If you’ve flown in a Garmin glass cockpit with synthetic vision, then you may have seen the “Pathways” feature, a series of constantly moving rectangles on the primary flight display (PFD). Candidly, I’ve never liked Pathways, so I was delighted to recently find a good use for them. Best of all, this tip works in any Garmin glass cockpit with Synthetic Vision Pathways technology, so you can use it in anything from a G1000-equipped Cessna 172, up through Cessna business jets with the G3000 and G5000.
The following comes from my Max Trescott’s G1000 and Perspective Glass Cockpit Handbook:
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Subscribe Now“Pathways, also known as highway in the sky (HITS), guidance is provided by displaying a series of rectangles that a pilot flies through to maintain the desired course. NASA originally developed this concept, and [its] testing showed that it let pilots fly a more precise path, though at the cost of a pilot’s higher workload.
Positioning the Flight Path Marker (FPM) in the center of each rectangle should reduce the workload, though Garmin’s own testing showed that some pilots still find it easier to fly a course using the conventional flight director.
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“Most of the time, the rectangles are 700 feet wide and 200 feet tall. However, when flying an approach, the width is 700 feet or half of the full-scale CDI deflection, whichever is less. Also on approach, the height is 200 feet or half of the full-scale deflection of the vertical deviation indicator, whichever is less.
The rectangles are magenta when flying the active leg of a GPS flight plan, white when flying a GPS leg that is not active, and green when flying an ILS or localizer. Pathways are not displayed when leg sequencing is suspended, such as after the MAP before the SUSP soft key is pressed, or on any flight plan leg that would lead to intercepting a leg in the wrong direction.”
I’ve tried Pathways, and I find it more difficult to use than the flight director. Also, I prefer a clean PFD, as I feel that moving objects and blinking cursors tend to desensitize pilots from noticing new things that appear, such as changes in autopilot modes and new crew alerting system (CAS) messages. For example, in cruise with the autopilot on, Pathways add no information but are a constant distraction because they never stop moving.
While working with new Vision Jet pilots, I’ve found that they typically struggle in two areas. One is flying arrivals, and the other is flying visual approaches. Most of the time, jets fly long, straight-in instrument approaches, so pilots don’t get much practice approaching a runway from other directions. When approaching an airport on a long base leg, they often struggle to determine the correct altitude for joining the final approach. Without tools to assist them, they end up high or low on final.
There are some simple tools you can use in any airplane with a moving map. What I’ve coached pilots to do is to figure out roughly how many miles they’ll be from the airport when turning onto final.
For example, when aiming for the outside of a Class Delta ring on a moving map, you’re typically going to be joining the final at 4 miles from the center of the airport. On a normal 3-degree glideslope, you’ll descend at about 320 feet per nautical mile.
To simplify the calculation, use 300 feet instead of 320, and multiply by four miles to get 1,200 feet. Then, as you join the final, you’ll want to be roughly 1,200 feet above the field elevation to be on a 3-degree glidepath to the airport. That works well for short runways, say 3,000 feet or less. But for a long 10,000 foot runway, if you turn final 4 miles from the airport center, you’re actually closer to 3 miles from the runway threshold, so you may have to adjust your calculation for long runways.
But using Pathways simplifies the problem and works regardless of runway length or where you join the final. Here’s the tip. When flying a visual approach, load any approach with some kind of vertical guidance to the runway. It could be an ILS, or even one of the Garmin visual approaches. Then activate vectors to final. When you do that, Synthetic Vision Pathways will draw a series of moving boxes along the glideslope or glidepath.
Then when approaching the airport on a base leg, or from most any direction, adjust the pitch of the aircraft so that the PFD’s FPM is aimed at the moving boxes on the glideslope. The FPM is the green circle that looks a little like a gunsight. It’s near the center of the PFD, and it always shows the current path of the aircraft.
It’s part of Synthetic Vision, so if you don’t see it, either you don’t have that feature in your aircraft or it is not turned on.
Note that this technique works regardless of where you join the final. If you aim a little farther out from the airport, you’ll be joining the final at a higher altitude. If you aim closer to the airport, you’ll join the final at a lower altitude.
Best of all, the technique works equally well for short and long runways, as the glidepath is always aiming for a point about 750 feet beyond the runway threshold. And you don’t have to do any math. Just aim the FPM at the moving boxes on the glideslope.
I’ve tried it in a simulator and in an airplane, and it works equally well in both. So next time you’re on a visual approach, try it and see if it doesn’t bring you out exactly on the visual glidepath to the airport.
This column first appeared in the May Issue 958 of the FLYING print edition.