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posted by Fnord666 on Wednesday June 21 2017, @06:53PM   Printer-friendly
from the commerce-collides-with-science dept.

The Associated Press reports via KTAR-FM in Glendale, Arizona

At Phoenix Sky Harbor International Airport, American Airlines regional jets sit on the tarmac as American Airlines says seven regional flights have been delayed and 43 have been canceled because of a heat wave as temperatures climb to near-record highs Tuesday, June 20, 2017, in Phoenix.

[...] It's the air density.

Hotter air gets thin, making it harder to take off and land safely, mostly for smaller jets. That's what has kept some planes grounded in Phoenix this week where temperatures have been pushing 120 degrees. Airplanes take off and stay aloft because of lift, the force from the movement of air underneath the plane's wings that push it upward.

"As air warms up, it expands and there's fewer molecules to be under your wing", said Lou McNally , professor of applied meteorology at Embry-Riddle Aeronautical University. With less lift, "you need more of everything. You need more thrust to take off. You need more distance (on the runway) to take off. You need more distance to land. You need more speed to land. It gets to a point for some aircraft that it gets just too much", he said.

High heat also means a plane climbs at a lower rate, said pilot Patrick Smith, author of the book "Cockpit Confidential".

To compensate, planes have to generate more thrust or power and have larger wings. Smaller jets that generate less thrust, like Bombardier's CRJ regional jets, which have a 118-degree limit at Phoenix's elevation, are more likely to be stuck in the heat.

At Dubai International Airport and other Gulf airports, which are used to hot weather, many flights--but not all--arrive at night and early morning to get around the heat problem. Gulf carriers also tend to operate longer flights using larger planes that aren't as limited by high heat.

[...] Airlines can take other steps when the temperature climbs too high. They can lighten the plane's load by selling fewer seats--a tactic American Airlines is using in the Phoenix heat wave--or reducing cargo. They can take off with less than a full tank of fuel and then stop somewhere cooler to refuel.


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  • (Score: 2) by kaszz on Wednesday June 21 2017, @10:41PM (1 child)

    by kaszz (4211) on Wednesday June 21 2017, @10:41PM (#529250) Journal

    temperatures have been pushing 120 degrees

    120 degree Celsius is a lot. Of course there is a problem. Even asphalt will become soft.

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  • (Score: 2) by its_gonna_be_yuge! on Thursday June 22 2017, @12:38AM

    by its_gonna_be_yuge! (6454) on Thursday June 22 2017, @12:38AM (#529296)

    Yeah, I read it as 120C the first time too. But then I remembered that SN is a US publication which uses some other archaic system called "Imperial". Why "Imperial" you ask? I think it has something to do with storm troopers who couldn't measure properly.