Alarm triggers Chennai-bound Jet flight to descend 200 feet after takeoff

A Jet Airways Delhi-Chennai plane had to descend 200 feet after take off from Delhi airport on Tuesday after an automatically generated alarm in the cockpit warned the pilots about the presence of traffic nearby.

The incident comes days after two IndiGo aircraft averted a near-collision in Bangalore airspace after a similar alarm.

In Tuesday’s incident, however, it was not clear what caused the alarm as there was no traffic near the Jet Airways aircraft.

The Directorate General of Civil Aviation (DGCA) has initiated a probe to investigate what triggered the TCAS alarm.

TCAS or traffic collision avoidance system monitors the airspace around a plane for other aircraft equipped with corresponding active transponders and gives pilots warning of possible collision risks.

“The crew of Jet Airways flight 9W 759 from Delhi to Chennai of July 24, 2018, executed a safety manoeuvre as per the guidance of the on-board Traffic Alert and Collision Avoidance System (TCAS), which was triggered post the flight’s take off from Delhi,” confirmed a spokesperson of Jet airways.

According to an official of DGCA, the Jet Airways flight descended from 2,200 feet to 2,000 feet and continued its journey thereafter.

“In the absence of traffic and in line with the instructions of the ATC, the B737 aircraft with 156 passengers and 7 crew members continued its journey, landing safely at Chennai. Jet Airways will follow the regulatory obligations and extend full support as always. Safety of guests, crew and assets is of paramount importance at Jet Airways,” the spokesperson added.

Another DGCA official said that such TCAS-RA is not common and detailed investigation will reveal the object due to which alarm was triggered.

“Sometimes while aircraft is taking off at a busy airport, such alert is generated due to its proximity to another aircraft on ground. DGCA’s investigation will find out whether another aircraft did not report a similar alarm deliberately or some technical error caused the alarm,” said the official.

According to DGCA, the pilot has to respond immediately to the warning by disengaging the auto pilot and commencing a climb/ descent manoeuvre as called for.

“They should not let visual sighting reverse the TCAS instructions. If pilots simultaneously receive conflicting instructions from ATC and TCAS, then the pilots should follow the TCAS instruction,” the DGCA official said.