Comprehensive Study Guide_ Automatic Flight Control Systems (AFCS) PDF

Comprehensive Study Guide: Automatic Flight Control Systems (AFCS) Objectives Flight Director (FD): Understand its purpose, components, inputs, and modes of operation. Autopilot: Explore its functionality, control mechanisms, and various operational modes. Auto Thro...

Comprehensive Study Guide: Automatic Flight Control Systems (AFCS) Objectives Flight Director (FD): Understand its purpose, components, inputs, and modes of operation. Autopilot: Explore its functionality, control mechanisms, and various operational modes. Auto Throttle: Learn its purpose, operational phases, and integration into flight management. Yaw Damper: Examine its role in maintaining directional stability and damping Dutch Roll oscillations. Flight Director (FD) Purpose: Assists pilots by providing pitch and roll steering commands to maintain a desired flight path, displayed on the ADI. These commands ensure smooth changes in altitude and heading. Inputs and Computations: ○ Inputs include ADC, compass systems, vertical gyros, and VHF navigation radios. ○ Computed by two main systems: Roll Computer (lateral steering) and Pitch Computer (vertical steering). Modes: ○ Heading, VOR/LOC, Approach (auto/manual), Altitude Hold, Go-Around, and Back Course. ○ Specific functions, such as VOR/LOC, use inputs like course deviation and roll attitude to adjust commands. Displays: ○ V-Bar Display: Combines pitch and roll commands into an integrated cue. ○ Split-Cue Display: Displays independent left/right and up/down commands using crosshairs. Key Features: ○ Commands are limited (±12° pitch, varying roll limits by mode: ±30° Heading, ±25° VOR/LOC, ±15° Approach). ○ Gain programming adjusts command sensitivity, especially during narrow glideslope beam approaches. Autopilot (AP) Function: Electronically controls pitch, roll, and yaw, reducing pilot workload. Capable of precision tasks such as automatic landing in modern systems. Operational Modes: ○ Control Wheel Steering (CWS): Pilot manually inputs commands, processed to assist flight control. ○ Command Mode: Fully automated based on AFCS Mode Control Panel inputs like heading and altitude. Components and Systems: ○ Roll Channel: Manages ailerons and spoilers, with outputs converted to mechanical movements via PCU. ○ Pitch Channel: Controls elevators and stabilizers; retrims stabilizers automatically for sustained pitch changes. ○ Yaw Channel: Uses the rudder for yaw damping and turn coordination. Servo Systems: ○ Electro-pneumatic: Simpler systems for direct control. ○ Electro-mechanical and hydraulic: Used in advanced aircraft for precision and redundancy. Advanced Functions: ○ Glideslope deviation attenuation ensures smooth transitions during ILS approaches. ○ Integration with sensors like Low Range Radio Altimeter for altitude precision. Auto Throttle (AT) Purpose: Automates throttle management to maintain thrust and speed parameters, reducing workload. Operational Phases: ○ Takeoff: Automatically sets N1 thrust based on environmental factors. ○ Climb and Cruise: Adjusts to meet speed or Mach requirements, optimizing fuel efficiency. ○ Descent: Maintains idle thrust while observing speed limits. ○ Go-Around: Rapidly increases thrust to achieve required climb rates. ○ Flare: Retards throttles for landing. Key Components: ○ Servo actuators, torque sensing mechanisms, and override systems for manual control. ○ Power Lever Angle (PLA) synchros ensure feedback on throttle positions. Yaw Damper Purpose: Stabilizes directional oscillations (Dutch Roll), especially in swept-wing aircraft prone to dihedral effects. Operation: ○ Utilizes rate gyros to detect oscillations and dampens them via rudder deflections. ○ Controlled by a yaw damper computer, working through hydraulic PCUs. ○ Operates independently of pilot inputs, with no feedback to rudder pedals. Key Features: ○ Limited rudder movement (2–5°) based on airspeed and aerodynamic requirements. ○ Gain programming modifies response sensitivity depending on flight conditions. Types: Series yaw damping integrates with pilot rudder inputs for coordinated turns. Flight Director and Autopilot Integration Modes and Functions: ○ Heading Mode: Guides aircraft to a preselected heading using roll adjustments. ○ VOR/LOC Mode: Tracks VOR radials or localizer courses, transitioning to ILS approaches when necessary. ○ Approach Mode: Combines localizer and glideslope capture, ensuring precision landing. ○ Altitude Modes: Altitude Hold maintains barometric levels; Preselect sets desired levels; Vertical Speed adjusts climb/descent rates. Beam Capture: Smoothly transitions to track VOR or localizer beams, arming for glideslope capture during approaches. Safety Enhancements: Disengagement protocols include visual and auditory alerts, ensuring pilot awareness. Key Components and Sensors Inputs: ○ Vertical: VG, AHRS, IRU, ADC provide altitude and attitude data. ○ Lateral: Gyros, compass systems, and VHF navigation ensure directional accuracy. Actuation: ○ Servo motors or hydraulic PCUs translate computed commands into physical control surface adjustments.  ○ Feedback loops stabilize aircraft by nullifying error signals. Integrated Protections: Flight envelope safeguards prevent overstressing the aircraft during operations. Summary of FD Commands Displays: Combines pitch and roll guidance for intuitive adjustments during all flight phases. Modes: Supports diverse scenarios, including Back Course approaches and Go-Around maneuvers. Error Correction: Steering commands dynamically address deviations from the flight path. Autopilot Operational Enhancements Detailed Logic: Advanced interlock systems ensure reliable engagement and safe operation. Specialized Modes: ○ Turbulence Mode: Improves response during unstable weather conditions. ○ Altitude Select: Precisely transitions to target altitudes, supported by CADC inputs. Safety Features: ○ Disengagement alerts, such as flashing panel lights and control column warnings, maintain pilot situational awareness. ○ Override mechanisms allow manual control in emergencies. This enhanced study guide now incorporates deeper technical details and additional operational examples, ensuring a robust resource for exam preparation.