SR.N4

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Mark 3 SR-N4 Hovercraft arriving in Dover on its last commercial flight - October 1, 2000

The Mountbatten class hovercraft or SR-N4 (Saunders Roe Nautical 4)[1] was built by the British Hovercraft Corporation (BHC). BHC was formed by the merger of Saunders-Roe and Vickers Supermarine in 1966. Work on the SR-N4 began in 1965 and the first trials 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 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).

Service

The craft entered commercial service in August 1968, with the Princess Margaret (of British Rail's Seaspeed) 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[2], for the 10:00 a.m. service.[3]

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 56.1 ft (17.1 m), increasing capacity to 418 passengers and 60 cars at the cost of a weight increase to almost 265 long tons (269 t). To maintain speed the engines were upgraded to four 3,500 shaft horsepower (2,610 kW) Rolls-Royce gas turbines fitted with four enormous 21 ft (6.4 m) 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 11 ft 6 in (3.5 m) high and with 57.5-mile-per-hour (92.5 km/h) winds. The stretched SR-N4s (Super-4's) became the world's largest hovercraft, holding this title until the Russian's Zubr class LCAC hovercraft's arrival in the early 00's.

The two main commercial operators (Seaspeed and Hoverlloyd) 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.

Ride

One passenger recalled the experience of the ride: "The ride was quite noisy, more like a ride on a noisy turboprop airliner than a boat. Unless calm, the motion was also rather abrupt as waves struck the vessel, producing a synchronized head toss action of the passengers."

Military

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.

Survivors

The two remaining Mk3 examples of the craft (GH-2006 Princess Margaret and GH-2007 Princess Anne) reside at the Hovercraft Museum. Their long-term fate is unknown, though a proposal by Hover Transit Services of Bolton, Ontario would put the hovercrafts back in operation (following a $10 million USD purchase and refurbishment) on Lake Ontario with service between Rochester, NY and Toronto, Ontario.

Production

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, scrapped due to electrical fire.

Specification

Dimensions

  • 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
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)

Performance

  • 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

See also

External links

References

  1. ^ "James' Hovercraft Site: SRN4". Retrieved 2008-03-22.
  2. ^ "Hovercraft Facts". 1966: Hovercraft deal opens show. BBC.
  3. ^ "Hovercraft". Dover - Lock and Key of the Kingdom. www.dover-kent.co.uk. Retrieved 2008-01-23.
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