The Lost Art of Heading

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This article originally appeared in IFR magazine, Mar. 2006.

Flying the System

There is a chain of FBOs in the Midwest famous for warm cookies, parrots with rude vocabulary and impressive line ladies. The ramp full of airplanes indicates that pilots are attracted to, and distracted from, competing FBOs by these interesting things. Looking in the cockpit of our airplanes, it's clear that pilots are also attracted to the interesting avionics that bring a huge bandwidth of information into the cockpit. Whether the magic in the cockpit is a pair of 12-inch, color, flight displays, or handheld GPS with downlink weather and satellite radio, these tools improve our situational awareness and that's good. The problem is that a picture of the airport with the final-approach course line on the moving map can distract a pilot's attention just like the short shorts on the line girls at the Kansas FBO. Both are fun to look at, but when it really matters, what we should be watching is the CDI, the HSI, or the pretty girl's hands, to guide us safely to our destination. Bad habits creep into all areas of our flying and the solution is usually getting back to the basics. Our primary navigation instrument should be the HSI or the CDI (for simplicity's sake, we'll call either one a CDI). There are times when the ADF or RMI might be the primary instrument, but both are scarce in GA airplanes in the U.S. A moving map should be used for situational awareness. Using the moving map instead of the CDI will work, but -- especially if a glideslope is involved -- the results will be poorer than if the focus was on the CDI. The reason is simple: There are fewer instruments in our scan. Partial-panel IFR is a scary thing to talk about, but once the initial shock passes it's not that difficult. With fewer gauges to scan, we get back to them more often and the result is lower workload. Adding the moving map to our scan adds to the total workload and degrades pilot performance rather than helping it. Scanning the moving map to maintain situational awareness in a procedure turn or holding pattern is great, but once the final intercept angle is established, the CDI should become the primary navigation instrument. After joining the final approach course, an occasional glance at the moving map or the GPS ground track is useful to determine the distance from any step-down fixes or to confirm our reference heading.

Old-School Tracking

Garden City (KGCK) ILS 35 (excerpt)

The skill of nav-tracking using a reference heading is creeping out of our bags of pilot tricks. Some have other names for it, but the process is the same. It was more important before GPS ground track information was available, but is now much easier because we have that information. It's one of those skills that's so simple to understand, so difficult to employ, and so easy to atrophy. As a refresher for those who were taught this way and a definition for those who were not, the reference heading is the heading we fly that results in a ground track parallel with the desired course. Let's suppose we're headed to Garden City, Kan., (KGCK) to get some of those cookies. There is no radar coverage, and the Garmin GNS 430 has died. Does this sound like an emergency? It shouldn't, but let's be honest: We have all become so spoiled by GPS that it raises the hair on our necks a bit. The Garmin drives the HSI, of course, but the trusty old KX-155 was in our airplane long before the Garmin was dreamed of and it is perfectly capable of finding the end of the runway from an ILS approach. The question is: Are we?

Fly the Bug

The plan is the ILS Rwy 35. Arriving from the northwest, we drive to the VOR and turn outbound on a course of 169. Established on the 169 outbound, we tune up the localizer and join it south of the airport. We know the winds are out of the west, so as the needle centers we turn to our reference heading of 180 and wait. Our airplane has a heading bug, so we set that at 180. The needle starts moving left and we turn right. (Remember, we don't have an HSI, so this is reverse sensing.) We have determined that 180 won't hold the course so we need a new reference heading. Move the heading bug right five or 10 degrees; turning the airplane further right to the right edge of the heading bug yields a correction. When it centers, we turn back to the center of the heading bug. Holding that heading, the needle stops moving and we have found a good reference heading. If it moves again, we make a smaller adjustment and again turn to the edge of the heading bug until it centers again and then back to the reference heading. Passing the marker outbound, we have a reference heading at 182. The procedure turn is straightforward and after we return to intercept the localizer inbound, we set the heading bug for our new inbound reference heading. Our first guess is the published heading of 352 degrees less the outbound correction of 10 degrees and we set the bug at 342. As the needle centers, we turn to bug and wait. If we nailed the intercept, all we have to do is wait. If we missed it, we will turn to one edge of the heading bug until the needle centers and then back to the reference heading. Our primary effort is keeping the wings level. If the wings are level, our heading won't change. Small changes of the reference heading will stop any CDI needle drift. With the wind determined on the outbound leg, finding the inbound reference heading will be quick unless there is an error in the magnetic compass or heading indicator. Compass errors and heading indicator precession are common and will be magnified by the course reversal. Headwind switching to a tailwind also changes the correction, so don't be alarmed or surprised if the correction used on the outbound leg is significantly different than the inbound correction. Once the reference heading is found, it will probably not change much throughout the approach. There are exceptions to that rule, of course. If the winds at altitude are blowing from the northwest and the surface winds are from the east, we can anticipate a shear and a major change in the reference heading crossing the shear. Be ready. These shears often cause a layer of choppy air during the descent and when that happens, we're prepared for a significant change in reference heading. It might be a 15-degree right turn and, the moment we feel the bumps and see the needle start to move, we'll change the reference heading. If the GPS were working, we would take a peek now to establish our new reference heading quickly. That's it. Find the heading that parallels the course and correct it with small turns when the CDI is not centered.

Simplicity Itself

Track (TRK) information is about the handiest thing your GPS shows on approach. Flying a reference heading and verifying with Track yields a smoother approach every time.

An airplane equipped with a heading bug removes most of the thinking and the math, so our mental horsepower is reserved for things like remembering reverse sensing, timing legs, and tracking our altitude. We end up having only three choices: on-course and centered on the bug, correcting left on one side of the bug, or correcting right on the other. Really good pilots, or those flying fast airplanes, can use one-half the bug for even smoother corrections. There is no math and no remembering the heading, and crosswind correction numbers disappear from our thought process. Some airplanes don't have a heading bug and that takes a little more effort. The process is the same: Figure out the heading that it takes to parallel the course and then fly only three headings: on-course, correcting left or correcting right. If the correcting left or right heading is not moving the needle, that becomes your new reference heading; turn further to the appropriate correcting heading. Even though there is no heading bug, keeping the numbers and the math out of the process as much as possible makes it easier. Just turn until the reference heading is one hash mark left or right of the pointer. This is the secret that makes the difference between a smooth ILS and something that looks like Paul Bunyan's work with an ax. This basic process not only works for lateral navigation, it works for vertical navigation as well. The approximate descent rate on a three-degree glideslope is five times our groundspeed. If we use a 100-knot approach speed, our "reference rate of descent" would be 500 feet per minute. Crossing the marker is when we establish a 500-foot-per-minute descent and then adjust the descent rate to move the glideslope needle. Whatever the reference descent rate is, use it and increase or decrease the rate to center the needle. It is exactly the same process as the heading, and it works. The same caveat applies regarding windshear: If we feel some turbulence and we know there was a tailwind aloft and a headwind on the surface, add power the moment we see the needle start to rise and reduce the reference descent rate accordingly. All of this sounds so simple and it is. Those of us who learned to fly before moving maps and GPS flew the same approaches to the same airports in the same weather we do today and we did it very successfully. The good news is GPS makes the reference-heading process even easier. After the first estimate of a reference heading, hold it for a few seconds and then cross check it with the ground track (TRK) on the GPS. With no more than one adjustment, the new reference heading should be nailed. If, at that point, we eliminate the GPS from our scan -- for all but an occasional glance -- the result will be better, smoother and more accurate approaches. The biggest challenge of the new information age in the cockpit is to remember the basics and learn what is important and what to ignore. No one would argue that the improved situational awareness offered by GPS, moving maps, terrain avoidance, traffic avoidance and downlink weather is a good thing. The problem is the same as taxiing on the ramp in Kansas. We've got to remember to look at her hands.
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