. He has consequently gone back to a design which is in essentials strongly reminiscent of the early tandem monoplane evolved by S. P. Langley. This included a heavy dihedral angle with two main planes set in tandem at a fore‐and‐aft dihedral to each other. Lateral stability and control was dependent entirely upon the dihedral angle and the rudder, ailerons being absent.

English Electric has appointed Mr E. B. Lynch as Manager, Aircraft Equipment Sales, responsible for all the products of its Aircraft Equipment Division at Bradford covering aircraft a.c. and d.c. generation, control and protection equipment motors and actuators, and for all the aircraft equipment products of D. Napier & Son Ltd., which are ‘Spraymat’ ice protection system, ‘Sierracote’ heated glass and plastic windscreens and'Sierraglo' electroluminescent lighting equipment.