NEW DELHI: The alertness of Delhi air traffic control (ATC) and pilots operating a SWISS flight to IGIA late Sunday (July 6) saved the day when another aircraft ahead of the European airliner first slowed down in air and then didn’t vacate the runway from the first available rapid exit taxiway. As a result, the spacing between the two arriving aircraft in air reduced from the four nautical miles that was being maintained by ATC at that time and then the other plane was on the runway for 25-30 seconds longer than it should have. The ATC asked pilots of the SWISS Airbus A330 to go around when it was at an altitude of about 1,400 feet and it then landed safely in the second attempt.This happened after 11.40 pm on Sunday when SWISS LX 146 was flying in from Zurich and an Indian carrier’s A320 from Phuket was ahead of it in the sequence of landing. According to senior ATC officials, the aircraft flying in from Phuket was “four nautical miles (NM) from touchdown on runway 11R and LX 146 behind it was about eight NM from touchdown. The other aircraft reduced speed on final approach. Subsequently, Swiss was also asked to reduce speed to minimum speed by the approach controller.”ATC asked the SWISS flight to “continue approach” because even this slightly reduced horizontal separation would have been enough for it to land had the other plane landed and vacated runway 11R using the first rapid exit taxiway. Made at 120 degrees to the runway, this alignment of the Y1 rapid exit taxiway would have made it possible for the aircraft to vacate the runway on landing roll itself and then LX 146 touching down.“After landing, tower controller (ATC) asked pilot of the other plane to vacate the runway via rapid exit taxiway Y1. But the pilot informed that the aircraft will vacate the runway by Y2, which is further down the runway and farther away from Y1. This resulted in increased runway occupancy time by 25-30 seconds,” said the official. Since this flight could not vacate the runway in time, the tower controller asked the SWISS flight to “go around” or carry out a missed approach for “safety reasons.” Flight tracking sites show the Lufthansa group airliner did so when it was at an altitude of 1,400 feet. It landed safely in its second attempt at 11.51 pm, as per flight tracking sites.At that time, Delhi was witnessing easterly winds — which is a common during monsoon. IGIA’s main runway 10/28 has been closed for repairs since June 15. With three operational runways (minus 10/28) and easterly winds, Delhi can handle a maximum of up to 32 arrivals in an hour. While learning from the fiasco earlier this summer, number of flights has been cut at Delhi. Still ATC and pilots have to be extra careful to operate in circumstances to maximise aircraft movement. “We are operating amid a shortage of experienced manpower. Whether it is Delhi or Mumbai, the crunch situation leaves low margin for error. An aircraft slowing down or taking longer than anticipated to vacate the runway, means quick decisions in real time to ensure safety,” said multiple air traffic controllers.
