Date: 201505
Local time of day: 0601-1200
Location: PHX.Airport, AZ
Flight conditions: VMC
Light: Daylight
Aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B PHX
ATC / advisory: Center ZAB; TRACON P50
Aircraft component: FMS/FMC
Component problem: Design
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Human-Machine Interface; Distraction; Confusion; Communication Breakdown; Situational Awareness; Workload; Time Pressure
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Contributing factors: Environment - Non Weather Related; Airspace Structure; Human Factors; Procedure
Primary problem: Procedure

Narrative: We were cleared by Albuquerque center to descend via the EAGUL6 with an east landing. We selected 7;000 in the altitude and soon began the descent.  All crossing restrictions and speeds had been verified by both pilots. However; soon afterward there were multiple interruptions to the arrival by Albuquerque center taking us repeatedly off the profile. They included giving hard altitudes to stop at; speed changes differing from the arrival and even a heading off of the arrival and eventually cleared to return to the eagul6 arrival and then handed off to Phoenix approach.  With this much confusion I looked at the FMC to confirm that we were going to cross our next point (GENO) as prescribed on the eagul6. It showed we would indeed cross it at 11;000 (is prescribed for crossing between 11;000-12;000). However we were once again given a speed deviation by Phoenix approach but comply with altitude restrictions.  The next things happened almost simultaneously: we received a TCAS TA; saw the traffic; Approach asked us our altitude; we responded. We said climbing back to 10;000 (which was where we were supposed to cross the next point; QUENY. The First Officer (FO) (flying pilot) immediately disconnected the autopilot and we were back at 10;000 within seconds. No TCAS RA was issued.I cannot say for certain; only guess; as to why the aircraft did not respect the altitude restrictions. The MULTIPLE speed; course; and altitude changes on an already difficult arrival certainly was a contributing factor.  I can also say that although we had obviously been pushed into the 'red' that 'automation' (TCAS); 'external resources' (ATC); 'knowledge; skill and aircraft handling' -as described in the model of the threat and error management - brought us back out of the 'red'One of the purposes of the RNAV arrival is that once cleared on it everyone should be doing the same speeds; altitudes; etc so there is little need for ATC intervention. I do understand some adjustments may need to be made. The event we were taken through was beyond the ordinary and pushed the airplane and the crew to the edge.  This should not happen on an RNAV approach.  Once ATC decides the need to start manipulating an aircraft to this degree they should take over full responsibility for issuing speeds and altitudes for the remainder of the flight. Of course the other option is for the crew to refuse to return to following the RNAV arrival and request hard altitudes and speeds be issued by ATC.




Synopsis: An air carrier on the PHX EAGUL6 RNAV was vectored off the arrival and given altitude changes so that when cleared back onto the track; the aircraft failed to capture a 10;000 foot altitude constraint. Similar malfunctions occur at other airports where ATC makes extensive RNAV changes causing the FMS to not respect crossing altitudes.