Figure 5-1. PIREP Turbulence Reporting

CHAPTER FIVE

AVIATION WEATHER

Intensity

Aircraft Reaction

Reaction Inside Aircraft

Occupants may feel a slight

Turbulence that momentarily causes slight, erratic

strain against seat belts or

changes in altitude and/or attitude (pitch, roll, yaw).

shoulder straps. Unsecured

Report as Light Turbulence; 1

objects may be displaced

Light

slightly. Food service may be

Turbulence that causes slight, rapid, and somewhat

conducted and little or no

rhythmic bumpiness without appreciable changes in

difficulty is encountered in

altitude or attitude. Report as Light Chop.

walking.

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

Occupants feel definite strains

times. It usually causes variations in indicated

against seat belts or shoulder

airspeed. Report as Moderate Turbulence; 1

straps. Unsecured objects are

Moderate

dislodged. Food service and

Turbulence that is similar to Light Chop but of greater

walking are difficult.

intensity. It causes rapid bumps or jolts without

appreciable changes in aircraft altitude or attitude.

Report as Moderate Chop.

Occupants are forced

Turbulence that causes large, abrupt changes in

violently against seat belts or

altitude and/or attitude. It usually causes large

shoulder straps. Unsecured

variations in indicated airspeed. Aircraft may be

Severe

objects are tossed about. Food

momentarily out of control. Report as Severe

service and walking are

Turbulence; 1

impossible.

Turbulence in which the aircraft is violently tossed

about and is practically impossible to control. It may

Extreme

cause structural damage. Report as Extreme

Turbulence.

High level turbulence (normally above 15,000 feet MSL) not associated with cumuliform

cloudiness, including thunderstorms, should be reported as CAT (clear air turbulence) preceded by

the appropriate intensity, or light or moderate chop.

NOTE:

Reporting Term

Definition

Occasional

Less than 1/3 of the time

Intermittent

1/3 to 2/3 of the time

Continuous

More than 2/3 of the time

Figure 5-1 PIREP Turbulence Reporting

The different types of turbulence can be divided according to their causative factors: thermal,

mechanical, frontal, and large-scale wind shear.

Two or more of these causative factors often work together. Any of the four types of turbulence

may occur without the visual warning associated with clouds. Turbulence in the absence of or

outside of clouds is referred to as clear air turbulence (CAT).

5-4

Weather Hazards of Turbulence, Icing, Ceilings, Visibility, and Ash Clouds