Flying in moving air
The nose can point one way while the airplane travels another. Change the wind, hold a heading or a course, and watch the two directions come apart.
Blue plus orange gives green. The wind arrow points where the moving air carries the airplane.
Set the conditions
The direction the wind comes from.
- Heading
- T
- Ground track
- T
- Groundspeed
- kt
- Drift from the nose
- left
Steady horizontal motion · constant true airspeed · uniform wind · all bearings relative to true north
A little time in the air
North up · nautical milesover the ground. Dashed blue shows displacement relative to the air mass; green shows the ground track.
The nose and the path
The nose points 000°, while the ground track is 345°. Holding a heading fixes the direction through the air; the wind still moves the air mass itself.
Move the elapsed-time control to see where the airplane ends up. The symbol points along its heading while its position follows the ground-velocity vector.
Switch between heading and course with the same conditions to see the correction. A direct headwind changes speed over the ground without changing direction.
Three velocities, one triangle
Velocity through the air plus the wind’s velocity gives velocity over the ground. Each has both a speed and a direction.
Vground = Vair + Vwind
Course mode: cancel the crosswind component
Distance in NM = groundspeed in kt × minutes / 60
The wind direction names where it comes from. A wind from the east moves the air toward the west, so its arrow points the opposite way from the reported bearing.
The model and its references
This is a constant-velocity illustration. It does not apply magnetic variation, gusts, climb, or aircraft operating limits. The symbol represents heading and position; it does not simulate a particular aircraft’s performance.
The FAA preset reproduces the worked example in the Pilot’s Handbook of Aeronautical Knowledge, chapter 16: course 090°, 120 kt true airspeed, and wind from 045° at 40 kt. Rounded results are heading 076° and groundspeed 88 kt.
NASA Glenn’s relative-velocity explanation describes the underlying relationship between the aircraft, the moving air, and the ground.