V 1 0 . 7 F/A-18A/B/C/D Flight Control Computer Software Upgrade Military Aircraft System Verification and Validation MIT 16.885J/ESD.35J Fall 2003 CDR Paul Sohl Commanding Officer United States Naval Test Pilot School Briefing Summary ? US Navy Acquisition Process Overview ? F/A-18 Aircraft Overview ? Flight Control Law Software Upgrade Program – Requirements – –Results ? Conclusions Constraints and Challenges Defense Acquisition Management Framework Defense Acquisition Management Framework IOC BA 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 by Initial Capabilities Document (ICD) Capabilities Development Document (CDD) Capabilities Production Document (CPD) Concept & System Development & Demonstration Production & Deployment System Integration System Deployment Design Review Decision Review Sustainment Disposal PProcess entry at Milestones A, B, or C EEntrance criteria met before entering phases EEvolutionary Acquisition or Single Step to Full Sustainment Pre-Systems Systems Acquisition Development, LRIP & Production) operational validation authority Relationship to Requirements Process 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 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 System Integration System Integration ? Purpose: Integrate subsystems – reduce systems-level risk ? Key Activities: í Demonstrate prototype articles í Conduct an Early Operational Assessment (EOA) í Prepare for Critical Design Review (CDR) í Prepare RFP for next effort/phase 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 Summary: System Development & Demonstration Phase Summary: System Development & Demonstration Phase ? May consist of System Integration and System 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? 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 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 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 The Main Problem Twenty F/A-18 aircraft lost due to Out-of-Control flight Ten aircraft were projected to be lost aircraft were projected to be lost during the remaining lifecycle without during the remaining lifecycle without modifications The Main Problem Sustained Out of Control Flight Motion Following Nose-High, Banked, Zero Airspeed Flight Eventual Recovery - Significant Altitude Loss Loss of Aircraft 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 Falling Leaf Modes Spin Modes -Upright -Inverted -Upright -Inverted 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 = Another Reason for Sideslip Control Roll (Coupled) Departure 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) Major Design Goals E ? Control sideslip buildup – Add sideslip rate ( ) feedback – Enhance sideslip (E) feedback ? Generate additional yaw rate – Use Adverse Yaw to our advantage ? Command opposite differential-stabilator Sideslip Control at High AOA At low AOA… At high AOA… Yawing motion produces sideslip Rolling motion produces sideslip Rudder deflection controls sideslip Rolling surfaces control sideslip 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 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 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 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 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 Recovery from Zero Airspeed Events Recovery from Intentional Zero-Airspeed Tailslide Old Control Laws Motion Not ExcessiveExcessive Uncontrolled Motion New Control Laws Flight Data 0.4M/35K (130 KCAS) Roll Performance Enhancement Data Includes Various Aircraft Configurations Time to Bank 90° (sec) 10 9 8 7 v10.7 FCC Software: 6 Lateral Only Lateral + Pedal 5 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 Go o d Flight Data Average AOA (deg) B24 Flt 707 Rec 59 v10.5.1 Control Laws D1 Flight 1290 Rec 21 v10.6.1 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 D1 Flight 1292 Rec 10 v10.6.1 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 + C L Tank