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Birdstrike Certification Tests of F-35 Canopy and Airframe Structure
Steve D. OwensF-35 Structures Certification LeadF 35 St t D l t
Eric O. CaldwellMechanical Engineer Staff
Mike R. WoodwardChief Engineer - StructuresF 35 Chi f E i OffiF-35 Structures Development
Lockheed Martin Aeronautics Company
2009 Aircraft Structural Integrity Program (ASIP) ConferenceDecember 1-3, 2009
Aircraft Systems Test LaboratoryLockheed Martin Aeronautics Company
F-35 Chief Engineers OfficeLockheed Martin Aeronautics Company
1© 2009 Lockheed Martin Corporation
Jacksonville, FL
DISTRIBUTION STATEMENT A: Approved for Public Release; Distribution Is Unlimited
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Presentation Outline
• Birdstrike Assessment Approach• Canopy Design & Requirements• Canopy Bird Impact & Removal System Test Results• F 35B STOVL Lift Fan Inlet Door Bird Impact Test Results• F-35B STOVL Lift Fan Inlet Door Bird Impact Test Results• Inlet Duct Structure - Strength Analysis & Test Plan
2Public Information Release Authorization AER200911008/JSF09-376 Approved© 2009 Lockheed Martin Corporation
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Aircraft Vulnerability to Bird Impact was Assessed in Preliminary DesignAssessed in Preliminary Design
Navy, AF Bird Weight
0.8
0.9
1
ty
Navy
Air Force
Cumulative Velocity Probability (0-5000 ft)
1
NormVel. (kts)
Norm Bird
Weight (lb)
CritVel. (kts)
Bird Weight
(lb)
Vuln. Area (sq ft)
Aircraft Component NormVel. (kts)
Norm Bird
Weight (lb)
CritVel. (kts)
Bird Weight
(lb)
Vuln. Area (sq ft)
Aircraft Component
1 X 10 -7 Event / Flt Hr
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Cum
ulat
ive
Prob
abili
t
0.4
0.5
0.6
0.7
0.8
0.9
mul
ativ
e Pr
obab
ility
CTOLCVSTOVL
324445921.3CANOPY-STOVL-AFT
27644511.51.1CANOPY-CTOL/CV-AFT
24043931.53.3INLET DUCT
225444912.4VERTICAL TAIL LE
158431610.6HORIZONTAL TAIL LE
324445921.3CANOPY-STOVL-AFT
27644511.51.1CANOPY-CTOL/CV-AFT
24043931.53.3INLET DUCT
225444912.4VERTICAL TAIL LE
158431610.6HORIZONTAL TAIL LE
0
0 2 4 6 8 10Bird Weight
0
0.1
0.2
0.3
0 200 400 600 800 1000 1200V (ft/s)
Cum
6374520622.0WING LEADING EDGES
53645054.510.0INTAKE FAIRINGS
51344844.58.0LIFT FAN INLET DOOR
44144713.52.0RADOME
35444482.55.0CANOPY-WINDSCREEN
6374520622.0WING LEADING EDGES
53645054.510.0INTAKE FAIRINGS
51344844.58.0LIFT FAN INLET DOOR
44144713.52.0RADOME
35444482.55.0CANOPY-WINDSCREEN
Notional Data
ReportingFlight Hour Data # Events resulting in LOA LOA Rate/Flt Hr (*10-7)
AC TypeReporting
Period Fleet Hours Total Canopy Engine Structure Total Canopy Engine StructureAV-8B 1980-2005 850927 5 2 2 1 58.76 23.50 23.50 11.75F-18 1980-2005 4952833 3 1 1 1 6.06 2.02 2.02 2.02F-16 1985-2005 7492673 7 2 5 0 9.34 2.67 6.67 0.00F-15 1985-2005 4193652 1 0 1 0 2.38 0.00 2.38 0.00
AV 8B h ti t d b d 187204 fl t h f 10/98 th h 3/2004
Probability = f(Bird Weight, AV Flight Envelope, Bird Population Density, Threat Area, Time)
AV-8B hours estimated based on 187204 fleet hours from 10/98 through 3/2004• Bird Strike Defined as a Probabilistic Based Design Criteria
• Historical Military Bird Strike Incidence Databases Used to Support System Safety Assessments Considering Structural ‘Similarity’
3Public Information Release Authorization AER200911008/JSF09-376 Approved© 2009 Lockheed Martin Corporation
y y g y
• Assessment Led to Focus on Canopy, STOVL Lift Fan Inlet Door, and Engine Inlet Duct Structure for Mitigation & Verification Testing
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F-35 Canopy Design Description• Transparency is Single Piece Formed & Stretched Acrylic• Thick Windscreen is Fwd of the Bowframe & Transitions to
Thi T S ti AftThinner Transparency Section Aft• CTOL & CV Canopy Designs are Common & Windscreen
Design is Tri-variant Common• Flexible Linear Shape Charge Bonded to IML to Facilitate
Pilot Escape
TransparencyExplosive Shaped
Windscreen
TransparencyExplosive Shaped Charge Cord
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CTOL / CV Canopy STOVL Canopy
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Canopy Bird Impact Design Criteria• Canopy Design & Test Success Criteria:
– Canopy System Must Withstand Impact of a 4 lb Bird at 480 Kt on the Reinforced Windscreen & 350 Kt on the Canopy Crownon the Reinforced Windscreen & 350 Kt on the Canopy Crown Without:• Breaking or Deflecting so as to Strike the Pilot When
S t d i th D i E “Hi h” P itiSeated in the Design Eye “High” Position,• Damage To The Canopy That Would Cause Incapacitating
Injury To The Pilot, or• Damage That Would Preclude Safe Operation of, or
Emergency Egress From the AircraftPilot Design E / H d
Windscreen
Eye / Head Position
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Canopy
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Canopy Bird Impact Test Approach
• Windscreen Tests - ‘High’ & ‘Low’ Shots at 480 Kt with 4 lb Bird• Canopy Crown Tests• Canopy Crown Tests
– Shoot STOVL & CTOL/CV Variant Canopies Using 4 lb / 350 Kt Bird – Subsequent Firing of Transparency Removal System to Validate
Proper Functionality & Fly-away of the TransparencyProper Functionality & Fly-away of the Transparency
Crown Shot
Windscreen ‘Hi h’ Sh t
Crown Shot Location
‘High’ Shot Location
Windscreen
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‘Low’ Shot Location
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Bird Impact Test Facility & Setup
Speed ‘Trap’ to Measure Projectile VelocityView Looking into the Business End of the Cannon
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Bore Sighting Provisions
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Accurate Representation of Boundary Conditions Maintained for Canopy Testspy
• Representative Forward Fuselage
Include Canopy Frame & Latches
I l d P i d C S l
Simulated seat rail breaker bar points at forward most Simulated
Foam manikin
Head Tracker Unit
Include Pressurized Canopy Seal
• Positioned at Aircraft Cruise Angle of Attack
• Set-up Simulated Features in Close Proximity to the Canopy Crown
locationfoam instrument panel cover
Helmet profile at max height and
8Public Information Release Authorization AER200911008/JSF09-376 Approved© 2009 Lockheed Martin Corporation
to the Canopy Crown
• Projectile is a Euthanized Chicken
gstretched over fore/aft range
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F-35 STOVL Windscreen Bird Impact Test
480 Kt – 4 lb Chicken
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Canopy Bird Impact Design Requirements were Successfully Verified by TestCanopy Bird Impact Design Requirements were Successfully Verified by Test
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F-35 CTOL Canopy Crown Bird Impact- Design Development Test -g p
• CTOL 350 Knot Canopy Crown Bird Impact – 4.0 lb Chicken• 0.0004 Seconds Per Image Displayed; 3 msec Duration• Preliminary Design Transparency with Reduced Thickness Failed• Test Success was Achieved for Re-sized Transparency
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Firing the Transparency Removal System
Post Bird Impact Test Firing of the TRS Detonation CordPost Bird Impact Test Firing of the TRS Detonation Cord
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Post Bird Impact Test Firing of the TRS Detonation Cord Successfully Demonstrated Escape System Capability
Post Bird Impact Test Firing of the TRS Detonation Cord Successfully Demonstrated Escape System Capability
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Design Criteria for Bird Impact on Airframe Structure
a) Identify Structure Likely To Be Damaged from a Birda) Identify Structure Likely To Be Damaged from a Bird Mass/Speed Derived from a 1 X 10-5 Occurrence / Flt Hr to Identify Structure Likely Damaged for Logistics Planning
b) Prevent Loss of Aircraft or Pilot Incapacitation Due to Impact
Cost of Ownership Related Criteria
from a Bird with Mass/Speed Derived from a 1 X 10-7
Occurrence / Flt Hr
Flight Safety Driven Criteria
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STOVL Lift Fan Inlet Door Selected for Bird Impact TestingBird Impact Testing
Lift Fan Inlet Door
Aux Air Doors
Inlet Door
• Lift Fan Inlet Door Opens During STOVL Mode Operations• Aircraft Forward Speeds are Relatively Low During STOVL
Mode Flight• Selected for Testing Due to Concern that Bird or DoorSelected for Testing Due to Concern that Bird or Door
Structural Debris Could be Ingested into the Lift Fan or Become FOD for the Main Engine via the Open Auxiliary Air Intake
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Intake
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STOVL Mode Flight Operating Doors
LF Inlet Door
Aux Air Intake & Doors
Lift FanLift Fan
LFI Door is Comprised of Monolithic Carbon Composite
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Skins Mechanically Attached to Metallic Substructure
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Lift Fan Inlet Door Test Setup
Impact Site
• Door Angle Set at “Full Open” Position Plus Increment to Account for Aircraft Angle of Attack
• Impact Location Centered on the Largest Bay Over the Fan• Test for Score Used a 2 lb Bird Shot @ 140 Kt• Test for Added Knowledge Used a 2 lb Gelatin Simulated ‘Bird’
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LFI Door Impact Test ResultsChicken & GelatinChicken & Gelatin
140 Kt / 2.0 lb Chicken140 Kt / 2.0 lb Chicken
168 Kt / 2.0 lb Gelatin Projectile
• Door Withstood the Bird Impact without Exhibiting A-scan Detectable Damage at the Impact Location
16Public Information Release Authorization AER200911008/JSF09-376 Approved© 2009 Lockheed Martin Corporation
Detectable Damage at the Impact Location
• Second Shot Using Gel Bird Yielded the Same Result
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Engine Inlet Duct Structure Assessed During Design
• Inlet Duct Structure
During Design
– Composite Inlet Duct Skins are Mechanically Fastened to Metallic SubstructureV l bilit A l i– Vulnerability Analysis Considered Bounding Subsystem Installations
Possible Impact ZonePossible Impact Zone
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View Looking Aft @ LHS Inlet Duct
View Looking Down
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Dynamic FEA of Inlet Duct Structure Conducted During Design DevelopmentConducted During Design Development
• Dynamic Nonlinear FEA Used to Predict Strength Capabilities of Vulnerable Inlet Duct StructureDuct Structure
– 4 lb Cylindrically Shaped ‘Bird’– Properties Governed by Equations of State
Defined within ABAQUSDefined within ABAQUS– Detail Strength Analysis Performed– Structure Hardened to Preclude Bird Impact
Damage That Could Result in a Cat I Event
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Dynamic Nonlinear FEA Used During Design to Size StructureDynamic Nonlinear FEA Used During Design to Size Structure
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Conclusions
• F-35 Airframe Structure & Canopy Meets Stringent Bird Impact Design Criteria as Validated by Structural Analysis & Representative Testing
• Minor Changes in Transparency Nominal Design ThicknessMinor Changes in Transparency Nominal Design Thickness Resulted in Significant Changes in Resistance to Bird Impact Induced Deflection & Damage
• Early Bird Impact Vulnerability Assessments & Application of Dynamic FEA During Preliminary Structural Design Led to Improvements that Enhance Air Vehicle Safety
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