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Aviation History
1917
1917 - 1167.PDF
NOVEMBER 8, 1917. of the Hm OFFICIAL NOTICES TO MEMBERS FLYING SERVICES FUND. MEETINGS of the Committee of the Flying Services Fund Wereheld on Wednesday, September 19th, Monday, October 8th, and Monday, November 5th, 1917. Present: Major T. O'B.Hubbard, R.F.C. (Chairman), Mr. Chester Fox and Squadron- Commander C. E. Maude, R.N. In attendance Lieut.-Com.H. E. Perrin, R.N.V.R. An allowance of £1 10s. per week for six months wasgranted to the widow of an aircraftsman in the Royal Naval Air Service.An allowance of 15s. per week for six months was granted to the widow of a 2nd Class Air-Mechanic in theRoyal Flying Corps. A grant of ^io was made to a 1st Class Air-Mechanic inthe Royal Flying Corps who had been injured on active service. A grant of £$ was made to the widow of a Sergeantin the Royal Flying Corps pending the consideration of her case for a weekly allowance.A grant of £5 was made to a Petty Officer in the Royal Naval Air Service who has been incapacitated. THE FLYING SERVICES FUND, administered by ' THE ROYAL AERO CLUB. THE Flying Services Fund has been instituted by the RoyalAero Club for the benefit of officers and men of the Royal Naval Air Service and the Royal Flying Corps who areincapacitated on active service, and for the widows and dependants of those Who are killed.The fund is intended for the benefit of all ranks, but especially for petty officers, non-commissioned officers andmen. Forms of application for assistance can be obtained fromthe Royal Aero Club, 3, Clifford Street, New Bond Street. London, W. 1. Subscriptions. £ s. d. Total subscriptions received to Nov. 6th, 1917.. 12,470 17 9 H. E. PERRIN, Secretary. 3, Clifford Street, New Bond Street, W. 1. ANSWERS CORRESPONDENTS [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 inour columns. Full name and address, which will not be published, must always be given.—ED.] A. H. (Bickley).—We have not hitherto heard of thephenomena you mention, i.e., that a bomb launched from a " pusher " should have a tendency to fall at an angle towardsthe nose of the machine, and that one launched from a tractor should tend to fall in a rearward direction. We can scarcelybelieve that this could be the case. Obviously the bomb, at the moment of release, is travelling at a horizontal velocityequal to that of the machine, and this would, of course, apply equally to both types. The only other force to which thebomb is subject, apart from the action of gravity, is the wind. In the case of a tractor the velocity of the air relatively toparts in the slip stream Will be somewhat higher than that of parts outside the slip stream. Possibly it is this fact whichhas given rise to the idea that a bomb launched from a tractor should have a tendency to travel in a backward direction.This is, of course, assuming that the bomb is carried on some part of the body or wings which lies inside the slip stream.The slight difference in velocity would, however, be negligible as far as its effect on the path of a bomb is concerned. Withregard to the " pusher " there would not appear to be any reason to suppose that the dropping bomb would travel alongany other curve than that followed by all bodies dropping from a height and having an initial horizontal velocity—i.e.,it would follow a parabolic curve. F. H. O. (Norwich).—A tail plane, in order to be non-lifting at o° incidence, must be of symmetrical section, i.e., either flat or double cambered. On modern high-speedmachines the flat tail plane is not extensively employed, chiefly because at small angles of incidence the resistance iscomparatively great, and also owing to the fact that such a thin structure—if the tail plane be of any considerable area—is not very strong and requires a fair amount of external bracing, which further increases the resistance. Sometimesdesigners employ a section having a flat bottom surface and a cambered top surface. This is usually done in order to neu-tralise the effect of a down draught on the tail plane caused by the deflection of air from the top main plane. Since, however,you specify that the section must be non-lifting at o° incidence such a section cannot be employed, as it would have to fly at all in order to give no lift. There then 1167 remains the double cambered surface which is symmetricalabout its chord line. In some recent German aeroplanes— as the Albatros D II—such a plane is employed, which is ofvery considerable thickness in proportion to its chord. Some tests carried out for the Curtiss Aeroplane Co. at the Massa-chusetts Institute of Technology on a tail plane of aspect ratio 4, and of a maximum depth or thickness of nearly .09 ofthe chord, indicate that such a tail plane has quite a low resistance, a fairly good lift, and a very small travel of thecentre of pressure. The following table giving lift co-efficients and drag co-efficients (in lbs. per sq. ft. per ft./sec.) shouldprovide you with the information required :— Angl e o f incidenc e 0 2 4 Dra g co - efficient . .000017 .000018 .000025 Lif t co - efficient . 0 .00017 .00032 Angl e o f incidenc e 6 8 10 Dra g co - efficient . .00004 .000064 .00011 Lif t co - efficient . .00045 .00059 .00072 Angl e o f incidenc e 12 1416 Dra g co - efficient . .00017 .00023 .00028 Lif t co - efficient. •00084 .00088 .00089 The section tested was of the following curvature :—Dist. from leading edge, per cent, of chord.. o 20 40 60 80 100Thickness per cent, of . chord .. .. o 7.92 8.75 7.00 3.72 0.42 N. H. B. (Rothley).—Without wind tunnel tests on a modelof the body it is impossible to say exactly what would be its resistance at 60 m.p.h. A fair estimate, however, would appearto be about 15 lbs. It should be remembered that this is the resistance outside the slip stream at 60 m.p.h. Inpractice, as the body is designed for a tractor, this resistance will be somewhat higher. How much higher will depend onthe slip at which the propeller is running. For purposes of approximation it may be assumed that the resistance ofthe body will be ij times as great in the slip stream. For the body in question, therefore, the resistance, allowing forthe effect of the slip stream, may be estimated to be roughly 22 lbs. We have no figures of the weights—empty and loaded—of the Gotha and A.E.G. twin-engine machines. From laboratory tests it appears that there is no advantage, aero-dynamically, in a backward stagger; on the contrary there appears to be a slight disadvantage. When, in spite of this,it is sometimes employed on aeroplanes the reasons are practical ones, such as giving the pilot a better view in a for-ward and upward direction.
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