Pan Am Flight 812

Pan Am Flight 812, operated by a Pan Am Boeing 707 registered N446PA and named Clipper Climax, was a scheduled international flight from Hong Kong to Los Angeles, California, with intermediate stops at Denpasar, Sydney, Nadi, and Honolulu. On April 22, 1974, the aircraft crashed into rough mountainous terrain while preparing for a runway 09 approach to Denpasar after a 4-hour 20-minute flight from Hong Kong. All 107 people on board perished. The location of the accident was about 42.5 nmi northwest of Ngurah Rai International Airport. Until the 1991 Jakarta Indonesian Air Force C-130 crash, it was the deadliest aviation accident to happen on Indonesian soil.

Accident

Flight 812, a regularly scheduled flight from Hong Kong to Los Angeles via Bali, Sydney, Nadi, and Honolulu, departed Hong Kong on April 22, 1974, at 11:08 UTC (7:08 pm Hong Kong time). The estimated flying time to Bali was 4 hours and 23 minutes. At 15:23 UTC (12:23 am Bali time in 1974), Flight 812 was on final approach to Bali. The aircraft reported reaching 2,500 ft. The Bali Tower gave instructions to continue the approach and to report when the runway was in sight. Acknowledgement was made by Flight 812 by saying, "Check inbound". At 15:26 the pilot-in-command requested the visibility by calling, "Hey – Tower, what is your visibility out there now?"

However, according to the transcription of Air Traffic Control voice recorder this message was never received by the Bali Tower. Apparently this was the last message transmitted by the aircraft. The Bali Tower kept trying to contact the aircraft by calling, "Clipper eight one two, Bali Tower", and "Clipper eight one two, Bali Tower, how do you read", several times. However, no answer was received from the aircraft. It was subsequently found that the aircraft had hit a mountain approximately 37 mi northwest of the Bali airport.

Sequence of events based on the final report

The following sequence of events were based on the final report:

The crew were trying to contact Bali Air Traffic Control, but they encountered several difficulties in doing so. First contact between the aircraft and Bali Tower was established at 15:06 UTC, whereupon Bali Tower instructed Flight 812 to contact Bali Control on frequency 128.3 MHz, because the aircraft was still within the jurisdiction area of Bali Control. That was acknowledged by Flight 812 accordingly. Subsequently, communication between the aircraft and the ground was normal.

Captain Zinke didn't encounter any difficulties on the approach procedure to Denpasar's Ngurah Rai Airport. The procedure stated that before it could land at the airport, the flight should maintain 12,000 ft and should then execute the full ADF let-down procedure. The pilots were aware that there was mountainous terrain on the north of the airport and that flight level 120 would clear the mountains. The crew then informed the controllers of the ETA of Flight 812, and stated their intention to make a right turn within 25 mi from the beacon for a track out on 261 degrees, descending to 1,500 ft followed by a procedure to turn over the water for final approach on Runway 09.

At 15:18 UTC, the crew noticed that the number one ADF was "swinging" while ADF number two remained steady. A few seconds later, the crew of Flight 812 reported to Bali Control that the plane was over the station turning outbound descending to flight level 120. That was acknowledged by Bali Control and Flight 812 was then instructed to change over to Bali Tower. After establishing contact with Bali Tower, Flight 812 reported that they were making outbound procedure at flight level 110 (approximately 11,000 ft) and requested for lower altitude. The plane was later cleared for lower altitude.

The crew of Flight 812 then decided to execute an early right turn on 263 degrees. The early execution of the right turn was caused by the malfunctioning ADF number one. The input was made since the crew assumed that they were nearing the NDB (Non-directional beacon). Investigators stated that the right hand turn was made at a position approximately 30 NM North of the beacon.

Several attempts were made to regain proper indication on the ADFs after the turn, but that couldn't be done because the plane was "shielded" by the mountain. The crew continued their approach and the plane subsequently crashed into the terrain.