FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1951
1951 - 0466.PDF
292 POWER versus WEIGHT... off rapidly to zero. The mass-flow evidently suffered from thelimitation produced by choking at the throat of the exhaust nozzle. The overall efficiency of this almost perfect machine did notgreatly exceed 0.30 to 0.35, values which were in themselves remarkable, but which would, in fact, be appreciably lower owingto unavoidable losses, particularly those associated with com- bustion. The lecturer pointed out that the external drag of thefaired body, wave drag and friction drag had been included in estimating the effective thrust F=<t>s. It was important in thisconnection that the internal thrust of this supersonic body was appreciably different from the kinetic thrust or change ofmomentum of mass-flow through the machine. Although the lightness of the ramjet was of primary importancein the struggle of power against weight, this advantage was very soon counteracted in transonic flight by a very high specificconsumption. As an example, the effectiveness of the ramjet could be compared with that of the turbojet with re-heat in stratosphericflight for maximum range at M= 1.5. Both jets were operated at the same and obviously excessive gas temperature of 1,500 deg C.at the entrance to the exhaust nozzle. Denoting by a dash all the symbols relating to the ramjet, theformula for effectiveness in maximum range flight showed that, at a given speed V, the turbojet would better the ramjet in "propulsiveweight" as soon as the ratio A/V was greater than (p-p')l(y' - y). In the case considered, which was at the limit of transonic flight FLIGHT, 9 March 1951 Fig. 5. Temperature effect on specific thrust and overall efficiency of a ramjet for various Mach numbers. 52O 10 I i1 Ifml Aid/A p* (/ \ f i 1 V r ?.' J • *—* *\ v-;'^'5- i (V= 1,000 m.p.h.), thefollowing values could be assumed: ply— 0.4 hr;p'=o.4p and y' = 2.sy, so that, under the samepower, the turbojet with re-heat would surpass theramjet after 0.4x0.6/1.5 =0.16 hr, that is to say,after ten minutes of flight. Take-off and acceleration requirements as well as climb to thestratosphere were also to the disadvantage of the ramjet. Take-off, climb and flight through the transonic range depended funda-mentally on the accelerating power at all intermediate speeds. Upon this was based, in fact, the judgment of experience withwhich theory had to agree, because it was experience that refereed the contest of power against weight. 10 2-0 3-O 4-0 LT. CDR. G. T. WEEMS, U.S.N. THE death occurred at Delaware recently, following an acci-dent to an experimental light seaplane, of Lt. Cdr. George T. Weems, a test pilot of the U.S. Navy. "Bee" Weems, who was29, completed No. 8 course at the Empire Test Pilots' School, Farnborough, in December, 1949. Through his personal efforts,the course was enabled to visit the Coral Sea in the Mediterranean —and a visit to an American carrier is now part of the E.T.P.S.syllabus. During the war, Lt. Cdr. Weems served in the Pacific, as an'ensign aboard a destroyer and later as a carrier-based fighter pilot. His awards included the Silver Star, American D.F.C. and onegold star, Air Medal and four gold stars and a Presidential Cita- tion. His post-war career included a tour as navigator of the car-rier Breton and a period as a test pilot at Patuxent. Recently he became the first U.S.N. officer to qualify for paratroop wings, andhe flew a number of missions on fighters from Japan and Korea. His father, to whom his friends in this country will extend sym-pathy, is Capt. P. V. H. Weems, an authority on navigation. NOTHING NEW UNDER the title A Century of British Engineering, a lecturewas delivered to the Royal Society of Arts on Wednesday, February 28th, by Mr. W. T. O'Dea, B.Sc, M.I.E.E., Keeperof Aeronautical Collections and former Keeper of Engineering Collections at the Science Museum. His themes were thatengineering, contrary to popular belief, has increased the extent to which skill is required of the worker; that it has removed much ofthe unpleasant labour from industrial processes; that the machine has created employment and has raised the standard of living;and that the failure to use machinery to the maximum advantage imperils those standards. The lecturer said that mass production had become so asso-ciated in the modern mind with the present age that it was appropriate to explain that all three modern varieties, in primitiveand very restricted form, were known a century ago. "If mass production means producing numbers of similar objects notnecessarily to the highest degree of precision, it was achieved by Brunei and Bentham in 1804-8," he said. "They devised a seriesof machines that produced in a year 130,000 naval pulley-blocks when operated by ten unskilled men. The same output, formerly,would have required no skilled block-makers. "If, however, by mass production is meant the assembly oflarge numbers of any product by use of a random selection from interchangeable component parts, the work of Whitney and Northin the United States on musket production had been proceeding for half a century before Colonel Colt brought it to an almostmodern-looking stage at the Colt Armoury, which was nearly finished, after four years' building, at the time of the 1851 Exhibi-tion. The basic principle of production was the use of limit gauges to control the interchangeability of component parts. "If, to defend the modern pride in mass production we are tofall back on what is now popularly known in engineering circles as 'flow production,' we must not forget that Bodmer, a Swisswho worked the later years of his life in Manchester, had laid out machines on a progressive operations system in the 1830s, andhad devised a travelling crane to assist in the manipulation of the work. In 1815 in Switzerland, he installed what seems to havebeen a conveyor-belt system in a flour-mill." Later in his review of progress during the ioo^year period,Mr. O'Dea said that, for a century before the Wright brothers made the first controlled flights in a heavier-than-air machine,serious scientific work was being conducted on the problems of flight by such men as Henson and Stringfellow. "We have a greatregard," he added, "for Maxim's huge machine of 1894, which would have flown had it not been held down by check rails." Most early aircraft, said the lecturer, hardly looked like engi-neering jobs, with the possible exception of the Avro 504 of 1913. In 1917 the A. V. Roe works in Manchester were making tenAvro 504s a day. THE ALL-SEEING CAMERA AERIAL photography as an aid to archaeologists was the subject**• of a paper read before the Royal Society of Arts on February 21st by Dr. J. K. S. St. Joseph, Curator in Aerial Photography atCambridge University. As readers of Flight who studied the article "The World inCamera" (April 13th 1950) will be aware, ancient foundations which have been overlaid by centuries of agriculture and arequite invisible on the ground can be seen and photographed from the air, especially with the aid of a low sun. In his lecture, Dr. St. Joseph showed how not only the existenceof such sites, but even their character and period, could also be clearly perceived in this way. Long-rooted cereals generally gavethe most sensitive renderings of such hidden features; root crops were often just a blurred image, while grass, except in droughtconditions, was seldom responsive. Thus, if a site were observed over a period of years and the land was under crop rotation, sooneror later the required information would be obtained by means of the aerial camera. Some outstanding examples of the application of air photo-graphy to archaeological knowledge, said the lecturer, were the Stonehenge Avenue, the prehistoric religious site at Dorchester,Celtic fields on Salisbury Plain, and Roman town-plans at St. Albans and many other places. Discoveries of new religiousmonuments had been made at Birrens (Dumfriesshire), Ceupland (Northumberland) and Elston (Notts), and a large number of IronAge hill forts had been discovered and photographed. In addition, our knowledge of the military and civil districts of Roman Britainhad been enlarged. The aerial camera had revealed military sites on Watling Street, and public buildings, shops, houses and evenmosaic or concrete floors in the old tribal capital of Wroxeter. Owing to great building projects, open-cast mining, afforesta-tion and agricultural development the surface of Britain was under- going a swifter change than ever before. Visible archaeologicalremains could be preserved, but hidden sites, which often con- tained greater historical material, were not taken into account. Airphotography was the answer in compiling a planned national sur- vey for record purposes. Time was short, and the opportunityin many cases, would not occur again.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
