Vertical
wind is approximated using a simplified inversion of the aircraft equation of
motion (Kopp, 1985). ). An example is shown in Figure 1 for Flight
803 on
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. The technique is valid only for straight and level,
non-accelerating flight. The 36 min data
segment below includes several turns in which the vertical wind is erroneously inferred
to be negative. The positive peaks represent actual updraft penetrations. At
the nominal penetration speed of 100 m s-1, each minute (each interval along
the horizontal axis) represents 6 km of flight.