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Design

How is the greenEMAS® designed?
The performance and design of a greenEMAS® is tailored to the specific runway and airport. A detailed performance report will be compiled that takes into account the fleet mix and available area for an EMAS for a specified runway. Upon receiving detailed fleet mix data, aircraft type, number of operations, and other relevant information, we model a greenEMAS® that maximizes stopping performance for the specific fleet.

How does the greenEMAS® work?
The greenEMAS® works by absorbing the energy of the aircraft through the crushing of the bed components. The main material responsible for this energy absorption is the foamed silica aggregate. This, combined with the top CLSM (Controlled Low Strength Material) and MMA (Methyl Methacrylate) layers, produce drag on the landing gear load, reducing the speed of the aircraft.

 

Design
How is the greenEMAS® constructed?

How is the greenEMAS® constructed?

  • The greenEMAS® is built on site. It requires a paved base, capable of supporting the specific fleet mix.
  • Once the base is prepared, the anchoring and geogrids are installed. The layout and spacing of the anchoring and geogrid are tailored to meet the requirements for jet-blast resistance for the individual fleet mix.
  • The foamed silica is poured in place between the geogrids. It is compacted and leveled to the final grade.
  • Geofabric is used to cover the foamed silica before application of the CLSM.
  • After the initial curing of the CLSM the bed is ready for use and the runway can be opened.
  • Upon completion of the CLSM curing, application of the MMA top coating can be done. The MMA top coating is a multi layer system that is used to coat the entire EMAS, protecting it from the environment.

 

How long does it take to install the greenEMAS®?

The installation can be completed in a relatively short period of time. Depending on airport requirements the greenEMAS® can be installed in parts over several nights, or during a complete runway closure. The first installation at Chicago Midway International Airport was completed mainly in 56 hrs. Prior to the closure the existing ESCO bed was removed and anchors for the geogrids were set.

Where is the material stored?
The material stored in the largest quantity prior to construction is the foamed silica aggregate. This material is shipped in bulk and can be stock piled in the open air as it’s not susceptible to the elements. The only material that has temperature restrictions in regards to storage is the MMA.  There are limits on both the minimum and maximum temperatures that some of the components can be stored at.  Certain components are also moisture sensitive and need to be stored in a dry area until used. The other materials that make up the bed are not sensitive to the elements or temperature. After installation, a small quantity of materials can be stored on site to facilitate rapid repairs.


What type of equipment is needed for construction?

What type of equipment is needed for construction?

The greenEMAS® is constructed using normal construction equipment. The foamed silica can be transported to the site in dump trucks and placed using numerous methods. Grading and compacting of the foamed silica is completed using tracked construction equipment with a ground pressure of approx. 34 kPa (5 psi). The conveyor can then be used to place the CLSM. For MMA placement, a portable mixer is required.

Prevention of debris?
To prevent debris, once the placement of foamed silica is started, the area should not be exposed to jet-blast (departing) until the CLSM has been placed and has reached initial cure.

How long is the initial cure?
The initial cure (hardening) is largely based on the temperature and humidity. In the first installation at Chicago Midway International Airport, the temperature was between 1° and 7°C (35° and 45°F). This slowed the initial curing time to approximately 36 hrs. Initial cure is significantly reduced at higher temperatures.

Reparation of a greenEMAS®?
In the event of an incursion, the damaged section of the bed can be repaired without impacting other areas. This is one of the benefits of the product.
The repair procedure would have to be in five steps; 1) cutting back the damaged CLSM/MMA layer, 2) removal of crushed foam silica, 3) repair or replacement of the geogrid anchorage system, 4) placement of the new foamed silica, 5) patching of the CLSM and MMA.
Repair could be completed in a matter of hours plus the required initial cure on the CLSM. This requires having materials stored on site which greatly reduces the time that the EMAS is out of service.