Pilot Reports


  • A Pilot Report (PIREP) is a report of meteorological phenomena encountered by the pilot, in flight
  • These reports serve as warnings to other pilots and give Air Traffic Control (ATC) knowledge of potential hazards in order to keep pilots clear
  • All pilots should give reports if:
    • In flight when requested
    • When unusual or unforecast weather conditions are encountered
    • When weather conditions on an IFR approach differ from the latest observation
    • When a missed approach is executed due to weather
    • When a wind shear is encountered on departure or arrival
  • Different types of reports include:

Issuance & Validity:

  • Issued when/as reports are received
  • Valid for current conditions and contain no forecasted data

Pilot Reports

  • FAA air traffic facilities are required to solicit PIREPs when the following conditions are reported or forecast:
    • Ceilings at or below 5,000'
    • Visibility at or below 5 miles (surface or aloft)
    • Thunderstorms and related phenomena
    • Icing of light degree or greater
    • Turbulence of moderate degree or greater
    • Wind shear and reported or forecast volcanic ash clouds
  • Pilots are urged to cooperate and promptly volunteer reports of these conditions and other atmospheric data such as:
    • Cloud bases, tops and layers
    • Flight visibility
    • Precipitation
    • Visibility restrictions such as haze, smoke and dust
    • Wind at altitude
    • Temperature aloft
  • PIREPs should be given to the ground facility with which communications are established; i.e., EFAS, AFSS/FSS, ARTCC, or terminal ATC
    • One of the primary duties of EFAS facilities, radio call "FLIGHT WATCH," is to serve as a collection point for the exchange of PIREPs with en route aircraft
  • If pilots are not able to make PIREPs by radio, reporting upon landing of the in-flight conditions encountered to the nearest AFSS/FSS or Weather Forecast Office will be helpful
  • Some of the uses made of the reports are:
    1. The ATCT uses the reports to expedite the flow of air traffic in the vicinity of the field and for hazardous weather avoidance procedures
    2. The AFSS/FSS uses the reports to brief other pilots, to provide in-flight advisories, and weather avoidance information to en route aircraft
    3. The ARTCC uses the reports to expedite the flow of en route traffic, to determine most favorable altitudes, and to issue hazardous weather information within the center's area
    4. The NWS uses the reports to verify or amend conditions contained in aviation forecast and advisories. In some cases, pilot reports of hazardous conditions are the triggering mechanism for the issuance of advisories. They also use the reports for pilot weather briefings
    5. The NWS, other government organizations, the military, and private industry groups use PIREPs for research activities in the study of meteorological phenomena
    6. All air traffic facilities and the NWS forward the reports received from pilots into the weather distribution system to assure the information is made available to all pilots and other interested parties
  • The FAA, NWS, and other organizations that enter PIREPs into the weather reporting system use a standard format [Figure 1]
    • Items 1 through 6 are included in all transmitted PIREPs along with one or more of items 7 through 13
    • Although the PIREP should be as complete and concise as possible, pilots should not be overly concerned with strict format or phraseology
    • The important thing is that the information is relayed so other pilots may benefit from your observation
    • If a portion of the report needs clarification, the ground station will request the information
    • Completed PIREPs will be transmitted to weather circuits as in the following examples
Aeronautical Information Manual, PIREP Element Code Chart
Figure 1: Aeronautical Information Manual, PIREP Element Code Chart
  • Example:
    • KCMH UA /OV APE 230010/TM 1516/FL085/TP BE20/SK BKN065/WX FV03SM HZ FU/TA 20/TB LGT
      • One zero miles southwest of Appleton VOR; time 1516 UTC; altitude eight thousand five hundred; aircraft type BE200; bases of the broken cloud layer is six thousand five hundred; flight visibility 3 miles with haze and smoke; air temperature 20°C; light turbulence
      • From 15 miles north of Beckley VOR to Charleston VOR; time 1815 UTC; altitude 12,000 feet; type aircraft, BE-99; in clouds; rain; temperature minus 8°C; wind 290° magnetic at 30 knots; light to moderate turbulence; light rime icing during climb northwest bound from Roanoke, VA, between 8,000 and 10,000 feet at 1750 UTC

PIREPs Relating to Turbulence:

  • When encountering turbulence, pilots are urgently requested to report such conditions to ATC as soon as practicable
  • PIREPs relating to turbulence should state:
    1. Aircraft location
    2. Time of occurrence in UTC
    3. Turbulence intensity [Figure 2]
    4. Whether the turbulence occurred in or near clouds
    5. Aircraft altitude or flight level
    6. Type of aircraft
    7. Duration of turbulence
  • Example:
    • Over Omaha, 1232Z, moderate turbulence in clouds at Flight Level three one zero, Boeing 707
    • From five zero miles south of Albuquerque to three zero miles north of Phoenix, 1250Z, occasional moderate chop at Flight Level three three zero, DC8
  • Duration and classification of intensity should be made using [Figure 2]
Aeronautical Information Manual, Turbulence Reporting Criteria Table
Figure 2: Aeronautical Information Manual, Turbulence Reporting Criteria Table
Aeronautical Information Manual, Icing Types
Figure 3: Aeronautical Information Manual, Icing Types

PIREPs Relating to Airframe Icing:

  • The effects of ice on aircraft are cumulative as thrust is reduced, drag increases, lift lessens, and weight increases
    • The results are an increase in stall speed and a deterioration of aircraft performance
    • In extreme cases, 2 to 3 inches of ice can form on the leading edge of the airfoil in less than 5 minutes
    • It takes but 1/2 inch of ice to reduce the lifting power of some aircraft by 50% and increases the frictional drag by an equal percentage
  • A pilot can expect icing when flying in visible precipitation, such as rain or cloud droplets, and the temperature is between +02 and -10° Celsius
    • When icing is detected, a pilot should do one of two things, particularly if the aircraft is not equipped with deicing equipment; get out of the area of precipitation; or go to an altitude where the temperature is above freezing
    • This "warmer" altitude may not always be a lower altitude
      • Proper preflight action includes obtaining information on the freezing level and the above freezing levels in precipitation areas
    • Report icing to ATC, and if operating IFR, request new routing or altitude if icing will be a hazard
      • Be sure to give the type of aircraft to ATC when reporting icing
  • Reporting Icing Conditions:
    1. Trace: Ice becomes perceptible. Rate of accumulation slightly greater than sublimation. Deicing/anti-icing equipment is not utilized unless encountered for an extended period of time (over 1 hour)
    2. Light: The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Occasional use of deicing/anti-icing equipment removes/prevents accumulation. It does not present a problem if the deicing/anti-icing equipment is used
    3. Moderate: The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or flight diversion is necessary
    4. Severe: The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. Immediate flight diversion is necessary
  • Aeronautical Information Manual, Icing Conditions
    Figure 4: Aeronautical Information Manual, Icing Conditions
  • Example:
    • Pilot: "[Agency], this is [Identification], [Location], [Time (UTC)], [Intensity of Type], [Altitude/FL], [Aircraft Type], [Indicated Air Speed (IAS)], and [Outside Air Temperature (OAT)]"
    • Pilot: "Washington Center, this is N1727V, VORTAC, at 1800, experiencing trace icing at 10,000 feet, cessna 172, 120 knots, indicating -10 degrees C OAT"
  • Rime ice. Rough, milky, opaque ice formed by the instantaneous freezing of small supercooled water droplets
  • Clear ice. A glossy, clear, or translucent ice formed by the relatively slow freezing of large supercooled water droplets
  • The OAT should be requested by the AFSS/FSS or ATC if not included in the PIREP

PIREPs Relating to Volcanic Ash Activity:

  • Volcanic eruptions which send ash into the upper atmosphere occur somewhere around the world several times each year
    • Flying into a volcanic ash cloud can be extremely dangerous
    • Regardless of the type aircraft, some damage is almost certain to ensue after an encounter with a volcanic ash cloud
  • Additionally, studies have shown that volcanic eruptions are the only significant source of large quantities of sulphur dioxide (SO2) gas at jet-cruising altitudes
    • Therefore, the detection and subsequent reporting of SO2 is of significant importance
    • Although SO2 is colorless, its presence in the atmosphere should be suspected when a sulphur-like or rotten egg odor is present throughout the cabin
  • While some volcanoes in the U.S. are monitored, many in remote areas are not
    • These unmonitored volcanoes may erupt without prior warning to the aviation community
    • A pilot observing a volcanic eruption who has not had previous notification of it may be the only witness to the eruption
    • Pilots are strongly encouraged to transmit a PIREP regarding volcanic eruptions and any observed volcanic ash clouds or detection of sulphur dioxide (SO2) gas associated with volcanic activity
      • Pilots should submit PIREPs regarding volcanic activity using the Volcanic Activity Reporting (VAR) form
      • If a VAR form is not immediately available, relay enough information to identify the position and type of volcanic activity
        • Pilots should verbally transmit the data required in items 1 through 8 of the VAR as soon as possible. The data required in items 9 through 16 of the VAR should be relayed after landing if possible

PIREPS Relating to Clear Air Turbulence:

  • Clear Air Turbulence (CAT) has become a very serious operational factor to flight operations at all levels and especially to jet traffic flying in excess of 15,000'
  • The best available information on this phenomenon must come from pilots via the PIREP reporting procedures
  • All pilots encountering CAT conditions are urgently requested to report time, location, and intensity (light, moderate, severe, or extreme) of the element to the FAA facility with which they are maintaining radio contact
  • If time and conditions permit, elements should be reported according to the standards for other PIREPs and position reports

Finding PIREPs: PIREP Query
Figure 5: PIREP Query

Case Studies:

  • NTSB Identification: LAX05FA088: The National Transportation Safety Board determines the probable cause(s) of this accident to be: the pilot's in-flight loss of control following an inadvertent encounter with unforecast severe icing conditions. A factor in the accident was the inaccurate icing forecast developed by the NWS Aviation Weather Center


  • Case studies can show us that pilot reports have the potential to prevent accidents and loss of life
  • According to FAR 91.183, IFR Communications, aircraft operating under IFR must report any unforecast weather conditions encountered
  • According to AIM 5-3-3, Additional Reports, aircraft in general must report anything that pertains to safety of flight and when encountering weather conditions which have not been forecast, or hazardous conditions which have been forecast
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