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Aviation History
1951
1951 - 1889.PDF
374 FLIGHT, 14 September l95I CORRESPONDENCE The Editor of "Flight" does not hold himself responsible for the views expressed by correspondents in these columns; the names and addresses of the writers, not necessarily for publication, must in all cases accompany letters. Tomorrow's TrainersI N your leader of August 24th it is suggested that the question might be asked: "What can Balliols do in the way of advanced training that Vampire Trainers cannot do better?" Earlier in the same paragraph you refer to the Vampires as operational trainers, a role that is comparable with that of the two-seat Meteors. It is presumed that the word operational in this case means training in the operational role specifically associated with this class of aircraft, whereas the major part of "advanced training" is con- cerned with instruction in all operational aspects of aircraft as a military weapon, i.e. the use of offensive and defensive armament, reconnaissance, navigation, etc. Such training can, surely, be given more economically and affectively in a type of aircraft specially designed for the purpose, and, in the present state of technical development, can certainly be given more cheaply on aircraft fitted with low-rated piston engines than on those with jets. The time may come when the balance of advantage in cost and effectiveness of training may change in favour of a jet-engined aircraft specially designed to fulfil the advanced training role and to carry the diverse and alternative equipments which the modern Service pilot has to learn to use. In my opinion no such aircraft exists today, but the P. 119 project described in your issue of August 31st seems to provide an economical and effective answer. London, S.W.I. L. M. ILES, A.V-M. (ret.). Delta AerodynamicsI WAS rather surprised by a statement appearing in Mr. Ewans' article, "Aerodynamics of the Delta" (Flight, August 10th). In the first paragraph on p. 173 I read : "As air flows past a wing its speed is increased over the upper surface to a considerable extent and over the lower to a lesser extent, so that there is a greater suction on the upper surface than on the lower surface." Until reading this, I was under the impression that the funda- mental explanation of lift involved the consideration of the super- position of streaming flow past an aerofoil and circulation round it, giving rise to increased speed over the aerofoil and decreased speed below it. By Bernoulli's Theorem these perturbations of speed can then be related to a decrease of pressure above the aerofoil and an increase of pressure below it. I should, therefore, welcome some expansion on this subject by Mr. Ewans, or other of your more technically-minded readers. Incidentally, should not the fourth "delta" in the list at the commencement of the article read XF4D-1, XF3D-1 being the Skynight, a twin-jet night fighter? London, W.4. T. S. R. JORDAN. [Yes, XF4D-1 is the correct designation.—ED.] Piscatorial Aeronautics AS it takes some time for my copy of Flight to penetrate as far asSwaziland, I fear I may be rather late in presenting my observations on flying fish (article by L. W. Crawford, July 27th). However . . . I also spent days watching flying fish doing their version of "circuits and bumps" and, unlike Mr. Crawford, came to the con- clusion that their flight was not powered—despite the apparently extraordinarily small angle of glide which both Mr. Crawford and I observed. The gliding angle relative to the horizontal is virtually zero, but I suggest that the angle of glide relative to the direction of the air stream is much greater. Did Mr. Crawford notice that the fish flew only when there were moderate wave conditions? It seemed to me that they got most of their lift from the up- currents at the wave tops, which enabled them to keep airborne over the troughs. "Wing" vibrations, or flutter, I did see, but I interpreted this to be a result of turbulence over the wing surface when the angle of attack changed from positive to zero (or even negative) as the fish moved almost horizontally through an undulating air stream. There is, however, a form of propulsion once the fish is airborne —particularly with Exoccetus, which has z. fairly well-projecting lower portion to its rudder. One notices this lower rudder breaking the surface on wave tops and waggling violently, so boosting the speed just as maximum-lift conditions are provided by the upward air current. Changes in direction also follow the use of this sea- rudder. I doubt if the ability to alight on a ship's deck is "unquestion- able [evidence] that they must use power for flight"; the fish that I saw came aboard from the weather side of the ship, assisted I submit, by the general turbulence and up currents of air passi over the vessel. On one point Mr. Crawford and I agree : the biological gentle- man's "parachute" theory is a little difficult to accept, but maybe he, too, was thinking in terms of the fish making the maximum use of up-currents. Mbabane, Swaziland. G. DENNIS GILBERT. Rearward-facing Seats "V^OUR correspondent Mr. J. Scott (August 24th) appears to •*• have the opinion that "advocates of rearward-facing seats" believe them to immunize the passenger from hurt in any type of crash. Of course, this is not so, but if anyone with a slight knowledge of dynamics would show him the effects of a body in a forward, then a rearward-facing seat during a sudden deceleration, he would then become an "advocate of rearward-facing seats," especi- ally if he were that body. We know that a rearward-facing seat is of no more use than a wicker chair in a crash from any altitude; but for emergency landings, such as "wheels up," they are of great value to human lives. Mr. Scott also writes that advocates of rearward-facing seats are inclined to quote accidents which support their case; be this as it may, the only crash with which he backs his case possibly hap- pened after the original letter from Mr. J, Howard had been written and published. Warminster, Wilts. G. NORRIS. Airfield FiresW ITH reference to "Enquirer's" letter (August 31st), recorded instances of lives being saved from severe aircraft crashes at civil airfield are few, but do exist. The reason there are not more is due mainly, outside most M.C.A. and a very few overseas inter- national airports, to the inadequacy of equipment and training facilities and the apathy of airport operating authorities towards the problem. The really severe high-speed impact-crash fire, either on or off the airfield, is always a difficult problem, but there are numerous cases where prompt action by efficient crews and apparatus on small to medium fires has undoubtedly prevented a major fire developing within a few seconds and has enabled passengers a crew to get clear safely or to be rescued. Conversely, there are other cases where initially small fires have led to complete loss of the aircraft and to death of passengers or crew because of inefficient ground aids. Details are too lengthy to be produced here, but if "Enquirer" is interested he is referred in particular to the bulletins and reports issued by the National Fire Protection Association's Committee on Aviation and Airport Fire Protection, from 60 Batterymarch Street, Boston, Mass., U.S.A. Recommended I.C.A.O. minimum crash/fire standards already exist for various grades of airfields, based on lengthy research by several organizations; but, with the above exceptions, most over- seas airfields provide only from 5 to 40 per cent of the recom- mended outputs, and these cannot be successful on major fires. London, W.i 1. FIRE ENGINEER. I CANNOT answer your reader who enquires whether fire-fighting equipment has saved a single life at a civil airfield dur- ing the last 20 years, but I can mention one way in which it might be made more likely to do so in the future. As "Enquirer" says, fire engines cannot normally travel beyond the perimeter. It ought to be compulsory, therefore, for all airfield? except those reserved for gliders, to have bridges leading across the perimeter drainage ditches into adjoining fields; and ever/ ga'e lying in the path of fire engines up to a distance of at least a v^ from the perimeter ought to have laterally weak hinges and l<-tchs so that any vehicle that might be used in saving life can push tw gates to the ground and drive over them. Eastbourne. WILLIAM F. JORDAN.
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