|CHAPTER 4. Automated Flight Control
Using the Flight Director (FD)
Flight Director Without Autopilot
The FD and autopilot systems are designed to work together, but it is possible to use the flight director without engaging the autopilot, or the autopilot without the FD, depending on the installation. Without autopilot engagement, the FD presents all processed information to the pilot in the form of command bar cues, but you must manually fly the airplane to follow these cues to fly the selected flightpath. In effect, you “tell” the FD what needs to happen and the FD command bars “tell” you what to do. This adds to your workload, since you must program the FD for each procedure or maneuver to be accomplished, while actually flying the aircraft. In many cases, you will have a decreased workload if you simply disable the FD and fly using only the flight instruments.
Flight Director With Autopilot
When the aircraft includes both a flight director and an autopilot, you may elect to use flight director cues without engaging the autopilot. It may or may not be possible to use the autopilot without also engaging the flight director. You need to be familiar with the system installed. When you engage the autopilot, it simply follows the cues generated by the flight director to control the airplane along the selected lateral and vertical paths.
Common Error: Blindly Following Flight Director Cues
The convenience of flight director cues can invite fixation or overreliance on the part of the pilot. As with all automated systems, you must remain aware of the overall situation. Never assume that flight director cues are following a route or course that is free from error. Rather, be sure to include navigation instruments and sources in your scan. Remember, the equipment will usually perform exactly as programmed. Always compare the displays to ensure that all indications agree. If in doubt, fly the aircraft to remain on cleared track and altitude, and reduce automation to as minimal as possible during the problem processing period. The first priority for a pilot always is to fly the aircraft.
Common Error: Confusion About Autopilot Engagement
Pilots sometimes become confused about whether or not flight director cues are being automatically carried out by the autopilot, or left to be followed manually by the pilot. Verification of the autopilot mode and engagement status of the autopilot is a necessary technique for maintaining awareness of who is flying the aircraft.
The FD/autopilot’s navigation function can be used to guide the aircraft along the course selected on the navigation indicator. Since the navigation display in most advanced avionics cockpits can present indications from a variety of navigation systems, you can use the autopilot’s navigation function to follow a route programmed into the FMS using VOR, global positioning system (GPS), inertial navigation system (INS), or other navigation data sources.
Following a Route Programmed in the FMS
Figure 4-6 demonstrates how to use the navigation function to follow a route programmed into the FMS. With the navigation function engaged, the FD/auto-pilot steers the aircraft along the desired course to the active waypoint. Deviations from the desired course to the new active waypoint are displayed on the navigation indicator. When the aircraft reaches the active waypoint, the FMS computer automatically sequences to the next waypoint in the route, unless waypoint sequencing is suspended.
It is important to note that the normal navigation function provides only lateral guidance. It does not attempt to control the vertical path of the aircraft at any time. You must always ensure the correct altitude or vertical speed is maintained.
When combined, use of the FMS and the FD/autopilot’s navigation function result in an automated form of flight that was formerly limited to very complex and expensive aircraft. This same level of avionics can now be found in single-engine training airplanes. While it is easy to be complacent and let down your guard, you must continuously monitor and stay aware of automated systems status and function and the track of the aircraft in relation to the flight plan and air traffic control (ATC) clearance.
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