Calculate ground speed and required heading using the wind triangle method
Aircraft's speed through the air
Speed of the wind
Direction wind is coming from (0-360°)
Path you want to fly over ground (0-360°)
Ground Speed
550.0
knots
Required Heading
90.0°
Direction to point aircraft
Wind Correction Angle
0.0°
No correction
Headwind Component
50.0 knots
Headwind
Crosswind: 0.0 knots
Ground speed is the actual speed of an aircraft relative to the ground below, while airspeed is the speed of the aircraft relative to the surrounding air. These two speeds differ when wind is present. A headwind reduces ground speed, while a tailwind increases it. For navigation and flight planning, ground speed determines how long it takes to reach a destination.
The relationship between airspeed, ground speed, and wind is visualized using the wind triangle (also called the velocity triangle), which is the foundation of dead reckoning navigation. The three vectors form a triangle: the airspeed vector points in the direction the aircraft is heading, the wind vector shows wind direction and speed, and the ground speed vector represents the resulting path and speed over the ground.
When flying in crosswinds, pilots must apply a wind correction angle (WCA) by heading slightly into the wind (called "crabbing") to maintain the desired course over the ground. The calculator uses the classic E6B flight computer formulas to solve the wind triangle and determine the required heading and resulting ground speed. This is essential for accurate navigation, fuel planning, and arrival time estimates.
Input your aircraft's true airspeed (TAS), not indicated airspeed. TAS accounts for altitude and temperature effects. For accurate navigation, convert IAS to TAS using an E6B computer, flight calculator app, or the aircraft's flight management system.
Input wind speed and direction. Wind direction is always reported as the direction the wind is coming FROM (not going to). For example, a "270° wind" means wind from the west (blowing east). Obtain current winds from ATIS, METAR, or weather briefings.
Enter the course (track) you want to fly over the ground. This is your intended path from departure to destination, typically measured on a chart as the true course between waypoints.
The calculator provides ground speed, required heading, wind correction angle, and headwind/crosswind components. Fly the required heading to track your desired course. Ground speed determines your ETA and fuel consumption.
A pilot plans to fly due west (270°) in a Cessna 172 with a true airspeed of 110 knots. The winds aloft forecast reports winds from the north (360°) at 20 knots. Calculate the required heading and ground speed.
Wind is blowing toward 180° (south)
Angle = (180° - 270°) = -90° relative to course
This is a pure crosswind from the right
sin(WCA) = (WS / TAS) × sin(wind_angle)
sin(WCA) = (20 / 110) × sin(-90°)
sin(WCA) = 0.1818 × (-1) = -0.1818
WCA = arcsin(-0.1818) = -10.5°
Heading = Course + WCA
Heading = 270° + (-10.5°)
Heading = 259.5°
GS = TAS × cos(WCA) + WS × cos(wind_angle)
GS = 110 × cos(-10.5°) + 20 × cos(-90°)
GS = 110 × 0.983 + 20 × 0
GS = 108.1 knots
To fly due west, the pilot must head 259.5° (about 10.5° south of west) to compensate for the north wind pushing the aircraft southward. The resulting ground speed is 108.1 knots. Key points:
Pro Tip: In-flight, continuously monitor GPS ground track. If drifting off course, adjust heading in small increments (2-5°) until tracking the desired course, then hold that heading.
Heading is the direction the aircraft's nose points, while course (or track) is the actual path over the ground. In no-wind conditions they're the same, but with crosswinds you must head into the wind to maintain your desired course.
Pure crosswind doesn't directly slow you down, but the wind correction angle means you're not pointing exactly where you want to go. You're flying slightly sideways through the air, so less of your airspeed contributes to forward progress over the ground.
Winds change with altitude and location. Pilots get winds aloft forecasts for different altitudes, calculate wind triangles for each flight segment, and continuously monitor GPS ground track to detect wind shifts and adjust heading accordingly.
The E6B is a circular slide rule used for flight planning calculations, including wind triangles, fuel consumption, and conversions. Modern pilots use electronic E6B apps, but the mechanical version is still taught and allowed on pilot exams.
Takeoff and landing performance depends on airspeed (wind over the wings), not ground speed. Taking off into a headwind means slower ground speed but safer operation — you need less runway. Crosswinds require special techniques to prevent drift.
Each aircraft has a demonstrated crosswind component (typically 15-20 knots for trainers, 30-40 for airliners). Exceeding this doesn't make the aircraft illegal, but it's beyond what was tested during certification. Pilot skill is critical.
Actually, it's usually the opposite — ground speed often exceeds airspeed due to tailwinds at altitude. The jet stream (100+ knot tailwinds) can boost ground speed significantly on eastbound flights, while westbound flights fight headwinds and are slower.
GPS provides real-time ground speed and track, making it easy to navigate. However, understanding wind triangles is essential for preflight planning (fuel, time estimates), interpreting GPS data, and handling GPS failures. Pilots must know both methods.
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