Saunders Roe Nautical 4

SR.N4 Mk.III in Calais

SR.N4 Mk III on the last day of operation, October 1, 2000

Driving from a SR.N4 Mk II in September 1977

Arrival of Sir Christopher

The Saunders Roe Nautical 4 (SR.N4) , also known as the Mountbatten class , was a class of British hovercraft . The hovercrafts were built by the British Hovercraft Corporation in East Cowes on the Isle of Wight between 1968 and 1977 and were in service until 2000. The SR.N4 Mk.III were after the Zubr class the largest air-cushion vehicles that were ever built.

history

Construction and commissioning

Play media file

Landing of a hovercraft in Calais

Play media file

Boarding a hovercraft with a motor vehicle

In 1965, the Hoverlloyd shipping company opened the first connection between Ramsgate and Calais across the English Channel with pure passenger hovercrafts . At the same time, the Saunders-Roe shipyard began developing a larger hovercraft for transporting passengers and cars . The SR.N4 Mk I should not only have a larger capacity, but also be able to be used reliably in bad weather. Due to their construction, the previous models could only operate on the English Channel in the summer season. In 1966, Saunders Roe merged with competitor Vickers Supermarine to form the British Hovercraft Corporation . In the same year Hoverlloyd ordered three SR.N4s for the connection from Ramsgate to Calais. Seaspeed , a subsidiary of British Rail , ordered two more hovercrafts for the route from Dover to Boulogne .

On February 4, 1968, the prototype of the SR.N4 started its first test run on the Solent, with top speeds of almost 60 knots being reached. The first crossing of the English Channel took place on June 11 of the same year from Dover to Boulogne. After the completion of the test drives, the prototype was christened The Princess Margaret and started the regular service between Dover and Boulogne on August 1st. On April 2, 1969, the Swift began operating on the Hoverlloyd connection from Ramsgate to Calais. At the end of the year, two hovercrafts were available on both lines, the Sura and The Princess Anne . During the 1971/72 winter season, Seaspeed first used a hovercraft on the connection from Dover to Calais. On July 3, 1972, Hoverlloyd put the third SR.N4 into operation, which was named Sir Christopher in honor of the inventor Christopher Cockerell . So-called hover ports were built to handle the SR.N4, which initially consisted of a concrete surface. The hovercraft drove straight out of the water onto these areas and were loaded and unloaded there via a bow and stern ramp. Since they were constructed in the RoRo design , it was possible to completely unload and load them in less than 15 minutes.

modification

In 1973 Hoverlloyd began converting its SRN.4 Mk I , which was then given the designation Mk II , and at the same time ordered a fourth hovercraft, The Prince of Wales , which was to be built according to the Mk II standard. The inside cabins of the vehicles were removed to enlarge the car deck . The main cabins, on the other hand, have been enlarged outwards to be able to transport more passengers. The capacity could thus be increased by 28 passengers and six cars. Even before the conversion, all SR.N4 had received a new apron so that they could also be used in heavy seas. In 1976 Seaspeed decided to undertake a much more radical renovation than Hoverlloyd had done. By adding a new middle section, the hovercraft should be extended by 16 meters. The performance of the four turbines was increased by 400 hp each and Rolls-Royce designed new propellers with a larger diameter. The passenger capacity of the new Mk III had now been expanded to 418 seats, with space for up to 52 cars on the car deck. Almost 1 ton of fuel was used on the route between Dover and Calais .

The end of the SR.N4

An SR.N4 Mk.II leaves Dover

In 1981 Hoverlloyd and Seaspeed merged to become Hoverspeed . The less profitable connection from Ramsgate to Calais was closed, the connections from Dover to Calais and Boulogne intensified. In 1983 the company decided to retire the Sure as the first SR.N4, as the operation of six hovercrafts appeared unprofitable.

In September 1991 Hoverspeed retired the three remaining SR.N4 Mk II . They were replaced by catamarans on the route from Dover to Boulogne . A major reason for the retirement was that Rolls-Royce had stopped producing the propellers. There was also a general lack of spare parts. The two Mk IIIs continued to operate, however, partly with spare parts from the decommissioned Mk IIs , as the catamarans proved to be relatively unreliable and the capacity utilization did not meet expectations. In the following nine years, the two remaining hovercrafts continued to generate profits, with an annual average load factor of around 70 percent.

On October 2, 2000, the two SR.N4 Mk IIIs were also replaced by two catamarans and the reason given was that the hovercrafts could not hold enough vehicles and their passengers could not get up during the journey, for example to go shopping. The catamarans offered around 50% more capacity, but needed around 50% more travel time. The decision met with a lot of incomprehension among passengers and employees. For the shipping company Hoverspeed, the decommissioning of the hovercraft proved to be fatal. In November 2005 she had to file for bankruptcy due to insufficient utilization of the catamarans.

The whereabouts of the SR.N4

The Princess Margaret at the Lee-on-Solent Hovercraft Museum 2008

Propeller in Dover Harbor 2012

Of the original six SRN4, the two until recently used copies The Princess Anne and The Princess Margaret have survived . The latter example serves as a spare parts store for The Princess Anne . Both examples are now on the grounds of the Hovercraft Museum in Lee-on-Solent , UK. In November 2005 these were sold to the British millionaire Wensley Haydon-Baillie for £ 500,000 and the museum lacked the necessary funds to purchase and maintain. In early 2006, however, Haydon-Baillie had indicated that the museum would leave at least one of the two hovercrafts permanently. The third Swift was acquired by the museum in Lee-on-Solent in 1994, but had to be scrapped in 2004 due to its poor condition. The hovercrafts Sure and Sir Christopher were scrapped in 1983 and 1998, respectively, as was The Prince of Wales , after this one was badly damaged by fire on April 2, 1993 in Dover.

Records

With a curb weight of 265 and a maximum weight of 320 tons, the SR.N4 Mk III were the largest civil hovercraft ever built. Its propellers were the largest in the world with a diameter of 6.4 meters. On September 14, 1995, the hovercraft The Princess Anne set a new record for crossing the English Channel. It took 22 minutes to get from Calais to Dover, two minutes less than the Swift a few years earlier. This record has not yet been broken.

Accidents

On October 29, 1969, a Sure propeller came loose during take-off from Ramsgate and damaged the terminal building. As a result of the incident, all four SR.N4 were shut down immediately, but were able to resume operation after just 48 hours. It turned out that when the propeller was replaced the day before, some bolts had only been insufficiently fastened. The most momentous accident involving a hovercraft happened on March 30, 1985. In rough seas and strong winds, the hovercraft The Princess Margaret collided with the harbor wall as it entered the port of Dover and was torn open over a length of more than ten meters. Nevertheless, the captain still managed to reach the hoverport. Four people were killed in the accident and 50 were injured. The investigation report later determined that a conventional ferry would have sunk immediately after such a collision and that it was thanks to the construction of the SR.N4 that not more people were killed.

Data

	SR.N4 Mk I.	SR.N4 Mk II	SR.N4 Mk III
Weight (max.)	165 tons	200 tons	320 tons
length	39.68 m		56.38 m
width	23.77 m
Top speed	65 knots	70 knots (129 km / h)
Cruising speed	60 knots
Range	450 km
power	4 × 3400 hp		4 × 3800 hp
Can be used up to wind strength	6th	8th	9
Passengers	250	278	418
Car	30th	36	52

Produced SR.N4

hovercraft	Identifier	completion	Commissioning	Retirement	Whereabouts	Remarks
The Princess Margaret	GH-2006	4th February 1968	1st August 1968	October 1, 2000	Scrapped in 2018	Converted to Mk III standard in 1978.
Swift	GH-2004	December 10, 1968	2nd April 1969	September 29, 1991	Scrapped in 2004	Converted to Mk-II standard in 1972
Sure	GH-2005	1968	3rd June 1969	1983	Scrapped in 1983	Converted to Mk-II standard in 1974
The Princess Anne	GH-2007	1969	August 8, 1969	October 1, 2000	Hovercraft Museum Lee-on-Solent	Converted to Mk III standard in 1977
Sir Christopher	GH-2008	May 1972	3rd July 1972	September 29, 1991	Scrapped in 1998	Converted to Mk-II standard in 1974
The Prince of Wales	GH-2054	1976	June 18, 1977	September 29, 1991	Destroyed by fire on April 2, 1993	Constructed as Mk II from the start