B757 Undifferentiated or Other Model
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Time Pressure; Workload
ATC Issue All Types
General None Reported / Taken
Procedure; Human Factors
Multiple changes in flight planning; STARS; headings; fixes; crossing intersection and runways. Multiple times; a heading and altitude off the STAR was given; then assigned direct to a fix; and clearance for another STAR was given. Sometimes within 10 miles of the fix with a crossing restriction. It was difficult to find; load; verify; and execute the FMS in time to meet navigation requirements. ATC would then assign another heading after reporting that we couldn't comply. The flight was very chaotic. Even after reviewing and discussing multiple STAR options during preflight; it was still very frustrating and difficult to comply with all of ATC demands. Multiple STAR; runway; ATC clearance and route changes in a short amount of time in a very busy phase of flight and environment. Speed reductions instead of multiple heading clearances of the STAR; then cleared back to a fix of a different STAR; and runway. The FMC does not program or think fast enough to meet certain clearance demands.
B757 First Officer reported ATC issued multiple changes in the clearance during arrival into LAX; causing a safety concern because of the increased workload.