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Moving Maps (Part Two)

in Information Systems

Maintaining Proficiency: Spatial Reasoning Skills

Consider the CDI shown in Figure 5-8. What is the position of the aircraft with respect to the VOR station? Interpreting this type of display requires more effort than interpreting the moving map, which automatically displays the solution to the position-finding problem. Pilots should expend the effort to practice this skill set. Those who learn to navigate using ground-based radio navigation aids are forced to develop spatial reasoning and visualization skills, but a Federal Aviation Administration (FAA) study showed that this type of skill tends to fade quickly when not used. Be sure to keep your spatial reasoning and visualization skills sharp.

Figure 5-8. Can you determine your position from a simple CDI?

Figure 5-8. Can you determine your position from a simple CDI?

Failure Indications

Failure indications on the moving map can be quite subtle. The MFD in Figure 5-9 reflects a loss of position information, indicated by the removal of the aircraft symbol, compass labels, and other subtle differences. Be familiar with the failure indications specific to your equipment.

Figure 5-9. An MFD indicating a loss of position information.

Figure 5-9. An MFD indicating a loss of position information.

Common Error: Using the Moving Map as a Primary Navigation Instrument

The rich detail offered by the moving map display invites you to use the display as a primary navigation instrument, but you need to resist this temptation. The moving map display is designed to provide supplemental navigation information, but is not approved as a substitute for primary navigation instruments. The moving map is not required to meet any certification standards for accuracy or information as are the primary navigation CDI and related system components. Bear in mind that the apparent accuracy of the moving map display can be affected by factors as simple as the range setting of the display. An aircraft 10 miles off course can appear to be centered on an airway when the range is set to cover great distances.

Awareness: Overreliance on the Moving Map

With the position of the aircraft conveniently displayed at all times on a color screen in front of you, it is easy to let the computers do the work of monitoring flight progress. Numerous studies have demonstrated that pilots have a tendency to monitor and process navigational information from conventional sources (e.g., outside reference or conventional navigation instruments) much less actively when a moving map display is available. In a National Aeronautics and Space Administration (NASA) study, two groups of pilots were asked to navigate along a circuit of checkpoints during a VFR cross-country flight.

One group navigated using a sectional chart and pilotage. The other group had the same sectional chart plus an RNAV computer and a moving map. After completing the circuit, both groups were asked to navigate the circuit again, this time with no navigational resources. Pilots who had navigated with only the sectional chart performed well, finding the checkpoints again with reasonable accuracy. The performance was less favorable by pilots who had the FMS/RNAV and moving map available. While half of these pilots found the checkpoints with reasonable accuracy, one-fourth of the pilots made larger errors in identifying the checkpoints. The remaining pilots were wholly unable to find their way back to the airport of origin. This study makes two important points:

  1. The existence of information about aircraft position and geographical surroundings in an FMS/RNAV and moving map display does not mean that the pilot maintains true situational awareness or involvement with the operation of the flight to a degree needed for a safe outcome.
  2. The key to the successful use of a moving map display is to use the display as a supplement—not a substitute— for active involvement in the navigational process.

What does it take to use a moving map and remain “in the loop,” or situationally aware? In a second NASA study, pilots who used an FMS/RNAV and moving map display were asked to act as “tour guides,” pointing out geographical features to a passenger while navigating the same set of cross-country checkpoints. When confronted with a surprise request to navigate around the circuit again with the FMS/RNAV and map turned off, these pilots performed as well as anyone else. The simple task of pointing out geographical features was enough to avoid the out-of-the-loop phenomenon.

A moving map provides a wealth of information about your route of flight and gives you the opportunity to consider many similar questions along the way. Where would you land if you lost engine power? Which alternate airport would you use if weather at your destination deteriorated below minimums? Which nearby VOR stations could be used (and should be tuned as the flight progresses) in the event that the global positioning system (GPS) signal or other RNAV navigation data source is lost? Is a more direct routing possible? Diligent pilots continually ask questions like these.


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