Extreme heat can hinder flights

- John Cox Have a question about flying? Send it to

Q: Do airplanes have a hard time taking off in Arizona because of the hot weather?

— Chris Batten, Lilburn, Ga.

A: I would not say they have a hard time, but performanc­e is definitely limited by the heat. Hot air does not allow the wing to create as much lift (fewer air molecules); therefore, the weight must be reduced to maintain the required climb path. Very high temperatur­es such as Arizona, the Middle East or other desert environmen­ts require careful preflight planning.

Q: What kind of challenges do pilots face when taking off in the summertime from Albuquerqu­e because of altitude and temperatur­e?

— Rodger B., Albuquerqu­e

A: Airports such as Albuquerqu­e that are at high altitude have less air with which to produce lift. The atmospheri­c pressure decreases with altitude. When it is hot, air is less dense than when it is cold. Adding the two issues together means a high-altitude airport on a hot day has less dense air at lower pressure. Pilots calculate this to determine the density altitude.

Q: I had heard that over 117 degrees F, planes cannot fly. Is there a specific temperatur­e at which they can’t operate?

— Joyce Gioia

A: The airplane manufactur­er provides performanc­e charts for normal operations. These charts have upper limits and are generally around the figure you cite (near 120 F). If the temperatur­e exceeds the upper value on the chart, then it is not possible to perform the required calculatio­ns, and the airplane is not legally allowed to fly. An operator can purchase high-temperatur­e performanc­e charts, which enable more precise calculatio­ns that may allow the airplane to depart. There is a temperatur­e at which all performanc­e charts stop, making it impossible to fly.

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