Widebody; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Troubleshooting; Human-Machine Interface; Distraction; Confusion
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Other / Unknown
Flight Crew Overcame Equipment Problem; Flight Crew Became Reoriented
Aircraft; Environment - Non Weather Related
Initially noticed an EICAS ATC alert. Also heard another aircraft say they lost their GPS reception. 5 minutes later we lost both GPS signals. We followed the QRH procedure. On step 2 of that procedure it says to use radio (DME) updates 'if allowed'. Neither the QRH; nor the FOM; nor any other publication available to the crew tells us whether we are 'allowed' to select and use radio updates. Since the inertial platform was drifting off course rapidly; we selected radio updates and our navigation accuracy returned to normal. We did not get the right GPS back online until east of STL; and we didn't get the left GPS signal back until east of CLE. The crew needs more QRH information regarding this procedure.
Air carrier Captain reported losing both GPS signals; which he attributed to military activity in the area. He successfully switched to an alternative means of navigation until the GPS signal was restored.