J.B. LojkoJ.B. LojkoEngineer IIEngineer II

H.F. SmithH.F. SmithSr. Structural Specialist Engr.Sr. Structural Specialist Engr.

Lockheed Martin Aeronautics Lockheed Martin Aeronautics Company - MariettaCompany - Marietta

Modeling and SimulationModeling and Simulationof the C-5 Aftof the C-5 Aft

Cargo Loading SystemCargo Loading System

Title

AgendaAgenda

•System Description & BackgroundSystem Description & Background

•DADS ModelDADS Model

•EASY5 ModelEASY5 Model

•Solution DevelopmentSolution Development

•TestingTesting

•Solutions, Part 2Solutions, Part 2

-NASTRAN ModelNASTRAN Model

•Conclusions & Lessons LearnedConclusions & Lessons Learned

System DescriptionSystem Description& Background& Background

C-5 Aft Pressure DoorC-5 Aft Pressure Door

Mechanical System Mechanical System DescriptionDescription

• Plug-type Door - Seals Aft Cargo EnvelopePlug-type Door - Seals Aft Cargo Envelope

- HeightHeight - 11.4 ft- 11.4 ft

- WidthWidth - 19.0 ft- 19.0 ft

- Door Weight 1845 lbDoor Weight 1845 lb

• Carries Cabin Pressure Loads in Flight & Cargo or Vehicle Carries Cabin Pressure Loads in Flight & Cargo or Vehicle Loads for Drive-in LoadingLoads for Drive-in Loading

• Pressure Door Opens Up for Aerial Delivery & Truck-bed or Pressure Door Opens Up for Aerial Delivery & Truck-bed or Down for Drive-in LoadingDown for Drive-in Loading

• 2 Sets of Hinges and Actuators, Upper and Lower, Left and 2 Sets of Hinges and Actuators, Upper and Lower, Left and RightRight

Mechanical System Mechanical System DescriptionDescription

• Aerial Delivery SystemAerial Delivery System

- Aerial Delivery System (ADS) Requires Installation of a Aerial Delivery System (ADS) Requires Installation of a Pilot Parachute on the Lower Half of the DoorPilot Parachute on the Lower Half of the Door

- Pilot Parachute and Associated Hardware Weight 558 lbPilot Parachute and Associated Hardware Weight 558 lb

• Supporting Fuselage Structure Found to be Very FlexibleSupporting Fuselage Structure Found to be Very Flexible

Hydraulic System Hydraulic System DescriptionDescription

• 3000 psi System3000 psi System

• OpeningOpening

- 2 gpm Split to 1 gpm at 2 gpm Split to 1 gpm at ActuatorsActuators

- Ramp Blocker ValveRamp Blocker Valve

- Balanced Relief ValveBalanced Relief Valve

• ClosingClosing

- Initial Lift - FuseInitial Lift - Fuse

- Slow Down - FuseSlow Down - Fuse

First ContractFirst Contract

• Fatigue Problems with Upper Hinge Prompted USAF to Fatigue Problems with Upper Hinge Prompted USAF to Place LM Aero-Marietta Under Contract to Improve the Place LM Aero-Marietta Under Contract to Improve the Reliability of this SystemReliability of this System

• Initial Contract 1996 - Less Than Four Month ProjectInitial Contract 1996 - Less Than Four Month Project

- Geometry and Kinematics Created in CATIAGeometry and Kinematics Created in CATIA

- Ground Test Performed to Validate SimulationsGround Test Performed to Validate Simulations

- Analysis Performed in CATIA Using CAT/DADSAnalysis Performed in CATIA Using CAT/DADS

- Several Solutions ProposedSeveral Solutions Proposed

• Hydraulic Modifications - Slow Door OpeningHydraulic Modifications - Slow Door Opening

• Structural Modifications - Increase Strength in Selected Structural Modifications - Increase Strength in Selected AreasAreas

First ContractFirst Contract

First ContractFirst Contract

Actuator Load Comparison, Normal Actuator Load Comparison, Normal Operation, Test vs. DADSOperation, Test vs. DADS

First ContractFirst Contract

Actuator Load Comparison, Slow Actuator Load Comparison, Slow Operation, Test vs. DADSOperation, Test vs. DADS

Second ContractSecond Contract

• Follow On Contract 1999Follow On Contract 1999

- Incorporate Hydraulic Modifications to Reduce Door Incorporate Hydraulic Modifications to Reduce Door Opening SpeedOpening Speed

• First Attempt FailedFirst Attempt Failed

• Use DADS/Plant & EASY5 to Analyze All Proposed Use DADS/Plant & EASY5 to Analyze All Proposed Hydraulic Modifications Prior to TestingHydraulic Modifications Prior to Testing

• Using Analysis-Led Design the Second Attempt at Using Analysis-Led Design the Second Attempt at Modifying the Hydraulics was a SuccessModifying the Hydraulics was a Success

DADS ModelDADS Model

Model DefinitionModel Definition

• Model Simplified - Flexibility Greatly ReducedModel Simplified - Flexibility Greatly Reduced

• 16 Bodies 16 Bodies

• 6 Control Elements6 Control Elements

- Left & Right Actuator Distance, DistanceD, ForceLeft & Right Actuator Distance, DistanceD, Force

• ForcesForces

- 1 Contact Force - Door Stop1 Contact Force - Door Stop

- 2 TSDAs - Lower & Upper Fuselage Stops2 TSDAs - Lower & Upper Fuselage Stops

- 2 RSDAs - Flexibility in Torque Arm/Hook2 RSDAs - Flexibility in Torque Arm/Hook

Model DefinitionModel Definition

• Approximately 20 JointsApproximately 20 Joints

• OtherOther

- Curves - Door Stop DriverCurves - Door Stop Driver

EASY5 ModelEASY5 Model

Model DefinitionModel Definition

Model DefinitionModel Definition

• 62 Components62 Components

• Main Control ValveMain Control Valve

- Custom - HV LibraryCustom - HV Library

• Balanced Relief Valve (Simplification)Balanced Relief Valve (Simplification)

- Pilot-to-Open Check ValvePilot-to-Open Check Valve

• Fuses - Variable Orifice that Closes After Specified Fuses - Variable Orifice that Closes After Specified Volume of Flow is SensedVolume of Flow is Sensed

Model Definition, cont.Model Definition, cont.

• Actuators - AP Component for use with DADS Model Actuators - AP Component for use with DADS Model Extension ComponentExtension Component

• Ramp Blocker Valve - Critical that Pressure was Ramp Blocker Valve - Critical that Pressure was MeasuredMeasured

- Simple Fixed OrificeSimple Fixed Orifice

Solution DevelopmentSolution Development

SimulationsSimulations

• Conduct Simulations to Determine the Best Combination Conduct Simulations to Determine the Best Combination of Flow Regulatorsof Flow Regulators

- Performance Criteria - Load Reduction vs. Opening Performance Criteria - Load Reduction vs. Opening TimeTime

- Constraint - Slowing Opening Time Could Impact Constraint - Slowing Opening Time Could Impact Aircraft OperationAircraft Operation

• Current Flight Profile Could Change for ADS Current Flight Profile Could Change for ADS PreparationPreparation

EASY5 Results - EASY5 Results - Actuator Pressures & Actuator Pressures & PositionPosition

EASY5 Results - Ramp EASY5 Results - Ramp Position Valve, Pilot Position Valve, Pilot LineLine

DADS/Plant Results - DADS/Plant Results - Actuator LoadActuator Load

TestingTesting

Flow RegulatorsFlow Regulators

• Manifold, Cartridge Valve Flow RegulatorManifold, Cartridge Valve Flow Regulator

- Fluid RegulatorsFluid Regulators

- Modify Current 2.0 gpm Flow RegulatorsModify Current 2.0 gpm Flow Regulators

- .5 gpm & 1.0 gpm.5 gpm & 1.0 gpm

• MS-Type Flow RegulatorMS-Type Flow Regulator

- Parker HannifinParker Hannifin

- 1.5 gpm & 2.0 gpm1.5 gpm & 2.0 gpm

Cartridge Valve Flow Cartridge Valve Flow RegulatorRegulator

Two-Way Flow Regulator Response

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 500 1000 1500 2000 2500 3000

Valve Differential Pressure (psi)

Flo

w (

gp

m)

1 gpm Valve

.5 gpm Valve

TestsTests

• Baseline TestBaseline Test

- Verify Door Operates ProperlyVerify Door Operates Properly

• 1st Test1st Test

- 1.0/2.0 gpm Flow Regulators1.0/2.0 gpm Flow Regulators

- Regulators Delivered as SpecifiedRegulators Delivered as Specified

• 2nd Test2nd Test

- .5/1.5 gpm Flow Regulators.5/1.5 gpm Flow Regulators

- Modified 2.0 -> .5 gpm Could Not Perform as DesiredModified 2.0 -> .5 gpm Could Not Perform as Desired

C-5 Aft Pressure DoorC-5 Aft Pressure Door

C-5 Aft Pressure DoorC-5 Aft Pressure Door

C-5 Aft Pressure DoorC-5 Aft Pressure Door

Test ResultsTest Results

• BaselineBaseline

- Operated ProperlyOperated Properly

- Approximately 10 second OpeningApproximately 10 second Opening

• 1st Test1st Test

- Approximately 19 second OpeningApproximately 19 second Opening

- Predicted 21.29 second OpeningPredicted 21.29 second Opening

Test Results, cont.Test Results, cont.

• 2nd Test2nd Test

- Approximately 22 second OpendingApproximately 22 second Opending

- Predicted 40 seconds with Constant .5 gpm FlowPredicted 40 seconds with Constant .5 gpm Flow

- 2nd Test - Better Performance2nd Test - Better Performance

• Re-Run Simulations with Variable Flow Rate Re-Run Simulations with Variable Flow Rate RegulatorRegulator

SolutionsSolutionsPart 2Part 2

Loads & PressuresLoads & Pressures

• Goal of First ModelGoal of First Model

- Hydraulic Modification Will It Work?Hydraulic Modification Will It Work?

- How Long to Open & Close DoorHow Long to Open & Close Door

- Not Concerned with LoadsNot Concerned with Loads

• After Test, Model Fidelity Improved to Assist Loads & After Test, Model Fidelity Improved to Assist Loads & Structural Analysis OrganizationsStructural Analysis Organizations

- Variable Flow Regulator SimulatedVariable Flow Regulator Simulated

- Balanced Relief Valves AddedBalanced Relief Valves Added

Model DefinitionModel Definition

• Structural Flexibility in Fuselage ModeledStructural Flexibility in Fuselage Modeled

• DADS/Flex Used to Model Torque Arm/HookDADS/Flex Used to Model Torque Arm/Hook

• ForcesForces

- 10 Bushings10 Bushings

• MSC NASTRAN Model Used to Find Spring ConstantsMSC NASTRAN Model Used to Find Spring Constants

- 4 RSDAs - Damping Only - Friction, Any Uncertainties4 RSDAs - Damping Only - Friction, Any Uncertainties

Model DefinitionModel Definition

• Flexible BodiesFlexible Bodies

- Left & Right Torque Arm & HookLeft & Right Torque Arm & Hook

- MSC NASTRANMSC NASTRAN

- 1st Simulation Craig-Bampton Modes not Defined 1st Simulation Craig-Bampton Modes not Defined ProperlyProperly

- Continue Work Upon Return to MariettaContinue Work Upon Return to Marietta

DADS/FlexDADS/Flex

• Craig-Bampton Mode ErrorsCraig-Bampton Mode Errors

- Fixed ConstraintsFixed Constraints

- Free ConstraintsFree Constraints

• Axis OrientationAxis Orientation

- Local z-axis Parallel to Global y-axis for Revo & Cyli Local z-axis Parallel to Global y-axis for Revo & Cyli JointsJoints

- Several Axes Rotated about Global y-axis to Achieve Several Axes Rotated about Global y-axis to Achieve Correct Load PathCorrect Load Path

NASTRAN ModelNASTRAN Model

Torque Fitting Torque Fitting RepresentationRepresentation

• Torque Fitting and Arms IsolatedTorque Fitting and Arms Isolated

• Interface Points DefinedInterface Points Defined

- Shaft Inboard and Outboard BearingsShaft Inboard and Outboard Bearings

- Actuator AttachActuator Attach

- Door/Arm ContactDoor/Arm Contact

- Inboard RollerInboard Roller

- Restraint HookRestraint Hook

• Structure Idealized in NASTRANStructure Idealized in NASTRAN

• Mirrored for Right SideMirrored for Right Side

Fitting Back-Up Fitting Back-Up RepresentationRepresentation

• Fuselage Plug from FS 1964 to 2178 Used. Detailed Fuselage Plug from FS 1964 to 2178 Used. Detailed Idealization of Back-up Frame Included.Idealization of Back-up Frame Included.

• Five Interface Points ChosenFive Interface Points Chosen

- Actuator PointActuator Point

- Inboard Upper Support PointInboard Upper Support Point

- Outboard Upper Support PointOutboard Upper Support Point

- Inboard Lower Support PointInboard Lower Support Point

- Outboard Lower Support PointOutboard Lower Support Point

• Mirrored for Right SideMirrored for Right Side

NASTRAN Analysis RunNASTRAN Analysis Run

• Normal ModesNormal Modes

• Imposed Deflection Force Matrix GenerationImposed Deflection Force Matrix Generation

- Unit deflections imposed on interface point DOF’s one Unit deflections imposed on interface point DOF’s one at a time with remaining interface point DOF’s at a time with remaining interface point DOF’s constrained.constrained.

• Analyses performed for each side separately for each Analyses performed for each side separately for each substructure.substructure.

Fitting IdealizationFitting Idealization

Back-Up IdealizationBack-Up Idealization

Conclusion &Conclusion &Lessons LearnedLessons Learned

MethodologyMethodology

MECHANICALSYSTEM

PROTOTYPE

MONODETAILMODELS

KINEMATICS(CAT/DADS)

MECHANICALSYSTEMBUILDUP

DYNAMICS

HYDRAULICS& CONTROLS

Integrated CAEIntegrated CAE

• CATIACATIA

- Work From One Geometry Model (CATIA)Work From One Geometry Model (CATIA)

• DADSDADS (CAT/DADS)(CAT/DADS)

- Define Load PathsDefine Load Paths

• NASTRANNASTRAN

• EASY5EASY5

• Clearly Define Requirements for InterfacesClearly Define Requirements for Interfaces

• INTEGRATED CAE WILL SAVE TIME & MONEYINTEGRATED CAE WILL SAVE TIME & MONEY