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THE DEVELOPMENT OF DITCHING and WATER IMPACT DESIGN LIMITS

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). SBIR WATER IMPACT PROGRAM. PHASE I Feasibility of Hybrid and FEM Methodology

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THE DEVELOPMENT OF DITCHING and WATER IMPACT DESIGN LIMITS

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  1. 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)

  2. 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

  3. IMPACT ENVELOPES

  4. SIGNIFICANT QUESTIONS • Can modeling simulate /represent the significant aspects of full-scale impact and scale model ditching tests? • Can analytical modeling be an effective tool in the development of crash design criteria?

  5. ASPECTS OF WATER IMPACT AND DITCHING • Kinematics Behavior • Overall response • Discrete location response • Failures • Design parameters • Seat-occupant performance/tolerance • Trends & relationships

  6. FULL SCALE WATER IMPACT TESTS 1998 - 1999 Tests of UH-1H Test S1 26 fps vertical Test S2 28 fps vertical 39 fps longitudinal

  7. OVERALL RESPONSES & KINEMATIC BEHAVIOR

  8. FLOOR ACCELERATION

  9. PRESSURE RESPONSE

  10. FLOOR PULSE

  11. FLOOR VERTCAL PULSES – GROUND, WATER, REGULATIONS

  12. SIGNIFICANT QUESTIONS • Can modeling simulate /represent the significant aspects of full-scale impact and scale model ditching tests? • Can analytical modeling be an effective tool in the development of crash design criteria?

  13. DESIGN CONSIDERATIONS-SEAT LOAD LIMIT NO SEAT LOAD LIMIT 14.5G SEAT LOAD LIMIT 26 FPS VERTICAL WATER IMPACT

  14. TRENDS –SEA STATE VS. CALM SEA

  15. 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

  16. 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 TRENDS

  17. DITCHING COMPLIANCE

  18. 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

  19. 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

  20. CURRENT DLE CONSIDERATIONS;TAKE INTO ACCOUNT

  21. CURRENT WATER IMPACT DLE CONCEPT

  22. DLE-DITCHING APPLICATION

  23. KRASH/SOMR-HIC RESULTS

  24. 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

  25. 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

  26. The Fourth Triennial International Aircraft Fire and Cabin Safety Research Conference

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