Investigation Summary
The accident occurred during a scheduled cargo run from Anchorage to Dillingham with an intermediate stop in King Salmon. While en route to Dillingham, the crew requested the RNAV/GPS Runway 19 approach. The Anchorage ARTCC controller issued a clearance to 'maintain at or above 2,000 feet until established on a published segment of the approach.' This clearance was technically improper as the aircraft was in a Terminal Arrival Area (TAA) where the minimum altitude was 5,400 feet. The crew read back 'maintain 2,000 until a published segment,' which the controller did not correct. As the aircraft descended, the crew requested to enter a holding pattern at the ZEDAG initial approach fix to check runway conditions. The controller cleared them to hold 'as published.' The crew initiated the hold at 2,000 feet, unaware that the published holding altitude was 4,300 feet. During the outbound leg of the hold, the aircraft's radar data triggered a Minimum Safe Altitude Warning (MSAW) on the controller's display, consisting of a flashing indicator and an aural alarm. The controller, later citing 'alarm fatigue' from frequent nuisance alerts, did not notice or act upon the warning. The aircraft impacted a southeast-facing slope in the Muklung Hills, approximately 6 miles north-northwest of the approach fix.
Final Conclusions
The NTSB determined the probable cause was the flight crew's failure to maintain terrain clearance, resulting in controlled flight into terrain (CFIT) in instrument meteorological conditions. Contributing factors included the crew's failure to correctly read back and interpret clearance altitudes, their failure to adhere to published minimum altitudes on the approach chart, and their failure to follow company checklists. Additionally, the air traffic controller contributed by issuing an ambiguous clearance, failing to correct the pilot's incorrect readback, and failing to monitor the flight or respond to MSAW alerts.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Jeff Day, age 38. Toxicology found low levels of doxylamine (antihistamine) below therapeutic range. Autopsy identified severe coronary artery disease with greater than 85% stenotic lesion, though the NTSB found no evidence of medical impairment contributing to the accident.
First Officer
Neil Jensen, age 21. Hired by the company in November 2012. Was off duty the day prior to the accident.
Systems & Failure Modes
Minimum Safe Altitude Warning (MSAW)
A ground-based radar system function that alerts controllers when an aircraft is predicted to be in proximity to terrain. In this case, the controller did not notice the aural or visual alerts.
Bendix/King KMD 850 / Garmin 430W
Onboard avionics capable of providing terrain warnings. Damage prevented investigators from determining if these systems were active or inhibited by the crew.
Interesting Facts
- 01The aircraft was not equipped with, nor required to have, a CVR or FDR.
- 02The published minimum altitude for the TAA segment the aircraft was in was 5,400 feet.
- 03The published minimum holding altitude at ZEDAG was 4,300 feet.
- 04The controller's radar display showed a flashing MSAW alert for several minutes before the crash.
- 05The captain had 5,470 hours of experience on the Beech 1900 type.
- 06The wreckage was located at coordinates 59.317779, -158.351104 on a southeast-facing slope at an elevation of about 1,996 feet.
Safety Actions & Advisories
Voluntary Recorder Installation
Following a previous accident in 2010, Alaska Central Express management opted to voluntarily install cockpit image recording systems in all company aircraft, though N116AX had not yet been equipped at the time of the crash.
ATC Safety Alert Compliance
The NTSB investigation highlighted the failure of the controller to respond to MSAW alerts, leading to renewed emphasis on FAA Order 7110.65 requirements for controllers to issue safety alerts when an aircraft is in unsafe proximity to terrain.