FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1957
1957 - 0184.PDF
ia§ FLIGHT, 8 February 1957 BY-PASS ASSESSMENT . . . Figs. 11 and 12. Extensions of the turbine-blade toots on the Dart (left and extreme right) made possible a considerable reduction in temperature compared with earlier turbojet blades. S25*C 27CC c-fl-s zjut — 23<re rims were exposed to the hot gases and as they received a large heat-inflow from turbine blades, a high-temperature alloy was used. The disadvantages of this material were that it was difficult to forge and that its poor thermal conductivity resulted in large temperature gradients. The result was cracking in the blade- fixing serrations with repeated temperature cycles. Ferritic material gave higher permissible stresses, but the tem- perature had to be reduced. This inspired the design of the "extended blade-root" which removed the turbine rim from the influence of the hot gases, and was first introduced into service on the Rolls-Royce Dart. The arrangement is shown in Figs. 11 and 12. An important feature of the turbine design is the flow of cooler air up the face of the turbine discs to prevent the inflow of the hot gas; with the extended blade root design the rim tempera- ture did not exceed 375 deg C, whilst in the old design it was 525 deg C. This is shown in Fig. 11, a design that has now flown over 1^ million hours in civil transport operation. The authors concluded their paper by saying that they had attempted to make as fair a comparison as possible of the jet and by-pass engines. Their assumptions were that both types feature the same design technique and stress levels and the use of similar materials. The broad conclusion that they drew from the analysis was that the by-pass engine has the advantage in weight and consumption for the particular operation considered. THE VULCAN ACCIDENT INQUEST WHEN the inquest on the victims of the accident to theR.A.F. Avro Vulcan at London Airport on October 1was resumed last week, the possibility of altimeter error as a contributory cause was suggested when the pilot, S/L. D. R. Howard, said in evidence that he believed his altimeter had been "gravely misleading" on the approach. He said further that his rate of descent would have been "fantastic" had he been at the height given by the ground controller a few seconds before the impact. At the inquest, held in Ealing on January 30, the jury returned verdicts of accidental death on S/L. Edward J. Eames, aged 32, navigator; S/L. James G. W. Stroud, aged 29, second navigator; S/L. Albert E. Gamble, aged 35, air electronics officer; and Mr. Frederick Bassett, of A. V. Roe and Co., Ltd. In his summing-up the coroner, Dr. H. G. Broadbridge, sug- gested there was nothing in the evidence to show criminal negligence on the part of anyone in the aircraft or on the ground; everyone seemed to be doing their duty as they thought right at the time. S/L. HOWARD said that before leaving Aden he had received a signalfrom Bomber Command saying that he was to land at London Airport. Asked by the coroner if he had decided definitely to land there, S/L.Howard replied: "No. I was going to make an attempt to land, in view of the weather. If I could not, I was going to overshoot and go toWaddington, where it was promised that the weather would be very good. I decided to come down to 300ft by my altimeter, which repre-sented to me a minimum approach altitude for London Airport of 150ft over the ground." As the Vulcan came in at an approach speed of about 160 m.p.h.—"usual for diat type of aircraft"—the talk-down from the ground con- troller was normal, and S/L. Howard said he acted on the informationas soon as he received it. Before the talk-down was completed he hit the ground. He now knew—although he did not know at the time—that he wasoutside the runway when he hit the ground. The last instruction he remembered before hitting it was "Three-quarters of a mile, 80ft high"—meaning he was three-quarters of a mile from touch-down and 80ft above the ideal glide-path. He increased the rate of descent "I asked the co-pilot, at a range I cannot remember, to look for thehigh-intensity lighting, which I was going to use to complete the landing. He told me he could see the lights over to starboard. All this time Iwas looking at instruments, not looking out. "I looked for the lights as he told me, and I did not recognize thepattern. They were not what I expected to see. Immediately I had looked I went back on instruments, and he then told me I was verylow, and to pull up. I did. "At that precise time, the aeroplane just touched the ground and Idecided to overshoot. This I tried to do, but as the aircraft accelerated it became obvious that I could not control it any moie. It wanted toroll over to the right. "I used all the control I had but I could not stop it and I realized Icould do no more. My altimeter was showing slightly below 300ft. "I shouted to the crew to get out and when it was apparent that theaircraft was going to roll into the ground decided to eject." Asked by Mr. L. A. Prickett, representing A. V. Roe and Co., Ltd., ifhe had any idea what happened after hitting the ground to make the air- craft uncontrollable, S/L. Howard said : "At the time I did not know,and I could not understand why, because the aircraft did not hit the ground hard. But on recollection now, it must have been that the con-trols were damaged when the aeroplane hit the ground." The coroner, Dr. H. G. Broadbridge, asked if the altimeter wasgravely misleading him. S/L. Howard replied that he believed it was, but he did not know how it could be accounted foi. He told Mr MichaelEastham (appearing for Miss Ann Mailey, an Ai* Traffic Control assistant) that he held a Master Green instrument rating, the highest an R.A.F. pilot could have. He said tiiat diere was a known error of 70fton his altimeter and he set 80ft as the height of London Airport a.s.l. He agreed that if he had been on the glide-path three-quarters of a milefrom touch-down he should have been about 260ft off the ground. If the altimeter had functioned correctly he would have broken off bisattempt to land. AIR MARSHAL SIR HARRY BROADHURST, A-O.C-in-C. Bomber Com-mand and co-pilot of the Vulcan, said that he left it to die judgment of S/L. Howard, as captain, whether he (Howard) tried to land or not.Asked by the coroner whether the talk-down was normal, he replied: "There was nothing in it to alarm you. It seemed perfectly safe."Speaking of the lights, he said they appeared as a sort of misty glow on the starboard bow, and he immediately reported them. When the lightsbegan to clear into a pattern he knew they were too low. They hit the ground a glancing blow and he was so convinced that nodamage had been done that as the pilot opened his throttles and the air- craft rose he said : "If we turn slightly left we can still make it."But the pilot answered: "No, I am going to overshoot." Then he said: "I think we have had it." He called to the crew to get out, andejected. Sir Harry tried the controls but got no response, then ejected himself. He said that his and the pilot's altimeters were not coincident on theflight; there was an error of between 50 and 80ft between the two. Asked if he could account for the additional error in the altimeter, heanswered that they now had established phenomena which might account for it.MR. JOHN MANNING, G.C.A. controller, said that the Vulcan was about six miles out when he established contact with it. His screen didnot show the aircraft's height above the glide-path; that was given to him by a meter operated by his assistant. The aircraft must have come downat a steep angle and touched the ground in a matter of seconds. Replying to Sir David Scott Cairns, Q.C., Mr. Manning said thatso far as the screen was concerned, the appearance to him of an aircraft on the ground or one passing over safely at a point, say, 150ft abovewould be exactly the same. "From the point 80ft high the meter showed a descent towards the glide-path. I cannot say with accuracy whetherit had reached the glide-path. I can say it did not go below." Miss ANN COLLINS MALHY, the tracker, said that her job was towatch height and range on her instruments, passing the range to the controller verbally and the height by instruments. Replying to thecoroner, who suggested that the aircraft must have descended rapidly at some stage, Miss Maley said she did not recollect any rapid descent.When the Vulcan was about two miles away, it seemed to drop about 100ft below the glide-path and she mentioned this to the controller.She agreed that it must have recovered because later it was above the glide-path. S/L. HOWARD was recalled and asked by the coroner whether it wouldbe an abnormal rate of descent to drop 300ft in 500 yd. He replied that this would be "fantastic—about 4,000 feet per minute," and thathe would have known if they had been going down at that rate. W/C. C. K. SAXELBY, from the A. and A.E.E., Boscombe Down, saidit had been found that, when the aircraft came close to the ground, the 70ft altimeter error could become about 130ft, added to which there wasthe 80ft for London Airport's height above sea level. It was quite possible for there to be a further error of 70ft caused by friction. MR. B. M. STEPHENSON, representing the R.A.F., the M.T.C.A. andthe two survivors, expressed his sympathy with the relatives of the deceased, and was joined in this by Sir David Scott Cairns and Mr.Eastham. * * * In a statement issued after the inquest, Mr. Stanley Mayne, secretaryof the Institution of Professional Civil Servants, referred to one of the recommendations in Dr. A. G. Touch's report on the accident Flightlast week, p. 131], saying that a G.C.A. system in which the controller observes both sets of displays—dius eliminating the need for a tracker—had been developed and should be put into operational use as soon as possible. Similar equipment, said Mr. Mayne, had been in use in othercountries for some vears.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
