AIRSPACE

Navigational Reference System

In place since 2005, this extensive and underused waypoint grid above FL180 already provides direct routing using only 5-character waypoint names throughout the United States.


Jeppesen high-altitude enroute chart. NRS waypoints are circled in red.

Preplanned routes are also developed to facilitate heavy traffic flow to various holiday destinations, major sporting events and other similar occasions. These “play book” routes and the newer “wind routes” into just a few east coast US cities take advantage of the NRS as it was intended.

Aircraft no longer have to zigzag across the country on an antiquated ground-based navigation route structure.

Tactical use

Where the NRS waypoint structure can perhaps make a large impact for both pilots and controllers is in tactical situations, ie, one that is not preplanned but results from a dynamic event such as severe weather.

Both pilots and dispatchers can now use charts or software for considering NRS waypoints during times of rerouting. No longer do operators have to go more miles then necessary when deviating around weather, such as proceeding direct to a VOR that may be further than what is really needed or making frequent requests for vectors to get around the weather on an already saturated voice communications system.

Usually, miles can be shaved off and turns around weather can be made sooner by using NRS waypoints, rather than remaining on vectors for extended periods. This also offers the benefit for controllers of preventing having a sector full of aircraft on vectors, which creates a tremendous workload.

Limitations

Although NRS waypoints offer many benefits to the NAS, the system is not without its limitations. Pilots have expressed concerns that tactical usage is challenging because NRS waypoints are not displayed on their MFDs unless they are already part of the programmed flightplan.

Unlike other navigational fixes that can be toggled on/off via a flight management system (FMS), NRS waypoints are not displayed (Burian, 2010). It also makes time critical tactical rerouting challenging for pilots.

This makes using NRS waypoints for deviating around significant weather much more challenging since there is frequently little time to find the aircraft’s location and develop a course of action while looking at an information-saturated high altitude chart.

In some cases, FMS data­base memory capacity has also been problematic. The extensive number of NRS waypoints can cause some databases to approach or reach their memory capacity. With the proliferation of RNAV procedures for the foreseeable future, this will only become more of an issue.

Many aircraft operators have been forced to remove some NRS waypoints in order to stay within memory limitations of some FMS databases. Although there are several other limitations to the NRS waypoint system, they are beyond the scope of this article.

Still, most users should find these waypoints beneficial to their flight operations above FL180. FAA, with the help of NASA Ames researchers, is currently studying the NRS waypoint system to see if systemwide improvements are possible to increase usability for more operators in the NAS.

Although not a panacea for many of the airspace issues facing the industry today, NRS waypoints do offer most operators increased efficiency, greater routing flexibility and another tool for tactical rerouting. Further enhancements to the system will only serve to benefit all users of US airspace.

Shawn Pruchnicki is a CRJ200 captain for Comair Airlines. He is ALPA’s national director of human factors and vice-chairman of his local ALPA safety committee. Pruchnicki also teaches system safety, human factors and accident investigation.

 

 

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