Terrain Awareness

February 11, 2010 by Bruce Landsberg

Despite last week’s collision between a tow plane and a Cirrus in Colorado, they are a small part of the GA safety picture. I’d like to draw your attention to a much bigger problem: VFR into IMC. When comparing the two in terms of media play, collisions get much more attention but are far less common.

Midairs average between 7-10 annually. To be fair, you need to double the number of hull losses because it takes two to tangle but here’s the interesting part. Typically, the fatal accident ratio on midairs is about 50% because many occur just over the touchdown zone. It results in a really hard landing but nobody falls very far and there are often no injuries. That is NOT to minimize the severity of any particular accident, as we saw last week – just relating the stats.

In the 30 or so annual VFR into IMC accidents, usually 90% result in fatalities. Too often the pilot chooses not to get a weather brief or download, or gets it, and ignores the warnings. It doesn’t help that “VFR Not Recommended” is occasionally in error. The flight launches and before too long the pilot is getting squeezed between cloud and terra firma. Doesn’t take much imagination to figure out what happens next. The widow makers are terrain ( mountains), towers and, of course, spatial disorientation  – Flying in low visibility over mountainous terrain is just not smart and towers will show up anywhere.

ASF created an Accident Case Study based on this all-too-common scenario and a Pilot Safety Announcement with a fairly pithy message. But how would a VFR pilot know what his or her minimum altitude should be and how low could the clouds descend before deciding to throw in the towel? First question is, What part of cloud don’t you understand?

There are several ways of determining this but we came up with something called a Terrain Awareness Plan ( TAP). It starts with a sectional chart and the maximum elevation figure.

If  you’d like to go more high tech go to the Aviation weather Center’s HEMS Tool and download (It’s still experimental) as an option.

If you’ve got another way, we’d like to hear it. We don’t want more posthumous Darwin Award trophies  this year so spread the word to those who push VFR limits. It can be said with absolute certainty that not one of the pilots who crashed in weather last year thought an accident would happen to them.

Bruce Landsberg
Senior Safety Advisor, Air Safety Institute

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