Aeronautical Information Manual (AIM), page 484

Index   483 -- Page 484 -- 485

AIM      CHG 2                                                                                                    3/15/07

                                                       TBL 7-1-7
                                            PIREP Element Code Chart

          PIREP ELEMENT              PIREP CODE                                CONTENTS
  1.   3-letter station identifier     XXX           Nearest weather reporting location to the reported phenomenon
  2.   Report type                   UA or UUA       Routine or Urgent PIREP
  3.   Location                         /OV          In relation to a VOR
  4.   Time                             /TM          Coordinated Universal Time
  5.   Altitude                          /FL         Essential for turbulence and icing reports
  6.   Type Aircraft                     /TP         Essential for turbulence and icing reports
  7.   Sky cover                        /SK          Cloud height and coverage (sky clear, few, scattered, broken, or
  8.   Weather                           /WX         Flight visibility, precipitation, restrictions to visibility, etc.
  9.   Temperature                        /TA        Degrees Celsius
 10.   Wind                              /WV         Direction in degrees magnetic north and speed in knots
 11.   Turbulence                         /TB        See AIM paragraph 7-1-22
 12.   Icing                               /IC       See AIM paragraph 7-1-20
 13.   Remarks                           /RM         For reporting elements not included or to clarify previously
                                                     reported items

7-1-20. PIREPs Relating to Airframe Icing                          1. Trace. Ice becomes perceptible. Rate of
                                                               accumulation slightly greater than sublimation.
   a. The effects of ice on aircraft are cumulative-           Deicing/anti-icing equipment is not utilized unless
thrust is reduced, drag increases, lift lessens, and           encountered for an extended period of time (over
weight increases. The results are an increase in stall         1 hour).
speed and a deterioration of aircraft performance. In
extreme cases, 2 to 3 inches of ice can form on the                2. Light. The rate of accumulation may create
leading edge of the airfoil in less than 5 minutes. It         a problem if flight is prolonged in this environment
takes but 1/2 inch of ice to reduce the lifting power of       (over 1 hour). Occasional use of deicing/anti-icing
some aircraft by 50 percent and increases the                  equipment removes/prevents accumulation. It does
frictional drag by an equal percentage.                        not present a problem if the deicing/anti-icing
                                                               equipment is used.
   b. A pilot can expect icing when flying in visible               3. Moderate. The rate of accumulation is such
precipitation, such as rain or cloud droplets, and the         that even short encounters become potentially
temperature is between +02 and -10 degrees Celsius.            hazardous and use of deicing/anti-icing equipment or
When icing is detected, a pilot should do one of two           flight diversion is necessary.
things, particularly if the aircraft is not equipped with
deicing equipment; get out of the area of                           4. Severe. The rate of accumulation is such that
precipitation; or go to an altitude where the                  ice protection systems fail to remove the accumula-
temperature is above freezing. This "warmer"                   tion of ice, or ice accumulates in locations not
altitude may not always be a lower altitude. Proper            normally prone to icing, such as areas aft of protected
preflight action includes obtaining information on the         surfaces and any other areas identified by the
freezing level and the above freezing levels in                manufacturer. Immediate exit from the condition is
precipitation areas. Report icing to ATC, and if               necessary.
operating IFR, request new routing or altitude if icing        NOTE-
will be a hazard. Be sure to give the type of aircraft to      Severe icing is aircraft dependent, as are the other
ATC when reporting icing. The following describes              categories of icing intensity. Severe icing may occur at any
how to report icing conditions.                                accumulation rate.

7-1-40                                                                                                      Meteorology

Page 484 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   483 -- Page 484 -- 485