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DRI THE DEVELOPMENT OF DITCHING and WATER IMPACT DESIGN LIMITS PRESENTED AT INT’L CABIN SAFETY CONFERENCE NOVEMBER 17, 2004 LISBON, PORTUGAL DYNAMIC RESPONSE INC. (DRI) FEDERAL AVIATION ADMINISTRATION (FAA-TC)
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DRI SBIR WATER IMPACT PROGRAM PHASE I Feasibility of Hybrid and FEM Methodology PHASE II Perform Full Scale Tests, Model and Correlate (KRASH and MSC/DYTRAN) KRASH Model For Existing Scale Model Ditching test Evaluate FAR27/29 Water/impact/Ditching Regulations & Compliance Develop Preliminary Water impact Design Limits With KRASH PHASE III Develop Military and Civil Helicopter KRASH Models Evaluate Correlation Techniques/Procedures Develop Design Criteria & Design Envelopes (DLE) & Procedures- Using KRASH --- Ditching and Water Impact --- Civil helicopters --- Military helicopters Recommend Ditching and Water Impact Design Criteria
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DRI IMPACT ENVELOPES
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DRI SIGNIFICANT QUESTIONS 1.Can modeling simulate /represent the significant aspects of full-scale impact and scale model ditching tests? 2.Can analytical modeling be an effective tool in the development of crash design criteria?
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DRI ASPECTS OF WATER IMPACT AND DITCHING Kinematics BehaviorKinematics Behavior Overall responseOverall response Discrete location responseDiscrete location response FailuresFailures Design parametersDesign parameters Seat-occupant performance/toleranceSeat-occupant performance/tolerance Trends & relationshipsTrends & relationships
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DRI FULL SCALE WATER IMPACT TESTS 1998 - 1999 Tests of UH-1H Test S1 26 fps vertical Test S2 28 fps vertical 39 fps longitudinal
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DRI OVERALL RESPONSES & KINEMATIC BEHAVIOR
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DRI FLOOR ACCELERATION
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DRI PRESSURE RESPONSE
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DRI FLOOR PULSE
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DRI FLOOR VERTCAL PULSES – GROUND, WATER, REGULATIONS
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DRI SIGNIFICANT QUESTIONS 1.Can modeling simulate /represent the significant aspects of full-scale impact and scale model ditching tests? 2.Can analytical modeling be an effective tool in the development of crash design criteria?
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DRI DESIGN CONSIDERATIONS- SEAT LOAD LIMIT 26 FPS VERTICAL WATER IMPACT NO SEAT LOAD LIMIT 14.5G SEAT LOAD LIMIT
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DRI TRENDS – SEA STATE VS. CALM SEA
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DRI S2/S1 Pressure Trend Comparison; Analysis Vs. Test Resultant Velocity S1 Test = 26 FPS S2 Test = 48 FPS S2/S1 Velocity Ratio 1.85 S2/S1 KE Ratio 3.41 3.41
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DRI TRENDS Correlation Sea State Levels S2/S1 Test Levels -Pressure -Acceleration -Transfer Function (Accel. to Pressure) -Filter Levels Design Envelopes Panel Failure Floor Acceleration Mass Item Response Occupant-Seat Response VS. -Panel Strength -Pitch Attitude -Seat Load Limit -Velocity Profile -Sea State
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DRI DITCHING COMPLIANCE
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DRI DITCHING COMPLIANCE PROCEDURES Scale Model Testing - rigid, deficient, misleading, costly Similarity to Existing Designs - questionable basis Pressure Calculations - static flotation analysis Vertical Load Factor Calculations - stall speed, no sink velocity Procedures - under-estimate pressure & acceleration
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DRI What Exists – Relative to Ditching Assessment Capability Inadequate evaluation and compliance procedures KRASH modeling features that address significant issues, i.e. trends, sea state, nose-over, failures Analysis predictable within a level of acceptance Analysis simulation time efficient
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DRI CURRENT DLE CONSIDERATIONS; TAKE INTO ACCOUNT
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DRI CURRENT WATER IMPACT DLE CONCEPT
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DRI DLE-DITCHING APPLICATION
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DRI KRASH/SOMR-HIC RESULTS
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DRI APPLICABILITY TO FAR 25; TRANSPORT CATEGORY AIRCRAFT FAR 25, FAR 27 and FAR 29 HAVE MANY SIMILARITIES: Ditching Envelope Seat Dynamic Test Requirements Mass Item Retention Acceptance Criteria Compliance Procedures
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DRI SUMMARY Balanced Test, Analysis, Design SBIR - F/S WI and Scaled Ditching Tests - Civil and Military Rotorcraft Models/Correlation - FAR 27/29 and Military Design Specifications/Compliance Development of Ditching Criteria and Design Limit Envelopes Based On; - Occupant –Seat-Restraint System Integrity - Structural and Mass Retention Integrity - In Excess of 300 Simulations Performed Applicability of DLE to Evaluate Design Strength, Operational Conditions, Acceptance Criteria, New Designs, FAR 25, 27, 29 End Product Goal- Recommended Ditching and WI Design Criteria, DLE and Procedures
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DRI
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