# Presentation: 497207

## 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**
**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**
**	****   **

## IMPACT ENVELOPES

## 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

**Kinematics Behavior**
**Overall response**
**Discrete location response**
**Failures**
**Design parameters**
**Seat-occupant performance/tolerance**
**Trends & relationships**
** ****	**** **
**                      **

## 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

## FLOOR ACCELERATION

## PRESSURE RESPONSE

## FLOOR PULSE

## FLOOR VERTCAL PULSES – GROUND, WATER, REGULATIONS

## 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

**26 FPS VERTICAL WATER IMPACT**

**NO SEAT LOAD LIMIT**

**14.5G SEAT LOAD LIMIT**

## TRENDS –SEA STATE VS. CALM SEA

## 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**

## 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**
** **

## DITCHING COMPLIANCE

## 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**
** **

## 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**

## CURRENT DLE CONSIDERATIONS;TAKE INTO ACCOUNT

## CURRENT WATER IMPACT DLE CONCEPT

## DLE-DITCHING APPLICATION

## KRASH/SOMR-HIC RESULTS

## 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**

## 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**

## The Fourth Triennial International Aircraft Fire and Cabin Safety 

**The Fourth Triennial ****International Aircraft Fire and Cabin Safety **
**Research Conference**