Small Transport; Low Wing; 2 Turbojet Eng
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 4
Communication Breakdown; Time Pressure
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Human Factors; Procedure
Training in progress. Aircraft was on arrival into SNA at 080. We issued a descend clearance to 060 and speed of 190kts. Aircraft read back '60 to a 190'. Aircraft then turned to a 190 heading directly into an MVA of 079 descending out of 080. The proximity of the boundary line to the arrival was less than 1 mile; given us not time to fix the situation until it was too late. We observed the turn and issued a stop descend; low altitude alert; and climb back to 080 immediately. Be more vigilant in verifying the correct read back when doubt occurs because of the proximity of the higher MVA.
SoCal TRACON Controller reported a bad readback from a pilot which caused an instantaneous airspace violation.