A pilot report or PIREP is a report of actual flight or ground conditions encountered by an

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. ...

. Reports commonly include information about atmospheric conditions (like

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied on ...

, icing,

turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...

) or airport conditions (like

runway condition code Runway safety is concerned with reducing harm that could occur on an aircraft runway. Safety means avoiding incorrect presence (incursion) of aircraft, inappropriate exits (excursion) and use of the wrong runway due to confusion. The runway conditi ...

s or ground equipment failures). This information is usually relayed by

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transm ...

to the nearest ground station, but other options (e.g. electronic submission) also exist in some regions. The message would then be encoded and relayed to other weather offices and air traffic service units. Although the actual form used to record the PIREP may differ from one country to another, the standards and criteria will remain almost the same. At a minimum the PIREP must contain a header, aircraft location, time, flight level, aircraft type and one other field. In recent years, a PIREP will also include UA or UUA used to identify the PIREP as routine or urgent.

Included data

Mandatory

*UA or UUA used to identify the PIREP as routine or urgent (In Canada this is indicated by the prefix to the PIREP: "UACN01" for an urgent PIREP or "UACN10" for a normal PIREP) */OV location of the PIREP, in relation to a NAVAID, an aerodrome or geographical coordinates */TM time the PIREP was received from the pilot ( UTC) */FL

flight level In aviation and aviation meteorology, a flight level (FL) is an aircraft's altitude at standard air pressure, expressed in hundreds of feet. The air pressure is computed assuming an International Standard Atmosphere pressure of 1013.25 h ...

altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...

above

sea level Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardise ...

at the time the PIREP is filed; it is essential for turbulence and icing reports */TP aircraft type; it is essential for turbulence and icing reports

Optional (at least one is required)

*/SK

sky cover In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compo ...

*/TA ambient temperature; important for icing reports */WV wind vector referenced in terms of

true north True north (also called geodetic north or geographic north) is the direction along Earth's surface towards the geographic North Pole or True North Pole. Geodetic north differs from ''magnetic'' north (the direction a compass points toward t ...

(ICAO), or

magnetic north The north magnetic pole, also known as the magnetic north pole, is a point on the surface of Earth's Northern Hemisphere at which the planet's magnetic field points vertically downward (in other words, if a magnetic compass needle is allowed ...

(in the United States) */TB

; intensity, whether it occurred in or near clouds, and duration */IC icing */RM remarks */WX flight visibility and weather

AIREP

Like PIREPs, Aircraft Reports (AIREP) are reports of actual weather conditions of an aircraft in flight. AIREPs are often automated reports, contrary to PIREPs. Likewise, a different

encoding In communications and information processing, code is a system of rules to convert information—such as a letter (alphabet), letter, word, sound, image, or gesture—into another form, sometimes data compression, shortened or secrecy, secret ...

is used for either type.

Body

The message identifier "UA" is used when the PIREP contains non-hazardous weather information. If the PIREP contains a report of a

tornado A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, alt ...

funnel cloud A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud (usually a cumulonimbus or towering cumulus cloud) but not reaching the ground or a water s ...

waterspout A waterspout is an intense columnar vortex (usually appearing as a funnel-shaped cloud) that occurs over a body of water. Some are connected to a cumulus congestus cloud, some to a cumuliform cloud and some to a cumulonimbus cloud. In the c ...

, severe

, severe icing,

hail Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets generally fal ...

, or a low-level

wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizon ...

hazard, the identifier "UUA" would be used. The location (/OV) can be reported in one of three ways: as a direction and distance from a navigation aid (NAVAID), as a direction and distance from an airport, or as the

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north po ...

and

longitude Longitude (, ) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek let ...

of the aircraft. The time (/TM) used is the UTC time that the PIREP is reported. The flight level (/FL) is reported as either a three digit value that indicates the altitude of the aircraft above sea level in hundreds of feet or can be one of three abbreviations: DURD (during descent or on approach), DURC (during climb or after takeoff) and UNKN (unknown). Aircraft type (/TP) will be the approved

ICAO The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international ...

designator, or UNKN if not reported. Sky cover (/SK) is used to report the

cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...

layer amounts and the height of the cloud base. The tops of the cloud layers can also be included, as can more than one layer of cloud. Heights are in hundreds of feet above sea level and are three digits. Abbreviations used in this group are "CLR" (clear), "FEW" (few), "SCT" (scattered), "BKN" (broken) and "OVC" (overcast). Temperature (/TA) is the air temperature in whole degrees Celsius as a two-digit value, with negative temperatures preceded by a minus (-) sign. In the United States, negative temperatures are preceded by the letter M (M). Wind velocity (/WV) must contain both the wind speed and direction. Direction is reported as a three-digit value in whole degrees true and the wind speed in knots also in three digits. Turbulence (/TB) and the intensity are reported in a PIREP based on the aircraft and occupants reaction to the turbulence. The altitude of the turbulence should be included using three-digit groups. When the top or the base of the turbulence is unknown then the abbreviation BLO (below) or ABV (above) should be used. Turbulence should be reported as LGT (light), MDT (moderate), SVR (severe) or in exceptional cases EXTRM (extreme).

Clear-air turbulence In meteorology, clear-air turbulence (CAT) is the turbulent movement of air masses in the absence of any visual clues, such as clouds, and is caused when bodies of air moving at widely different speeds meet. The atmospheric region most suscep ...

is reported as CAT. Icing (/IC) is reported by type and the intensity or rate of accretion. The type of ice is reported as "CLR" (clear), " RIME", or "MXD" (mixed). The intensity is reported as "TR" (trace), "LGT" (light), "MDT" (moderate), and "SVR" (severe). (Units are measured in MSL - MEAN SEA LEVEL) Remarks (/RM) report on other weather conditions that are not covered in the rest of the PIREP may include such things as icing in precipitation,

thunderstorms A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are some ...

, St. Elmo's fire and frontal conditions. There are many other types of weather conditions that could be reported in a PIREP. The above explanation of PIREP fields is Canadian. The United States version may also include a weather (/WX) group, while other countries may use other groups and measurements.

Examples of PIREPs

These examples are taken from the Canadian MANOBS (Manual of Surface Weather Observations) published by Environment Canada. *PIREP: ::UACN10 CYQT 192128 ::YZ WG ::UA /OV YSP 090025 /TM 2120 /FL050 /TP BE99 /SK 020BKN040 110OVC /TA -14 /WV 030045 /TB MDT CAT 060-080 /IC LGT RIME 020-040 /RM LGT FZRA INC :Decoded as: ::Routine upper air report from

Thunder Bay Thunder Bay is a city in and the seat of Thunder Bay District, Ontario, Canada. It is the most populous municipality in Northwestern Ontario and the second most populous (after Greater Sudbury) municipality in Northern Ontario; its populatio ...

issued at 2128 UTC on the 19th of the month ::YZ is

Toronto Toronto ( ; or ) is the capital city of the Provinces and territories of Canada, Canadian province of Ontario. With a recorded population of 2,794,356 in 2021, it is the List of the largest municipalities in Canada by population, most pop ...

and WG is

Winnipeg Winnipeg () is the capital and largest city of the province of Manitoba in Canada. It is centred on the confluence of the Red and Assiniboine rivers, near the longitudinal centre of North America. , Winnipeg had a city population of 749 ...

: these are the Flight Information Regions where the PIREP was issued ::Aircraft observation was east (090 degrees radial) of the

Marathon The marathon is a long-distance foot race with a distance of , usually run as a road race, but the distance can be covered on trail routes. The marathon can be completed by running or with a run/walk strategy. There are also wheelchair di ...

VOR/ DME at 2120 UTC. The aircraft was at and is a

Beech 99 The Beechcraft Model 99 is a civilian aircraft produced by Beechcraft. It is also known as the Beech 99 Airliner and the Commuter 99. The 99 is a twin-engine, unpressurized, 15 to 17 passenger seat turboprop aircraft, derived from the earlier Be ...

. The clouds were broken at AMSL with tops at and an overcast layer at AMSL. The temperature is −14 degrees Celsius and the winds are from the northeast (030 degrees true) at . There is moderate clear air turbulence between and . There is light rime icing between and . Note this would indicate that the icing is picked up in the cloud. The remarks section says that light freezing rain was encountered in the cloud. *PIREP ::UACN10 CYXU 032133 ::YZ ::UA /OV YUX 09010 /TM 2120 /FL030 /TP C172 /TB MDT /RM MDT TURB BLO 050 CYKF CYXU :Decoded as: ::Routine message from

London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...

, issued at 2133 UTC on the 3rd of the month ::The Flight Information Region is Toronto ::The aircraft was east (090 degrees radial) of the London VOR at 2120 UTC. The aircraft was at and was a

Cessna 172 The Cessna 172 Skyhawk is an American four-seat, single-engine, Monoplane#High, high wing, fixed-wing aircraft made by the Cessna Aircraft Company.

. The pilot reported moderate turbulence. The remarks says that the turbulence was below between

Kitchener Kitchener may refer to: People * Earl Kitchener, a title in the Peerage of the United Kingdom ** Herbert Kitchener, 1st Earl Kitchener (1850–1916), British Field Marshal and 1st Earl Kitchener ** Henry Kitchener, 2nd Earl Kitchener (1846–1937) ...

Waterloo Waterloo most commonly refers to: * Battle of Waterloo, a battle on 18 June 1815 in which Napoleon met his final defeat * Waterloo, Belgium, where the battle took place. Waterloo may also refer to: Other places Antarctica *King George Island (S ...

and London.

Soliciting PIREPs

In the US,

air traffic controller Air traffic control specialists, abbreviated ATCS, are personnel responsible for the safe, orderly, and expeditious flow of air traffic in the global air traffic control system. Usually stationed in air traffic control centers and control ...

s are required to solicit PIREPs upon request of other facilities or pilots, or when any of the following conditions exists or is forecast in their area:Aeronautical Information Manual (AIM) 7-1-20 Pilot Weather Reports (PIREPs)
/ref> * Ceilings at or below *Visibility at or less than *

Thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are somet ...

s and related phenomena *

Turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...

of moderate degree or greater *Icing of light degree or greater *

Wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizon ...

Volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer ...

clouds At least once hourly, terminal controllers must obtain a descent/climb-out PIREP, including cloud information and other related phenomena.

References

* Aeronautical Information Manual, dated April 3, 2014
p. 472

External links

{{Earth-based meteorological observation Aviation meteorology Earth sciences data formats Aviation publications