Linda and I took our car across the Channel on one of these massive Hovercraft in the Mid 1980s
Video (Poor Quality) Here • Dover Trip Linda VW Va...
The SR.N4 (Saunders-Roe Nautical 4) hovercraft (also known as the Mountbatten class hovercraft) was a combined passenger and vehicle-carrying class of hovercraft. The type has the distinction of being the largest civil hovercraft to have ever been put into service.
Work on the SR.N4 was initiated in 1965 by Saunders-Roe. By the time that the vehicle's first trials took place in early 1968, Saunders-Roe had merged with Vickers Supermarine to form the British Hovercraft Corporation, who continued development. Power was provided by four Rolls-Royce Proteus marine turboshaft engines each driving its own lift fan and pylon-mounted steerable propulsion propeller. The SR.N4 was the largest hovercraft then built, designed to carry 254 passengers in two cabins besides a four-lane automobile bay which held up to 30 cars. Cars were driven from a bow ramp just forward of the wheelhouse. The first design was 40 metres (131 ft) long, weighed 190 long tons (193 t), was capable of 83 knots (154 km/h) and could cruise at over 60 knots (111 km/h).
The SR.N4s operated regular services across the English Channel between 1968 and 2000. In response to operator demands, stretched versions of the SR.N4 were developed, culminating in the Mk.III variant, which had almost double the capacity for carrying both cars and passengers as the Mk.I. While interest was expressed in military applications for the type, no vehicles were ultimately used for such purposes. Following the fleet's withdrawal from cross-channel services, a single remaining Mk.III example, GH-2007 Princess Anne, has been preserved; it is currently on static display at the Hovercraft Museum at Lee-on-Solent.
The SR.N4 was the biggest hovercraft to have been completed upon its introduction. Its primary structure comprised a large modular buoyancy tank, the internal structure of which being divided into 24 watertight compartments. It had an identical platform shape to the smaller SR.N5, being rectangular with a semi-circular bow and a beam-to-length ratio of 1:1.66. Navigation wise, the SR.N4 had a dual radar system for navigation purposes allowing the craft to operate in zero visibility- Type Racal Decca Bridgemaster with GPS navigation system.
The SR.N4 was powered by four Rolls-Royce Proteus turboprop engines. The Proteus engines each drove a set of 19 ft (5.8 m) diameter steerable Dowty Rotol propellers, arranged in two pairs on pylons positioned on top of the craft's roof; upon the SR.N4's introduction to service, these were the largest propellers in the world. Six independent electrohydraulic systems, each driven from the main gearboxes, powered the movement of the fins and pylons, while a further four units were used to actuate the variable-pitch propellers.
The interior of The Princess Anne in 2019
The control cabin of the SR.N4 resembled the flight deck of an aircraft, being relatively cramped in comparison with the bridge of a typical vessel. It housed a crew of three, comprising a captain, first officer/flight engineer, and a second officer/navigator; the main role of the second officer was to avoid collisions, primarily using a Decca 629 radar to do so. The flying controls appeared broadly similar to a typical aircraft, using an assortment of rudder pedals, joysticks, yokes, separate propeller pitch levels, and engine speed controls; however, their functionality often differed substantially, such as the ability for the yoke to command the pitch of all four propellers.
The SR.N4 is fitted with a 12-ton skirt which runs under the perimeter of the whole craft and employs a complex structure. On the underside of the buoyancy tanks, a total of five 21-inch platforms (known as 'elephant feet') were positioned so that the craft could stably rest on three of them.
Fuel was contained within flexible bags located at all four corners; the craft could be trimmed by intentionally redistributing fuel between the fore and aft tanks to better match the load and prevailing weather conditions. The craft would consume 1,000 gallons per hour at a cruise of 50 knots before refuelling with an approximate range of 150 miles. Maximum fuel capacity was 8068 gallons, 36,676 litres or 28.8 tons.
The stern of the craft featured a sizeable set of doors for the loading and unloading of vehicles onto the car deck as well as all four of the exhausts for the Proteus engines, another set of loading doors were present on the front as well.
Filmed on DJi Pocket2