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Aviation History
1918
1918 - 0180.PDF
FEBRUARY 14, 1918. SWERS TOCORRESPONDENTS [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 Full name and address, which will not be published, must always be given.—ED.] Notice to Correspondents in General. Applications for commissions in the Royal Naval Air Service should be addressed to the Director of Air Services, Admiralty, S.W. The necessary form and a pamphlet giving the conditions of entry and other information can be obtained from the Secretary of the Admiralty. Applications for commissions in the Royal Flying Corps should be sent to the Director of Air Organization, R.F.C. Air Ministry, Strand, W.C. Those who wish to enlist in the R.N.A.S. should apply to the nearest naval recruiting station or to the R.N.A.S. Drafting Office, Crystal Palace, S.E. Skilled mechanics are taken whatever their army classification, but unskilled men are only taken if they are classified Bi, B2, or Ci. Recruiting for the R.F.C. is closed for the time being, and any enquiries should be made to the Officer Commanding, Royal Flying Corps Depot, Farnborough. Enquiries with regard to appointments in the A.I.D. should be addressed to the Chief Inspector, Aeronautical Inspection Department, Air Ministry, W.C. 2. J. H. C. (Herne Hill).—In the first instalment of our article on " Metal in Aeroplane Construction " published in the February 22nd, 1917 issue of " FLIGHT " there occurred a printer's error in the strut formula, which was, however, pointed out in the following week's issue. In the corrected form the formula—which is Rankine's strut formula for pin connected ends and given in all text books on structural fc x A In one engine (12 cylinder high compression water cooled^ I used a number of small plates which were inserted by a mechanic between the valve stem and the tappet while the engine was idling. The thickness of these plates: was just sufficient to produce a slight loss of compression and explosion Plat engineering—should be : P = + • fc x P Generally speaking, this formula is found to give fairly accurate results, and is extensively employed, although for aeroplane struts others have been suggested from time to time. Mr. J. C. Hunsaker carried out a series of tests on spruce struts which gave results as indicated in the following formula : - = 6500 — 46-5 when T is less than 70, and --• = - ;,%-A k k A //\- when - is greater than 70. E. the modulus of elasticity, for spruce is 1,825,000 Ibs./sq. in. ' R.L., 2nd Lieut. R.F.C. (B.E.F.).—sends us the following query : " Would you mind giving me your opinion on an engine question. The point concerns running up a Beardmore 160, which has just been filled up with hot water. Should the engine be run at less than 800 r.p.m. ? I hold that it should not, for the following reasons : 1. The plugs become slightly sooted and oily-when she is kept ticking over. (No. 1 cylinder seems to be the worst offender.) 2. Being a high compression engine she vibrates like fury at very low speeds. I have been working with Beardmore engines since May last, and so far have never spoilt my engine through " revving " at 800. As the question appears to be one of general interest we have specially submitted it to an engine expert, whose reply is as follows : "lam of the opinion that 800 r.p.m. is not too slow for the engine to " idle." As your correspondent remarks, this engine has a high compression and is very prone to vibration, especially when running at anything near its revs., and a plug is missing. Intermittent missing will cause very serious vibration, and for this reason it is advisable to substitute new hot plugs if the engine has been kept " idling." for any length of time. Once a plug has " oiled up " it will more readily oil up again, and, of course, the plugs are liable to oil up more readily when the engine is idling. .» ; .*— .,- [gj Strip pressure. In this way the engine could be kept running quite slowly and yet kept hot. Just before starting for a flight new plugs were put in and the valve " lifters " removed. I might mention, that these lifters were all screwed on to a strip of wood as indicated in the accompanying diagram. I presume that your correspondent knows that Beardmore pistons get out of shape very easily, and if one cylinder oils up the piston might be examined to see if it is blowing. Nothing is more unpleasant than to hear an engine just " kicking " over each dead centre, but nothing is more important than to make sure that an engine is thoroughly heated right through before it is put under full load for any length of time. So n.any mechanics think it is enough to get the water in the jackets warm and then " let her rip." This hascaused a large number of breakdowns." J. W. (Bradford).—The internal drift wiring of an aeroplane wing is frequently in duplicate to give an increased factor of safety. Should one wire be broken for some reason, the other would take over the function. In any case the drift wire in each bay is always made amply strong, whereas the (ZL\ x \ JKileron. x anti-drift wire may be made lighter, although a reversal of stresses may occur which would render it advisable to have both wires equally strong. In normal flight the wires which take care of the drift are those shown in full lines in the accompany- ing diagram. The anti-drift wires are shown in dotted lines. B. S., Fl. Lieut. R.N.—A variable angle of incidence has been tried with excellent results, notably on the Paul Schmitt biplane, which established several world's records in the days before the war. The pros and cons of a variable incidence cannot be discussed in this column owing to lack of space,, but if you are interested in the subject we would refer you to a description of the Paul Schmitt biplane which appeared in " FLIGHT " of October 30, 1914, a copy of which can be obtained from our offices, the price being is. It is not, we think, advisable, as you suggest, to do away with the elevator, since a certain amount of elevator control will be necessary while changing the incidence. R. F. P. (Worcester).—For particulars regarding the American Air Service you should write to the Headquarters of the U.S. Military Mission, 30 Grosvenoi Gardens, S.W. A. O. W. (E. Dulwich).—You should write as directed above. Cadet (Oxford).—Army Council Instruction No. 28 of 1918 authorises an advance of £9 for each officer cadet to be expended on clothing under the orders of the O.C. the cadet unit, who will arrange for the supply. On being commis- sioned cadets will draw £41 outfit allowance instead of £50. French Air Champions. IT has been announced in Paris that of the nine German machines brought down on February 3rd, six were brought down by three pilots. Lieut. Mahon now occupies the second place among the French aces with 22 Germans to his credit. Game Law for Aviators. SOME sporting aviators have already indulged, in the States, in the shooting of game from aeroplanes, and this has led the North Carolina authorities to pass a bye-law prohibiting the shooting of waterfowl above any of the waters of the state from an aeroplane. 176
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