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Aviation History
1921
1921 - 0648.PDF
SEPTEMBER 29, 1921 AN IMMEDIATE APPLICATION OF SLOTTED AEROFOILS ..: Their Use as Inter-Plane Ailerons • - By •' MARCO POLO " IT is, of course, well known that in the majority of aeroplanes the landing speed is considerably above the minimum speed at which the machine is able to hold the air. The reason for this is chiefly that at angles of incidence corresponding to maximum lift the aileron controls are insufficient to give the necessary restoring effect. The consequence is that practically all machines are landed much faster than they need be if the controls were more effective. While this applies also to a considerable extent to longitudinal control, the latter does not appear to present as great difficulties, since here it is mainly a question of the size of the control surfaces and of suitable balances. As regards lateral control, however, the problem is more difficult, owing to the fact that, more or less irrespective of size, when the angle of maximum lift is reached the aileron which forms a part of the trailing edge of the wing becomes inoperative. It appears to the writer that there is every probability that the old-fashioned inter-plane ailerons may be re-intro- duced. In the Curtiss machines of old these gave very good results, and enabled, for a time at any rate, the Curtiss Co. to get around the Wright wing-warp" patents. When it is remembered that those ailerons were of streamline section, and consequently had no very great L(. max., it should be possible to do very much better in our " enlightened " days* The suggestion which the writer would like to make is that it appears distinctly worth while to experiment with inter-plane ailerons formed by slotted aerofoils of the Handley Page type. There are several reasons for suggesting that this type would be more suitable than the fixed aerofoil of ordinary section. In the first place, the effect of slotting an aerofoil is to postpone " burbling " until a greater angle has been reached. Also, the lift is considerably increased. Both features would tend to make such an aerofoil par- ticularly suitable for inter-plane ailerons. Assuming that the slotted inter-plane aileron is so fitted on the machine that normally the slots are closed and the aileron is at an angle of incidence somewhat smaller than that of the main planes. The aileron would then be at an angle of attack which, if not corresponding to maximum L/D (which is not necessary for an aileron), would be at a small angle corresponding to small drag (which is very desirable for an inter-plane aileron). When called into use, the aileron on the lower side would have its slots opened slightly, and would thus increase its lift and tend to right the machine. On alighting, or when flying at or near stalling speed, the aileron, being set at a smaller angle of incidence than the main planes (assuming the aileron to be of the same section as the wings), would not have reached the angle of maximum lift when the main planes had reached or even exceeded this angle. Added to this fact, the opening of the slots would still further postpone the angle of maximum lift of the aileron, so that, several degrees beyond the " burble point " of the main planes, the aileron would continue to increase its lift, and consequently be capable of exerting a righting force. The matter of finding out the best section, slot formation and operation, and proportions of ailerons for any given machine would probably be one for full scale experiment, but in view of the fact that ailerons are not, in any case, of very large area, such experiments need not be very costly, and the gain to be anticipated would appear to be such as to make the experiments well worth while. It might be objected that such inter-plane ailerons, with their operating gear, would offer a considerable amount of extra resistance. While this is probably not to be denied, it should be remembered that the virtual landing speed of the machine would be reduced by the use of such ailerons, and that consequently the wing area itself might be reduced to give the same maximum speed. There would probably still be a considerable gain in practical landing speed. The writer offers the suggestion for what it is worth, and the Editor of this Journal has kindly offered to place at disposal space for a discussion of the problem if any reader should feel disposed to take the matter up. THE LONDON-CONTINENTAL SERVICES FLIGHTS BETWEEN SEPTEMBER 18 AND SEPTEMBER 24, INCLUSIVE • RouteJ Croydon- Paris Pari»-Croydon ... Croydon-Brustels Brussels-Croydon Croydon-Amsterdam ... Amgterdam-Croydon ... Totals for week No . o f flights * 22 23 8 7 4 3 67 No . o f passenger s 61 61 7 8 3 140 No. of flights carrying Mail s 6 10 4 6 43 33 Good s 13 18 4 4 4 3 46 No . o f journey s complete d \ 18 18 5 2 2 3 48 Averag e flyin g tim e h. m. 2 58 3 1 2 40 4 4 3 18 3 33 Fastest time made by D.H.18 G-EARO (2h. 12m.) D.H.I8 G-EARO (2h. 30m.) D.H.4 O-BALO(2h. 17m.)... D.H.4 0-BATO (2h. 27m.)... FokkerH-NABLOh. im.)... Fokker H-NABL (3I1. nm.) Type and (in brackets) Number of each type flying B. (3). D.H.18 (1), G. (4), H.P. (2), Sp. (5), V. (1). B. (4), D.H.18 (1), G. (4). H.P. (2), Sp. (5), V. (I). D.H.4 (4). D.H.9 (2), G. (1), Sp, (1). D.H.4 (4). D H.9 (2), R. (l). D.H.9 (i), F. (2). D.H.9 (1), F. (2). • • " ' • Not including " private" flights. t Including certain journey* when stops were made $n route. % Including certain diverted journeys. Av. =-= Avro. B. = Breguet. Br. = Bristol. Bt. = B.A.T. D.H.4 — D« Havilland 4, D.H.9 (etc.). F. = Fokker. Fa. =• Farman F.50. G. = Goliath Farman. H.P. == Handley Page. M. — Martinsyde. N. = Nieuport. P. — Potez. R. = Rumpler. Sa. = Salmson. Se.— S.E.5. Sp. = Spad. V. = Vickers Vimy. W. = Westland. The following is a list of firms running services between London and Paris, Brussels, etc., etc.:—Co. des Grande*Expresses Aeriennes [ Handley Page Transport, Ltd. ; Instone Air Line; Koninklijkie Luchtvaart Vfaatschappij; Massagerias Aericnnes; Syndicat National poor l*£tude des Transports Aeriens; Co. Transaerienne. Audibility of Oppau Explosion THE Air Ministry announces that as the distance of audibility of sound is of great scientific importance in questions relating to the structure of the atmosphere, the Director of the Meteorological Office, Air Ministry, would welcome information from those who heard the sound of the Oppau explosion. 648
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