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Aviation History
1963
1963 - 1171.PDF
Air-Cushion Vehicles FLIGHT International supplement, 27 June 1963 LETTERS TO THE EDITOR The Editor of "Air-Cushion Vehicles" is not necessarily in agreement with the views express ed by correspondents in these columns. Names and addresses of writers, not for publication in detail, must in all cases accom pany letters. ACV v Tunnel SIR,—In your issue of May 23 a spokes man for the Channel Tunnel Study Group is quoted as making some rather categorical statements which do not seem to take account of the potential developments in transport and in hover craft in particular. A decision to spend some £130m on the construction of a Channel tunnel is a grave and serious step. Not only must there inevitably be some measure of doubt about the accuracy of any predictions of future traffic and on passenger appeal, but more unpredictable still is the extent and the effect of future developments in the transport field. Airlines are not always correct in assessing the profitability of a new aircraft with a working life of ten years. Shipping companies seem unable to predict over the 25 years of the life of a passenger liner. The tunnel, with a potential life of about 100 years, is an even more difficult problem. Look ing back at the history of transport over the past 100 years, many things have happened. The canals have been ousted by the railways, which, after reaching their peak, have been made unprofitable by developments in road transport and by the advent of the aircraft. Looking at the future (and it is unreasonable to expect to be able to draw a clear-cut picture even over a fifth of the life of the tunnel) helicopters, hydrofoils and hovercraft are coming up, and, further off, the hover-railcar. I think that the only thing that can be said "without hesitation" is that trans port development will go on, and at least at the pace achieved over the last 100 years. If there were no alternative to a £130m Channel tunnel or a £200m Channel bridge, and if a decision had to be made now, the decision would have to be for a tunnel, because a bridge, taking account of the predicted traffic, would not be profitable for many years. How ever, these two fixed facilities are not the only possibilities; and, if a tunnel is built, the sponsors must be prepared for hovercraft to be operated over the same route at lower fares, and for the grave risk that the tunnel will have its revenue reduced to little more than that obtain able from freight carrying alone. Again, long before the end of the life of the tunnel, there are arguments that point to a network of fast (300kt?) hover-railcars between city centres both in Britain and on the Continent. If we are to reap the benefit of this advance in surface transport, the two networks should be connected via a Channel bridge (a tunnel would not be a suitable link). This development will, of course, affect the short-haul air network, and is quite typical of the ever-changing trans port scene. But is a fixed facility really needed at this time? It is not generally realized that the existing cross-Channel facilities without expansion are capable of carry ing for the next 20 years the predicted growth in traffic during the eight winter months, and that the congestion, requiring an expansion of facilities, occurs only during the four summer months, and is entirely due to the heavy holiday traffic. It seems to me that, in the light of the uncertainties of traffic growth and of transport developments, there is a strong argument for augmenting and improving the existing Channel links with hovercraft, and then later, probably in 20 years time when the traffic has built up sufficiently to warrant a fixed facility, building a bridge capable of carrying all types of surface transport, including hover-railcars. Such a plan would make it unneces sary to take the dramatic decision at this time to spend £130m on a tunnel, when the profitability is based on un certain predictions of traffic growth and during the early days of a funda mentally new form of transport. Moreover, such a plan would facilitate the building up of a British export market in hovercraft. A hovercraft service including terminals and suitable craft, increased in size and numbers in step with requirements, could be got going, and phased into the existing system, for about one-tenth of the cost of the tunnel; and at any time thereafter it could be decided to choose and install an expensive fixed facility, the hovercraft being moved down the coast to serve other routes. Hythe, Hants c. s. COCKERELL Periscopic Proposal SIR,—I am enjoying my subscription to Air-Cushion Vehicles. The field of locomotion—whether on land, on sea, in the air or in between the two—is one of my major interests. As a visual consultant to the automotive industry I have had occasion for the last two years to develop the visual and human factors evaluation that are involved in present ing a rear-vision mirror periscope to automobile operators. It has come to my mind that hover craft would benefit immeasurably by the use of periscopes. Firstly, a conven tional periscope such as we are using on automobiles should be incorpoated on the cabin structure so that the operator could have a wide view (44°) of events that are taking place aft of his craft. Secondly, he should be able to see both forward and laterally from his craft with periscopes that view the scene from a point at the level of the craft's clear ance (bottom of the craft). In this way he would know if he was going to clear ground hillocks, stumps, waves, etc. All these could be presented efficiently on a console in front of the operator. I would be more than pleased to discuss the application of our patented periscopes with any of the companies manufacturing hovercraft and hydrofoil craft who might express an interest. PAUL L. CONNOLLY, OD, 4066 Telegraph Rd, Visual Consultant Bloomfield Hills, Michigan, USA Conflict SIR,—The publishers of the book Hydroplanes and Hovercraft have drawn my attention as author to a review of the book which appeared in your March issue. With the exception of one reference to what is quite definitely a mistake the reviewer has drawn conclusions and made comments which imply that facts in the book are incorrect. As the theoretical and design work in the book is all taken from established textbooks on the subject written by well-known, fully qualified naval architects, I am at loss to see what the reviewer hopes to achieve except the odd knock at the establishment. I should like to make a brief summary of the reviewer's misconceptions. An explanation is given regarding the value of Froude number which should be used and regarding the "K" value for hydro foils this was supplied by Supramar Ltd, designers of nearly all the world's hydro foils. Unless a particularly high degree of stability is required the length of a hydroplane and hence the position of the "step" does matter. The reviewer is wrong: the friction 100
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