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The Mountbatten class hovercraft or SR-N4 was built by the British Hovercraft Corporation (BHC). BHC had been formed by the merger of Saunders-Roe and Vickers Supermarine in 1966. Work on the SR-N4 had begun in 1965 and the first trials had took place in early 1968.

The SR-N4 was the largest hovercraft built to that date, designed to carry 254 passengers in two cabins besides a two-lane automobile bay which held up to 30 cars. Cars were driven from a bow ramp just forward of the cockpit / wheelhouse. The first design was 40 m long, weighed 190 tons and was capable of 83 knots and could cruise at over 60 knots.

Contents 1 Service 2 Ride 3 Military 4 Survivors 5 Production 6 Specification 6.1 Dimensions 6.2 Performance 7 See also 8 External links 9 References

The craft entered commercial service in August 1968, with the Princess Margaret initially operated between Dover and Boulogne but later craft also made the Ramsgate (Pegwell Bay) to Calais route. The journey time, Dover to Boulogne, was roughly 35 minutes, with six trips a day at peak times. The fastest ever crossing of the English Channel by a commercial car-carrying hovercraft was 22 minutes, recorded by the Princess Anne SR-N4 Mk3 on September 14, 1995^[1], for the 10:00 a.m. service^{[citation needed]}.

In 1972 the first SR-N4s were converted to Mark 2 specification to allow for seven further car spaces and 28 more passengers. From 1976 two SR-N4s were refitted with new deep skirts and stretched by almost 17 m, increasing capacity to 418 passengers and 60 cars at the cost of a weight increase to almost 265 tons. To maintain speed the engines were upgraded to four 3,500 shp Rolls-Royce gas turbines fitted with 4 enormous 21 feet diameter steerable propellers. The work cost around £5 million for each craft and they were designated Mark IIIs, the improvements allowed them to operate in seas up to 3.5 m high and with 50 knot winds.

The two main commercial operators merged in 1981 to form Hoverspeed, which operated six SR-N4 of all marks. In all operations, while the craft were occasionally damaged, there was loss of life only once when on March 30, 1985 the Princess Margaret was blown onto a breakwater at Dover and four passengers were killed. The last of the craft was withdrawn from service in October 2000 and Hoverspeed ceased operations in November, 2005.

The ride was quite noisy, more like a ride on a noisy turboprop airliner than a boat.

The Royal Navy considered a mine sweeping version of the SRN-4, hovercraft being almost invulnerable to mines, but it never got further than the concept stage, although an SRN-3 was used by the Inter-Service Hovercraft Unit for trials.

Currently still the world's largest hovercraft. There are two remaining Mk3 examples at the Hovercraft Museum.

Built as Mark 1 unless specified otherwise.

• 01 - GH-2006 Princess Margaret, 1968 originally the prototype converted to Mk3 specification in 1979
• 02 - GH-2004 Swift converted to Mk2 specification, broken up in 2004 at the Hovercraft Museum
• 03 - GH-2005 Sure 1968, converted to Mk2 specification in 1972, broken up in 1983 for spares
• 04 - GH-2007 Princess Anne converted to Mk3 specification in 1978
• 05 - GH-2008 Sir Christopher 1972, converted to Mk2 specification in 1974, broken up 1998 for spares
• 06 - GH-2054 The Prince of Wales built as Mark 2

• Length:

Mark 1 and 2: 39.68 m

Mark 3: 56.38 m

• Beam: 23.77 m
• Height: 11.48 m (on landing pads)
• Gross Weight

Mark 1: 165 t

Mark 2: 200 t

Mark 3: 320 t

• Powerplant: 4 x 3,400 shp Rolls-Royce Proteus Gas turbines (3,800 shp in Mark 3)
• Load:

Mark 1:30 cars and 250 passengers

Mark 2: 36 cars and 278 passengers

Mark 3: up to 60 cars and 418 passengers (112 t maximum)

• Max speed: Mark 1 - 65 knots (calm water, zero wind, at gross laden weight)
  Mark 2 - 70 knots
• Normal operating speeds: 40 - 60 knots
• Endurance: 4 hours (maximum power, 2,800 Imperial gallons of fuel)
• Gradient: 1 in 11

• N500 Naviplane

• SR-N4 Hovershow 05 Pictures

1. ^ Hovercraft Facts. 1966: Hovercraft deal opens show. BBC.

• Hovercraft Museum on the Mark 1
• Hovercraft Museum on the Mark 2
• Hovercraft Museum on the Mark 3