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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.
(Score: 2) by its_gonna_be_yuge! on Wednesday June 21 2017, @08:11PM (8 children)
I doubt this is BS - more like the airport/runways aren't designed for the heat.
But at least you quote the altitude and temperature in metric, so you've got that going for your argument. It *sounds* intelligent compared to people using the old clodhopper units. Good on you.
(Score: 2, Disagree) by t-3 on Wednesday June 21 2017, @09:43PM (6 children)
There's nothing wrong with using imperial units. SI is great for science and stuff, but imperial is vastly more intuitive. An inch is about the width of a finger, a foot is about length of a foot, a yard is about a pace, miles don't have much to recommend them over km, both are pretty arbitrary, 100F is pretty hot, 0 F is pretty cold, and the gradient is much better than C, grams are the same in either system, an ounce is a ziploc full of weed, and the pound, like fahrenheit, has a much better gradient for common everyday use than kg.
(Score: 2) by its_gonna_be_yuge! on Wednesday June 21 2017, @10:03PM (3 children)
Heh. Really? Vastly more intuitive? I've been in "Imperial" for half my life, metric for the rest. I can say that for me, Imperial is nothing but an awkward error-prone mess. 32/212 degF means nothing intuitive. Measuring in fractions of inches is nuts when you can do it in mm. But as long as you keep that "Imperial" in the US, I don't care. I buy most stuff from countries other than the US anyways. The US amazes me with it's self-inflicted wounds.
(Score: 2, Disagree) by t-3 on Wednesday June 21 2017, @11:37PM (1 child)
Freezing and boiling water are nothing you really need to measure in day to day life, so use SI for them. Outside of chemists, HVAC techs, and chefs, who regularly measures temps of water near boiling/freezing? Those don't need to be intuitive because they don't matter much for everyday life. 100F and 0F are both significant relative to everyday human experience, because they let you know it's dangerous to go outside unprepared, you can get heatstroke or frostbite. 100C means nothing to me except that I know it's the boiling point of water, I never encouter temps like that in day to day life, it's too low for cooking and and too high for environmental reference. 0C means nothing to me except that it's the freezing point of water, it's not particularly cold. Sure, the roads might get icy, but that usually doesn't happen until it's less than 0C for an extended period.
(Score: 2) by its_gonna_be_yuge! on Thursday June 22 2017, @12:34AM
Anybody in Canada. At least the freezing part. Anyways, there are a lot of people who need to know even by your own admission.
Only in the US. And quoting 0F as significant for frostbite is a bit of a stretch. Frostbite can happen over a huge range of temperatures, from 0C on down. It depends on way more factors than just outside temperature. 0F is only -18C - that's a common temperature in Calgary in the winter. Nothing special about it. and 100F isn't much above body temperature. Nothing special there.
Anyways, you live in your environment. And I'll live in the rest of the world ;-) .... I didn't down-mod you BTW - that was someone else.
(Score: 2) by AthanasiusKircher on Thursday June 22 2017, @03:35AM
Bah -- both of you are just attached to what you're used to. There are only two things metric is really superior at: (1) conversions, and (2) it's close to a globally accepted standard. The latter is a good reason to use metric. The former is actually not as common for ordinary people in ordinary life as one might think, but it's convenient.
Anyhow, when it comes to temperature measurements alone, reason (1) is irrelevant, since there are no old-fashioned weird non-decimal multiples or divisions of degrees. So the ONLY reason Celsius is superior is because of its widespread acceptance. I mean, making the degree scale between freezing and boiling of water be exactly 100 degrees is a reasonable idea, but it's not like the common person is calibrating thermometers using those numbers on a daily basis.
So it's all just what you're used to in the specific case of temperature. (Note I'm only talking about average Joe using temperature units alone. You start making up composite units and conversions rapidly become annoying, You haven't lived until you've done a fluids problem involving pressures measured in pounds per square inch, dimensions measured in a mixture of inches, feet, and yards, and an ideal gas law constant with cubic feet-atm per pound-mole degree Rankine!)
One can make up all sorts of justifications about why one systems seems more "natural," but when it comes to temperature it's 95% just what people are used to.
(Score: 0) by Anonymous Coward on Thursday June 22 2017, @02:07AM (1 child)
> miles don't have much to recommend them over km
Mile comes from the Roman mille for 1000. 1000 double paces = 5280 ft, so the Romans were probably shorter than we are now. Handy if you are keeping track of the progress of your marching army.
(Score: 4, Interesting) by KGIII on Thursday June 22 2017, @02:45AM
This is sort of related.
Speaking of the Romans, they marked out miles along their roads. Rome, as we all know, loved to make roads. I have read some research that suggests that the decline of the roads was a factor in the fall of Rome. That's unfortunate, really. The Romans were road building fools. They stopped maintaining them as their wealth decreased. The fall was really a slow declination. You can't really point to a specific date and claim it to be the fall of the empire, though you can point to an end date for their eastern empire - it is why we don't have Constantinople anymore. We don't have to ask the Turks, it's in the history books. Silly song.... But, I digress.
So, they built the roads with these neat sticks to survey. They didn't have the math to be able to plot a circumference. So, they take angles and they shoot the azimuth with the sticks that have a a simple cross and a plum bob. Using just those devices, and some simple math, they were able to tunnel in from both directions and be pretty damned accurate.
Anyhow, some of the original roads still exist in fairly close to original condition. You can drive down parts of the Appian Way. Well, they might have made it illegal, now. You could, however. I am too lazy to look to see if it is still allowed. Their construction was a very forward process and not entirely, at least in theory, dissimilar to the way we construct roads today.
No, they didn't pave them with asphalt and the had no steamrollers. But, they dug, leveled, put in ditches, did substrate, gravel, tamping, and paving with stone. They are based on the width of two horses abreast. Much of what is still considered normal is, curiously enough, kinda based on the width of two horses asses. That'd be our single vehicle lane width on many roads, or a close approximation. Were the width different, our vehicles might look different today.
Rome brought standardization of the highway. And, yeah, it's probably based on the width of two horse asses.
I don't have a point, really. I just figured I'd share that. It's kinda neat. Umm... I kinda like roads. The same standard(ish) is loosely coupled with the width of train tracks, or so I am told. I haven't looked to verify it. I kinda know about roads, not so much about trains.
"So long and thanks for all the fish."
(Score: 0) by Anonymous Coward on Thursday June 22 2017, @07:20AM
You need Kelvin, so you can use the ideal gas law. You could also use Rankine.