B737-800
Flight Crew Air Transport Pilot (ATP)
Time Pressure; Workload; Communication Breakdown; Situational Awareness; Human-Machine Interface
ATC Issue All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification
Chart Or Publication; Aircraft; Human Factors; Procedure
We had briefed the RIIVR2 Arrival and ILS 25L approach. Passing GRAMM we still had not been handed off to SoCal Approach. Approaching RUSTT we were handed off to Approach and cleared for RIIVR2 Arrival and ILS 24R approach. This left us high and briefed for the wrong runway. Because we would not be able to satisfy RIIVR crossing restriction; we requested and received relief. While setting up and briefing ILS 24R we passed RIIVR and realized we were navigating to LUVYN still on the ILS 25L approach track. We had insufficient time to enter the ILS 24R procedure in to the FMS and complete the approach briefing for the new runway prior to the IAF due to the late ATC clearance. We requested and received a heading to intercept the ILS 24R approach and were then cleared for the approach. The approach and landing were uneventful. Approach Control did not advise of any loss of separation.
Light traffic into LAX; so ATC allowed us to keep our speed up but then they seemed behind the ball on issuing clearances. We were issued step-down descent clearances initially and were told to expect GRAMM at FL180. I was already in the [mental] 'get the plane down to VNAV PATH' mode. I normally brief my non-flying partner that 'if we get a different runway; you do the FMS while I make sure we comply with altitude; speed and course;' but I did not say that this time. I was still in altitude-chasing mode when the CA noticed we hadn't changed the FMS to 24R.  There was no time to re-brief the new approach and I failed to change the FMS or ask the CA to do it.Stop issuing late runway changes at LAX. This is something that happens over and over. 90% of the time there is plenty of time to make the changes; but 10% of the time it's one of those 'where are we going' moments.
Late descent clearances and an unexpected runway change inbound to LAX on the RIIVR2 STAR overtaxed the flight crew of a B737-800 and required Approach Control vectors while the newly assigned ILS was programmed and activated.