FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1975
1975 - 0018.PDF
18 WHAT'S HAPPENED TO HOVERCRAFT? about receiving a return on capital employed on their total investments, but hovercraft have captured nearly 30 per cent of the cross-Channel traffic in people and cars. It remains to be seen how different the cost picture might have been if military development had soaked up the R&D costs and effort. In the military field outside Britain, BHC has been highly successful in selling SR.N6s and its latest design, the 45- ton BH.7, to Middle East customers, Iran in particular. Vosper Thornycroft is also actively pursuing the military market with an amphibious craft, the VT-2, of 65 tons all-up weight. Iranian and Saudi Arabian purchases of British hover craft highlight the fundamental advantages of the ACV concept. In the Middle East there is a need for craft which can operate in shallow water, far away from fixed bases. This need is again paramount in the northern Canadian Arctic, where the terrain is basically flat but changes its characteristics between winter and summer from ice and snow to non-load-bearing, vegetation-covered mud. Oil and defence requirements—which have become apparent with the opening-up of the North Slope—have proved the need for low-footprint-pressure vehicles in the area. Helicopters have been widely used, but ACVs are cheaper in some cases and require fewer skilled personnel. Bell Aerospace (Canada) is building 40-ton Voyageur and 17-ton Viking craft specifically to cope with Canadian logistics problems. FLIGHT International, 2 January I97S was being discussed by the US Army at a Princeton University symposium as early as 1959, there had been no significant military contracts placed for ACVs until the early 1970s when the US Navy began gearing up its efforts to produce sidewall craft, now being spoken of as the spearhead of the "lOOkt Navy". The third reason is perhaps the most important and may have affected the other two. It was difficulty encountered by manufacturers in accurately forecasting the cost and progress of R&D in ACV technology. Early operators, both military and civil, were faced with operating costs which were greater than originally forecast and craft perform ances which in some cases were not up to specification. In turn the manufacturers' R&D costs in improving perform ance were greater than anticipated and led to increased capital costs in later craft. Escalating costs prevented the ACV from competing effectively in the market place with other forms of trans port such as ships and hydrofoils. On the military side, the US Army had great success with Bell-modified BHC SR.N5s in Vietnam in a number of limited-scale operations. Britain formed a hovercraft squadron as part of the Royal Corps of Transport, and the Royal Navy had a hovercraft detach ment in the Falkland Islands for some years, but neither service in the end could justify the continuation of its token forces during a period of general retrenchment in defence spending. Even now, ten years after its Vietnam trials, the US Army is still considering using amphibious ACVs in the amphibious logistics role. Only the US Navy is going ahead on a large scale, and even then with sidewall, non-amphibious craft. The Mk I SR.NI at Farnborough in September 1959. No skirts had been fitted at that stage; the engine was the original Alvis Leonides but someone clearly saw a military potential which has yet to be fully realised in Britain A British firm, Air Cushion Equipment Ltd, is also heavily involved in Canada, as well as having interests in Britain and other areas. This second-generation company was formed as a design and development group which until recently only manufactured skirts. These it provided as part of a total design service for companies wanting to move heavy and unusual loads using lower horsepower/ton ratios than are available with conventional lifting equip ment. Perhaps significantly, ACE is now moving into water- cushion systems in order to cope with multi-thousand-ton loads. In the United States work is now in hand on the design and development of two 2,000-ton "surface-effect ship" prototypes for the US Navy. These will not be amphibious, but are forecast as the predecessors of the 10,000-ton air- cushion aircraft carrier and fast sub-chaser. In 1975, the 17th year of ACV operations, it is easier to review the events of the early- and mid-1960s in perspective and to pinpoint many of the reasons why hovercraft did not break through the "credibility gap" at a time when many proponents of the ACV as a radical new transport medium were forecasting for it a future as rosy as that of the commercial aircraft of the period. (To be fair, there were as many sceptics on the subject as there were opti mists.) First, no definitive market for commercial passenger- carrying craft had been found at that time; the concept of freight and utility craft was only just developing and sales effort was being directed toward passenger-carriers. Second, although military usage of the amphibious ACV The sad fact is that without substantial military spending hovercraft technology will not advance rapidly. All the major problems in aviation technology (including space flight) have been solved because of a military requirement and there is no' reason to doubt that the same will apply to hovercraft progress in the future. The technical prob lems in hovercraft arise mainly in the propulsion system and in the skirt. ACVs have the same power/weight-ratio problems as aircraft, although on a lesser scale, but the skirt problems are more complex. Materials, for example, have had to be developed to resist abrasion from a wide variety of sources and over a wide range of temperatures; detailed skirt shapes to produce greatest lift efficiency have had to be designed and tested literally by trial and error (although test tank results can now be scaled up with greater accuracy than was the case ten years ago); there is still a great deal of work to be done on the hydro- dynamic/aerodynamic interface—the area in which the skirt is mostly operative—and on cushion dynamics. While British manufacturers struggle on to sell de veloped versions of ten-year-old designs (Vosper Thorny- croft excepted), BHC is actually selling its skirt technology expertise to one of the American companies developing a 2,000-ton sidewall craft for the US Navy. American military funds are being used to buy the British know-how that successive British governments have refused to fund (see table). We British will only have ourselves to blame when, in 20 years' time, we are buying large hovercraft off-the- shelf from the USA, just as we have done with jet aircraft for the past decade.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
