But let’s still decommission all terrestrial navaids… - Bob Mann
> On May 25, 2025, at 07:30, Tom Ronell via Mifnet <mifnet@lists.mifnet.com> > wrote: > >  > > Situation > > This past week, a slew of Dual/Complete GPS Failures began to be reported by > airlines and AOs around the world. Typically, the fault is first annunciated > as an “ADS-B RPTG” Fault, followed by GPS 1/2 failure. This is unrelated to > spoofing or jamming. Many aircraft have been grounded as a result, mostly for > short duration pending a reset. > > > > Update – Sunday 25 May > > Many reports of dual GPS failures and associated system failures continue to > come in. The cause remains unknown. Aviation authorities and manufacturers > are investigating, but there is no clear answer yet. GPS spoofing/jamming is > very unlikely to be the cause, as this is happening in many regions where > none is present. > > Impact is apparently limited to Air Transport category aircraft (notably > mostly B737 and A320, but also A330 and others). No reports of any business > aviation aircraft being impacted have been received. > > > > Reports and Information Received > > The majority of reports are from aircraft with Honeywell IMMRs. However, > there are also some unverified reports that Collins units are also affected. > > - Most events have “ADS B 1 & 2 RPTG FAULT” as the first indication of GPS > issues. > > - As an example, one A320 report indicates (Bogota, Colombia), GPS failed on > the ground and only recovered in flight through FL160. Another A320 > experienced similar, with similar ECAM messages, also ILS 1 + 2 FAULT and > loss of GPS clock occurred. The integrity was restored without any action, > after two or three minutes. > > - Most aircraft affected seem to be A320 and B737. However, other types also > affected. An A330 report received from the Africa/ME region says that “ADS-B > out reporting dual failure, and then generated a series of warnings including > Pull up Terrain and Don’t Sink several times, subsequent to GPS 1 and GPS 2 > failure.” This operator advises that multiple similar events have occurred > from May 12 to May 24. > > - A series of RAIM-related reports received from some operators, though it’s > unclear if this is related to the same issue. For example, 4 B737’s out of a > US airport (Texas area) suffered GPS loss of signal on 21 May at around > 0500Z, and “appear to be related to several swaths of RAIM outages”. > > - An Airbus note (22 May) advises that: “In the reported cases, NAV ADS-B > RPTG 1(2) FAULT could be triggered on A/C equipped with IMMR due to repeated > auto-resets of IMMR. The auto-resets occur about once per minute, preventing > the receiver from maintaining stable operation. The root cause of these > auto-resets is under investigation.” Also: “At this stage, no workaround has > been identified. In some cases, MMR reset (several attempts could be > necessary) or moving the A/C may clear the faults and help to recover the > system.” > > - US operators: A minimum of 8 air carriers have reported issues with over > 150 aircraft affected by Dual GPS INOP. Reports from North America > (majority), Australia, and Europe so far. While a few listed other equipment > and may be separate issues, the overwhelming majority confirmed they were > Honeywell-equipped. > > - A Boeing note (24 May) says: “The majority of the reports received have > been applicable to 737NG/MAX model airplanes. Reported events have also > occurred on B767 and B777 aircraft. This issue is not limited to the parts or > system design of the 737; all Boeing airplane models could potentially be > impacted. Most reports are seen on aircraft equipped with Honeywell > Integrated Multimode Receiver (IMMR) units, P/N: 69002600-0101. Boeing is > investigating the GPS loss events for all MMR part numbers including the > Collins GLU-2100 and GLU-925 to determine if the root cause could be related > to the widespread GPS loss events being seen on the Honeywell IMMR P/N > 690002600-0101. Boeing is currently coordinating with Honeywell and Collins > to investigate these events to determine the root cause and possible > mitigating and final actions. Boeing is aware major solar storms inducing > solar flares could cause communication/navigation blackouts during the week > and continues to investigate this phenomenon for potential connections to the > root cause. Information provided by some reported cases indicates that the > GPS Receiver recovered GPS functionality within 10–30 seconds of a loss > event.” > > - A Honeywell note (24 May) says: “On May 21, 2025, Honeywell, Boeing and > Airbus began receiving reports of dual GPS receiver function in Air Transport > category aircraft. The nature of the failures is still under investigation. > It has not impacted all aircraft, but appears to be limited to those equipped > with Integrated Multi-Mode Receivers (IMMR) (Boeing: P/N: 69002600-0101, > Airbus P/N: 69002602-0201). Reports have been received that this is NOT > limited to Honeywell-integrated IMMRs and does affect other suppliers. > Symptoms include: No Clock, GPS Status is Blank, L/R GPS Failure messages. > These issues can occur either on the ground or in-air. Other GPS-Consuming > symptoms such as ADS-B, EGPWS are also likely to experience issues and > degraded modes due to the loss of GPS data. This is NOT a fault with those > symptoms and can be confirmed by reviewing the GPS Status/Monitoring data.” > > - Causes suggested so far include GPS Jamming/Spoofing (can be ruled out due > to locations of reports), Space Weather/Solar Flares (seems unlikely due to > the lack of impact on other GPS users and the trend towards specific aircraft > types and operations), and a software issue with specific receivers > (unverified). To date, no cause is clearly identified. > > > Request for More Information > > We would greatly appreciate: > > Any reports of GPS issues or failures (other than those related to spoofing > or jamming) > Any guidance received from your CAA, OEM/manufacturer, or operator > Any further information on the issue > -------------------------------------------------------------------------- > Revised: 20250507 > > You are receiving The Mifnet because you requested to join this list. > > The Mifnet is largely a labor of love, however the infrastructure isn't > exactly cost-free. 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