An all-electric “seaglider” that can transition between floating and flying has begun sea trials in Narragansett Bay, Rhode Island. The tests are a prelude to the vehicle’s first crewed flights, scheduled for later this year, which would make it the largest battery-powered flying machine in the world – albeit one that must remain just above the water’s surface.
Electric aircraft are tricky because they must carry heavy batteries, which add to their overall weight and reduce their flight range. The Viceroy seaglider, developed by US company Regent Craft, achieves energy-efficient flight with a phenomenon called the “wing-in-ground” effect, says at Embry‑Riddle Aeronautical University in Florida, who is not affiliated with Regent.
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With this technique, a cushion of air forms between a low-flying aircraft and the ground or water below. The cushion supports the vehicle and reduces its aerodynamic drag by preventing swirling patterns of air from forming at its wingtips.
“The drag on an airplane is less than the drag on a boat, and the wing-in-ground effect is making [the seaglider] even more efficient than an airplane,” says Anderson.
Few vehicles take advantage of this effect because it works only for low flying and, even then, only over flat surfaces, such as calm seas without tall waves. To let the seaglider manoeuvre in rougher waters if necessary, Regent added a hydrofoil capability.
From floating in the water like a boat, the seaglider can transition to hydrofoil mode by traveling fast enough so that the main body lifts out of the water – with help from wing-like fins underneath. Then the seaglider can lift from hydrofoil mode to become completely airborne, although it must fly within just a single wingspan – in this case, 20 metres – above the waves.
“We’re a boat where it makes sense to be a boat, but we can be a very fast and very wave tolerant boat,” says , cofounder and CEO of Regent. “Then as we leave the harbour, we can take off from those hydrofoils to fly over the water.”
Regent plans for its seaglider, which can carry 12 passengers and two crew members, to make transportation between coastal cities easier and cheaper. The Viceroy has enough battery power to travel over 300 kilometres, and its top cruising speed of 290 kilometres per hour would make it significantly faster than any ship.
However, Anderson cautioned that the seaglider is also more complicated to operate than a ship. Regent’s solution has been to automate much of the control systems so that the crew members won’t need pilots’ licenses. “All the operator has to do is drive it like a boat – left, right, fast and slow,” says Thalheimer.
