by Jonathan M. Stern
Turbulence occurs when air currents vary significantly over short distances. Figure 13.7 shows wind shear and turbulence.
Figure 13.7. Wind shear can be caused by changes in wind direction over small changes in altitude.
Airline passengers experience turbulence as a bumpy ride, although extreme turbulence can cause structural damage to aircraft. Some extreme cases of turbulence have led to multiple serious injuries of passengers on large airliners. Table 13.1 shows the various classifications of turbulence, corresponding Flight Simulator turbulence settings, and a description of each classification.
|TABLE 13.1 Classifications of Turbulence|
|Classification||Flight Simulator Setting||Reaction Inside Aircraft|
|Light||1-2||Turbulence that momentarily causes slight, erratic changes in altitude and/or attitude (pitch, roll, yaw).
Occupants may feel a slight strain against seat belts or shoulder straps. Unsecured objects may be displaced slightly. Food service may be conducted and little or no difficulty is encountered in walking.
|Moderate||3-5||Turbulence that is similar to Light Turbulence but of greater intensity. Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times. It usually causes variations in indicated airspeed.
Occupants feel definite strains against seat belts or shoulder straps. Unsecured objects are dislodged. Food service and walking are difficult.
|Severe||6-7||Turbulence that causes large, abrupt changes in altitude and/or attitude. It usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control.
Occupants are forced violently against seat belts or shoulder straps. Unsecured objects are tossed about. Food service and walking are impossible.
|Extreme||8||Turbulence in which the aircraft is violently tossed about and is practically impossible to control. It may cause structural damage.|