FAA PRELIMINARY TESTS POINT TO UWB INTERFERENCE FOR AIRCRAFT

FCC was expected to have adopted on circulation by today (Thurs.) order and further notice addressing 14 pending petitions for reconsideration on UWB rules adopted in Feb. 2002. Office of Engineering & Technology Chief Edmond Thomas said last week that agenda item was “mainly cleanup” and that short-term changes in rules would be relatively “anticlimactic” (CD Feb 7 p3). Commission’s lab has planned to spend this year testing real-world UWB devices and their interactions with incumbent services before agency makes changes in rules. While FCC agenda meeting was postponed to Feb. 20 to take up UNE proceeding, OET still planned to go ahead with demonstrations of UWB technology today as scheduled in conjunction with original meeting (CD Feb 12 p1).

FAA last fall began testing UWB devices in effort to make initial assessment by year-end on potential impact of technology on avionics systems (CD Nov 18 p5). FAA and NASA had been among federal agencies particularly concerned about potential impact of UWB on safety-of-life systems. FAA had planned to test UWB prototype device and GPR unit at agency’s Technical Center in Atlantic City, but ultimately decided to evaluate just GPR, Sakai said in interview. FAA tests covered baseline measurements of kind and level of emissions from GPR unit, as well as operational tests, he said. Latter tests focused on whether commercially available GPR device, whose maker FAA hasn’t disclosed, caused interference to communications system of helicopter. Aside from airborne tests, FAA assessed impact of GPR unit on ground communications equipment used by air traffic controllers, Sakai said.

Final FAA test report is expected to be complete by May 30 and submitted to federal agencies such as NTIA, Sakai said. Preliminary tests will be followed up by repeat testing to fine-tune results, although he said he expected to see similar findings. Follow-up testing will provide more details on how extensive that interference is, he said.

“We are confident that the [FCC’s] first report and order adopted in February 2002 includes standards that provide adequate protection for existing and planned radio services, particularly safety services,” FCC spokeswoman said. “The Department of Transportation’s test data and report have not been shared with the FCC so it is not clear what devices were tested under what conditions and whether the devices complied with the FCC rules.” Spokeswoman said additional data were “always welcome” and “will be considered in the course of FCC policy deliberations once submitted into the record.”

FAA preliminary test results are “completely inconsistent with everything we understand about the performance of these devices,” said Washington attorney Mitchell Lazarus, who has represented GPR companies in UWB proceeding: “We'd welcome the chance to examine the specifics of the experimental set-up and the raw test results so that we can respond specifically and in detail. GPR emissions are required to be much lower than those from an ordinary consumer digital device like a laptop or a Palm Pilot.” Some pending petitions for reconsideration involve GPR operation. Last year, OET granted waiver of UWB rules to eligible GPR devices, allowing certain users to operate under Part 15 as long as they registered their devices and there was no showing of harmful interference to authorized services. GPR users had argued that rules, as originally adopted, would block needed applications and were more restrictive than needed.

As for operational tests on communications systems, FAA’s Sakai said 100 ft. was minimum distance between helicopter and GPR. He said severe interference was found: “We asked how far up we can go until we don’t have any more problems. The pilot changed the altitude and he went up all the way to 270 feet and there was also interference recorded.” Above that, interference wasn’t found. Above 275 ft., receivers have squelch setting that eliminates noise and aids in accurate scanning. That means signal has to be higher than receiver’s squelched setting to cause interference. “Above 270 feet, the [ground-penetrating] radar didn’t break the squelch,” Sakai said. Sometimes that setting is broken because someone else is talking to pilots, he said. Under that scenario, receiver is “wide open” and can hear other signals, he said. FAA testers asked pilot to override setting manually so receiver could listen to any signal. In that case, interference was found up to 600 ft. he said.

For tests on pilot navigation tools, at 100 ft. no “significant interference” was found on gear such as instrument landing system and VHF omnidirectional range (VOR), Sakai said. “Interfering sound” from GPR was detected on VOR receivers at 100 ft., he said: “It’s noticeable. If the sound is loud enough, it might interfere with operations.” That could cause problems in cases such as pilot reception of station identification information, he said. FAA tests involved ground equipment used by air traffic controllers. Systems detected “loud noise,” he said: “Our ground communications were severely affected by the ground-penetrating radar. It’s loud enough that it would mask the actual communications.”

GPR unit was configured in real-world application of looking toward ground, Sakai said. NASA last fall released final report on tests in Victorville, Cal., that evaluated potential UWB interference to aircraft radios on United Airlines and Eagles Wings planes. Those tests had shown potential for handheld UWB transmitters to cause cockpit failure indications for air traffic radio beacon control systems and failure of instrument landing system localizer. That report recommended further study of potential for UWB devices to affect avionics systems.

Additional, separate tests are also under way for FAA by Rockwell Collins at Cedar Rapids, Ia., Sakai said. They are “more precise, more academic type of tests” while those conducted in Atlantic City were more operational testing, he said. Rockwell Collins tests are expected to be wrapped up by June, he said.

Several sources said FAA was among govt. users of GPR- based technology, which has applications for facilities such as providing images of underground cable. One concern raised by aviation interests in last several years has been interference incident in 2001 at JFK International Airport in N.Y. in which GPR unit appeared to cause interference with air traffic control system. Dept. of Transportation officials last fall said assessment wasn’t finalized on possible linkage between GPR and interference incident (CD Nov 21 p6). That incident involved demonstration of GPR, Sakai said. “The people who were doing the demonstration immediately turned off the ground-penetrating radar. We did not allow any additional demonstrations,” he said.