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Aviation History
1946
1946 - 0633.PDF
MARCH 28TH, 1946 FLIGHT 325 CORRESPONDENCE The Editor does not hold himself responsible for the views expressed by correspondents. The names and addresses of the writers, not necessarily tor publication, must in all cases accompany letters. STOP PRESS A Jet-propelled Locomotive I LONDON, March 6 (UP).—The Great Western'Railway is studying con-struction of locomotives based on the jet-propulsion principle, it was disclosed to-day.PLEASE note the above clipping, from a U.S. daily paper. I can understand a gas-turbine locomotive, but I certainlyi can't understand a jet-propelled locomotive. ' About a year ago one of our officials wanted to know howmuch horse-power was required to operate a full-sized train by the use of jet propulsion. My calculations, which were veryrough, estimated it would require at least 50,000 h.p. for the principal reason that the maximum speed of the train would beonly 100 m.p.h. or thereabouts, and there would be a tremen- dous amount of "slippage" in the jet stream as compared tothe surrounding air. Of course, a gas-turbine locomotive with a conventional transmission would take about 5,000 h.p. forthe same train. • R. T. S. New York. CASE AGAINST HEATHROW Presturick's Better Weather Record REGARDING "Kibitzer's" mention (Flight, March 14th,1946) of Heathrow's "man-made haze and fog," I would point out that Prestwick Airport does not suffer from visibilityso bad that the airport has to be closed to any appreciable extent (two closed days in the year). The conditions at Prest-wick are phenomenally good and possibly are not equalled on the western seaboard of Europe. I would like to say that I am surprised, to put it mildly,that you persistently ignore the various advantages of Prest- wick over Heathrow. HECTOR SOUTTER. LONG-DISTANCE RECORD Fuel Consumption of the Wimpey WITH reference to the two letters by Mr. J. L. Coverdale(Flight, February 7th and 28th), I must join with your contributor, Mr. R. G. Lofting (Flight, February 28th) in querying the load and range figures tabulated by Mr. Cover- dale. • I am not personally acquainted with the cruising figures ofthe Lancaster I, but I can assure him that he would not manage 24 gall / engine / hour on his hypothetical long-range" Wimpey." At its operational weight of some 34,000 lb, optimum cruis-iug consumption of the Wellington lc was 30 gall /engine /hr. At the all-up weight suggested of 39,700 lb, of course, thisfigure would worsen somewhat. It would also appear that at this wing loading (47.2 lb/sq ft)and power loading 19.8 lb/h.p., a pretty generous length of runway would be indicated, as the "unsticking" speed wouldbe in the neighbourhood of 105 m.p.h.. J. C. ELKINS. FUEL AND WEIGHT A Problem in Consumption Rate WONDER if any of your readers could answer the followingquestion. The problem concerns two heavy bombers; B-24S the same mark and both equipped with " Ceco " carburet-tors. Both aircraft take-off on a range-flying exercise; air- craft "A" weighs 52,000 lb and aircraft "B" weighs62,000 1b. Both aircraft use the power settings of " auto- | lean mixture, 32m m.p., 2,200 r.p.m." I I maintain that if the power settings are not changed both I aircraft will consume the same quantity of petrol per hour.I Naturally, aircraft "B" will arrive at base later than "A" I because of its heavier weight, and, consequently, decreased? i.a.s. I, therefore, come to the conclusion that both machines use the same number of gallons per hour, but that aircraft"B" has a lower a.m.p.g. and consumes more petrol. My late Flight Engineer Leader believes that aircraft "B "must consume more gal / hr—even though both " A" and "B" maintain the same power setting—because it is theheavier of the two. Both engineers and the Pratt and Whitney engine technicalrepresentative agree with me, but he still remains stubborn. it Could anyone enlighten me? "MIVTTn r" ON BEING C.G. CONSCIOUS A Simple Means of Checking Load THE letter in Flight, March 7th, by John Howard, under•^- the above heading, suggests to me that there is a very simple and efficient means of preventing overloading or badloading of any aircraft. If a pair of weighbridges is arranged so that the main wheelsof an aircraft can rest on one bridge, while the tail or front wheel is on the other, then the total weight of aircraft and loadwill be the sum of the two weighbridge readings. Overloading will be apparent if present. The proportion between the two readings must be constantfor a given aircraft, no matter what the load, if the C.G. is to be maintained in its correct place. C.G. Taking moments about the C.G. \\\.x = Wt.y then W_, _ v W~2 ~ 7 W, = wt. on main wheels. W2 = wt. on fore or aft wheel. y Now — is a constant for any aircraft, since the position oix the main and fore or aft wheels and the C.G. are fixed.It follows that for any given aircraft the wheel loadings should bear a constant proportion whatever the total weight,and this figure could be clearly marked on the aircraft, and would be as important to the machine as is the Plimsoll lineto a ship. By using two weighbridges the cargo could be arranged inthe best position and readings would instantly show when the aircraft was safe.Technical difficulties in laying out weighbridge equipment to suit the varying wheelbase lengths could no doubt be over-come, and the cost of such an installation would be negligible in comparison with additional safety ensured. W. G. HARROW. 'MIXTURE.' Best Position for the Datum Point WHILE fully agreeing with Mr. Howard's views as to the'necessity for the utmost care in loading transport aircraft (Flight, March 7th), I cannot help feeling that these proposedsimplifications are likely to make matters even more contusing The suggestion to rename the datum "balance point"brings to mind the story of the pilot officer who, when asked to define "the centre of gravity of an aircraft," replied: "Itis a point usually indicated by a white cross on the side of the aircraft." The term "balance point" suggests that the air-craft should balance at the indicated spot, and I hate to think of the number of P/Os who would then confuse the centreof gravity with the datum point, possibly with disastrous results if they loaded their aircraft to this point. While in theory Mr. Howard's suggestion of placing thedatum point at approximately the centre of the cargo space may be good, in practice it is often impracticable and in anycase it is undesirable. If the correspondent has ever been present at the weighing of an aircraft he will understand theneed for having the datum at a point from which a plumb-line can be dropped to the floor without fouling the wing, which itnormally would do if the datum were placed at the cargo centre of a low-wing monoplane. It is undesirable to have the datumpoint at the centre of the cargo hold owing to the introduction of positive and negative moment arms and moments, and I needhardly emphasize what might be the result of a " minus sign " being overlooked. Undoubtedly the best position for the datum of a transportaircraft is at the front end of the cabin in order that the ground crew can measure the moment arm of any item of cargodirectly, regardless of its vertical or lateral position in the cabin. Using this datum will, in most cases, result in all
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