B737-500
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 235
Situational Awareness; Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Aircraft; Human Factors
On descent into LAX; we were cleared the RIIVR Arrival and subsequently cleared to cross GRAMM at FL190. On being handed off to SoCal; we were directed to proceed to RIIVR for 24R; descend to 14;000 FT and maintain 300 KTS or greater. At that time I selected Level Change and set 14;000 FT in the Altitude window to initiate the descent. The FMC had been previously programmed for Runway 24R; so we verified the route and reprogrammed the Descent page for 300 KTS. Subsequently; we were cleared for the ILS to 24R. My First Officer and I both confirmed the routing and modes and I set 2;200 FT in the Altitude window. Approaching 10;000 FT on the arrival; our attention was diverted by a loss of flight director bars on the First Officer's ADI. At approximately 9;500 FT; I realized that we were not leveling or slowing. I disengaged the autopilot and started a climb back to 10;000 FT. At this time SoCal gave us a frequency change and stated we were low and directed us to maintain 9;000 FT and re-cleared us for the ILS 24R. The remainder of the approach and landing was uneventful.Upon evaluation of this event; both the First Officer and I felt we had confirmed an LNAV/VNAV descent and had set the appropriate altitudes. As we descended; I was crosschecking the LEGS page restrictions and we were on a good descent gradient. However; I obviously did not realize we were still in Level Change; which created the altitude issue. After reflecting on this event; I feel there were several contributing factors. First; I have become somewhat complacent with the LNAV/VNAV arrivals as they become routine and I have come to trust the machine. Additionally; I think that when we were confirming our descent mode; we saw what we wanted to see (descending on path at 300 KTS) not the mode that was actually engaged; Level Change. Finally my comfort level of having done the arrival hundreds of times contributed to me diverting my attention to something trivial at a time when my attention should have been on ensuring the LNAV/VNAV was doing what I wanted it to do. The lesson for me from this event is twofold. First and foremost is to trust but verify the machine. Second; and the more difficult; is to make much more of an effort to guard against complacency.
On approach into LAX on the RIVVR Arrival; ATC instructed us to speed up to 300 KTS. After reprogramming the FMC; ATC then instructed us to go directly to RIIVR for 24R and descend to 14;000 FT and maintain 300 KTS. About this time my ADI flight director bars disappeared and there were red flags in view. I told the Captain and we got caught up in trying to figure out what happened. I forgot to continue my pilot not flying duties and became distracted with the minor malfunction. ATC gave us a frequency change and; as I was switching; she said to maintain our current altitude since we were below the crossing restriction altitude. I then noticed we were passing about 9;500 FT and still at 300 KTS. The Captain disengaged the autopilot; climbed back to 10;000 FT; and began to slow to 250 KTS. I told ATC 'sorry;' and she said; 'No problem; contact Approach.' I switched over and the approach continued normally and uneventfully. Once on the ground; we debriefed the approach and deduced what had happened was the Captain selected Level Change and I forgot to verbalize LNAV/VNAV PATH. I felt that I had become complacent with the automation of the aircraft; pilot not flying duties; and got caught up with a minor distraction that would not have had an impact on the approach.
B737-500 flight crew reports an altitude deviation during the RIIVR 2 arrival to LAX when they are given direct to RIIVR from over GRAMM and 300 KTS or better. Level Change was selected for descent to 14;000 FT then forgotten when 2;200 is set for the final approach fix altitude.