Phoenix endurance aircraft takes flight in Portsmouth

Designed to operate at high altitudes for extended periods, the prototype vehicle has a 15m-long fuselage filled with helium and a wingspan of 10.5m. It propels itself using variable buoyancy, constantly shifting its weight to be lighter or heavier than the surrounding air, which creates thrust. This oscillation in weight is achieved by sucking in and compressing air to descend, then releasing that air to increase buoyancy.

“The Phoenix spends half its time as a heavier-than-air aeroplane, the other as a lighter-than-air balloon,” said lead designer Andrew Rae, Professor of Engineering at the University of the Highlands and Islands. “The repeated transition between these states provides the sole source of propulsion.

“The vehicle’s fuselage contains helium to allow it to ascend and also contains an air bag which inhales and compresses air to enable the craft to descend. This motion propels the aeroplane forwards and is assisted by the release of the compressed air through a rear vent.”