text: Chapter 6
  LOAD DRIFT UNDER PARACHUTE
  6-32. To calculate the amount of drift experienced by a load under a parachute, use the D=KAV formula
  (Figure 6-4). Always round up to the next whole number.
  Figure 6-4. Example application of D=KAV formula.
  WIND
  6-33. Measuring wind on the drop zone entails measuring both surface wind and mean effective wind.
  Use an authorized wind-measuring device to measure surface (ground) wind speed, especially for
  personnel and heavy equipment operations.
  6-34. Mean effective wind (MEW) refers to the average wind from ground level to drop altitude.
  Measure the magnetic azimuth to the balloon and note the reciprocal heading. This gives you the MEW
  direction to report. Use the pilot balloon (PIBAL) to measure MEW. PIBAL circumferences include—
  y 10 grams for day—57 inches.
  y 30 grams for day—75 inches.
  y 10 grams for night—74 inches.
  y 30 grams for night—94 inches.