Near collision of Vistara, Jet planes, ministry launches probe

The Ministry of Civil Aviation has launched a probe into what could have been a major accident in the Delhi skies when the distance between two aircraft was reduced to just 400 feet.

On April 21, the Jet Airways flight 9W 597 was scheduled to land at Indira Gandhi International Airport here but it decided to abort the landing.

As a result, the distance between it and the Vistara flight UK 811, which had been okayed for take-off, reduced to less than required, triggering a warning in the cockpits of the aircraft to maintain a safe distance.

There were 148 passengers on-board the Vistara Airbus A320 aircraft, which was bound for Bengaluru, while Jet Airways Boeing 737 was coming here from Muscat with 174 people on board, a source said.

The incident is being investigated by the Civil Aviation Ministry's apex probe body -- Aircraft Accident Investigation Bureau (AAIB), the source said.

According to the source, Jet Airways flight 9W 597, was flying at a much higher speed than was required for the landing. However, the Delhi ATC cleared it for landing after its flight crew said it will "slow down".

At the same time, the ATC okayed the Vistara flight's takeoff from the runway where the said Jet Airways aircraft had to land.

However, the Jet Airways plane aborted the landing due to its "high speed," and opted for a go-around, the source said.

At this stage, both the Vistara and the Jet Airways flight were taking off almost simultaneously, with the vertical separation between the two aircraft was just around 400 feet.

"This triggered a Resolution Advisory (RA) by the Traffic Collision Avoidance System (TCAS), which averted the possible collision between the two aircraft," the source said.

The TCAS is an on board equipment that advises pilots about traffic in the proximity of the aircraft and also prescribes what action the pilots can take to maintain desired separation between the aircraft.

Both the Vistara and the Jet Airways confirmed the incident.

Defending its pilot's decision to abort the landing at the last minute, a Jet Airways spokesperson said it was done to attain the "desired approach and landing."

The spokesperson in a statement termed the decision as "in the interest of safety".

The Jet Airways also said "during the execution of the manoeuvre, another aircraft was aligned for departure on the same runway and as their activation envelope overlapped, the on board automatic traffic alert and collision avoidance system issued appropriate guidance to keep both the aircraft at a safe distance from each other."

"The flight crew followed the guidance and landed safely," the airline said.

The matter has been reported to the regulatory authorities besides an internal investigation into the incident is also being carried out, it added.

When contacted, the Vistara spokesperson said its aircraft took off only after it had the required permission form the ATC and that the airline followed all the procedures correctly.

"We have offered our full support to the relevant authorities in their investigation and hope the occurrence of such incidents can be reduced going forward," the spokesperson told PTI.