Farnborough 2010 (July.10) Boeing – A US aerospace company’s massive showing, included its own unmanned air vehicle pavilion. With an 11m (36ft) rotor diameter nearly as wide as the 10.7m autonomous helicopter is long, it is larger than other vertical take-off UAVs. But weighing in at 1,135kg (2,500lb), with its largely composite frame, it is also lighter, making up for the fact that it carries 45kg more than its weight in fuel. However, what makes the A160 unique is not something visible in its low-drag, reduced radar profile silhouette.
In conventional helicopters, the revolutions per minute of the rotors is normally locked in for a maximum forward speed, given weight and altitude considerations. At maximum forward speed, the tip of the advancing blade moves at speeds slightly under Mach 1, avoiding the drag and vibration seen at higher speeds. But being locked into a constant maximum rotor RPM also means that anything less that maximum forward speed – a hover, low-speed forward flight – the rotor is moving far faster than actually necessary, wasting fuel and creating drag, shortening the helicopter’s range. Humming Bird so far managed to fly at the speed of 165kt (305km/h) – with a service ceiling of between 20,000ft and 30,000ft and a range of around 2,500nm (4,620km). It is its blades that makes it unique, for range and speed compared to other in its class. For A160, the stiffness and cross-section of the rotor blades vary along their length. The low-loading hingeless design allows for changing RPMs to optimise efficiency at different speeds and altitudes. The Hummingbird has come a long way since the diesel-powered, variable-speed rotor experiment that was awarded a 30-month technology demonstration contract in March 1998. The first true Hummingbird prototype, a three-bladed design, debuted in December 2001 and had its first forward flight the following month at former US Air Force base at Victorville, California, using a Subaru engine.
In September 2003, DARPA awarded Frontier a $75 million contract for the design, development and testing of four A160s. By May 2004, Boeing had purchased Frontier from Karem. In August 2005, Frontier Systems – now a Boeing subsidiary – received a $50 million contract from the Naval Air Warfare Center Aircraft Division to examine the affordability of long-range VTOL UAVs for payload delivery. With no orders on the books, Boeing made the decision in late 2009 to put the helicopter into production, an unusual move in a business where manufacturers usually wait for a contract award or at least a military requirement before opening production. The A160 has already demonstrated its ISR capabilities to the US Army, as far back as 2008, at an annual C4ISR exercise at Fort Dix in New Jersey. Operating at the army’s Class IV UAV for the exercise, the Hummingbird integrated five different payloads for the event, Lavoranda says, including a 380mm (15in) Wescam electro-optical/infrared sensor ball and two mini tactical common datalink transceivers used to downlink full motion video from the EO/IR sensor Rover terminals to both mounted and dismounted troops with Rover terminals. The Hummingbird also proved its role as a communications relay, keeping two Humvees in contact when they moved out of the line of sight. In March, during six flights in two days, the A160 demonstrated its autonomous cargo delivery capabilities to the Marines, Wattam says, consistently delivering sling-loaded cargo within 1.2m of the target drop site. Furthermore, the A160’s proprietary, portable ground control system makes it possible to deliver cargo without a trained UAV pilot at the delivery site. After the UAV flies its pre-planned route, it stops and orbits until someone at the forward delivery location instructs it, with the touch of a button, to proceed to the inbound delivery point. Once there, another click tells it to hover over the delivery point. Adjustments can be made within a 1km range of the original delivery site before instructing the Hummingbird to lower its load, release the cable and head home on its predetermined path.
Unmanned Cargo Resupply Contract
According to the Sources Lockheed, together with manufacturer Kaman Aerospace, will get $45.8 million to operate the K-Max – who is copable of carrying 2721.6kg (6,000lbs) of cargo at sea level and more than 1,814.3kg (4,000lbs) at 10,000ft – while Boeing will receive $29.2 million to use its A160T Hummingbird to deliver cargo to Marines in Afghanistan. The Hummingbird, designated the YMQ-18A by the Pentagon, with its patented adjustable rotor speed technology, holds the record for endurance in its class, at 18.7h. In August 2010 the A160T Hummingbird underwent jungle test flights in Belize to test the ability of DARPA FORESTER foliage-penetrating radar to penetrate jungle cover. What makes this UAV unique is the incorporation of many new technologies – such as advance composite materials, Optimum Speed technology, ability to shift to another gear, and finally fthe uselage’s two large, stiff monocoque skins which help keep the frequency ranges of the structure outside the frequency ranges of the rotor as it changes its speeds.