What is a Jet Blast Barrier or Deflector?
Airline operators face a perpetual quandary. They need to maintain a safe distance from buildings and homes but also need to be close enough to serve them. Airfields far from people make no sense, especially commercially, but operating as close to customers as possible is a delicate balancing act.
The jets of a typical large aircraft at just 40% power generate 120mph wind 200 feet to its rear. That’s a lot of air, heat and noise – unsurprisingly it creates problems. Pilots have to abide by strict rules when taxiing but that can lead to departure and arrival delays. The rules are by no means fool-proof; accidents inevitably happen and lighter aircraft, trees, buildings, vehicles and sometimes people fall victim.
A NASA survey shows that only half of jet blast accidents happen where you might expect them – on congested ramps and parking areas. The other half happen in areas where operators are more complacent. Weather conditions add an element of unpredictability and gusts change direction by bouncing off hard surfaces.
Engines undergoing testing and maintenance pose particular hazards. During a test, engines have to be powered up fully so regardless as to where they are conducted, controlling jet wash and noise is a major challenge.
Jet Blast Deflectors
Jet blasts pose three main problems – heat, noise and force – so a barrier has to provide a threefold solution. But there are other crucial parameters. To be practical and cost-effective, they have to be easy to assemble, to adjust in situ, and to relocate. They must also, of course, be robust and able to catch flying debris without themselves being damaged.
In some contexts, such as engine testing, they also need to be see-through (visibility through barriers is an CAA recommendation). Crude concrete walls provide limited solutions and a range of new problems, including reflected sound and variable wind conditions. Designing jet blast barriers for effective airfield solutions is a specialised skill.
As you would imagine, aerodynamics plays a major part in their design. Their materials and construction must either dissipate sound and airflow or deflect it in a controlled direction. In practice, most barriers seek to do both, while providing a physical shield against heat, dust and debris.
The ideal barrier provides protection from all jet wash hazards in a single unit, but airport space is often an additional consideration. Some are therefore designed with flexibility of location and can be moved and positioned to suit weather conditions, accessibility and aircraft types.
The Noise Challenge
In the modern world, the acoustic performance of barriers is particularly important. Noise mitigation regulations and legislation are becoming ever stricter. Wise operators understand that they need to ensure their investments are future-proof in that respect. Proposed new or expanded airfields need to think the same way before, rather than after their planning applications are submitted.
Cast concrete walls are hard to remove after you realise your mistake. They also squander land, defeating the value of an expansion. Nor is concrete an environmentally friendly material. The lightweight materials used in modern jet blast deflectors can be more effective than inches of concrete, with none of its disadvantages.
Because they are constructed from prefabricated components, they can be assembled and disassembled quickly, providing enormous versatility and flexibility of application. IAC Acoustics range of jet blast barrier solutions for airports ensures we can support the safe working practices and changing requirements of airports across all likely use scenarios.
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