On November 16, 2006, a Boeing/B757-200 (registration B-27015) was involved in an aviation accident near 99NM south of the Jeju Island， Korea/in the air, TW. No fatalities were reported. Investigators recorded the probable cause as: The EF306 flight crew did not complete the TCAS RA standard operation procedures and commenced an excessive high rate descent. The induced negative G-force resulted in the occupants' injury. This summary draws on records from the Taiwan Transportation Safety Board (TTSB).
On November 16, 2006, a TCAS event occurred between Far Eastern Air Transport Flight EF306 and Thai Airways Flight TG659, 99 NM south of Jeju Island, Korea, resulting in injuries to 20 people and minor aircraft damage.
Incident Overview and Investigation Scope On November 16, 2006, Far Eastern Air Transport Flight EF306, a Boeing 757-200 with registration B-27015, departed Tao Yuan International Airport at 0841 Taipei local time, bound for Jeju International Airport, Korea. During descent from FL390 to FL310, approximately 99 nautical miles south of Jeju Island, the aircraft's Traffic Alert and Collision Avoidance System (TCAS) issued a Traffic Advisory (TA) and Resolution Advisory (RA) warning. The crew executed a descent maneuver in response to the TCAS RA 'DESCEND' warning. This event resulted in four passengers being seriously injured, ten passengers and six cabin crew sustaining minor injuries, and minor interior damage to the aircraft. The Aviation Safety Council (ASC) of the Republic of China conducted the investigation under the concurrence of the Korea Aviation & Railway Accident Investigation Board (KARAIB). The investigation team included members from the USA NTSB, KARAIB, Boeing Company, ROC Civil Aeronautical Administration (CAA), and Far Eastern Air Transport (FEA). The final report was published on August 15, 2008, following eight months of factual data collection. ## Key Findings Related to Probable Causes The investigation identified two primary findings related to the probable causes of the occurrence. First, Incheon Area Control Center (ICN) control made a non-standard call and gave a confusing instruction to EF306 during its descent when passing FL340. The EF306 flight crew did not fully comprehend the ATC instructions, failed to confirm them, and stopped descending at 33,800 feet. Both parties did not apply standard radiotelephony procedures and phraseologies, which contributed to the TCAS event between EF306 and TG659. Second, the EF306 flight crew did not complete the TCAS RA standard operation procedures and commenced an excessively high rate descent. The induced negative G-force resulted in the occupants' injuries. ## Risk Factors and Contributing Elements The investigation identified several risk factors that had the potential to degrade aviation safety. The EF306 flight crew did not adequately exhibit good Crew Resource Management (CRM) performance. The South Sector radar control (SSRC) momentarily missed monitoring the approaching situations between EF306 and TG659 while concentrating on radar identification of other aircraft. Approximately 20 seconds after stopping descent, the pilot of EF306 notified SSRC of climbing in accordance with TCAS instructions but actually descended. At that time, SSRC did not provide traffic information but attempted to modify the aircraft flight path instead, not complying with ATC TCAS operating procedures. The human capability of the South Sector radar control position could be limited when control services are performed by only one controller paying continuous attention to a large number of aircraft in a relatively broad service area, particularly during sudden abnormal situations. Applying Reduced Vertical Separation Minimum (RVSM) operations, air traffic on B576 to and from Jeju airport was increasing rapidly. Most injured passengers did not have their seat belts fastened and lost their protection while the fasten seat belt sign was still on. The cabin crewmembers did not provide timely injury information to the flight crew, which would have allowed the flight crew to request sufficient medical assistance before landing. The controllers were not aware of the importance of the number of injuries and the need for more ambulances to meet the flight upon landing, causing the necessary number of ambulances to arrive at the airport with delay. ## Other Findings The flight crew members were properly certified and qualified in accordance with applicable Civil Aviation Regulations. There was no evidence indicating that the flight crew members had any physical or psychological problems, nor any use of alcohol or drugs. The aircraft was operated within operational weight and balance limitations. There were no adverse weather conditions at the time of the occurrence. The TCAS response maneuver of TG659 flight crew met the standard operational procedures and requirements. The EF306 flight crew TCAS training materials met the CAA's training requirements. It may mislead the flight crew to have abrupt input to the aircraft while they speculate the relative distance according to visual contact of conflicting aircraft. SSRC and the controller at the Flight Data Control position held the qualifications required for the appropriate control position and the valid air physical examination certificates and did not take drugs or drink alcohol. The closest distance between EF306 and TG659 met the ICAO radar separation requirement but did not meet the minimum radar separation of 10 NM into an actual operation for a safer control. There was no standard instrument arrival procedure from B576 south of Jeju to Jeju airport. The data in the Flight Data Recorders of EF306 and TG659 aircraft were in accordance with ICAO Annex 6 Type 1 Flight Data Recorder, and satisfied to record 32 mandatory parameters. The 'seat belt sign' of EF306 was turned 'ON' at 02:03:05, and continued remaining 'ON' until the aircraft was parked in ramp. According to flight recorders of both the EF306 and TG659 aircraft, the TCAS TA/RA activations were recorded. The 'TA' activated at 02:06:48. At that time, EF306 was at an altitude of 34,052 feet, airspeed 272 knots, ground speed 493 knots, and magnetic heading 11.6 degrees. TG659 was at altitude 34,001 feet, airspeed 288 knots, ground speed 421 knots, and magnetic heading 219 degrees. Forty-nine seconds prior to the Closest Point of Approach (CPA), the relative distance, relative altitude, and closure rate of the two aircraft were 12.2 NM, 51 feet (altitude of EF306 was higher than that of TG659), and 910 knots, respectively. The autopilot of EF306 was disengaged at 02:06:56, at an altitude of 33,828 feet, airspeed 274 knots, ground speed 494 knots, and magnetic heading 11.6 degrees. With 41 seconds prior to CPA, the relative distance, relative altitude, and closure rate of the two aircraft were 10.05 NM, -171 feet (altitude of EF306 was lower than that of TG659), and 911 knots, respectively. The autopilot of TG659 was disengaged at 02:07:00, with altitude 33,999 feet, airspeed 288 knots, ground speed 421 knots, and magnetic heading 219 degrees. With 37 seconds prior to CPA, the relative distance, relative altitude, and closure rate of the two aircraft were 9.08 NM, -139 feet, and 910 knots, respectively. The 'RA' activated at 02:07:01. Thirty-five seconds prior to CPA, the relative distance, relative altitude, and closure rate of the two aircraft were 8.82 NM, -128 feet, and 910 knots, respectively. Twenty-nine seconds prior to CPA, the descent rate of EF306 was approaching to a maximum of 12,096 feet per minute. The relative distance, relative altitude, and closure rate of the two aircraft were 7.41 NM, -812 feet, and 893 knots, respectively. Twenty-four seconds prior to CPA, the 'RA Climb' of TG659 was released. The relative distance, relative altitude, and closure rate of the two aircraft were 6.13 NM, -1,880 feet, and 914 knots, respectively. At time 02:07:36 was the Closest Point of Approach (CPA).
