Citation Excel (C560XL)
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 60; Flight Crew Total 13300; Flight Crew Type 2200
Workload; Distraction; Time Pressure; Situational Awareness; Confusion
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance
Chart Or Publication; Human Factors; Procedure
While descending on the new DSNEE1 arrival going to LGB; we crossed DSNEE intersection at 8000 feet and 220 knots. We began our descent to cross Mckye at or above 7800 as depicted. ATC called traffic; Aircraft X at our 2 o'clock position; level at 7;000 and converging right to left. We visually acquired the Boeing just as we crossed DSNEE.We were descending on autopilot using FMS/VNAV and when we crossed DSNEE the autopilot began a right turn from our 216 degree heading to the 236 heading required by the STAR and initiated a descent to 7800 feet. As we descended and turned; we got a 'monitor vertical rate' annunciation from our TCAS at about the same time as the aircraft leveled at 7800 feet.This is a new arrival and we believe the fact that we were descending and converging with Aircraft X triggered the RA. We heard the Aircraft X crew advise ATC that they got an RA as well. ATC called us and asked our altitude who was at that time 7800 feet. The RAJEE departure off ONT calls for 7000 feet at RAJEE and that intersection is just south of DSNEE so the step down after DSNEE should probably not begin at DSNEE; perhaps not till Mckye or ATC might have told us to level at 8000 feet until clear of Aircraft X.At no time was there any question of a conflict as both crews had each other in sight and communicated that fact to ATC.
Citation pilot reported that a descent on their arrival was a factor for other traffic departing a close by airport.