Delhi airport has advanced tech for low-visibility landings. So why does fog still disrupt flights?

The Indira Gandhi International Airport in Delhi, the country’s busiest airport, is fitted with an advanced system that allows aircraft to land in low visibility. Despite this, the winter months each year – December and January in particular – are marked by flight delays and disruptions, owing to the fog that envelops parts of North India in this season.

On December 8, a day after 362 flights arriving and departing from the Delhi airport were delayed and 38 cancelled, the Directorate General of Civil Aviation directed domestic airlines to adhere to its advisory on operating aircraft in low visibility.

The advisory includes directions for close monitoring and rescheduling of flights keeping visibility conditions in mind and deploying pilots trained in the CAT IIIB instrument landing system, which allows aircraft to land even when visibility is down to 50 metres.

In an email to domestic airlines, the civil aviation regulator said: “Today, IGI Airport again experienced a spell of fog when the duration of LVP [low visibility procedures] was for 15 hours and 26 minutes. However, at no stage RVR [runway visual range] on both the runways had gone below 125 meters.”

On December 7, of the total delays and cancellations, 197 were for arrivals. This happened just a day after the Delhi International Airport Limited reportedly said the IGI airport is fully prepared to handle flight operations during dense fog. However, since the first week of December, there have been delays and cancellations almost every day.

Advanced system

An instrument landing system uses radio signals to guide aircraft to land when pilots cannot see the runway. The CAT IIIB system – short for category three – is among the most advanced and three runways at the Delhi airport are equipped with it. The only other airports in India with this system are Lucknow and Jaipur, which implemented it this month.

This technology is only surpassed by the CAT IIIC system, which allows landing in near-zero visibility. A DGCA official who did not wish to be named said CAT IIIC is three to four times more expensive to operate than CAT IIIB and just a handful of airports in the world, including the JFK in New York and London’s Heathrow, are equipped with it.

Despite this, flight disruptions are a regular feature in the Delhi winter, when dense fog conditions last for about 20-odd days in December and January.

One reason for this is that all pilots are not familiar with the system. “Not all pilots flying domestic airplanes are trained to land on the CAT IIIB system,” said VP Agrawal, former chairman of Airport Authority of India. “Presently, the DGCA is very strict about pilot training with regard to CAT IIIB system, but some domestic airlines tend to avoid this. It is an expensive affair too as the training can cost nearly Rs 10 lakh per pilot.”

Another reason for delays, Agrawal said, is that during dense fog, the landing process takes longer, so fewer aircraft can land on a runway in a given period. Executive Director (retired) Air India Jitender Bhargava said that for the CAT IIIB system to work to its capacity, three factors have to be considered – training of pilots and co-pilots on the system, cockpit (aircraft) compliance and airport compliance.

“The IGI Airport in Delhi has in place a CAT IIIB system and most flights at present are CAT IIIB compliant too,” he said. “It [training] should be made mandatory at least for all pilots flying in the northern belt, which is worst affected by fog at this time of the year. It is high time that the DGCA should get stricter with pilot training with regard to the same.”

Bhargava said the delay and cancellations at one airport – especially one as arterial as Delhi – has a cascading effect on operations across the country. So, if a flight has to go from Delhi to Hyderabad and onward to Chennai, any delay at the IGI airport would affect operations in the other two cities as well. “No matter what the cost of training a pilot in CAT IIIB is, the airlines have to keep their customers in priority and bear the price,” he added.

Landing trouble

But insufficient pilot training is only one reason why the Delhi airport is yet to reap the benefits of the CAT IIIB system even 12 years after it was tested. The fact that few other airports have implemented this system also impacts operations in Delhi. For example, if an incoming flight to Delhi is delayed at the airport where it originates from because that is not CAT IIIB compliant, there is little that authorities in the national capital can do. Similarly, a flight from Delhi bound for a destination with low-visibility may have to delay take-off if that airport is not compliant with the system.

“What if a flight which was to arrive from Amritsar or depart for the city gets delayed because of fog in Amritsar, which does not have CAT IIIB system installed in the airport?” said a senior DGCA officer who did not wish to be identified.

Because of this, the DGCA, in its directive to airlines, said all non-CAT IIIB compliant aircraft should arrive at or depart from IGI Airport only between 10 am and 8 pm – when visibility is not a big issue – while only CAT IIIB compliant aircraft with qualified crew should be scheduled in the early mornings and at night.

“The problem caused by coordination pertaining to CAT III system compliance among airports can only be reduced through proper management in terms of flight scheduling,” the DGCA official said.

On December 8, Airport Authority of India said that Jaipur and Lucknow airports were being upgraded to CAT IIIB. Last year, reports said that the government was planning to implement the system in 13 airports, including Patna, Chandigarh and Amritsar.

So why is it taking so long for the system to be implemented in more Indian airports? Former Airports Authority of India chairman Agrawal said that the system is expensive and aircraft in the country need time to comply with it.

“CAT IIIB is undeniably an expensive affair,” added Agrawal. “Initial cost of the CAT IIIB system in an airport is up to Rs 10 crore and the recurring cost can reach around Rs 50 lakh a month, mainly incurred on maintenance.”