Derived from the launch and recovery system for the Thales Watchkeeper fixed-wing tactical UAS, D2AD includes a shipboard segment using radar sensors for guidance and motion-prediction software to anticipate the ship's movement. The flight segment, which functions independently of GPS and is adaptable to different types of UAVs, involves an airborne beacon and deck-lock harpoon that engages a landing grid and holds the aircraft to the flight deck.

“To the best of our knowledge, even the U.S. today has not gone so far in the experimentation of this system,” says Pierre Legros, senior vice president of the surface ships and naval systems division at DCNS.

DGA awarded the D2AD contract in 2008, giving Thales responsibility for the positioning system and UAS interface, supply of a demonstrator aircraft and slaving of its flight path along a trajectory. Majority-state-owned DCNS is responsible for predicting ship motion, the harpoon system, and system interface and integration with the vessel.

When operating in high seas, the motion of vessels will vary with size, hull design and stabilization system. When alighting on such a platform, a helicopter pilot must observe the heave, pitch and roll motion of the deck to determine when to land through a combination of aircraft capability and gut instinct.

With D2AD, a pilotless aircraft approaching a ship in rough waters and inclement weather begins transmitting its position and heading to a pair of receivers on opposite sides of the flight deck. The receivers triangulate the signal and a correction order is sent to the helicopter.

The system's sophistication, however, has less to do with triangulating sensors than choreographing a sort of dance between the aircraft and the ship using DCNS-developed motion prediction algorithms that make it possible to anticipate the vessel's movement. When this information is conveyed to the helicopter, the aircraft is able in response to mimic the ship's pitch and heave and anticipate roll as it lands.

“The interface is simple, but the intelligence is not in radar, it is in the prediction of movement,” Legros says.

Such delicate maneuvering was performed accurately during the sea trials. Legros says the helicopter was manned to ensure safety during testing, but with “no hands on the controls.” He says the system's demonstrated reliability and precision offers the potential to become a standard component of all naval helicopters.

“The pilot in the helicopter doesn't have any means to anticipate the movement of the platform,” he says. “At the end of the day, this system should be more precise, more accurate and safer than normal helicopter operation.”