Boy, was I disappointed! As I worked toward my instrument rating and studied a number of high-tech devices that guide our descent to the runway I thought an instrument approach was a wondrous statement of high-technology flight. By the end of my training, I came to understand something else:
FLYING AN IFR APPROACH IS just a matter of flying the right distance, in the right direction, at the lowest safe altitude, in hopes of seeing the runway and landing *visually*.
All instrument approaches are variations of these basics:
- an Initial Approach Fix
- a Final Approach Fix;
- a Missed Approach Point; and
- a Missed Approach Procedure
HOW IT WORKS: Fly from one to the next in sequence, reaching each at a prescribed altitude, and you’re flying the instrument approach…
Initial Approach Fix (IAF): The IAF is the point where you stop flying “en route” and start flying the approach — at a charted course and altitude. It’s the IFR equivalent of the interstate off ramp — take the airway (or GPS direct) to the IAF and you’re on the “published” approach procedure. From there, fly to the…
Final Approach Fix (FAF): From the IAF you descend to and fly at the published altitude until you get to the FAF, usually three to five miles from the airport. The FAF is where you “turn into the neighborhood,” in automobile terms, and begin your final descent toward the runway. Sometimes, especially when you’re given radar vectors to the approach, the FAF serves as the IAF as well. Just keep flying down the approach path until you get to the…
Missed Approach Point (MAP): This is the closest you can safely get to the airport while still in the clouds. If you reach the MAP (defined sometimes by altitude, other times by a distance from the FAF), can see the runway, and are sure you can visually maneuver for a safe landing, you can continue on down. If at the MAP you can’t see the runway, you must then fly the…
Missed Approach Procedure: “Flying the missed,” means climbing in a safe direction to a safe altitude, and going somewhere where you can decide what you’ll do next. Sometimes that may be another try at the approach. Other times it means going to another airport … preferably, one with better weather. If you’re cleared for the approach you’re also cleared for the missed approach procedure, but Air Traffic Control may have to park you some place (in a “holding pattern”) until they can accommodate your after-the-missed decision.
WAIT, THERE’S MORE…
A precision approach gives you “vertical guidance”– almost always an electronic glideslope you can follow in a gentle descent toward the runway.
Example: At the FAF you start a gradual descent (usually around 500-600 feet per minute). If you hold heading and vertical speed you’ll end up (on most precision approaches) about 200 feet above the runway when you’re half a mile short of the threshold. That’s the typical precision approach missed approach point.
Non-precision approaches, on the other hand, point you toward the airport (though not necessarily lined up with any runway) and let you descend to a minimum safe altitude. The idea is to “break out” of the clouds far enough away from the runway to safely maneuver for a landing. Without “precision” descent guidance, most non-precision approaches have higher “minimums” (the lowest safe altitude and visibility) than precision approaches and they are flown at higher descent rates designed to bring you out of the clouds, further from the airport.
Example: A “standard” non-precision approach usually flown at a 800-1000 feet per minute descent rate, requires a mile visibility or more, with a “Minimum Descent Altitude (MDA)” of 500 feet above ground level.
THE VASTLY OVERSIMPLIFIED SUMMATION
- Cross the IAF at the published altitude, then
- descend on course to the published altitude before reaching the FAF. At the FAF,
- begin a gradual descent (a little steeper on non-precision approaches), going down to the lowest safe altitude before reaching the MAP. At the MAP,
- if you see the runway, land. If not, fly the missed approach procedure.