Clear the Airways

31 August 2008 (Last Updated August 31st, 2008 18:30)

David Behrens has his ear to the ground on the ongoing challenge for airports to reduce their environmental emissions.

Clear the Airways

Many of the environmental inefficiencies in the air traffic system today stem from inadequate airport infrastructure. While the obvious contributing factors may be insufficient runways, taxiways, aprons and gates, it's also the passenger flow 'choke points' at the terminal – such as queues for passenger check in, security and immigration – that can cripple efficiency and adversely affect aircraft operations even hours away from their destination airport.

In many places the problem is serious and growing. Europe and the United States are facing serious airport challenges. In Europe there are predictions that 75% of airports have no chance of building new runways in the next 20 years. By 2025, more than 60 European airports will be congested and the top 20 airports will be saturated at least eight to ten hours a day. In the US airport capacity is a continuous concern. In its operational evolution partnership (OEP) programme, the US Federal Aviation Administration (FAA) has identified 35 airports for infrastructure improvements. Nevertheless, even if the OEP projects go forward as planned, six airports will run out of required capacity by 2015 and 14 by 2025.

Much of this problem stems from inadequate land, improper zoning of tall buildings by city planners and airport limitations such as outdated terminals and runway configurations, insufficient taxiways, aprons and gates – all of which have an environmental impact on the airport air quality.

At many of these airports, lobbyists use environmental arguments to prohibit much needed infrastructure improvements. Regrettably, efforts by lobbyists to curb infrastructure improvements are often counterproductive to the environmental mission they represent – as an airport with inefficient infrastructure only exacerbates fuel and energy wastage.

Internal affairs

The design, layout and procedures inside an airport terminal directly affect the CO2 emissions of the airport environment. Inefficient passenger flows from ineffective check-in counters, security screening, customs and immigration and gate-to-gate passenger movement all contribute to delays.

Passenger delays to the gate add unnecessary time to the airline's turnaround, which in turn means the gate will not be vacated in time for the next arriving flight. Arriving aircraft have to wait with engines and auxiliary power units running, resulting in wasted fuel, wasted time and unnecessary CO2 emissions.

"By 2025, more that 60 European airports will be congested and the top 20 will be saturated at least eight to ten hours a day."

Security and customs and immigration are two other major areas that contribute to the airport's total environmental impact. Almost everyone has a stressful story to tell about excessively long times in the queue waiting for security screening or to clear through customs and immigration. That, in turn, has created uncertainty for the travelling public, who don't know when it is best to arrive at the airport on the day of travel. Consequently, many choose to be on the safe side and arrive at the airport three to four hours in advance. This places an extra burden on an airport's infrastructure that is already constrained, which furthers the congestion and gate delays. Airports are designed to move passengers – not to hold thousands of passengers for hours at a time.

Improper travel planning is not only a routine problem with the inexperienced traveller, but many travel agents still improperly place passengers with less than an hour's time between connecting flights at busy airports that are notorious for late gate arrivals, long queues for transit passenger screening and lengthy transfers between terminals. It all adds up to numerous gate holds and missed flights, which furthers the environmental impact of unnecessary CO2 emissions.

Last but not least – curfews force congestion at many airports. Many airlines, in their efforts to meet the demands of the travelling public, will try to maximise as many movements as possible as soon as the airport opens for business and just before the airport closes for the evening. Such a model contributes to the inefficiency of not only the airport itself but also puts a strain on the entire air traffic system.

So what can be done to improve the airport's effectiveness and the CO2 emissions? Usually there are several areas for improvement that can improve passenger and aircraft throughput as well as maximise the efficient movement of aircraft – all which adds up to fewer emissions and a cleaner environment.

Efficient movement of aircraft

Today's modern aircraft are 70% more fuel-efficient than those manufactured 40 years ago and 20% more than ten years ago. The modern aircraft achieves a remarkable fuel efficiency of 3.5l a passenger per 100km. However, even fuel-efficient aircraft will burn excessive fuel if they are not allowed to fly as they were designed. For example, significant environmental savings can be achieved if aircraft are allowed to depart and quickly climb to an operationally efficient flight level. However, most states have restricted aircraft to operate at 250kt or less below 10,000ft. Such speed restrictions require the heavy departing jets to increase drag, which results in an operationally inefficient flight profile and fuel wastage.

A typical four-engine aircraft on departure is usually forced to fly at a speed lower than their minimum drag speed, which may be up to 280kt in clean configuration of no flaps. This means that the aircraft needs to be configured with flaps flying up to 10,000ft, which incurs an unnecessary environmental, operational and financial penalty. The additional fuel burned can be an extra 300kg to 1,500kg a departure, which equates to 950kg 4,750kg of excess CO2. As this occurs at lower altitudes near airports, the excess carbon emissions have a more direct impact on the local area.

"Today's modern aircraft are 70% more fuel efficient than those manufactured 40 years ago."

Noise abatement departure procedures can be even more wasteful in terms of CO2 emissions.

These procedures were first developed in the late 1960s, during an era of very noisy aircraft engine performance. Since then there has been considerable reduction in noise due to modern engine design. Today's aircraft are 50% quieter than those manufactured ten years ago. On 1 January 2006, a more stringent Chapter 4 noise standard was introduced, for new aircraft designs. These Chapter 4 aircraft are at least one third quieter than those currently certified to the Chapter 3 standard. With modern aircraft, fuel and emissions can be saved with minimal impact on noise.

However, according to International Civil Aviation Organisation Annex 16, 'aircraft operating procedures for noise abatement shall not be introduced unless the regulatory authority, based on appropriate studies and consultation, determines that a noise problem exists'. In many areas where these procedures exist today, noise abatement needs to be re-addressed with decisions considering the trade-off of today's quieter aircraft against the fuel wastage of the departure procedure itself.

This is especially true for those departures where the climb occurs over water and there is no community below, where aircraft should be allowed to climb at a clean airspeed.

Continuous descent approaches, known as CDAs, also offer significant fuel savings and quieter operations, as well as safety benefits. A CDA allows the aircraft to arrive on a continuous descending flight path with engines at a quiet idle. By comparison, many arrivals have step-down flight profiles that require periods of straight and level flight.

This means that every time an aircraft is required to level off its engines must be accelerated with flap settings that require extra fuel burn, with a significant difference in noise when compared to an idle descent.

CDAs can not only save 400kg to 800kg of CO2 a flight but they also allow the flight to arrive with minimum noise. However, they are not always the perfect solution, because they require more spacing between aircraft, rendering them unsuitable during times of high-density traffic. However, when traffic is not so heavy they are a win-win solution for the airlines, the environment and the community. CDAs also allow late-evening arrivals to land with minimum noise to the communities below.

These are just two examples of how aircraft movement affects the environment. There are many other areas to consider such as taxiway design, aircraft taxi movement, de-icing procedures, as well as the management of aircraft movement on aprons and gates that have a direct impact to fuel efficiency and the environment.

"Continuous descent approaches can save 400kg to 900kg of fuel a flight."

Efficient movement of passengers

As explained earlier, the efficiency of passenger flows at the airport also has a direct domino effect on the environment resulting from CO2 emissions. There are many examples of best practices to follow for automobile traffic flows, check-in, baggage handling, security screening, customs and immigration, transfer between terminals and the terminal design and layout itself. From an airport operator point of view, trying to understand just exactly what the best practices are may be a daunting exercise. However, the airlines know exactly which airports have the best processes in design and practice.

Here is where IATA can assist airport planners to understand what works best for airlines and the travelling passenger. IATA has established airport consultancy committees to assist major airports in master planning, organised technical missions to help identify problem areas and solutions, and worked one-on-one with airport planners for customised solutions.

Airport emissions will always present a challenge in the growing world of air travel. But with careful planning and effective procedures there is a lot to be gained in saving fuel and reducing impact on the environment.