Proposals put forward by Brussels are likely to see a number of aircraft/engine combinations excluded from certain European airports

After a tense couple of years, the 33rd general assembly of the International Civil Aviation Organisation (ICAO), which met in October, finally promised to lay to rest the arguments over a new engine noise standard. At long last, Chapter 4 had emerged for new aircraft types. Yet a split in the world consensus over noise regulation remains a real threat. Europe, in particular, continues to push hard for new ways to outlaw the noisiest aircraft/engine combinations.

Chapter 4 itself was widely seen as a relatively modest tightening in noise limits. It puts caps for new aircraft at a cumulative 10dB below that for the existing Chapter 3 - this is closer to the 8dB reduction sought by US negotiators, than to the European Commission's (EC's) more aggressive 14dB.

The new limits will only apply to aircraft certificated from 2006. In fact, European governments were keen to protect the Airbus A380, which should be certificated before the deadline. A questionmark could hang over Boeing's Sonic Cruiser, however. "Drawing board aircraft, such as the Sonic Cruiser, that may be certified after the standard comes into effect, will be required to meet it," says Alan Hedge, vice-president at the Campbell-Hill Aviation Group, which acted as consultants to ICAO's fifth committee on aviation environmental protection (CAEP 5), and which drew up Chapter 4.

The real controversy, however, has not focused on Chapter 4 so much as the bitter transatlantic dispute over what to do with the existing fleet of noisier Chapter 3 aircraft.

Europe's threat to ban marginally compliant hushkitted aircraft from next April produced a fierce US counter-attack. Brussels has long made it plain that it wants these aircraft phased out long before 2006. In the USA, on the other hand, the prevailing position is that they simply pass required tests, and that should be that. "Chapter 3 is a bright line standard. There are no 'marginal' Chapter 3 aircraft," Hedge says.

In the event, ICAO brokered a compromise in the run-up to the general assembly. Under this, it was agreed there would be no official phase-out, but that individual airports could impose operating restrictions as part of a a broader programme designed to combat noise - the so-called "balanced approach".

The EC,keen to prevent a total free-for-all in its back yard, is putting forward legislation which will lay out the framework under which European airports may restrict aircraft which are within 5dB of Chapter 3. That effectively allows for the same result as the hushkit ban. It is also indicating that a 8dB limit could be on the cards at some point.

Although the proliferation of different engine/airframe permutations and modifications makes it difficult to gauge the true impact of these proposals, there is no doubt that a huge volume of today's in-service aircraft would be affected. On a rough count, there are in the region of 2,000 narrowbodies flying which would fail the 5dB test, with another 1,000 in storage. Around 700 would fail at 8dB, along with a further 200 stored aircraft. This would put around a quarter of the active world single-aisle fleet at risk if a higher 8dB level were implemented.

For widebodies, the 5dB rule would catch approximately 600 in-service aircraft and the 8dB another 400. That again puts over a third of the active fleet at risk with the higher 8dB proposal.

However, many of the types at greatest risk are now ageing. Some are already stored, and others are likely to join them before the EC's proposals are brought in by European airports. Also, few of the worst affected types fly within Europe. For example, around 60-70% of the active fleet of McDonnell Douglas DC9s and Boeing 727s fly within North America, with only 70 or so units in Europe.

Raising limits

The EC's 5dBproposals are being considered by the European Parliament and Council of Ministers, and should be passed by the end of March, replacing the hushkit ban on the statute books. Once the framework is put in place, the EC plans to keep up pressure on the noise issue, promising to issue a report "no later than five years" after the framework is announced. "This report will, in particular, address the need for introducing a more stringent definition of marginally compliant Chapter 3 aircraft in terms of moving, for example, from a cumulative margin of 5dB to one of 8dB," it says.

At this higher limit, the proposals would not only catch ageing types. A notable casualty, for example, would be the McDonnell-Douglas MD-80, where around half the world's 1,000-strong fleet could be hit. These aircraft, most of which are powered by Pratt & Whitney JT8D217s, only just creep over the 5dB threshold, even though all have been passed as Chapter 3 compliant - and more than 300 MD-80s are flying in Europe. The USA has long feared that this aircraft was a target of the Europeans, and is quick to point out that it was agreed at ICAO that there should be no discrimination against particular aircraft types.

Another major casualty would be the Boeing 737-3/4/500, where around 850 aircraft, not far short of half the world's fleet, would be affected. Around 30%of the fleet flies in Europe, and all are powered by variants of the CFM56 - though the particular thrust levels may make a difference. Higher thrust can in certain circumstances improve noise performance on take-off as it means higher altitude is reached more quickly. But it tends to be a disadvantage on approach.

By contrast, the younger Airbus fleet comes off relatively lightly, although a small number of early A320s and A321s will fail to meet the 8dB cut-off point. An ICAO insider says a number of these will have their engines modified in the near future to meet the 8dB limit.

The 8dB threshold would also include most of the world's hushkit fleet. All but a handful of Boeing 727s would be affected, as well as the entire 737-200 fleet (mainly powered by P&W JT8Ds), half the world's McDonnell Douglas DC8s and all DC9s. The fact these aircraft come under the Boeing stable, and that Airbus short-haul aircraft are not affected, has not been lost on the US side. Europeans are point out that this partly reflects the fact that the Airbus A320 family was simply designed more recently.

On long-haul, around 40% of the ageing Airbus A300Bs (powered by CF6-50s and JT9s) and just under half of the A300-600 fleet (mainly powered by CF6-80s) are at risk. But again it is Boeing models that are in the frame. A number of these are aged, but would normally re-emerge in cargo fleets.

Express operator FedEx is the largest single operator of DC-10s, and has been busy acquiring more from American and United Airlines. The longer range DC-10-30s fly on the transatlantic, and could be a big casualty of a crack-down. Half the world's fleet would flunk the 5dB limit - and virtually all fail the 8dB test.

Older Boeing 747 classics, too, would be a clear target for Europe's new airport noise framework. All 747-100s and possibly some -200s would be hit by a 5dB limit, accounting for around 40% of the world fleet. These aircraft are powered by JT9s, RB211s and CF6-80s. One observer close to CAEP 5 says there are modifications which can be made on these aircraft to improve noise performance, such as fan and blade spacing - but they may not be economical for cargo operators because utilisation levels may not justify it.

A relatively small number (less than 30) Boeing 767s are also in the firing line at the 8dB threshold.

Although Brussels aims to see the framework pass regulatory muster by the end of March, it will take time before its impact is felt at airport level. It will take at least a year for the EC directive to be adopted into national law by each of the member states.

After the proposals have gone through this legislative process, airports must still prove operating restrictions are necessary as part of a "balanced approach". If they can show this is the case, they will be able to ban new "marginal" aircraft after six months. Then they will be entitled to remove these aircraft at a rate of not more than 20% per year. "The rate of removal shall take into account the age of the aircraft and the composition of the total fleet," the EC says. This means it will take around six to seven years for an airport to ban all aircraft that fail to reach the 5dB limit.

Hushkit option

Last time around, many airlines were able to meet the Chapter 3 restrictions through hushkitting. Observers agree, however, that this is now unlikely to be an option. "Nobody knows how to hushkit a high-bypass engine," says one ICAO official. Few aircraft are likely to hold sufficient value to justify the cost of extending what remains of their life through an expensive hushkit refit.

Also in the Chapter 3 round of noise legislation, airlines were able to carryout various modifications on older aircraft to improve noise performance. Indeed, some participants at CAEP 5 were amazed by the number of modifications which different airlines had carried out.

In effect, it has resulted in a proliferation of noise certification levels on aircraft/engine combinations which should theoretically meet identical levels. Determining which aircraft meet or fail new noise tests almost becomes a case-by-case business.

But there is, without doubt, less room for manoeuvre. The ability to improve engine performance with modifications to high-bypass engines is simply proving more difficult than it was for their low-bypass predecessors. And, although the time limits are still vague, and implementation yet to be decided by individual airports, there is a real prospect that a significant cross-section of the world fleet could find itself compliant with international standards and yet unable to fly to a range of major European airports over the next 10-20 years.

Source: Airline Business