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Aviation History
1946
1946 - 0927.PDF
MAY 9TH, 194b FLIGHT 477 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 accompany letters. No. 170 SQUADRON News of Photograph Wanted I WONDER if any of your readers, ex-members of 170 Squad-dron, Bomber Command, could help me trace a photograph of the squadron which was taken at Dunholme Lodge R.A.F. Station, near Lincoln, in November, 1944? It was the only one ever taken and, being unofficial, there is no record of it at the Air Ministry. British Red Cross. (Miss) FRANCES E. THOMPSON, M.S.R. THE MASTER CONTROL Official ConfirmationS ORRY, "Indicator," but Mr. Hall is right. The safety stops on the two undercarriage levers are interconnected by Bowden cable, so that the undercarriage can be raised from either cockpit. As if Miles Aircraft, Ltd., would overlook such a point! D. L. BROWN, (Miles Aircraft, Ltd.). [Several other letters have been received in which the' writers make the same point. On handing "Indicator" his humble pie for solitary consumption, he said, "Evidently I did an insufficient amount of back-seat driving."—ED.] FLIGHT OF BIRDS A "Brains Trust" Theory ChallengedI N a recent B.B.C. Brains Trust session the question arose why certain breeds of birds when flying, especially in migration, formate in squadron-vee, and the matter was disposed of by Dr. Julian Huxley. He completely tabooed the general notion that the birds always had a rightful and accepted leader and held that the reason is entirely aero- dynamic, i.e., that the birds get in close together and so reduce overall drag'when they are flying long distances and desire high speed. With all due deference to such an authority as Dr. Julian Huxley, I find this theory a little hard to swallow, and perhaps some others can throw light on the matter. STANLEY BRADSHAW. HEIGHT CONSCIOUSNESS . Experience of Helicopter Pilots TV/TAJOR "JIMMY" CORDES, that extremely experienced •'-''1. test pilot, tells me that when helicoptering above 2,000ft he is very conscious of height, and wonders if the direct down- ward view is responsible. Lying in the bomb aimer's glass- house, in various bombers at various heights, I have neither had the sense of height, nor heard of anyone who had. Sqn. Ldr. Arkell, who was the chief instructor at the R.A.F. helicopter school, used to get this height sensation at 5,000ft when helicoptering on radar work. He supports the down- ward-view theory, and says that bomb aimers may be spared because they are prone. May forward speed enter the argu- ment? And have we a cast-iron explanation for the lack ol the height sensation in fixed-wing flying? J. D. S. ALAN. REWARD FOR SERVICE And the Song They Sang at Halton '"THE letter by "Wing Co." in your issue of April 18th, has -*• its points. May I please be allowed to add a few words concerning ex-apps: to whom the officer's mess proved no cynosure or who for various reasons (often the realization of being able to pull their weight—and then some!—as W./O.s or S.N.C.O.s), were not commissioned under war emergency. Having (or electing) to seek opportunity, peace and settle- ment in civil life for which they have been fighting, and in- cidentally serving since school days, presents difficulties no less than for ex-Wing Co. Apart from the question of E.V.T., there is a general bar on ex-regulars benefiting under the Further Education and Training Scheme. This, in spite of the fact that skilled Service trade seldom qualifies in civil appli- cation ; witness, necessity for G.E.'s licences. For ail such (completion of 12 years plus), there ^s not the support of "/go p.a. or so" although, let it be noted, that for "Wing Co.," each year of service in the ranks becomes,by reason of being commissioned, valuable for half-rate officer's service benefit. This all reminds me of a song we loved to sing occasionallyat Halton—"Let's have a good cry," but such senti- ments are sometimes justified. KX-W/O. "SAM." "KEEPING THEM RUNNING" The Author Replies to a Critic THE communication from Mr. R. E. T. Hack Flight, April -*- 18th) is appreciated by the author'of the article in question and his letter necessarily calls for a reply. By virtue of Mt. Hack's apparent knowledge he has kindly amplified certain statements that were quoted, but which inevitably suffered brevity. However, it would appear that he has failed to appre- ciate that "Keeping Them Running" was written a» a generalization of servicing and maintenance on a variety of gas turbines and not confined to any particular design as his letter seems to imply. For those who service and maintain aircraft, it is a normal assumption that the determination of any faulty component has first been established, either by mental reasoning or investi- gation, before it is replaced, and such qualification may there lore be considered superfluous. The reference to r.p.m. "hunting" is presumed to be a supplementation, though in taking a cross-sectional analysis of fuel-system faults from a number of types, a more common cause for erratic operation is that referred to in the last sentence of his relevant para- graph, particularly where the fuel system incorporates a com- posite unit wherein the throttle valve and a.s.g. is fitted, the latter partly in lieu of an a.c.u. It is difficult to accept the statement that " practically every defect" falls under the heading of "power losses"; there are many defects which may arise, though seldom do, that have no direct bearing at all on power output, and while to the maintenance export the typical list of possible power loss causes may appear both elementary and obvious, such is not quite the case to the uninitiated. The phrase "aero- dynamic breakdown" was not intended to be confused with mechanical breakdown; the implication was to differentiate between the two. It is further observed that Mr. Hack is also in agreement with the author regarding the inverse efficiency of the com- pressor with respect to increased impellor/compressor casing clearances, and since it has already been inferred that rectifica- tion of troubles akin to this component necessitates a complete strip, Mr. Hack's remarks are further confirmation. It may certainly be said that propelling nozzle distortions on British gas turbines is a very rare occurrence, though all gas turbine designers have not enjoyed this success. For in- stance, certain German-built gas turbines, after extensive run- ning for the type, have shown a marked deterioration of the propelling nozzle assembly, from which inferiority pressure losses emanate and directly influence the propulsive efficiency. On the other hand the reference to detrimental effects from jet pipe gas leaks is sound and good advice. Regarding bearing troubles, perhaps "faulty" would have been a more suitable and comprehensive adjective and would have included such remote contingencies as partial seizures. One of the principal limitations to additional power from a given size unit is the maximum permissible temperature of the turbine moving blades. Thus any negative heat transfer that takes place from these blades will assist in permitting the maximum operating temperature to be increased, potentially raising the power output—provided, of course, there is no undue sacrifice iu the turbine efficiency or overall performance of the engine. This is one of th^e primary reasons why some designers have advocated and used hollow static and moving turbine blades. The temperature of such blades is normally influenced by cooling air being ducted from the stator ring inner flange assembly and the periphery of the turbine disc to the outer extremities of the fixed and moving blades, finally exhausting into the main gas stream, heat transfer being effected mainly by convection. Experience has shown that if and when such turbine cooling systems fail, the jet pipe tem- perature will respond to the occasion. The rear bearing cooling air is an entirely separate issue. R. M. CRACKNELL (Sqn. Ldr.).
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