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Aviation History
1917
1917 - 0227.PDF
MARCH 8, 1917. [As a number of letters reach us signed with initials only, some of which do not give a complete address, we would point out that such communications cannot be dealt with in our columns. Full name and address, which will not be published, must always be given.—ED.] A. R. (Norbury); B. F. S. (Bristol). The subject of proper heat treatment of Duralumin, which is of general interest, is dealt wita in a. pa.fagra.pa Oapage 238. H. F. V. B. (Holt). For speeds such as are attained in present-day aeroplanes the centre of pressure is not generally supposed to shift for any given angle of incidence. What you apparently have in mind is the travel of the centre of pressure with changes in the angle of incidence. The amount of this travel varies in different sections, but that shown in our " Answers to Correspondents " column in last week's issue of " FLIGHT " may be taken as being fairly typical for a modern section. The travel of the centre of pressure here ranges from about o- 32 of the chord from the leading edge at about 12° incidence to o" 57 of the-chord at 0° incidence. Where a single inter- plane strut is fitted this should obviously be so placed that the moments around its point of attachment are the same whether the c.p. is in front of the strut or behind it, i.e., half-way between the two extreme positions of the c.p., in this case at about 0*45 of the chord from the leading edge. With regard to the efficiency of the spur gear you refer to, there is no reason to suppose that this would be less for the larger spur wheels; on the contrary, the larger the wheels, within reason, of course, the greater the number of teeth that can be given them, which always makes for greater efficiency. H. E. B. (Walthamstow). In machines with twin propellers it is usual practice to have the two propellers running in opposite directions in order to equalise the torque. This was, for instance, the case im the twin-engined Caudron biplane, where one of the Anzani engines was altered to run in the opposite direction to that usual in these engines. Machines have, however, been built and successfully flown, in which both propellers ran in the same direction, and we have not heard of any difficulty arising from that source. A. W. D. (Fareham). In the majority of modern aeroplanes the ailerons are so interconnected that when one moves down the other moves up. It is not, however, invariably the case, some machines, as for instance certain of the Short seaplanes, still being fitted with the older type single acting ailerons. It is generally thought that the tendency of a machine to yaw when the ailerons are single acting is somewhat lessened by inter- - connecting them, but pilots appear to differ in their opinions on this point. The chief advantage of aileron control over warp control, apart from the fact that warping a wing will weaken it in time, lies in the fact that the former is more positive in its action at high angles of incidence. This is due to the fact that warping a wing simply means increasing its angle of incidence towards the tip, and if the wing is already flying at or near its angle of maximum lift a further increase in the angle of incidence means more resistance but not more lift. With the aileron however, a virtual increase in the camber is obtained, which may give more resistance, but which will certainly give more lift. E. H. S. (Hull). If you are physically fit the fact that you have had on flying experience does not bar you from applying for a com- mission in the R.N.A.S. If accepted you would be trained at a Government school. The pay of a Probationary Flight Officer is 10s. per day plus 4s. per day flying pay. On graduating you would receive a further 4s. a day flying pay. D. H. L. (Woodford Green). Your application will probably be put back until you are 18. A. H. (Blandford). For enlistment in the R.N.A.S. you should apply to any Naval recruiting office or to the Drafting Office of the R.N.A.S. at the Crystal Palace. You can enter as a skilled mechanic if you pass the standards, whatever your Army classification. Unskilled men are only taken if they are Bi, B2 or Ci. R. H. T. (Seaton Carew) and many others. The minimum age is 18. For particulars of the R.F.C. Cadets apply to the Directorate of Military Aeronautics, War Office, London, S.W. B. H. W. (Shrewsbury). When you are 18 send in an application, on a form which you can obtain from the Admiralty, to the Director of Air Services. You should get a copy of " Hints for Flight Sub- Lieaitenants, which can be obtained from " FLIGHT " offices for is. 2d., post free. A. H. C. (Golders Green). The thrust obtainable with a 45 h.p. Anzani engine will, of course, vary according to the efficiency of the propeller used.' As a fair average figure, which may reasonably be expected, we should think you might count on a thrust of about 200 lbs. The Anzani engines are designed to be mounted on a single capping plate by means of six bolts l\ passing through the crank case. The spacing of these bolts is shown in the accompanying diagram, as is also the diameter of the circular hole cut in the engine plate through which is passed such accessories as magneto, oil pump, &c. An illus- trated description of various mountings and cowlings of Anzani engines appeared in our " Constructional Details " series in our issue of September 14th, 1916. The outside diameter of the engine plate will depend on the shape of the nose of the body, but it should be kept as small as possible, both in order to save weight and also to reduce vibration. For the 45 h.p. Anzani engine the engine plate is usually made of 10 Standard Wire Gauge mild steel. W. S. (Lennoxtown) and numerous other correspondents. Apply to the Secretary of the Admiralty for the conditions under which temporary commissions are granted in the R.N.A.S. G. B. P. (Huntingdon). 1. You would probably have to pass through the Cadet Corps. 2. R.F.C. uniform without rank badges and with white band round cap. 3. It is unlikely that he would obtain commission as pilot, but might be accepted as an Equipment Officer if qualified. L. H. (Wigan). 1. 12s. 6d. a day. 2. Apply to the Directorate of Military Aeronautics, War Office, S.W. L. J. P. (Sleaford). You cannot do better than get Burls' " Aero Engines," which can be obtained from " FLIGHT " Office for gs. 6d. post free. J. T. (Highgate). ,.,..,,. Apply to any firms advertising in FLIGHT, asking if they have any vacancies. They would also give you particulars regarding premiums and length of apprenticeship. G. E. G. M. (Edinburgh). We should recommend " Aircraft of To-day," which can be obtained from " FLIGHT " Office for 5s. 6d. post free. L. H. C. (Wanstead). You would probably be able to join if there are vacancies. For the R.N.A.S. apply to the R.N.A.S. drafting office, Crystal Palace, S.E., and for the R.F.C. to the Polytechnic, Regent Street, W. W. H. (Manchester). (a) You must apply for admission to the R.F.C. Cadet Corps, (b) The pay is the same as a private, (c) Apply to the Director of Air Services, Admiralty, S.W. J. W. S. (Barnsley). / You would only be able to enter either if you can pass the trade tests ; see reply to L. H. C. abore. 227
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