FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1961
1961 - 1424.PDF
528 FLIGHT, 5 October 19. Symbolic of an earlier era, the bri yellow Vickers VA-I hovercraft accompanied on trials in the Sok by a launch bearing a red fag, a is restricted to operation in visib< ties of more than half a mile. L power is provided by a Gipsy Moj driving, through a clutch and be cardan shafts to fore and aft i fans. The propulsion engine is Continental flat-four driving a fixe pitch propeller. Individual cockpi are provided for pilot and observe but the engines are left uncowk HOVERCRAFT NEW GENERATIONS AHEAD EVER since Saunders Roe first demonstrated their SR-N1 onthe Solent in 1959, British interest in hovercraft has beensteadily quickening. Under the auspices of Hovercraft Development Ltd as a benevolent co-ordinating authority, thedesign of surface-effect vehicles has been carefully nurtured, so that only three years after the birth of the SR-N1 a whole family ofcomplementary craft is coming into being. Last week it was the turn of Vickers-Armstrongs to demonstratethe results of some of the effort which they have been putting into amphibious vehicles, and to outline the project work which maylead them, more rapidly than any other hovercraft manufacturer, to the first goal of current development—commercial scheduledservices by an established operator. For the better part of a year the South Marston firm has beenexperimenting with a simple research vehicle designed to explore the technical aspects of hovercraft development. By no means asrefined in concept as the SR-N1, the VA-1 is a simple laboratory tool designed to be rapidly modified for empirical experiment.As such, it must offer more scope for the development of lift curtain systems, stabilizing devices and cushion controls than waseasily possible with the SR-N1; and by the interchange of informa- tion through Hovercraft Development many of the lessons learnedfrom the first Saunders-Roe vehicle should be available to Vickers- Armstrongs (South Marston) for re-assessment on VA-1. Aboveall, this 3,5001b platform is paving the way for VA-3, a passenger- carrying hovercraft which is now under construction. With applications already before the Air Transport LicensingBoard for hovercraft services, commercial pressure for a practical load-carrying vehicle is the spur to development for all members ofthe hovercraft club—Vickers, Saunders-Roe, William Denny, Britten-Norman and Folland. Saunders-Roe at least seems attrac-ted, with the SR-N2, to naval and military hovercraft applications, and Folland to vehicles which operate overland, so that it may beDenny's sidewall craft or Vickers' VA-3 or VA-4 for which com- mercial orders for a hovercraft ferry are first placed in any quantity.This will be the second great milestone in the story of hovercraft. Meanwhile, technical problems still have to be solved, particu-larly recovery and recirculation of static air, and the still difficult problem of effective control at low speeds. Much thought has beengiven by Vickers to recirculation and spray control, as wind-tunnel models, water spray rigs and VA-1 itself give evidence; outriggersand spray guides as now fitted to VA-1 appear to have virtually solved the spray problem. But dust and spray ingestion are dif-ficulties still associated with recirculation ducts, so that this effective method of energy recovery is still largely a laboratory solution toincreased efficiency. After seeing Vickers' careful background work to cushion andcurtain development, VA-l's control system seems surprisingly crude. No sensitive fore-and-aft control is provided, as in SR-N1,and all turning movement is provided by aerodynamic rudders operating in the slipstream of a 90 h.p. Continental engine. Aspropulsive thrust must be zero when VA-1 is hovering, the vehicle is particularly susceptible to side gusts and wind drift, and onlywhen its momentum is high does control seem reasonably effective. Another disadvantage of the simple system used is that momentumis only destroyed by the drag of the structure, or by reversing direction of the whole craft to bring it to rest. None of these difficulties is insurmountable, and VA-3 is to havea much more sensitive control arrangement using twin reversible- pitch propellers—a system shown to be successful in principle on the First glimpse of the VA-3, due for hover-out next spring. This hovercraft, a ten-tonner, will carry a payload of 24-26 passengers at a cruising speed of 60 kots and a hover height of up to eight inches. Pairs of Turmo 603 shaft turbines provide power for lift and propulsion CC-1 Cushioncraft constructed by Britten-Norman. Two otherdevelopment studies for which VA-1 is being used are investigations into length/beam ratio, and the use of spoilers in the efflux duct forlateral and pitch control. It was found on the SR-N1 that a con- siderable length of air curtain had to be sterilized to overcome thenatural stability, but the spoilers on the Vickers craft are said to be fully effective. All this development work should pay real dividends in thedesign of the "operational research" craft VA-3, the structure of which is now about one-third complete. Still, although too small tooperate over wave heights greater than about two feet, and thus likely to be confined to service in estuaries and rivers,VA-3 couldoperate a passenger ferry where, because of sandbanks or tidal waters, none has been possible before. Given a route where sub-stantial savings in overland distance are possible, the unknown variable of cost per seat-mile might conceivably look attractive.But it is the larger, third and fourth generation of hovercraft to which designers and operators are looking for the full potential ofMr Cockerell's invention to be realized; and Vickers are now working on VA-4, a car-ferry hovercraft of about 100 tons all-upweight and a hover height of 3ft, and VA-5, a 500,0001b vehicle capable of overwater operation. No time-scale is attached to theseprojects, but the thinking behind them is outlined in the following Vickers statement: "For the type of seas likely to be encountered on unprotected watershovercraft sizes of from 100 to 1,000 tons should be considered. Such Concluded on page 564) Length Beam Powerplant lift propulsion Max weight Payload Cruise speed Hover height Range/endurance Remarks VA-I 25ft 13ft Gipsy Major Continental 3,5O0lb 2 crew 35-40kt 4.1 in research vehicle VA-2 28ft 4in 14ft 10 in 2"] light ^aircraft 1 J pistons 4 passengers 40kt 8.5in l±hr transportable demonstrator VA-3 52ft 6in 25ft Oin 2 Turmo 603 2 Turmo 603 22,0001b 24 passengers or 4,0001b cargo60kt 8m 87 n.m. commercial VA-4 173ft Oin 58ft Oin 100 tons 30 tons 70-80kt 3ft 260 n.m. commercial
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
