Page 16 - Volume 10 Number 9

PILOT KA SPEAK
Balancing
Your Backups
In Part 1, the article left off with GPS failures that would affect both primary and secondary GPS units (such as failures related to shared antennas, identical software bugs, satellite outages, or the loss of shared power sources or cooling equipment). In such cases, being able to revert to “old school” forms of navigation can sometimes be the only options left. We pick up the discussion there...
Very High Frequency Omnidirectional ange (VOR)
OR’s stations are cumbersome and expensive to maintain. Many have been shut down in recent years and an accelerated decommissioning
PART 2
true. However, it is more complicated than that. Because VOR radials emit in all directions from a VOR station, the width of a given radial is never constant. Instead it is ever-widening, from zero at the station to eight miles wide (or more) at triple digit distances from the station (taking into account, of course, the service volume of the VOR station in question [Figure 1]). Thus, VOR radials become less precise with increased distance from the station. This is not the case with GPS courses programmed to overlay VOR radials. Such GPS courses are constant in width and that width is subject to the Course Deviation Indicator (CDI) scale the GPS unit is set to (a setting that can be changed automatically as a function of software and aircraft position, or manually by the pilot). Additionally, VOR
by Matthew McDaniel
RV
schedule looms in the near future. However, while the number of VOR facilities may be on the decline, VOR navigation is a long way from disappearing, as Victor Airways (below FL180 in the United States) and Jet Airways (FL180 and above in the United States) are still in common use. Yet, the explosion of advanced avionics over the past decade-plus, has made it far more common to track such routes via GPS or FMS overlays of the actual airway. Regardless, pilots should still practice their airway and VOR radial intercepting and tracking skills, should the need arise to do so using an actual VOR signal as the sole source of navigation. Sadly, it has become all too common during training events to see pilots fumbling with their avionics to complete the simple (but unpracticed) tasks of tuning and identifying a VOR and selecting an assigned radial or airway. What was once IFR-101 has become an “advanced skill” in the age of glass panels and GPS. When was the last time you practiced these tasks?
It seems the procedures for intercepting and tracking radials should be the same, regardless of whether that radial is created by a VOR signal or is being mimicked by a GPS signal. At the most basic level, that is essentially
14 • KING AIR MAGAZINE
Figure 1: Aeronautical Information Manual (AIM), Figure 6-3-20, Frequency Protected Service Volume for VOR. This diagram details the service volumes (effective ranges) of the various VOR types in Above Ground Level (AGL) altitudes and straight-line distances. These numbers should be considered maximum numbers, as signals received beyond these parameters should be considered unusable. Other factors can further reduce the effective range of VOR signals, including (but not limited to) line of sight limitations, antenna capabilities and receiver condition.
SEPTEMBER 2016