Science Says: Why some airplanes don't fly in high heat - WFMJ.com News weather sports for Youngstown-Warren Ohio

Science Says: Why some airplanes don't fly in high heat

Posted: Updated:
  • NationalMore>>

  • Grandmother shot, hostages held at supermarket; 1 woman dead

    Grandmother shot, hostages held at supermarket; 1 woman dead

    Sunday, July 22 2018 12:39 PM EDT2018-07-22 16:39:40 GMT
    (AP Photo/Damian Dovarganes). Los Angeles Police SWAT officers escort a group of people who were held for their safety by police across businesses surrounding a Trader Joe's supermarket, after a gunman held dozens of people hostage inside the store bef...(AP Photo/Damian Dovarganes). Los Angeles Police SWAT officers escort a group of people who were held for their safety by police across businesses surrounding a Trader Joe's supermarket, after a gunman held dozens of people hostage inside the store bef...
    Police say they're trying to determine what prompted a man to shoot his grandmother and then run into a busy Los Angeles supermarket and hold dozens of people hostage for hours.More >>
    Police say they're trying to determine what prompted a man to shoot his grandmother and then run into a busy Los Angeles supermarket and hold dozens of people hostage for hours.More >>
  • Judge, calm in court, takes hard line on splitting families

    Judge, calm in court, takes hard line on splitting families

    Sunday, July 22 2018 12:39 PM EDT2018-07-22 16:39:30 GMT
    U. S. District Judge Dana Sabraw went well beyond the American Civil Liberties Union's initial request to stop families from being separated at the border by imposing a deadline of Thursday to reunify more than...More >>
    U. S. District Judge Dana Sabraw went well beyond the American Civil Liberties Union's initial request to stop families from being separated at the border by imposing a deadline of Thursday to reunify more than 2,500 children with their families.More >>
  • Survivor recounts boat accident that killed 9 family members

    Survivor recounts boat accident that killed 9 family members

    Sunday, July 22 2018 12:34 PM EDT2018-07-22 16:34:48 GMT
    (AP Photo/Charlie Riedel). People pray outside Ride the Ducks, an amphibious tour operator involved in a boating accident on Table Rock Lake, Friday, July 20, 2018 in Branson, Mo.(AP Photo/Charlie Riedel). People pray outside Ride the Ducks, an amphibious tour operator involved in a boating accident on Table Rock Lake, Friday, July 20, 2018 in Branson, Mo.
    More than half of the 17 people killed when a tourist boat sank on a Branson lake were members of the same Indiana family, and they likely wouldn't have been on the ill-fated trip but for a ticket mix-up.More >>
    More than half of the 17 people killed when a tourist boat sank on a Branson lake were members of the same Indiana family, and they likely wouldn't have been on the ill-fated trip but for a ticket mix-up.More >>

By SETH BORENSTEIN and DAVID KOENIG
Associated Press

WASHINGTON (AP) - When it comes to getting airplanes off the ground in broiling weather, it's not the heat or the humidity. 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.

In Phoenix, temperatures around 118 are infrequent enough that airlines continue to use regional jets for shorter trips.

If a plane does try to take off beyond its temperature threshold, it may keep racing down the runway and not get up in time and have to abort. And if it tries to land when the air is too thin and hot, that's not good either because it can run out of runway, McNally said.

Before they fly, pilots consult a sheet that tells them about the temperature, elevation and even humidity - factors that go into something called density altitude, a key measurement of flight conditions.

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.

The density altitude is the main issue, but there also could be simple heat issues on internal components like seals that might become too soft or even melt at higher temperature, MIT aeronautics and astronautics professor R. John Hansman said.

Pilot Smith said electronics overheat, brake temperatures run high and internal machinery gets overly hot and then toss in ground temperatures racing past 110 degrees "and things begin to break down."

___

Koenig reported from Dallas, Texas.

___

Follow Seth Borenstein on Twitter: @borenbears. His work can be found here. Follow David Koenig on Twitter: @airlinewriter. His work can be found here .

___

This Associated Press series was produced in partnership with the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.

Copyright 2017 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

  • More NewsMore>>

  • Youngstown: 3 women injured at bar shooting

    Youngstown: 3 women injured at bar shooting

    Sunday, July 22 2018 12:23 PM EDT2018-07-22 16:23:32 GMT

    A shooting in Youngstown early Sunday morning sent three people to the hospital. Officers were called to Afro Dogs on Gibson Street around 4 A-M for a shooting. The victims were all female and one may have lost eyesight in one eye. Two of the victims drove to Saint Elizabeth's in their own vehicles while the third was taken by ambulance. As of now, all victims are listed in stable condition. There is no word on any suspects.

    More >>

    A shooting in Youngstown early Sunday morning sent three people to the hospital. Officers were called to Afro Dogs on Gibson Street around 4 A-M for a shooting. The victims were all female and one may have lost eyesight in one eye. Two of the victims drove to Saint Elizabeth's in their own vehicles while the third was taken by ambulance. As of now, all victims are listed in stable condition. There is no word on any suspects.

    More >>
  • Waterfire Sharon kicks off first event with "Magical Moments"

    Waterfire Sharon kicks off first event with "Magical Moments"

    Sunday, July 22 2018 5:24 AM EDT2018-07-22 09:24:47 GMT
    The Shenango River glowed for the first of the three Waterfire Sharon events in downtown Sharon as dozens of braziers were lit by people in boats carrying torches. The lighting ceremony for "Magical Moments" Saturday night took place on the State Street bridge just after 9 p.m. Some travel back to the Shenango Valley for the event each year. "To me it's spiritual and I love the smell of the fires burning, the cedar, I just thoroughly enjoy it," Kay Anderson said...More >>
    The Shenango River glowed for the first of the three Waterfire Sharon events in downtown Sharon as dozens of braziers were lit by people in boats carrying torches. The lighting ceremony for "Magical Moments" Saturday night took place on the State Street bridge just after 9 p.m. Some travel back to the Shenango Valley for the event each year. "To me it's spiritual and I love the smell of the fires burning, the cedar, I just thoroughly enjoy it," Kay Anderson said...More >>
  • Pets killed in Trumbull County fire

    Pets killed in Trumbull County fire

    Sunday, July 22 2018 5:03 AM EDT2018-07-22 09:03:48 GMT

    One dog and two cats are dead after a fire broke out at a Trumbull County home Saturday afternoon. Officials responded to a trailer fire in the 5000 block of Kinsman Road Saturday. The woman who lives there was not home at the time the flames broke out. Firefighters credit a passerby for alerting authorities of the blaze. Orangeville Fire Chief Larry Foltz tells 21 News the west end of the trailer saw the majority of the damage.  The cause remains under investigation.

    More >>

    One dog and two cats are dead after a fire broke out at a Trumbull County home Saturday afternoon. Officials responded to a trailer fire in the 5000 block of Kinsman Road Saturday. The woman who lives there was not home at the time the flames broke out. Firefighters credit a passerby for alerting authorities of the blaze. Orangeville Fire Chief Larry Foltz tells 21 News the west end of the trailer saw the majority of the damage.  The cause remains under investigation.

    More >>
Powered by Frankly
All content © Copyright 2000 - 2018 WFMJ. All Rights Reserved. For more information on this site, please read our Privacy Policy and Terms