B747-400
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Fatigue; Human-Machine Interface; Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Returned To Clearance
Airport; Human Factors; Procedure
We departed late due to a late inbound aircraft. We flew an RNAV STAR arrival and received vectors abeam the airport. Due to the late arrival into the normally busy airport the traffic pattern was clear. The ILS to [Runway] XXL was out of service and visual approaches were in use. We loaded the RNAV (GPS) Y Runway XXL into the FMS for backup guidance for the visual. While on vectors I extended the centerline off the FAF; however; when I executed the modification; the centerline extended off [Runway] XXL and the FAF was deleted from the route; along with its 2;400 FT crossing restriction. We were on a southerly heading at 3;000 MSL; outbound abeam the FAF when the Controller turned us to a 080 heading for a base leg. I reentered the FAF into the FMS and extended it; but did not enter the hard altitude of 2;400 FT. The Controller asked if we had the field in sight; we said yes and he cleared us the visual approach to [Runway] XXL. We were in heading select/VNAV with the autopilot and autothrottles on. I made the mistake of entering the DA for the RNAV approach in the altitude window; 900 FT. I should have entered 2;400; the final approach fix altitude. The First Officer remained in heading select/VNAV when LNAV should have been selected. I'm not sure what the FMA was at this point because I was looking outside. I believe we were in THR; HDG SEL; VNAV SPD. I noticed we were not intercepting the runway centerline by visual cues to the runway; I told the First Officer we were overshooting and needed to turn. He began his turn and corrected to the runway centerline. I saw that we were low on the glidepath; four red lights on the PAPI; and told the First Officer we were low. Just after I said that we received an EGPWS TERRAIN; TERRAIN alert. The First Officer immediately executed the CFIT maneuver. I noted we were above 1;600 MSL at the time of the alert. Almost immediately after the maneuver was initiated the alert stopped and we were on glidepath with two white and two red PAPI lights. I believe the alert was triggered by the hill that sits on final for [Runway] XXL. We both felt that terrain was no longer a factor and configured the aircraft for landing; we were flaps 10; speed 10 at the time of the alert. After the maneuver we were at least 1;800 MSL; were fully configured and stable before 1;000 AGL. We landed uneventfully. Several factors contributed to this event: First; the ILS XXL out of service. Next; probably extending the centerline off [Runway] XXL instead of the FAF. Third; trying to reenter the FAF on a clear night with unlimited visibility. Fourth; not selecting LNAV on base leg. Fifth; entering the Decision Altitude in the altitude window when we were not on the approach; selecting the FAF altitude would have stopped our descent and the alert probably would not have happened. Last; both pilots relying too much on the [automation] when we should have been looking outside and using visual cues as the runway was in sight and the PAPI clearly visible. Although I didn't feel tired at the time; it was the middle of the night and we had been on duty in excess of 8 hours. I believe fatigue contributed in some way.
Based on the early morning hour I thought it would be prudent to utilize a high level of automation. This is something we do often when backing up a visual approach with the ILS. My plan was to intercept the final approach course and path for the RNAV 35L outside the FAF with LNAV and VNAV. Then I would fly the path on autopilot until fully configured and land manually. When the FAF reappeared on the ND I adjusted my heading to intercept the final approach course outside of it but neglected to arm LNAV... ...As we started to cross the final approach course I disengaged the autopilot and autothrottles and manually turned the plane back to centerline. I could not see four distinct lights on the PAPI but I could see white and red. I came inside to check airspeed and when I came out the PAPI was all red. I suspect that I let the nose drop as I came in and descended below the last white indicator......Conclusions: I am confident in our non-precision approach procedures and my ability to shoot a non-precision approach. That being said; I had never used one as a back up for a visual approach. It seemed like a reasonable alternative to using the ILS as a backup; but looking back that is not the case. Unlike an ILS; the [descent] path of the non-precision approach can be accidentally modified. I believe that when the FAF was deleted and reentered the resulting path was from 3;000 FT at the current aircraft position to the runway. That path would be a lower shallower path than the one published and would cross below 2;400 FT at the FAF. That mistake; combined with my forgetting to arm LNAV; created a bigger problem. At the critical time of crossing the FAF during a non-precision approach; I was forced to be eyes out adjusting back to centerline because I was flying a poor visual approach. I was not monitoring the FMAs and the path at that point like I normally would during a non-precision approach. We did not crosscheck the altitude at the FAF; which would have indicated that we were below the profile or that the path was inaccurate. The result was a low approach; with a hill below us; which triggered the EGPWS......FMS data entry mistakes can corrupt the path during a dynamic period close to landing. You may not recognize them because you are looking outside (as you should on a visual approach). We are taught that using the appropriate level of automation during flight reduces risk. My experience suggests that in this situation I attempted to use too much automation. We are also taught to recognize real-time when it is appropriate to downgrade to a lower level of automation. I did not downgrade until we overshot final. I should have downgraded at the moment the FAF was deleted. At that point I should have forgotten about the RNAV backup and focused solely on the visual approach. The EGPWS did its job.
An important and illuminating report that addresses the effect of inappropriate and/or improper modifications programmed into the autoflight system by a fatigued flight crew cleared to fly a visual approach on a clear night. They ultimately received an EGPWS 'Terrain' warning for descent below that prescribed by the RNAV approach they had programmed specifically to act as a backup/support mechanism to mitigate the effects of their fatigue.