FAQ
- What is an EMAS?
- What are the main benefits of an EMAS installation?
- How is it produced?
- What are the site preparation requirements for an EMAS?
- How is an EMAS installed?
- How long does a program take?
- What is the contracting process for an EMAS?
- How big is an EMAS?
- Is EMAS applicable to military arresting gear requirements?
- What are the performance capabilities?
- How can ESCO predict the performance?
- What is the cost of an EMAS?
- How long does it take to repair an arrestor bed after an arrestment?
- What is the repair procedure after an arrestment?
- How is ILS affected by EMAS?
- Is it necessary to remove snow from the EMAS? How is it accomplished?
- What is the normal maintenance?
- To what extent can emergency and maintenance vehicles and personnel traverse the EMAS?
What is an EMAS?
ESCO's Engineered Material Arresting System (EMAS) is an evolution of a "soft ground arresting system" consisting of a crushable cellular cement material installed on the runway overrun to decelerate an aircraft in an emergency. FAA Policy Order 5200.9 identifies EMAS as equivalent to a 1,000-foot long RSA and provides guidelines on comparing various runway safety area (RSA) improvement alternatives to the EMAS option.
When an aircraft is unable to stop on the active runway, the aircraft rolls into the EMAS arrestor bed, and is decelerated by the loads applied to the aircraft landing gear as the aircraft wheels travel through the EMAS. The depth of the EMAS gradually increases as the aircraft travels into the arrestor bed, providing increasing deceleration when required by heavier or faster aircraft. Aircraft runout distance will be determined by the aircraft size, weight, speed and bed configuration.
ESCO's EMAS is a cost-effective way of improving safety where runway safety area distance is limited by site conditions. The range of aircraft operating at each airport and available overrun distance on each runway are accommodated by varying bed dimensions and material properties.
Engineered Arresting Systems Corporation has developed the cellular cement material specifically for this application, and has developed machinery, ingredients and patented processes enabling ESCO to control properties of strength, density and the resulting performance within much narrower tolerances than previously possible.
(top)What are the main benefits of an EMAS installation?
Besides the benefit of being AIP-eligible and meeting Part 139 requirements, ESCO's EMAS provides a reliable and predictable capability to stop an aircraft before reaching an existing hazard (road, railroad, waterway, steep embankment, etc.) and is equally effective in doing so in dry and non-dry surface conditions. The system is environmentally friendly since it can be installed on the existing runway safety area. It also negates the loss of any needed operational runway as is required by other safety area enhancement options such as shortening the runway, or imposing declared distances. In fact, EMAS may free up additional RW length on runways with more than 600 feet of RSA. Finally, it minimizes runway shutdown after an overrun as well as the airport's and airline's liability in overrun incidents.
ESCO believes that EMAS can provide further safety enhancement even in areas where there are adequate RSA available. This is particularly true in situation where there is a need to protect against a high level of danger for an overrunning aircraft REGARDLESS of available RSA length (into rivers, buildings, highways/rails, over cliffs, etc.). We have already seen some airports realizing the benefits of having both EMAS and a full RSA.
(top)How is it produced?
The arrestor bed is produced as pre-cast blocks. A factory installed jet blast resistant block protection system is applied to the raw blocks to enhance durability and protect against the effects of aircraft jet blast. Blocks that pass the stringent quality test limits established by the FAA are then transported to the runway safety area to be installed.
(top)What are the site preparation requirements for an EMAS?
The safety area is graded for drainage and longitudinal slope, adjusted if necessary, based on performance modeling of aircraft. The safety area is then paved (strength sufficient to support a rolling aircraft without deformation, not runway strength), from the runway end to the back of an EMAS. A concrete beam is constructed at the location determined from the ESCO computer model to be the best for the front of the arrestor bed. The length and width of the paved area are based on the arrestor bed size and location, also determined by the ESCO computer modeling. The bed is located to minimize the handwork required during installation where blocks are cut to fit around lights. Any lights which will be in the EMAS arrestor bed are modified to 2-points of frangibility. Normally, electrical utilities requiring regular access are moved outside the bed footprint. Any special drainage issues are accommodated.
(top)How is an EMAS installed?
After the site has been prepared, blocks are placed using forklifts with special clamping attachments, then pushed tightly against the neighboring blocks in the bed. Then a grid is marked to outline block locations. The block joints are then caulked and additional coats of water-resistant paint are applied to seal the bed and prevent weather damage.
(top)How long does a program take?
A typical program will vary considerably depending on the size of the arrestor bed, and the amount of site preparation work required. Once the design is completed, it typically would take about three to four months to produce and install an EMAS on one overrun safety area. The actual installation would typically take 4-6 weeks after site preparation is completed, depending on the bed size.
(top)What is the contracting process for an EMAS?
The airport selects a design consultant—with requirement that ESCO be part of design consultant's team—to do computer performance modeling, design the arrestor bed configuration, and provide technical support on the related civil design issues.
Most airports contract directly with ESCO as a material supplier to provide blocks and installation support (installation materials and technical support during installation). The airport then through competitive bid selects a contractor to perform the site preparation and arrestor installation. This is the lowest-cost and lowest-risk contracting method.
Design-build is another option.
(top)How big is an EMAS?
The arrestor bed is the width of the runway, plus 16 to 24 feet for the stepped sides (to facilitate ARFF vehicle access and passenger egress), depending on the maximum depth of bed material. EMAS includes a paved rigid ramp (i.e. setback), usually 75 feet long, in front of the arrestor bed. If sufficient safety area is available, a longer setback is normally used to provide the maximum performance possible.
(top)Is ESCO's EMAS applicable to military arresting gear requirements?
Yes, particularly for transport/cargo planes, or at joint civil/military airfields. For fighter planes, a higher level of deceleration performance is available from ESCO's mechanical arresting systems.
(top)What are the performance capabilities?
ESCO's EMAS performance can be tailored to customer requirements, available overrun distance, aircraft mix, etc. Performance is varied by increasing depth and length of bed, and variations of bed material strength.
Based on the FAA Advisory Circular (AC) for EMAS, the design goal is 70 knots runway exit speed, including the effects of deceleration on the paved portion of the EMAS in front of the arrestor bed. Contact ESCO for preliminary performance capability information. Charts in the AC are optimized for each aircraft and provide a very rough estimate.
If a customer has an identified requirement, a site survey, or site drawings (primarily focused on overrun distance available for EMAS), information on aircraft mix, and customer requirements would be used to make a preliminary design. An estimate of predicted bed performance would then be provided from this preliminary design at no cost to the airport or consultant. If the project moves to the design stage, ESCO design support will be provided for a fee. Request Performance Information
(top)How can ESCO predict the performance?
ESCO has a complex computer model to predict aircraft loads and arrestment capabilities. Over 10 years of R&D, aircraft testing, and actual emergency arrestments have validated the accuracy and reliability of this model.
ESCO's patented materials test method ensures that ESCO's EMAS blocks meet stringent FAA requirements. Coupled with our proprietary modeling computer, which validates the effect of the EMAS on aircraft, ESCO has the capability to make general performance predictions about the EMAS product.
(top)What is the cost of an EMAS?
Costs for EMAS will vary greatly depending on the condition of the existing overrun, mix of aircraft to be controlled and available runout distance, cost and availability of support labor and on-site storage space available at the airport. In particular, site preparation requirements can also have a large impact on price.
(top)How long does it take to repair an arrestor bed after an arrestment?
Damaged material would be removed and replaced. In addition to aircraft wheel rut damage, any damage caused by fire/rescue vehicles would have to be replaced. The duration of the repairs will be related to the amount of material damaged. In the Saab 340 overrun at JFK airport in 1999, the repairs took only 12 working days to accomplish.
The runway remained open between the time the aircraft was extracted from the safety area and the time the repairs were completed. After an arrestment (once the aircraft has been removed) but before the overrun arrestor has been repaired, the FAA has stated that airports may reopen runways. A NOTAM would be issued stating the EMAS is out of service.
The FAA Advisory Circular for EMAS includes a design requirement that an EMAS can be repaired within 45 days after an overrun arrestment.
(top)What is the repair procedure after an arrestment?
Damaged EMAS material is removed with front-end loaders and discarded. The aircraft is extracted (in the JFK arrestment, this was done using two tugs and straps attached to each main landing gear to pull the aircraft out backwards). New precast blocks are then installed and finish coats applied.
Repair costs would normally be paid for by the insurance of the party responsible for inflicting damage to the EMAS system.
(top)How is ILS affected by EMAS?
Tests by the FAA have indicated no adverse effects. (See item 16 for effects of snow accumulation.)
(top)Is it necessary to remove snow from an EMAS? How is it accomplished?
Snow on the pavement leading to the arrestor bed should be handled in the same manner as snow on the runway, so as to provide maximum predictability and braking on the paved area. Snow removal from the arrestor bed is usually only necessary if large annual accumulations will build up, obscuring approach lights, or affecting the ILS.
If a large, asymmetrical snow accumulation occurs on one side of the bed, it may affect the ILS and the snow will have to be removed.
Snow would not be expected to have a substantial effect on performance, but to prevent excessive buildup; an airport may want to keep EMAS clear of snow. To accomplish this, a special vehicle is required, which is eligible for federal (AIP) funding as part of an EMAS project. This vehicle, which is a tracked vehicle to provide very low surface pressure on the arrestor bed, uses a snow blower. It was first used at the Minneapolis-St. Paul International Airport EMAS during the winter of 1999/2000. It was found to work well, and did not damage the arrestor bed surface. If large accumulation of ice due to melting/freezing snow is expected, removal of snow is recommended.
(top)What is the normal maintenance?
Normal maintenance consists of maintaining the protective surface coatings. This would include painting and caulking as needed, which can be performed by airport maintenance personnel or by ESCO under an optional maintenance agreement. Proper maintenance will protect the underlying arrestor bed blocks from the environment, keeping excessive moisture out and prolonging the life of the system. In order to maintain durability, repaint of the entire bed may be required every 3 to 5 years.
An arrestor bed should also be inspected regularly. ESCO recommends weekly drive-by inspections as well as a monthly walk of the bed. Any visible damage to the surface coatings should be repaired immediately to maintain durability. During the first year, ESCO will perform quarterly inspections at no cost to the airport.
(top)To what extent can emergency and maintenance vehicles and personnel traverse the EMAS?
ARFF vehicle maneuverability on ESCO's EMAS arrestor beds was demonstrated in several tests at the FAA Technical Center. However, non-emergency use on the bed by ARFF vehicles should be avoided since the tires will leave ruts. Similarly, access on the bed by maintenance vehicles (other than specially equipped snow removal equipment mentioned above) should be avoided. EMAS site preparation includes paving around the perimeter of the bed to allow vehicles to drive around the bed for inspections and maintenance. Maintenance and other authorized personnel can walk on the arrestor bed without damaging the surface.
(top)