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Aviation History
1918
1918 - 1293.PDF
NOVEMBER 14, 1918 CORRESPONDENCE:. The Relative Inflammability of Dopes [1968] In certain newspaper reports on the findings of the sub-committee appointed to investigate the contract of the British Cellulose Company, reference is made to the Air Board sending out an inflammable substitute for cellulose acetate dope owing to the shortage of the latter. This state- ment cannot in fairness be made by anybody with a know- ledge of the facts, for to my knowledge at least the majority of the dope sent out, apart from cellulose acetate dope, was at least as little inflammable as the cellulose acetate variety and it undoubtedly afforded a better resistance to ignition of the wings by " tracer " bullets and other incendiary methods of firing aircraft by means of the fabric. The question of the relative danger from inflammability of dopes has never, to my mind, been properly dealt with. In the Specification known as D. 101 of April, 1918, drawn up by the British Engineering Standard Association, a " method of testing the inflammability " and a " method of measuring the rate of burning " is laid down. The test of the former is to place a small cube, 4 mm., of celluloid on top of the fabric and to ignite the cube. Tt is stated that " the celluloid cube shall not produce more than a slight charring and the fabric itself shall not ignite." The man in the street would naturally ask why a cube of this specified size should be taken and why the size should not be increased until the fabric does ignite. As regards the method laid down under the above speci- fication for measuring the rate of burning, which is to ignite the edges of a hole in the fabric and to measure the time taken for the flame to travel, one cannot take exception to this except that it might be suggested that if the stringency of the test for inflammability were increased, the dope that offers the better resistance to ignition should have the preference over one that burns at a slower rate, for when the fabric of an aeroplane wing is once aflame, it if does not blow out, the aviator has a very small opportunity of getting to earth in safety. My object in writing to you is to suggest a more efficient method of testing the danger from inflammability. To arrive at the correct relative values of dope in this connection, the following tests should be made :— (1) Facility with which flame is put out by the wind, assuming the fabric to have ignited. (2) Resistance the dope offers to ignition. (3) Rate of burning if and when the fabric is ignited. I have placed the qualities roughly in their order of im- portance. If a dope offers a greater resistance to flame, it may, as a general rule, be said that it is better than a dope that offers a less resistance to name even though the latter burns slower, for the reason that when the fabric is once, ignited the short time it takes the wings to burn gives the pilot insufficient time to reach the earth. Secondly, if the burning is of such a nature that it is easily extinguished by the wind, it will, in turn, be seen that such a dope, even assuming it to ignite more readily, is probably of greater value than one which is harder to ignite but does not blow out by the wind so readily. To my mind the great disadvantage of the cellulose acetate dopes in this connection is that they melt from the heat, and they are, in consequence, the most difficult to put out when once ignited, though, no doubt, something can be said in their favour in connection with the third quality, i.e., rate of burning, as they perhaps burn a little slower than a type of nitro dope made on the lines of " Titanine." The latter, however, offers a greater initial resistance to flame and also has the advantage of being readily extinguished by the wind. Until the Air Board lay down a definite standard for tautness, all comparative dope tests have their value limited. Given a definite standard of tautness the fireproofing quality can, with certain types of dope, probably be increased-without overstepping the limit. In testing dopes for inflammability, they must obviously be applied on double-sided frames so as to produce, as nearly as possible, the conditions of an aeroplane wing. These frames, should if-possible, be moved quickly through the air during the process of sending incendiary bullets through them and as much more efficient methods of incendiary attack will, no doubt, be found should the War be prolonged, one should not necessarily limit this to the incendiary bullets at present in use, but should increase the stringency of the test so far as to ensure the ignition of the fabric. This would definitely decide which dope offers the greatest resistance to flame, and would show whether the wind caused by the current of air would extinguish it. Personally, I have always been of the opinion that itis not generally realised what a vulnerable target the fabric of an aeroplane wing affords. It is a common thing to read ofmachines that have had upwards of 30 or 40 bullets through the wings returning to their base without discomfort. Shouldany one of these cause the fabric to ignite, however, the machine would be doomed. I am sure I have no wish to seethe " Hunlike " methods of fighting by liquid flame, &c, &c, increased, but if we wish to retain our supremacy of the airwe must be prepared for all eventualities, and by realising exactly what might be done against us, we should best beable to take the most effective precautions and counter- measures. To my mind there is no reason why Qur aero-planes should not be sent out capable of resisting much more effective media for conveying flame through ignitingthe fabric than the present tracer bullets. One might readily predict that if the necessity for this does not arise in thepresent War, it is bound to in the next (God forbid !). I have limited my remarks to the possibility of settingmachines on fire through the medium of the doped fabric. Ignition of the petrol through a tracer bullet penetratingthe tank is quite another matter, and one that I must leave to others to deal with. The petrol tank, however, does notoccupy more than 1 per cent, of the area of the machine, whereas fabric occupies more than 90 per cent, of it. T. W. H. WARD,_ Managing Director, Titanine, Ltd. Aeroplanes after the War [1969] With the prospect of an early Peace, bringing,as it must do, the post-War manufacture of aeroplanes, we think your Journal could be of invaluable service in assistingmanufacturers generally to get down to serious business. For the past four years, the industry has been producingmachines for War purposes. Under the guidance of the Air Ministry, manufacturers to a large extent have produced,without reference to one another, planes, engines and acces- sories to requirements laid down by this authority, but wefeel that for commercial purposes, as soon as this control is removed, unless some definite standards are set up, we shallget such a multiplicity of ideas in each of the three branch mentioned, that considerable time will elapse before anyrecognised standards are reached. Bearing this in mind, we, as being interested in the manufacture of engines, askedthe leading plane builders for their opinions of their likely requirements of post-War engines. Without exception,our efforts were met with all possible courtesy and interest, but we were surprised to, find that such a great diversity ofopinion existed as to use, size, power and type of machine that would be used. We respectfully suggest that your Journal should invitea controversy on the subject, to be followed by a summary, to find out what are the broad lines that would ultimatelybe followed, and establish, if possible, some such standards as :— 1. Types of aeroplanes. ' 2. Horse-power of engines. 3. Engine fixture dimensions. * 4. Propeller speeds. _ 5. Ranges of Propeller bosses. '~ * 6. Fittings. ~7. Instrument boards. We do not suggest that this list is in any way complete,but includes just a few items that occur to us. By this means, the manufacturer of aeroplanes knows that he has availablea selection of engines and accessories which can be embodied without alteration to the design of his machine, and an enginebuilder knows that his engines will fit into a number of makes of planes, and so on. We instance the motor car industry. For years, themanufacturers of chassis designed absolutely regardless of the body builder, and when the body had been fitted, theunfortunate purchaser used to hunt for various places on his car to fit accessories. We feel that we may be criticised on the ground that thesuggestion is one that might hinder progress and perfection, but we suggest that the great aim of all manufacturers,during the trying period of reconstruction, will be to get down to a Peace basis as quickly as possible, thereby minimisingdisorganisation of labour and consequent unemployment. After this has been attained, future development could beconsidered. p.p. THE SELSDON AERO AND ENGINEERING CO., LTD.,G. CAMPLING, Managing Director. Sanderstead Road, Croydon, Surrey, November 8th. I294
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