The development of ditching and water impact design limits
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THE DEVELOPMENT OF DITCHING and WATER IMPACT DESIGN LIMITS. PRESENTED AT INT’L CABIN SAFETY CONFERENCE NOVEMBER 15-17, 2004 LISBON, PORTUGAL DYNAMIC RESPONSE INC. (DRI) FEDERAL AVIATION ADMINISTRATION (FAA-TC). SBIR WATER IMPACT PROGRAM. PHASE I Feasibility of Methodology PHASE II

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THE DEVELOPMENT OF DITCHING and WATER IMPACT DESIGN LIMITS

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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 15-17, 2004

LISBON, PORTUGAL

DYNAMIC RESPONSE INC. (DRI)

FEDERAL AVIATION ADMINISTRATION

(FAA-TC)


Sbir water impact program

SBIR WATER IMPACT PROGRAM

PHASE I

  • Feasibility of Methodology

    PHASE II

  • Perform Full Scale Tests, Model and Correlate

  • Model For Existing Scale Model Ditching test

  • Evaluate FAR27/29 Water/impact/Ditching Regulations & Compliance

  • Develop Preliminary Water impact Design Limits

    PHASE III

  • Develop Military Helicopter KRASH Models

  • Evaluate Correlation Techniques/Procedures

  • Develop Design Envelopes (DLE) - Water Impact/Ditching

  • Develop DLE Procedures

    --- Civil helicopters

    --- Military helicopters


Impact envelopes

IMPACT ENVELOPES


Significant questions

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?


Aspects of water impact and ditching

ASPECTS OF WATER IMPACT AND DITCHING

  • Kinematics Behavior

  • Overall response

  • Discrete location response

  • Failures

  • Design parameters

  • Seat-occupant performance/tolerance

  • Trends & relationships


Full scale water impact tests

FULL SCALE WATER IMPACT TESTS

1998 - 1999 Tests of UH-1H

Test S1

26 fps vertical

Test S2

28 fps vertical

39 fps longitudinal


Overall responses kinematic behavior

OVERALL RESPONSES & KINEMATIC BEHAVIOR


Floor acceleration

FLOOR ACCELERATION


Pressure response

PRESSURE RESPONSE


Floor pulse

FLOOR PULSE


Floor vertcal pulses ground water regulations

FLOOR VERTCAL PULSES – GROUND, WATER, REGULATIONS


Significant questions1

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?


Design considerations seat load limit

DESIGN CONSIDERATIONS-SEAT LOAD LIMIT

NO SEAT LOAD LIMIT

14.5G SEAT LOAD LIMIT

26 FPS VERTICAL WATER IMPACT


Design considerations ea oleo vs skid type gear

DESIGN CONSIDERATIONS – EA OLEO Vs. SKID TYPE GEAR

Kinetic energy

Floor pulse


Trends sea state vs calm sea

TRENDS –SEA STATE VS. CALM SEA


S2 s1 pressure trend comparison analysis vs test

S2/S1 Pressure Trend Comparison; Analysis Vs. Test


Ditching compliance

DITCHING COMPLIANCE


Ditching compliance procedures

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


Dle for water impacts

DLE for WATER IMPACTS


Dle ditching application

DLE-DITCHING APPLICATION


Krashsom hic results

KRASHSOM-HIC RESULTS


Dle considerations

DLE CONSIDERATIONS


Applicability to far 25 transport category aircraft

APPLICABILITY TO FAR 25; TRANSPORT CATEGORY AIRCRAFT

FAR 25, FAR 27 and FAR 29 HAVE:

  • Ditching Envelope

  • Seat Dynamic Test Requirements

  • Mass Item Retention

  • Acceptance Criteria

  • Compliance Procedures

  • Different Levels but Many Similarities


Summary

SUMMARY

  • SBIR Tests/Correlation and Applications

    - 2 Full Scale Water and 35 Scaled Ditching Tests

    - Aircraft Weights: 10,000 -20,000- 42600 lb. GTOW

    - Design Requirements & FAR Regulations

  • Development of Civil Design Limit Envelopes –

    - Occupant –Seat Integrity

    - Structural and Mass Retention Integrity

  • Development of Ditching and Water Impact Design Criteria and Procedures

  • Utilization of DLE to Evaluate Design Strength, Operational Conditions, Acceptance Criteria, and New Designs

  • Applicability of DLE Concept and Procedures to FAR25 Transport Category Airplanes


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