Investigation Summary
The flight was conducting a Localizer Directional Aid (LDA) approach to Runway 8 at Juneau. During the descent, the crew reported passing the Barlow intersection, which is the final approach fix located 10.2 nautical miles from the airport. However, the aircraft actually struck a mountain at the 2,475-foot level, approximately 18.5 miles west of the airport. The NTSB found that the crew's instruments were displaying data indicating they had reached the fix when they were still over 8 miles away. The investigation focused on potential signal interference or equipment malfunction, but no definitive source for the erroneous data could be identified. A significant factor noted by the NTSB was the presence of a light aircraft (N769Y) in the Juneau airspace. The controller's focus on coordinating the light aircraft's movements, combined with the crew's own awareness of the traffic, may have created a distraction that contributed to the lack of position cross-checking. While the crew was not required by regulations to cross-check their position using secondary aids like the Sisters Island VOR, they did fail to perform the required audio identification of the primary navigational facility, which might have alerted them to the signal issues.
Final Conclusions
The NTSB determined the probable cause was the display of misleading navigational information concerning the flight's progress along the localizer course, resulting in a premature descent below obstacle clearance altitude. The origin or nature of the misleading information could not be determined. Contributing factors included the crew's failure to use all available navigational aids to verify their position and the lack of a requirement to perform audio identification of navigational facilities.
Photographic Evidence (1)
Video Analysis
Alaska Airlines Flight 1866 air crash | Erroneous readouts — A detailed look at the 1971 crash near Juneau, Alaska, where a Boeing 727 descended prematurely due to misleading navigational data.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Richard C. Adams, with Alaska Airlines since 1955.
First Officer
Leonard D. Beach, hired in 1966.
Second Officer
James J. Carson, hired in 1966.
Systems & Failure Modes
Localizer Directional Aid (LDA)
A type of localizer-based instrument approach that provides horizontal guidance but is not aligned with the runway centerline.
VHF Omnidirectional Range (VOR)
A radio navigation system used for cross-checking positions; the crew did not use the nearby Sisters Island VOR to verify their distance.
Interesting Facts
- 01The accident remained the deadliest single-aircraft crash in U.S. history until 1975.
- 02The aircraft was leased from Hughes Airwest and had 11,344 total airframe hours.
- 03The crash site was 18.5 miles west of Juneau Airport, while the reported fix was only 10.2 miles away.
- 04The investigation could not replicate the exact navigational error despite extensive testing of the localizer and aircraft components.
- 05Visibility at the time was poor, and the crew was flying solely by instruments.
Safety Actions & Advisories
Navigational Aid Cross-Checking
The NTSB recommended that pilots be required to use all available navigational facilities to cross-check their position during non-precision approaches.
Audio Identification Requirements
The investigation led to stricter enforcement and recommendations regarding the audio identification of navigational signals to ensure the correct station is being received.