# Weather temperature

I have an inquiry about the weather temperature

Does the high / low weather temperature affect while the plane is flying?

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When cruising the Outside Temperature is usually around -40 (Celsius and Fahrenheit) whether it’s summer or winter, above Dubai or Anchorage. So it really doesn’t vary much temperature wise at cruise

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Yes, temperature effects airplane performance both the engine itself and the aerodynamics involved.

What Is Density Altitude?

Density altitude is pressure altitude corrected for nonstandard temperature. As temperature and altitude increase, air density decreases. In a sense, it’s the altitude at which the airplane “feels” its flying.

How Will High Density Altitude Affect Flight?

On a hot and humid day, the aircraft will accelerate more slowly down the runway, will need to move faster to attain the same lift, and will climb more slowly. The less dense the air, the less lift, the more lackluster the climb, and the longer the distance needed for takeoff and landing. Fewer air molecules in a given volume of air also result in reduced propeller efficiency and therefore reduced net thrust. All of these factors can lead to an accident if the poor performance has not been anticipated.

One way of looking at it is that higher temperatures make the airplane fly the way it would at a higher altitude where the air is less dense. An airplane cannot climb to infinity, it has what is called a service ceiling [and an absolute ceiling] that the aircraft can no longer climb any higher. This also because of a decrease in air density, but for a different reason. Raising the temperature of the air also decreases this air density. You can use an Air Density Calculator or a Density Altitude Chart :

to determine how the aircraft will fly. It is especially important at airports with short runways or high actual altitudes [Denver, Colorado for example] where the aircraft already may need to be near maximum performance.

If the density altitude is 4,000ft than that means that airplane will fly like it was at 4,000ft at standard atmospheric temperature. Standard atmospheric temperature [at sea level] is 15 degrees Celsius or 59 degrees Fahrenheit. An airplane departing at a sea level airport, at 100F would feel like it is already flying at over 2600ft. An airplane departing at a 5,000ft airport would feel like it is already flying at over 8700ft. If clearing the trees at the end of the runway was already a concern at this particular airport it may not happen anymore.

Taken from this aviation StackExchange page. I started writing a reply but thought it’s much better to point you to someone who knows what they’re talking about, unlike me who isn’t an expert in this field by any means.

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Yes it does, test it out on solo, pick a plane, put temps down to -90 takeoff, test it again at the same weight and put the temp up to +70, you will see the ground speed increase.

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It does change, while flying PANC-KSLC there was a gradual 30c temperature change at cruising.

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@Maxim pretty much covered all the bases, but I’ll add that this isn’t just some textbook fact, you can actually see this in action especially as we come into the summertime. Down south especially really hot places, even better if they have some altitude on them, so like Phenix, or Vegas, you’ll see days where flights are cancelled because the planes can’t get airborne, or land safely in weather that hot. Two of three years ago there was a particularly bad heatwave in Phoenix, temperatures soared to 118, up as high as nearly 120 degrees Fahrenheit, that’s about 48 Celsius for the rest of the world. This brought the airport to a virtual standstill. At Phoenix’s altitude of 1,000 that meant planes were taking off at an effective altitude of ~5,000+ feet. This is also why a lot of these airports have long runways. For example Las Vegas has a 14,000 ft runway, because they have a double dose of relatively high altitude and hot climate. It’s not uncommon for them to bust the 100* F mark, which means at there altitude of 2,000 ft above sea level it can easily feel like nearly 6,000 feet above sea level. Airport altitude plays into this a lot, that’s why Denver has the longest commercial runway in the US, at a starting altitude of ~5,000 feet, on a hot day it could feel like approaching 10,000 feet of altitude.

True, I was flying over the summer and I noticed that the plane took up a lot more runway than in the winter, my home airport got a density altitude of 6053 ft yesterday when our elevation is 2800ft.

Yesterday I flew into Denver with a 165kt ground speed and a 140kt airspeed.

Aircraft perform better in colder temperatures.

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Way better, I almost overran at KDEN yesterday because of it.

Yes. If we lets say we have a higher temperature, like during the summer it will decrease the air density which will affect the way you fly. With lower air density, your aircraft will need as @Maxim said, more speed. (because of the lower density due to the high heat). This is because lift is determined/occurs when air molecules pass under and above the wing. So if there isn’t enough air molecules passing under the wing because of the lower air density, you will need to increase the speed in order to gain enough lift. So if you are not careful, your aircraft without sufficient speed will drop like a ton of bricks, aka stall wich is not fun.

Passing by airports during the summer, I noticed airplanes were at a higher angle attack upon landing. Almost like EGLC.

This is probably what altimeter means on ATIS.

Not really, upper atmosphere temperatures have a lot of variation to them, right now to use your example, it’s -64 over Anchorage, and a comparatively hot -31 over Dubai. While it’s true upper level temperatures are sum what more stable, they still fluctuate and in the part of the atmosphere that planes fly that is mostly determined by ground temperatures, but if you want your mind to be really blow, at about ~36,000 feet the temperature sum what stabilizes as you continue up till ~60,000 ft where it actually starts to climb again. Though this climbing is sum what false climbing because the energy of the individual particles is getting higher again, but there are so few at this point that it would probably still freeze you to death since the climbing goes from -60 C to -10 C, but it keeps going, when you hit the mesosphere at ~165,000 feet the temperature starts dropping again. This is because the effect I talked about above where the particles are getting hotter as you go up, but there’s also fewer of them to transfer this heat. But there’s one more swap to come, when you hit the thermosphere at ~280,000 feet the temperature goes up again and continues to do this till space, don’t get me wrong it’s still very cold up here but because at this point there’s so little air to filter the sun everything is incredibly hot, but the air still can’t transfer this heat to you very effectively because there’s so little of it, so if I were to place you in the thermosphere looking down on earth you would have the once in a lifetime feeling of simultaneously having your back fried to a crisp and your belly frozen, not to mention that your half an hour fall to the surface wouldn’t be too fun either…

That’s probably way more than you wanted to know, but there it is 😂

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I think Altimeter is designed for pilots to adjust their Altimeter according to their elevation at the current airport they are at. This is done so pilots and the airplane don’t receive incorrect altitude readings which is crucial especially when performing Cat II or Cat III ILS approaches.

So If for example we had an airport with an elevation of 1,650 feet (airport A), and then an airport with an elevation of -50 feet (Airport B ) (elevation from sea/ocean level). If a pilot takeoff from Airport A and doesn’t re-calibrate his/her altimeter to land at airport B (I think this is how it works) it could e disastrous…

But I also think that the Altimeter does have something to do with Air Pressure, and with air density as well because your Altimeter does also measure your rate of descent as well. (Which as we ave discussed does vary during different seasons do to changing weather).

It does, I have an altimeter watch and as a low pressure system was coming through the altitude started to go up.

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If your talking about the angle of attack no, but if it’s generally about the relationship between pressure altitude and temperature your spot on to an extent. Altitude is calculated one of two ways, either with barometric pressure, or by detecting how far down the ground is usually with radar of some kind. For this though the first one is what’s important. Barometric pressure is determined by all sorts of things mostly pressure systems and temperature. These pressure systems are at there core caused by changes in temperature. Hot air exerts more pressure, and cold air less, this is usually why temperature fronts are accompanied by a pressure change, and vise versa. The altimeter is set to the barometric pressure at the airport, so then the system can compensate for the fact that pressure is different pretty much everywhere. This can have some interesting knock on effects. One I can think of recently was a topic made by @Andre_S about how in Norway the pressure dropped so much due to a low pressure storm system that some planes particularly the -8 couldn’t fly at all because they couldn’t set there altimeter to a pressure that low. So to sum it all up, yes pressure is what altimeter is based on, and pressure and temperature are very much linked, so temperature does change altimeter setting, but it is not a direct measure of it…

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There is only one major difference with lower temperature, at least in IF: speed of sound increases with temperature. Therefore you cruise faster in hotter OAT.

Thanks for elucidating👍

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