MIT engineers develop new aircraft queuing model

A new aircraft queuing model, developed by two engineers at MIT including an alumna of IIT Madras, claims to not only bring down the pressure on the over-stressed air traffic control officers but also make airlines operations cost-effective if accepted by the aviation industry.
The reserachers claim that the aircraft queuing model, based on a study carried out after analysing departure operations at the three major US airports--John F Kennedy, Newark Liberty, and Philadelphia International Airport-- predicts how long a plane will wait before takeoff, given weather conditions, runway traffic, and incoming and outgoing flight schedules.
The study conducted by Hamsa Balakrishnan, an associate professor of aeronautics and astronautics and engineering systems at MIT, in association with a former graduate student Ioannis Simaiakis has been published in the journal Transportation Science.

It assumes significance for India where airports such as New Delhi, which handle bulk of the air traffic, often face acute shortage of Air Traffic Control Officers (ATCO).
On an average, the ATCOs at Delhi airport handles around 1,050 arrivals and departures per day while those at Mumbai over 800 flights every day.
Government had last year said that there were nearly 1,600 posts of air traffic controllers lying vacant at different airports in the country while acknowledging that ATCOs are at times under stress at airports having high density operations but suitable measures are in place to address such situations.

"The model may help air traffic controllers' direct departures more efficiently, minimising runway congestion. For example, if a controller knows that a plane is unlikely to take off for half an hour, he may choose to keep the plane at the gate to avoid contributing to runway backups," the study paper said.

"In our field tests, we showed that there were some
periods of time when you could decrease your taxi time by 20 per cent by holding aircraft back," Balakrishnan says.
"Each gate-held aircraft saves 16 to 20 gallons of fuel, because it's not idling. And that adds up," she said in the study paper.

To prevent extended runway queues, Balakrishnan and Simaiakis developed a model, consisting of two modules, to predict taxiing time.
The first module calculates a plane's travel time from the gate to the departure runway, taking into account any interactions with other arriving and departing flights while the second module estimates an individual runway's queuing delay - the time it takes for a plane to take off after joining the queue for takeoff.
Balakrishnan, who completed her B.Tech degree from IIT Madras in 200, said that individual decisions on when planes push back from gates can contribute to the problem.
"It's mostly on the fly. Sometimes, if there is a controller with a lot of experience or intuition, they might actually decide they'll hold aircraft back," she said.

Balakrishnan and Simaiakis tested the model using data from the Federal Aviation Administration's (FAA) Aviation System Performance Metrics database, which contains pushback times and takeoff times for every flight departing from 77 major US airports.
Balakrishnan said the queuing model gives air traffic controllers accurate predictions of what airport congestion would look like if they took certain actions, such as continuously pushing planes back from the gate.
Controllers can then use these predictions to adjust their pushback times to avoid runway backup, she said.