CARROLL McCORMICK / MONTREAL
United Airlines says UWB devices led to failure of major systems, despite FCC approval
Preliminary tests of ultra wideband (UWB) transmissions have led to failures in aircraft avionics, including the traffic alert and collision avoidance system (TCAS), instrument landing system (ILS) localiser, and glideslope (GS), United Airlines has revealed.
The results support airline and general aviation operators' claims that UWB devices, approved this year by the US Federal Communications Commission (FCC), pose a danger to aircraft systems.
Radio communications and VOR navigation beacons were not affected during the tests, which were conducted by NASA's Langley Research Center and Victorville, California-based Eagle Wings on Boeing 737-200s and 747-400s.
"At intentional emission levels set by the FCC we are observing critical flight systems anomalies from a single UWB device," says James Miller, United's flight operations technology department programme manager, who represents the US aviation industry on UWB issues.
Researchers operated a UWB chip at varying distances from avionics system antennas outside the aircraft and in several interior locations. The chip transmitted at the maximum power level set by the FCC. The communication and navigation systems broadcast at the lowest levels permitted by the International Civil Aviation Organisation.
When operating the chip outside the aircraft, NASA says, the TCAS fail light came on, its display indicator turned off and the targets disappeared off the screen. At lower UWB strength (inside the aircraft), says NASA, "the warning light did not come on, but the targets disappeared off the screen. It spoofed the system without any direct warning to the pilot."
The UWB source also caused erratic motion and retraction of the GS bar and pointer, and extension of the GS failure flag while transmitting outside the aircraft. These effects were not observed while transmitting inside the passenger cabin. The source also caused uncommanded motion and blanking of the ILS localiser course deviation indicator bar on the horizontal situation display.
UWB devices will broadcast weak signals over vast swathes of the aeronautical spectrum. Miller insists that the new FCC regulation "allows unlicensed consumer devices to intentionally radiate into [safety-critical aeronautical] bands under the guise that UWB is not powerful enough to interfere. Any pilot will tell you that injecting any level of interference into the cockpit is an unacceptable consequence of FCC rule making."
Source: Flight International
