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Into thin air

Performance factors to consider with density altitude

Density altitude is more than a phrase you learn to pass a checkride—it’s an insidious threat whose hazards can go overlooked even by experienced pilots.

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We’re taught the basics even if we don’t have to contend with very high density altitudes in our day-to-day flying. But what we’re typically taught can be a significantly limited view on the hazards of high density altitude flying.

Sometimes, the only performance factor we consider is how density altitude will affect our takeoff and landing. We’ll need more runway for both because the engine won’t make as much power, the wings won’t make as much lift, and our true airspeed will be higher. Takeoff is only one part of the go/no-go decision, although we often think of it as the deciding factor.

Just because you can take off doesn’t mean that a flight can be accomplished safely. Your climb performance, climb gradient, turn radius, true airspeed, and other performance factors are easy to forget if you fixate on takeoff and landing. If the airport is reporting 8,000-feet-plus density altitude, guess what? You’ll likely be cruising at a density altitude higher than 10,000 feet. What’s your service ceiling? Do you really want to fly at the altitude where your airplane can’t climb anymore? Probably not.

The cooler months are a good time to explore your airplane’s performance (and your skill limits), what you feel comfortable with, and what’s safe. As it gets warmer, take notes on how that performance and your comfort level changes with the seasons.

Unfortunately, not all pilots prepare sufficiently for the potential dangers of high density altitude before they’re dealing with it in real time. In the early evening of July 3, 2021, two pilots in a newly purchased Beechcraft Bonanza G36 departed Aspen, Colorado, for their home base on the East Coast. They planned to cross the Sawatch Mountains—with peaks topping 14,000 feet—after an initial climb out of Aspen.

Join the AOPA Air Safety Institute as we follow the Bonanza’s likely encounter with high density altitude—an inherent hazard in high terrain significantly degrading aircraft performance. Deceptively upsloping terrain would leave no escape for the flatland pilots facing the canyon trapping them.

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airsafetyinstitute.org/ACS/IntoThinAir


Alyssa J. Miller

Alicia Herron

ASI Aviation Writer
Aviation writer Alicia Herron joined the AOPA Air Safety Institute in 2018. She is a multiengine-rated commercial pilot with advanced ground and instrument flight instructor certificates. Alicia is based in Los Angeles and enjoys tailwheel flying best.

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