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60 This chapter briefly summarizes the overall experimenta- tion process followed for the candidate evaluations. It pro- vides context for the interrelationships and commonalities of Chapters 9 through 14, which document the evaluations on a system-by-system basis. 8.1. Scope and Emphasis The research funding did not support full-scale testing on a broad enough basis to be meaningful for the effort. Because the experimentation phase was intended to compare the most promising alternatives to the current system, and because there were several to evaluate, a modeling-centric approach was adopted. Within this approach, various physical tests were per- formed in order to characterize the materials involved and to provide a basis for calibrating high-fidelity computer models of the systems. The models were then used to assess the per- formance of the arrestor concepts in different configurations and for different aircraft. The candidate systems and evaluation methods are given in Table 8-1. As the table indicates, the passive systems shared similar evaluation approaches, but the active system differed. The experimentation does not include the current ESCO cel- lular cement material. Comparisons between different candi- dates and the current EMAS technology were made based on overall aircraft deceleration. The majority of the experimentation emphasis was placed on the passive systems (Candidates 1 through 3), which included testing and high-fidelity modeling. Figure 8-1 shows the relative emphasis given to each of the areas. Crushable material technologies were emphasized most because they have a proven track record; finding a similar material solution with better life-cycle performance would provide a useful alternative in the near-term. Aggregate systems have historically experienced a dis- crepancy of acceptance, seeing use in the UK but not within the U.S. The evaluation approach outlined herein offers the promise of resolving the question of predictable arresting performance. The active system approach required a feasibility study to determine its merit. As such, a small 10% allotment was ded- icated to completing a more detailed paper/analytical study. 8.2. Evaluation Process The evaluation method for the passive systems was com- posed of (1) modeling and (2) physical testing. Figure 8-2 illus- trates a simplified version of the modeling and testing approach. The materials underwent laboratory testing and small- scale one-wheel bogey tests. The data was used to construct models and undertake a more substantial array of simula- tions for the tireâarrestor interface. These simulations pro- vided data for a wide range of dynamic cases with various speeds of travel, tire sizes, and bed dimensions. The simulation data was collected into databases, which were referenced by the APC (Appendix G). The APC was used to simulate the aircraft suspension response to different arrestor bed designs. It predicted landing gear loads, the effects of material property alterations, and overall arresting perform- ance. The viability of each alternative was assessed based on the best-case performance obtained through the APC simulations. Early in the research effort, best-case EMAS arrestment pre- diction data was provided for three aircraft from different size regimes: the CRJ-200, B737-800, and B747-400 (Figure 8-3). In order to compare the candidate systemsâ performance with these EMAS baseline cases, aircraft models for each were developed for use in the APC. These three aircraft are cited through the evaluation chapters. 8.3. Order of Discussion The candidates were numbered per the sequence of discus- sion from Chapter 7, which was ordered in accordance with the mechanical classification of the arrestor systems. The C H A P T E R 8 Experimentation Overview
61 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 8-1. Summary of evaluation methods for candidates. Active Systems 10% Engineered Aggregate System 34% Glass Foam and Aggregate Foam Systems 56% Figure 8-1. Relative emphasis for different systems during experimentation phase. Characterize Materials Through Testing Develop Computer Models to Match Test Data ⢠Create Performance Databases Predict Tire- Arrestor Interface Loads Predict Aircraft Arrestment Performance ⢠Utilize Arrestor Prediction Code (APC) Figure 8-2. Simplified diagram of modeling and testing approach.
crushable concepts were discussed first, followed by the engi- neered aggregate and active systems. However, in the detailed evaluation of the following chap- ters, the sequence is altered. The glass foam and engineered aggregate concepts are discussed first, in Chapters 9 and 10. These two candidates serve as bounding mechanical cases; prior discussion of these concepts simplifies the subsequent discussion of the aggregate foam concept. As such, aggregate foam is placed third (Chapter 11). 62 88 ft 130 ft 230 ft B747-400 MTOW = 875,000 CRJ 200 MTOW = 51,000 B737-800 MTOW = 174,200 Figure 8-3. Three evaluation aircraft for the effort. (MTOW = Minimum takeoff weight.)
