New ground-avoidance system uses Cold War technology
It may be hard to believe, but airliners that seem to be operating perfectly often crash into the ground. That's what happened to an American Airlines jet in Cali, Colombia, in 1995. The problem is that pilots get lost, and by the time the existing ground-warning system barks "Pull up! Pull up!" it may be too late. (Among the factors contributing to the Cali crash were confusion about navigation, and poorly timed deployment of panels meant to slow the plane.)

This kind of crash, which often occurs in clouds or at night, is a major threat to aviation. It killed Commerce Secretary Ron Brown and his fellow travelers last spring. In fact, the Flight Safety Foundation, a non-profit industry group, calls "controlled flight into terrain" the greatest single risk to aircraft, crews and passengers. Citing Boeing statistics, the Foundation says such accidents killed more than 3,000 people in Western-built jet planes between 1979 and 1991.

Since 1974, when the Federal Aviation Administration directed airlines flying in the United States to install ground-warning systems, these crashes have grown considerably more rare. But these warning devices are not perfect since they depend on the plane's altimeter, a machine that looks down (to ground the plane has already passed) not forward (to ground it could hit). The older systems give pilots 10 to 30 seconds to respond, gun the engines and climb out of danger. Sometimes, as in Cali, that's not enough.

So if you really don't want to smash into a parking lot...
Two U.S. airlines -- American and Alaska Airlines -- recently announced plans to install a new avoidance system that relies on technology that didn't exist when the first warning systems were built. These devices use global positioning satellites (GPS) to locate the plane on a digital map of global terrain.

GPS is a system of satellites that send signals to portable receivers which measure how long the signals take to reach them. From the travel time, the receivers calculate the distance to each satellite, and then figure out exactly where it is located in space. (Here's an introduction to the technology.)

Digital terrain map of the Apenine mountains in Central Italy produced by The Italian Processing and Archiving Facility. Courtesy of The European Space Agency.

Like GPS itself, the digital terrain maps were state secrets during the Cold War, since governments feared they would be used to help cruise missiles and other nasties reach their targets. Today, government digital maps are available, as are terrain maps being created by private satellites.

The new warning system has a readout on the instrument panel that shows any ground within 2000 feet of the plane's altitude in green. Yellow indicates terrain that is somewhat above the plane's altitude. Red -- you guessed it -- is reserved for land that's so high it poses the most acute hazard.

By looking ahead -- searching its digital map-- the warning system can locate in advance unwanted mountains or pesky office buildings that threaten the passengers' prospects of having a nice day. The system is intelligent enough to search straight ahead when the plane is cruising level, down a sloping flight path when it's descending, and on a curve if it is banking.

The new system will combine the existing "look-down" warnings with the futuristic "look-ahead" warnings, all for a package price of only $56,000 -- "less than 1/10 of 1 percent of the purchase price of many new transport aircraft," as the manufacturer helpfully notes. (Just in case you were thinking of buying one... Never know when you'll need to avoid a mountain in your Bronco.)

Interested in another way to stay stay above the fray?

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