Explained: Why Delhi airport always fails to meet flight-handling demand

Even as it has three runways, Delhi's IGI airport barely manages to handle 73 air traffic movements during peak hours, against airlines' combined demand for 90

New Delhi’s Indira Gandhi International (IGI) airport, which has three operational runways, late last year clocked its peak record of handling 1,339 air traffic movements (ATMs) in a day. Even as this was significantly higher than its usual count, the number would seem rather unimpressive when compared with the 969 ATMs achieved a few days ago by the Mumbai airport, which has only one runway.

Why does Delhi handle so few ATMs in a day despite three runways? There certainly is no dearth of demand – the average consolidated demand from all airlines would require the airport to handle 90 ATMs in peak hours, against the 73 that it manages at present.

The problem for Delhi, it seems, lies in a number of factors. For one, though there are three runways, not all can operate simultaneously, thanks to operations complexities. Besides, some security issues and the nature of flights to and from the airport also pose some challenges that are unique to Delhi.

Simultaneous operations

The International Civil Aviation Organisation (ICAO) rules state that different aircraft operating on adjacent runaways must be separated by a minimum of 3 nautical miles at all times, unless some ‘mitigation measures’ have been put in place. In IGI’s case, the distance between the two runways used for arrivals is only 1.3 miles. This means there can be no parallel landing of planes on different runways at the same time – something that significantly reduces the overall capacity.

Also, the situation of two of the three runways – one used for arrival and the other for departure – is such that they converge at ends. This makes them operationally dependent on each other, and simultaneous arrival and departure of planes impossible.

Delhi International Airport Ltd (DIAL), the joint venture of GMR Group, Airports Authority of India (AAI), and Fraport AG operating the Delhi airport, and AAI are working together on putting in place the necessary ICAO-mandated ‘mitigation measures’ to facilitate simultaneous operations on the runways 10/28 and 11/29. These measures, used only at some of the world’s busiest airports, are designed for additional security to ensure safe parallel operations across runways.

Security concerns

The Delhi airport also has a large general aviation business – of smaller private planes – which accounts for three per cent of its daily ATM handling. However, the northernmost runway is barred from servicing such planes, thanks to VIP security restrictions. Since these planes do not follow a fixed schedule, they need to be accommodated on the other runways which adds more pressure on the capacity.

The airport also handles 50-55 ATR aircraft, the most for any airport in the country. These account for 7-8 per cent of its daily ATM handling. For these smaller aircraft, ICAO has stipulated a separation of up to 7 miles, if they are behind larger aircraft. This, too, exerts some pressure on the capacity.

Environmental concerns

Among its many problems, the Delhi airport is also constrained by the fact that it cannot operate one of its runways from 11 pm to 6 am every night. It is, in fact, the only airport that faces such a restriction, thanks to a National Green Tribunal (NGT) order around noise pollution menace.

Capacity vs timeliness

DIAL executives point out that there is always a conflict between pushing for capacity and on-time performance (OTP) of the airport. A balance has to be maintained. They claim that the Delhi airport, with an OTP of 79.5 per cent in October 2017, is far ahead of competing airports.

As for capacity, DIAL is putting in place a plan that includes investing in a fourth runway. According to company executives, the DIAL-AAI efforts to put in place the ICAO-mandated ‘mitigation measures’ will require writing of some new rules. Besides, this will be possible only after the air traffic controller (ATC) capacity at the airport is enhanced for allowing simultaneous landing. A new ATC tower is expected to be launched by the end of this year. DIAL expects this to help increase the ATM capacity by around 10 per cent to 80 an hour, and give the airport the capacity to handle 1,500-1,600 ATMs during peak times daily, compared with 1,320 at present.

The airport authorities are also considering taking some hard decisions, such as disallowing the landing of ATR planes during peak hours of morning and evenings. Besides, private aircraft operators might have to inform about their flight schedule three days in advance, so that they can be accommodated and the arrivals planned.

DIAL is also in talks with the defence ministry to put in place procedures for use of the airspace over Hindon. Nearly 50 per cent of the planes coming to the airport use this airspace. But since it is currently restricted for civil aviation flights, the landing of flights at the Delhi airport gets delayed.

The fourth proposed runway, expected to come up within three years, will substantially improve the airport’s ability to handle more flights – about a peak of 90 ATMs an hour or 1,800-1,900 a day. But in the interim, the airport is building rapid taxiways to reduce the time taken by an aircraft to exit a runway from 62 seconds to 50 seconds.

These measures and infrastructure development should help DIAL in enhancing its capacity and allow the handling of over 119 million passengers in a year, compared with 69 million at present.