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It's Too Hot For Some Planes To Fly In Phoenix (npr.org)
In Phoenix on Tuesday, temperatures were forecast to climb as high as 120 degrees Fahrenheit, causing more than 40 American Eagle regional flights out of Phoenix's international airport to be canceled. NPR reports: American Airlines said in a statement that the Bombardier CRJ aircraft used on some shorter routes have a maximum operating temperature of 118 degrees. For bigger jets, the threshold is higher. The carrier says that, for example, Airbus aircraft have a maximum operating temperature of 127 degrees and that for Boeing, it is 126 degrees. As USA Today reports: "Extreme heat affects a plane's ability to take off. Hot air is less dense than cold air, and the hotter the temperature, the more speed a plane needs to lift off. A runway might not be long enough to allow a plane to achieve the necessary extra speed." Bianca Hernandez, a meteorologist with the National Oceanic and Atmospheric Administration, tells NPR that Phoenix is seeing an unusually strong high-pressure system, which is causing the soaring temperatures.
This actually isn't all that uncommon around the world, at least to varying degrees.
Hot air, at high(er) altitudes is less dense, which will affect the performance of an aircraft to various degrees. The usual effect is that reduces the aircraft's MTOW (Maximum Take Off Weight). If it drops below a certain point, it's either uneconomical to fly the plane, or it can't carry enough fuel to do its job.
Many years ago, Air Canada used to fly to India using Airbus A340s. At certain times of year, it was hot enough in Delhi that they could not take off with sufficient fuel to do DEL->YYZ direct, and instead they would have to make a technical stop in Turkey to refuel the aircraft. This is also one of the reasons why most long-haul international flights fly in and out of Delhi at night. The air is cooler, giving the airliners better performance.
...si hoc legere nimium eruditionis habes...
Arizona overall isn't a hot state, it's just Phoenix which happens to reside in a valley. If you actually go south to Tucson, it's generally about 5 degrees cooler, and to the north lies Flagstaff, which this year had the longest duration ever for its popular snow skiing resort being open (from October til May.) It also snows much of the year at Four Peaks, which is about a 1 hour drive from Phoenix.
You may as well say that California is a hot state because of Death Valley, which is always hotter than Phoenix.
The article is sort of right. What matters more is density altitude, the effective density based on temperature and air pressure. But that's not to say other aspects of the plane are not rated for that temperature because they would then exceed some internal temperature based on temp rise above ambient.
I believe in global warming, got solar panels, hopefully a model 3 someday. The non-stop slashdot stories about global warming is going to cause the end of the world as we know it, is a bit much.
The problem is not global warming, or at least not the primary one. The problem is it is currently more profitable to lie and pretend it doesn't exist, is a scam from china, isn't our fault anyway, there is nothing we can do, etc, etc.
The problem is those lies, like so many others work remarkably well quite often, well that and the fact that people care about the near term. Sacrificing, well, anything, for the long term, or the planet, is, well, not particularly American. It is all rather sad.
If we had competent representation, we could pull off a plan to minimize it and to mitigate it, to one degree or another. We have a society that is increasingly embracing anti intellectualism. You can't get competent representation if your definitions are all skewed, if your society's heroes are the football stars and not engineers or the scientists.
How do we change society to first above all to embrace logic, reason, and truth, above all the mess we have now? We often get it right eventually, but is it really necessary to try all the obviously bad ideas first every time and for things like the environment, well, do we even have time not to act? The costs just go up..
Phoenix has only had three previous days with a temp of 120F or higher, all occurring in 1990 or later. Such temps were not recorded there any other time since 1890s.
I found a cool source:
https://www.pilotsofamerica.com/community/threads/max-operating-temperature-for-airplane.104126/
According to these guys, there is probably no physical limit that absolutely prevents the CRJ from operating safely above 118 degrees, given runways that are long enough for the gross weight. The problem is that pilots and airlines are not allowed to use the laws of physics, such as the ideal gas law, to calculate the required runway length to takeoff at a given weight and temperature. Instead, they are required to use the official performance data published by the OEM. The official performance data is printed in the FAA-approved Airplane Flight Manual as a series of graphs, and for airliners the same data may also be available in some computerized form. The graphs are only printed up to a certain temperature, so if the ambient temp. exceeds that limit, there is no way to calculate the required runway length.
For at least some planes, it may be possible to obtain officially sanctioned "expanded performance data," aka. charts that extend into higher temperatures, but it's often not economical to shell out extra fees to get this data.
And you're perpetuating a common falsehood, that's been thoroughly debunked.
It's a nice story, but it's not true. The origin of the scale comes from Ole Romer who set freezing of water at 7.5, and human body temperature at 23.5, and boiling point at 60. Fahrenheit didn't like this scale because of the fractions so he just bumped everything up by 0.5. Freezing at 8, body temperature at 24. Later on he multiplied everything by 4. Freezing now becomes 32, body temperature 96, boiling at 212.
But there's probably more to the story, since 1oF increase in temperature increases the volume of Mercury by 1 part in 10,000. Did this play into it? No one knows.
Interesting story. I highly recommend Veritasium's video on the subject:
https://www.youtube.com/watch?...
I'm up at 0315 for a training flight in a balloon this morning. Sunrise is at 0450. I intend to have landed by 0730, and this has little to do with the heatwave we're experiencing.
The reason balloons operate near sunrise and sunset is not specifically to do with the temperature, but actually to avoid thermals, which are generate by temperature differences (strictly, different heating rates of areas on the ground). Thermals that would be fairly pathetic for a glider pilot (which I used to be), say anything up to 200 ft/min up or down, would be enough to cause issues for balloons. Meaningful thermals (more than 200 ft/min up or down) would make the balloon very hard to control, since up and down control is the only way a balloon pilot can steer and uncommanded up and down movements (especially on landing!) mean you don't know where you're going to end up.
As far as temperature is concerned, the balloon flies a bit better in summer but can carry less weight. The balloon is less buoyant in hot air which is thinner as the parent(s) point out, so in general you can carry more weight in winter (or at lower altitudes - "pressure altitude" is still a relevant thing to look up). The big deal with temperature for me is actually that the fuel pressure drops a lot with falling temperature (liquid propane expands and contracts far more than water does). This means that in winter, less fuel is supplied each time I burn, meaning less heat output per burn. I have to burn more frequently to maintain level flight, or constant climb/descent rates.
I knew I needed to stop reading Slashdot and finish my PhD when I started to miss articles by Bennett Haselton.
The core value of metric is not just the decimal calculations, but that the units for different measures, such as weight and volume, fit together in an easily comprehensible way. No more medieval mess of fluid ounces, cups, pints and gallons.
I was in Phoenix when they closed the airport due to temperature. I think it was 1990. The problem was their printed charts for how much runway they needed for a certain temperature only went up to about 120F and it was over that, so legally (or insurance-wise) they couldn't fly.
The original measurement was that 0C was the freezing point of water at sea level. This has since been changed so that 0.01C is the triple point of water, exactly -- or more specifically, 273.16K . (The triple point of water is the temperature and pressure at which water can exist in all 3 states simultaneously, which is 273.16 K (0.01 C) at 0.611657 kPa (0.00603659 atm)).
This was chosen because the triple point is at an exact temperature AND pressure. If either the temperate or the pressure are changed then water cannot exist in all 3 states. There's no "at sea level" here, as that can be somewhat arbitrary, thus leading to a fluctuating 0C.
https://en.wikipedia.org/wiki/..., if you want to read more.
The vast majority of SI units are specified so that they can be measured in a lab -- the kilogram being an obvious exception to this, but that is something that should be resolved soon. The definitions of all of the SI units is actually fairly fascinating, and I recommend reading at least the Wikipedia article about them.
https://en.wikipedia.org/wiki/...
This lists the original measurements (such as the metre being 1/10,000,000 of the distance from the North Pole to the Equator (through Paris, for some reason)), and how the definition changed until the current definition was reached (a metre is the distance light travels through a vacuum in 1/299,792,458 seconds).
It gives reason to all of the measurements, and shows how they are all (mostly) interlinked, again with the obvious exception of the kilogram.
Incidentally, the inch, which is the basis for all imperial units of measuring, is 25.4mm exactly. So all measurements in the US are actually based on SI units. https://en.wikipedia.org/wiki/...
All weights are also based on SI units: https://en.wikipedia.org/wiki/...