Originally Posted by
PurpleToolBox
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.
Please reread my first three sentences. The concern isn’t for Boeing guys, it’s for light aircraft. Many Cessna, Pipers, etc have very limited backups, if any. Due to the ADS-B mandate, during a GPS outage their position will only be know by primary radar. All transponder, including Mode C, functions will be inoperative.