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Aviation History
1924
1924 - 0118.PDF
The value of K1 is obviously variable with the type of aeroplane, but the Report states that it is recommended that for the average aeroplane of clean design Kj be taken as 20-3, and that the figure will probably vary from 19-5 to 21-0, according to design, but that it requires an unusually clean design and high speed-range to secure values of Kj in excess of 20-5. It appears that for all machines of ordinary design reason ably accurate results may be obtained, but in the case of a light 'plane, say, a monoplane of very clean design, a value of K! very considerably in excess of 20-3 can be obtained. Let us, for the sake of argument, take a light 'plane having a wing loading of 4 lbs./sq. ft. and a power loading of 3Q lbs./h.p. The stalling speed of such a machine would —' J, would probably be about 35 m.p.h. The speed range, / — V then be, according to the formula, and assuming a propeller 20-3 X v/0^78 20-3 x 0-92 FEBRUARY 23$, 1924 ceiling. Its derivation is fully dealt with in the Report, and the average value of K4 is 61 •!. In the tables of data given in the Report the extreme variation in the value of K4 is from 60-2 to 63-2. One of the tables of the Report gives the absolute ceilings calculated by the formula, compared with the absolute ceilings actually obtained with a number of machines, and the agreement is quite satisfactory, especially in view of the fact that in calculating from the formula a constant value L/D = 8 was used. Reference has already been made to the use of the formula in conjunction with the curves published herewith. To show the sort of accuracy obtained we give below the calculated and actual absolute ceilings of a number of machines :— Absolute Ceiling (ft.). Aeroplane. USXBIA M.B. 3 efficiency of 78 per rent., 1-84. 735 x 30 The maximum speed would then be 35 1050 < 1-84 = 64-4 m.p.h. There is little doubt that a modern light monoplane of clean design would have a considerably greater speed range than that, and that values of Kx of 21 or 22, or even greater, might be obtained. This is, presumably, mainly due to the high value of L/D of light 'planes. With regard to the formula for intial rate of climb, the Report points out that, as was to be expected, the value of K, decreases with increase in I —- ). Plotting K„ against speed range it is found that the points fall on or near to a smooth curve which has the equation .-0.27 K„ M. 80 .. "D " .. Roland D. VI-B MS-*'AR" .. D.H.-4.. Fokker D. VIII VE-7 S.E.-5 .. JN-4H. . Calculated 19,800 23,500 19,300 22,000 15,700 19,300 15,400 18,000 20,400 18,300 18,200 18,200 Actual. 22,400 24,900 19,900 23,600 15,100 19,000 16,600 17,600 22,100 19,000 19,800 19,000 The service ceiling, i.e., the altitude at which the rate of climb is 100 ft./min., is found from a simple formula. At any altitude the rate, of climb is given by the eqnationl C =C, C -2- :.-•(£)-" The average value of K 2 is in the neighbourhood of 0-8 ; thus when the speed range ratio is 2 the value of K 2 is 0-83. When the speed range is 2-25, th»-value of K, is 0-8 ; and when the range is 2-8 K2 is 0-78. The Report points out that for very low values of C„ the formula is unreliable, since small percentage errors in either member of the equation may mean large percentage errors in C„. It is stated that the limiting value of C„ is usually about 400 ft./min. Little need be said concerning the formula for absolute where Ha is the absolute ceiling, C„ the initial rate of climb, and C the rate of climb at altitude y. At the service ceiling C ion A y c„ - ioo , ... „ __ Co- ioo = 100 and-q- = - ; from which y = HS — Ha p where Hj is the service ceiling. The Report containing the derivation of these and other performance estimate formulae is American National Advisory Committee for Aeronautics, No. 173, and copies can be obtained by application to The Superintendent of Documents, Government Printing Office, Washington, D.C., U.S.A. The price of the Report is 5 cents., and another 5 cents or so should be added for postage. THE ROYAL AERO CLUB OF THE U.K. OFFICIAL NOTICES TO MEMBERS. COMMITTEE MEETING A MEETING of the Committee was held on Wednesday, February 20, 1924, when there were present: Lieut.-Col. J. T. C. Moore-Brabazon, M.C., M.P., in the Chair ; Group-Capt. F. W. Bowhill, C.M.G., D.S.O., R.A.F. ; Mr. E. C. Bucknall, Lieut.-Col. M. O. Darby ; Col. F. Lindsay Lloyd, C.M.G., C.B.E. ; Lieut.-Col. A. Ogilvie, C.B.E.;' Lieut.-Col. M. O'Gorman, C.B. ; Mr. F. Handley Page ; Mr. T. O. M. Sopwith, and the Secretary. Election of Members.—The following New Members were elected :— Harold James Andrews. Allan Lancelot Addison Kenneth Woodhouse Brew- Perry-Keene. ster. Henry Basil Pett. Flying Officer Hubert Steven Arthur Roach Thomas Redward Burt. Pipon. Flying Officer John Francis Pilot Officer Thomas Bain Bythell. Prickman. Edwin Haigh Chalmers. Major Russell Purves. Pilot Officer John McPhee Jean Baptiste Richard. Darroch. George Richardson. Charles Frank Day Evans. Pilot Officer Reginald Austen Austin Christopher Ferguson. Poyntz Roberts. Anthony Archibald Fletcher. Archibald Russell. Flying Officer Arthur Edwin Flight-Lieut. Norbert Marie Golds. Sackville Russell. Flying Officer Charlton Elijah Dudley Salthouse. Hallawell. Herman Sanders. William Allan Hammerton. Lieut.-Col. Francis Claude Harry Archer Hince. Shelmerdine. Phillip Thomag Hubbard. Flight-Lieut. Horace Scott Thomas Price Jenkins. Shield. Edward Arnold Jones. William Harry Statham. Frank Hazell Jones. Elias George Steer. James Morton Leach. Capt. David James Stewart. Pilot Officer Francis Richard Charles Tindal .Travers. Lines. Frederick Dudley Travers. Robert Henry Mcintosh. Norman Wralter Wale. Pilot Officer Edgar Archibald George Louis Gordon McKinley-Hay. W'atson. Bernard James Malyan. Capt. Stanley Frederick Cecil George Mathew. Aubrey Welsh. Lewis Motley. Flying Officer Charles Maurice Ashdown Newnham. Bernard Wilson. Flying Officer Herbert James Hubert Edward Winch. Payne. Flight-Lieut. Frederick Herbert Howard Perry. Robert W'ynne. Racing Committee.—Reports of the Meetings of the Racing Committee held on January 28 and February 4, 12 and 18 were received and adopted. The following items were included in the Reports :— Two-Seater Light Aeroplane Competition, 1924.—The Regulations for the Prize of £'3,000 offered by the Air Council were finally approved. The King's Cup Race, 1924.—Proposal that this year's Race be confined to seaplanes. This was approved. Aerial Derby.—Proposal to limit the landing speed. Further proposal that the Race should be held away from London, and preferably near a large town in the south, giving facilities for a clear course in the open country. Beaumont Cup.—The entry of the Gloucestershire Aircraft Co. for the Beaumont Race to be held in France in June next was confirmed. Late Lieut.-Col. J. L. Travers.—The message of sym pathy sent on behalf of the Club was confirmed. Late Mr. Lawrence B. Sperry.—The acknowledgment of message of sympathy sent on behalf of the Club was • received from Mr. and Mrs. E. A. Sperry. Aviators' Certificates.—The following Aviators' Certifi cates were granted :— 7950. Harold James Andrews, February 1, 1924. 7951. Donald John Munro. February 5, 1924. 7952. Archibald Russell, Mav 16, 1918. Offices: THE ROYAL AERO CLUB, 3, CLIFFORD STREET, LONDON, W. i. H. E. PERRIN, Secretary. 118
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