Background
An aircraft was conducting a 14 CFR Part 135 instrument competency check flight under visual flight rules (VFR) during hours of darkness and marginal VFR conditions. The flight was being vectored for an instrument approach.
Accident Sequence
The aircraft impacted mountainous terrain in controlled flight. The flight was instructed by approach control to maintain VFR conditions and was assigned a heading and altitude that caused the aircraft to enter another airspace sector below the minimum vectoring altitude (MVA).
Controller Actions
FAA Order 7110.65, Section 5-6-1, requires that if a VFR aircraft is assigned both a heading and altitude simultaneously, the altitude must be at or above the MVA. The controller did not issue a safety alert. In an interview, the controller stated he was not concerned when the flight approached an area of higher MVA because the flight was VFR and that pilots fly VFR below the MVA every day. At the time of the accident, the controller was working six arrival sectors and experienced a surge of arriving aircraft. The approach control facility supervisor was monitoring the controller but did not detect and correct the vector below the MVA.
Probable Cause
The probable cause, as stated in the official findings, is the failure of the air traffic controller to comply with instructions contained in the Air Traffic Control Handbook, FAA Order 7110.65, which resulted in the flight being vectored at an altitude below the MVA and failure to issue a safety advisory. In addition, the controller's supervisor monitoring the controller's actions failed to detect and correct the vector below the MVA. A factor in the accident was the flightcrew's failure to maintain situational awareness of nearby terrain and failure to challenge the controller's instructions.