What happened
During an instructional flight in instrument conditions, the aircraft was cleared for the VOR-A approach by the TRACON controller (POMR) at 1929. After contacting the tower local controller (LC), the pilot reported being on the approach outside of the final approach fix. Two minutes later, the POMR controller observed the aircraft circling the airport and queried the LC regarding its track.
The LC asked the pilot if they intended to cancel IFR or continue the approach; the pilot elected to continue. The LC noted the aircraft appeared west of course and requested the pilot report the runway in sight. At 1932:20, the pilot reported having the airport in sight, leading the LC to inform POMR that the pilot was canceling IFR. Consequently, the POMR controller dropped the aircraft's data block from his radar display.
Approximately 47 seconds later, the pilot informed the LC they did not have the runway in sight but noted seeing the ground and a freeway. After briefly reporting the airport in sight again, the pilot was cleared to land runway 26L. However, by 1934:25, the LC noted the aircraft was three miles west of the airport and suggested a heading of 080 degrees while instructing the pilot to maintain visual flight conditions.
At 1936:02, the pilot again reported not having the airport in sight. The LC instructed a 10-degree right turn to enter the downwind and provided updated distance information. Although the pilot eventually reported the airport in sight and was cleared to land, the aircraft subsequently deviated from its track toward the airport. At 1939:29, the pilot requested a missed approach.
During a subsequent discussion between the LC and the TRACON controller regarding the flight's IFR/VFR status, the TRACON controller suggested that if the pilot was in IMC without visual contact with the airport, the aircraft should turn southbound immediately. The LC instructed the pilot to turn south and climb to 5,000 feet, but there was no response from the flight. The airplane subsequently collided with rising mountainous terrain.
The investigation
Review of recorded radar data revealed that starting at 1933:10, the Minimum Safe Altitude Warning (MSAW) system was flashing alerts on both the TRACON and tower DBRITE radar displays. However, once the TRACON controller dropped the aircraft's data tag, the MSAW alert was automatically suppressed at the TRACON level. Additionally, a review of air/ground communications confirmed that neither controller issued an explicit terrain avoidance advisory to the flight crew.