Transponder/GPS issues today

[swh]

Anyone know of a work around for the issues Rockwell Collins 737/757 transponders and GPS have started to exhibit today ?

What is the root cause ?

[DaveReidUK]

Reportedly also affects all CRJs and CSeries/A220s, which also carry Rockwell Collins kit.

[cappt]

I got the email but on VAC for a few days and no details, what's the issue?

[Halfnut]

Up on our board.....so it's a "source from another source" -

This is from another source:



From sources posted on public forum:
Just had a call with the Command Center: Below are notes from the Call.
United, Delta, Air Canada all report that their regional partners who fly CRJ type aircraft are also experiencing widespread issues. Currently we have not heard of any mainline aircraft being affected with the exception of United's 737-900.
WAAS and GPS appear to be up and running without issue.
Fort Bliss/ZFW/ZAB all have NOTAMs advising of GPS jamming today and the FAA has requested a stoppage of any jamming in the interim. The FAA has also contacted NORAD to see if they are engaged in any activity.
Different email...
Currently this is causing widespread delays across Mesa, Skywest and PSA and appears to be affecting CRJ aircraft only.
Republic, Piedmont, Envoy and Compass have not reported any issues.
More to follow.

[KelvinD]

I may be getting old and the brain getting a bot rusty but, I am sure I read an article about this issue within the last couple of months. I don't remember the details but I am sure it mentioned Rockwell taking pro-active measures and it may have had something to do dates, along the lines of the Y2K 'issue'.

[PPRuNeUser0130]

I may be getting old and the brain getting a bot rusty but, I am sure I read an article about this issue within the last couple of months. I don't remember the details but I am sure it mentioned Rockwell taking pro-active measures and it may have had something to do dates, along the lines of the Y2K 'issue'.

The GPS date rollover was April 6, so I doubt that has anything to do with it

[swh]

FAA has issued a blanket waiver for all aircraft experiencing GPS\ADS issues today

https://www.fly.faa.gov/adv/adv_otherdis.jsp?advn=29&adv_date=06092019&facId=DCC&title=GUIDANCE+FOR+ADSB&titleDate=06/09/19ATCSCC AdvisoryATCSCC ADVZY 029 DCC 06/09/2019 GUIDANCE FOR ADSBMESSAGE:
EVENT TIME: 09/1230 - 10/0400Z
COMMAND CENTER HAS APPROVED BLANKET WAIVER FOR ALL FLIGHTS CURRENTLY
HAVING GPS/ADSB ISSUES WITH THEIR TRANSPONDERS. INDIVIDUAL WAIVER
REQUESTS TO THE COMMAND CENTER ARE NO LONGER NECESSARY. HOWEVER,
AFFECTED FLIGHTS SHOULD FILE FLIGHT PLANS VIA THE FOLLOWING
PARAMETERS:

YOU MUST FILE FL280 AND BELOW. YOU MUST FILE RNAV ROUTING AND IF YOU
ARE UNABLE,YOU MUST FILE VIA TRADITIONAL AIRWAYS AND/OR NAVAIDS.
THIS BLANKET APPROVAL IS VALID ONLY UNTIL JUNE 10, 0400Z. EFFECTIVE TIME:
091231 - 100430 (tel:091231 - 100430)SIGNATURE:
19/06/09 12:31

[Maninthebar]

FAA has issued a blanket waiver for all aircraft experiencing GPS\ADS issues today

https://www.fly.faa.gov/adv/adv_otherdis.jsp?advn=29&adv_date=06092019&facId=DCC&title=GUIDANCE+FOR+ADSB&titleDate=06/09/19ATCSCC AdvisoryATCSCC ADVZY 029 DCC 06/09/2019 GUIDANCE FOR ADSBMESSAGE:
EVENT TIME: 09/1230 - 10/0400Z
COMMAND CENTER HAS APPROVED BLANKET WAIVER FOR ALL FLIGHTS CURRENTLY
HAVING GPS/ADSB ISSUES WITH THEIR TRANSPONDERS. INDIVIDUAL WAIVER
REQUESTS TO THE COMMAND CENTER ARE NO LONGER NECESSARY. HOWEVER,
AFFECTED FLIGHTS SHOULD FILE FLIGHT PLANS VIA THE FOLLOWING
PARAMETERS:

YOU MUST FILE FL280 AND BELOW. YOU MUST FILE RNAV ROUTING AND IF YOU
ARE UNABLE,YOU MUST FILE VIA TRADITIONAL AIRWAYS AND/OR NAVAIDS.
THIS BLANKET APPROVAL IS VALID ONLY UNTIL JUNE 10, 0400Z. EFFECTIVE TIME:
091231 - 100430 (tel:091231 - 100430)SIGNATURE:
19/06/09 12:31


That approval has expired, no?

[Noeyedear]

Affecting Bombardier aircraft as well. According to Bombardier its to do with the June 9th GPS Satellite update.

They've suggested a work around involving powering up the aircraft with GNSS Breakers pulled, then resetting the breakers once everything else is running.........

No idea if that's gonna work.

[Euclideanplane]

A little more background on hackaday.com/2019/06/09/gps-and-ads-b-problems-cause-cancelled-flights/ of all places:


Something strange has been going on in the friendly skies over the last day or so. Flights are being canceled. Aircraft are grounded. Passengers are understandably upset. The core of the issue is GPS and ADS-B systems. The ADS-B system depends on GPS data to function properly, but over this weekend a problem with the quality of the GPS data has disrupted normal ADS-B features on some planes, leading to the cancellations.

WHAT IS ADS-B AND WHY IS IT HAVING TROUBLE?
Automatic Dependent Surveillance-Broadcast (ADS-B) is a communication system used in aircraft worldwide. Planes transmit location, speed, flight number, and other information on 1090 MHz. This data is picked up by ground stations and eventually displayed on air traffic controller screens. Aircraft also receive this data from each other as part of the Traffic Collision Avoidance System (TCAS).

ADS-B isn’t a complex or encrypted signal. In fact, anyone with a cheap RTL-SDR can receive the signal. Aviation buffs know how cool it is to see a map of all the aircraft flying above your house. Plenty of hackers have worked on these systems, and we’ve covered that here on Hackaday. In the USA, the FAA will effectively require all aircraft to carry ADS-B transponders by January 1st, 2020. So as you can imagine, most aircraft already have the systems installed.

The ADS-B system in a plane needs to get position data before it can transmit. These days, that data comes from a global satellite navigation system. In the USA, that means GPS. The GPS system is currently having some problems though. This is where Receiver autonomous integrity monitoring (RAIM) comes in. Safety-critical GPS systems (those in planes and ships) cross-check their current position. If GPS is sending degraded or incorrect data, it is sent to the FAA who displays it on their website. The non-precision approach current outage map is showing degraded service all over the US Eastern seaboard, as well as the North. The cause of this signal degradation is currently unknown.

WHAT HARDWARE IS AFFECTED?
GPS isn’t down though — you can walk outside with your cell phone to verify that. However, it is degraded. How a plane’s GPS system reacts to that depends on the software built into the GPS receiver. If the system fails, the pilots will have to rely on older systems like VOR to navigate. But ADS-B will have even more problems. An aircraft ADS-B system needs position data to operate. If you can’t transmit your position information, air traffic controllers need to rely on old fashioned radar to determine position. All of this adds up to a safety of flight problem, which means grounding the aircraft.

Digging through canceled flight lists, one can glean which aircraft are having issues. From the early reports, it seems like Bombardier CRJ 700 and 900 have problems. Folks on Airliners.net are speculating that any aircraft with Rockwell Collins flight management systems are having problems.

This is not a small issue, there are hundreds or thousands of canceled flights. The FAA set up a teleconference to access the issue. Since then, the FAA has issued a blanket waiver to all affected flights. They can fly, but only up to 28,000 feet.

This is a developing story, and we’ll be keeping an eye on it. Seeing how the industry handles major problems is always educational, and there will be much to learn in the coming days.

[Euclideanplane]

And a comment from a Scott H. on the same site:

The airline I work for is having this issue. The story we’re getting is that at approximately 3:00z on 6/9/19, the WAAS system on all of the GPS satellites received a software upgrade and that the software upload was somehow corrupted. This means that aircraft equipped with the WAAS MMR’s (Multi mode receivers) manufactured by Rockwell Collins are unable to resolve the WAAS signal from the satellites, thus causing MMR and GPS failure messages in the aircraft. The aircraft equipped with the pre WAAS MMR’s are not affected. Our airline is working with Rockwell Collins, the aircraft manufacturer and the FAA to receive permission to return our aircraft back to the pre WAAS configuration until the WAAS systems on the satellite constellation are operating normally again.

[Vilters]

Perhaps, I am old school, perhaps my airplane is old school, but in my younger years we had something called a compass.

And you know what?
There even was a guy that crossed the ocean with a "compass". => Lindberg in a canvas airframe without heater or aircon and I don't think he had a stewardess to keep him company either.

See where technology has brought us?

To fly? You need a pilot and an airplane. Every line of software is a line too many.

[denachtenmai]

There even was a guy that crossed the ocean with a "compass". => Lindberg

There was even two "guys" who did it before, Alcock and Brown.:)

[Euclideanplane]

There even was a guy that crossed the ocean with a "compass". => Lindberg in a canvas airframe without heater or aircon .

According to Wikipedia "Lindbergh navigated only by dead reckoning (he was not proficient at navigating by the sun and stars and he rejected radio navigation gear as heavy and unreliable)"
and he didn't know where the airfield was once he arrived at Paris.

So are you really sure about this "navigation by compass only" anecdote?

[MurphyWasRight]

According to Wikipedia "Lindbergh navigated only by dead reckoning (he was not proficient at navigating by the sun and stars and he rejected radio navigation gear as heavy and unreliable)"
and he didn't know where the airfield was once he arrived at Paris.

So are you really sure about this "navigation by compass only" anecdote?
That reads exactly like dead reckoning using a compass to me.

Direction (compass) and speed X elapsed time plotted tells you (about) where you should be.

Having to find the airport at the end would be totally expected.
The compass was also usefull to point in correct direction :)

[cappt]

Arrggghhhh.."Software update", should of known.

[Euclideanplane]

That reads exactly like dead reckoning using a compass to me.
Indeed. I may have misread Vilters, who didn't actually say "only a compass". For dead reckoning you compute the wind triangle using a compass, additionally you need information about wind speed and true airspeed. Which the compass obviously does not provide.
Anyway, GPS provides heading information anyway, in addition to whatever else information you need, so I am not sure I see the point. You use whatever instruments available to tell you where your are and where you are headed.

[Grummaniser]

Arghhhh! One of my pet hates -it's DED reckoning, 'Ded' being short for 'Deduced'
Pedantly yours...

[Maninthebar]

Arghhhh! One of my pet hates -it's DED reckoning, 'Ded' being short for 'Deduced'
Pedantly yours...

That source of all error, Wikipedia, says "The term "dead reckoning" was not originally used to abbreviate "deduced reckoning," nor is it a misspelling of the term "ded reckoning." The use of "ded" or "deduced reckoning" appeared much later in history, no earlier than 1931; in contrast to "dead reckoning" appearing as early as 1613 in the Oxford English Dictionary. The original intention of "dead" in the term is not clear however. Whether it is used to convey "absolute" as in "dead ahead," reckoning using other objects that are "dead in the water," or using reckoning properly "you’re dead if you don’t reckon right," is not known"

One might also instantiate "dead on", "dead heat", "dead drunk" in each of which the term 'dead' qualifies as 'absolutely'

[Surlybonds]

That source of all error, Wikipedia, says "The term "dead reckoning" was not originally used to abbreviate "deduced reckoning," nor is it a misspelling of the term "ded reckoning." The use of "ded" or "deduced reckoning" appeared much later in history, no earlier than 1931; in contrast to "dead reckoning" appearing as early as 1613 in the Oxford English Dictionary. The original intention of "dead" in the term is not clear however. Whether it is used to convey "absolute" as in "dead ahead," reckoning using other objects that are "dead in the water," or using reckoning properly "you’re dead if you don’t reckon right," is not known"

One might also instantiate "dead on", "dead heat", "dead drunk" in each of which the term 'dead' qualifies as 'absolutely'

Dead right...

:)

[MurphyWasRight]

That source of all error, Wikipedia, says "The term "dead reckoning" was not originally used to abbreviate "deduced reckoning," nor is it a misspelling of the term "ded reckoning." The use of "ded" or "deduced reckoning" appeared much later in history, no earlier than 1931; in contrast to "dead reckoning" appearing as early as 1613 in the Oxford English Dictionary. The original intention of "dead" in the term is not clear however. Whether it is used to convey "absolute" as in "dead ahead," reckoning using other objects that are "dead in the water," or using reckoning properly "you’re dead if you don’t reckon right," is not known"

One might also instantiate "dead on", "dead heat", "dead drunk" in each of which the term 'dead' qualifies as 'absolutely'

That said if I was responsible for navigation the most common meaning of dead would most likely also apply.

[GordonR_Cape]

Indeed. I may have misread Vilters, who didn't actually say "only a compass". For dead reckoning you compute the wind triangle using a compass, additionally you need information about wind speed and true airspeed. Which the compass obviously does not provide.
Anyway, GPS provides heading information anyway, in addition to whatever else information you need, so I am not sure I see the point. You use whatever instruments available to tell you where your are and where you are headed.

Pedantic mode: Pure GPS does not provide direction, only position. However if you move in a randomly oriented straight line, GPS will tell you which direction you have moved in, and then you can then re-orient yourself to go in the direction you really wanted. Of course most devices (such as modern phones) have a compass and accelerometer.

[Maninthebar]

Pedantic mode: Pure GPS does not provide direction, only position. However if you move in a randomly oriented straight line, GPS will tell you which direction you have moved in, and then you can then re-orient yourself to go in the direction you really wanted. Of course most devices (such as modern phones) have a compass and accelerometer.

Could you derive track from heading, speed and acceleration? I think not. Well I couldn't

[lenrand]

They say they still don't know the root cause and have no projected fix time/date.

Anyone know of a work around for the issues Rockwell Collins 737/757 transponders and GPS have started to exhibit today ?

What is the root cause ?

[Eboy]

They say they still don't know the root cause and have no projected fix time/date.

In this article, Collins is quoted as saying it has determined the root cause and resolution:

https://www.ainonline.com/aviation-news/business-aviation/2019-06-10/collins-gps-receivers-suffer-reception-outage

[Gauges and Dials]

Could you derive track from heading, speed and acceleration? I think not. Well I couldn't

This is a case in which the difference between theory and practice is greater in practice than it is in theory.

GPS gives you a series of positions. Which means, as theory pedants like me will point out, GPS cannot tell you what your airplane (or ship, or cell phone) is doing in terms of course or velocity right now, all it can tell you is what your course and velocity were a little while ago.

But now factor in physics. If your course and velocity were to be a whole lot different than what they were one second ago, your neck would have snapped from the acceleration. Since your head didn't snap off your shoulders, we can safely infer that your instantaneous velocity vector right now is not a whole lot different from what it was a little while ago.

Factor in reasonable values for a little while and a whole lot and you get pretty tight bounds around what your instantaneous course and velocity are.....

[Smythe]

GPS gives you a series of positions. Which means, as theory pedants like me will point out, GPS cannot tell you what your airplane (or ship, or cell phone) is doing in terms of course or velocity right now, all it can tell you is what your course and velocity were a little while ago.


GPS tells you were you were.
The kalman filter and associated algorithms predict where you are.

[Slow and curious]

If you are everywhere, there is no need to go anywhere.:p

[Dont Hang Up]

...Which means, as theory pedants like me will point out, GPS cannot tell you what your airplane (or ship, or cell phone) is doing in terms of course or velocity right now, all it can tell you is what your course and velocity were a little while ago.

But now factor in physics. If your course and velocity were to be a whole lot different than what they were one second ago, your neck would have snapped from the acceleration. Since your head didn't snap off your shoulders, we can safely infer that your instantaneous velocity vector right now is not a whole lot different from what it was a little while ago......

As we are being pedantic I suppose we should be clear that "course and velocity" is tautology. There is "course and speed" or there is "velocity".

[futurama]

GPS gives you a series of positions. Which means, as theory pedants like me will point out, GPS cannot tell you what your airplane (or ship, or cell phone) is doing in terms of course or velocity right now, all it can tell you is what your course and velocity were a little while ago.
This is wrong, anyway, in theory and in practice.

GPS does calculate instantaneous velocity -- the velocity right now -- not from a series of positions but by using the doppler shift from each satellite.

In fact with just a single reading (from at least four satellites) a GPS receiver can calculate instantaneous position, velocity and time (PVT).

With multiple readings, very precise velocity estimates can be obtained by noting how the carrier phase changes between each reading. This is known as Time-Differenced Carrier Phase (TDCP).

All subject to the usual GPS errors (hence Kalman filters).

[fdr]

After reading the GPS issue, was interested in what was to be seen on flights takin on the 9th. Nothing of interest appeared to occur which was nice. However, having completed a flight on the 9th, on departure the next day, the radars would not come up. The flight was completed to reposition taking some care to avoid the lumpy bits. Initial checking indicated that the radars were dead (or DED, as applicable). Questioning that, we played with the radar for a while, and found that if we sequenced the systems power up of the radar and GPS, radar worked fine. As the solid state radars are not known for regenerating the magic smoke after auto release, a discussion with the system manufacturer ensued. The OEM was surprised by the behaviour, agreed that solid state units don't exhibit Schrodinger's cat's behaviour. On review, the OEM had a prior history of some 10 failures of this type in 2015 when the system was relatively new, and had introduced a software update to fix the problem. 4 years later, after an overnight, the problem is manifested again. What happened on the 9th?

[MarkerInbound]

Perhaps, I am old school, perhaps my airplane is old school, but in my younger years we had something called a compass.

And you know what?
There even was a guy that crossed the ocean with a "compass". => Lindberg in a canvas airframe without heater or aircon and I don't think he had a stewardess to keep him company either.

See where technology has brought us?

To fly? You need a pilot and an airplane. Every line of software is a line too many.


You'll note that Lindberg (and Alcock and Brown) quite literally had the sky to themselves. So technology has brought us the ability to to launch a couple thousand NAT crossings a day.

[bill fly]

After reading the GPS issue, was interested in what was to be seen on flights takin on the 9th. Nothing of interest appeared to occur which was nice. However, having completed a flight on the 9th, on departure the next day, the radars would not come up. The flight was completed to reposition taking some care to avoid the lumpy bits. Initial checking indicated that the radars were dead (or DED, as applicable). Questioning that, we played with the radar for a while, and found that if we sequenced the systems power up of the radar and GPS, radar worked fine. As the solid state radars are not known for regenerating the magic smoke after auto release, a discussion with the system manufacturer ensued. The OEM was surprised by the behaviour, agreed that solid state units don't exhibit Schrodinger's cat's behaviour. On review, the OEM had a prior history of some 10 failures of this type in 2015 when the system was relatively new, and had introduced a software update to fix the problem. 4 years later, after an overnight, the problem is manifested again. What happened on the 9th?

Huawei sends greetings...

[FairWeatherFlyer]

GPS does calculate instantaneous velocity -- the velocity right now -- not from a series of positions but by using the doppler shift from each satellite.

Are you saying that GPS can accurately calculate GS/VS/direction purely by observing the received, doppler-shifed-due-to-GPS-receiver-movement carrier frequencies from satellites? It would be interesting to read more about this if you have some reference material?

[FairWeatherFlyer]

The airline I work for is having this issue. The story we’re getting is that at approximately 3:00z on 6/9/19, the WAAS system on all of the GPS satellites received a software upgrade and that the software upload was somehow corrupted.

That sounds unlikely but possibly just because it's a slight misintepretation of events. It would be more likely that the software update was applied correctly but that some niche receivers either are not fully compliant to the standard or have obscure bugs in rarely exercised code which have been triggered by the new software version on the satellites. I say niche because there's likely to be testing on a decent spread of real receivers for this type of critical system.

A plausible explanation from recent Hackaday comments (leap seconds (https://www.nist.gov/pml/time-and-frequency-division/leap-seconds-faqs) often cause "fun"):

Josh says:June 11, 2019 at 7:13 am (https://hackaday.com/2019/06/09/gps-and-ads-b-problems-cause-cancelled-flights/#comment-6155776)This particular issue is directly related to certain GPS units from Collins Aerospace (formerly Rockwell Collins). A software design error resulted in the system misinterpreting GPS updates due to a “leap second” event. Collins has advised its customers to not power on the units until June 16, the next scheduled update by the US government to the GPS constellation.

[futurama]

Are you saying that GPS can accurately calculate GS/VS/direction purely by observing the received, doppler-shifed-due-to-GPS-receiver-movement carrier frequencies from satellites? It would be interesting to read more about this if you have some reference material?

"Stand-alone single-frequency GNSS receivers ... estimate velocity either by differencing two consecutive positions ... or by using Doppler measurements related to user-satellite motion. The former approach is the most simple to implement, but it has a meter per second-level of accuracy due to the dependence on pseudorange-based position accuracy. In contrast, Doppler frequency shifts of the received signal produced by user-satellite relative motion enables velocity accuracy of a few centimeters per second." -- GNSS Solutions (http://admin.insidegnss.com/auto/marapr15-SOLUTIONS.pdf)

"GPS and other global navigation satellite systems use the Doppler shift of the received carrier frequencies to determine the velocity of a moving receiver. Doppler-derived velocity is far more accurate than that obtained by simply differencing two position estimates." -- GPS World (https://www.gpsworld.com/gnss-systemalgorithms-methodsinnovation-doppler-aided-positioning-11601/)

"With respect to the receiver, of course, the satellite is always in motion, but the receiver may be in motion in another sense, in kinematic GPS. It may be on a moving platform, like a vehicle. The ability to determine instantaneous velocity of a moving vehicle has always been one of the primary applications of GPS and it is aided by the Doppler shifted frequency of a satellite signal. In other words, if the platform is moving, there is a relationship between the Doppler shift nominally from the satellite and the change based upon the movement of the vehicle on which the receiver finds itself." -- GPS and GNSS for Geospatial Professionals (https://www.e-education.psu.edu/geog862/node/1786)

[MurphyWasRight]

"Stand-alone single-frequency GNSS receivers ... estimate velocity either by differencing two consecutive positions ... or by using Doppler measurements related to user-satellite motion. The former approach is the most simple to implement, but it has a meter per second-level of accuracy due to the dependence on pseudorange-based position accuracy. In contrast, Doppler frequency shifts of the received signal produced by user-satellite relative motion enables velocity accuracy of a few centimeters per second." -- GNSS Solutions (http://admin.insidegnss.com/auto/marapr15-SOLUTIONS.pdf)

"GPS and other global navigation satellite systems use the Doppler shift of the received carrier frequencies to determine the velocity of a moving receiver. Doppler-derived velocity is far more accurate than that obtained by simply differencing two position estimates." -- GPS World (https://www.gpsworld.com/gnss-systemalgorithms-methodsinnovation-doppler-aided-positioning-11601/)

"With respect to the receiver, of course, the satellite is always in motion, but the receiver may be in motion in another sense, in kinematic GPS. It may be on a moving platform, like a vehicle. The ability to determine instantaneous velocity of a moving vehicle has always been one of the primary applications of GPS and it is aided by the Doppler shifted frequency of a satellite signal. In other words, if the platform is moving, there is a relationship between the Doppler shift nominally from the satellite and the change based upon the movement of the vehicle on which the receiver finds itself." -- GPS and GNSS for Geospatial Professionals (https://www.e-education.psu.edu/geog862/node/1786)
Thanks for the links, the last one is part of a comprehensive introduction to GPS (hit 'up' at bottom of page) that covers a lot of things that I have 'picked up here and there' cursory knowledge of, in a way that ties it all together. In other words there goes a few more hours learning things that I have no practical use for.:)

[GordonR_Cape]

Are you saying that GPS can accurately calculate GS/VS/direction purely by observing the received, doppler-shifed-due-to-GPS-receiver-movement carrier frequencies from satellites? It would be interesting to read more about this if you have some reference material?

It is theoretically possible to measure velocity very accurately from GPS signals, but this requires significant processing power, compared to a normal GPS position fix. See:
https://www.researchgate.net/profile/Kefei_Zhang/publication/238619351_On_the_relativistic_Doppler_Effects_and_high_accur acy_velocity_determination_using_GPS/links/0f3175358611da4c78000000.pdf
http://researchbank.rmit.edu.au/eserv/rmit:9492/Zhang.pdf
To date, with SA switched off and with the improvement of receiver technologies, velocities of a GPS user can be determined at an accuracy level of centimetres per second, which are several orders of magnitude higher than that of the positions. Moreover, the velocities can be measured at a relative high sampling rate, say from 10Hz to 100Hz

Whether your specific GPS receiver has this capability (outside of specialised surveys), is an entirely different question.

P.S. Thanks to @futurama for pointing this out earlier in the thread.