Aeronautical Information Service (AIS) — Page 364, Lesson 489

Let's pick up with the ASHTAM colour code, because that's the heart of field E of an ASHTAM — the volcano alert level. I want you to know this cold, because it's a direct operational decision-maker for flight crews. The ASHTAM colour code has four levels: Red, Orange, Yellow, and Green. Each one tells you the state of volcanic activity, and crucially, whether any ash plume is reaching or expected to reach above Flight Level 250. That's the key altitude threshold — FL250, which is 25,000 feet in the standard pressure setting. Red is the most severe. It means a volcanic eruption is in progress, and a pyroclastic ash plume or cloud has been reported above FL250. Alternatively, the volcano is dangerous and an eruption is likely, with the pyroclastic ash plume or cloud expected to rise above FL250. So Red always involves ash above FL250, either already there or expected. Orange is a step down. It still means an eruption is in progress, but the pyroclastic ash plume or cloud is not reaching, and not expected to reach, FL250. Or the volcano is dangerous and an eruption is likely, but the plume is not expected to reach FL250. So the key contrast between Red and Orange is purely that FL250 threshold — Red is above, Orange is below. Yellow is a cautionary state. The volcano is known to be active from time to time, and volcanic activity has recently increased significantly. The volcano is not currently considered dangerous, but caution should be exercised. There's also a second scenario for Yellow: after a volcanic eruption — meaning a change in alert from Red or Orange down to Yellow — the volcanic activity has decreased significantly. Again, not currently dangerous, but caution should be exercised. Green is the all-clear. Volcanic activity is considered to have ceased, and the volcano has reverted to its normal state. Now, one thing to note: this colour code is used in field E of the ASHTAM. That's the specific field where the alert level goes. And I want you to remember the exact wording of the definitions, because examiners will test the precise conditions — especially the "not reaching nor expected to reach FL250" phrasing for Orange, and the two distinct Yellow scenarios. Now let's move to the next topic: Aeronautical Information Circulars, or AICs. These are a completely different dissemination method from the AIP or NOTAM. An AIC is a method whereby information that does not qualify for inclusion in the AIP, or is not suitable for a NOTAM, is disseminated to all interested parties. So think of it as the catch-all channel — if it doesn't fit the permanent AIP or the urgent NOTAM, it goes into an AIC. An AIC is originated whenever it's desirable to promulgate three types of information. First, a long-term forecast of any major change in legislation, regulations, procedures, or facilities. Second, information of a purely explanatory or advisory nature that is liable to affect flight safety. Third, information or notification of an explanatory or advisory nature concerning technical, legislative, or purely administrative matters. Now the general specifications of AICs. They are issued in printed form, and both text and diagrams may be included. The originating State can select which AICs are given international distribution — so not every AIC necessarily goes worldwide. Each AIC is allocated a serial number, which should be consecutive and based on the calendar year. When AICs are distributed in more than one series, each series is separately identified by a letter. So you might have series A, B, C, and so on. For differentiation and identification of AIC topics according to subject, it's normal to use a colour coding system — meaning the paper on which the information is published is distinguished by topic by different colours. That's the colour coding you see in the figure. A checklist of AICs currently in force is issued at least once a year, with distribution the same as for the AIC itself. And in the UK specifically, AICs are published on Thursdays every 28 days. That's a specific national detail worth remembering. So to tie it together: AICs handle the long-term, explanatory, advisory, and administrative material that doesn't fit the AIP or NOTAM. They're printed, serial-numbered by calendar year, optionally split into lettered series, colour-coded by topic, and checked annually.