Developing Improved Civil Aircraft Arresting Systems (2009) / Chapter Skim
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Pages 87-109
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From page 87... ...
During the assessment process, the following aspects were considered: • Dynamic behavior and energy absorption, • The degree of non-linearity of the landing gear loading and danger of failing the nose gear, • Performance in a short-landing situation that involves an aircraft touchdown inside the arrestor bed, • Applicability to arresting a wide range of aircraft types, • Vulnerability to ice crust formation in severe winter environments, and • Effect of a cover layer on the performance of the aggregate system.
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From page 88... ...
Aggregate Bed Aggregate Bed Cover Layer of Engineered Turf Aggregate Arrestor Concept 1: Open Bed Aggregate Arrestor Concept 2: Covered Bed Arrestor Basin Figure 10-2. Engineered aggregate arrestor concepts.
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From page 89... ...
Density and Dimension Measurements The density and dimensions of the engineered aggregate were measured for several hundred randomly selected aggregate particles. The particle size was found to follow a bounded normal distribution, with a diameter mean and standard deviation of 0.348 and 0.047 in., respectively.
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From page 90... ...
90 Figure 10-5. Hydrostatic test specimen for engineered aggregate pre-test (left)
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From page 91... ...
10.3.6. Environmental Tests Environmental tests were considered for the engineered aggregate and turf materials.
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From page 92... ...
This would likely result in 92 Figure 10-7. Overview pictures of engineered aggregate pendulum test setup.
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From page 93... ...
Post-test view of rut in engineered aggregate created by pendulum wheel. 0 200 400 600 800 1,000 1,200 Drag Avg Force (lbf)
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From page 94... ...
10.4.1.2. Size Distributions Section 10.3.1 discussed the particle size variation of the engineered aggregate, which followed a bounded normal distribution.
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From page 95... ...
The strut followed an arced path approximating that of the actual strut, with the same 1⁄2-diameter penetration depth into the arrestor bed. The wheel was set to a constant rotation rate approximating the observed rotation rate of the wheel on test video.
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From page 96... ...
96 Figure 10-12. Angle of repose simulation in EDEM.
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From page 97... ...
10.4.3.1. Arrestor Bed Models The arrestor bed models for the aircraft tire simulations were 8 ft wide and 25 ft long.
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From page 98... ...
10.4.3.2. Tire Models EDEM does not inherently support deformable tire modeling, which necessitated a different approach be taken than that of the LS-DYNA crushable arrestor models.
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From page 99... ...
Engineered aggregate pendulum model data comparison to test data. Clamp Motion Loose Turf Particles After Bonds Broken Figure 10-18.
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From page 100... ...
Tire library simplification for engineered aggregate arrestor models. Bed Depth Bottoming Depth Penetration Depth Figure 10-20.
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From page 101... ...
101 Tire Experimental Points Points Used Response RMS Error R 2 Drag 3.52% 0.999 H44 50 48 Vertical 4.20% 0.996 Drag 4.38% 0.998 H27 50 48 Vertical 8.38% 0.982 Drag 7.59% 0.993 R18 50 48 Vertical 5.00% 0.987 Table 10-3. Metamodel accuracy summary for engineered aggregate/turf arrestor bed.
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From page 102... ...
In actuality, the landing gear vertical strut member would sever the turf layer, preventing a complete tunnel. Additionally, bed designs of this relative depth would typically not be feasible because they would overload the landing gear.
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From page 103... ...
Single Aircraft CRJ-200 9.6 495 14.1 310 20 258 B737-800 13.5 462 19.5 361 20 287 B747-400 29.1 568 34.7 517 26 495 Table 10-5. APC predicted 70-knot stopping distances for engineered aggregate arrestor system.
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From page 104... ...
CRJ-200 70+ 335 B737-800 63 400 B747-400 39 400 Table 10-6. Fleet design arrestor bed for glass foam arrestor system.
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From page 105... ...
Landing Gear Forces - NOSE STRUT Nose Gear Drag Nose Gear Limit Load Nose Gear Ultimate Load
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From page 106... ...
Landing Gear Forces - NOSE STRUT Nose Gear Drag Nose Gear Limit Load Nose Gear Ultimate Load -50 400 0 50 100 150 200 250 300 350 -50 4000 50 100 150 200 250 300 350 -50 4000 50 100 150 200 250 300 350
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From page 107... ...
Estimated costs to establish engineered aggregate arrestor, 150 x 300 ft, assuming survey average costs for current EMAS, units of millions USD. Engineered Aggregate System Cost Category Lower Bound Upper Bound Current EMAS Site Preparation $ 0.34 $ 0.68 $ 0.68 Installation $ 3.61 $ 3.61 $ 3.83 Cost to Establish $ 3.95 $ 4.29 $ 4.50 Percent of EMAS 88% 95% Table 10-8.
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From page 108... ...
10.7.5. Full-Scale Testing A full-scale aircraft overrun test of an engineered aggregate arrestor bed is advisable because this concept represents a substantial departure from the current EMAS design in terms of mechanical loading and the materials used.
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From page 109... ...
The speed dependence of the engineered aggregate bed would require development of a new design criterion. Overruns exceeding the rated exit speed or short landings into the bed could result in overloads to the landing gear if the speed dependence is not considered in the design process.
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