Vertical wind

Vertical wind is approximated using a simplified inversion of the aircraft equation of motion (Kopp, 1985). An example is shown in Figure 4. The most important component of this estimate is the rate of change of aircraft pressure altitude, which is approximated as a centered difference, one second either side of the second at which the computed value is stored. The most simplifying approximation in the equation of motion is substituting pitch (which is measured on the T-28) for angle-of-attack (which is not measured). This approximation leads to an improvement in estimated vertical wind over that obtained using solely the rate-of-change of aircraft pressure altitude as a proxy for vertical wind, but is not as accurate as would be a similar calculation with a measured angle-of-attack.

Figure 4. Vertical wind estimated from T-28 flight data during the entire flight on 29 June 2000. The estimate is valid only during straight-and-level flight, and yields artifact downdrafts during turns. The 30 m s-1 peak just after 234200 was observed during a pass through the main updraft.

Kopp, F. J., 1985: Deduction of vertical motion in the atmosphere from aircraft measurements. J. Atmos. Ocean Tech., 2, 684-688.