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Aviation History
2002
2002 - 1684.PDF
TECHNOLOGY RADIO SPECTRUM CARROLL MCCORMICK / MONTREAL US group slams ultra-wideband devices approval The US Federal Communications Commission (FCC) has failed in its responsibility to provide a reasoned basis for its actions, to make ratio nal connections between the facts and its decision, or to make deci sions consistent with its Part 15 rules governing radio frequency devices, according to a US group. The allegations are made in a draft petition for reconsideration prepared for the Aviation Tele communications Coalition (ATC), formed to fight the unlicensed use of ultra-wideband (UWB) devices. The final version of this critique of the FCC's First Report and Order (R&O), which approves the use of certain classes of UWB devices, is expected to go to the FCC by 17 June. In February, the FCC autho rised the use of UWB devices above A Swedish/US team will this week test an automatic air-to-air collision avoidance system (AutoACAS) in simulators at Saab's factory in Linkoping. AutoACAS has been designed to prevent collisions during training and is an enabling technology for autonomous unmanned air vehicle (UAV) operations. The $12 million programme is funded jointly by Swedish defence materiel administration FMV and the US Air Force Research Lab oratory. Boeing, Lockheed Martin and Saab are participants. Ragnar Rosengren, Saab project manager, says the week-long trial - with Swedish and US pilots - will be run in two of Saab's JAS39 Gripen simulators and on two PC- based simulators. Flight tests are planned on USAF Lockheed Martin F-16s starting June/July next year. The tests follow an initial phase, which ended last year, during which the three companies sepa- 3.1GHz and imposed technical lim its below 3.1 GHZ, despite opposi tion from airlines and general avia tion operators Flight International, 26 February-4 March). Devices using UWB technology will broadcast weak signals over vast swathes of the aeronautical spectrum. Opponents fear this will interfere with their licensed sys tems and render unsafe aeronauti cal systems such as those using the global positioning system. The draft argues that the R&O did not establish limits that will prevent interference. It adds that the FCC conclusion that interfer ence can be mitigated by the users of authorised systems is contrary to the Part 15 requirement that inter fering operators immediately stop their interfering. rately developed AutoACAS pro posals. AutoACAS builds on a ter rain-avoidance system - the ground collision avoidance system - devel oped by the same team, but without Boeing, between 1997 and 1999. Saab's proposal was selected for further development. AutoACAS works by reserving areas to where the aircraft automatically flies, if a collision is imminent, using a 5,? manoeuvre. Each safe area is a cone of space, which widens the further from the fighter it is. When two cones inter sect, the escape manoeuvre is trig gered, the control is removed from the pilot and AutoACAS com mands the escape manoeuvre. Each fighter has three possible escape manoeuvres, one that repre sents the current escape path and two that are efforts to reserve areas for the next escape zone. System refresh rate is 10Hz. A special mode allows two aircraft to join for for mation flying, says Rosengren. The draft disputes the FCC accu sation that UWB opponents pre sented overly conservative and worst-case conditions where inter ference could occur - for example, between UWB and digital audio radio services equipment. A conser vative stance is fully justified and is the only one that can protect authorised systems, says the draft. "Nothing in the record or com mon sense supports an assumption that UWB devices will be kept away from the receivers they are more likely to interfere with," it adds. The R&O encompasses a wide variety of devices without regard to their particular interference charac teristics, according to the draft. Moreover, it argues, the FCC has failed to define successfully terms that will prevent the proliferation By linking the aircraft with a datalink, the system - which is software-based and does not req uire hardware changes - ensures each fighter has reserved a unique sanctuary. Risk is further reduced as the AutoACAS turns the fighters away from each other during a manoeuvre. Saab has simulation- of outdoor UWB communications infrastructure, a key UWB contain ment issue. The draft says that several R&O technical findings and decisions are wrong. For example, the R&O reasons that because Part 15 devices are already operating in the 2,400-2,450MHz band, UWB devices are likely to have no signif icant impact. The draft claims consistent evi dence exists that UWB devices impose an interference threat. Finally, it argues that the six to 12- month FCC timetable for review ing the limits set out in the R&O is not based on any facts, concluding that the only reason for this timetable is to allow the FCC to promote the deployment of UWB devices. tested the system with four aircraft. Rosengren says there are plans to test an "out of network" system, without datalinks, relying on other sensors. Changes for UAVs would require the vehicle to manoeuvre before a manned aircraft has to alter course, and have a less aggres sive escape manoeuvre. AutoACAS has a special mode to allow formation flying COLLISION AVOIDANCE STEWART PENNEY / LINKOPING Automatic avoidance system ready for simulator testing on Gripens Simulation and Lockheed Martin F-16 flight trials next year could pave way for autonom ous UAV operations 26 4-10 JUNE 2002 FLIGHT INTERNATIONAL www.flightinternational.com
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