I've been GPS jammed. It went on for 18 minutes. Our actual navigation performance grew to a couple of miles (I forget the actual value now). This jamming was not part of an exercise.

Probably not jamming, at least not targeted at you. GPS jamming targeted at you would render it useless. GPS signals are very weak.

It might have been RF inteference, either authorized or unauthorized. Might also have been jamming targeted at something else nearby, depending on where you were when it happened. In the US they issue NOTAMs before they do that.

What he described sounds exactly like GPS jamming where the FMS starts using other means of discerning aircraft position and ANP rapidly rises.

The FMS should tell you if GPS is TU. But yes, loss of GPS would result in RNAV via other, less precise means (INS, DME/DME, etc)

On most Boeings it tells you UNABLE RNP and sometimes it says ATC FAIL. Also your moving map NAV source will change - usually to IRS.

We were definitely in a area to be jammed. It is an area of known jamming. The company has issues several NOTAMs about it. The problem with our situation was that we were jammed much longer than the company had ever seen before.

The airplane reverted to INERTIAL for navigation, on the POS REF page the GPS position was blank. The RADIO line started tuning DME DME (which it doesn't do unless you lose GPS). We had all sorts of EICAS messages consistent with GPS being lost or jammed (ADS-B OUT L/R, TCAS, TERR POS). The ANP started increasing. I forget the maximum value but it did reach a couple of miles during that short amount of time.

Slowly the GPS signal started to come back and all the messages went away.

It was interesting to watch. Safety reports filed after landing.

I was jammed over southern New Mexico (surprise surprise). Vegas to Lauderdale and GPS never came back. Had to shut the whole plane off for a few minutes in Lauderdale to get it to come back.

Plane Coffee

ANP shouldn't "rapidly rise." If so, then you have bigger problems.

The concern over jamming really doesn't apply to us airline guys. We've got plenty of backups. The concern is for the average GA dude. The FAA has been pushing next gen nav, decommissioning VOR's and NDB's and mandating ADS-B. This has pushed most (?) GA guys to use GPS as their primary, or in some cases only, nav. I've personally witnessed probable GPS jamming outside of NOTAMed air space. So if the military is playing nearby is all GA traffic grounded? If a pilot is near the NOTAMed airspace and is accidentally jammed. Is he a primary target only due to his jammed ADS-B transponder? We're going to a single source for nav options. Personally, I feel it's problematic. But who could have seen this coming......