The SR.N4 is one of the world's largest commercial hovercraft and is designed for passenger / vehicle ferry operations on stage lengths up to 185km (100 n miles) on coastal water routes.

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Cutaway schematic view of the SR.N4 Mk I (large file)
A plan view of the craft showing the internal layout
Sectional elevations showing how the craft can accommodate coaches

TYPE

165 Tonne amphibious passenger / car transport
Powerplant: 4 x 3,400shp Rolls Royce Marine Proteus Gas Turbines

EXTERNAL DIMENSIONS

Overall Length: 39.68 m
Overall Beam: 23.77 m
Overall Height on landing pads: 11.48 m
Skirt Depth: 2.44 m

INTERNAL DIMENSIONS

Vehicle Deck Headroom - centreline: 3.43 m
Bow Ramp Door aperture size (h x w): 3.51 m x 5.48 m
Stern Door aperture size (h x w): 3.51 m x 9.45 m

WEIGHT / CAPACITY

30 cars & 250 passengers
Normal Gross weight: 165 tons

PERFORMANCE
(at normal gross weight at 15 ºC)

Max. water speed over calm water, zero wind (continuous power rating): 65 knots
Average service water speed: 40 - 60 knots
Operation: Up to gale force 6
Normal stopping distance from 50 knots: 480 m
Endurance at maximum continuous power on 2,800 Imperial Gallons: 4 hours
Negotiable Gradient from standing start: 1 in 11

A graph showing engine power generated by different turbine speeds
A graph showing how wind speed affects water speed in operational conditions

CRAFT BUILT

(Yard No 001) GH-2006 Mountbatten Class Prototype
Prototype SR.N4 craft cost £1.75 million
Launched at East Cowes 4 February 1968
First Channel crossing Dover to Boulogne 11 June 1968
Later handed over to Seaspeed and named The Princess Margaret

(Yard No 001) GH-2006 The Princess Margaret
First commercial service Dover to Boulogne 1 August 1968
Converted to Mk III craft September 1978 to April 1979 (See the Conversion Page for images)
Re-launched at Cowes as Mk III on 23 April 1979
Last service Calais to Dover 1 October 2000
Total Hours Logged to 30 September 2000: 48,195
Retired to Lee-on-Solent for lay-up 16 December 2000
Awaiting sale or a decision on its future. See www.ferries4sale.com

(Yard No 002) GH-2004 Swift
Rolled out as MK I craft at East Cowes 10 December 1968
First commercial service Ramsgate to Calais 2 April 1969
Converted to Mk II craft 1972 / 73
Last Service Calais to Dover 29 September 1991
Total Hours Logged to end of 1989 (few hours between 1989 and 1991): 22,419
Laid up 1993 and on 25 June 1994 donated to the trustees of the Hovercraft Museum
Currently preserved at the Hovercraft Museum Lee-on-Solent

(Yard No 003) GH-2005 Sure
Rolled out as Mk I craft at East Cowes 1968
Officially named & first commercial service Ramsgate to Calais 3 June 1969
Converted to Mk II craft 1974
Last Service Calais to Dover 1983
Total Hours Logged to 1983: 17,852
Broken up at Pegwell Bay in 1983 for use as spares for the other craft

(Yard No 004) GH-2007 The Princess Anne
Rolled out as Mk I craft at East Cowes 1969
First commercial service Dover to Boulogne 8 August 1969
Converted to Mk III craft February 1977 to April 1978 (See the Conversion Page for images)
Re-launched at East Cowes as Mk III on 6 April 1978
Set a new cross-Channel record of 22 minutes on the 10.00am flight on 14 September 1995
Last service Calais to Dover 1 October 2000
Total Hours Logged to 30 September 2000: 46,418
Retired to Lee-on-Solent for lay-up 3 December 2000
Awaiting sale or a decision on its future. See www.ferries4sale.com

(Yard No 005) GH-2008 Sir Christopher
Rolled out as Mk I craft at East Cowes in May 1972
First commercial service Ramsgate to Calais 3 July 1972
Converted to Mk II craft 1974
Last Service Calais to Dover 29 September 1991
Total Hours Logged to end of 1989 (few hours between 1989 and 1991): 19,116
Laid up early 1993 pending possible sale
Broken up at Dover in 1998 for use as spares for the two remaining Mk III craft

(See SR.N4 Mk II page for technical descriptions)

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