Prox Dynamics' 15g (0.59oz) 100mm (3.93in) rotorspan PD-100 Black Hornet helicopter prototype Hornet-3a made its maiden outdoor flight on 7 April in Asker, Norway.

During two successful flights, the nano unmanned air vehicle (NAV) hovered and flew at up to 15.5kt (28.8km/h) in dry conditions with wind conditions reaching 3.89kt.

Demonstrating a 25min endurance, it was flown by remote control using a two-way datalink and an on-board fly-by-wire flight-control system for stability, aiding gust resistance. The helicopter is deliberately inherently unstable, says Prox Dynamics, to cope with winds. Hornet-3a more than doubled the endurance - the prototypes Hornet-1 and -2 flew for 10min only.

"We are now working on the next prototype 3b," says Prox Dynamics' marketing and government relations vice president, Dag Henning Paulsen. "Prototype four, which flies this summer, will have a shell."

Hornet-3a will be used to develop the autopilot that will use the global positioning system for autonomous waypoint navigation. Paulsen added that at a distance of about 3m (9.8ft), ambient noise makes the Hornet silent.

Prox Dynamics has flown five prototypes to date. All have had their rotor systems modified to improve performance. Paulsen expects that with aerodynamic optimisation, through better rotor layouts, the endurance can be increased to 30min.