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Aviation History
1910
1910 - 0833.PDF
OCTOBER 8, 1910 I shall be glad to give a more detailed explanation, with drawings, to amyone engaged in constructing flying machines. Ilchester. H. D. CAREY. DIHEDRAL ANGLE. [797] Being very interested in the discussion re the dihedral angle, with your permission I should like to throw more light on the matter. The air exerts a pressure, P, mainly normal to the surface, which by the resolution of forces is equivalent to the two components, P1 and Q, acting vertically and horizontally respec tively. When the machine is in stable flight, the forces on either plane are equal to one another, each to each, as shown in Fig. I, but in the event of the angle, 0, diminishing, as seen in Fig. 2, the vertical component, P1, on the lower plane becomes greater than P1 on fhe higher plane, tending to right the machine. Also it is seen that the component, Q, acting horizontally on the latter, is greater than Q acting on the former, and it is this excess of pressure that causes the machine to drift in the direction, R. It seems to me that a machine having its wings set at a dihedral angle would experience considerable difficulty in turning corners. With the centres of pressure of either wing situated at P, and the weight, W, acting vertically downwards at the junction of the wings, the arrangement appears to be equivalent to a machine having its wings in one plane and the centre of gravity situated at some distance below the centre of pressure. The machine would then be in complete accord with the laws of pendulum, and as in turning the machine cants over to the inner side of the curve, the weight, W, is continually tending to restore the machine to its horizontal position, thus hindering the turning movement. If the theory is correct, an aeroplane such as the R.E.P., i.e., having the e.g. above the c.p., would be able to take a sharp turn with ease. Being only an aspiring amateur, I shall be only too pleased if someone more experienced in matters aero nautical than myself will step in to correct me if my theory proves to be wrong. Coventry. " ASPIRING." PARACHUTES FOR PILOTS. [798] Is it not possible, with a view to the prevention of fatal accidents, for an airman to have some kind of parachute attachment which could be made to work in the event of a fall ? This might be possible in a monoplane where the pilot has no obstructions above him, and when an accident occurs at a great height he might have time to get the appliance to work. " CAUTIOUS." [The idea of providing pilots with parachutes as a possible source of safety in the event of a mid-air calamity does not commend itself to us, because, in our opinion, the aeroplane itself is inherently the safest form of parachute that the pilot or his passenger can have, and they had much better trust their lives to it up to the last than to abandon their posts, and rely upon an apparatus that might quite as easily fail them in an emergency. We are very strongly of the view that there is no justification for any mishap in mid-air that is brought about by the structural failure of the machine, for we contend that manufacturers simply must build aeroplanes strong enough to with stand any stress put upon them in flight. It is a fact, now well demonstrated, that the stoppage of the engine is a contingency that a good pilot is prepared for, and it will not of itself be the direct cause of disaster. The aeroplane is a natural glider if properly handled. There remains, of course, the other source of danger that lies in the inexpertness of the pilot himself, which could never be properly set off by the addition of a parachute. Assuming that the pilot is a master of his art, and has been flying sufficiently high, we believe that he should be capable of making a gliding descent under any contingency that does not involve the fracture of some essential member of the machine. It may be, of course, that he will be unable to select a landing place that will give a perfectly safe descent, but, on the whole, the chances are in his favour, and we think that a wider recognition of the necessity of being able to land on rough ground will lead to the construction of more machines with skids, or other suitable devices, that will very largely minimise the entirely unnecessary risk that a pilot now runs when he is unable to land on smooth turf.—En.] BUOYANT AEROPLANES. [799] Being a regular reader of your valuable paper, I take the liberty to write you, asking your opinion with regard to an aeroplane I am thinking of constructing. The idea is a combination of the dirigible and aeroplane, each wing of the machine made like a Bleriot, only double-surfaced, the interior between the upper and lower skin to be formed into cells into which hydrogen is forced. This method would give you all the lift of an ordinary dirigible, and yet do away with the great head resistance caused by the gas-bag. By this means I think that it is possible to make a machine about one-half the span of the ordinary machine capable of lifting the same weight ; and because the cutting edge is reduced by about half, the power required to force the machine through the air could not be much more than 4 or 5 h.p. The gas required would be just sufficient to bear the weight of the machine and motor, or if more, it could be easily ballasted down to get the proper lift. The ad vantage of building the wings up in cells would be, in case of an accident, there would be a chance of not losing all the buoyancy at the same time as if the wing was simply hollow and filled in one compartment. This idea would not cause any great alteration of the shape of the present type of wing, as it could still be made in stream-line form. I am sorry to encroach on your valuable time, but I should be pleased to hear the opinion of yourself and readers who may be interested. Also kindly let me know if this idea is new, or has it been tried before? and, if so, with what success. Llandrindod Wells. M. BAKER. [The idea of filling the wings of an aeroplane with gas lighter than air has been frequently advocated, but we suggest that our correspondent makes a very simple little calculation in order to see how far the internal capacity of the wings of an ordinary aeroplane goes to meet the volume of gas required for its support. As a basis of calculation we would suggest that the load to be lifted is reckoned at 1,000 lbs., and for the purpose of approximation it may be assumed that hydrogen will lift 74 lbs. per 1,000 cub. ft. If the machine is to be buoyant about 13,600 cub. ft. of gas will be required.—ED.] CHAUVIERE PROPELLER. [800] Experiments have shown that a curved leading edge and a straight trailing edge give a more concentrated slip stream than a straight leading edge and a curved trailing edge. Most marine propellers have blades sloping backwards giving a still more concentrated slip stream. By means of a lighted taper I found that air was drawn in from the sides as well as the leading edge in the Chauviere type, but not in its opposite. This rather points to air being thrown off and drawn in in a tangential way. Newcastle. C. IAN BUKRELL. BRAKES ON AEROPLANES. [801] Replying to letter No. 746 in FLIGHT, from Mr. A. G. Pugh, Bootle, re. brakes for aeroplanes, I see no reason why brakes should not be fitted to wheels of aeroplanes. I myself have an idea for one, and am at present experim enting with it on a model. It he looks at the constructional details of the new Curtiss biplane, published by you recently, he will see th e foot brake used on that machine. Glasgow. AMATEU R. i
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