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Aviation History
1942
1942 - 2684.PDF
698 FLIGHT DECEMBER 24TH, 194* Correspondence * The Editor does not hold himself responsible for the views expressed by correspondents. The names and addresses of the writers, not necessarily for publication, must in all cases acconipany letters. THE TORPEDO BOMBER Beaufort or Beaufighter TF I may, I should like to question a statement in Mr. R. •*• Hudson's letter in Flight of December 3rd. He says that the armament of the Beau-fighter is purely offensive, but I think I am right in saying that some of these aircraft did have gun turrets in place of the usual astro-hatch. In any case, it would be comparatively easy to fit a turret. Bearing that in mind, I am more than ever of the opinion that the "Beau" would make a very good torpedo-bomber. No doubt, if time were taken, a better specification could be worked out, but when our apparent policy is (wherever possible) to adapt types, it seems the Beaufighter has enough of the qualities now required in torpedo aircraft to make it worth while being given a trial. I say very hesitatingly that it is withjn the bounds of possi bility to operate this type from an aircraft carrier. But, if this is not practicable, it would still do well as a land-based machine. I do not know how much better it would be than the Beaufort, but I cannot, on superficial examination, discover any marked disadvantage compared with its sister-type, and it has the obvious advantage of speed, manoeuvrability and armament. '' AERO.'' FAULTY FILMS Errors in Newsreel Comments MAY I be permitted to add my bleat to the current criticisms of aircraft recognition in films. I have this week seen British Paramount Newsreel's version of the North African landings, and was much impressed. But when photographs of a captured airfield are shown, and the c6mmentator refers to an elderly Dewoitine air liner as a Junkers 52 troop carrier and a Potez 63 as a Me. fighter-bomber, I suggest that is slightly stretching things. Also in the early stages of the in vasion of the East Indies, I remember seeing a newsreel show ing what I should say was a Netherlands East Indies Dormer Do. 24 doing patrol duty, and the commentator blandly talked about Catalinas. Dare I risk one more poke? In the M.O.I, film "Royal Observer Corps," a plane is shown crashing after raiders have been turned back from their objectives. The plane is leaving a trail behind it and crashes out of sight behind some houses, but what struck me most of all was that the outline, rather dim, was very much like that of a Spitfire ! Now tell me, am I being too much of a realist, or am I just seeing things? Ordinary films might blunder on recog nition, but surely newsreels and M.O.I, films' should be accurate. Here's hoping. H. SNELGROVE. P.S.—Have been ,a regular reader for several years now. Should like to congratulate you on the maintenance of your highly interesting journal de'spite, doubtless, restrictions'and difficulties. H. S. AIR TRANSPORTS Their Value to the Army in Africa THE recent actions in North Africa show, and emphasise J- perhaps better than any previous arguments have done, that there is a great need for aircraft of the transport type, both for short-range tactical work and also as high-speed carriers of freight from bases in Britain and America. We have been told that production of such a type has started in this country and we know, of course, that the U.S. is well advanced in this respect. It is therefore the responsibility of the Powers-that-Be to see that we build up, in.the near future, an adequate number of these aircraft so that we have a rapid means of transport for troops when the need is sufficiently great, and for vital supplies to be brought up to the forward fighting areas. Land and marine types will be. necessary, although the latter appear to be more suitable for building as regards increased size and quick production, and also in view of the fact that flying-boats require less ground organisation than similar land aircraft. Now that we have occupied large portions of West Africa it is certain that there will be much scope for these machines in connecting up communications to Britain. The distance is not too great and should in fact enable them to be used to best advantage. It should also be possible to supply them with fighter protection the whole way if this were necessary. In the Mediterranean theatre, too, it would be great strategic value to have a fleet of big transports, ordinarily used for routine duties, but ready in an emergency to move compara tively large numbers of troops in little or no time. This is especially so when we can gain such decisive air supremacy as the Eighth Army has had over Rommel's forces in the past few weeks. In Africa, under such an umbrella and with a few hundred transports, we could soon have moved enough trpops and equipment to overwhelm the original German paratroops force landed in Tunisia. The enemy saw the wisdom in this method and used Italian Savoia8is to carry German troops. Fortunately for us the Germans did not possess air supremacy. The result was that'W the six of them were shot down with the loss of over 200 mc~»jl» Possibly they had not even a small fighter screen lor protec tion. With adequate air cover the whole situation would be altered. There is no reason for the transport to remain continually as such; it could also be used for long-range reconnaissance. Up to the present much of the tardiness in adopting the type for large-scale use has been due to the need to concentrate on "more war-like" aircraft in the belief that transports are not essential. Neither are they to the Air Force, but in the Army they should be regarded as every bit as necessary as tanks and guns. Only when such a state of affairs is accepted will our Army obtain the fullest possible measure of mobility. CLYDE. BOOST PRESSURE VARIATION Why Reduced Piston-load Raises It BEING concerned with the design of aircraft engine boost control units, I am in a position to offer your correspondent "Puzzled" (Flight, Nov. 19th) some enlightenment on the reasons why the boost pressure may vary from a pre-set value when the speed of the engine is changed. As air is drawn past the throttles into the engine, a torque is produced on the throttle spindles tending to close them. If they are to be maintained in an open position, a counteracting force must be supplied by the boost servo piston to oppose the closing torque. This force is created by a pressure differential across the piston, and obviously the pressure difference will vary with changing loads. The fsiston does not effect a perfect seal in its cylinder, and consequently the working fluid is in duced to flow past the piston to the low pressure side. ' In order that this flow can be accommodated, the servo valve of the boost control must be displaced from the neutral position to expose sufficient area of the controlling ports for this pur pose, the amount depending upon the rate of flow past the piston. If, now, we imagine the boost control unit as being set to control at a particular datum boost when the torque exerted by the throttles is at a definite value, then it is apparent from the reasons given that the valve will move to a new positii^ if this value is altered. Since the valve is attached directly'f& the boost responsive bellows, it follows that the new condition can only be achieved by an alteration in the boost pressure applied to the bellows. If the load on the piston is reduced, the boost pressure must increase slightly to move the valve towards the neutral position, i.e., in the direction that would normally close the throttles. As mentioned already, the torque is produced on the throttles aerodynamicallv, and this decreases as the mass air- A flow into the engine falls off. Hence, when the engine revs are f pulled down by coarsening the airscrew pitch at a given boost setting, the mass flow will decrease with a consequent reduction of the throttle torque. For this reason the boost will rise when the engine speed is reduced. The extent to which the boost will vary depends upon* certain features in the design of the unit and in particular upon the pressure rate of the bellows and the shape of the controlling ports. L. S. GREENLAND.
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