Twin challenges: blast and noise

posted on 27th June 2018

Airside operations have many challenges, amongst them the dangers associated with the use of jet engines in populated and congested areas. It’s part of an airport authority’s role to minimise the impact of and noise on both the airfield and the local off-airport community

Blast walls and fences represent a frequently used method of protecting infrastructure, equipment and people from aircraft jet blast. The vast majority of airfield blast walls are made of steel but in 1998 one company, Toronto-headquartered Blastwall, introduced a patented fibreglass blast wall design and construction. Then, a couple of years ago – explains president Peter Roston – clever engineers at the company found a way of simplifying the construction process while making the fibreglass blast walls even stronger and more effective at blast deflection; and all with no increase in cost to the customer, he notes.

The advantages of fibreglass design are twofold, Roston considers. The first lies in the fact that fibreglass can have no possible undesired influence on airfield locator beacons, and can thus be positioned without regard to them – something that cannot be said of steel blast walls, he insists.

Its second benefit lies in the fact that Blastwall’s fibreglass designs are frangible – ie, they fragment when struck and lose their solidity, a significant advantage if a blast wall were to be struck, for example, by the undercarriage of an aircraft taking off from or landing on a nearby runway.

Blastwall continues to offer four different fibreglass wall designs (although it will create a design of pretty much any dimension according to client requirements). However, as Roston is quick to admit, fibreglass is expensive – perhaps twice as costly to the buyer as its steel equivalent designs. Hence Roston’s decision to venture into the much larger steel blast wall market a couple of years ago. Up till now, it’s been “a pleasant and successful introduction” to this bigger marketplace, he says.

There continues to be plenty of demand for both fibreglass and Blastwall’s new steel constructions. The company is currently overseeing the installation of a steel blast wall at San Francisco, for example, while July 2014 should see – as Airside International goes to press – construction work begin on a fibreglass wall at the US East Coast gateway. A blast wall is also soon to be installed at the Russian airport of Pulkovo, St Petersburg.

 

Customisation

When it comes to airfield blast deflection, there are different sizes, different shapes, different materials used, but at the end of the day they are all designed to deflect engine blast vertically away from infrastructure or populated areas.

What do differ are the needs of the customer. According to Roston, the various manufacturers in this field are more than competent when it comes to fulfilling those various requirements. In the end, he says, it comes down to the ability of the blast wall designer to deliver the project on time and in the way that was promised, although price will of course always play a part in keeping a customer happy.

Another big name in the field of blast deflection is Transpo Industries, Inc. President and chief operating officer Mike Stenko agrees with Roston that meeting the customers’ very specific requirements is vital. He believes that good communication is critical to ensuring that the blast fencing provided to customers is exactly what they need.

“Ongoing communication is key,” he explains. “Often an airport realises that it needs a blast fence and starts the dialogue (with Transpo). We then help them to identify their needs and customise a design to meet those needs.”

Those requirements will be dependent on a number of factors, not least the aircraft types involved, the location in question, the assets that are to be protected from jet blast and the nature of the jet blast criteria.

Transpo has been in the business since 1968 and has developed its own unique offering. Its blast fences have the minimum possible footprint, Stenko says, allowing the company to design solutions for the smallest of spaces.

This ability to design and provide smaller deflectors is key in today’s evolving market. As airports add to their ever-more extensive infrastructure, new buildings and other assets are being brought into ever-closer contact with aircraft on the apron. Hence the need both for more blast fences, and for smaller deflectors that fit into confined airport spaces.

Moreover, Transpo offers what it describes as a unique design that allows the easy incorporation of gates and doors in the fence, while also permitting the blast deflector to be scaled up and down as required to meet only what the customer requires – and no more. This minimises the cost. Finally, as well as its customised designs, Transpo also emphasises its after-sales customer support, working with clients after installation to ensure that all is as planned and hoped.

GRE development

While jet blast deflection is very much in the blood of Reno-based Blast Deflectors, Inc (BDI) – the company has been offering blast deflectors to customers for nearly 60 years – it is also heavily involved in ground run-up enclosure (GRE) design and installation. But, as Don Bergin, director of technical sales at BDI, points out, GREs are really only blast deflectors with an aerodynamically enhanced acoustic enclosure, a method of tackling those twin challenges of jet blast and noise in one.

Much of the company’s work this year has concerned two GREs that it is introducing into Far Eastern airports at Seletar in Singapore and Subang in Malaysia.

The GRE at Seletar, a general aviation gateway operated by Changi Airport Group (CAG) – which also looks after the much bigger Changi International Airport nearby – has already been built, although the paving around it is still under construction. Testing at the GRE was expected to begin in late 2014.

The GRE is able to accommodate aircraft of up to B757 size. It was deemed necessary because engine run-ups performed at Seletar are currently conducted relatively close to residential areas – a not-unexpected problem given the size of Singapore, and one that is not likely to ease in the future.

The speed of the build was impressive, thanks in part to BDI’s excellent relationship with CAG, which issued the tender for the GRE last year. BDI technicians are on the ground from the start of such a project to the very end, Bergin says, although a local sub-contractor handles the facility erection.

The other GRE with which BDI has been heavily involved this year is Subang, which serves both civilian general aviation and the Royal Malaysian Air Force (RMAF). The new GRE is for the latter and is expected to be used by both RMAF fighters and transport aircraft (its existing C-130 Hercules and soon-to-be-delivered A400Ms).

Seeking to mitigate the noise produced by a modern fighter aircraft running at full afterburner is a major challenge, and one that differs in no small degree to that for handling transport aircraft and civilian jets, Bergin points out. The Subang GRE represents the first enclosure built by BDI in Asia that will be dedicated to military use.

The Seletar and Subang GREs will add to two other such enclosures BDI has designed and constructed in the Far East, one at Kuala Lumpur International Airport and one at Bangkok Suvarnabhumi International.

According to Bergin, one of the unique aspects of a military GRE is the type of blast deflector used. Due to the extreme exhaust temperatures and velocities of fighter aircraft running at full afterburner, the Subang GRE required a highly specialised jet blast deflector designed specifically for this application.  “We supply many afterburner-rated deflectors for military forces and aircraft manufacturers around the world, and our experience has resulted in a deflector with very unique geometry and material composition.  The Subang project has been quite interesting as it is a blend of our fighter aircraft deflector technology with our commercial GRE design,” he remarks.

Meanwhile, BDI has continued to invest in improving its blast deflection product technology. In the business since 1957, “We really developed the industry and the technology,” Bergin considers, but the company is not content with that and insists on ongoing development.

What he calls BDI’s deep “tribal” knowledge of this very specialised segment of the airport business has been based on decades of field experience as well as its own in-house research and development that entails scale modelling, computer simulations and full-scale testing with aircraft. The company has a full-time employee focused entirely on computational fluid dynamics (CFD) studies, for example, giving BDI a significant capability in air flow modelling and simulation. “Our newly formed CFD department was heavily involved in the design of a new type of afterburner blast deflector we recently installed for a military project in Japan,” Bergin says.

He explains that the company’s core range of jet blast deflectors are constructed entirely of carbon steel. However, it has also worked with other materials including stainless steel, aluminized steel, Galvalum and aluminium. “Our most recent development is a series of curved blast deflectors made entirely of fibreglass reinforced plastic,” Bergin reports.

“These lightweight deflectors are ideal for use at runway ends, particularly if an installation is required in front of an instrument landing system’s localised antenna.” BDI’s first fibreglass deflector was installed in late 2013 at T F Green Airport in Providence, Rhode Island.

Chicago takes a lead

GREs and blast deflectors can play their part in airside noise mitigation, but airports also have to consider the wider picture and the impact of aircraft noise on local communities caused not just by engine start-ups, taxiing, take-offs and landings, but also that created by aircraft moving along flight paths above residential communities.

Numerous airports are doing all they can to mitigate that wider noise footprint and, in recent decades, US and European gateways have taken a lead on the issue thanks at least in part to the pressure exerted by vociferous local communities. In North America, the Chicago Department of Aviation (CDA), responsible for Chicago O’Hare International Airport, has been particularly prominent in developments in this area and was one of the first North American airports to build modern GRE (which was designed and installed by BDI).

Moreover, CDA also provides an interesting case study today because of its massive O’Hare Modernization Program (OMP), a huge redevelopment of the gateway that represents one of the largest airport construction projects in the US and one which has led to significant changes in flight patterns around the facility; and this, of course, has meant changes in the levels aircraft noise heard on the ground and, consequently, complaints from some localities experiencing heightened noise levels.

It was an issue well anticipated by the airport and by CDA, which has a long history of sustained noise mitigation effort, Indeed, notes assistant commissioner for environment Aaron Frame, O’Hare has had an office devoted to just this issue for 30 years and it remains an “active, vibrant programme”. The airport’s ‘Fly Quiet’ strategy, in place since 1997, has particularly targeted noise mitigation at night, and it is an effort that is constantly under review and reassessment, he points out.

Key to recent efforts to deal with OMP-related challenges and the longer term issues relating to aircraft noise has been ongoing liaison with airlines and air traffic control to choose the best possible flight paths in order to minimise the noise impact on local residential areas. This has been supported by a vigorous outreach programme of interaction with those communities to hear their concerns and to try to deal effectively with them.

Ongoing efforts to provide sound insulation for schools and homes – partially funded by airport revenues and partly from Federal Aviation Administration (FAA) grants – have proved very successful. As of late June this year, 121 local schools had had sound insulation installed, together with thousands of residential homes, and the project is generally ahead of schedule, Frame confirms.

Frequent roundtable discussions form key parts of the community outreach programme, while data on noise emissions is made available by CDA in regular reports. That data comes from a network of 32 permanently sited noise monitors around O’Hare, most of them having been introduced in the period between 1996 and 2000. Many of those monitors were manufactured by Lochard, a company subsequently bought out by Brüel & Kjaer (the rest were supplied by Larson Davis, another well-known name in acoustic measurement). CDA is currently going through a tender process for updating much of that equipment.

The data is supported by Airport Noise and Operations Monitoring System (ANOMS) software, also supplied by Brüel & Kjaer, and discussed below. O’Hare has been using the ANOMS product since 1996, Frame confirms, and – while O’Hare doesn’t yet offer a flight tracker system readily accessible to the general public in the way that an airport such as London Heathrow does – it is on the CDA agenda, he says.

O’Hare is amongst the busiest airports in the world. If you also factor in the ongoing reconstruction of the OMP and flights to and from the smaller Midway airport located not far from O’Hare, it is easy to see not only why the airspace around Chicago is extremely busy but also why complex flight path patterns are changing all the time. Clearly, then, there is bound to be a noise problem – and one whose impact on the ground is evolving all the time. It is the task of CDA to try to balance that challenge with the civic and economic benefits of the airports for which it is responsible.

“We still have a lot to deliver, but we are proud of our accomplishments,” Frame believes. With an office devoted to noise mitigation in place for over three decades and a policy of working with – not against – local communities on this issue, he is proud of what has been achieved by CDA.

Keep the noise down!

European gateways have also looked to work with local communities wherever they can. Maintaining good relations with noise-affected communities through strong, clear communication is regarded as absolutely vital by the best of them – getting the message through that the airport operator is doing all it can to minimise noise and the consequent impact on local regional centres.

The Netherlands’ Eindhoven Airport, for example, has committed itself to doing all it can to inform the local community about its operations and its noise measurements. As part of this effort, the gateway has helped in the creation of a website featuring WebTrak and WebTrak MyNeighbourhood, tools designed by the above-mentioned Brüel & Kjær, to provide communities with accurate information about the airport and answers to frequently asked questions, thereby hoping to offer a better understanding of airport operations.

Joost Meijs, CEO at Eindhoven Airport, notes: “Brüel & Kjær was selected for its long experience of airport noise management and our successful working relationship so far. Brüel & Kjær’s ANOMS and WebTrak represent the latest in available technologies and we are looking forward to using them to work more directly with our stakeholders.”

WebTrak MyNeighbourhood enables the public to investigate noise and flight information, including long-term trends and seasonal changes. Drill-down capabilities reveal further information about flights and noise – and WebTrak also provides an easy way for people to lodge complaints.

ANOMS was contracted by the gateway in April 2011 and replaced an earlier system that Brüel & Kjaer had in use at Eindhoven. “We’ve been monitoring noise at the airport for 14 years,” notes Brüel & Kjaer global product marketing manager Phil Stollery, adding that a particular challenge at Eindhoven is that the airport is a joint commercial/military airport.

“The company’s offerings go beyond the basics of monitoring noise at airports. They police an airport’s noise abatement rules, enabling (airport operators) to efficiently manage operations to minimise the noise impact. However, that is only half of the story. They present the noise impact in ways that communities, regulators and other stakeholders can understand, showing what has changed and long-term trends,” he explains.

Increasing pressure

Stollery believes that the pressure to lessen aircraft noise is increasing, but the nature of that pressure is changing somewhat too. “As growth returns to commercial aviation, we are finding demand increasing as concerns about impact develop. However, increasingly it’s not just about communities wanting to hear less aircraft noise. Particularly around large airports, there is an understanding of the need to balance the noise impact against the economic benefits that the airport brings to the region.

“Tools like WebTrak are part of how airports work together with communities, sharing information to help them understand how the airport operates and what this means for the noise. Innovative airports are working with communities to determine and trial new operating approaches.

“Airport noise management is maturing,” he argues. “Huge gains have been made in reducing the noise impact of individual aircraft over the last 50 years. Noise impact remains important, however, as there is a lot more air traffic and it is getting harder and harder to find ways to reduce the impact.

“Much of the innovation now lies in effective stakeholder engagement. The information airports provide about noise impact, and the ways in which they provide it, are developing to provide a much greater understanding of airport operations and correspondingly a higher degree of acceptance and tolerance,” Stollery adds.

Toronto’s Blastwall testimonial

Chris Stewart, manager, airside and infrastructure engineering at Toronto Pearson International Airport operator Greater Toronto Airports Authority (GTAA), explains the gateway’s thinking behind the acquisition of a fibreglass blast wall: “The location of the blast wall was such that it had to be placed in front of a localiser antenna array. Steel could not be used due to interference with signals. Fibreglass has no effect on the signals and has the required strength, so was an ideal choice.”

He continues: “The blast wall has functioned well (although) three years ago the fence had to be refinished due to surface degradation caused by the extreme environment.”

As to future requirements: “We would consider further fibreglass constructions in similar circumstances. Steel could also be considered if the location was not within the boundaries of the electronic zoning of sensitive equipment,” Stewart explains.

MAG opts for ANOMS

In another contract win for Brüel & Kjaer, the company confirmed in July that the UK’s Manchester Airports Group (MAG) has opted for its ANOMS 9 system to monitor and report on noise at MAG’s multiple airport sites at London Stansted, Bournemouth, East Midlands and Manchester itself.

The airports will employ WebTrak and WebTrak MyNeighbourhood, with noise monitoring terminals (NMTs) also deployed at the gateways.

“Through a recent tender process we examined new offerings from Brüel & Kjær and other companies, before finally deciding that Brüel & Kjær’s ANOMS 9 solution and new Type 3639 NMTs met all our needs,” explains Tim Walmsley, environment manager at Manchester Airport.