July 1, 2000
By Thomas A. Horne
You're coming to the end of what has been a well-executed night instrument approach. The weather is at nominal precision approach minimums—a 200-foot ceiling and a half-mile visibility. The localizer and glideslope needles are centered, and you're still in the soup as you descend to decision height. You catch a glimpse of what appear to be approach lights, fixate on them, and descend some more, certain that the runway will be the next thing you'll see.
What you don't see is the glideslope needle drifting toward the top of the instrument face.
There's something strange about this approach lighting system, you begin to think. There are no flashing lead-in lights, just a single row of steady-burning lights—and no roll-alignment lights yet, either.
Then you realize. These aren't lead-in lights at all. These are highway lights, stretched out along the edge of a road that just happens to be on the same general heading as your final approach course. You can see road signs much too clearly to be at a safe altitude. You check your ILS needles, and you are terrified to see that you're three dots left of the localizer and that the glideslope needle is pegged at the top.
What to do? Announce and perform a missed approach, of course. Climb like your life depends on it (it does), turn toward the inbound course, intercept it, and fly to the missed approach point. Later, you'll have time to figure out how things could have gone so awfully wrong. You'll come to several conclusions—all of which will be very familiar to safety experts and aviation accident analysts. That's because the time between breaking out from instrument weather and transitioning to visual flying has proven to be one of the more dangerous parts of flying an instrument approach—especially if the weather is at minimums, you're hand-flying the approach, you're flying to an unfamiliar airport, it's a nonprecision approach, circling is involved, it's night, and high terrain is a factor.
In other words, in the last moments of an instrument approach—the few crucial seconds you spend switching from the gauges to setting up for the landing—there can be deadly traps, illusions, and temptations. You fight these by sticking to a standardized set of procedures and maintaining situational awareness right down to the runway. Here are a few tips to bear in mind:
Good landings are the result of good approaches. You've heard this before, and it's true. Make sure you're all set up for the approach before you reach the final approach fix. This means having your target power settings, configuration, airspeed—and the appropriate altitude—nailed well before you intercept any final approach courses.
Use your instruments to maintain situational awareness. If you have a moving-map display, then by all means follow your progress as you work your way to the airport. For precision approaches having locator outer markers (LOMs), your ADF needle can be a great help in orienting you to the final approach fix. In other words, know where you are at all times during the approach.
Mind your altitude. You did plug in the latest altimeter setting, didn't you? In colder temperatures and around high terrain this is especially important. ATIS, AWOS, or ASOS can give you the altimeter setting, and so can controllers. When flying an ILS, be sure to note the glideslope altitude at the outer marker; this is published on approach charts. Then note your altitude as you intercept the glideslope, the needle centers, and you cross the marker during your approach. If your altitude is different than the published altitude, you could be flying along a false lobe of the glideslope signal. The only way you'll know if you're really on glideslope is to cross-check that published glideslope altitude with your own.
Get stabilized, and stay that way. Here's what you want as you descend along the final approach course:
Stay on the gauges until reaching MDA (minimum descent altitude) or DH (decision height). Sneaking a look is what got our pilot in trouble back at the beginning of the article. Fly instruments until you spot the airport environment—meaning the approach light system, the runway itself, or any part of the "runway environment" as described in FAR 91.175 (c) (3).
Don't "duck under." The only time you can go below MDA or DH is if you have the runway environment in sight. Just because the ATIS or ASOS says you should break out at a certain altitude, or that the visibility is above minimums, doesn't constitute permission to fly below MDA or DH. The regulations say flight visibility is what counts—meaning the visibility from your vantage point in the cockpit. The ceiling and visibility you're provided from ground-based resources may be radically different from what you see, and many times you can see farther than what automated systems may report.
Beware the circling approach. Most airlines forbid them, and for good reason. Does banking at low altitude and a relatively slow airspeed sound like a good idea? Throw in an unfamiliar airport, night, and high terrain, and you've got a recipe for losing sight of the runway. That and losing your prescribed track radius and altitude as you divide your attention between looking outside for the airport or runway, and scanning the instruments to make sure you have your airspeed and altitude under control. Also, keep in mind that you must maintain MDA on a circling approach until you are lined up with the extended centerline of the runway. So, no descending until after you've circled. This sets you up for the next warning.
Nonprecision approach? Get ready for a slam-dunk arrival. Nonprecision approaches have MDAs of approximately 500 feet agl. By the time you spot the airport, you could be too high for a normal, three-degree descent profile to the runway. The temptation is to dive for the runway. Try not to do it. You'll end up with a big descent rate and excess airspeed—an unstabilized approach—as you reach the runway threshold. If the runway is shortish and slick with rain or slush, you could slide off the end. To avoid the slam dunk, subtract a minute or so from the published approach time. This will give you more time to set up for the final, visual part of the approach. When this calculated time is up, and you don't see the runway, then consider a different approach—or a precision approach at an alternate airport. The VDPs (visual descent points, used on some straight-in, nonprecision approaches) published on some approach charts are designed to help pilots see the runway in enough time to make a normal descent to the runway, and avoid a slam-dunk final. If you haven't seen the runway by the VDP, then you know that you'll need an aggressive descent rate to make the runway. Too bad VDPs are being phased out.
Be ready for the missed approach. This is a big, big item. Patchy ground fog can roll in and obscure what, moments before, had been a clear shot at the runway environment. Automated and human weather observers may not be able to report the weather at the approach end of the runway. A front passes through. Any number of things can turn what was advertised as an "ice cream" IFR day into a white-knuckle adventure and a scary low approach. So be spring-loaded for a missed approach. Don't be timid about making the decision to miss, and don't change your mind once you've begun the procedure.
Ultimately, the best strategies for safely breaking out are to think far ahead of the airplane and not tolerate any deviations from standard procedures. That's easy to say, but a little harder to comply with when the weather's down and you want desperately to be on the ground.
AOPA Pilot Editor at Large Tom Horne has worked at AOPA since the early 1980s. He began flying in 1975 and has an airline transport pilot and flight instructor certificates. He’s flown everything from ultralights to Gulfstreams and ferried numerous piston airplanes across the Atlantic.
Safety and Education,
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