Noise regulations coming into force in Europe and the USA are forcing aircraft owners to consider the future of their ageing fleets

Ian Sheppard/London

A ban will apply in Europe after 31 December, 1999, on aircraft not complying with International Civil Aviation Organisation (ICAO) Chapter III rules, while, in the USA, aircraft not complying with US Federal Aviation Administration Stage 3 regulations must be phased out by 1 April, 2002.

Most European carriers with such aircraft are replacing them, although some have bought hushkits to boost resale value. Major US carriers are able to hushkit large fleets and operate them throughout the country without penalty.

Various options have emerged to avoid costly fleet replacement programmes, including re-engineing. Capital cost and the effects on performance and residual value must be balanced carefully, along with the cost of hangar time for modifications.

Early hushkits tended to increase drag and fuel consumption and, although manufacturers have refined designs to negate this, many aircraft still have older, Stage 2, kits. The increase in aircraft empty weight, which reduces its payload, has also been addressed.

However, modification of load bearing structures inevitably affects the aircraft's type certification, and has contributed to the emergence of more elegant solutions that rely partially or entirely on reduced thrust settings, altered aerodynamic surfaces and winglets.

After the FAA introduced Part 161 legislation in 1991, giving birth to Stage 3, Pratt & Whitney teamed with FedEx to find a solution for the Boeing 727, while Nordam worked on the 737-200 and ABS Partnership on the McDonnell Douglas (MDC) DC-9. All three types are powered by the P&W JT8D, which accounted for more than 30% of the world's jet fleet and for almost half of the narrowbody fleet.

The FAA says that 80% of aircraft operating in US airspace are now Stage 3 compliant and, by the end of the year, 75% of Stage 2 aircraft must have been phased out or converted. By the end of 1999, there will be no Stage 2 aircraft flying in the USA. Meanwhile, the FAA is also working on NASA's Advanced Subsonic Transport effort to develop noise-reduction technology. This has run since 1992 and is due to conclude in 2000, with the goal of a 10dB reduction in "source noise".

For noise certification, take-off, sideline and approach measurements are made, and complex formulas applied to limit noise impact, with added penalties for Stage 3 aircraft and night operations. Whereas in the USA exceeding the limit in one of the three categories is allowed as long as the aircraft is comfortably inside the limit in one of the other two categories - so-called "acoustic trades" - Europe demands that the limit is met in all three categories.

The European Commission is planning to widen the US-European compliance gap even further with a proposal to legislate against hushkits altogether, on the grounds that, even if kitted aircraft meet Chapter III standards, such aircraft meet the requirements "with very small margins", says Dave Tomkins, the UK Civil Aviation Authority's head of air services policy. European Union nations are also concerned that, after 2002 - the deadline for complete phasing out of Chapter II aircraft - there will be "-nothing else going on to improve things".

Tomkins says the proposal is "-progressing through the EC", which aims to have adopted it in December. The current document suggests banning more additions of hushkitted aircraft to European registers from 1 April, 1999, although this is likely to slip to December "-for it to be put into states' own legislation", he says.

The second stage would require any non EU-registered aircraft operating into Europe to meet two criteria: to have been on their home country's register on 1 April, 1999, and to have a history of operating into Europe. "The message is that modifications is not the way to go," says Tomkins. "It is a freezing of the fleet - what you have, you hold." For example, under the new ruling, British Airways could hushkit its Chapter II 737-200 fleet, but it would not be able to add any more aircraft.

In a letter sent earlier this year to the president of the European Civil Aviation Conference (ECAC), André Auer, however, FAA chief Jane Garvey expresses her concerns over the EC/ECAC proposals, which she says are "-at variance with ICAO certification standards and would undermine our efforts to achieve global standardisation".

In April, ICAO's Committee on Aviation Environmental Protection agreed to resume work on establishing for jet aircraft new noise standards which would be more stringent than the current Annex 16, Chapter III, standards - a matter set aside in 1995. ICAO says, however, that the potential increase in noise levels at some airports because of increases in traffic, even allowing for the phasing out of the older, noisier, Chapter II-compliant aircraft, prompted the renewed focus on jet noise.

Tomkins says that the EC plans to press ICAO at a meeting in Montreal in September to "-put Chapter IV back on track to enshrine new technological developments in legislature". It would have to recognise the need to be a "noise regime" rather than a "certification regime", and be designed for airport restrictions from the outset, unlike Chapters II and III. It would also be necessary to account for the predicted trend towards larger average aircraft size, with the growing pressure on airport capacity, "-to ensure that the benefits we've got continue".

An added problem in Europe is that airports have unilaterally introduced even stricter regulations which cannot be met by hushkitted aircraft. For example, plans by the Netherlands to introduce a strict noise regime at Amsterdam's Schiphol Airport were scuppered when chaos threatened, although it has since had to rein in planned growth in movements. Despite careful slot co-ordination, growth looks likely to fall from around 8% to 4% or less.

Measures are likely to include more severe penalties on Stage 2 aircraft, which are already penalised by double landing fees during the day. Other, longer-term, measures being considered include bringing forward the opening of a fifth runway, due in 2003. KLM argues that the contour boundary should be made more flexible so that a minor infringement in one area does not automatically penalise the whole operation.

Boeing 727

In addition to the original FedEx kit for the Boeing 727, Raisbeck and DuganAir have each developed solutions that rely heavily on reconfiguring flap and slat settings, using reduced thrust, which are relatively quick to install and at considerably less cost.

The decision by American Airlines in June not to hushkit its 727-200s, instead adopting an aerodynamic modification developed by Raisbeck to meet Stage 3 noise limits, was a significant development and a blow to FedEx.

American bought 52 Stage 2 kits, with a further 26 to follow when Seattle-based Raisbeck certificates its Phase 3 kit for higher gross weight -200s in April 1999. This will allow a maximum take-off weight of 84,615kg (187,000lb), rather than 75,820kg, while the Stage 4 kit - to be ready at the same time - will take it to 89,500kg. "More than that and you've got to go to FedEx," says chairman James Raisbeck. Empty-weight change is zero.

The Phase 2 kit, ordered by American and available by September, costs $1.1 million and can be installed in just over 100 man hours, while the FedEx hushkit costs $3 million and takes 21 days to install, says Raisbeck. The company's Phase 1 kits for the standard 727-100 and -200 were certificated in December 1996 and cost $700,000, requiring only 30 man hours to install. The Phase 3 kit costs $1.5 million, while Phase 4 costs $1.8 million and takes 219 man hours because of the extra leading edge slat deflection. Phases 3 and 4 are the only ones to add any weight - 43kg.

Raisbeck's solution requires the aircraft already to be fitted with Boeing's "Quiet Nacelle" and reduces noise by lowering engine temperature flat rating and modifying the aircraft's high lift devices - leading edge slats and trailing edge flaps - to allow their use at higher speeds. As the flap angle is restricted to 25í rather than the normal 30í, "-we've taken a 4kt [7km/h] hit on approach speed", says James Raisbeck, and this increases the take-off run by about 140m (450ft). "When you plug up a tailpipe, it costs you range. The secret is not to derate the engine, just don't push the throttles so far," explains Raisbeck.

The company was able to achieve a phenomenal difference because the "-flaps were like big barn doors" with only one deployed position. The final and most obvious advantage, says Raisbeck, is the fact that, once the kits are available, they will easily keep up with any increase in demand, and operators will not be under pressure to get their orders in so soon.

Raisbeck estimates that 200-250 727-200s have yet to be hushkitted, and says that orders have been placed by other, as-yet unannounced, US airlines. In early June, Colombian freight carrier Lineas Aereas Suramericanas and Northstar International followed American Airlines - the company's first major order.

James Raisbeck disputes claims that hushkitted aircraft should maintain higher residual values, predicting that the standard $2 million difference between Stage 2 and 3 727s is set to fall. Previously, Stage 3 was "the last financial blow" for 727 operators, he says, whereas American was able to save "well over $100 million" - but "-many airlines are already committed to an expensive alternative". The main beneficiaries are likely to be lessors who will see the "life and usefulness" of their asset extended, he adds.

In April, the FAA awarded a supplemental type certificate (STC) to DuganAir Technologies for its Quiet Wing System, which allows Boeing 727-100s and -200s to meet Stage 3 requirements without hushkits. It has been under development for four years and combines winglet technology developed by Winglet Systems, with modifications developed by DuganAir in one package, including a flap and aileron droop system, and which requires the removal of the third engine thrust reverser. This decreases the aft centre of gravity by almost 1.1t, reducing overall weight and enhancing balance. An acoustic tube is added in the inlet, which, DuganAir says, increases gross weight to 95.3t, resulting in up to 5% payload growth, with the same fuel. Range is claimed to increase by as much as 13% because of the winglet design.

Robert Olson, vice-president of marketing with Bellevue, Washington-based DuganAir, says that the company has increased the maximum gross weight for which its solution is available to 95.3t for all engines "through the -17R", with up to 6% fuel saving. With all testing completed last November, Olson says that the company is now analysing data and believes it can increase the maximum weight to 98t .

Olson says this is far greater than possible with Raisbeck's solution, which has an 89.4t maximum, and is heavier than any original 727. He also points out that DuganAir's solution uses the "same speeds as the basic aircraft", and therefore does not increase landing field length, "especially in wet or icy conditions". Its kit costs $1.1-2.2 million, depending on weight, compared with $1.8-$3 million per engine hushkit, and modification time is down to about seven days.

Orders have been received for 32 conversions, 10 of which are for -100s. Of the -200s on order, four are passenger versions, says DuganAir. Canadian company Kelowna Flightcraft has ordered seven kits for its 727 freighters, while US carriers Sun Pacific International and Express One International have contracts for two and nine kits, respectively. Duganair has two new unannounced customers - plus the Imperial Palace Hotel in Las Vegas, which has three 727s and plans to "-go into leasing and VIP charter", says Olson. Kelowna is performing the initial conversions in a partnership with DuganAir, called Quiet Wing Systems.

Federal Express Aviation Services has been selling JT8D hushkits for the 727 for several years and, in April, began offering a Stage 3 kit for the 89.6t maximum take-off weight version of the aircraft. The company now claims to offer kits for any 727 in the world at design take-off thrust. Phil Blum, manager of marketing at FedEx Aviation Services, does not consider re-engineing or kits from DuganAir and Raisbeck to be a major threat, saying they are for niche markets and cut into the performance envelope.

According to Blum, FedEx has received orders for 125 shipsets since January 1997, has 676 firm orders with 140 options and has delivered more than 500 to 60 customers worldwide. "We believe our approach is still the way to go," he says, adding that FedEx delivered 22 shipsets to American Airlines in 1996/7.

One 727 re-engineing programme is now under way, headed by California-based Rohr (now BFGoodrich), supported by P&W. The "Super 27" package involves replacing the aircraft's outboard engines with the latest, -200, version of the JT8D and adding a new acoustic exhaust mixer to the existing centre engine. The modification, which costs $12-15 million, brings the aircraft inside Stage 3 limits and provides a 6-7% cut in fuel consumption, claims Rohr. The company says that more than $2.5 million of the cost can be recouped from selling the removed engines. Its latest customer, signed up in early June, is a private operator whose aircraft will be modified in the UK in December.

BMW Rolls-Royce, in conjunction with Dee Howard of the USA, has proposed re-engineing the 727 with its BR715 turbofan in the outboard engine positions with either a smaller BR710, R-R Tay, or derated JT8D in the centre position. BMW R-R believes that orders could come from night freight carriers which want to operate even quieter 727s. The programme would probably be launched by a large US operator and the company is targeting a potential market of 70-150 aircraft. It is working towards an entry into service date of mid-2000.

Such re-engineing could cost $10-15 million per aircraft, although the BR715 is around 10% more fuel-efficient than the Tay used for the now-completed UPS 727-100QF re-engineing programme. The most cost-effective solution for the centre engine, says the company, would be a derated JT8D, which would avoid the need for the enlarged S-duct used on the 727-100QF.

McDonnell Douglas DC-9

ABS Partnership received FAA certification for its MDC DC-9-50 Stage 3 hushkit in January, having already developed a Stage 3 kit for every other variant of the P&W JT8D-powered DC-9. The company has been working on a solution for the larger JT8D- 17-powered -50 for several years and developed a new 18-lobe exhaust mixer with P&W, which was "abandoned" in favour of the original 12-lobe item, says Bob Fregeau, director of marketing at Sparks, Nevada-based ABS.

"We redid the entire analysis so we could discard the 18-lobe," says Fregeau, who adds this included refining the gear-retraction drag calculation. "ABS now holds an STC for 54.5t with -17 power, but we're still chasing the 121,000lb maximum weight," says Fregeau.

Some 95 DC-9-50s remain in service, and ABS says it has interest from key operators such as Meridiana, Northwest Airlines and Trans World Airlines. In April, Air Canada revealed plans to hushkit up to 27 DC-9s with ABS Stage 3 kits, with deliveries to be completed in August 1999. ABS, which remains the only company to have developed a kit, says that it now has 476 orders with 71 options, and that there are "something like 835 of the fleet left".

The US Airways and Continental fleets are being sold but "-most will end up hushkitted", believes ABS, as will TWA's 70 or so aircraft. ABS estimates that half of the "remaining 250 or so" will be hushkitted, too, and reports "considerable activity" with the "-third and fourth intervals now approaching" - indicating smaller fleets. ABS sees no competition emerging at this late stage, although James Raisbeck says his company is "active on the DC-9-10 to -50", and looking at potential aerodynamic modifications to meet Stage 3 limits.

Fregeau believes other opportunities are limited. The company determined "around six years ago" that the "-DC-9 won't take winglets", for example - although this is not a Raisbeck requirement. "It's a difficult aircraft, subject to the two-engine rule," he says.

Boeing 737

Nordam has delivered just half of the 300-shipset-strong orderbook for its Boeing 737-200 hushkit, which received its first FAA STC in 1992. The company is "-shipping out 10-11 shipsets a month" from its Tulsa, Oklahoma plant, says Jack Arehart, vice- president of programme development. He says Nordam has about 80% of the 737 market, with Av Aero its only competitor, and has around 100 orders. Av Aero "-is used [by prospective customers] as a leverage to negotiate terms", adds Arehart.

The current 737-200 fleet consists of 975 aircraft, of which about 500 "-are already committed" to hushkitting or re-engineing, says Arehart. Of the rest, Nordam is coy about how many are likely to be retired, but Arehart stresses that many in "non-noise-sensitive areas" of the world, such as Indonesia, could benefit from hushkitting in terms of resale value back into the USA or Europe - and time is running out. He says lessors are driving demand because they have to keep an eye to their next customer.

Arehart paints a picture of a politically charged noise-abatement world, and is acutely aware of EC plans to freeze the hushkitted fleet. "As long as customers sign up before the EC date with a deposit, they'll be exempt," he says. Meanwhile, Arehart sees the EC "-jacking up landing fee rates under the guise of noise to replace taxes from duty free shops".

He also feels state carriers have undue influence in Europe because they do not experience the commercial pressures which have forced carriers such as Ireland's Ryanair - from which it has "-just received an order" - to retain older aircraft. Arehart also suggests that the EC is "-taking economic advantage away from Europe". Nevertheless, Nordam has just received an order from Olympic Airways of Greece, but is unable to reveal details.

Boeing 707 and MDC DC-8

Burbank Aeronautical II (BAC II) spent $20 million over three years developing a Stage 3 hushkit for the Boeing 707's P&W JT3D engines, aimed at a potential market of 150 707-300s, mostly freighters. BAC II says that it is the only company to offer such a solution, and estimates that there are still 110 707s operating in the USA, with many "coming back" to that country, where they can be operated "more profitably".

The kit was first flown in April 1997 and noise tests were completed in September that year. Thomas McGuire, vice-president of marketing, says that flight testing of the thrust reversers at Mojave, California, including an in-flight deployment test, is finished and that the programme will be "100% complete" by 22 June, following anti-icing trials. "We are now getting things over to the FAA," he adds, "and hope for an STC by late July."

The company claims that fuel consumption is 11% below that of Stage 2 hushkits, and noise is attenuated by 30dB for a Stage 1 aircraft and by 15dB for a Stage 2, JT3D-7 powered, aircraft. A JT3D-3B shipset costs $2.9 million, and a -7 shipset $3 million. BAC II is already building "a number of" components which could not be subject to any last-minute design changes, says McGuire. It is aiming to ramp up production to three shipsets a month by 1999, with 40-45 due to be complete before 2000.

BAC II is also developing winglets, which it calculates will improve fuel consumption by 7%, for a price of $700,000 a set. It had originally hoped to flight test them with its JT3D hushkit, but the FAA required separate programmes. McGuire says they should be available in September-October. The first example was delivered to BAC II in early June and will undergo structural tests. After these, two examples will be strapped onto a 707 for flight testing, which the company expects to be complete within a month.

The hushkits and winglets together offer operators of Stage 2 aircraft a 15-17% improvement in fuel consumption, says McGuire. The new long-shell hushkits add no drag to the basic engine, negating the 10% or so fuel consumption penalty suffered with the original Stage 2 707 hushkit.

The new thrust reversers contribute most of this saving, being hydraulically rather than pneumatically operated, and there are target-type blocker doors in place of the cascade assembly. Results achieved with the 80kN (18,000lb)-thrust JT3D-3B and 84.5kN -7 allow aircraft to meet Stage 3 requirements at full take-off weight with no payload restriction. Heavyweight landings to Stage 3 could be achieved only with 25í, rather than 40/50í, landing flap, however.

BAC II is also developing a Stage 3 hushkit for the DC-8-50 and -61, which is due to receive an STC in July. The DC-8 kit is applicable to about 100 aircraft still in operation. The company expects to perform Stage 3 hushkit and winglet flight tests on MDC DC-8-50s and -60s later this year.

McGuire says that BAC II is watching developments in Europe "very closely", and that it is aware of the proposed "non-addition rule".

Omega Air claims that its programme to re-engine the 707 with more powerful P&W JT8D-219s will bring the aircraft comfortably within Stage 3 limits, while reducing fuel consumption by 20% and aircraft weight by 180kg, yielding a range increase of 30%, and a 45% reduction in time to initial cruise height. Omega claims the aircraft will "-outperform the [Airbus] A310-300 in nearly all parameters as an aerial-refuelling aircraft".

Using four brand-new JT8Ds, which remain in production for the MD-80, pushes the cost per aircraft up to $15 million. Swearingen Aircraft of San Antonio, Texas, which will undertake the conversion work, took delivery of the first aircraft in March. The first five engines will be delivered in December, first flight is scheduled by March 1999 and an STC should be gained by late 1999, says Omega, which will re-engine its own portfolio of some 25 707s.

BAC 1-11

In late 1997, Quiet Technologies delivered the first BAC One-Eleven engine hushkit demonstrator to European Aviation of Bournemouth, UK. About 100 aircraft which could benefit from hushkits remain in operation, while Florida-based Quiet has also adapted the kit for the One-Eleven-500, certificated in the USA and targeted at about 12 corporate operators there.

Trevor Whetter, managing director of European Aviation, says -400 proof of concept flights are due to start on 24 June, with around 10 flights planned. On 13 July, the company will deliver a 70-seat -500 Series "-to do proof of concept in the USA", says Whetter, while the -400 kits will be fitted to one of its 24 One-Elevens for another 10 flights. "We will then enter a full certification programme," he says.

The pressure is on because, under current European rules, the company has to "-phase out" 10% of its non-Chapter III-compliant fleet every year. The company is also planning to hushkit 13 Boeing 737-200s that it purchased from Sabena recently. It says that it is "in negotiations" with Nordam and Av Aero, and will make a decision shortly after final presentations from the US companies at the end of June.

Turning to the EC plans to ban hushkits altogether by 1999, Whetter is "concerned". He adds that the company has invested considerable sums on the premise that the 2002 deadline to be Stage 3-compliant, with or without kits, would stand.

Gulfstream II/III

Stage III Technologies is completing a redesign of its planned hushkit for the Gulfstream II and III business jets, and hopes to begin flight tests in October-November. Design refinements were carried out following proof-of-concept ground tests earlier this year at Dallas Airmotive and Rohr. Dallas Airmotive has agreed to market the hushkits to satisfy Stage 3 noise limits, and perform installations at six sites around the world. The Dallas, Texas-based company expects to begin installing flight-test hushkits on a customer's GIII in September. The first production kits are due to be available early in 1999.

Stage III says that its hushkit will allow R-R Spey Mk511-8-powered GII/IIIs to meet the Stage 3 noise limits with no degradation in take-off performance, "minimal change" in cruise performance and a 3% increase in static thrust.

The hushkit includes an external mixer-nozzle and fixed position ejector. Operators of Stage 2 GII/ IIIs will be able to retain the existing thrust-reversers if desired, but hushkitting of older Stage 1 aircraft requires elimination of the thrust reversers, says the company.

Meanwhile, Gulfstream is investigating the possibility of re-engineing GII/GIIIs with the new General Electric CF34-8, work that could be undertaken by Garrett Aviation of Arizona.

Fokker F28

Stage III Technologies is also developing a hushkit for the Fokker F28's Spey 555 engines, based on a Stage 3 hushkit already under way for the Spey 511-powered GII and GIII business jets. The new kit is expected to be certificated and available for customers by the third quarter of 1999. Las Vegas, Nevada-based Stage III has completed initial windtunnel tests of the prototype F28 hushkit and is preparing for flight tests. Performance penalties are expected to be no greater than the 5-7% estimated for the Gulfstream hushkit, and Stage 3 limits will be met without reducing gross weight, says the company.

Small changes are needed to adapt the ejector/mixer design to the lower-thrust Spey 555. Dallas Airmotive is marketing the hushkits, and will undertake installations. It expects the equipment for the F28 to have about the same $1.5 million cost as that of a GII/III shipset.

Stage III says that the F28 project does not need data from Fokker Aviation, which has a programme under way to re-engine the twinjet with the Tay 620, used on the Fokker 70 and Fokker 100, to replace Speys. It is being considered because further hushkitting to meet Stage 3 limits is expected to invoke severe performance penalties. Large F28 operator Horizon Air is a front runner to launch the programme.

For $8.5-9.5 million, customers for the conversion would get 15-20% more range, because of a 12-20% reduction in fuel consumption. Also, a 1.14m-long fuselage plug would be inserted forward of the wing to offset the weight of the larger engines.


It is not just narrowbodied airliners powered by low-bypass-ratio engines that are falling foul of the new rules. The partnerships of Air Foyle/ Antonov and Heavylift/Volga-Dnepr must hushkit their Antonov An-124 freighters to allow continued operations in Europe and the USA, despite the fact that they are fitted with "big-fan" engines.

The decision to develop a hushkit followed a study into re-engineing the aircraft with the CF6-80C2, which was deemed to be not economically viable. The Progress Design Bureau, which designed the D-18T turbofan, and Antonov have developed a Stage 3 hushkit which involves "-drilling a very large number of microscopic holes in part of the nacelle", says Air Foyle. All of Air Foyle's fleet will be modified as more kits become available.

Rybinsk Motors is developing a combustor and a hushkit for its D-30 turbofan, which powers the Ilyushin Il-76 freighter and the Tupolev Tu-154. The proposed hushkit has vortex generators and an ejector with acoustic mixer - claimed to cut noise by 3-4dB - while the updated combustor has a new forward section to allow for "more efficient fuel atomisation"

Source: Flight International