Date: 201808
Local time of day: 1801-2400
Location: ONT.Airport, CA
Flight conditions: VMC
Weather elements / visibility: 5
Light: Night
Aircraft: Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Descent
Airspace: Class C ONT
ATC / advisory: TRACON SCT
Reporter organization: Air Carrier
Reporter function: Pilot Flying
Human factors: Communication Breakdown; Confusion; Situational Awareness
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Air Traffic Control; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Airspace Structure; Human Factors; Procedure
Primary problem: Human Factors

Narrative: While on the ZIGGY 7 [Arrival]; we were vectored off the arrival just past HITOP on a 140 degree heading and cleared to descend to 8000 feet. As we passed ZIGGY (SBD); we were told to descend to 4000 feet and turn left to a heading of 240 degrees. We queried the controller as to whether he really meant to turn right as ONT airport was on clearly our right side and we would be basically be doing a 270 degree descending turn to our approach course. After a couple of queries going back and forth as to his real intentions for us; we examined the amount of turning space as the Captain and I had our terrain features selected and decided we could easily make the turn as the controller had directed. We were at a relatively slow airspeed and partially configured at flaps 15 and about 215 knots. As we descended and about half-way through the turn at 080 degrees; we heard an instruction without a call-sign to immediately turn right to a heading of 240 degrees and that the minimum safe altitude in that sector was 6000 feet and that we were to climb and maintain 6000 feet. [We were also] asked if we had a visual on the terrain ahead. The instruction was repeated several times and as we ascertained that it was for us; we promptly executed a right turn as instructed while being asked if we had the terrain in sight as we were told the low-level warning bells had sounded in the controller's office. After learning that the instructions were for us; we followed them. We replied that we could see no terrain as it was black outside but that we were monitoring our terrain display and had things under control and that there was no immediate threat yet. As we were monitoring the terrain on our instruments; we were flying as instructed and at no time was there any imminent danger. It was a busy night and perhaps there should have been a second controller handling other sectors on the arrival. During the arrival/approach; [we] were always situationally aware of our position over the ground; terrain; and of our performance capability for vectors and turns assigned; we knew could execute them safely; which we did. The controller did an excellent job as he realized he had vectored us in the wrong direction initially while maintaining and communicating situational awareness throughout the event.




Synopsis: Air Carrier pilot reported ATC assigned a heading which placed them below the Minimum Vectoring Altitude.