June 9, 1999


I was amused last week to see a TV reporter state that ". . . computerized weather radar showed that there were severe thunderstorms approaching the airport just as the aircraft landed . . ." She was reporting the image, not the weather itself. Wouldn't it have made more sense to have said that the plane landed moments before a terrible storm engulfed the airport?

This apparent shift of reality goes beyond TV though. I have observed flight instructors walk up to a weather terminal and call up the most recent radar image, and decide not to fly a lesson . . . even though the sky outside showed no sign of impending weather. I have watched trusted friends dial the automated weather station and listen to its computer-generated voice for wind information, rather than walk out the door and look at the wind sock.

I like wind socks. They do a good job of describing the wind that has set them into motion. In their most basic function, they show the direction of the wind because they are mounted on a frame that is supported by bearings. As the strength of the wind increases, it gradually inflates and extends the sock. Below five MPH, the sock stays bent enough to have kinks in it, but the kinks are about gone by the time a 10 MPH breeze softly fills it. A sock fully inflates at about 15 and becomes rigid above 20 MPH.

The sock also speaks plainly about the consistency of the wind. A sock which stands like a photograph, rarely showing a change in strength or direction, says that there is not likely that the pilot will have to perform a juggling act as he makes his way down the runway preparing to land. A sock which twitches like a cat's tail as it stalks a mouse says that the wind direction and strength changes more rapidly than the whole sock can respond to quickly enough. Only the tail has the flexibility to react to these quick changes, and it appears to move separately from the rest of the sock.

As technology marches on, the lowly wind sock becomes more and more of a bargain. A hundred dollar frame will last almost forever, and a thirty dollar sock will easily last a year. They are cheap enough to scatter around a large airport, and that is what is often done, even still. Often, there is a there are socks near the ends of each of the runways. On days with a twitchy wind, each windsock will show a different wind strength and direction.

Wind information comes to the pilot in many forms. As students build their proficiency with the airplane, I point out the wind socks to them as they near the runway. I also point out the motion of nearby trees, waves in long grass or cropland, ripples and lees on ponds, and the cats-paw marks of wind bursts on larger bodies of water.

Wind information also comes to the pilot by radio, but is of little practical value because it describes wind conditions that exist several minutes prior to landing, and at a location that is other than the landing area. I tell students to discount what the radio tells them and look at the sock prior to touchdown, but only for rough information.

The only wind that matters is the wind that actually exists in the landing area as the airplane skims over the runway, lands, and rolls out. All the perceptions and radio reports prior to that moment are only trends and expectations, the moments of landing are the reality. There is still nothing that can replace the perceptions and reactions of the human brain when our marvelous mechanical creations must negotiate the interface between technology and the real world.

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