August 1, 2011
The Activate Vectors to Final (VTF) feature on all modern Garmin navigators, from the GNS 400 up to the G1000 and its derivatives, was revolutionary when introduced. Before this feature, when a pilot received vectors for an approach, the steps to properly configure the GPS were numerous and often confusing. They typically required the pilot to move his hand—and attention—between the navigator, HSI or CDI, and a set of panel-mounted pushbuttons. The ability to condense several steps into one button push was unquestionably a great workload reducer.
Yet like so many other features of avionics automation, there is a dark side to the VTF function—one that can result in pilot confusion during the transition to an approach. In the high-speed world of jet flight, confusion on an approach is especially serious, as the time available to remedy problems is limited. At heart is the issue of what the VTF function actually does: It makes the final approach fix the active waypoint, with a selected course that matches the final approach course. With the exception of G1000-based systems running the newest software, it also removes all fixes prior to the FAF from the flight plan.
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Consider the ILS 33 into Burlington, Vermont. Because the Green Mountains run north to south 15 miles east of the airport, the procedure begins with several stepdowns before the glideslope can be intercepted. Imagine this procedure has been loaded into the navigator, and after ATC vectors the aircraft off the en route section, the pilot activates VTF. He is then given the following clearance: “Fly heading 350 and intercept the localizer, cross JANUD at or above 7,000 feet, cleared for the ILS DME 33.”
The problem is that once established on the final, the pilot—now looking for distance to JANUD—will only see distance to EHIKO, the FAF, prominently displayed. Even worse, for many installations, JANUD, as well as NIDUQ and HONIB after, will not appear at all on the MFD or in the list of flight-plan waypoints. The pilot may now be left rapidly trying to reload the approach without vectors, or to determine an alternate method of identifying JANUD. Because this approach requires careful energy management, it is no time to be scrambling.
For this reason, many instructors recommend that approaches not be loaded with VTF as the transition unless the pilot is very familiar with the approach and certain that guidance relative to fixes outside the FAF will not be needed. When loading the ILS 33, the pilot is given the choice of JANUD as a transition. Selecting this, all the fixes from JANUD on will be loaded into the flight plan. Then, once the approach itself is commenced, activating the approach (not VTF) will result in JANUD becoming the active waypoint, with NIDUQ and HONIB ready to appear in sequence. For added situational awareness the pilot may, via OBS mode or the Direct button, select a course to JANUD that matches the final approach course. This results in an approximate re-creation of VTF’s long final drawn on the MFD. It is important to emphasize that this “final” is for situational awareness only, and the pilot must navigate referencing the localizer.
Another issue illustrated here is the importance of utilizing all navigation information available to the pilot. The ILS 33 localizer supports DME information, so ensuring the DME is tuned correctly, and displayed prominently, will provide the pilot with another means of identifying the fixes prior to EHIKO. This is a good practice to use on every approach, yet many pilots get out of the habit as they become accustomed to GPS providing all needed information.
Neil Singer is a Master CFI and a mentor pilot in Cessna and Embraer jets.
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