Date: 201902
Local time of day: 1801-2400
Location: LAX.Airport, CA
Light: Night
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground LAX
Aircraft component: GPS & Other Satellite Navigation
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Time Pressure; Troubleshooting; Human-Machine Interface
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Contributing factors: Airport; Procedure
Primary problem: Ambiguous

Narrative: During push-back we got the EICAS 'ASD-B NOT AVAIL'. During the time we were referencing the QRH; the EICAS cleared on its own. I remembered getting the same exact EICAS a long time ago when the US military was testing GPS jamming equipment in the southwest US. So; when we got the EICAS and looked at QRH; I checked our NAV sensors in the MCDU; and I saw blank space for both GPS 1 and 2; which told we weren't getting a GPS position. After GPS 1 & 2 got positions again; the EICAS cleared and we started to taxi. Shortly into our taxi to 25R; we got the EICAS again. Now I wanted to pull over and call Maintenance Control. For reference the first instance occurred when we were in the gate area in LAX and the second occurred just as we made the turn onto TWY B off of C4. LAX Ground had us taxi B-C3-C hold short of C4 while we troubleshot. While on the phone with the company I was advised that the issue could be due to GPS jamming testing by [company name] or one of the other aerospace companies nearby. Ops Control suggested I move from my current position. I evaluated the situation and decided that I would try to give that plan a shot before returning to the gate for Maintenance. I intended to ask LAX ground that we taxi to the approach end of 25R and give the plane a few minutes to assess the situation and see if changing position impacted the GPS performance. A couple of points I want to add are; while I contacted Ops and Maintenance Control while we were on C short of C4; our GPS signal was so intermittent we got many EICAS messages for ADS-B NOT AVAIL. During that time; we asked Ground if anyone else was having the issue; and multiple AC reported no issue; though no one was close to our position at the time. During this time; I also referenced our SID; the SUMMR1; which had a note for 'DME/DME/IRU or GPS required'. Even if we were able to get the EICAS to clear and get a stable GPS signal prior to departure I did not want to assume I'd have it for the departure; so I contacted Clearance Delivery (CD) and advised them of our GPS issues and they decided to amend our clearance to the VTU8 and gave us a modified routing to ZZZ. Getting the clearance changed with CD took a while; Ground moved us up C to short of C6; and we waited there for over 10 minutes while we sorted out our clearance and checked our route. During that entire period while we were short of C6 we did not have any issues with our GPS signal; nor did we get any EICAS messages. That gave me some confidence that the company was correct; that some third party was testing GPS jamming equipment; and that we were in its effective radius. Now that the GPS was stable; and we had a modified clearance from ATC accounting for a potentially inoperative GPS; we took off and continued with normal operations. For the remainder of the flight we did not once lose GPS signal and had positions on GPS 1 and 2 the whole time. It seems there's a very good chance that a company is testing GPS jamming equipment in the vicinity of LAX. If this is true; I am very frustrated that this is occurring. Given the increasing use and reliance of GPS for RNAV and RNP navigation; GPS jamming; at best; causes an issue like mine that ends up just wasting time and fuel. At worse; this could potentially impact navigation performance in a critical phase of flight. Personally; I hope this kind of activity is banned within a given radius next to airports. At the very least a NOTAM; for which there was not one; would have helped me correctly and quickly identify the issue.


Second narrative: When we started to push back; we got an EICAS message that said 'ASD-B NOT AVAIL'. As we opened the QRH and started reading through the procedure; the message went away on its own. We then checked the NAV sensors; which GPS 1 and 2 were blank; then as the EICAS message disappeared; the sensors came back. We then started to taxi; shortly after getting the message again (about C4). The Captain decided we needed to pull over and give Maintenance a call; so we contacted Ground and they told us B-C3-C hold short C4. Maintenance advised the CA that there could be some GPS jamming testing going on. So we tried to taxi towards the end of 25R to see if things would fix itself. We also asked Tower if any other planes were having any issues; they asked 3 others; who were not experiencing the same thing (though they were not near us). While we were stopped; we had the EICAS message come up again. The Captain (CA) decided to start looking at other departures that were not RNAV related; we ended up getting the VTU8 departure. While we grabbed clearance for our new departure; Ground moves us to C6; where we did not get the EICAS message again or issues with the sensors. After a while we decided the GPS was stable enough and we departed; having no further issues the entire flight.


Synopsis: Embraer 175 flight crew reported experiencing intermittent GPS signal reception while taxiing for takeoff at LAX.