Light;
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.
Occasional – Less than 1/3 of the time.
Intermittent – 1/3 to 2/3.
Continuous – More than 2/3.
Moderate;
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.
or
Turbulence that is similar to Light Chop but of greater intensity. It causes rapid bumps or jolts without appreciable changes in aircraft altitude or attitude.
Occupants feel definite strains against seat belts or shoulder straps. Unsecured objects are dislodged. Food service and walking are difficult.
Severe;
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;
Turbulence in which the aircraft is violently tossed about and is practically impossible to control. It may cause structural damage.
The
Vb speed (turb pen.) is not usually any different from the Va speed for light a/c and is defined at 66'/sec of vertical gust.
In general, any time you are in moderate turbulence you should be not above the Va speed
adjusted for weight.
Note, even though it is expressed that you will not break the aircraft if you make full deflection at Va,
DO NOT go from one full deflection (eg. Full left rudder) to the other extreme.
