Aeronautical Information Service (AIS) — Page 353, Lesson 475

We’re starting a new topic now: the Aeronautical Information Service, or AIS. This is the machinery that gets aviation information from the people who know it to the people who need it — pilots, operators, air traffic services. Let me walk you through how it’s structured. First, the scope of the AIS. It’s responsible for receiving and/or originating, collating or assembling, editing, formatting, publishing, storing, and distributing aeronautical information and data. And that covers the entire territory of the State, plus any areas outside its territory where that State is responsible for air traffic services. So it’s a complete, State-wide information pipeline. All of that information is published in one standard form, called the Integrated Aeronautical Information Package — the IAIP. Now, before we go into the package itself, there’s a critical technical foundation: the World Geodetic System 1984, or WGS-84. Since 1 January 1998, all published geographical co-ordinates — latitude and longitude — used in aviation have been expressed in WGS-84. That’s the global standard reference frame. Then, since 5 November 1998, something extra became mandatory: in addition to the elevation, which is referenced to mean sea level, the AIP AD section must also publish the geoid undulation for those surveyed ground positions. Let me unpack that. The geoid undulation is the gravity variation caused by the varying radius of the Earth, referenced to the WGS-84 ellipsoid. In plain terms, the Earth isn’t a perfect sphere, so the “sea level” surface and the mathematical ellipsoid don’t perfectly coincide — the undulation is the difference between them. And this matters for satellite orbits used in SatNav systems, because those systems rely on the WGS-84 frame. Now the heart of it: the Integrated Aeronautical Information Package. It’s defined as a system of dissemination of information essential to aviation operations and safety. It consists of six elements: the Aeronautical Information Publication, or AIP, including its amendment service; Supplements to the AIP; NOTAM and pre-flight information bulletins, the PIBs; Aeronautical Information Circulars, the AICs; and Checklists and Summaries. Let’s focus on the AIP itself. It’s designed to allow information of a generally “static” nature to be published — static meaning it doesn’t change often — and, if practicable, in a form that can be used in flight. Think instrument approach plates or SID plates, the standard instrument departure charts. The AIP is required to be the definitive reference for permanent information and for information concerning long-duration temporary changes. That’s a key point: aircrew and operators can rely on it being accurate and up to date. But note the limitation — the AIP does not contain aerodrome operating minima. Those are defined by the operator, for example the visual criteria to continue an instrument approach. So the AIP gives you the permanent data, but the operator sets the operating limits. The AIP consists of three parts. Part 1 is General, abbreviated GEN. Part 2 is En route, ENR. Part 3 is Aerodrome Data, AD. Part 1, GEN, contains information of a regulatory and administrative nature, and it has five sections. Here’s a crucial detail for you: differences to the ICAO SARPs and PANS — that’s Standards and Recommended Practices, and Procedures for Air Navigation Services — notified by the State publishing the AIP are detailed fully at GEN 1.7. That’s the usual method of referring to AIP contents. So if a State deviates from the international standards, you’ll find the full details at GEN 1.7. The complete content of Part 1 is laid out by headings, but for your learning objectives, you only need to recall the location of the information shown in bold italics — so focus on where things sit, like GEN 1.7, rather than memorising every heading. That’s the AIS and the IAIP structure. We’ve covered the WGS-84 co-ordinate system, the geoid undulation, the six elements of the package, and the three-part AIP with the GEN 1.7 referral point.