Sydney, Jan 4 A study led by a scientist of Indian-origin has decoded the tricky art of landing by honeybees, a finding that can have huge implications in making better robot planes.

An automatic landing system for an aircraft is expensive and complex. And it is just one of many systems that is required to make a truly robotic aircraft. But a bee can take off, find targets, fly through tunnels, navigate home and land without any of that complexity.

Mandyam Srinivasan, whose work is followed closely by robotics experts around the world, led a team from the Vision Centre, the Queensland Brain Institute at the University of Queensland and Lund University, to find out how the insect speeds like an airplane and then suddenly morphs into a hovering chopper while delicately landing on a flower.

Unlike the 'controlled crash' of a fly landing, the bees land with utmost delicacy after 'reading' their airspeed visually, hovering above their landing ground and sensing it with vision, feelers and legs.

"As any trainee pilot knows, landing is one of the hardest things to do. It requires excellent coordination to get the speed, angle, distance and touchdown point exactly right — especially if, as in the case of the bee, the landing surface is sloping or even upside down," Srinivasan said.

The team used a special tiltable bee-landing platform and a high-speed camera to film the bees in the final moments of touchdown and identify each of their separate actions.

On approach to their target the bees use 'optic flow', the stream of visual signals provided by their eyes as the landscape speeds past, to slow down and move from forward-flight to stable hover mode about 16 mm from the platform, where they come to a dead stop.

They hover for a few thousandths of a second until their hind legs come in contact with the landing ground and they lower themselves gently onto it — regardless of the angle at which it is tilted.

However, when the bees land on surfaces ranging from vertical to upside down, their antennae comes closest to the surface during the hover phase.

The antennae graze the surface and this mechanical contact triggers the bees to reach up with the front legs, grasp the surface and then slowly heave their middle and hind legs up too, said a Vision Centre release.

"We hadn't expected the antennae to play a role. It adds a further dimension to the 'instrumentation' the bee uses in order to achieve the perfect landing," said Srinivasan, who has been studying honeybees for more than 20 years.