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Red alert: Why a disaster is waiting to happen in Indian skies

India’s civil aviation regulator found that 71 of the 129 potential collisions between 2011 and May this year were because of ATC glitches.

india Updated: Aug 22, 2016 11:33 IST
Jeevan Prakash Sharma, Hindustan Times
Mid-air collisions,Aviation,Aircraft
India’s civil aviation regulator found that 71 of the 129 potential mid-air collisions between 2011 and May this year were because of ATC glitches.(Representative image/Shutterstock)

On September 2, 2013, at Delhi’s Indira Gandhi International airport, a mid-air disaster was just seconds away. In the span of 50 seconds between 08:53:22 am and 08:54:12 am, a SpiceJet and an Indigo flight, with a total of nearly 300 people on board, narrowly missed a collision, not once or twice, but thrice.

The confusion started when Air Traffic Control (ATC) allowed the SpiceJet flight SEJ234 to land on Runway No. 28 from where the Indigo aircraft IGO286 was about to take off.

From there, the situation rapidly hurtled towards a catastrophe, aided by wrong instructions from the ATC.

The first collision was averted when the two planes were just 50 feet apart —the Spicejet plane was descending for a landing and the Indigo aircraft was about to take off. No instruction from ATC, Spicejet aborted landing and started climbing.

But more danger was in store. The Indigo flight took off and both planes ascended parallel to each other, converging at a point when they were at the same height and just 300 feet apart laterally. The pilots realised the risk and the Spicejet plane flew underneath the other.

But with the ATC offering little help, a third near miss was in store. The new course set both planes on a collision course that was prevented by an in-built anti-collision system on both aircraft.

This was the narrowest escape since the world’s worst mid-air collision in November 1996, when a Saudi and a Kazakh plane crashed into each other above Charkhi Dadri near Delhi, killing all 349 people on board.

A Directorate General of Civil Aviation (DGCA) probe concluded that confusion over the handover and takeover between two ATC instructors was the main reason for the September 2, 2013 incident, an HT investigation has found.

This wasn’t the only case of ATC error. On May 8, 2014 a Jet Airways and an Indigo flight had a similar near miss situation in Mumbai due to poor ATC planning.

India’s civil aviation regulator found that 71 of the 129 potential collisions between 2011 and May this year were because of ATC glitches.

These included misjudgment by the controller, inadvertent clearance issued by the controller, loss of situational awareness by the controller and poor planning by the controller – all of which contributed to the risking of thousands of passengers’ lives.

A glaring example of poor air safety is right here in Delhi, where a new air traffic control tower at the Indira Gandhi International airport is yet to operationalise. “It has missed many deadlines and there is no update on when it will be ready and operational. ATC is not well-equipped to handle the air traffic situation,” says a senior official from the Air Navigation Services under the Airports Authority of India (AAI).

The Airports Authority of India, which controls the ATC and the airlines mentioned in the story, did not respond to HT queries.

All it takes is 40 seconds

The DGCA defines a near miss or an airprox (aircraft proximity) as a situation where the distance between aircraft as well as their relative positions and speeds may have comprised the safety of the planes.

The AAI official said near miss occurs when aircraft are separated by less than 1,000 feet of vertical distance or 5-25 nautical miles (30,000- 150,000 feet) of horizontal distance.

An HT investigation of a near miss on May 7 this year, based on data from, the world’s largest flight-tracking data company, shows how technology played a part in averting the collision.

India’s skies have been kept safe for the past few decades by a technology called the Traffic Collision Avoidance System (TCAS) that was made mandatory after the Charkhi-Dadri incident.

The TCAS radio signal creates an electronic shield around a flight. If two shields overlap, TCAS alerts both pilots.

If an airprox situation arises, TCAS first gives them a traffic advisory (TA). In other words, if one aircraft is 40 seconds away from another aircraft, vertically or horizontally, TCAS indicates a possible threat.

But if the violations continue and time gap reduces to 25 seconds, the TCAS instructs one flight to “climb” while other one to “descend” till the violation is removed.

If the ATC and TCAS instructions contradict each other, pilots are instructed to follow the TCAS – a practice made mandatory after the Uberlingen mid-air collision in Germany in 2002 where 70 people died.

ATCs face staff crunch

A former DGCA official says a rise in near misses over the past few years is due to increasing air traffic, but data doesn’t support his claim. Traffic increased just 17% this year but potential collisions rose by 78%.

A more plausible reason is the severe shortage of traffic controllers in ATC operations in India, say civil aviation ministry sources. The ATC — which organises the flow of air traffic to prevent collision — is functioning without a quarter of its sanctioned strength.

There’s a shortage of 1,000 air traffic controllers, as revealed by a 2014 audit by International Civil Aviation Organisation (a UN agency that guides aviation norms), according to a senior manager in Air Traffic Control Operations. One area controller shouldn’t handle more than 15 aircraft at a time, but he is doing twice that. An area controller monitors aircraft at cruising speed.

Sources in the ATC reveal that no controller was recruited between 2012 and 2015. At the same time, the number of aircraft departures rose from 647,863 to 789,260.

A shortage of controllers was one of the reasons why the United States Federal Aviation Administration (FAA) downgraded India’s aviation safety ratings in January 2014.

“The shortage of ATCs compromises with the safety of thousands of flyers every day. We are waiting for a disaster to act,” says SS Panesar, who headed the flight safety and training divisions at Indian Airlines.

Few takers

The stress inside an ATC was best captured in the 1999 John Cusack movie Pushing Tin. An ATC source involved with recruitment says this year, 3,000 people applied for an air controller’s job and 400 were selected. “90 out of them refused to join.” The high stress and poor pay discouraged talented candidates, he adds.

A senior AAI official privy to pan-India ATC operations worries that the 310 fresh recruits will take seven years to become full-fledged area controllers.

“We have only 400 area controllers who work in shifts to monitor more than 2,000 flights daily. The more we delay in hiring them, the more time they will take to elevate to important positions,” he says.

Former executive director of AAI air operations, Gurucharan Bhatura, who was a part of an investigation into the 2010 Mangalore air crash, told HT that the government should recruit retired technical staff from the air force to tide over the crunch.

ATC lacks modernisation

But a lack of manpower isn’t the only reason for the appalling air safety record. Sources say few modern equipment and poor maintenance of existing infrastructure at ATC towers in major hubs such as Delhi, Mumbai, Chennai and Kolkata contribute to the rising potential collisions.

The second AAI official said an integrated radar system — supplying continuous and seamless images of aircraft from its take-off to landing anywhere in India — failed twice in the past six months, first in Kolkata and then Nagpur.

This failure means flights can go off the ATC radar in areas beyond the limit of a particular radar located in an airport.

For communicating with aircraft, the ATC uses high-frequency signals — which aren’t often audible to pilots — and officials say extended very-high frequency signals is the need of the hour for error-free communication of directions and instructions.

Read| Mid-air near misses rise to a new, dangerous high

First Published: Aug 22, 2016 01:02 IST