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Managing the skies

India’s state-of-the-art Central Air Traffic Flow Management balances capacity against the demand to obtain optimum utilisation of airports, airspaces and aircraft

The beginning of the 21st century has marked a sustained growth of air traffic in India, registering a fivefold increase since the early 2000s.

During the last 15 years, aviation infrastructure in India has undergone significant augmentation in terms of airport capacity, ANS infrastructure, manpower addition and advanced technological adoption. Greenfield airports at Bengaluru, Hyderabad, Pokyong and Kannur; capacity augmentation of many airports; huge airport expansion in Delhi, Mumbai and Cochin have added significant ground infrastructure capacity. Nevertheless, the exponential growth in air traffic and demand for access at constrained airports regularly creates air traffic congestion.

Air Traffic Flow Management

At any given time, only one aircraft can land or depart from a runway and every aircraft must be separated with another aircraft or object by a certain distance or time to avoid collisions. Due to these factors, every airport or airspace sector has a finite capacity known as Aerodrome Capacity or Airspace Capacity. This capacity depends on many factors such as the number of runways available, the layout of taxi tracks, availability of air traffic control and current or anticipated weather. There are several variables that affect an Aerodrome Capacity such as bad weather, change in runway-in-use, runway configuration, VIP movement, bird activity, unforeseen situation such as missed approach, necessitating runway inspection and many more.

There are times when more arrivals occur than the airport can safely handle. When the air traffic demand reaches or exceeds the declared capacity, arriving aircraft are directed towards holding patterns where they circle until it is their turn to land. However, aircraft flying in circles is an inefficient and costly way of delaying aircraft, so it is preferable to keep them on the ground at their place of departure. This practice is known as Ground Delay which helps in saving a considerable amount of fuel.

The application of such regulations in order to balance capacity with air traffic demand is the function of ATFM unit. It is an activity that is done before flights take place. Sophisticated computers are used by ATFM to calculate exactly where an aircraft will be at any given moment and to predict when the demand of the airspace or airport is exceeding the declared capacity. This will help the ATFM managers to apply necessary regulations such as Ground Delay.

Each airport and air traffic control sector has a published maximum capacity, which when exceeded requires measures to reduce traffic. This is termed as regulation. The aim is to use capacity effectively, keeping the average delay as low as possible while ensuring that the capacity is not exceeded.

Towards a centralised system

Anticipating that India would need a nationwide air traffic flow management system with a network management principle, AAI initiated initial project consultations with Federal Aviation Administration (FAA) back in 2009. FAA appointed M/s, John A Volpe National Transportation Systems Center (Volpe Center), a reputed research organisation, as consultants in developing a detailed project report (DPR) for implementation of C-ATFM in India.

M/s Volpe Center interacted with the AAI core team of ATM and CNS experts, stakeholders such as airlines, airport operators, military, MET, etc., and submitted the ATFM Concept of Operations and a DPR on the implementation of ATFM in 2011. AAI internally formed a core team of CNS and ATM experts to study reports. The expert team interacted with various other experts from Eurocontrol, Australia and Japan over a period of time and adopted a modified DPR for the implementation of a Central ATFM in India. Following the procurement process, AAI floated a global tender in 2013 for Supply, Installation, Testing and Commissioning (SITC) of C-ATFM system in India. After the due process of technical and financial evaluation of the tender, M/S ATECH of Brazil was awarded the SITC of C-ATFM in 2015 at a cost of Rs 107 crores.

Since the construction of Central Command Center (CCC) at Vasant Kunj was yet to begin, the ATFM CCC and associated network systems were temporarily installed at the new ATC Complex, IGI Airport. Specialised Flow Management Position (FMP) systems were simultaneously installed at six metro airports, viz. Delhi, Mumbai, Bengaluru, Chennai, Kolkata and Hyderabad. The first phase of C-ATFM consisting of CCC and FMP at six major airports began operations from January 2017.

Since then, AAI has constructed a state-of-the-art C-ATFM complex at Vasant Kunj, New Delhi called the "Sky Flow". At a project cost of approximately Rs 80 crores, the new ATFM command centre is equipped with latest display screens and all necessary communication equipment. CCC began system validation and operations trial from the new premises in June 2019.

What is C-ATFM?

The C-ATFM system is primarily meant to address the balancing of capacity against the demand to achieve optimum utilisation of major resources, viz. airport, airspace and aircraft at every Indian airport having a capacity constraint.

The C-ATFM system integrates flight data from various subsystems, viz., ATC automation system and flight update messages. The system also displays weather information along with static information about airports, airspaces and air routes. The system processes the demand and capacity information and provides decision-making tools to the ATFM flow manager for collaborative decision-making to ensure the regulated flow of traffic in each airport in India.

The C-ATFM system is supported by 36 FMPs at various airports. Provided with FMPs, eight defence airports are also part of the ATFM network. CCC is the nodal centre for ATFM implementation in India and communicates with FMPs for implementation of different ATFM measures whenever necessary.

The ATFM process

The C-ATFM system stores all the approved flight schedules, airspace data, information about the airport and air navigation facilities. Through appropriate external interfaces, C-ATFM dynamically receives all updates of the flight data, information about any unserviceability of airport and equipment, airspace closures, special events such as VVIP movements and weather data.

Utilising the current information, C-ATFM builds a comprehensive picture of future demand and capacity scenario for all airports and airspace sectors. The national demand and capacity scenario is then published as an ATFM Daily Plan (ADP) by CCC, which provides an indication about expected air traffic congestions at all airports for the next day. This information helps airlines to plan their flights with more accurate estimates of delay and fuel requirement.

The CCC ATFM experts continuously analyse the air traffic demand and capacity information, updating the same with inputs from various airports for refining the predicted air traffic congestions for each airport.

When the air traffic demand is more than the capacity, traffic flow managers, in collaboration with airlines, ATC and airports, put in regulations to redistribute the air traffic so that the airborne congestion is reduced. This application of ATFM regulation is carried out with airlines in accordance with acceptable business rules.

Thus, the C-ATFM system enables optimum utilisation of major resources such as airports and airspaces, enhances air safety, saves fuel and reduces carbon footprint. It also provides data to the airport and airspace planners for carrying out gap analysis and strategically plan for augmentation of capacity.

The journey so far

Since the modest beginning of operations limited to six metro airports in January 2017, C-ATFM operations have grown to encompass the monitoring of air traffic scenario over the entire Indian airspace and airports across the country. Some of the significant events handled by CCC are:

Airspace closures for Republic Day Parade and air traffic regulation thereafter at Delhi in 2018/2019

Airspace closure at Bengaluru airport for Bengaluru Air show and air traffic regulation thereafter 2017/2019

Major Runway closure at Delhi (2018), Mumbai (2017/2018/2019) and air traffic regulation thereafter

Monitoring of air traffic flow and providing assistance to ATC due to Cyclones at the Bay of Bengal

Pakistan Airspace closure assistance to Mumbai ATC

Significant bad weather (Fog, Dust storms, Thunderstorms) at major airports and air traffic recovery assistance thereafter at Delhi, Mumbai, Kolkata, Bengaluru, etc.

C-ATFM works on the principle of collaborative decision making (CDM). Over the last two years, AAI has conducted several interactive seminars, meetings and presentations to create awareness of C-ATFM concepts across the nation with participation from stakeholders such as DGCA, Airlines, Airport Operators, Military Officers and GA operators. AAI has followed the process of consultation by conducting seven stakeholders' meetings at regular intervals so far.

In order to assess the impact of early departures from field stations to the congested airports, two-phased trial operations were conducted in October and November 2018. Operations were monitored by CCC and the flight data thereby collected were analysed by the ATFM team. Results were presented to Secretary, MOCA by ATFM directorate in the stakeholders' meeting in January 2019. The exercise helped in identifying one of the main cause of congestion. Suitable measures are being initiated to stop early departures/arrivals to reduce congestion in the air–reducing fuel burn and carbon footprint in the process.

India (AAI) was also invited by ICAO Mid East office to participate as a core team member for developing ATFM concept of operations in Mid East Region and prepare a roadmap for implementation and they are actively contributing to the same. Indian ATFM experts are assisting Nepal to develop a national ATFM concept of operations.

(This article is authored by Airports Authority of India)

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