How the MyFlaps Crosswind Calculator Works

When the wind isn’t perfectly aligned with an airport runway, some of its velocity acts across the runway-perpendicular to it-rather than along it. That’s the crosswind component.

MyFlaps calculates that component and compares it with the Maximum Demonstrated Crosswind Component for the selected aircraft.

The calculation is deliberately simple.

1. Start with the runway

Every runway has a direction.

Suppose you’re landing on Runway 09. Its heading is approximately 090°.

For the MyFlaps calculation, the important thing is the angle between the runway heading and the direction the wind is coming from.

Enter the ICAO airport code and MyFlaps looks up the airport’s available runway ends. When a new airport is loaded, the calculator initially selects the runway end whose heading is most closely aligned with the current wind. You can then select a different runway manually.

The runway selection is not changed when you refresh the weather for the same airport.

2. Look at the wind

Suppose the reported wind is:

060° at 20 kt

Runway 09 has a heading of 090°, so the wind is coming from 30° away from the runway heading.

Only the component of that wind acting perpendicular to the runway contributes to the crosswind.

3. Break the wind into components

The easiest way to picture the calculation is as a vector triangle:

The crosswind component is the simple sine component of the wind:

$$V_\text{crosswind} = V_\text{wind} \left|\sin(\theta)\right|$$

where:

• $V_\text{wind}$ is the wind speed
• $\theta$ is the angle between the wind direction and runway heading
• the absolute value means we care about the magnitude of the crosswind, not whether it is from the left or right

For our example:

$$20 \times \sin(30^\circ) = 10\text{ kt}$$

So the crosswind component is 10 kt.

That’s all there is to the basic calculation.

What about the headwind?

The same wind can also be divided into a component along the runway.

That component is the headwind or tailwind component:

$$V_\text{along} = V_\text{wind}\cos(\theta)$$

In our example:

$$20 \times \cos(30^\circ) \approx 17.3\text{ kt}$$

So the wind consists of:

• 10 kt across the runway
• 17.3 kt along the runway

The two components together describe the original wind vector.

4. Compare the result with the aircraft

Different aircraft have different published or demonstrated crosswind figures.

For example, suppose the selected aircraft has a Maximum Demonstrated Crosswind Component of 15 kt.

MyFlaps might then show:

Crosswind component: 10 kt
Maximum demonstrated: 15 kt
Below demonstrated crosswind

The important word here is demonstrated.

A Maximum Demonstrated Crosswind Component is not necessarily a hard operating limitation. It describes the crosswind component demonstrated during the relevant aircraft testing. The applicable aircraft flight manual, operating limitations and procedures remain authoritative.

So MyFlaps does not interpret 15 kt as a magical boundary at which an aircraft suddenly becomes incapable of landing.

Instead, it tells you that the calculated crosswind is below or above the aircraft’s demonstrated value.

5. What about gusts?

Wind is often reported as a steady speed with a higher gust speed.

For example:

12 kt, gusting 20 kt

The gust increment is:

$$20 - 12 = 8\text{ kt}$$

A commonly used approach-speed technique in gusty conditions is to add one-half of the gust factor to the normal approach speed.

That gives:

$$\frac{8}{2}=4\text{ kt}$$

So if the normal reference approach speed were 61 kt, the resulting speed after the half-gust correction would be:

61 + 4 = 65 kt

MyFlaps treats this as a gust correction, rather than pretending that the aircraft’s published Vref itself has changed.

The aircraft’s own flight manual or operating procedures always take precedence.

Where does the weather come from?

You can enter the wind manually, or enter an ICAO airport code and let MyFlaps retrieve the current weather from CheckWX.

The weather report can provide:

• wind direction
• steady wind speed
• gust speed

When an airport is loaded, MyFlaps also identifies the airport and its available runway ends. The calculator uses that runway data to populate the runway selector and initially chooses the runway whose heading is most closely aligned with the current wind.

If you refresh the weather for the same airport, the current runway selection is preserved. Loading a different airport starts a new runway selection for that airport.

You can still edit the wind values manually. Changes to wind direction, wind speed, gusts, runway, or aircraft update the calculation immediately.

Where does the aircraft information come from?

The aircraft database contains the Maximum Demonstrated Crosswind Component for individual aircraft and variants where we have a suitable source.

We aim to use authoritative aircraft documentation such as:

• Pilot’s Operating Handbooks (POHs)
• Aircraft Flight Manuals (AFMs)
• manufacturer documentation
• other appropriate primary sources

We also try to preserve the distinction between a maximum demonstrated crosswind component, an operating limitation, and other published guidance. They aren’t necessarily the same thing.

If a value can’t be established reliably, we’d rather leave it out than invent one.

Try the calculator

The easiest way to explore the relationship is to change the wind, runway, and aircraft yourself.

Open the MyFlaps Crosswind Calculator →

A simple calculation, deliberately

There isn’t an aerodynamic simulation hiding behind the result.

The crosswind calculation is just trigonometry.

The useful part is combining that simple piece of physics with aircraft-specific information so that you can quickly see what the wind is doing relative to the runway and the aircraft you’re flying.

That’s intentional.

MyFlaps isn’t trying to replace the aircraft’s flight manual or turn a simple calculation into something mysterious. It’s trying to make the underlying relationship visible and understandable.

What the result does — and doesn’t — tell you

The MyFlaps crosswind calculation can tell you:

• the crosswind component of the reported wind
• the component along the runway
• the selected aircraft’s Maximum Demonstrated Crosswind Component, when available
• whether the calculated crosswind is above or below that demonstrated value
• the size of a half-gust correction when gust information is available

It does not determine whether a particular real-world landing is safe.

Real aircraft operations depend on many factors, including aircraft configuration, weight, runway condition, pilot technique, aircraft-specific procedures, weather and operational limitations.

For real-world flying, always use the applicable aircraft documentation and procedures.

MyFlaps is a flight-simulation and educational tool.