Flying Into a Fog Is Safer Than You Think

Feb. 8, 2006 — -- So it's the end of the flight, your captain has briefed you on the PA that you're landing on time despite fog ahead, and over the seat audio channel, which allows you to eavesdrop on controller-to-pilot radio exchanges, one of the pilots has just acknowledged the flight's been cleared for something called an ILS.

ILS?

"Roger, approach, BigBird 25 cleared for the ILS runway one-three, tower at the marker."

Fact is, you'd really like to know what the devil "ILS" means, but a quick rifling through the in-flight magazine reveals nothing but guidance on airport layouts and ads for learning French the easy way. Here's the explanation you can use to dazzle your seatmate on your next flight:

"ILS" stands for Instrument Landing System, a brilliant piece of technology now found in virtually every airliner's cockpit that lets us see an otherwise invisible pathway from a point perhaps 10 to 15 miles away from a fog-bound airport to a spot some 50 feet over the threshold of a runway -- an electronic ramp in the sky, so to speak.

If you've ever been aboard an airliner large or small in marginal weather, you've sat through an approach using this marvelous device. It's a piece of technological wizardry that finally emerged from testing into operational reality in January … of 1938!

That's right. Sixty-eight years ago. (There's an excellent history of the ILS here).

The fact that the ILS is still the mainspring of safe, all-weather landing capability worldwide doesn't mean the thousands of ILS systems are archaic and out of date; it merely shows how incredibly reliable and boilerplate the technology has become.

Flying a large airplane safely to a point over the end of a runway is pretty simple in daytime with crystal-clear weather. But when weather obscures the field and you can see nothing but gray outside, landing safely requires a precise, reliable pathway to make what we call a stabilized approach.