Commercial Fixed Wing
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 178; Flight Crew Total 27000; Flight Crew Type 1857
Human-Machine Interface; Situational Awareness; Distraction
Inflight Event / Encounter CFTT / CFIT
Flight Crew Became Reoriented; Flight Crew FLC Overrode Automation; Flight Crew Overcame Equipment Problem
ATC Equipment / Nav Facility / Buildings; Airport; Airspace Structure; Environment - Non Weather Related
On approach into LLBG; received multiple GPWS TERRAIN WARNINGS and elected to continue the approach with reference to Flight Manual 'DAY VISUAL CONDITIONS.'ATIS said to expect GPS interference. I had done the exact same RNAV Arrival GEFEN 1C to join the ILS X RWY26 Approach the week before and so I was familiar with the approach and terrain. When the terrain warning first went off; I disconnected the autopilot and was ready to perform the escape maneuver; but I looked out the window and could see we were above the terrain at a safe altitude. The warning stopped anyway and so I reconnected the autopilot and continued the approach. A few minutes later; we got another TERRAIN WARNING and again I had the terrain in sight and elected to continue the approach. After landing; we debriefed what had occurred and decided it may have been a safer course of action to perform the escape maneuver or request radar vectors from approach control.The airplane self-reported a maintenance write up to Maintenance Control. Nose Number [Aircraft X]:DEFECT: TERR POS                                                        ADVISORY                                                        THE GND PROX HAS DETERMINED THAT HORIZONTAL POSITION            UNCERTAINTY EXCEEDS ITS LIMIT.                          ACTION: CLR - MAINT MSG INACTIVE. REF         FIM. INTERMITTENT FAULT; NO FURTHER           ACTION REQUIRED.                   On departure from LLBG the next [flight]; I noticed that the airplane we were departing with (a different Nose Number from our incident airplane) had a similar write up referencing 'TERR POS ADVISORY THE GND PROX HAS DETERMINED THAT HORIZONTAL POSITION UNCERTAINTY EXCEEDS ITS LIMIT'. This leads me to believe that it is not an airplane specific problem; but rather a GPS interference problem that caused the GPWS WARNING.The below is the reference from the [Aircraft] Flight ManualTERRAIN WARNINGSCondition: EGPWS/GPWS senses terrain or obstacle encounter within 20-30 seconds or terrain clearance floor.The following are EGPWS/GPWS terrain aural warnings:* 'Terrain; terrain'* 'Terrain; terrain; pull up; pull up; pull up'* 'Too low terrain'* 'Pull up; pull up'* 'Obstacle; obstacle; pull up; pull up; pull up'Choose one:If during day visual conditions and positive visual verification is made that no obstacle or terrain hazard exists:[PF] Immediately take positive corrective action until warning ceases and/or terrain/obstacle clearance is assured.[PM] Advise ATC of any clearance deviations.During the GPWS event; there was a lot of noise on the Flight Deck due to the various sirens and voice warnings. This creates confusion and difficulty communicating effectively. I was unable to effectively communicate my intentions to the First Officer and the Relief Pilot. I was not able to seek adequate input from them; but knew that it was a false GPS WARNING due to the ATIS information about GPS interference and my looking out the window and confirming that we were above the terrain. I also knew that the flight manual allowed me to continue the approach with the above provisions. However; after landing and debriefing it became evident to me that the First Officer hadn't been comfortable with me continuing the approach. He did not communicate that to me during the approach though. We also neglected to inform ATC that we had received a GPWS TERRAIN WARNING. After discussing the event with the other 2 pilots; I determined that we should have requested radar vectors and terrain clearance from ATC rather than continue on the RNAV Approach.Lastly; it may be prudent to restrict company flights to LLBG from flying this particular RNAV arrival and approach until this anomaly can be resolved.
Upon arrival to LLBG; ATIS made note of possible GPS interference. We were cleared the ILS X Runway 26. Approaching the fix RABIN at 3;800 MSL; we received a TERR POS EICAS message. Shortly after; we received an aural terrain caution with no visual terrain on the HSI. We verified we were on course at the proper altitude. We soon received a terrain warning. Once again; we verified proper course and altitude. The Pilot Flying disengaged the Autopilot to prepare from the avoidance maneuver. We were daylight VMC and visually verified clear of terrain; so we elected to continue the approach. Making the turn to final warnings ceased. The Captain mentioned the same thing happened on a prior flight to this same approach. Then on final a few miles from the runway; clear of terrain; on profile and the runway in sight; we received more terrain warnings. The warnings ceased and we landed uneventfully.
Air carrier flight crew reported they had multiple terrain warnings on approach; the ATIS aforementioned possible GPS interference.