Turbulence Intensity - Definition
All of us are aware of the typical definitions of turbulence as stated in various publications (AIM, FOM, etc). I.e.: Slight rhythmic bumps…walking difficult…..passengers thrown violently, etc, etc.
On that subject, a study was conducted about 10 years ago by “Digital Avionics Systems.” That study summarized as follows:
"...The goal of this research was to study how pilots assess turbulence intensity when no “out the window” cues are available (e.g., no clouds or contrails). In this experiment, we explored these subjective differences in turbulence assessments. Pilots provided their turbulence assessments while experiencing various “smooth”, “light”, and “moderate” turbulence intensities…”
Obviously - among other things - individual experience levels will account for at least some of the “Subjective” differences.
Around that same time (1999 – 2000), I read an aerospace publication / engineering document which contained a set of Turbulence definitions which related “Air Speed / Vertical Speed changes,” to specific Turbulence intensities.
The subject of that document seemed an effort to eliminate the "Subjectiveness", by applying a defined aircraft reaction, to a specifed turbulence intensity level (or visa-versa).
I can’t recall the name of the document, nor its publisher. It may have been a NASA (Dryden Flight Center) or Military (US Navy) document, but searching their respective public files, I have not been able to find it.
However, I vaguely recall that it applied to "Transport Aircraft," and that the document classified turbulence somewhere around the following values:- Light Chop = 5 – 14 knot changes in IAS
- Moderate Chop = 15-25 knot changes in IAS
- Light Turbulence = 5 – 14 knot changes in IAS, AND, 300 – 1199 FPM V/S
- Moderate Turbulence = 15-24 knot changes in IAS, AND, 1200 – 2400 FPM V/S
- Severe Turbulence = +25 knot changes in IAS, AND, 2500 - 2999 FPM V/S
- Extreme Turbulence = + 3000 FPM V/S...
Does anyone recall this document and its publisher?
Cheers