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60 CHAPTER 8 Experimentation Overview This chapter briefly summarizes the overall experimenta- promise of resolving the question of predictable arresting tion process followed for the candidate evaluations. It pro- performance. vides context for the interrelationships and commonalities of The active system approach required a feasibility study to Chapters 9 through 14, which document the evaluations on a determine its merit. As such, a small 10% allotment was ded- system-by-system basis. icated to completing a more detailed paper/analytical study. 8.1. Scope and Emphasis 8.2. Evaluation Process The research funding did not support full-scale testing on a The evaluation method for the passive systems was com- broad enough basis to be meaningful for the effort. Because the posed of (1) modeling and (2) physical testing. Figure 8-2 illus- experimentation phase was intended to compare the most trates a simplified version of the modeling and testing approach. promising alternatives to the current system, and because there The materials underwent laboratory testing and small- were several to evaluate, a modeling-centric approach was scale one-wheel bogey tests. The data was used to construct adopted. Within this approach, various physical tests were per- models and undertake a more substantial array of simula- formed in order to characterize the materials involved and to tions for the tirearrestor interface. These simulations pro- provide a basis for calibrating high-fidelity computer models vided data for a wide range of dynamic cases with various of the systems. The models were then used to assess the per- speeds of travel, tire sizes, and bed dimensions. formance of the arrestor concepts in different configurations The simulation data was collected into databases, which and for different aircraft. were referenced by the APC (Appendix G). The APC was The candidate systems and evaluation methods are given used to simulate the aircraft suspension response to different in Table 8-1. As the table indicates, the passive systems shared arrestor bed designs. It predicted landing gear loads, the effects similar evaluation approaches, but the active system differed. of material property alterations, and overall arresting perform- The experimentation does not include the current ESCO cel- ance. The viability of each alternative was assessed based on the lular cement material. Comparisons between different candi- best-case performance obtained through the APC simulations. dates and the current EMAS technology were made based on Early in the research effort, best-case EMAS arrestment pre- overall aircraft deceleration. diction data was provided for three aircraft from different size The majority of the experimentation emphasis was placed on regimes: the CRJ-200, B737-800, and B747-400 (Figure 8-3). the passive systems (Candidates 1 through 3), which included In order to compare the candidate systems' performance with testing and high-fidelity modeling. Figure 8-1 shows the relative these EMAS baseline cases, aircraft models for each were emphasis given to each of the areas. developed for use in the APC. These three aircraft are cited Crushable material technologies were emphasized most through the evaluation chapters. because they have a proven track record; finding a similar material solution with better life-cycle performance would 8.3. Order of Discussion provide a useful alternative in the near-term. Aggregate systems have historically experienced a dis- The candidates were numbered per the sequence of discus- crepancy of acceptance, seeing use in the UK but not within sion from Chapter 7, which was ordered in accordance with the U.S. The evaluation approach outlined herein offers the the mechanical classification of the arrestor systems. The

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61 Table 8-1. Summary of evaluation methods for candidates. Category System Evaluation Approach Crushable Candidate 1: Glass foam Material testing Material Systems Candidate 2: Aggregate foam One-wheel bogey testing Numerical modeling to Displaceable Candidate 3: Engineered aggregate develop tire/material Material Systems response surfaces Overall aircraft response evaluation using an aircraft suspension model Active Systems Candidate 4: Main-gear engagement Extended paper study active system Analytical spreadsheet model Active Systems 10% Engineered Glass Foam and Aggregate Aggregate Foam System Systems 34% 56% Figure 8-1. Relative emphasis for different systems during experimentation phase. Predict Tire- Predict Aircraft Develop Arrestor Interface Arrestment Characterize Loads Performance Computer Models Materials Through to Match Test Create Utilize Arrestor Testing Data Performance Prediction Code Databases (APC) Figure 8-2. Simplified diagram of modeling and testing approach.

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62 B747-400 CRJ 200 MTOW = 875,000 MTOW = 51,000 88 ft B737-800 MTOW = 174,200 230 ft 130 ft Figure 8-3. Three evaluation aircraft for the effort. (MTOW = Minimum takeoff weight.) crushable concepts were discussed first, followed by the engi- These two candidates serve as bounding mechanical cases; neered aggregate and active systems. prior discussion of these concepts simplifies the subsequent However, in the detailed evaluation of the following chap- discussion of the aggregate foam concept. As such, aggregate ters, the sequence is altered. The glass foam and engineered foam is placed third (Chapter 11). aggregate concepts are discussed first, in Chapters 9 and 10.