Small robotic spy-planes have been developed that use shape-shifting wings to switch from being stable gliders to ultra-manoeuvrable fliers.
The articulated wings – with a span of 60 centimetres – were inspired by the way seagulls alter their wing-shape during flight, says Rick Lind, an aerospace engineer at the University of Florida, in Gainesville, US.
The robot plane, or drone, has a joint halfway along the leading edge of both its wings. Actuators at this “elbow” joint and at the “shoulder” joint of each wing, where it connects to the fuselage, allow the wing structure to shift from an “M” to a “W” configuration, as viewed from the front or rear.
With the elbow lowered, the “W” configuration produces a highly manoeuvrable aerodynamic shape, says Lind. In contrast, the high elbow “M” shape is less manoeuvrable but highly stable, perfect for gliding and conserving battery power.
The change in flight performance comes partly from a shift in the aircraft’s centre of gravity, says Lind: “With the wing position higher than the centre of gravity it is stable like a pendulum.” Reversing this – the “W” position – produces low stability, like an inverted pendulum. See a movie of the craft showing off its different in-flight configurations, here.