Date: 201905
Local time of day: 1801-2400
Location: SCT.TRACON, CA
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class E ZLA
ATC / advisory: TRACON SCT
Second aircraft: B737 Next Generation Undifferentiated
Reporter organization: Government
Reporter function: Approach
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Training / Qualification; Communication Breakdown
Second reporter function: First Officer; Pilot Flying
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Air Traffic Control Issued Advisory / Alert; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Airspace Structure; Human Factors; Procedure
Primary problem: Human Factors

Narrative: The Sector feeding us a 3 aircraft sequence from the east. Two SNA arrivals followed by a ZZZ arrival. The first aircraft; Aircraft Y was coming from the north and they were making that aircraft number one in the sequence; followed by Aircraft X landing SNA and Aircraft Z landing ZZZ. They misjudged the spacing when putting Aircraft Y first and allowed Aircraft X to get to close behind. My trainee reached out to them and asked to slow Aircraft X to 190 knots so that we could build some spacing and not feed the next sector a compressing sequence to the final. Even with this 190 knot speed reduction; it was not enough. At this point we are still not talking to Aircraft X. They realized that the spacing is not going to work so he pulled Aircraft X off the arrival and turned him on a northerly heading. Please note that no coordination has been done regarding any of the aircraft. We thought that they were going to either re sequence Aircraft X behind Aircraft Z or do a little zig zag with Aircraft X to build in a couple of miles in between Aircraft Y.But again we were told nothing by the feeding Controller. So Aircraft X was on a northerly heading for a couple of miles and then we observe the other Controller turning Aircraft X on a southerly heading and it appeared that they were going direct to a fix to rejoin the arrival. Aircraft X was allowed to descend to 7;600 feet by the Controller. This is in the handoff Letter of Agreement between our two sectors that the aircraft will be descending to 7;600 feet. At this time Aircraft Z; the third aircraft in the sequence; has a rapid overtake on Aircraft X. Aircraft X was slowed to 190 knots per my trainee's instructions to the sector and it appeared as if the Controller did not slow down Aircraft Z. So the spacing between the two aircraft was compressing rapidly and a loss of separation was likely. During this time my trainee was dealing with other aircraft and coordination involving a helicopter what was requesting to climb to 10;500 feet and maneuver. When Aircraft X checks in; they are over the fix and are not observed in the turn. My trainee sees that they are not joining the arrival; that they are about to enter a Minimum Vectoring Altitude (MVA) of 7;900 feet while at 7;600 feet and also the Aircraft Z behind Aircraft X is less than three miles with a significant speed overtake. My trainee assigned Aircraft X 8;000 feet and issued a heading of 180. The trainee then issued a low altitude alert to Aircraft X. The trainee chose to keep Aircraft X southbound due to the proximity of Aircraft Z behind. If we turned Aircraft X on a westerly heading climbing to 8;000 feet they would have been dangerously close to Aircraft Y and could have resulted in a mid-air. We knew that the EOVM (Emergency Obstruction Video Map) altitude over the peak was 6;000 feet and chose to climb and direct Aircraft X southbound and to an altitude above the MVA knowing the altitude of the EOVM to avoid an aircraft accident. As soon as she issued these instructions to Aircraft X I called the other sector and told them to move Aircraft Z because we were climbing Aircraft X due to high terrain.There is no way that Aircraft X was going to be able to make the turn at the fix to rejoin the arrival. The turn was too sharp. I do not know what the other sector instructed Aircraft X to do because no coordination was done. This is just my assumption.


Second narrative: [Report narrative contained no additional information.]


Synopsis: SCT TRACON Controller and B737 flight crew reported the aircraft was assigned a heading and route which placed the aircraft below the Minimum Vectoring Altitude.