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Aviation History
1912
1912 - 0024.PDF
'••WPW WIM^j. •».f>.l,W»...|...«...W»^- P- —.^—.-,••,1.^ i- • .1 .ii.-. • • •- [pjGHT] is given by V2 = z'2 + 2^, where v is the velocity at start. In the present case, ^ = 95 f-p.s. (65 m.p.h.), £ = 550, ^=32*2, and V = 210 f.p.s., or 140 miles per hour. This supposes the machine falling in vacuo under the influence of the weight alone. It therefore neglects resistance and the thrust of the propeller. If the latter were working, it would probably just balance the resistance ; but, on the other hand, if the engine were stopped when starting the dive, the resistance would diminish the final velocity. The force on the planes when attempting to take a horizontal direction is given by the principle of momentum. The whole of the vertical momentum being destroyed, this force is given by „ , W in tons V r in tons = X T x cos 6, g t where W is the weight, V velocity in f.p.s., / the time taken to flatten out, and 6 is the angle the line of dives makes with the vertical. Substituting W--6, V=210, ^=32-2, 6=35°, F = 3^. If the flattening out is instantaneous, / is very small and F very great. Actually t will be of appreciable amount. Taking t=\ sec, F=I54 tons ; whilst if t = % sec, F = 6'2 tons. In the latter case the force on the wings is ten times the force due to supporting the weight. If / is 5 sees., the machine will have travelled 1,050 ft. while flattening out, and the total force on the wings will be double the usual. Upper Tooting. A. W. JOHNS, R.C.N.C, M.IN.N.A. [1460] I notice, on looking through the correspondence re the Fiiey Disaster that almost all of your correspondents take ^as^ 32*2, not taking into account the fact that the fall was not vertical, but at an angle of 65°, in which case g becomes 32-2 sin 650, or 29'l83. Again Mr. G. H. May [1451] multiplies 65 by %% to turn it from m.p.h. into f.p.s., instead of by f|. Taking these figures, 11 =• 65 m.p.h. = *-|8. f.p.s., £-=29*183, A = 55o. V* = u"- + 2gh = (*5fi)2+2x 550x29-183 = 9088-4+ 32101-3 = 4118974 f.p.s. .'. V = 202'95 f-P-s., or 138-375 m.p.h. Then, taking P = -003V2, P = -003 x 19147-641 = 57-44 lbs. per sq. ft., and area of planes = 290 sq. ft. .-. Total pressure due to velocity = 57*44 x 290 lbs. » 16,658 lbs. Again, we have to add in stress put on planes owing to weight of machine. This stress = 2 x 1350 = 2,700 lbs. .-. Total pressure on planes = 16,658 + 2,700 lbs. = 19,358 lbs. = 8-6 tons. This, I think, differs from other estimates as published in FLIGHT. Edinburgh. J. C. S. MACGREGOR. " A Study of Bird Flight." [1461] Dr. Hankin shows himself such a capable and honest observer that one does not like to criticise him hastily, but perhaps the discussion of one or two points may enlighten the weaker brethren—of whom I am one. It seems to me that in the treatment of flapping flight, especially poise flapping or hovering, that he does not give enough weight to the gliding tendency, and that this to some extent vitiates his observations. On page 955, indeed, when treating of " half flaps," he acknowledges the presence of this gliding element, but so far he has made no other reference to it. Now it is obvious that even in full flapping—e.g., in hovering— the bird's wings pass through the most efficient gliding position, and on to an extreme dihedral in both directions. That is to say, its efficiency as a glider would vary, say, from I to 90, where 100 is absolute efficiency. The average, then, must be quite worth consideration, and at any rate there is one moment in each flap where the wings are at maximum gliding efficiency. The result of this is that there is a positive forward tetdency which must be counteracted by some backward reaction in the flap if the bird wishes to hover, i.e., the wing tips must show a negative angle of incidence, or else there must fee a backward motion of the whole wing- Further, the flap has not to sustain the whole weight of the bird, but only that part which is not equalized by the gliding reaction. It is obvious that a bird when half-flapping may be using its wings as propellers, and what we may call the aeroplane effect is then seen—i.e., it is sustained by the reactions against the wing caused by forward motion, and not by direct downward reaction of the wing beat. If we followed this line of thought into full-flapping progress, we see that an appreciable fraction of the weight must be so sustained, e ven though the gliding efficiency has been greatly reduced. JANUARY 6, 1912. I have noticed frequently an interesting example of this gliding reaction in flight shown in the flight of gulls. When travelling from place to place against a slight wind, their wings work quite leisurely, but if they turn round with the wind they have to flap away at a tremendous pace to keep up at first. As has already been pointed out, I think, by one of your correspondents, if instead of a glider being propelled through the air, it either (1) glides in a rising current or (2) glides while exercising a downward reaction from its. wing area, then it will b:,th be sustained, and travel forward at a speed limited by the head resistance. The application of this to flapping flight is both interesting and instructive. Dublin. p. D. M. ® ® ® ® Mem for Model Flyers. MESSRS. WILLIS BROTHERS, of 60, Cambridge Road, Hastings, ask us to state that by mutual arrangement they are no longer associated with Messrs. Mann and Grimmer. They are, however, still supplying machines, parts, and all model materials, &c, and are making a speciality of rubber and lubricant. ® ® ® ® PUBLICATIONS RECEIVED. Aeronautische Meteorologie. Part I. By Dr. Fr. Linke. Frankfort: F. B. Auffarth. Price 3 marks. Aeronautische Meteorologie. Part II. By Dr. Fr. Linke. Frankfort: F. B. Auffarth. Price 3 marks 50. Chemie der Gasse. By Dr. Fr. Brahmer. Frankfort: F. B. Auffarth. Price 4 marks. ® ® ® ® NEW COMPANY REGISTERED. Thrilling Flights, Ltd.—Capital £2,600, in £1 shares. Acquiring a captive aeroplane device formerly belonging to Vanes, Ltd., together with the British and foreign patent and other rights. ® ® ® ® Aeronautical Patents Published. Applied for In 1010. Published January tfh, 1912. 29,148. I. M. SAWYER. Steering device for aeroplanes. Applied for In 1011. Published January 4th, 1912. 2,904. G. MEES. Flying machines with gyroscopically-^cting stabilising propellers. 3,125. G. H. CHALLENGER AND BRITISH AND COLONIAL AEROPLANE CO Supporting planes. 3,532. G. AND M. ANTONI. Aerial machines. 3,596. W. E. BACK. Propulsive power for aeroplanes. 23,922. —PELTERIE. Teaching control of aeroplanes. PRINCIPAL CONTENTS. Editorial Comment The Future of the Dirigible. The Dawn of Another Year. Flight Pioneers : Mdme. Jane Herveu The British War Office Trials Paris Aero Show ' Royal Aero Club Notes From the British Flying Grounds Air Eddies. By " Oiseau Bleu " British Notes of the Week Foreign Aviation News Aeroplane Efficiency. By A. E. Berriman Models. Conducted by V. E. Johnson, M.A Progress of Flight about the Country British Patents Correspondence PAGE 2 3 4 5 9 10 12 13 14 15 18 19 22 z3 FLIGHT. 44, ST. MARTIN'S LANE, LONDON, W.C. Telegraphic address: Truditur, London. Telephone: 1828 Gerrard. SUBSC^PTION RATES. FLIGHT will be forwarded, post free, to any part of the world at the following rates:— UNITED KINGDOM. ABROAD. J. d. s. d. 3 Months, Pott Free ... I 8 3 Months, Post Free... 2 9 6 „ „ -. 3 3 6 „ 5 6 12 „ „ ... 6 6 12 „ „ ... n o Cheques and Post Office Orders should be made payable to the Proprietors of FLIGHT, 44, St. Martin's Lane, W.C., and crossed London County and Westminster Bank, otherwise no responsibility will be accepted. Should any difficulty be experienced in procuring FLIGHT from local newsvendors, intending readers can obtain each issue direct from the Publishing Office, by forwarding remittance as above. 24
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