The system is derived from the ATOL system nearing readiness for the fixed-wing Watchkeeper UAV but features several modifications needed to operate at sea.
A single set of sea trials using an unmanned Boeing H-6U Little Bird rotorcraft should validate the concept from about mid-2012, depending on the availability of a French navy frigate.
According to Jean-Noel Stock, Thales vice-president for UAVs, intelligence and surveillance, the concept would then be worked into a future tactical UAV programme being run by France’s DGA research agency, with prospective deployment on appropriate platforms in about five years.
Trials carried out in the USA in June and July with a flatbed truck and the Little Bird demonstrated better accuracy than any other system, says Stock, with the DCNS-developed harpoon finding the same hole in a landing grid “every time”.
Separate trials on sloping ground and moving platforms simulating sea states as severe as five have proved the kinematic performance, so sea trials will focus on coping with such variables as side winds, air turbulence caused by deck movement and weather.
Stock adds that while an ATOL system is easier to develop for a rotorcraft – which can stop and start as it approaches its destination – than for a fixed-wing UAV, which must be guided along a continuous trajectory, shipboard operations pose far greater challenges than runway landings. A ship’s deck rolls and pitches, and accuracy is more critical than on a runway.
Also, adds Stock, on a naval vessel the deck is a strong electromagnetic environment that complicates design of the ATOL system.
Thus, says Stock, the so-called D2AD system incorporates DCNS expertise in predicting ship movement, so the system can tell the harpoon-equipped UAV when to make its final move toward the deck.
So as not to disturb a ship’s electromagnetic environment, D2AD is also designed to work with on-deck radar that is merely a passive receiver of the UAV’s responses to normal command and control signals. With a radar receiver on either side of the deck, the C+C system works out the UAV’s position and sends cues to the UAV’s flight controls to keep it on course.
Unlike laser-based systems, D2AD is not weather-dependent, and as the aircraft need carry only about 200g of hardware, it is suitable for any platform.
D2AD should also prove easy to integrate, adds Stock, as it provides guidance cues to the aircraft’s flight controls, but does not require access to its avionics software, which manufacturers understandably resist. For these reasons, D2AD could also be used as a secondary guidance system for manned helicopters, says Stock.
For now, the system is based on a Boeing Little Bird and French frigate, but Stock stresses that it is generic and could be adapted to any pair of platforms.
Dan Thisdell, Flight Global