Date: 201604
Local time of day: 0601-1200
Location: ZLA.ARTCC, CA
Flight conditions: Mixed
Weather elements / visibility: Icing; Turbulence
Light: Daylight
Aircraft: Medium Large Transport; Low Wing; 2 Turbojet Eng
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZLA
ATC / advisory: Center ZLA
Second aircraft: Small Transport; Low Wing; 2 Turbojet Eng
Aircraft component: FMS/FMC
Component problem: Malfunctioning
Reporter organization: Corporate
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: Enroute
Anomaly: Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance
Contributing factors: Airspace Structure; Human Factors; Aircraft
Primary problem: Human Factors

Narrative: The KEFFR THREE ARRIVAL was programmed into the FMS and crossing restrictions were confirmed present and correct. Autopilot and Autothrottles were armed and the Aircraft was traveling at approximately 300 KTS. After crossing EDANE at FL240 we were instructed to descend via the KEFFR THREE ARRIVAL. We set 8000 ft (altitude at KEFFR) and armed VNAV. Shortly after we noticed that the aircraft was not descending; that the VNAV path vector was displaying erroneous information and that the left and right VNAV indicator on the PFDs did not match. We armed Vertical Speed and set a rate of 3000 ft/minute. Shortly after the controller asked if we were descending on the arrival and we confirmed that we were. The controller then instructed us to increase our descent rate because he didn't think we would be able to meet the restriction at CAARR (13000 ft/280 KTS). We set our descent rate to 5000 ft/min. Shortly after he instructed us to level off at FL180. We entered FL180 into the Altitude Selector. The Auto Pilot was unable to level off at FL180; possibly due to the time permitted; aircraft speed and descent angle. We disarmed the Autopilot and stopped the descent so that we could climb back to FL180. Before we could climb back to FL180 the controller instructed us to descend via the KEFFR THREE ARRIVAL once again. We were instructed to contact the control center via phone for a possible pilot deviation.


Second narrative: Aircraft X was at FL240 on the KEFFR3 arrival HEC transition. The r-side issued a descend via clearance at XA:40. We already had radar on aircraft Y landing PSP at 170 and no additional restriction was issued to get Aircraft X below Aircraft Y. Initially the KEFFR2 arrival had a built in restriction to separate from the PSP arrivals but when the KEFFR3 arrival came out that restriction was removed making PSP arrivals traffic for KEFFR3 arrivals. This creates an unsafe situation every time we have both arrivals at the same time. At XA:42 the r-side stopped Aircraft X at FL180. The r-side also made a transmission to Aircraft X that he wasn't going to make the restrictions and needs to expedite his descent which may have caused some confusion. At XA:43 r-side issued a 25 degree left vector to Aircraft Y to allow the 2 aircraft to cross further north so that Aircraft X could continue the descent. At XA:44 Aircraft X descended below FL180 creating a loss of separation.Add a restriction back to the KEFFR arrival to separate these 2 arrival courses. The KEFFR2 arrival had a restriction to cross BARSE intersection at or below 15000 which ensured separation.


Synopsis: Corporate Captain reported a delay in starting the descent on the KEFFR 3 Arrival to SNA which led to an overshoot at an intermediate level off. ZLA Controller reported a loss of separation with an aircraft descending to PSP.