N500 Naviplane

The N500 Naviplane was a French hovercraft built by SEDAM (Société d'Etude et de Développement des Aéroglisseurs Marins) in Pauillac, Gironde.

Manufacture

Two models were built:

• N500-01 - "Côte d'Argent" First flight on April 19, 1977 on the Gironde, demonstrating a speed of 40-45 knots (74–83 km/h). She was destroyed by a fire at its construction site on May 3, 1977.
• N500-02 - "Ingénieur Jean Bertin" (built 1977). Built for Seaspeed by SNCF. Transferred to Hoverspeed in 1983 after a number of modifications but is returned to SNCF later that year after Hoverspeed decides she is not suitable for their services. Broken up in 1985 at the Boulogne Hoverport.

The N500 was one of the world's largest hovercraft; it could transport 400 passengers, 55 cars and 5 buses. It was also one of the fastest and reached a speed record for a travel from Boulogne to Dover at an average speed of 74 knots (137 km/h).^[1]

The mass of the N500 was 260 tons, it was 50 m long and 23 m wide.

French merchant navy registration

• N500-01 "Côte d'Argent" : LV 365.832 (port of Le Verdon, Gironde estuary).

• N500-02 "Jean Bertin" : BL 341.931 (port of Boulogne Sur Mer).

Crew

1 pilot. 1 co-pilot. Seated side by side in the cockpit. 1 radar-navigator seated at the rear part of the cockpit.

6 to 8 stewardess.

6 stower-men for the cars.

Flight control

Flight yokes controls the horizontal tail wing (elevator), propeller pitch and the thrust power of the 3 propulsion gas turbines

Rudder pedals control the two aerials rudders.

Two thrust levers controls power of the two lifting gas turbines.

Obturation flaps system between the air cushion chamber and the skirts providing additional longitudinal and lateral control.

Later modification (1983) includes:

• A third rudder on the middle engine pylon.
• Four air vents systems providing additional lateral control at low speed.

Specifications (N500)

General characteristics

• Crew: 15 to 17
• Capacity: 400 passengers distributed on the two half superior decks, 55 cars on the main deck
• Payload: 85 tons ()
• Length: 50 m (46 m)
• Wingspan: 23 m (22 m)
• Height: 17 m ()
• Empty weight: 118.25 tons ()
• Max takeoff weight: 240 tons ()
• Powerplant: 3 × Avco-Lycoming TF-40 marinised gas-turbines, 3,400 hp derated to 3,200 hp in commercial service for propulsion () each

Performance

• Never exceed speed: approx 78 Kts (sea level)
• Maximum speed: over 75 kts (sea level)
• Cruise speed: 65 kts to 70 kts (sea level)
• Stall speed: None (None)
• Range: 5 hours (approx 300-400 NM)
• Service ceiling: sea level (sea level)

Armament
None

Avionics
The navigator has two marine Decca radars (band S, 2-4 GHz, a 7cm and 10 cm wavelength), one slave radar for the pilot, two VHF radio. Anemometers, marine loch.

• Maximum continuous power: 16,000 shp
• Gas turbines revolution (max continuous): 14,500rpm
• Max Fuel: 20 metrics tons.
• Fuel consumption: 247gal/engine/hour, fuel type: Kerosene JP4/TR4.
• Oil capacity: 500 kg ?
• Propeller number: 3.
• Propeller diameter: 6.40 m.
• Propeller blades: 4. variable pitch with reverse
• Propeller manufacturers: Hawker Siddeley and Ratier-Figeac^[2]
• Propeller speed: 640 rpm

See also

• Aérotrain
• Mountbatten class hovercraft

References

1. ^ "Aérotrain et Naviplanes - L'histoire de la SEDAM et des Naviplanes". Aérotrain et Naviplanes. http://aernav.free.fr/Naviplane/Histo_Navi.html. Retrieved 2006-07-28. 
2. ^ Ratier-Figeac Propeller manufacturers

External links

• Les Naviplanes
• Transcript of a SEDAM publicity brochure
• N500 Naviplane gallery
• Images of the transfer of the "Ingénieur Jean Bertin" from its production site to Boulogne