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Aviation History
1963
1963 - 1075.PDF
Air-Cushion Vehicles ACVs FOR THE ARMY . . . FLIGHT International supplement, 24 January 196 1—5 IN THE BEAUFORT SCALE Ship-Tank methods in the second phase, thus obviating the necessity of using ports. Since ACVs are inherently amphibious they must have an important role in putting the army ashore. It may be that, in due course, they will fulfil the main oversea role of the ships themselves; but, even so, it is unlikely that very large ACVs will be suitable for the initial assault role. This would be putting too many eggs into over-large baskets, and irresponsibly risking ultra- expensive craft. This article will there fore concentrate on such ACVs that might be of use in the assault phases of an amphibious operation. Payload is likely to consist of infantry groups or Commandos, with Land- Rover-type vehicles and trailers carrying their close-support weapons, anti-tank guided missiles and first-line supplies. The same type of craft will be needed to reinforce the initial ship-to-shore-waves, and a shuttle service is probably re quired. If the craft has a good enough overland capability to penetrate beyond the sea shore itself, this would give a bonus to rapid dispersion of the de livered forces, and would be most wel come for ammunition and resupply generally in the early stages of the campaign. Although it is obviously impossible for cliffs and man-made coastline obstacles to be crossed in most cases, lanes could be cleared through the latter in time. In short, the payload Ctaild be any reasonable number of men with their equipment, together with a capability for transporting small type vehicles and loaded trailers. It would be convenient for complete sub-units to be thus carried. Perhaps the minimum acceptable pay- load might be 25 men, a one-quarter- ton combat vehicle and trailer, and some manhandled infantry support weapons which will later require further transport (e.g., mortars). Oversea limitations seem to be the dominating factor in this-case. Such amphibious operations are carefully planned, and there is normally no question of operations going ahead un less the weather and sea conditions are reasonable. Apart from the waves en countered at sea, allowance has to be made also for the surf conditions on the beach. In this connection it may be as well to recall wave conditions implied by relatively mild weather at sea. If it is remembered that Beaufort Scale 6 is "strong breeze," 8 is "gale" and 10 is "storm," and that the mean height of waves in violent storm (Beau- Beaufort number 3 A 5 Limits of windspeeds (let) 7-10 11-16 17-21 Description Gentle breeze Moderate breeze Fresh breeze Sea conditions Large wavelets. Crests starting to break. Foam of glassy appearance, perhaps scattered "white horses." Small waves, becoming longer, fairly frequent white horses. Moderate waves, taking a pro nounced long form. Many white horses. Occasional spray. Probable wave height (ft)* mean 2 3i 6 max 3 5 Bi Surf likely (ft) 4-5 6-7 10-12 In enclosed waters, or when near land with an offshore wind, wave heights will be less and the waves steeper fort Scale 11) is 37ft, it is obvious that real "all-weather" operation of such craft is not possible. Perhaps a wave capability for Beaufort Scale 4 is a sensible solution. This requires a maximum hoverheight for waves of 7ft (for surf), so the normal hoverheight must be 3ft 6in. At this point the lowest part of the craft will be just touching the worst waves. For high-speed travel over- water, it would be convenient to have some extra clearance. Water impacts, even with only occasional extra-high waves, would require the base of the craft to be specially reinforced, and would also slow the craft. Once over land, the capability for extra clearance would be welcome. The devices to improve efficiency over sea, such as sidewalls, would have to be retractable for overland use, or extra clearance again made to allow for them. Perhaps the ideal true hoverheight would be 5ft. The size requirement is clearly of the same order as that assessed for the logistic supply vehicle, which, it will be recalled, had the following outline characteristics: h (pure), 5ft 4in, Wp, \1\ tons; gross weight, 50 tons; L, 55ft; B, 33ft; and max speed, 75kt. Here then is an attractive possibility: the same basic craft might be produced in two versions, one for logistic supply overland to fighting formations and one for ship-to-shore. The two versions would be bound to be different to enable the most efficient devices to be used over- water. A possible limitation would be the well-deck and stowage dimensions of the parent ship. The payload would enable a few selected lighter AFVs to be delivered to the shore in the assault wave, but where this was done the craft would be weight-limited and could not be fully laden with troops. However, calm weather and seas would allow such overload to be taken with advantage, if hoverheight were sacrificed. The other major saving on the oversea variation might be in power, but further details will be given in Part 3. The Suggested Start—Three ACVs A possible starting point for the Army thus appears to be three roles requiring transport in conditions where the more normal surface vessels and wheeled or tracked vehicles might be at a disadvant age. Part 3 will conclude this article and suggest possible configurations and characteristics for: a logistic supply ACV; a tank-carrying ACV; and an assault-craft ACV. The author does not pretend to have selected technical optimae in the craft suggested, but rather to visualize ACV potentialities. In fact the first and last of the proposed craft is not far removed from British ACVs already in existence, although the control problems inherent in overland movement may take some years to solve. To be concluded ACVs ON LONDON RIVER (continued from page 5) of requirements, rules and regulations without practical and proven founda tion which would create precedence and tend to make the ACV generally un economic. Similarly the operators of services would need to take full regard of the fact that they would be entering the field of passenger-carrying activity, which is already, by its unprofitability, a heavy burden on the taxpayer. There would be little or no future, for example, if any such enterprise was developed in a way requiring to bear costs similar to the enormous overheads of ground staff and administrators of the airlines, or to meet some of the traditional charges incurred by the shipping lines. Nor could they meet, in using ports and seaways, such costs as compulsory pilotage—an inherited overhead, ques tionable as to its value, especially with the advent of modern navigational aids. Crews would need to be kept to a satis factory minimum and expenditure on operation would need to be strictly governed in relation to profitability. 12
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