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UNIT 7

Weather Hazards (2)
SECTION 3. TURBULENCE

1. General

a. The effect of turbulence on aircraft ranges all the way from a few small bumps
to severe jolts which are capable of producing structural damage. Since turbulence is
associated with many different weather situations, it is helpful to have a knowledge of its
causes and how the irregular air movements act.

b. The atmosphere is considered turbulent when irregular eddies of air affect
aircraft so that a series of intermittent jolts or bumps are felt. A large range of eddy sizes
exist, but those causing turbulence are about the same size as the aircraft and usually occur
in an irregular sequence. The reaction of the aircraft to the turbulence varies not only with
the intensity of the eddies, but also with the aircraft characteristics such as flight speed, size
of the aircraft, altitude of the aircraft, and wing lift/weight relations. Turbulence can cause
quick unpredictable changes in the aircraft's altitude and attitude.

2. Intensity of Turbulence.
a. Classification of turbulence intensity is a difficult problem for pilots and

weathermen. The pilot's judgment of turbulence severity may be influenced by the length of

time his plane is exposed to turbulence, the amount of experience the pilot has, and the type

of aircraft he is flying.

b. In order to provide a standard for reporting and describing turbulence,

turbulence has been classified into four intensities; light, moderate, severe, and extreme,

according to its effect on the aircraft and its occupants. Turbul ence that causes a continuing
rapid series of bumps or jolts is called chop.