With sweltering heat and humidity plaguing much of the United States, pilots should be aware of the effects of high density altitude. It is critical to work through the performance charts for your aircraft before you take off-on a hot day, you might not have enough runway.For example: You plan to fly a Piper Tomahawk out of Clearview Airport in central Maryland. The airport elevation is 799 feet msl, and the runway length is 1,840 feet. On a 70-degree F day, your takeoff distance to clear a 50-foot obstacle would be 1,800 feet. But on a 100-degree day, you couldn't make it—it would take 2,350 feet to clear that 50-foot obstacle. Plus, climb performance would decrease from 625 fpm on a 70-degree day to 500 fpm on a 100-degree day.
"These are performance issues pilots have been taught from the beginning, but it is something we all need to be reminded of," said Woody Cahall, AOPA vice president of aviation services. "Do the math on these hot days. It's better to be safe than sorry." And remember, your aircraft might not perform as well as it did the day it left the factory. See the AOPA Air Safety Foundation online course, Mountain Flying .
August 4, 2006