An accident involving three aeroplanes could be prevented by automatically sent warnings (TCAS) and by the intervention of air traffic control. The Indian Aircraft Accident Investigation Bureau (AAIB) has launched an investigation.
The incident took place on Sunday 23 December. Above Delhi, a Boeing 747-400F (N919CA) from U.S.-based National Airlines Cargo operating flight NCR840 between Bagram (Afghanistan) and Hong Kong flew at an altitude of 31,000 feet. The automatic warning system (TCAS1) went on when the aircraft came close to a Boeing 777-300ER (B-16716) from the Taiwanese EVA Air flying at an altitude of 32,000 feet en-route from Taipei and Bangkok to Vienna on flight BR061.
Both aircraft rose to a new altitude, with the effect that also a KLM Boeing 777-300ER aircraft (PH-BVB) that was operating flight KL875 to Bangkok at 33,000 feet was in danger, according to Indian media. Air traffic control intervened and ordered the plane from National Airlines not to rise further and turn left, after which the three aircraft could safely continue their flight.
KLM said this Sunday to news agency ANP that its own aircraft has never been in danger. “It’s about an incident between two planes,” said a spokeswoman. “Contrarily to national and international reporting, flight KL875 to Bangkok is NOT involved in the near collision over India. KL875 was flying nearby, but safety has not been compromised,” KLM wrote in a statement.
The incident happened in the Delhi Flight Information Region (FIR). An FIR refers to a specified airspace where flight information and alerting services are provided.
1 A traffic collision avoidance system (TCAS) is an aircraft collision avoidance system designed to reduce the incidence of mid-air collisions between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of mid-air collision (MAC). It is a type of airborne collision avoidance system mandated by the International Civil Aviation Organization (ICAO) to be fitted to all aircraft with a maximum take-off mass (MTOM) of over 5,700 kg or authorized to carry more than 19 passengers.
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