Technique: Missed Approach Musings

Being spring-loaded for the missed approach

October 1, 2008

Those of us who are instrument rated and current practice missed approach procedures on a regular basis—in VFR weather. But a real-world missed approach in below-minimums weather is something altogether different. There’s no hood or Foggles to yank off in a moment of indulgence, none of the self-assurance that comes from knowing that it’s really severe clear beyond the windshield. In the real world, missed approaches can be scary and frantic. As you scramble to reconfigure the airplane for a climb, or maybe a climbing turn, worrisome thoughts can break your concentration: Should I try for another approach? Hold and hope the weather improves? Go to the alternate right now, or later? Go somewhere else? How much fuel do I have? Where is the nearest area of better weather?

Because considerations like this can creep in and compromise your instrument scan and judgment so easily, it’s vital to have a good grip on missed approach issues. What follows are some basic guidelines.

Briefing the miss

It’s important to go into an into an instrument approach firmly believing that you will miss the approach. This helps you concentrate on preparation for the upcoming missed approach procedure. Study the approach plate with a special eye on the information blocks devoted to the miss.

Luckily for us, missed approach directions are presented in both text and graphic form. It’s up to you, but many pilots find the graphics easier to comprehend. There can be as many as four separate steps in the complete procedure, so the best tactic is to memorize the first two steps. That’s the most you can hope to remember in the tense moments after declaring a miss, but it’s enough to get you on your way. Later in the missed approach procedure, you can check the subsequent steps to make sure all falls in line. Here’s where a second pilot—or even an aviation-savvy front-seat passenger—can help read off the steps.

True, air traffic control (ATC) may issue you vectors after you declare a missed approach—and yes, declaring a missed approach is one of a pilot’s responsibilities, as stated in Section 5-5-5 in the Aeronautical Information Manual (AIM)—but it’s best to be prepared to fly the missed approach procedure as published. That goes double if you’re in a mountainous area, or at an airport without radar service.

In almost every case, the first step in a missed approach procedure is a straight-ahead climb to a designated altitude. Which is good, because this minimizes task loading. More complicated procedures that involve climbing turns to intercept a VOR radial, then follow that radial to a fix defined by a cross-radial from another VOR, can be extremely taxing, and demand all your instrument flying skills. This argues for setting up your navaids prior to shooting the approach—so as to be well prepared for what may come, and minimize confusion.

Panel set-up

Of course, your primary concern during the approach phase is tracking the final approach course guidance. But be sure to pay attention to setting up your navaids for the missed approach procedure well in advance of reaching the initial approach fix. It’s impossible to give specific instructions for this, owing to the great diversity in navaids. Modern, big-screen integrated, moving-map glass-cockpit equipment—such as Garmin’s G1000 and Avidyne’s Entegra—as well as comparatively “small screen” moving-map GPS/nav/com gear may make this task very easy. For example, the missed approach procedure is usually loaded when the approach is loaded. When the missed approach point (MAP) is reached, the display guidance more or less automatically changes to give the proper guidance through the miss. We say “more or less” because each GPS/nav/com can have a dramatically different sequence of inputs.

Some navigators, such as the new WAAS (Wide Area Augmentation Service)-capable units, really do automatically switch to missed-approach flight plan guidance. Should you be lucky enough to have a flight director, the drill then becomes flying the command bars through the missed approach procedure—or following ATC vectors, as the case may be. With other older units, such as the non-WAAS-upgraded Garmin 430/530 series of GPS/nav/com receivers, you must first push an “OBS” button to invoke the missed approach guidance.

What happens next depends, again, on each individual receiver. You may be prompted to fly direct to the first fix in the missed approach procedure. But be forewarned. The published guidance on the approach plate takes precedence. You may have to make a climbing turn, for example, before flying to that first fix. Today’s GPS/nav/com boxes can vary widely in their “knobology” and operating logic.

Some GPS navigation units can be so non-intuitive that many pilots confess to falling back on the old, tried-and-true VHF-based electromechanical guidance they learned on!

“Old-school” setup

So much for the vagaries of flying with modern panels of the kind found in technologically advanced aircraft. For the bulk of us who use conventional, electromechanical course deviation indicator (CDI) nav heads instead of electronic displays with moving maps, preparing for the missed approach can be more straightforward. Hopefully, you have two nav heads. The primary HSI/CDI can be set up for the final approach course. The second CDI can be used for guidance along the first leg of the missed approach procedure—again, subject to the mandates published on the approach plate. Things get interesting if you have to use the second CDI for a dual purpose, like showing crossing-radial information on a final approach course—say, for a final approach fix (FAF) or step-down fix—and have to switch back and forth from the crossing fix’s radial and frequency to the missed approach’s radial and frequency. Talk about being busy on the final approach course!

I started flying on instruments in the 1970s—the golden age of electromechanical navigation. Thinking about it now, I wonder how we got along as well as we did. Why? Today’s moving maps provide invaluable safety enhancements. Chief among them is situational awareness. With a glance at our symbolic airplane on the moving map, we know exactly where we are with relation to the instrument approach course, airport, terrain, navaids—and missed approach tracks. Much more mental gymnastics are required when all you have are a pair of needles and a paper chart or two.

Today’s electronic approach charts, as depicted on modern large-screen multifunction displays (MFDs), are worth their weight in gold when it comes to flying missed approach procedures in the soup. With an MFD, there’s little question as to your position, which way you must steer to make good a course, and where traffic, terrain, obstacles, and strong precipitation returns are located.

Decision time and place

So when and where is the MAP? With GPS and moving-map displays the answers are right there on the screen; you can watch your symbolic airplane. But it’s always good pilot practice to run the numbers yourself. Besides, you never know when your equipment may “flag out” on the final approach course. That would be rare—except in a hard-core simulator session—but it can and does happen. That’s when you revert to that 70s-style electromechanical world, assuming you have such a back-up capability.

With a precision approach, such as the instrument landing system (ILS), the MAP occurs at decision altitude (DA). With WAAS approaches having vertical guidance, the MAP happens at DA—which can be as low as 250 feet above the airport elevation. As the name implies, when you reach this place it’s time to decide: Can you see enough of the runway environment to safely land? If so, proceed, keeping the localizer and glideslope needles centered all the way to the touchdown target zone—about 1,000 feet from the runway threshold. If not, begin climbing immediately. The DA is typically located at the following combination of variables:

  • 200 feet agl above the runway threshold elevation;
  • Five or so nm beyond the final approach fix;
  • One-half mile from the runway threshold;
  • Over the middle marker (if the ILS has one);
  • At a DME fix from an ILS-DME frequency serving the ILS approach.

There’s an additional way to help confirm the MAP on an ILS approach. It involves figuring out elapsed time from the FAF, and assumes a constant descent rate and constant groundspeed. Lucky for us, those groundspeeds, descent rates, and elapsed times are summarized on the approach plate. Just remember that we’re talking about groundspeed here, not airspeed.

Non-precision approaches (those without vertical guidance) also use this method to determine the MAP. Of course, GPS receivers do a great job reporting groundspeeds, as well as keeping track of distance to the MAP. Again, here’s where a moving map earns its keep. In addition to elapsed time, non-precision approaches have MAPs with these general characteristics:

  • 500 feet or more above the threshold elevation;
  • Approximately five nm beyond the final approach fix;
  • At the runway threshold in some approaches;
  • At a certain DME fix; or
  • At the navaid serving the approach, in cases where the navaid is located on the airport.

Of course, these are broad generalizations; be sure to check your approach plates for the exact information on the MAP. Be extra sure in the case of RNAV GPS non-precision approaches with LNAV or LNAV/VNAV guidance—though in many cases these approaches also have their MAPs over the runway threshold. It’s just that you have the luxury of some vertical guidance in the case of RNAV approaches with LNAV/VNAV minima.

Deadly traps

The biggest traps during the missed approach tend to be set by an urgency to get on the ground. Example: Just as you arrive at the MAP, you catch a glimpse of the runway through breaks in the clouds. It can be tempting to either dive to the runway through a cloud break, or circle around for what you hope is a better setup for the landing. But both these temptations can be deadly.

Remember that in the case of an ILS, you’re at a mere 200 feet agl. Any circling invites a crash into terrain or obstacles. On a non-precision approach, you’re at some 500 feet agl, so any diving to the runway is likely to be followed by an increase in airspeed, lots of floating on the runway, and an overrun off the departure end—especially if the runway surface is wet or icy.

All this is bad enough. But the biggest danger is that by trying to squeeze through low clouds you could enter more clouds while simultaneously trying to rack the airplane around for what you hope is a successful attempt to land visually. This invites a loss of control at low altitude. The moral: Fly the missed approach procedure unless you have the prescribed visual references as set out in FAR Part 91.175 (c). Here’s the first part of that passage, summarized and abridged for simplicity (check the regulations for the full scoop):

“No pilot may operate an aircraft below the authorized minimum descent altitude or decision altitude/decision height unless the aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers.”

The rule goes on to say that at least one of the following visual references for the intended runway must be distinctly visible and identifiable to the pilot flying both non-precision approaches and Category I ILS approaches. (Category II ILS approaches require special pilot certification and typically have 200-and-1,800-foot runway visual range (RVR) and 100-foot-and-1,200-foot RVR weather minima, respectively):

  • The threshold
  • The threshold markings
  • The threshold lights
  • Runway end identifier lights
  • The visual approach slope indicator
  • The touchdown zone or touchdown zone markings
  • Touchdown zone lights
  • The runway or runway markings
  • The runway lights

Can’t make a normal landing? Can’t see one of the above? Then it’s time to climb, right now. And don’t look back.

E-mail the author at tom.horne@aopa.org.