Blast Away; Aircraft Jet Blast Protection

Transpo Industries, Inc.

Blast Safe Transpo

As the demand for air transport grows, airport administrators are becoming adept at maximising the use of space. Room can usually be found for an extra car park, cargo village, baggage handling facility or terminal extension. But the increasing utilisation of what were greenfield sites has created a new problem: the need to protect against aircraft jet blast and ground run-up noise

"The more cluttered airports become, the more they need to protect people, vehicles and buildings from airport blast," emphasises Nick Smith, business manager aviation for IAC Airport Systems. "The blast from an aircraft breaking away (from its parking position) or taking off can blow a vehicle over, damage a building or injure a person."

"As airports expand, communities are growing closer," adds Mike Stenko, president of Transpo Industries. "Runways are close to each other, so there has to be protection." Aircraft are taxiing closer to public roads, car parks, office and industrial buildings and even housing, all of which need protection. Don Bergin, director of technical sales for Blast Deflectors, Inc (BDI), puts it another way: "High-velocity aircraft exhaust can potentially limit the use of areas on or near airports. By effectively deflecting blasts, airports create useable space."

Blast Protection from Transpo Industries

Most jet blast deflectors look like fences. In fact, the average passenger spotting one would assume it was designed for security. But although they can double as Air Operations Area (AOA) security fencing by mounting barbed wire on top, most blast deflectors have a very different aim. They work by channelling the blast upwards, above the height of people, vehicles and buildings. Determining exactly where a blast deflector is to be installed is key to its efficiency. They need to be placed between the aircraft parking area, runway or ground run-up site and whatever needs to be protected. Typical locations include along a perimeter road, whether it's a public road or one used for ground service equipment; between the runway and terminal building; in front of a baggage handling facility; adjacent to a car park; or at a designated run-up area. At La Guardia, New York, for example, the front bumpers of vehicles in one car park almost touch the aircraft as they taxi down the runway. They need protection from jet blast. La Guardia also introduced deflectors around the VIP area so that the public cannot see who is arriving at or leaving the airport.

Chicago's O'Hare installed a blast deflector around the main power plant supplying the airport to prevent not only blast, but debris from damaging the plant. Newark has used one to protect fuel loading areas. When considering where jet blast deflectors may be required, airport planners must bear in mind that aircraft can stop and start at any point while manoeuvring on the airfield, and the most significant jet blast hazard during taxi operations is the use of breakaway thrust to commence aircraft movement. During the planning and design stages of new taxiways, remote parking aprons and terminals, jet blast hazards must be carefully considered at all points of the aircraft path of movement. In addition to jet blast deflectors, BDI also offers a blast deflector designed for ground run-up. The most commonly used GRE (ground run-up enclosure) comprises a jet blast deflector surrounded by an acoustic barrier to minimise the noise impact.

"A ground run-up creates a local jet blast impact and a far-reaching acoustic impact," Bergin explains. "Our Stabile Flow GRE design can protect against both hazards. We are in the process of building two GREs in Asia for very different aircraft mixes, but with similar objectives: to protect the immediate area from jet blast and the surrounding area from jet blast."

Options

BDI has recently rolled out a moveable jet blast deflector designed primarily for airport construction sites or temporary applications. The need for protection varies on a construction site according to where the work is being carried out. "We have developed a new type of blast deflector that can be mounted on a concrete base that can be moved by forklift," Bergin notes. The first application for BDI's new portable deflector was installed at Oakland International Airport in June. Transpo Industries is also developing a moveable version of its product.

"Some large airports, especially those handling new larger aircraft, such as the A380, asked us to develop a jet blast fence on a moveable system so they could move it behind the aircraft, wherever it happens to be," says Stenko. "We're working on it." Transpo and BDI both offer vertical blast deflectors as an alternative to the traditional curved models. "With a curved model, a bit of rock blasted into it can ricochet against the fence and fall from the sky somewhere else," he explains. "That doesn't happen with a vertical fence. Vertical fences also take up less space."

New materials have been introduced for blast deflection, too. Galvanised steel has been most commonly used in blast deflection technology because of its high strength and corrosion resistance. As Stenko points out, if a bit of debris is blown against it, the blast fence will not be damaged or penetrated. Steel is sometimes covered with wadding to increase acoustic noise protection. But steel structures cannot be used in front of an Instrument Landing System (ILS) localiser due to signal interference. Instead, non-metallic deflectors are used as they are transparent to the localiser signals. Nor can steel blast walls be produced in a frangible version. Blast walls near runways have to be frangible in case the landing gear hits the top of them. So, in place of steel, fibreglass is used.

Airport Blast Protection

BlastWall Inc was the first company to produce a patented fibreglass blast wall, according to company president Peter Roston. "Toronto Pearson International had a problem in 1998 when it built a new runway as close to the road as could be," he says. "As it could not put a traditional steel, non-frangible blast wall there, it approached my late partner Mark Selkirk with a view to creating a fibreglass version. Not only can fibreglass be turned into a frangible blast wall, but radar signals can go through it, so it does not affect the ILS. It also needs little or no maintenance; Pearson's original fibreglass blast wall needed no attention until 2011." After extensive testing of different heights and spreads of blast walls, using different aircraft types, aviation authorities gave their permission for the fibreglass blast wall to be developed and sold commercially. BDI developed its version this year.

BlastWall now offers four patented fibreglass blast walls - two models, each available in frangible or non-frangible versions - and has just introduced a range of six steel blast walls. They all differ in height and the amount of force they can withstand. "A frangible blast wall withstands a force of 160kph," Roston explains, "whereas a non-frangible one can withstand forces up to 230kph." Aesthetics come into the equation, too. Some airports and civil aviation authorities require blast deflectors to be painted, while some want more attractive cladding such that the landside matches the surrounding architecture. "Quite a bit of science goes into designing jet blast deflectors," says Bergin. "We recently hired a full-time expert, educated to PhD level, in computational fluid dynamics, to help evaluate different blast deflector and GRE designs. This allows us to analyse the aerodynamic characteristics of new designs or specific projects and greatly enhances the capabilities of our research and department."

As indicated, blast deflectors come in a variety of size, shapes and materials. But in the increasingly competitive aviation world, if an airport doesn't have any yet, it may not be long before blast deflectors head the list of essential infrastructure investment.

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