In ForeFlight, runway headings are described relative to Magnetic North, while wind directions are described relative to True North. When winds are nearly parallel to the runway at an airport with a significant magnetic variation, it might seem like ForeFlight is reporting a crosswind component from the wrong direction.
To verify that the crosswind component seen in ForeFlight is correct, follow these steps:
- With the airport displayed in ForeFlight on the Airports page, find the reported True wind direction and wind speed at the top of the Airport Summary or under Weather > METAR.
- Tap Info > Features.
- Find the Magnetic Variation in degrees East (E) or West (W).
- Use the Magnetic variation to calculate the Magnetic wind direction:
- If the variation is °East, subtract it from the True wind direction.
- If the variation is °West, add it to the True wind direction.
- Tap Runway.
- Select the correct runway from the list.
- Scroll down to the Heading section to find the Magnetic runway heading.
- Enter the wind speed, Magnetic wind direction, and Magnetic runway heading into an E6B or other flight computer to calculate the crosswind component.
- Compare your result to ForeFlight’s reported crosswind direction. The values should match.
Pilots at Monterey Regional (KMRY) might expect a right crosswind component listed for runway 28R with winds blowing from 290° at 4 knots. The lack of a crosswind arrow in the Runway entry might seem like an error.
However, you can determine that ForeFlight is correct, and there is no crosswind. Here’s how:
STEP 1. Locate KMRY’s reported True wind direction and speed (290° at 4 knots).
STEP 2. Find KMRY’s Magnetic Variation (15° E).
STEP 3. Calculate the Magnetic wind direction: (290° - 15° = 275°).
STEP 4. Find runway 28’s Magnetic heading (278°).
STEP 5. Enter the following into a flight computer to calculate the wind component.
- Wind speed = 4 knots
- Magnetic wind direction = 275°
- Magnetic runway heading = 278°
STEP 6. Evaluate the results:
ForeFlight subtracts KMRY’s magnetic variation (15°E) from the True wind direction (290°) to calculate a Magnetic wind direction of 275°. This wind blows virtually straight down runway 28 (oriented at 278°), and ForeFlight reports no crosswind. This should align with calculations made on a flight computer.