Narrative:

There was some initial confusion on our cleared routing from clearance delivery. We were not cleared as filed; but rather via [route 1]. Prior to engine start; we clarified with ATC that our routing was [route 1 to lax]. Initially after departure; los angeles center cleared us direct to zzzzz. Zzzzz was not one of the waypoints on our cleared route which we queried center about. They seemed confused that zzzzz waypoint was not on our flight plan and said they would check with socal to find out what routing they would prefer for our arrival. Eventually they called us back and cleared us to lax via SADDE8. This arrival is what we were originally filed to fly. Passing 11;000; ATC requested that we level off at 11;000 which we momentarily went above because we had been cleared higher and then descended back down to 11;000 complying with ATC's instructions. We entered the new arrival/routing information into the FMS and verified the accuracy. The waypoints on the arrival are the same fixes as the [route 1] routing we had. A FMS discontinuity was where we expected it to be after smo and confirmed. We continued to fly the assigned routing. Approach assigned us a 040 degree heading along with a continued descent into lax. Approach queried us on what our heading was departing smo. It appeared as if the FMS reverted to dead reckoning mode and we actually flew closer to 080 heading instead of what should've been a 070 heading departing smo for that arrival procedure. The rest of the flight was continued as would be expected for our arrival into lax runway 24R.ATC provided us with clearances normally associated with RNAV routing [for this flight leg]. It appeared as if the controllers were expecting us to arrive lax via different routing (we were using non-RNAV routing). Additionally; our routing was changed repeatedly over the course of an already very short leg. Numerous changes/requests by la center over a very short period of time further compressed the crew's time and ability to manage tasks in the cockpit for an arrival into the highly saturated airspace of lax. Reducing the amount of reroutes/changes in flight within the final 15 minutes from landing would have provided the crew better ability to manage their arrival/tasks into lax.

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Original NASA ASRS Text

Title: Air Carrier flight crew reported confusion with ATC and receiving multiple reroutes on short flight resulting in increased workload.

Narrative: There was some initial confusion on our cleared routing from clearance delivery. We were not cleared as filed; but rather via [Route 1]. Prior to engine start; we clarified with ATC that our routing was [Route 1 to LAX]. Initially after departure; Los Angeles Center cleared us direct to ZZZZZ. ZZZZZ was not one of the waypoints on our cleared route which we queried Center about. They seemed confused that ZZZZZ waypoint was not on our flight plan and said they would check with SoCal to find out what routing they would prefer for our arrival. Eventually they called us back and cleared us to LAX via SADDE8. This arrival is what we were originally filed to fly. Passing 11;000; ATC requested that we level off at 11;000 which we momentarily went above because we had been cleared higher and then descended back down to 11;000 complying with ATC's instructions. We entered the new arrival/routing information into the FMS and verified the accuracy. The waypoints on the arrival are the same fixes as the [Route 1] routing we had. A FMS discontinuity was where we expected it to be after SMO and confirmed. We continued to fly the assigned routing. Approach assigned us a 040 degree heading along with a continued descent into LAX. Approach queried us on what our heading was departing SMO. It appeared as if the FMS reverted to dead reckoning mode and we actually flew closer to 080 heading instead of what should've been a 070 heading departing SMO for that arrival procedure. The rest of the flight was continued as would be expected for our arrival into LAX runway 24R.ATC provided us with clearances normally associated with RNAV routing [for this flight leg]. It appeared as if the controllers were expecting us to arrive LAX via different routing (we were using non-RNAV routing). Additionally; our routing was changed repeatedly over the course of an already very short leg. Numerous changes/requests by LA Center over a very short period of time further compressed the crew's time and ability to manage tasks in the cockpit for an arrival into the highly saturated airspace of LAX. Reducing the amount of reroutes/changes in flight within the final 15 minutes from landing would have provided the crew better ability to manage their arrival/tasks into LAX.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.