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Aviation History
1920
1920 - 0261.PDF
MARCH 4, 1920 •-_-- SCHEDULE OF LOAD FACTORS AND FACTORS OF SAFETY.GENERAL CLASS. (a) Load factor with C.P. in most for- ward position(b) Load factor with C.P. in the position corresponding to maximum hori-zontal speed at ground level (c) Factor of safety in a terminal nose dive(d) Specified lift coefficient for fins and rudders. (Under this loading thefactor of safety of the fuselage should be unity)(ei) Static load factor on undercarriages \e2) Specified vertical velocity (ft./sec.) for determining travel of under-carriages Total Up to 3,000lbs. 8 6 1-75 o-68 10 weight of aircraft. 3,000 to 10,000lbs. 8 — 6* 6 — 4-5* i-75 o-6 8 — 6* 10 Above 10,000lbs. 6 4-5 i-75 o-66 10 • The decrease in load from the larger value is directly proportional to theincrease in the weight of the craft. Methods of Calculation.—In using the above schedules the calculations of strength will be checked by the methods of the Handbook of Strength Calculations (H.B. 806, second edition), published by the Technical Department, Air Ministry. In all calculations and in specifications of load factors and factors of safety, design figures should be em- ployed and not those obtained from breaking tests. Further, when dealing with steel tubes, the specifications of the Engineering Standards Committee, based on the figures for yield points, are approved for stress calculation purposes ; for stream line wires the breaking load should be taken in pre- ference to the yield point which is, in these cases, ill-defined. Redundant wires, except as mentioned in (/), are to be con- sidered as neglected. With a view to facilitating the use of the schedule, the following additional matter should be noted. (1) That for (a) and (b) the positions of the centre of pressure should preferably be determined by a test on a model with a 6-in. chord at 60 ft./sec, but that the Air Ministry might agree to issue a certificate based on results for a monoplane model of 3-in. chord tested at 40 ft./sec. For biplanes, a biplane test is preferred ; similarly for tri- planes. For case (b) the maximum horizontal speed at ground level should be obtained from the formulae given in (2) below. From this speed the value of the lift coefficient is obtained and the position of the centre of pressure determined from model tests as denned above. (2) That for (b) and (d) the maximum speed at ground level should be defined by the following formulae giving the maximum speed for given loadings and weight of aircraft. Should the manufacturer desire to specify the maximum speed in any other manner he is at liberty to make a special application. For single engine aircraft— Where N, V, u> and p arethe power per unit weight, the speed, the-—0-316) loading and the density in any system of con-sistent units; e^g., N in ft. lbs. per sec. per 1b. For multi engine aircraft— For boat seaplanes— an(j (v -v/' ~ 1' 425)3= 2-74 (N y/ ^-0-304) p in slugs/cub, ft. (a " w ground level). The above formulae may also be expressed in the form :— For single engine aircraft. Where N is horse-power per • V ., , N . 1,000 lbs. / •=- - 25 V = 16-6/ --ii-8\ '. I>OOoh.p. wFor multi engine aircraft. For boat seaplanes. / V\J^~2°) I4' \y being the weight of H.P.the horse-power of the *ircraft in q^stion.V is in miles per hour at ground level; . N and '4 (A/~ ~ ""35 1 tu is wing loading in lbs. per (3) That for (c), the case of the limiting nose dive calcula- tions submitted by the manufacturers would be considered by the Air Ministry; otherwise, the following table with the necessary extensions for other wing sections would be em- ployed. Table of tail plane loads in limiting "nose dive. Type of Aircraft Wing Section Employed R.A 0-6 0-55 o-5 .F. 15 We / We I We I R 0 0 0 .A 9 ' 7 •5 F. 60 We I We J We Single engine, .. .. .. Multi-engine Boat Seaplane Where W is the weight of the aircraft. c is the chord of the main planes, and / is the distance from the centre of gravity of the aircraft to the centre of pressure of the tail plane. (4) That in the case of (d) the static strength of the under- carriage should be checked for the four following cases :— (i) When the aircraft lands on an even keel and with the chord of the main planes borizontal. (ii) When the aircraft lands on an even keel and so that the tail skid and undercarriage tou«n the ground simul- taneously. (iii) When the aircraft lands so that one wing tip touches the ground at the same time as the main undercarriage and with the chord of the main planes horizontal. (iv) When the aircraft lands so that one wing tip touches the ground at the same time as the main undercarriage and so that the tail skid and undercarriage touch the ground simul- taneously. In (i) and (ii) the load factor should be that specified, and in (iii) and (iv) the load factor should be at least half that specified. As regards length of travel of the undercarriage, its amount should be such that the total work of compression is equal to the value of £ (wv^/g where w is the weight of the machine and v is the specified vertical velocity ; also, the maximum load should not exceed the specified static load on the under- carriage. - . t 1 1: i Smaller and Cheaper Aeroplanes LECTURING at King's College to L.C.C. school-teachers on " Aviation and the Possibilities that await the Develop- ment of the Aeroplane," Mr. F. Handley Page pointed out that during the War economy in the cost of running played no part in the design. Their experiments had been directed to finding out whether it would not be possible to fly with smaller planes, and one of their interesting discoveries indicated that we should be able to use planes of at least half the size of the present area. Experiments showed that they • would be able to land slower with these smaller machines and that with 25 h.p. instead of 100 h.p. they would be able to fly with pilot and passenger, and with enough petrol and oil for five hours at a speed of 100 to no miles an hour. Such a machine would cost from ^150 to £200. "Which means," said Mr. Page, "that we shall be able to get a small machine that you can put perhaps in the coal- shed, and drag it out on a fine Saturday afternoon for a trip to any destination within a range of 500 miles at a cost no greater than that of running a small motor car." The price of flying from London to Paris will be comparable in the future, said the lecturer, with travelling by omniBus from the Bank to Charing Cross, though it will be a long time ahead yet, as at present we have only the old type of machines. Development, however, would be along the cheaper lines he had indicated. " With the enormous production of motor-cars here and in America and other places, the day is not far distant when it will be impossible to move along the roads ; and there will be only one thing left to do if you want to go anywhere, and that is to travel by air." H.P. Paris and Brussels Air Service ON the Handley Page Continental Air Services, between September 2, 1919, and February 26, 1920, 976 passengers and 46,383 lbs. of freight have been carried over a distance of 71,369 miles. 20th Squadron R.A.F. IT is proposed to hold a reunion dinner in London. All past.members are requested to communicate with J. A. HONK, 23, Palmerstone House, Old Broad Street, London, E.C., who will inform them when definite arrangements have been made. 26l F 2
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