f/a-18a/b/c/d flight control computer software … flight control computer software upgrade military...
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F/A-18A/B/C/D Flight Control Computer Software Upgrade
Military Aircraft System Verification and Validation MIT 16.885J/ESD.35J
Fall 2004
CDR Paul Sohl Commanding Officer United States Naval Test Pilot School
V10.7
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Briefing Summary
• US Navy Acquisition Process Overview
• F/A-18 Aircraft Overview
• Flight Control Law Software Upgrade Program– Requirements
–
– Results
• Conclusions
Constraints and Challenges
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Defense Acquisition Management
Framework
Defense Acquisition Management
Framework
IOCBA
Tech Development
Operations
& Support
C
Technology Opportunities &
User Needs
Concept
Exploration
Technology
Development Demonstration
LRIP Full-Rate Prod &
Critical FRP
FOC
• • • Capability
Acquisition (Demonstration, Engineering
IOC: Initial Operational Capability FOC: Full Operational Capability
Validated & approved byInitial Capabilities
Document (ICD)
Capabilities Development
Document (CDD)
Capabilities Production
Document (CPD)
EEntrance criteria met before entering phases
EEvolutionary Acquisition or Single Step to Full
Concept & System Development
& Demonstration Production & Deployment
System
Integration
System
Deployment
Design
Review
Decision
Review
Sustainment Disposal
PProcess entry at Milestones A, B, or C
Sustainment Pre-Systems Systems Acquisition
Development, LRIP & Production)
operational validation authority
Relationship to Requirements Process
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System Development &
Demonstration Phase
System Development &
Demonstration Phase
B
System
Demonstration
System
Integration
Critical
Design
Review
System Integration System Demonstration Enter: PM has technical solution but Enter: Prototypes demonstrated in
has not integrated subsystems into intended environment complete system z Activities: Complete
z Activities: System Integration of development. DT/OT/LFT&E demonstrated subsystems and Exit: System demonstration in components. Reduction of integration intended environment using risk engineering development
Exit: Demonstration of prototypes in models; meets validated relevant environment requirements
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System Development &
Demonstration Phase
System Development &
Demonstration Phase
Purpose:
• To develop a system
• Reduce program risk
• Ensure operational supportability
• Ensure design for producibility
• Assure affordability
• Demonstrate system integration,
interoperability, and utility
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System Integration System Integration
• Purpose: Integrate subsystems – reduce
systems-level risk
• Key Activities:
íDemonstrate prototype articles
í Conduct an Early Operational Assessment (EOA)
í Prepare for Critical Design Review
(CDR)
íPrepare RFP for next effort/phase
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System Demonstration System Demonstration
• Purpose: Demonstrate the ability of the
system to operate in a useful way
consistent with the validated KPPs.
• Key Activities:í Conduct extensive testing: developmental,
operational, and survivability/lethality testing,
as appropriate
í Conduct technical reviews, as appropriate
í Demonstrate system in its intended
environment
í Prepare RFP for Low Rate Initial Production
í Prepare for Milestone C
í Update: Information requirements
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Summary: System Development &
Demonstration Phase
Summary: System Development &
Demonstration Phase
• May consist of System Integration andSystem Demonstration depending on:
– technology maturity
– affordability
• System demonstrated in the intended
environment; meets validated
requirements; industrial capability
available; meets exit criteria
• Manufacturing risk low
Bottom Line: System ready to begin LRIP?
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F/A-18A/B/C/D “Hornet”
• Supersonic, Multi-role, Combat Aircraft
– Introduced to fleet in 1983
• Relevant Design Features
– “Fly-by-wire” Flight Controls
– Twin Vertical Stabilizers
– Leading Edge Extension (LEX)
– Two Turbofan Engines
• SuperHornet (E/F Models)
– Introduced to fleet in 2001
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Flight Control System
• Two Digital Flight Control Computers (FCC)– Four separate channels
• Control Augmentation System
– Augments basic airframe stability
– Gains scheduled to enhance flying qualities
– Provides departure resistance
– Provides protection against overstress
– Actively controls structural mode interaction
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Program Origin
• Need to upgrade the FCC software– Mishap Prevention
• Suppress out of control flight modes
• Improve departure resistance
– Improve maneuverability at high AOA
• Improve roll performance above 30° AOA
• Implement “Pirouette” Feature
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The Main ProblemThe Main Problem
TwentyTwenty F/AF/A--18 aircraft lost due to18 aircraft lost due toOutOut--ofof--Control flightControl flight
TenTen aircraft were projected to be lostaircraft were projected to be lost
during the remaining lifecycle withoutduring the remaining lifecycle without
modificationsmodifications
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The Main ProblemThe Main Problem
Sustained Out of Control Flight Motion Following Nose-High, Banked, Zero Airspeed Flight
Eventual Recovery -
Significant Altitude Loss Loss of Aircraft
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F/A-18 Out of Control Flight Modes
• Departure – Aircraft no longer responding to pilot commands
• Post Departure Gyrations – Random oscillations (AOA, Airspeed, Sideforces)
• Fully Sustained OOCF Modes –
–
Spin Modes
Falling Leaf Modes
Departure From
Controlled Flight Post Departure
Gyrations
Spin Modes
Falling Leaf Modes
- Upright - Inverted
- Upright - Inverted
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Departure Resistance
The Usual Cause of a Departure:
overcomes control surface authority
E Roll or yaw due to sideslip (E)
Key to Controlled Flight:
Minimize E with control surfaces “Sideslip is the root of all evil”
E = Sideslip =
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Another Reason for Sideslip Control
Roll (Coupled) Departure
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Program Overview
• $15 Million dollars • Program Timeline
• Improved control laws developed (1988-90) • Baseline design used in SuperHornet (1993) • SuperHornet Developmental Test (1995-99) • “Heritage Hornet” upgrade proposed (2000) • New Control Law Developmental Test (2001-02) • Release to Fleet (June 2003)
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Major Design Goals
• Control sideslip buildup E– Add sideslip rate ( ) feedback
– Enhance sideslip (E) feedback
• Generate additional yaw rate – Use Adverse Yaw to our advantage
• Command opposite differential-stabilator
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Sideslip Control at High AOA
At low AOA… At high AOA…
Yawing motion produces sideslip Rolling motion produces sideslipRudder deflection controls sideslip Rolling surfaces control sideslip
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Design Process
• Implement E/F High AOA Architecture
• Adapt for A/B/C/D Architecture
• Tailor Gains to A/B/C/D Aerodynamics
• USN/Contractor Test Team Involvement• Integrated Test Team Philosophy
• Team Members able to review all documentation
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Program Constraints
• No hardware changes
– FCC software changes ONLY
• No software changes to Mission Computer
• No changes to Air Data System
– No modification to AOA Probes
– No provision for Sideslip Probe
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Program Challenges
• High Risk Flight Test
– Intentional Out of Control Flight Maneuvers
• Tailslides
• Spins
• Aggravated Inputs
– Risk Mitigation
• Extensive Simulations and Bench Tests
• Spin Chute Study
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Program Challenges
• No direct measurement of Sideslip
– Must develop software to estimate Sideslip
• AOA Probe Range = -14° to 35° AOA
– Need to estimate AOA above 35° degrees
• AOA estimate required to generate the new feedback signals (Sideslip and Sideslip Rate)
• Also needed to schedule gains at high AOA
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Developmental Flight Test
• 70 flights for 100 hrs – Used both two-seat and single-seat aircraft
• 8 external store loadings
• Approximately 600 test points – 400 Rolls
– 48 Spins
– 63 Tailslides
– 1v1 Operational Maneuvering
– Aggravated Control Inputs
– Failure Modes
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Recovery from Zero Airspeed Events
Recovery from Intentional Zero-Airspeed Tailslide
Old Control Laws
Motion Not ExcessiveExcessive Uncontrolled Motion
New Control Laws
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Flight Data
0.4M/35K (130 KCAS)
Roll Performance Enhancement Data Includes Various Aircraft Configurations
10
9
8
7
v10.7 FCC Software:6
Lateral Only
Lateral + Pedal5
4
3
2
1
0
5 10 15 20 25 30 35 40 45 50 55 60
0.4M/35K (130 KCAS)
New Capability
Existing Fleet Software:
Lateral or Lateral+Pedal
Flight DataTime to Bank 90° (sec)
Go
od
Average AOA (deg)
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B24 Flt 707 Rec 59v10.5.1 Control Laws
D1 Flight 1290 Rec 21v10.6.1 Control Laws
Improved Roll Performance at High AOA
0.4 Mach/35K
AOA = 35 deg.
Old Control Laws Lateral Stick Only 2 Seat Clean Lateral Stick + Pedal
New Control Laws 2 Seat +Cl Tank
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D1 Flight 1292 Rec 10v10.6.1 Control Laws
New Roll Capability at High AOA
0.4 Mach/35K
AOA=45 deg.Lat Stick + Pedal 2 Seat Clean
Lateral Stick + Pedal
2 Seat + CL Tank
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