Investigation Summary
The accident occurred during a multi-stop journey from Hong Kong to Sydney, with a final terminus in Los Angeles. As the aircraft approached Bali at night, the crew relied on Automatic Direction Finder (ADF) equipment to identify their position relative to the NDB (Non-Directional Beacon). During the descent, one of the two ADF needles swung, leading the captain to believe they had passed over the station. However, the second ADF needle remained steady, indicating they had not yet reached the beacon. Despite this discrepancy, the crew executed a right turn to intercept the 263 degree outbound track while still approximately 30 nautical miles north of the station. This maneuver placed the aircraft on a collision course with the mountainous terrain of northern Bali. The investigation highlighted that the crew had limited experience with the Bali night approach and failed to cross-check their position using other available instruments or the second ADF needle.
Final Conclusions
The Indonesian Directorate General of Air Communications concluded the probable cause was the premature execution of a right-hand turn based on the indication of only one ADF needle while the other remained steady. Contributing factors included the crew's failure to verify station passage and the lack of radar coverage at Denpasar, which prevented air traffic controllers from identifying the aircraft's incorrect position.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Systems & Failure Modes
ADF (Automatic Direction Finder)
A radio-navigation instrument that automatically displays the relative bearing to a ground-based radio station (NDB).
NDB (Non-Directional Beacon)
The ground-based radio transmitter that the aircraft's ADF uses to determine position and station passage.
Interesting Facts
- 01The aircraft involved, N446PA, was named 'Clipper Climax' and had appeared in the 1971 film Willy Wonka & the Chocolate Factory.
- 02At the time, it was the deadliest aviation accident in Indonesian history.
- 03The crew initiated the premature turn approximately 30 nautical miles north of the beacon, but the final impact occurred approximately 37 to 42.5 nautical miles northwest of the airport.
- 04The recovery effort was extremely difficult due to the dense jungle and steep terrain, requiring paratroopers and ground teams.
- 05Identification of victims was largely impossible; remains were eventually buried or cremated in mass ceremonies on a Bali beach.
- 06The aircraft had accumulated approximately 34,000 flight hours over 14 years of service at the time of the accident.
Safety Actions & Advisories
GPWS Development
The accident, along with other contemporary CFIT events, accelerated the industry-wide adoption and regulatory mandate of Ground Proximity Warning Systems (GPWS).
Navigation Procedures
Pan Am and other carriers reinforced training regarding the verification of station passage using multiple instruments before initiating turns in mountainous terrain.