MIT Subject 16.885J/ESD.35J Aircraft Systems Engineering F/A-18 FLIGHT CONTROL SYSTEM HENRY HARSCHBURGER Boeing (Retired) 1Flight Control Systems For Tactical Military Aircraft • Flight Control System Architecture – No Universal FCS Designs – Many Different Architectures Will Work – Any System Will Have Pros and Cons • Factors Influencing Architecture – Aircraft Mission – Aircraft Configuration – Procuring Agency • Service History With Similar Aircraft • Experience • Preferences HEH Sept. 2002 2Flight Control Systems For Tactical Military Aircraft • Other Factors Influencing Architecture – Flight Control System Team (Government/Contractors/Suppliers) • Experience of Team Leaders • Lessons Learned • Team Members Strongly Held Preferences • Organization – Total System Vs Subsystem/Component – System Integration Responsibility – Integration of Interfacing Systems/Subsystems – System Testing – Development Plan / Integrated Schedules HEH Sept. 2002 3Brief History of F/A-18A • 1974 Navy Fighter Study • DOD Direction HI/LO Mix (F-14/F-15 & Low Cost Fighter) • USAF and Navy Use Light Weight Fighter YF-16 or YF-17 • Contractor Teams – General Dynamics - LTV – Northrop - McDonnell Douglas • Flight Controls – YF-16 Fly-By-Wire – YF-17 Hydro-Mechanical and CAS • USAF Selected the YF-16 • Navy Selected Naval Version of YF-17 to Become F/A-18 • F/A-18 Required Changes to YF-17 Flight Control System HEH Sept. 2002 4Evolution of F/A-18A Flight Control System 5 F-15 YF-17 F- 4 SFCS (FBW) F- 4 PACT HEH Sept. 2002F/A-18 Requirements Development • Customer Requirements • Experience With F-4 and A-7 Aircraft • Lessons Learned From Development Programs • Navy Lessons Learned Database (all aircraft) • Contractor / Supplier Experience on Recent Programs Customer Requirements F/A-18 Weapon System Detailed Specification Contractor Design Requirements F/A-18 Aircraft and Systems HEH Sept. 2003 6F/A-18 Flight Control System Requirements F/A-18 Weapon System Detailed Specification Significant Specifications and Standards: • MIL-F-8785 Flying Qualities Piloted Airplanes • MIL-F-9490 Flight Control Systems - Design, Installation and Testing of Piloted Aircraft, General Specification for • MIL-H-5440 Hydraulic Systems, Aircraft Types I and II, Design, Installation, and Data Requirements for • MIL-STD-704 Electrical Power, Aircraft, Characteristics and Utilization of • DOD-STD-2167 Military Standard, Defense System Software Development Notes: 1. Specifications Can be Tailored in Weapons System Detailed Specification 2. Military Specifications are Being Replaced by Industry Standards. 7Carrier Based Aircraft - Unique Requirements 8Navy Experience and Concerns That Drove Requirements • Reliability History of Their Fleet – Electrical Wiring, Connectors and Generators – Electronic Systems (Autopilot, Autothrottle, etc.) • Maintainability History - Needs Major Improvement • Carrier Operations – Approach Speed – Catapult/Arresting Gear Loads – Spotting Factor (Wing Fold) –Environment • Corrosion Due to Humidity and Salt Water • Electromagnetic Interference – “Blue Water Operations” - No Alternate Field in Range • Survivability • First Production Digital FBW Flight Control System – Electromagnetic Interference – Generic Software Failures HEH Sept. 2002 910 HEH Sept. 2002Design Approach: • Use Airframe As Electromagnetic Shield (Carbon/epoxy) • Antenna EM Radiation Control • Subsystem EM Control: Bonding, Twisted/Shielded Wiring, Filter Pin Connectors • Ground Plane Interface Requirements HEH Sept. 2002 11Discussion of Requirements 12F/A-18A Hornet Primary Flight Control System Quad Digital FBW • Ailerons • Rudders • Leading Edge Flaps • Trailing Edge Flaps • Stabilators - With Mechanical Back-up 13WHY DID THEY DO THAT ?HEH Sept. 2002[ MANEUVERING [ ROLL & ] [ YAW & PITCH ] [ MANEUVERING & ROLL ] FLAPS FLAPS [ PITCH & ROLL ] FLAPS & ROLL ] 14 HEH Sept. 200215 HEH Sept. 2002F/A-18A Flight Control System Redundancy Levels • Redundancy Levels Driven By Reliability and Survivability • Control Functions Critical to Flying Qualities and/or Safety Must Have Two-Fail-Operate/Fail-Safe Capability – Primary Control Commands – Motion Sensors – Stabilator Actuators – Trailing Edge Flap Actuators (Needed for Carrier Landing) • Control Surfaces with Aerodynamic Redundancy and Less Critical Functions Must Have Fail-Operate/Fail-Safe Capability • Survivability Protection Dictated Separation of Control Functions – Flight Control Computers – Motion Sensors – Interconnecting Wiring HEH Sept. 2002 1617HEH Sept. 2002HEH Sept. 2002 1819HEH Sept. 2002Electronic Set Aileron Actuator T.E. Flap Actuator F/A-18A Flight Control Hardware Stabilator Rudder Actuator Actuator HEH Sept. 2002