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145 700 600 Stopping Distance (ft) 500 400 CRJ-200 300 B737-800 200 B747-400 100 0 Current EMAS Glass Foam Engineered Aggregate Aggregate Foam Figure 13-1. Comparison of single-aircraft bed performance for all candidates: distance travelled in bed for full arrest assuming 70-knot exit speed. and aggregate foam beds would further obtain a 70-knot rating The engineered aggregate produced speed-dependent land- for the B737-800, while the engineered aggregate falls behind ing gear loads. This would typically require designs to hedge at only 63 knots. For the B747-400, none of the beds obtain a against overloading by under-designing them, resulting in full 70-knot rating; the aggregate foam leads at 56 knots and longer arrests than illustrated above. the engineered aggregate falls to below the minimum allow- The glass foam beds produced the most predictable and able speed at 39 knots. constant decelerations without speed dependence or por- Overall, the performance of the three concepts can be sum- poising effects. marized as: 13.3. Environmental Performance The aggregate foam concept provided the best overall Comparison mixed-fleet bed performance, showing the smallest spread in arrestor performance for the three aircraft. However, the From an environmental performance standpoint, all three bed design must be correctly specified to prevent oscillatory alternatives appear likely to offer superior performance to porpoising behavior. the current EMAS technology. The environmental perfor- 1000 900 800 Stopping Distance (ft) 700 DATA NOT AVAILABLE 600 500 CRJ-200 400 B737-800 300 B747-400 200 100 0 Current Glass Foam Engineered Aggregate EMAS Aggregate Foam Figure 13-2. Comparison of multi-aircraft bed performance for all candidates: distance travelled in bed for full arrest assuming 70-knot exit speed.