The concept is part of a DARPA X-Plane program to develop a Class 3 Unmanned Aerial System (UAS) Vertical Take Off and Landing aircraft that doesn't need special infrastructure on land or aboard ship, and can fly in "most weather conditions."

The initial contract for the project was awarded to Sikorsky Innovations – the company's rapid prototyping group – back in 2013, with company president Paul Lemmo recently confirming that flight testing has been undertaken for at least the last 18 months as part of an earlier development phase.

Sikorsky says that the rotor blown wing design – which looks quite similar to Boeing's Heliwing project from the mid 1990s – was selected because "the constant airflow from the proprotor wash across the wing reduces drag in hover mode and when transitioning to forward flight, increasing cruise efficiencies and endurance."

When not in the air, the unmanned aircraft rests on four feet with its nose and twin proprotors pointing skyward. It takes off from this position, and then transitions to horizontal forward flight for long-haul intelligence, surveillance, recon and targeting missions.

The tail-sitter features the company's MATRIX autonomous flight control system, a hardware/software combination developed as part of another DARPA program to enable "autonomous flight in obstacle-rich environments" and also benefits from an articulated rotor setup that's similar to systems found in helicopters. Returning to base, it moves from horizontal flight to land vertically like a helicopter.

The battery-powered proof-of-concept prototype is currently undergoing flight tests to confirm stability during vertical take-off and landing operations, as well as efficient horizontal cruising.