the development of ditching and water impact design limits

DRITHE DEVELOPMENT OF DITCHING and THE DEVELOPMENT OF DITCHING and

WATER IMPACT DESIGN LIMITSWATER IMPACT DESIGN LIMITS

PRESENTED AT INT’L CABIN SAFETY PRESENTED AT INT’L CABIN SAFETY CONFERENCECONFERENCE

NOVEMBER 17, 2004NOVEMBER 17, 2004

LISBON, PORTUGALLISBON, PORTUGAL

DYNAMIC RESPONSE INC. (DRI)DYNAMIC RESPONSE INC. (DRI)FEDERAL AVIATION ADMINISTRATIONFEDERAL AVIATION ADMINISTRATION(FAA-TC)(FAA-TC)

DRISBIR 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

DRI

IMPACT ENVELOPESIMPACT ENVELOPESFigure 3-1 Ditching and Survivable Crash Environment

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U.S. Navy Helicopters, Land, 95th % SurvivableU.S. Navy Helicopters, Water, 95th % SurvivableU.S. Army Helicopters, 95th % Design RequirementCivil Rotorcraft, 95th % Land & Water Range - upperCivil Rotorcraft, 95th % Land & Water Range - lowerSBIR Test S1 - UH-1HSBIR Test S2 - UH-1HOsprey Ditching TestsFAA Civil Ditching RequirementsUH-1H Parametric Analysis Cases

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?

DRIASPECTS OF WATER IMPACT ASPECTS OF WATER IMPACT

AND DITCHINGAND 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

DRI

FULL SCALE WATER IMPACT TESTS 1998 - 1999 Tests of UH-1H

Test S126 fps vertical Test S2

28 fps vertical39 fps longitudinal

DRIOVERALL RESPONSES & KINEMATIC BEHAVIOR

OverallOverall S1 TestS1 Test S2 TestS2 Testcg vertical g ------------- 7 % 18 %avg. floor vertical g---- 10 % 19 %average panel psi ------ 8 % 4 % avg. floor longit. g -------- ----- 22 %

KinematicsKinematicscg velocity change------ 19 % -----cg vertical g ------------- 7 % 17.6 %cg longitudinal g ------- ----- 8.3 %water penetration -------- 8 % -------attitude ---------------------- flat pitch up

DRI

FLOOR ACCELERATION

a) FS 42

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KR mass 31

test S1 ch 01

test S1 ch 04

b) FS 155

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KR mass 91test S1 ch 16test S1 ch 17

DRI

PRESSURE RESPONSE

a) S1 Pressures at FS 81

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KR mass 51test S1 ch 06test S1 ch 10

b) S2 Pressures at FS 84.5

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time - sec

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lsn 6 mass 51test ch 4test ch 6

DRI

FLOOR PULSE

S1 Test 26 fps vertical

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TEST

DRI/KRASH

MSC/DYTRAN

DRIFLOOR VERTCAL PULSES – FLOOR VERTCAL PULSES –

GROUND, WATER, REGULATIONSGROUND, WATER, REGULATIONS

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FAR 27/29 Part 27/29.562Military - cockpitMililtary - cabinUH-1H Ground Test 23 fps vert - 18 fps latUH-1H Water Test 26 fps vertUH-1H Water Analysis (DRI) 26 fps vertUH-1H Water Analysis (MSC) 26 fps vertUH-1H Water Test 28 fps vert - 39 fps longUH-1H Water Analysis (DRI) 28 fps vert - 39 fps longUH-1H Water Analysis (MSC) 28 fps vert - 39 fps longSeahawk Ground Analysis (DRI) 30 fps vertSeahawk Water Analysis (DRI) 30 fps vertwater - upper limitwater - lower limitground - upper limitground - lower limit

Envelope ofWater Conditions

Envelope ofGround Conditions

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?

DRIDESIGN CONSIDERATIONS-DESIGN CONSIDERATIONS-

SEAT LOAD LIMITSEAT LOAD LIMIT

a) pilot floor, torso & dri responses without seat load limiter

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DRIlower torso & seat panavg of 4 floor pts

UP

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WN

b) pilot floor, torso & dri responses with 14.5 g seat load limiter

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DRIlower torso & seat panavg of 4 floor pts

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26 FPS VERTICAL WATER IMPACT

NO SEAT LOAD LIMITNO SEAT LOAD LIMIT 14.5G SEAT LOAD LIMIT14.5G SEAT LOAD LIMIT

DRITRENDS –

SEA STATE VS. CALM SEA

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calm 2.58 / 52 3.75 / 75 7.5 / 75

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FS217 - analFS217 - testFS412 - analFS412 - testFS552 - analFS552 - test

analysis average

test average

DRI S2/S1 Pressure Trend S2/S1 Pressure Trend Comparison; Analysis Vs. Test Comparison; Analysis Vs. Test

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33%

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Class 60 Filter Class 180 Filter Unfiltered

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analysistest

PRESSURES

Resultant VelocityResultant Velocity

S1 Test = 26 FPSS1 Test = 26 FPS

S2 Test = 48 FPSS2 Test = 48 FPS

S2/S1 Velocity RatioS2/S1 Velocity Ratio 1.851.85

S2/S1 KE RatioS2/S1 KE Ratio

3.413.41

DRI

TRENDS CorrelationSea State LevelsS2/S1 Test Levels- Pressure- Acceleration- Transfer Function

(Accel. to Pressure) - Filter Levels

Design EnvelopesPanel FailureFloor AccelerationMass Item ResponseOccupant-Seat Response

VS.- Panel Strength- Pitch Attitude- Seat Load Limit- Velocity Profile- Sea State

DRI

DITCHING COMPLIANCE

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Osprey p-mean (R&M 2917)

UH-1H p-mean (R&M 2917)

UH-1H avg p-dyn

Osprey avg p-dyn

FAA static flotation (UH-1H)FAR 25.533c distr press (Vx=50 fps)

FAR 25.533b local press (Vx=50 fps)

Osprey max p-dyn

UH-1H max p-dyn

UH-1H sea state = 4' high, 40' long, wave vel = 0Osprey sea state = 3.75' high, 75' long, wave vel = 0 -12 fps

UH-1H avg p-dyn (sea state)

Osprey avg p-dyn (sea state)

longitudinal velocity = 50 fpspitch = 10 deg ANU

Bell 609 test peakat 5 fps / 8.6 psi

Osprey test p-dyn

DRIDITCHING 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

DRIWhat 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

DRICURRENT DLE CONSIDERATIONS;

TAKE INTO ACCOUNTCONSIDERATIONS DITCHING WATER IMPACT

Configurations Modeled GTOW GTOWMax Design Landing Max Design Landing

Amphibious/Float Amphibious/FloatAuxiliary Fuel Tank Auxiliary Fuel Tank

S1, S2 Test ArticleDesign Envelope FAR27/FAR29 Civil 95th Percentile -Upr

Civil 95th Percentile-LwrVertical Velocity Ft/Sec. 0 to 25 10 to 28 Longitudinal Velocity Ft/Sec. 0 to 80 0 to 60Pitch Attitude Degree 0, 5, 10 0, 4, 5, 10Roll, Yaw Degree 10, 10 10, 10Sea State Calm Calm Sea State 4 NoLanding Gear Position Retracted, Extended Retracted, ExtendedRigid seat Yes NoLoad Limit Seat g 12, 14.5 12, 14.5Drag effects (Pitch-over) Yes NoFloat Design Considerations psi 3, 5, 10 10Panel Design Strength Tradeoff psi Current- 2X current NoSuction psi -10 No

Criteria Seat Stroke limit In. 5 5 Lumbar Load Limit Lb. 1500 1500 Underside Panel Failure psi Design Design Interior Bulkhead Failure psi Design Design Head Injury HIC 1000 1000 Restraint Belt Load Lb. 1750-2000 1750-2000 Mass Item Restraint g 30/30/15 <1> 30/30/15 <1> Engine Transmission Fuel

<1> Vertical/Longitudinal/ Side

DRICURRENT WATER IMPACT DLE CONCEPT

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Civil Rotorcraft, 95th % Land & Water - Upper Civil Rotorcraft, 95th % Land & Water - Lower

SPECIFIED:Configuration, % LiftPitch Attitude _ DegreeLanding Gear Extended/RetractedCriteria Seat Load Limit < _ g Seat Stroke < _ In. Interior Design Pressure, < _ psi Mass Item Limit; Vertical, Longitudinal, and Side < _ g

Engine > Criteria

Engine > Criteria

Mid Fuel > Criteria

Interior Bulkhead Pressure >Criteria

DRI

DLE-DITCHING APPLICATIONPreliminary Ditching Envelope - No Underside Panel Failure

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No Lift Sea State 2 67% Lift Sea State 2 No Lift Calm Sea67% Lift Calm Sea Ditching Criteria OEI Points

Weight = 23500 poundsCG = FS 349, Pitch = 10 degPanel Failure = 70 psiGears Retracted Sea State 2: WAVE

Height = 2 ftLength = 20 ftVelocity = 15 ft/secWave Front Impact

DRI

KRASH/SOMR-HIC RESULTS

KRASHSOM RESULTS - LONGITUDIAL PULSEHIC

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MIL STD

Military-WI

FAR27/29

Civil-WI

PULS

E

HIC value

EA Blkhd HICStiff.Blkhd HIC

1.01 inch Penetration8.50 inch head travel



50th Percentile male


x

1.06 inch surface penetration 8.5 inch head travel

Lap Belt Restraint Only

DRIAPPLICABILITY TO FAR 25;

TRANSPORT CATEGORY AIRCRAFT

FAR 25, FAR 27 and FAR 29 HAVEMANY SIMILARITIES:• Ditching Envelope• Seat Dynamic Test Requirements• Mass Item Retention• Acceptance Criteria• Compliance Procedures

DRI

SUMMARYSUMMARY• 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

DRI

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

the development of ditching and water impact design limits

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