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Aviation History
1927
1927 - 0648.PDF
SUPPLEMENT TO FLIGHT 54 AUGUST 25, 1927 THE AIRCRAFT ENGINEER stalling speed of the particular airplane. If VMP is less than Vmin. (see point D', Fig. 1) obviously, flight cannot be maintained and the ceiling as calculated from equation (23) will not be realised. To take care of this condition it is necessary to return to the fundamental expressions and retain V in the equation. Then P,/1/* = j 0-00000872 F,Vm)/ + .yL)- =- (24) V MP F;)emax. K-,i The symbols have the same meaning as before except that VMP is no longer given by the formula (20). An arbitrary approximate value of VMP for this condition is 1-1 Vmjn. This expression was derived by inspection of a number of performance calculations which had been previously made by the old detail method. ... VMP=l-lVmin. (25) In order to determine into which case any particular design falls we must first apply the expression deduced below. F-\1V MP = 14 f -!'.-•V (20) and V - / w » mm. — A / ; A,,.K|; max.But from (25) \ MP =1*1 Vmin. .-. 14 F,1-1 \Y 196 F, 1 - 1-21W * r " A(rjL,; max. A,,. = (26)93 • 6 K, ; max. A,,. — Total wing area. KK max. = Maximum total lift coefficient full scale. If the wing area is less than that given by equation (26), formula (24) must be used—otherwise formula (23). Summary (Absolute Ceiling) Case I when 4 — *•> 93-6K, ; max. O-OOoF/^F,.1/* (23) V )* des./ Case II when A,, < 93 • 6 j, max. P,5/4 =•= (() • 00000872 F, VMI,:i - ~ * F;,eiJ1ax.'%, (24) VMP = 1 • 1 V Both cases mm. V-- >' '- emax. — 1 — w Kw 0-425 PM"BX"3 (Vdes.r"1 r, = w (To be continued.) TECHNICAL LITERATURE. SUMMARIES OF AERONAUTICAL RESEARCH COMMITTEE REPORTS. THE SPINNING OF AEROPLANES. By S. B. GATES, M.A., and L. W. BRYANT, B.SC, A.R.C.SC R. & M. No. 1001. (Ae. 242.) October, 1926. This monograph is a comprehensive survey of recent work in this country on the subject of spinning. No general study of spinning has been made since the issue of R. & M. 618* in 1918 ; since then a great deal of further information from model and full scale sources has accumulated, and much solid progress has been made in fundamental parts of the subject. It is the object of the authors to put on record the present state of our knowledge regarding the geometry and mechanics of the steady spin and the evidence on which that knowledge is based, together with speculations which can reasonably be advanced regarding the character of the as yet unanalvsed motions of the entry to recover ' from the steady spin. The work is divided into eleven chapters, and an endeavour has been made to provide for several classes of reader. It is suggested that those readers who are interested in practical conclusions rather than in analyses may find all they require in the first three chapters. The first of these gives an elemen- tary survey of the problem using only the simplest mathe- matics : the second summarises the history of the subject, and the results of full scale experience of the spin ; whilst the third anticipates the analysis which follows, and collects the practical conclusions and recommendations which can be drawn from it. In Chapter IV the theory of the steady spin is elaborated, and is followed in Chapter V by the application of the theory to two contrasted aeroplanes whose aerodynamic properties have been measured in fair detail in the wind tunnel. Detailed discussions of aerod\iiamie questions which appear to be fundamental to the problem are given in Chapters VI to IX. The questions dealt with are (1) the autorotative properties of monoplanes and biplanes. (2) the couples due to sideslip, (3) the action of the controls, and (4) the influence of the running airscrew. Chapter X contains a summary of the technical conclusions from the mathematical analysis. The report concludes in Chapter XI with a short reference to future developments. A bibliography and full index are appended. The sources from which the material for the study has been drawn are mainly pilots' evidence, full scale observations, and wind tunnel experiments. The testimony of pilots regarding the spinning projK'rties of many different aeroplane types has been collected from time to time. In the best circumstances this evidence would fall short of precision, and it is not suqjrising that the complicated and confusing charac- ter of the spinning motion seriously detracts from the normal scientific value of a personal impression. Pilots say that the majority of aeroplanes can be made to fall into a fast spin by some action of the lateral controls—-some indeed have been observed to spin at moderate rates with lateral controls held neutral. Some outstanding types attain very high rates of rotation in a spin, from which recovery is dangerously slow. On the other hand a few types have been very reluctant to spin even with full rudder and ailerons. Besides these variation1* among the different types, we gather that an aero- plane has moods in its spinning behaviour, and spins of different individual aeroplanes of the same type show marked differences, whilst spins of even the same aeroplane are often notably different on different flights and in the hands of different pilots. We have every reason to suspect that equi- librium conditions in a steady spin are very sensitive to soiw factors which are as yet only imperfectly understood, it should be remarked, however, that there is no unique motion which could be called the spin of a given aeroplane ; the steaay spin is strictly a function of the control settings, and hus infinite gradations from the '" tight" or fast spin to a spir t glide of large radius at an incidence just above stalling. There is no evidence that the steady spin is usually reached in practice, when it is seldom that the manoeuvre is -«"*•'"'"' 59W * R. & M. 618. The investigation of the spin of an aeroplane.—H. Glauert.
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