Keep the noise down: new certification standard to reduce aircraft noise

New environmental standards, in a range of industries and instances, are often met with rumbles of discontent or vocal displeasure. While the need to be cleaner or quieter might be reluctantly acknowledged, such measures imply higher costs, revised operating procedures and the need for new technologies: three things that many would rather avoid at a time of lingering economic uncertainty. But there are exceptions, as the aviation industry has demonstrated in recent years.

In 2013, the International Civil Aviation Organisation (ICAO) published the latest certification standards governing aircraft noise. Chapter 14 - the sequel to Chapter 4, which applied to aircraft of which prototypes were approved after 1 January 2006 - comes into force at the start of 2017. It will see the noise standard for civil aircraft reduced by seven effective perceived noise level (EPNL) decibels, applying to new high-weight aircraft from 2017 and new low-weight craft from 2020. When fully rolled out, the standards will reduce the total land area exposed to aircraft noise by 2% by 2026, removing 500,000 people from aircraft noise zones. This figure is expected to grow to more than one million by 2036.

The aircraft manufacturing industry saw the new regulations coming from a long way off and has used them as an opportunity to innovate with new engine, gearbox and wing designs. If you wander around the chassis of the new Boeing 747-8 aircraft, for example, you are likely to notice metal teeth, known as chevrons, on the trailing edges of the jet engine nozzles. These enhance the mixing rate of the shear layer - the layer of air between hot exhaust gas coming from the engine and the cold outside air that flows around the engine - helping reduce pressure fluctuations and, in turn, jet noise.

Manufacturers' track record in meeting noise reduction targets has long been very good, with new aircraft generally meeting the new standard and then some. Over the past 40 years, the noise output of aircraft has decreased by more than 75%, and with the heightened social and political pressure to reduce aircraft noise, particularly in densely populated Western Europe, there is a big incentive to keep pushing for quieter and quieter craft.

"If you look at how the noise certification levels have been handled, most of the new aircraft types are built to anticipate further increases in stringency," explains Thomas Roetger, assistant director of environment technology at the International Air Transport Association (IATA), whose 260 members' airlines make up 83% of air traffic. "If you look back in history from Chapter 2 to 3, to 4 to 14, there have been continuous tightening in regulations, and if a manufacturer wants to keep selling their aircraft it is necessary to anticipate further stringency. The margin to the certification rule is used as a kind of environmental green label, as a quality factor to help create positive publicity for that aircraft."

Part technology, part practice
Reduction at the source is one of five pillars that make up ICAO's 'balanced approach to aircraft noise management' to reduce the overall noise of aircraft operation, and is the only pillar that rests solely in the hands of the manufacturer. The other four pillars are land-use planning, noise-abatement operating procedures, operating restrictions and noise charges - advances that are hammered out in increments by an uneasy coalition of airlines, airports, and local and national governments.

Airlines, under great political pressure to ensure their planes are as quiet as possible, are going through a constant fleet-renewal process. Many of the new aircraft being delivered already meet the new Chapter 14 standards and Roetger believes that by 2017, even the aircraft that don't yet need to meet the standards will, simply because airlines are so keen to get the quietest technologies in place. Most airports are just as keen to bring down the volume, but according to Michel Adam, manager of environmental policy at IATA, they often act without consulting others, are too quick to use taxes and levies as a solution, and sometimes act in ways that are unwittingly detrimental to the business of airlines.

For example, London Heathrow Airport, which is relatively sensitive when it comes to noise impact, is planning to use Chapter 14 standards as a benchmark for its own noise emissions. By taking these standards and applying them to individual airports and countries, it is effectively lifting rules designed for new aircraft and applying them to all aircraft. To help older planes meet these standards, it is likely that operating restrictions, landing charges or night curfews would have to be introduced, which would make life that much harder for airlines.

"This obviously raises a number of concerns on our side," says Adam. "[Airports such as Heathrow] are using a standard that aircraft are not even legally meant to meet, and they are using it prior to its implementation. There is a risk, with that approach, of setting a precedent that as soon as you have a new standard, airports will introduce higher charges or new operating restrictions.

"There are over 600 airports in the world with different rules for aspects from noise abatement to flight procedures, to switching off APUs [auxiliary power units] at the stand, to night restrictions, and so on. So this is very difficult for an operator."
One has to be sympathetic to the airports. If somebody in the vicinity has a noise complaint, it is the airport that has to deal with it, not the operator of the offending aircraft, so one can see why they'd want their noise standards to be as stringent as possible. On the other hand, the behaviour of some local and national governments - while ostensibly positive - has more than a whiff of cynicism about it.

Roetger and Adam feel that increasingly, measures are being introduced by governments that are more politically than environmentally motivated. Taxes on aircraft noise are often imposed in a way that has seemingly little impact on noise or carbon emissions, existing primarily to boost the coffers of regional government. For example, since 2013, Italian airports have imposed taxes on noise emitted by aircraft during take-off and landing. The levy is set by individual regional governments and based loosely on the noise standards stipulated in Chapter 14 as well as an aircraft's maximum take-off weight (with aircraft under 4.5t exempt from taxation).

"You have no real earmarking - only 5-10% [of the tax] is set aside for environmental purposes, but we have no real idea of what these environmental purposes are," Adam says. "And those taxes are introduced bluntly, and there is no will from the regional government to look for other alternatives to improve the noise situations. That's probably because they don't really care about the situation."

Even if the environmental purpose of such taxes was clearly defined, IATA's argument is that punitive taxes are no way to encourage the introduction of quieter aircraft. The amount already being invested in fleet renewal is massive; in fact, investment in new aircraft is forecast to be around $4 trillion over the next 20 years. Placing an additional financial burden on airlines could well be seen as petty rent-seeking and is likely to backfire on governments in the long term.

"It's a bit simplistic to believe 'I'm going to introduce a tax and I'll get cleaner, quieter aircraft tomorrow'," says Adam. "But that's very often the way those levies are being advertised. It is more likely to be a reason for an airline to move away from that airport if it's not one of the essential parts of its route network."

A rebalancing approach
IATA would like to see all relevant parties get back to the 'balanced approach to aircraft noise management' and focus more on the oft-neglected second pillar: suitable land-use planning. Under pressure from growing populations, it is somewhat understandable that local governments have abandoned the idea of leaving aircraft noise zones free of residential property. Yet the sheer number of properties being built is a real headache for airlines and airports.

According to the Airport Operators Association, 6,000 homes in the UK have been built in airport noise zones over the past three years. No matter how much you invest in quieter technology and introduce new operational procedures, such planning strategies are virtually impossible to combat. A set of EU regulations on airport noise management that will apply from April 2016 could help by providing a framework within which the 'balanced approach to aircraft noise management' can be implemented but, ultimately, the EU doesn't have the power to tell housing authorities where they can and can't build. Adam doesn't expect miracles, but hopes that all will strive harder to compromise in the future.

"This all ties back to the fact that you very often have decisions being made a bit too quickly," Adam says. "'Balanced approach' is about making sure all the options, and all the combinations of options, are looked at before a decision is made so that an authority does not jump to a decision - 'I need some extra cash, people aren't happy with noise, so I'll introduce a tax'. It has to be more thorough in its approach."