Airport Activity Module

The Flight Routing & Scheduling Model generates aircraft trips according to segmented passenger and freight flows. Based upon the passenger and freight flows coming from the Air Transport Demand Module, this model outputs aircraft trips, in the form of a flight schedule, to the Aircraft Movement Module and to an internal LTO Operations Model. Aircraft classes used are also output to the Aircraft Technology & Cost Module, which returns costs and emissions (the latter to the internal LTO Operations Model). The generation of the schedule includes identification of aircraft sizes, flight frequencies, departure times, and passenger load factors, by flight segment. These factors are modelled as a function of passenger and freight demand, segment length, and in future developments of the model, average delay (from an internal Delay Calculator) and aircraft cost (from the Aircraft Technology & Cost Module) to capture airline response behaviour. These relations are derived from current and historic schedules, demand data, load factors, delays, and aircraft class and size statistics.

Alternatively to the Scaled Routing Model in the Air Transport Demand Module, the Flight Routing & Scheduling Model also simulates the airline response to capacity constraints. By maximizing airline profits, i.e., the aggregate difference between airline revenues and costs for each possible flight segment, a linear optimization routine allocates passengers to various routes in different periods of the day, subject to the available aircraft fleet. This model will reproduce the global routing structure in the base year and endogenously adjusts the routing structure to capacity constraints, eventually resulting in a changing air traffic network over time. The formulation of this model has just begun and first tests based upon a limited set of airports are promising.

The internal LTO Operations Model includes two functions: modelling aircraft ground operations; and modelling landing and take-off operations. The outputs of these models are LTO path, taxi and flight times, and emissions (calculated relative to emissions by class input from the Aircraft Technology & Cost Module), which are direct inputs to the Local Air Quality Module. The modelling of ground operations includes simulating taxi demand and unimpeded taxi times. Taxi demand is defined by the flight schedule input from the Flight Routing & Scheduling Model, and airborne delay input from the Aircraft Movement Module. Unimpeded taxi times are obtained directly from data for airports in some regions (e.g. US, EU), whilst parametric modelling based on other airport characteristics is required for those regions for which it is not available.

*Courtesy: Univ of Cambridge


The latest on NextGen – Memphis

Nobody likes a traffic jam, including owners of jets loaded with people or packages that fly in or out of Memphis International Airport every 90 or so seconds.

Waiting at the end of the runway or in an airborne holding pattern is bad for business and the environment.

It’s one reason Memphis airport super-users FedEx and Delta jumped on board the Federal Aviation Administration’s NextGen program to modernize the air traffic control system.

Industry officials say the federal program to create a new air traffic control system is at a crossroads, making delays possible. ASSOCIATED PRESS FILES

Industry officials say the federal program to create a new air traffic control system is at a crossroads, making delays possible.

They’ve helped make Memphis a proving ground in early initiatives to implement the Next Generation Air Transportation System, which involves switching to satellite-based technologies from a 75-year-old radar-based system.

The finish line is still 14 years out, but FAA officials say the new system will ultimately make air travel safer and more reliable. It will enable planes to fly more directly from Point A to Point B with less wasted motion, by feeding controllers, flight crews, airlines and airport operators better information on what’s going on in the airspace.

Under NextGen, planes would no longer have to fly indirect routes to stay within range of ground radar stations. Planes would continually broadcast exact global positioning system readings, providing data for cockpit displays showing a plane’s relative position to other planes and those planes’ flight paths.

Although the Memphis-Shelby County Airport Authority has no direct involvement in NextGen, airport officials consider it vitally important to the future of the world’s second largest cargo airport and, on the passenger side, a Delta hub.

“If you enhance the technology on the ground and in the air, you can certainly increase the capacity of the system,” said airport executive vice president Scott Brockman. “If the system gets a benefit, clearly the airport gets a benefit. It’s an all-for-one type of scenario.”

FedEx spokesman Jim McCluskey said, “We are supportive of NextGen because it’s a harmonized air traffic system. It’s a coordinated blend of equipment, policy and procedures. It does allow more operations to coexist in the same air space, increasing safety and providing the airlines with the most optimal routing. All this leads to savings, if you look at time and fuel, and it helps make the aviation system greener.”

McCluskey added that in FedEx’s view, “One critical thing is that the FAA delivers a system that is useful to the airlines and that is developed in a cost-effective and expeditious way.”

An Associated Press report described NextGen as a program at a crossroads because of tight federal and airline budgets.

The tab for NextGen is estimated at as much as $22 billion for the government and another $20 billion for the airline industry through 2025. The House wants to reduce FAA’s budget authority by $1 billion a year over the next four years, while the Senate has favored higher funding.

FAA spokeswoman Kathleen Bergen said Memphis has already sampled a handful of NextGen initiatives. They include an effort to more evenly space jets awaiting departure, called collaborative departure queue management or CDQM; testing of ground-based GPS receivers that more accurately pinpoint locations of approaching aircraft; and implementation of satellite-based navigation for arriving flights that are properly equipped.

The airport will add satellite-based navigation for departing flights by February and introduce an enhanced technology guiding descent of arriving jets by next July, Bergen said.

The latter improvement, known as Optimized Profile Descent, is billed as a big fuel-saver because it allows planes to make a continuous descent at lower engine speeds, rather than descending in stairstep fashion.

The newly commissioned Memphis Tower was designed before NextGen began, Bergen said, but the tower and associated radar facility can handle any new NextGen initiatives.

The 336-foot-tall tower includes the latest airport surface detection equipment, a ground radar system that tracks planes and vehicles on the airfield. The antenna atop the tower provides dramatically better field coverage.

The FAA tried out collaborative departure queue management at Memphis with FedEx and Delta and concluded it had the potential to chop 5,000 hours a year off taxiing times between gates and runways. Rather than manually keeping track of paper strips listing planes awaiting takeoff, controllers shared airfield surveillance data electronically and used computers and software to space departures during peak times.

Bergen said the queue management system was suspended for 90 days because of the FAA’s switchover from old tower to new tower June 20, but it will return in August.

The FAA estimates NextGen will reduce total flight and ground delays by 35 percent and provide $23 billion in benefits through 2018, saving 1.4 billion gallons of aviation fuel and reducing carbon dioxide emissions by 14 million tons.

The agency says bigger system capacity is critical if U.S. passenger volume grows as predicted, from an estimated 737 million this year to more than 1 billion a year in the next decade.

iFLEX – From Fixed to Flex Routes

Most of the next generation Air Traffic Management (ATM) initiatives like Next Gen and SESAR are set to minimize delays and increase capacity both on the ground and in the airspace. One cornerstone of these projects is trajectory optimization. The gate-to-gate optimization concept where a flight is transported from end to end using state-of-the-art technology and much more direct routes.

The problem with this ideology is that a very large constraint already exists within the airspace. The presence of airways and waypoints not only limits opportunity for optimization, but also results in airspace saturation. Most of the airways are created specifically for a particular city-pair due to high demands, but 10 years later the airlines don’t fly that route anymore and the airways remain. Many such airways and waypoints exist in today’s aeronautical infrastructure that are rarely or never used.

This brings an interesting discussion forward. If there were no airways, would there be better scope for optimization. Yes. But it would be at a higher risk level. Hence, in low density airspace, where there are very few aircrafts flying per day, such a concept can be utilized to its potential. The International Air Transport Association (IATA) has launched an initiative called iFLEX, which will enable aircraft to fly a more flexible trajectory from origin to destination. The optimization process begins at the Flight Planning phase, where the dispatcher identifies the optimum combination of airways, waypoints, significant points, VORs, etc taking advantage of the upper winds. Modern flight planning systems are very sophisticated and can calculate the time, fuel consumption, CO2 burn, payload impacts, overflight charges for a particular route on a particular day. No re-optimization is envisioned enroute and the ATC separation standards will remains the same.

Being a part of the iFLEX team at IATA, I must say this is a very compelling concept that could change the very nature of air transportation. Together with support from ICAO, Delta Airlines and Emirates Airlines, the agenda for 2011 includes conducting 3 workshops, demo flights and publication of the guidance material to implement flexible routings.

More information on iFLEX can be found here.