The submission of a PIREP can be initiated by both the pilot or an air traffic controller
Air Traffic Control:
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:
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., FSS, ARTCC, or terminal ATC
One of the primary duties of the Inflight position 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:
The ATCT uses the reports to expedite the flow of air traffic in the vicinity of the field and for hazardous weather avoidance procedures
The AFSS/FSS uses the reports to brief other pilots, to provide in-flight advisories, and weather avoidance information to en route aircraft
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
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
The NWS, other government organizations, the military, and private industry groups use PIREPs for research activities in the study of meteorological phenomena
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
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
Issuance & Validity:
Issued when/as reports are received
Valid for current conditions and contain no forecasted data
PIREPs Relating to Turbulence:
When encountering turbulence, pilots are urgently requested to report such conditions to ATC as soon as practicable
Turbulence PIREP Information:
Aircraft location
Time of occurrence in UTC
Turbulence intensity [Figure 2]
Whether the turbulence occurred in or near clouds
Aircraft altitude or flight level
Type of aircraft
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 in accordance with FAA guidance [Figure 2]
Aeronautical Information Manual, Turbulence Reporting Criteria Table
PIREPs Relating to Airframe Icing:
Aeronautical Information Manual, Icing Conditions
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:
Trace: Ice becomes noticeable. The rate of accumulation is slightly greater than the rate of sublimation. A representative accretion rate for reference purposes is less than 1/4 inch (6 mm) per hour on the outer wing. The pilot should consider exiting the icing conditions before they become worse
Light: The rate of ice accumulation requires occasional cycling of manual deicing systems to minimize ice accretions on the airframe. A representative accretion rate for reference purposes is 1/4 inch to 1 inch (0.6 to 2.5 cm) per hour on the unprotected part of the outer wing. The pilot should consider exiting the icing condition
Moderate: The rate of ice accumulation requires frequent cycling of manual deicing systems to minimize ice accretions on the airframe. A representative accretion rate for reference purposes is 1 to 3 inches (2.5 to 7.5 cm) per hour on the unprotected part of the outer wing. The pilot should consider exiting the icing condition as soon as possible
Severe: The rate of ice accumulation is such that ice protection systems fail to remove the accumulation of ice and ice accumulates in locations not normally prone to icing, such as areas aft of protected surfaces and any other areas identified by the manufacturer. A representative accretion rate for reference purposes is more than 3 inches (7.5 cm) per hour on the unprotected part of the outer wing. By regulation, immediate exit is required
Severe icing is aircraft dependent, as are the other categories of icing intensity. Severe icing may occur at any ice accumulation rate when the icing rate or ice accumulations exceed the tolerance of the aircraft
Aeronautical Information Manual, Icing Types
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
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 Wind Shear:
Because unexpected changes in wind speed and direction can be hazardous to aircraft operations at low altitudes on approach to and departing from airports, pilots are urged to promptly volunteer reports to controllers of wind shear conditions they encounter
An advance warning of this information will assist other pilots in avoiding or coping with a wind shear on approach or departure
When describing conditions, use of the terms "negative" or "positive" wind shear should be avoided
PIREPs of "negative wind shear on final," intended to describe loss of airspeed and lift, have been interpreted to mean that no wind shear was encountered
The recommended method for wind shear reporting is to state the loss or gain of airspeed and the altitudes at which it was encountered
Example:
Denver Tower, Cessna 1234 encountered wind shear, loss of 20 knots at 400'
Tulsa Tower, American 721 encountered wind shear on final, gained 25 knots between 600 and 400' followed by loss of 40 knots between 400' and surface
Pilots who are not able to report wind shear in these specific terms are encouraged to make reports in terms of the effect upon their aircraft
Miami Tower, Gulfstream 403 Charlie encountered an abrupt wind shear at 800' on final, max thrust required
Pilots using Inertial Navigation Systems (INS) should report the wind and altitude both above and below the shear level
Wind Shear Escape
Pilots should report to ATC when they are performing a wind shear escape maneuver. This report should be made as soon as practicable, but not until aircraft safety and control is assured, which may not be satisfied until the aircraft is clear of the wind shear or microburst. ATC should provide safety alerts and traffic advisories, as appropriate
ATC: "Denver Tower, United 1154, wind shear escape"
Once the pilot initiates a wind shear escape maneuver, ATC is not responsible for providing approved separation between the aircraft and any other aircraft, airspace, terrain, or obstacle until the pilot reports that the escape procedure is complete and approved separation has been re-established. Pilots should advise ATC that they are resuming the previously assigned clearance or should request an alternate clearance
"Denver Tower, United ll54, wind shear escape complete, resuming last assigned heading/(name) DP/clearance" or "Denver Tower, United ll54, wind shear escape complete, request further instructions"
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
Estimating Intensity of Rain and Ice Pellets:
Rain:
Light:
From scattered drops that, regardless of duration, do not completely wet an exposed surface up to a condition where individual drops are easily seen
Moderate:
Individual drops are not clearly identifiable; spray is observable just above pavements and other hard surfaces
Heavy:
Rain seemingly falls in sheets; individual drops are not identifiable; heavy spray to height of several inches is observed over hard surfaces
Ice Pellets:
Light:
Scattered pellets that do not completely cover an exposed surface regardless of duration. Visibility is not affected
Moderate:
Slow accumulation on ground. Visibility reduced by ice pellets to less than 7 statute miles
Heavy:
Rapid accumulation on ground. Visibility reduced by ice pellets to less than 3 statute miles
Estimating Intensity of Snow or Drizzle (Based on Visibility):
Light:
Visibility more than 1/2 statute mile
Moderate:
Visibility from more than 1/4 statute mile to 1/2 statute mile
Heavy:
Visibility 1/4 statute mile or less
Finding PIREPs:
PIREPs are available through ATC, Flight Service Stations, or AviationWeather.gov
The NTSB 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
Submitting a PIREP:
Radio PIREP Submission:
When transmitting PIREPs manually, it is a good idea to write them our ahead of time with what you want to say
If you can't, or you omit something, its just a conversation, and need not be so formal and robotic when being read off
If you miss a critical piece of information, a controller will ask
Electronic PIREP Submissions:
The NTSB has recognized that difficulty in the PIREP submission process has resulted in few pilots submitting PIREPs
There are many reasons to this which include: understanding, weather is as expected, or pilot workload (especially in adverse weather) including aviating and navigating
PIREPs are not just for pilots, and can influence other decisions such as weather reporting giving pilots a large amount of influence with even just a single FITREP
PIREPs are not just for adverse weather, and positive weather encountered is equally important to submit
Finally, PIREPs are often time critical events requiring submission in the moment
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
