A321
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Total 7000
Conflict Airborne Conflict; Deviation - Altitude Crossing Restriction Not Met
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Air Traffic Control Separated Traffic; Flight Crew Took Evasive Action
Aircraft; Airspace Structure
Captains leg; departed on runway 1R out of LAS. We climbed out on the Cowboy 6 RNAV; and as we briefed at the gate; flaps 1 would remain extended in order to make the 13000 ft at or above crossing restriction at RIOOS. The Captain maintained airspeed just above the hook in order to fly a maximum rate of climb for SID compliance. Somewhere between 8000 and 9000 ft we received a TA indicating that an aircraft was climbing from behind and below us; and in close proximity. ATC then assigned us a right turn to the south just as we received the TCAS RA and the corresponding display on the PFD. In order to comply with the RA; The Captain raised the nose just enough to put the aircraft in the bottom of the green bar; and also simultaneously turned to the ATC assigned heading. Sometime during the event; the conflict aircraft (flight on the same departure) was also given altitude and heading instructions that may or may not have increased the conflict. I observed that the 737 was also turning to the south in order to avoid us. Whether or not he was responding to his own RA instructions; or ATC's instructions; I simply don't know. After the RA was resolved; ATC indicated that we should've notified him that we were flying a slower than normal airspeed in order to comply with the SID crossing at RIOOS. I informed the controller that the slow airspeed was for operational purposes to comply with the altitude restrictionIn retrospect; this was clearly a restriction that only an A321 could make if it were something close to its empty operating weight. In my opinion; the constraints on this departure do not conform to the A321's capabilities; especially considering that this was a very cool day in March as opposed to a high; hot; heavy August scenario.
A321 First Officer reported an aircraft triggered a TCAS RA from behind and below on the LAS COWBY6 departure. ATC commented on the slow climb that the flight crew felt was required to meet the 13;000 ft crossing restriction.