J.B. Lojko

1
Title
Modeling and Simulation of the C-5 Aft Cargo
Loading System

• J.B. Lojko
• Engineer II
• H.F. Smith
• Sr. Structural Specialist Engr.
• Lockheed Martin Aeronautics Company - Marietta

2
Agenda

• System Description Background
• DADS Model
• EASY5 Model
• Solution Development
• Testing
• Solutions, Part 2
• NASTRAN Model
• Conclusions Lessons Learned

3
System Description Background
4
C-5 Aft Pressure Door
5
Mechanical System Description

• Plug-type Door - Seals Aft Cargo Envelope
• Height - 11.4 ft
• Width - 19.0 ft
• Door Weight 1845 lb
• Carries Cabin Pressure Loads in Flight Cargo or
  Vehicle Loads for Drive-in Loading
• Pressure Door Opens Up for Aerial Delivery
  Truck-bed or Down for Drive-in Loading
• 2 Sets of Hinges and Actuators, Upper and Lower,
  Left and Right

6
Mechanical System Description

• Aerial Delivery System
• Aerial Delivery System (ADS) Requires
  Installation of a Pilot Parachute on the Lower
  Half of the Door
• Pilot Parachute and Associated Hardware Weight
  558 lb
• Supporting Fuselage Structure Found to be Very
  Flexible

7
Hydraulic System Description

• 3000 psi System
• Opening
• 2 gpm Split to 1 gpm at Actuators
• Ramp Blocker Valve
• Balanced Relief Valve
• Closing
• Initial Lift - Fuse
• Slow Down - Fuse

8
First Contract

• Fatigue Problems with Upper Hinge Prompted USAF
  to Place LM Aero-Marietta Under Contract to
  Improve the Reliability of this System
• Initial Contract 1996 - Less Than Four Month
  Project
• Geometry and Kinematics Created in CATIA
• Ground Test Performed to Validate Simulations
• Analysis Performed in CATIA Using CAT/DADS
• Several Solutions Proposed
• Hydraulic Modifications - Slow Door Opening
• Structural Modifications - Increase Strength in
  Selected Areas

9
First Contract
10
First Contract
Actuator Load Comparison, Normal Operation, Test
vs. DADS
11
First Contract
Actuator Load Comparison, Slow Operation, Test
vs. DADS
12
Second Contract

• Follow On Contract 1999
• Incorporate Hydraulic Modifications to Reduce
  Door Opening Speed
• First Attempt Failed
• Use DADS/Plant EASY5 to Analyze All Proposed
  Hydraulic Modifications Prior to Testing
• Using Analysis-Led Design the Second Attempt at
  Modifying the Hydraulics was a Success

13
DADS Model
14
Model Definition

• Model Simplified - Flexibility Greatly Reduced
• 16 Bodies
• 6 Control Elements
• Left Right Actuator Distance, DistanceD, Force
• Forces
• 1 Contact Force - Door Stop
• 2 TSDAs - Lower Upper Fuselage Stops
• 2 RSDAs - Flexibility in Torque Arm/Hook

15
Model Definition

• Approximately 20 Joints
• Other
• Curves - Door Stop Driver

16
EASY5 Model
17
Model Definition
18
Model Definition

• 62 Components
• Main Control Valve
• Custom - HV Library
• Balanced Relief Valve (Simplification)
• Pilot-to-Open Check Valve
• Fuses - Variable Orifice that Closes After
  Specified Volume of Flow is Sensed

19
Model Definition, cont.

• Actuators - AP Component for use with DADS Model
  Extension Component
• Ramp Blocker Valve - Critical that Pressure was
  Measured
• Simple Fixed Orifice

20
Solution Development
21
Simulations

• Conduct Simulations to Determine the Best
  Combination of Flow Regulators
• Performance Criteria - Load Reduction vs. Opening
  Time
• Constraint - Slowing Opening Time Could Impact
  Aircraft Operation
• Current Flight Profile Could Change for ADS
  Preparation

22
EASY5 Results - Actuator Pressures Position
23
EASY5 Results - Ramp Position Valve, Pilot Line
24
DADS/Plant Results - Actuator Load
25
Testing
26
Flow Regulators

• Manifold, Cartridge Valve Flow Regulator
• Fluid Regulators
• Modify Current 2.0 gpm Flow Regulators
• .5 gpm 1.0 gpm
• MS-Type Flow Regulator
• Parker Hannifin
• 1.5 gpm 2.0 gpm

27
Cartridge Valve Flow Regulator
28
Tests

• Baseline Test
• Verify Door Operates Properly
• 1st Test
• 1.0/2.0 gpm Flow Regulators
• Regulators Delivered as Specified
• 2nd Test
• .5/1.5 gpm Flow Regulators
• Modified 2.0 -gt .5 gpm Could Not Perform as
  Desired

29
C-5 Aft Pressure Door
30
C-5 Aft Pressure Door
31
C-5 Aft Pressure Door
32
Test Results

• Baseline
• Operated Properly
• Approximately 10 second Opening
• 1st Test
• Approximately 19 second Opening
• Predicted 21.29 second Opening

33
Test Results, cont.

• 2nd Test
• Approximately 22 second Opending
• Predicted 40 seconds with Constant .5 gpm Flow
• 2nd Test - Better Performance
• Re-Run Simulations with Variable Flow Rate
  Regulator

34
SolutionsPart 2
35
Loads Pressures

• Goal of First Model
• Hydraulic Modification Will It Work?
• How Long to Open Close Door
• Not Concerned with Loads
• After Test, Model Fidelity Improved to Assist
  Loads Structural Analysis Organizations
• Variable Flow Regulator Simulated
• Balanced Relief Valves Added

36
Model Definition

• Structural Flexibility in Fuselage Modeled
• DADS/Flex Used to Model Torque Arm/Hook
• Forces
• 10 Bushings
• MSC NASTRAN Model Used to Find Spring Constants
• 4 RSDAs - Damping Only - Friction, Any
  Uncertainties

37
Model Definition

• Flexible Bodies
• Left Right Torque Arm Hook
• MSC NASTRAN
• 1st Simulation Craig-Bampton Modes not Defined
  Properly
• Continue Work Upon Return to Marietta

38
DADS/Flex

• Craig-Bampton Mode Errors
• Fixed Constraints
• Free Constraints
• Axis Orientation
• Local z-axis Parallel to Global y-axis for Revo
  Cyli Joints
• Several Axes Rotated about Global y-axis to
  Achieve Correct Load Path

39
NASTRAN Model
40
Torque Fitting Representation

• Torque Fitting and Arms Isolated
• Interface Points Defined
• Shaft Inboard and Outboard Bearings
• Actuator Attach
• Door/Arm Contact
• Inboard Roller
• Restraint Hook
• Structure Idealized in NASTRAN
• Mirrored for Right Side

41
Fitting Back-Up Representation

• Fuselage Plug from FS 1964 to 2178 Used.
  Detailed Idealization of Back-up Frame Included.
• Five Interface Points Chosen
• Actuator Point
• Inboard Upper Support Point
• Outboard Upper Support Point
• Inboard Lower Support Point
• Outboard Lower Support Point
• Mirrored for Right Side

42
NASTRAN Analysis Run

• Normal Modes
• Imposed Deflection Force Matrix Generation
• Unit deflections imposed on interface point DOFs
  one at a time with remaining interface point
  DOFs constrained.
• Analyses performed for each side separately for
  each substructure.

43
Fitting Idealization
44
Back-Up Idealization
45
Conclusion Lessons Learned
46
Methodology
MECHANICAL SYSTEM PROTOTYPE
47
Integrated CAE

• CATIA
• Work From One Geometry Model (CATIA)
• DADS (CAT/DADS)
• Define Load Paths
• NASTRAN
• EASY5
• Clearly Define Requirements for Interfaces
• INTEGRATED CAE WILL SAVE TIME MONEY