Developing Improved Civil Aircraft Arresting Systems (2009) / Chapter Skim
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EMAS Nomenclature In general, the FAA advisory circular regarding EMAS provides latitude regarding the materials and construction methods that may be used; multiple EMAS designs could exist. At present, however, only one manufacturer has an approved EMAS design, which is the Engineered Arresting Developing Improved Civil Aircraft Arresting Systems 1
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When regulatory discussions are undertaken, the term will refer to the general requirements that pertain to the current and future passive arrestor systems. When clarification is required, qualifications such as "current EMAS," "current EMAS design," or "current EMAS technology" will be used to denote the ESCO product.
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Eight airports provided preparatory paving and installation costs for a total of 11 arrestors. By way of comparison, the cost design values according to FAA Order 5200.9 were based on five separate EMAS installations.
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Exit Speed Exit speed is how fast an aircraft is travelling when it rolls past the end of the runway. The advisory circular requires that an EMAS have a standard design exit speed of 70 knots (standard case)
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, 2. Aggregate foam arrestor concept (passive)
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Monolithic layups such as this have been used in building roof applications. Candidate 2: Aggregate Foam An aggregate foam arrestor concept was proposed.
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Aggregate foam material: microstructure (upper-left) , as a pile (upper-right)
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Figure S-7 Aggregate Foam Bed Cover Layer of Engineered Turf Arrestor Basin Figure S-5. Aggregate foam arrestor concept.
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Engineered aggregate arrestor concepts. Braking Unit Braking Unit Figure S-8.
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Category System Evaluation Approach Crushable material systems • Candidate 1: Glass foam • Candidate 2: Aggregate foam Displaceable material systems • Candidate 3: Engineered aggregate • Material testing • One-wheel bogey testing • Numerical modeling to develop tire/material response surfaces • Overall aircraft response evaluation using an aircraft suspension model Active systems • Candidate 4: Main-gear engagement active system • Extended paper study • Analytical spreadsheet model Table S-2. Summary of evaluation methods for candidates.
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. In order to compare the candidate systems' performance with these EMAS baseline cases, aircraft computer models for each were developed.
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The performance similarity of 0 100 200 300 400 500 600 700 Current EMAS Glass Foam Engineered Aggregate Aggregate Foam St op pi ng D is ta nc e (ft ) CRJ-200 B737-800 B747-400 Figure S-12.
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13 0 100 200 300 400 500 600 700 800 900 1000 Current EMAS Glass Foam Engineered Aggregate Aggregate Foam St op pi ng D is ta nc e (ft ) CRJ-200 B737-800 B747-400 D A TA N O TA VA IL AB LE Figure S-13.
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The glass foam material could be packaged in a manner similar to that of the current EMAS cellular cement or equipped with an alternative monolithic sealed top layer. Cost Comparison The relative costs for the current EMAS and the candidate systems are compared in Figure S-14 and Figure S-15, using survey cost assumptions and estimates from Order 5200.9, respectively.
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Its speed-dependent nature produces weaker multi-aircraft performance, which would require longer arrestor beds to obtain the same exit speed ratings. Active System Evaluation Results The main-gear engagement active system concept offered multiple advantages not available in passive surface-based arrestor beds.
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was 1.8 times higher than the predicted value, an update to the guidance document may be advisable. A review of aircraft overrun data led to a revised probability curve for aircraft overrun exit speeds.
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However, because the aggregate foam concept uses a novel crushable material and cover layer, the number of unknowns is greater. The arrestor materials require additional evaluation in order to produce high-confidence performance estimations.
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As with the aggregate foam, the materials to be used will require additional characterization in order to make high-confidence performance estimations. Overall, the combination of unknown factors and anticipated cost and performance improvements make it a moderate-risk/low-payoff concept.
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