ADS-B transponder problems on some aircraft stem from a bad update to a large class of aviation receivers, according to a blog on the Resilient Navigation and Timing Foundation website. The Air Traffic Control System Command Center issued a blanket waiver on June 9 for all flights having GPS/ADS-B issues with their transponders.
According to various sources, the disruption briefly grounded entire fleets of regional jets. The resulting delays and cancellations rippled through the system.
On June 9, the FAA published a map purporting to show an area of GPS signal degradation in the United States. However, the disruption appears to affect only certain Collins Aerospace (formerly Rockwell Collins) GPS receivers, according to AIN Online.
Collins Aerospace confirmed to AIN, “We identified a technical issue with our recently released GPS product(s) impacting availability, and have since determined the root cause and the resolution. We are engaging with our customers to ensure continued safe operational capability.”
The affected GPS receivers are GPS-4000S part number 822-2189-100 and GLU-2100 part number 822-2532-100. It appears that all aircraft worldwide these receives are not able to locate satellite position signals.
“The absence of reports of problems from other modes of transportation and other industries certainly seems to justify refocusing from GPS signals to receivers as the root cause….” said the RNTF blog. “This is a good reminder for all that great signals in space are just one part of a ‘gold standard’ system. We also need unobstructed spectrum, great receiving equipment, and more than one source of great signals.”