Wind Drift


  • For example, if a powerboat is crossing a river and the river is still, the boat could head directly to a point on the opposite shore and travel on a straight course to that point without drifting
  • That is, as the boat progresses forward with its own power, it must also move upstream at the same rate the river is moving it downstream
  • This is accomplished by angling the boat upstream sufficiently to counteract the downstream flow
  • Should the boat not be headed sufficiently upstream, it would drift with the current and run aground at some point downstream on the opposite bank [Figure 1]
  • As soon as an airplane becomes airborne, it is free of ground friction
  • Its path is then affected by the air mass in which it is flying; therefore, the airplane (like the boat) will not always track along the ground in the exact direction that it is headed

All procedures here are GENERALIZED for learning.
and/or current Standard Operating Procedures (SOPs)

Airplane Flying Handbook, Wind Drift
Figure: 1 Airplane Flying Handbook, Wind Drift

  • This would indicate that the air mass is moving side-ward in relation to the airplane. Since the airplane is flying within this moving body of air (wind), it moves or drifts with the air in the same direction and speed, just like the boat moved with the river current [Figure 1]
  • When flying straight and level and following a selected ground track, the preferred method of correcting for wind drift is to head the airplane (wind correction angle) sufficiently into the wind to cause the airplane to move forward into the wind at the same rate the wind is moving it sideways
  • Depending on the wind velocity, this may require a large wind correction angle or one of only a few degrees
  • When the drift has been neutralized, the airplane will follow the desired ground track
  • To understand the need for drift correction during flight, consider a flight with a wind velocity of 30 knots from the left and 90° to the direction the airplane is headed
  • After 1 hour, the body of air in which the airplane is flying will have moved 30 nautical miles (NM) to the right
  • Since the airplane is moving with this body of air, it too will have drifted 30 NM to the right
  • In relation to the air, the airplane moved forward, but in relation to the ground, it moved forward as well as 30 NM to the right
  • There are times when the pilot needs to correct for drift while in a turn [Figure 2]
  • Throughout the turn the wind will be acting on the airplane from constantly changing angles
  • The relative wind angle and speed govern the time it takes for the airplane to progress through any part of a turn
  • This is due to the constantly changing ground speed
  • When the airplane is headed into the wind, the ground speed is decreased; when headed downwind, the ground speed is increased
  • Through the crosswind portion of a turn, the airplane must be turned sufficiently into the wind to counteract drift
  • To follow a desired circular ground track, the wind correction angle must be varied in a timely manner because of the varying ground speed as the turn progresses
  • The faster the ground speed, the faster the wind correction angle must be established; the slower the ground speed, the slower the wind correction angle may be established

  • Airplane Flying Handbook, Effect of Wind During a Turn
    Figure 2: Airplane Flying Handbook, Effect of Wind During a Turn
  • The principles and techniques of varying the angle of bank to change the rate of turn and wind correction angle for controlling wind drift during a turn are the same for all ground track maneuvers involving changes in direction of flight
  • When there is no wind, it should be simple to fly along a ground track with an arc of exactly 180° and a constant radius because the flightpath and ground track would be identical
  • This can be demonstrated by approaching a road at a 90° angle and, when directly over the road, rolling into a medium-banked turn, then maintaining the same angle of bank throughout the 180° of turn [Figure 2]
  • To complete the turn, the roll-out should be started at a point where the wings will become level as the airplane again reaches the road at a 90° angle and will be directly over the road just as the turn is completed
  • The effects of wind during turns can be demonstrated after selecting a road, railroad, or other ground reference that forms a straight line parallel to the wind
  • Fly into the wind directly over and along the line and then make a turn with a constant medium angle of bank for 360° of turn [Figure 3]
  • A similar 360° turn may be started at a specific point over the reference line, with the airplane headed directly downwind
  • Airplane Flying Handbook, Effects of Wind During Turns
    Figure 3: Airplane Flying Handbook, Effects of Wind During Turns
  • In this demonstration, the effect of wind during the constant banked turn will drift the airplane to a point where the line is re-intercepted, but the 360° turn will be completed at a point downwind from the starting point
  • Another reference line which lies directly crosswind may be selected and the same procedure repeated, showing that if wind drift is not corrected the airplane will, at the completion of the 360° turn, be headed in the original direction but will have drifted away from the line a distance dependent on the amount of wind

Practical Test Standards/Airman Certification Standards: