Flight Management & Autopilot Systems
Flight Management Systems accept inputs from a variety of sensors and provides guidance through all phases of flights to reduce workload.
Introduction to Flight Management & Autopilot Systems
- 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
- Test your understanding of Flight Management & Autopilot Systems by applying your knowledge in the interactive scenario, comparing your performance against the applicable Airman Certification Standards, and concluding with the topic summary to reinforce the key concepts before moving on to the next lesson.
Flight Management & Autopilot Systems Key Highlights
- Flight management and autopilot systems assist pilots with navigation, aircraft control, workload management, and flight automation.
- Flight Management Systems (FMS) integrate navigation, performance, route planning, and avionics data into a centralized control system.
- Autopilot systems can maintain heading, altitude, airspeed, navigation tracking, and vertical flight profiles automatically.
- Modern avionics integrate GPS, RNAV, autopilot, and electronic flight display systems to improve operational efficiency.
- Pilots must understand system modes, annunciations, and automation logic to manage automated flight safely.
- Improper automation management can lead to mode confusion, loss of situational awareness, and operational errors.
- Pilots remain responsible for monitoring aircraft performance and maintaining overall command authority during automated flight.
- Autopilot systems may disconnect automatically during system malfunctions, unusual attitudes, or excessive control inputs.
- Regular cross-checking of flight guidance information and navigation data helps ensure automation accuracy and reliability.
- Understanding flight management and autopilot systems improves workload management, navigation precision, and overall flight safety.
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
- Position/attitude based: gyro senses wing position
- Modern systems may combine the above
- Modern autopilots are digital
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Autopilot Use During Climb:
- Use of IAS holds allow for Vx and Vy climbs
- For a climb, IAS or flight-level-change mode generally provides better airspeed protection than vertical-speed mode because the autopilot adjusts pitch to maintain the selected airspeed as available climb performance decreases; a vertical-speed climb requires close airspeed monitoring because the autopilot may progressively increase pitch while airspeed decays.
- Use of IAS holds allow for Vx and Vy climbs
-
Autopilot Use During Descent:
- Use of VS holds allow for hitting descent planning numbers
- For a typical piston-airplane descent, vertical-speed mode generally produces a predictable descent rate while the pilot adjusts power to control airspeed; IAS mode may be preferable when a specific airspeed must be protected, including during turbulence or certain terminal operations.
- Use of VS holds allow for hitting descent planning numbers
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Autopilot Use in Controlled Airspace:
- Use of functions like IAS hold allow for setting ATC restrictions
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. "
- 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
- Pilots might expect to experience a troublesome autopilot, but not necessarily one that won't disengage
- In the event an autopilot won't disengage, consider alternative means like moving the controls or trim and even pulling the appropriate circuit breaker
Flight Management & Autopilot Systems Interactive Scenario
Interactive Scenario
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Flight Management & Autopilot Systems 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.
- Understand the autopilot's operating limitations, know when it will engage or disengage, and practice the applicable procedures.
- Periodically practice appropriate training tasks without automation or moving-map guidance so that basic aircraft control, pilotage, navigation-radio use, flight planning, and workload-management skills remain available if electronic equipment fails.
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