Flight Management Systems (FMS)

Flight Management Systems accept inputs from a variety of sensors and provides guidance through all phases of flights to reduce workload.

Introduction

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

Flight Director/Autopilot

Flight Director/Autopilot
  • Flight directors/autopilot systems provide mechanical means to control an aircraft using electrical, hydraulic, or digital systems.
  • The entire flight director/autopilot system is called an integrated flight control system (IFCS) by some manufacturers; Others may use the term automatic flight control system (AFCS).
  • 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 Director/Autopilot Controls

Flight Director/Autopilot Controls
  • The FD/AP system may be employed at the following different levels:
    • Off (raw data).
    • Flight director (computed commands).
    • Autopilot.
  • With the system off, the FCI operates as an ordinary attitude indicator.
    • On most FCIs, the command bars are biased out of view when the FD is off.
    • The pilot maneuvers the airplane as though the system were not installed.
  • To maneuver the airplane using the FD, the pilot enters the desired modes of operation (heading, altitude, navigation (NAV) intercept, and tracking) on the FD/AP mode controller.
    • The computed flight commands are then displayed to the pilot through either a single-cue or dual-cue system in the FCI.
    • On a single-cue system, the commands are indicated by "V" bars.
    • On a dual-cue system, the commands are displayed on two separate command bars, one for pitch and one for roll.
    • To maneuver the airplane using computed commands, the pilot "flies" the symbolic airplane of the FCI to match the steering cues presented.
  • On most systems, the FD needs to be operating to engage the autopilot.“
    • At any time thereafter, the pilot may engage the autopilot through the mode controller.
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    • The autopilot then maneuvers the airplane to satisfy the computed commands of the FD.
  • Like any computer, the FD/AP system only does what it is told.
    • The pilot should ensure that it has been programmed properly for the particular phase of flight desired.
    • The armed and/or engaged modes are usually displayed on the mode controller or separate annunciator lights.
    • When the airplane is being hand-flown, if the FD is not being used at any particular moment, it should be off so that the command bars are pulled from view.
  • Prior to system engagement, all FD/AP computer and trim checks should be accomplished.
    • Many newer systems cannot be engaged without the completion of a self-test.
    • The pilot should also be familiar with various methods of disengagement, both normal and emergency.
    • System details, including approvals and limitations, can be found in the supplements section of the AFM/POH.
    • Additionally, many avionics manufacturers can provide informative pilot operating guides upon request.

Flight Management System Failures

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

Conclusion

Conclusion
  • Autopilots, navigation systems, and automation in general is only as helpful and can only enhance situational awareness and safety if the pilot knows how to use and interpret it's data
    • Pilots must take the time to understand their systems, as they can differ significantly from airplane to airplane.
    • Consider if the autopilot can outperform your aircraft's limitations, when it will and will not engage/dissengage and to practice those procedures.
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References

References