Flight Management Systems

Introduction:

  • Flight Management Systems (FMS) accept inputs from a variety of sensors and provides guidance through all phases of flights in order to reduce workload
  • Employs a master computer interface
  • A common Control Display Unit (CDU) interfaces with the master computer
  • A pre-loaded database of global navigation information should be accessible to the pilot allowing for a quick flight plan setup (includes NAVAIDS, airways, and intersections, charts, etc.
  • GPS currently a dominate sensor in use today
  • Modern systems utilize Vertical Navigation (VNAV) as well as Lateral Navigation (LNAV)
  • In addition to guidance, FMS' provide information on all systems and conditions of flight such as fuel and weather

Aircraft Autopilot:

  • Mechanical means to control an aircraft using electrical, hydraulic, or digital systems
  • Autopilots come in three general types:
    • Single-axis, autopilots that only perform a function along a single axis such as a heading hold or wings level
    • Two-axis, adding elements of pitch control that may permit instrument approach functionality
    • Three-axis, includes yaw control
  • Autopilots may be driven by one or a combination of methods:
    • Position/attitude based: gyro senses wing position
      • Uses sensors to determine attitude, etc.
      • Precise, but expensive
    • Rate-based: turn-and-bank sensor
      • Uses 3 axes of movement and combines information
      • Systems are cheaper, but less sensitive
    • Accelerometers and AHRS
  • Modern systems may combine the above
  • Modern autopilots are digital

  • Autopilot Use During Climb:

    • Use of IAS holds allow for Vx and Vy climbs

  • Autopilot Use During Descent:

  • Autopilot Use in Controlled Airspace:

    • Use of functions like IAS hold allow for setting ATC restrictions

Flight Management System Failures:

  • Pilots might expect to experience a troublesome autopilot, but not necessarily one that won't disengage

Conclusion:

  • It is good practice to notify the flight deck when autopilot systems are engaged/disengaged
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