Passenger Hovercraft

Overview

A passenger hovercraft is an amphibious air-cushion vehicle (ACV) that carries fare-paying passengers over water, mud, ice and gently shelving shore. It rides on a contained bubble of slightly pressurised air rather than floating in the water or rolling on wheels, so it can cross the surf line, beach itself on a concrete pad and unload passengers without a harbour. The craft modelled here is a 30-seat coastal ferry of roughly 21 m length and 18 t all-up weight, powered by two marinised turbo-diesel engines and capable of 35-45 knots in service.

The defining feature is amphibious operation. Because the Skirt System seals a cushion of air beneath the entire craft, there is no hull dragging through the water and no draught to speak of. A hovercraft can run from a slipway, over sandbanks that would ground a conventional ferry, across tidal flats and onto a hard standing, all in one continuous run. That capability is what justifies the cost and complexity over a fast catamaran on routes with awkward terminals.

Buoyancy Raft and Structure

The backbone of the craft is the Buoyancy Raft & Hull, a buoyancy raft built from glass-reinforced plastic with an aluminium deck grid bonded on top. Sealed Buoyancy Tank units, filled with closed-cell PVC foam, give the craft positive flotation even if it is swamped, so a hovercraft that loses cushion pressure settles gently onto the water rather than sinking. The Deck Structure uses extruded 6082-T6 aluminium frame members and composite floor panels to carry the engines, cabin and passenger load while keeping mass low, since every kilogram has to be lifted by fan power. A moulded Bow Fairing shapes the airflow into the skirt and a polyurethane Rubbing Strake protects the raft edge when berthing.

How the Air Cushion Works

Lift and propulsion are separate functions on this craft. The Lift System uses a centrifugal Centrifugal Lift Fan, around 1.2 m in diameter, to draw in air and pressurise the Plenum Chamber beneath the deck. Air flows out through Lift Air Duct runs into the skirt bag and then escapes under the skirt, and the steady leak is exactly what keeps the craft floating: the fan replaces escaping air faster than it can leave, holding the cushion at roughly 2 kPa above atmospheric. That pressure, spread over the full plan area, supports the entire 18 t weight while the craft hovers a fraction of a metre clear of the surface.

The Skirt System is a bag-and-finger design. A pressurised loop bag forms the deep outer wall and dozens of replaceable Skirt Finger segments hang from its lower edge, each flexing independently so the craft can ride over waves, ditches and curbs of up to about 0.9 m without losing the cushion. Fingers are consumable: they abrade on shingle and concrete and are unbolted and swapped at the Skirt Attachment Rail rails as routine maintenance.

Thrust comes from the Propulsion System system, a variable-pitch ducted Ducted Airscrew roughly 2.5 m across mounted on a Thrust Pylon above the deck. A GRP Propeller Duct Shroud raises static thrust and protects the blades, while the Variable-Pitch Hub lets the crew adjust blade angle, and even reverse pitch, for braking and manoeuvring. Steering is aerodynamic: a bank of Air Rudder vanes in the slipstream behind the airscrew swings the thrust line, and Elevon Surface surfaces trim pitch and yaw. Because a hovercraft has almost no grip on the surface, the crew flies it more like an aircraft than drives it like a boat, anticipating drift and crabbing into wind.

Powertrain and Controls

The Engine & Powertrain is built around two marinised Marine Diesel Engine units of about 250 kW each. A Power Split Gearbox using a cast Gearbox Housing and hardened Helical Gear Pair sets splits engine torque between the lift fan and the airscrew, with a Power-Take-Off Clutch able to declutch the lift drive on the ground. Diesel is held in baffled aluminium tanks in the Fuel System, filtered through water-separating elements before injection. The Engine Cooling System rejects engine heat through an air-blast radiator fed by the airscrew slipstream, which avoids the raw-water intakes that would clog with shingle on a beaching craft.

Control surfaces are moved by the Control System hydraulics. A Hydraulic Power Pack power pack supplies oil at around 150 bar to Hydraulic Actuator cylinders on the rudders and elevons, commanded from the Helm Console.

Cabin, Avionics and Electrical

Passengers ride in the Passenger Cabin, an insulated GRP shell fitted with up to thirty Passenger Seat units, tinted polycarbonate Cabin Window panels and sliding Boarding Door openings for boarding off a pad. Acoustic lining is important because lift fans and airscrews are loud, so the cabin carries a mass-loaded Acoustic Lining and a Cabin HVAC Unit unit that uses Heating Element heaters and a blower to temper the air.

Navigation runs on the Navigation & Avionics suite: an X-band Marine Radar for collision avoidance, a GNSS Receiver receiver, a VHF Radio for traffic and distress, and LCD Panel chartplotters at the helm, with a Pressure Sensor reporting cushion pressure so the crew can watch for skirt damage. The Electrical System system is 24 V DC, charged by engine Alternator units into AGM batteries and split through a breakered Distribution Panel feeding the Wire Bundle loom.

Materials and Variants

Materials are chosen for low mass and salt resistance: GRP for the raft, cabin and ducts, marine-grade aluminium for the deck grid and pylon, and neoprene-coated nylon for the skirt. Composite airscrew blades carry polyurethane leading-edge guards against spray erosion. Variants of the basic layout range from small 6-12 seat coastal craft to large car-and-passenger ferries such as the historic SR.N4 cross-Channel hovercraft, and military landing-craft versions like the LCAC that put the same lift-and-skirt principle to amphibious assault use. Civil passenger hovercraft remain in scheduled service on routes where terminals are awkward, the most enduring being the Isle of Wight crossing in England.

Use Cases

Passenger hovercraft earn their keep where conventional ferries cannot dock easily: tidal estuaries, shallow river deltas, ice-bound northern rivers and beaches without harbours. They support search and rescue over mud and ice, coastal patrol, and disaster relief into flooded areas where boats ground and roads are cut. The trade-offs are high noise, sensitivity to strong crosswinds and demanding maintenance of the skirt and powertrain, so they suit dedicated routes rather than general service.