Technology and Business; April 1995; Scientific American Magazine; by Gibbs; 2 Page(s)

When the London fog rolls in, pilots flying into Heathrow Airport turn on their instrument landing system receivers to pick up the radio beacons that will guide them safely through the soup and onto the runway. But those beams, steady for 50 years so far, may soon begin to rock and roll. In January 1998 European FM radio broadcasters will turn up the volume on their transmitters, some of which are located uncomfortably close--both on the ground and in the electromagnetic spectrum--to landing systems at major airports.

The world's aviation agencies planned for this contingency 20 years ago. The instrument landing system, everyone agreed, would be replaced in the mid- 1990s with a microwave landing system (better known as MLS). In addition to dodging interference by moving to a less crowded part of the spectrum, MLS would allow pilots to make steeper and curved descents, cutting noise and boosting airport capacity.