A Guide to Understanding Wind

Hello! Do you know how the wind works? This Guide will provide some good informations about it, since what is a wind, into wind gust informations. Also, this guide can be useful for pilots and Air Trafic Controllers. Have a good read!

What is Wind?

Wind is defined as moving air caused by a pressure difference between two regions, due to temperature variations.

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Source: https://www.faa.gov

Whenever there is a pressure difference between two points, the air will move from the point of greatest pressure to the point of least pressure in the horizontal direction. This phenomenon is called wind.

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Source: https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_00-6B.pdf

At higher levels, wind moves from Ecuador towards the poles. At lower levels, the wind circulation may be clockwise or counterclockwise, depending on the forces of Coriolis and the latitude at which the mass of air is located.

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Satellite Image

Wind Speed

Wind speed is the distance traveled in the unit of time; expressed in knots (KT), from 01 to 01 KT.

The ideal wind for landing and takeoff is always the opposite wind (bow wind). Never the tail wind.

Practical Example

In the example of this landing strip, considering that it is aligned with the rose of the winds, the ideal wind for operation would be a wind with the direction of 180 degrees and up to 10kt maximum.

Bow and Tail Wind

Bow Wind

The bow wind is best suited for landing and take-off operations, as it allows for an anticipated lift gain when compared to the tail wind.

Operation against the wind generates some of the required lift, resulting in a lower ground speed and less runway clearance. The headwind can also provide a higher climbing ratio.

Landing against the wind may also provide an operation where it is necessary to use less track distance and slower speed upon reaching the touch zone.

When the wind changes direction, air traffic control bodies often alter landing and takeoff operations using another headland. Up to 5kt, the wind would be considered harmless for landing and takeoff operations and does not require a headland change.

Tail wind

A takeoff with tailwind requires more runway and landing distance and higher speeds to generate sufficient lift for the flight. The climb rate can also be affected by the tailwind.

Practical Example

In the example of this landing strip, considering that it is aligned with the rose of the winds, the ideal wind for operation would be a wind with the direction of 180 degrees and up to 10kt maximum.

Landing with tailwind can cause the aircraft to touch the lane at a higher speed.

NOTE: Variable-direction wind and tail predominance, with an intensity of 10 knots or greater, may boost the excess speed during aircraft landing. In this situation, the crew must be prepared to properly assess available speed and lane length information for a safe landing.

Cross Wind

A potentially dangerous situation for landing and take-off operations is when the operation takes place under the effect of the so-called crosswind.

This phenomenon occurs when the wind is in the direction direction to the side of the aircraft.

The crosswind can change the expected course of the aircraft.
Oh god, it looks so hard, you may thinking. Calm! I’m going to practice now.

image
Source: https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_00-6B.pdf

NOTE: In the case of small aircraft, the pilot’s ability to operate with crosswind will vary according to the area he has on the aircraft.

During the takeoff run, the influence of the crosswind can cause a small aircraft to drift to the right or left side of the landing runway.

NOTE: When there is a large variation in the intensity of the wind at the time of landing, to the extent that it exceeds the limit set by the aircraft manufacturer, it increases the probability of an inadvertent departure of the aircraft from the runway. For operation at aerodromes that do not have precise direction and wind intensity information, due to absence of a meteorological station or ATS organ, the pilot must be aware of the indications of the bird, to verify if there is possibility of facing a component of tail wind or through.

Wind gusts

What is that? It is when the average wind speed is exceeded by 10 or more knots for at least 20 seconds, it is already considered a gust of wind.

This information is disclosed using the letter G (gusts), followed by the value of the gust, immediately after the average wind speed.

Practical Example:

METAR:

METAR SBMG 281900Z 04010 G 20KT 360V070 9999 FEW010 BKN015 BKN020 22/21 Q1010 =

See the image above, this is an aircraft taking off and passes through a track with gusting winds. At this stage, it undergoes a sharp increase in lift, propelling it up quickly. When the aircraft leaves the track, in turn, the lift decreases.

As a consequence of the different changes of wind intensity and direction in the vertical wind profile, the characteristics necessary to generate gradients with severe wind shear are created.

Burst winds may cause lift loss and change in aircraft trajectory.

Generally, wind gusts occur up to 3,000 meters above the ground. Above this level, turbulence becomes the most worrying phenomenon.

NOTE: At high levels, the existence of cirrus or cirrocumulus clouds may indicate occurrence of strong winds at altitude. To minimize possible bumps, it is advisable to slow down the cruise.

In the case of operations with small aircraft, gusts of wind may present danger during landing if the blast occurs laterally. In this case, the influence of a lateral gust of wind during the landing may cause a loss of heading (right or left bow), which may result in the aircraft leaving the runway after touching the ground.

In situations like this, it is necessary for the pilot to be attentive to correct the course of the aircraft and to avoid the lateral exit of the runway or overrun (exceedance of the limits of the runway of takeoff and takeoff).

NOTE: If the pilot realizes that he will not be able to correct the course of the aircraft, due to the influence of the gust of wind, he can make the decision to carry out a rush procedure.

Gusts of wind also pose a danger to small aircraft that are parked in the airfield yard. In the event of sudden changes in wind direction and speed, these aircraft may suffer structural damage if not properly secured.

In the flight planning phase, the occurrence of wind gusts at the departure aerodrome, along the route and at the destination aerodrome can be identified through the consultation of meteorological bulletins.

Thanks for reading!

This is my first article here and I hope I have contributed and helped you! I used ANAC (National Civil Aviation Agency) and Federal Aviation Administration articles as a source.

36 Likes

Good overview of winds. You’ve put a lot of research and thought into this.

Might I suggest also adding an additional section on wind shear: a suddenly change in the direction and/or speed of the wind. You’ve touched upon it in gusts, but it could be explained in a little more detail.

Also - I’m just curious - a headwind is called a bow wind in other countries? That’s a new term for me! Didn’t know that before.

4 Likes

Amazing work! Funny that the first image is the runway I just slammed on due to winds less than 5 mins ago at JFK… 😳

6 Likes

Great tutorial about winds! Very detailed!

Muito bom!

4 Likes

Great information!

However, you’ve copied the vast majority (~95%) of the text in this topic from this website, word for word.

I do see at the bottom you cite this as a source-

however, copying full sentences and paragraphs word for word from a website and pasting them into a topic, even if you do cite a source, isn’t the best thing to do.

Again, this is good information about wind, but it might be better if you can find a way to put this in your own words as opposed to copy pasting from websites. I want to emphasize I do understand your intent of contributing to the community, which is good, I am just trying to give you some perspective.

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I don’t know this, thanks! Now I know a think!!

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Hello, Yatch.

Thank you! This article is from ANAC, which I quoted. Thank you for the Feedback, as well! My intention was to get the informations and and put it together in one article, witch would be here at the community.

It probably wouldn’t be as read if I just posted a link to the site. So, thinking about it, I did what I did! But I will follow your feedback next time!

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Thank you! Yesss, I took it today! It was 32 of Gust!

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This is true, I agree that less people would feel inclined to visit the website if it was just a link, it does make sense why you would then post the information from the website.

However, this is why I suggest you still create a topic like this one, just find a way to give the information in your own words. This is 100% more acceptable and you’ll learn more about the topic yourself by reading, understanding, and explaining in your own words the information which you’re contributing to the community.

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Well done mate. 👏🏻👏🏻👏🏻

This is useful and great information about wind.

4 Likes

Thank you, @Sphinx!

3 Likes

Did anyone else not know this much about wind? This is honestly amazing, great job!

2 Likes

Great Information About The Winds! I Know More About It Now :)))

great. Love it. Good Job