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TYPE

320 Tonne amphibious passenger / car transport
Powerplant: 4 x 3,800shp Rolls Royce Marine Proteus 15m / 529 Gas Turbines
Auxiliary Power: Two Rover turboshaft engines driving 55kVA 200V, 400Hz Lucas alternators

EXTERNAL DIMENSIONS

Overall Length: 56.38 m
Overall Beam: 23.16 m
Overall Height on landing pads: 11.43 m
Mean Skirt Depth: 2.70 m

INTERNAL DIMENSIONS

Vehicle Floor Area: 631 mē
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

Maximum Gross: 320 tons
Maximum Disposable Load: 112 tons
Typical Fuel Load: 20 tons
Maximum fuel tankage: 28.45 tonnes
Normal Fuel allowing for ballast transfer: 18.29 tonnes
Payload: 54 - 60 cars, 418 passengers

PERFORMANCE
(typical cruise water speeds)

Calm (2ft waves, 5 knots wind): 60 - 65 knots
Moderate (5ft waves, 20 knots wind): 50 - 55 knots
Rough (8ft waves, 27 knots wind): 35 - 45 knots
Operation: Up to gale force 8
Endurance per ton of fuel: 0.23 hour

CRAFT CONVERTED

(Yard No 001) GH-2006 The Princess Margaret
Launched at East Cowes 4 February 1968
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 East Cowes as Mk III on 23 April 1979
Accident on 30 March 1985 - struck the Dover Harbour wall. (See the Accident Page for details)
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 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

NOTES

The Mk III differs from earlier marks of the SR.N4 primarily in that it is 16.76m longer, increasing the overall length to 56.38m with a beam of 28.04m.

Modification of an SR.N4 Mk I to Mk III standard necessitates adding a new 16.76m section amidships, widening the existing superstructure and strengthening the original bow and stern halves to accept the increased stresses resulting from the 40% increase in length. The propeller pylons are raised to allow 6.4m diameter propellers to be fitted, the transmission systems are realigned and four uprated 3,800 shp Rolls Royce Marine Proteus gas turbines are installed. A more efficient low-pressure ratio skirt system with larger fingers is fitted, giving a mean air cushion depth of 2.7m.

Passenger cabin trim and seating have been completely revised and sound-proofing increased. Compared with the SR.N4 Mk I, the Mk III has a 70% greater revenue earning capability, but costs only about 15% more to operate. The increased length and advanced skirt system give both a higher performance in adverse weather and greatly improved ride comfort for the passengers. Craft handling and skirt behaviour have proved completely satisfactory over the entire weight range from 212 to 300 tons in sea conditions up to force 8 to 9. Measurements taken in the passenger cabins of acceleration forces show a three fold improvement in ride comfort over the SR.N4 Mk II. The uprated Rolls Royce Marine Proteus gas turbines have been trouble-free and the new propellers have substantially reduced external noise when operating into and out of hovercraft terminals. The Mk III has a payload capacity of 418 passengers and 60 vehicles, a laden weight of 320 tons and a top speed in excess of 65 knots.

LIFT AND PROPULSION

Motive power is supplied by four Rolls Royce Marine Proteus Type 15M / 529 free-turbine turboshaft engines located in pairs at the rear of the craft on either side of the vehicle deck. Each engine is rated at 3,800 shp continuous under ISA conditions and is connected to one of four identical propeller / fan units, two forward and two aft. The propellers, made by British Aerospace Dynamics, are of four-bladed, controllable pitch type D258 / 485A / 2. The lift fans, made by BHC are of the 12 bladed centrifugal type, 3.5m in diameter. Auxiliary Power is provided by two Lucas turboshaft engines driving 55kVA 200V, 400Hz Lucas alternators.

 

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