Defense Technology International - September 2007 - (Page 14) TECH WATCH BILL SWEETMAN HUMMINGBIRD’S NEST Boeing’s A160T Hummingbird longendurance helicopter UAV is headed for fast-track tests of operational features for its first customer, U.S. Special Operations Command. Boeing flew the A160T in June, with a Pratt & Whitney PW207D turbine engine and a new transmission, giving it the power to fly at design weights. Between September and the end of the year, Boeing expects to perform long-endurance and heavy-payload test flights, conduct Hellfire missile firings and demonstrate the use of a 1,000-lb.-payload cargo pod. “You may see it deployed as early as 2008,” Boeing Advanced Systems President George Muellner said in June at the Paris air show. The A160T that flew in June is the second aircraft of this subtype; the first is engaged in endurance ground testing and a third is near completion. Until now, the program has been funded by the Defense Advanced Research Projects Agency (Darpa), but Socom is increasingly providing support. Since Boeing acquired Frontier Systems, the UAV’s developer, in 2004, aspects of the program have changed. Boeing decided at the end of 2006 that none of the hoped-for diesel engines was going to be ready for testing in time and switched to a single-track approach based on a certificated turbine engine. Reliability has been stressed: the lower vibration (compared with Subaru automotive engines in the earlier prototypes) will help. Frontier Systems had a tendency to try to make everything itself, Muellner says. “We spent a year weaning them off that. There were people in Irvine, [Calif.,] making actuators and Parker Hannifin is 6 mi. away.” Boeing has left most of the Frontier team in place. The aircraft are built and ground-tested in Irvine, running at full power on an indoor test stand, and flight-tested in Victorville, Calif. Vital and unique components are still custom-made, including the light (52-lb.) but rigid rotor blades. (On a recent tour at Victorville, an Army officer demonstrated the blade stiffness by doing a chin-up on the rotor. The blade barely deflected, but he was discreetly asked not to do it again.) The key to the A160T’s high perfor- Boeing expects to demonstrate a maximum range of 2,250 naut. mi. mance and low noise is the patented and a 20-hr. endurance under optiOptimum Speed Rotor concept. Other mum conditions—low forward speed helicopters operate in a small rotor- and 15,000 ft. The basic mission paspeed zone because of vibration lim- rameters are 12-hr. endurance, 500 its, but the rotor speed is higher than naut. mi. from station, with a 300necessary in many flight modes—par- lb. payload. ticularly low-speed forward flight— One advantage of the helicopter, creating extra drag. The OSR avoids Boeing notes, is in an armed reconthis with specially designed sections naissance mission. If a Predator at and a rigid blade system, with the cruising altitude detects a target and blades moving only in pitch: there the operator needs to descend and are no flapping or drag hinges. attack, the descent path has to be cleared of other traffic. It is easier and faster with the A160T, which descends quickly and almost vertically. Muellner notes that Socom experimented with Boeing’s own unmanned A/MH6X Little Bird as a cargo carrier, but the A160T has longer range a n d i s q u i e t e r. The streamlined ventral pod has a A clean, lightweight fuselage structure contrib- rear ramp and can utes to the A160T’s high performance. deploy a Talon unmanned ground The switch to a turbine, less toler- vehicle, raising the possibility of an ant of speed changes than a recipro- unmanned search-and-rescue operacating engine, has meant a change to tion, with the vehicle pulling an una two-speed transmission, developed conscious rescuee into the pod. Boeby Boeing’s rotorcraft technology ing business development director center in Philadelphia. Speed can be Grady Eakin describes the pod as “a adjusted over a 2:1 range by locking way to move high-value things from and releasing elements of a sun-and- locations where people are,” which planet gear system, using electrically is excellently vague. actuated carbon-carbon clutches. For The A160T is the primary platform early flights, the gear system will be for two Darpa sensor programs. It locked in place in either speed range, is the only UAV that readily carries but the transmission is designed for Syracuse Research Corp.’s Forester in-flight changes. foliage-penetrating radar, which has The A160T gains in performance a large antenna because it operates from a high fuel fraction. Empty in UHF. A surrogate antenna is due weight is 2,500 lb. and the helicop- to fly on the A160T this year, folter carries 2,600 lb. of fuel and a lowed in early 2008 by a functional 1,000-lb.-plus payload. Stub wings radar. The A160T is also the intended can be slotted into attach points on application for the agency’s Affordthe side of the body and carry four able Adaptive Conformal ESA Radar Hellfire missiles on each side. The (AACER), a Ka-band active electronimaximum takeoff weight is 6,500 lb. cally scanned array (AESA) under deAt high gross weights, the A160T is velopment by Raytheon and intenddesigned to perform a rolling takeoff ed to combine radar and high-rate communications functions. I on wheeled landing gear. www.aviationweek.com/dti 14 DEFENSE TECHNOLOGY INTERNATIONAL SEPTEMBER 2007 BOEING http://www.aviationweek.com/dti
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