Headwind and tailwind

Key takeaways

Headwind and tailwind belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Headwind and tailwind to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Headwind and tailwind from memory before moving on to harder problems.

Reference excerpt

A headwind is a wind that blows against the direction of travel of an object, while a tailwind blows in the direction of travel. A headwind decreases the object's speed and increases the time required to reach its destination, while a tailwind has the opposite effect. The terms are also used metaphorically in business and elsewhere about circumstances where progress is made harder (headwind) or easier (tailwind).

Travel

In aeronautics, a headwind is favorable in takeoffs and landings because an airfoil moving into a headwind is capable of generating greater lift than the same airfoil moving through tranquil air, or with a tailwind, at equal ground speed. As a result, aviators and air traffic controllers commonly choose to take off or land in the direction of a runway that will provide a headwind. Aircraft carriers usually turn into the wind during takeoffs and landings, and may increase their own speed. While on take-off and landing, headwinds are good because they allow the aircraft to use a shorter runway, in flight, however, headwinds are bad because they reduce the ground speed of the aircraft, which requires more fuel to get to the destination. Conversely, tailwinds are bad on take-off and landing, but are good in flight. In sailing, a headwind may make forward movement difficult, and necessitate tacking into the wind. In motor vehicles, wind can affect fuel consumption and top speed but is usually ignored by the driver who chooses the speed from speed limits and road conditions. In cycling, headwind is felt strongly by cyclists. It decreases the speed and increases the advantage of drafting, i.e. riding closely together in groups. This can affect tactics in road bicycle racing. The comedian Jacob Haugaard made a pointedly absurd campaign promise of more tailwind on bicycle paths when he successfully ran as an independent in the 1994 Danish parliamentary election. Cycling in Denmark is very popular.

Tailwinds and headwinds are commonly measured in relation to the speed of vehicles — commonly air and watercraft — as well as in running events — particularly sprints up to 200 metres where athletes run in the same or mostly same direction and wind assistance from a tailwind above two metre per second is not allowed in records. This limit also applies to long jump and triple jump.

Aeronautics calculations Pilots calculate the headwind or tailwind component and the crosswind component of local wind before takeoff. The direction of wind at a runway is measured using a windsock and the speed by an anemometer, often mounted on the same post. Headwind and tailwind are opposite interpretations of the wind component which is parallel to the direction of travel, while crosswind represents the perpendicular component. Determining the ground speed of an aircraft requires the calculation of the head or tailwind. Assume:

A = Angle of the wind origin from the direction of travel {\displaystyle A={\text{Angle of the wind origin from the direction of travel}}}

W S = The measured total wind speed {\displaystyle WS={\text{The measured total wind speed}}}

C W = Crosswind {\displaystyle CW={\text{Crosswind}}}

T W = Tailwind {\displaystyle TW={\text{Tailwind}}}

H W = Headwind {\displaystyle HW={\text{Headwind}}}

Then

C W = sin ⁡ ( A ) ⋅ W S {\displaystyle CW=\sin(A)\cdot WS}

H W = cos ⁡ ( A ) ⋅ W S {\displaystyle HW=\cos(A)\cdot WS}

For example, if the wind is at 09015 that means the wind is currently from heading 090 degrees with a speed of 15 knots and the aircraft is taking off from runway 24; having heading of 240. The pilot prefers the runway side with less than 90 difference from wind direction, in this case Runway 06; heading 060. Here, A = 30 ∘ {\displaystyle A=30^{\circ }} .

Crosswind = sin ⁡ [ 30 ∘ ] ⋅ 15 k n o t s ≈ 7.5 k n o t s {\displaystyle {\text{Crosswind}}=\sin[30^{\circ }]\cdot 15{\mathsf {knots}}\approx 7.5{\mathsf {knots}}}

Headwind = cos ⁡ [ 30 ∘ ] ⋅ 15 k n o t s ≈ 13 k n o t s {\displaystyle {\text{Headwind}}=\cos[30^{\circ }]\cdot 15{\mathsf {knots}}\approx 13{\mathsf {knots}}}

The aircraft is said to have 7.5 knots of crosswind and 13 knots of headwind on runway 06, or 13 knots of tailwind on runway 24. Aircraft usually have maximum tailwind and crosswind components which they cannot exceed. If the wind is at eighty degrees or above it is said to be full-cross. If the wind exceeds 100 degrees it is common practice to take off and land from the opposite end of the runway, it has a heading of 060 in the above-mentioned example.

See also Crosswind Air navigation Thrust Wind assistance Windsock

References

Illustrations

Worked examples

Example 1 — a first encounter with Headwind and tailwind

Start with the simplest possible case. Write down what Headwind and tailwind claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Headwind and tailwind before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Headwind and tailwind ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Headwind and tailwind

In research: Headwind and tailwind appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Headwind and tailwind in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Headwind and tailwind is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aerodynamics, so understanding it makes those chapters shorter.
In everyday life: Look for Headwind and tailwind outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Headwind and tailwind in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Headwind and tailwind means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Headwind and tailwind out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Headwind and tailwind in simple terms?

A headwind is a wind that blows against the direction of travel of an object, while a tailwind blows in the direction of travel. A headwind decreases the object's speed and increases the time required to reach its destination, while a tailwind has the opposite effect.

Why does Headwind and tailwind matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Headwind and tailwind?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Headwind and tailwind.