London, Nov 25 : Two separate US researchers have created a new breed of robot helicopters and aeroplanes, which can land or "perch" on steep surfaces.

Eric Feron, an aerospace engineer, and colleague Selcuk Bayraktar from the Georgia Tech University, Atlanta, US, say that such drone aircraft could land on moving vehicles, unsteady ships or even hide inside caves.

"Birds and bats can alight in all sorts of positions very well, but [normal] aircraft are limited to level surfaces," New Scientist quoted Feron, as saying.

Feron's small autonomous helicopters can land on surfaces inclined at up to 60 degrees by flipping in the air to place all of its landing skids straight away.

Feron and Bayraktar worked out a way for their computer-controlled helicopters to execute the trick, using external cameras to follow the aircraft from several different angles, the report said.

The helicopter accelerates towards a Velcro-covered landing pad and, when near, tilts its rotor as far backwards as possible. That rolls it backwards in free fall, bringing its Velcro-covered skids, or feet, parallel to the landing pad to grip on. If the helicopter misses the landing, it performs a recovery manoeuvre to prepare for another attempt.

Feron plans to dispose of the Velcro by having the helicopter reverse its rotors.

On a similar tip, MIT researcher Jonathan How has fashioned another unique unmanned aircraft which can take off and land from a "prop hang" position, wherein the plane stands on it's tail in midair.

How and colleagues have found a way for small autonomous aeroplanes to land and take off vertically from a perch fixed to a wall, by hovering vertically in a trick known as a "prop hang".

How was inspired after watching a video of a skilled radio-controlled plane "pilot" making his aircraft hover while standing on its tail.

"We saw it is pretty hard, but at least we knew it could be done," he said.

The "prop hang" is predominantly challenging since all of the plane's controls are used and shifting one requires changing the others to compensate. The propeller provides lift, while the flaps on the wings prevent the body from spinning, and the tail controls the aeroplane's horizontal position.

How said he hopes to develop control software that can learn how to perform such manoeuvres with any aircraft.

"We had several instances where it didn't quite work," he said.

Experts believe that these new technologies will help get aircraft into and back out of complicated spots with a new level of manoeuvrability. (ANI)