International NOTAM Office — Page 35, Lesson 33

I want to walk you through the start of the International NOTAM Office section of your Communications manual. This page is essentially a glossary of abbreviations and acronyms used in aviation communications and documentation. Let's go through them in order, defining each one clearly. We begin with NOSIG — that stands for No Significant Change. This is used specifically in trend-type landing forecasts. When a forecaster appends NOSIG to a landing forecast, it means they expect no significant change in the weather conditions during the trend period. Next is NOTAM itself. This is a critical term. A NOTAM is a notice containing information concerning the establishment, condition, or change in any aeronautical facility, service, procedure, or hazard — the timely knowledge of which is essential to personnel concerned with flight operations. So if a runway light is out, a navigation aid is off the air, or a new obstacle goes up near an airport, that information goes into a NOTAM. It's the system that keeps pilots and operations staff aware of anything that could affect the safety or efficiency of a flight. Then we have NOV — simply the abbreviation for November. NR stands for Number. NRH means No Reply Heard. If a controller or pilot calls a station and gets no response, they might log or report NRH. NS is Nimbostratus — that's a cloud type. Nimbostratus is a thick, grey cloud layer that produces steady precipitation, usually rain or snow. NSC stands for Nil Significant Cloud. When reported in a meteorological message, it means there are no clouds of operational significance — typically no cloud below 5,000 feet above aerodrome level or below the minimum sector altitude, whichever is higher. NSW is Nil Significant Weather — no significant weather phenomena present. NW is North West. NWB means North Westbound. NXT is Next. Moving to the letter O. OAC stands for Oceanic Area Control Centre. This is the air traffic control unit responsible for controlling aircraft in oceanic airspace — over the open ocean where radar coverage is not available. OAS is Obstacle Assessment Surface. This is an imaginary surface used in obstacle limitation and assessment around aerodromes, to determine whether an obstacle protrudes into protected airspace. OAT stands for Operational Air Traffic. Obs — this one has two meanings listed. First, Obstacle lights — the lights fitted to tall structures to warn aircraft. Second, Observe OR Observed OR Observation — used in meteorological reports to indicate that a weather element was observed rather than forecast. OBS is Observe OR Observed OR Observation — same abbreviation, same meaning as Obs but with a different abbreviation format. OBSC means Obscure OR Obscured OR Obscuring — used when a cloud layer or precipitation obscures part of the sky or a feature like a mountain. OBST is Obstacle. Now we come to OCA — Obstacle Clearance Altitude. This is the lowest altitude above sea level used to ensure adequate clearance from obstacles in the approach area. It's a critical value for instrument approach procedures. OCC stands for Occulting (light) — a type of light signal where the periods of light are longer than the periods of darkness. OCH is Obstacle Clearance Height — similar to OCA, but measured above the aerodrome elevation or the threshold elevation, rather than above sea level. OCNL means Occasional OR Occasionally — used in forecasts to describe weather phenomena that occur with a low frequency. OCS is Obstacle Clearance Surface — another imaginary surface used to define the area within which obstacles must be cleared for a safe approach. OCT is October. OHD stands for Overhead. OIS is Obstacle Identification Surface — a surface used to identify obstacles that need to be considered for departure procedures. OLR means Off Load Routes. OM is Outer Marker — a radio beacon located on the approach path, typically about 4 to 7 nautical miles from the runway threshold, used as a position fix during an instrument approach. OPA stands for Opaque, white type of ice formation — a type of ice that forms on aircraft surfaces, opaque and white in appearance. OPC means The control indicated is Operational Control — used in flight plan or communication contexts to specify who has operational control of the flight. OPMET is Operational Meteorological (information) — meteorological information prepared specifically for aviation operations. OPN stands for Open OR Opening OR Opened. OPR means Operator OR Operate OR Operative OR Operating OR Operational. OPS is Operations. O/R stands for On Request — meaning something is available or will be provided only when requested. ORCAM is Originator Region Code and Mode — a specific code used in the aeronautical telecommunications network. ORD means Indication of an Order. OSV is Ocean Station Vessel — a ship stationed in the ocean to provide meteorological observations and, historically, search and rescue support. OTLK stands for Outlook — used in SIGMET messages specifically for volcanic ash and tropical cyclones, to indicate expected conditions beyond the main validity period. OTP means On Top — used when an aircraft is flying above a cloud layer. OTS is Organized Track System — the system of predefined routes across the North Atlantic that changes daily based on wind and weather conditions. OUBD means Outbound. OVC is Overcast — sky condition where more than eight oktas (eighths) of the sky is covered by cloud. Moving to the letter P. P followed by an identification means Prohibited area — airspace of defined dimensions where flight is prohibited. PALS is Precision Approach Lighting System — a system of lights that provides visual guidance to pilots during the final approach, with specific categories indicated. PANS stands for Procedures for Air Navigation Services — the ICAO documents that specify detailed procedures for air navigation. PAPA is Parallax Aircraft Parking Aid — a visual aid to help pilots park aircraft accurately at the gate. PAPI is Precision Approach Path Indicator — a visual aid that gives pilots a precise indication of their vertical position relative to the correct glidepath, using red and white lights. PAR is Precision Approach Radar — a radar system used by controllers to guide aircraft onto the runway during an approach, providing both azimuth and elevation guidance. PARL means Parallel. PAX stands for Passenger(s). PCD means Proceed OR Proceeding. PCN is Pavement Classification Number — a number that indicates the load-bearing capacity of a pavement, used to determine whether an aircraft can operate on that pavement. PDG is Procedure Design Gradient — the minimum climb gradient required for a departure procedure. PE stands for Ice Pellets — a type of precipitation. PEC is Pressure Error Correction — a correction applied to altimeter readings due to errors in the static pressure system. PER means Performance. PERM is Permanent. PH stands for Public Holiday. PIB is Preflight Information Bulletin — a bulletin containing all relevant NOTAMs and other operational information for a specific flight. PJE means Parachute Jumping Exercise. PLA is Practice Low Approach. PLN stands for Flight Plan. PLS is Passenger Load Supplement. PLVL means Present Level. PN means Prior Notice required — indicating that advance notice is needed for a service or clearance. PndB is Perceived Noise Decibels — a unit for measuring perceived noise level, used in aircraft noise certification. PNR is Point of No Return — the point on a flight beyond which the aircraft no longer has enough fuel to return to its departure aerodrome. PO stands for Dust Devils — small, rotating columns of dust or sand. POB means Persons on Board — the total number of people on an aircraft, including crew and passengers. That covers the full set of abbreviations from NOSIG through POB on this page. These are the standard ICAO abbreviations you will see in NOTAMs, meteorological messages, flight plans, and operational communications.