Accident
During arrival to pick up a medevac patient, the flight was cleared for an LDA-1 runway 08 approach via the Asort transition. The pilot should have continued southeast on J-541 toward the SSR vortac and intercepted the localizer at Asort, then track inbound on the localizer (062°) using I-JDL frequency 109.9 MHz (frequency for localizer and co-located DME). After Asort, minimum altitudes were 6,500 feet to Dibol intersection, 5,100 feet to Lynns intersection, and 3,400 feet to the final approach fix at Barlo intersection. DME from I-JDL to the intersections was 18.2, 13.5, and 8 miles; DME from SSR (south of localizer track) was 11.2, 12.7, and approximately 16 miles.
The flight reported Asort inbound while descending through approximately 9,500 feet. The last radio call was 30 seconds later while descending through 8,200 feet, 14 miles west of Dibol. Approximately 4 miles west of Dibol, the aircraft impacted the mountain side at 3,500 feet mean sea level. No preimpact mechanical malfunction was found. There was evidence that both navigation receivers were tuned to 109.9 MHz, but the DME control head was inadvertently left in the 'hold' position (locking DME to SSR rather than I-JDL), and the crew began a premature descent. Juneau weather included 600 feet scattered, 3,000 feet overcast, and 7 miles visibility. The pilot-in-command was currently flying both a Learjet and a DHC-7. All four occupants (two pilots and two doctors) were killed.
Investigation
The investigation found no preimpact mechanical malfunction. Evidence indicated the DME was in hold, and the crew started descending early.
Probable Cause
The official probable cause findings include: in-flight collision with terrain during approach from initial approach fix to final approach fix; communication/navigation equipment (distance measuring equipment) not switched; improper use of flight/navigation instruments; habit interference by the pilot-in-command; inadvertent loss of orientation by the pilot-in-command; premature descent; hazardous condition not identified by the copilot; dark night light condition; cloud weather condition; mountainous/hilly terrain; proper altitude not maintained by the pilot-in-command; and rising terrain.