Originally Posted by
Freight Dawg
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......
Sure it is a concern. Backups?
What happens when you lose GPS updating? You revert to inertial and radio updating (I can speak only for 777 and probably most Boeings). Yes, there's still a navigation solution being calculated. However your operations become greatly degraded. You can't fly in RNP4, RNP2, FANS (depending on location), or ADS-B require airspace. You can't fly any procedures that require GPS.
Since writing my first post on the subject above, on my last flight we had GPS jamming indications over Eastern Montana/Western South Dakota. I checked the POS REF page and sure enough we were back to radio updating. It didn't cause any further issues other than some safety paperwork to be filed.