ATIS (Automatic Terminal Information System)

For beginning students, listening to, and understanding ATIS can be daunting. There’s a new language to learn and many of the controllers speak rather quickly. With a little knowledge and practice, everyone can learn to confidently get the ATIS information. On the ground, I always encourage students to write the information down. For early students, I encourage them to call on the telephone between lessons to listen to the ATIS (at EMT, 626-444-1107) and to call before heading to the airport for a lesson.

ATIS (Automatic Terminal Information System) is a method for distributing crucial weather and airport area information at many towered airports. El Monte airport has ATIS whenever the tower is open (and AWOS when it is not). In general, ATIS information is recorded every hour, 10 to 15 minutes before the hour. It may also be updated if conditions change significantly. METARs are also used to distribute the weather portion of the ATIS, but do not include the letter identifier, runway in use, and other remarks.

Just this morning, I wrote the following down:

B 1747Z CALM CLR 5 HZ 22/14 29.89 RW19, read back, birds

Now, let’s talk about what that means.

Format

The order of information in an ATIS recording is always the same, though the content can vary considerably. Knowing what to expect makes it easier to understand. You should also understand that ATIS is a snapshot; conditions can be very different than when a recording is made.

1. Information identifier (letter)

Each recording of ATIS is assigned a letter, in order. Think of that letter as a version identifier. If Bravo (B) was recorded at 1747Z, I expect Charlie (C) to come out about one hour later. Telling the controller, when calling to taxi or inbound for landing, the letter of the ATIS, lets him know you have current information.

2. Time of recording

The time is given in “Zulu” time (a.k.a. UTC or GMT). At El Monte, we are 8 hours behind zulu, except during daylight savings, when we are 7 hours behind. The recordings are normally done between 45 and 50 minutes after the hour. There’s a few minutes delay between when the recording is made and when it is available.There is also a minute or two during which no ATIS information is available. If you don’t have ATIS, you can just tell the controller “negative ATIS” – in this case, the controller will usually read you the pertinent information. After you have written the ATIS down, you should confirm whether the time makes sense. The 1747Z says today the recording was made at 10:47AM PDT.

3. Winds

Winds can be listed as “calm”, or given as a combination of direction and speed. Wind direction indicates from which magnetic direction the winds are coming. This makes it convenient to compare wind direction with the runway in use. If I’m using runway 19 and the winds are given as 190, then I have a nearly direct headwind. Direction is sometimes listed as variable (no dominant direction) or as variable between two directions (meaning there’s a range of directions from which the wind is coming). Speed is given in knots (kts) and may either be a specific number or, a number, gusting to another number. An example of a more complicated version would be “wind one six zero at one zero gusting to two zero, variable between one four zero and two two zero,” – I would transcribe as 160/10G20 140V220. More typically we get something simple, “two two zero at one zero”: 220/10.

4. Visibility (and impacts on visibility)

Visibility is usually given in statute miles (sm) – yeah, it’s a great mixture of units we use. At many locations, any visibility greater than 10sm, is simply reported as 10sm. If there’s something impacting visibility, that  will be reported too. Examples include mist (BR), haze (HZ), and smoke (FU) [if you know French, you might better understand those letters]. Visibility can vary depending on which way you look from the airport and whether you are looking into the sun or not. If there are large variances in visibility, those may be noted as well.

5. Clouds

Clouds can occur in multiple layers. Clouds will be reported from the lowest layer to higher layers. The cloud heights are reported as feet above ground level (AGL) of the base of the clouds and the layer of clouds is reported by the coverage – few (1/8-2/8: FEW), scattered (3/8-4/8:SCT), broken (5/8-7/8:BKN) over overcast (8/8:OVC). The sky may be reported as clear (CLR/SKC) or few if the coverage is less than 1/8th of the sky. At many stations using automated reporting of clouds, you’ll get a note “sky clear below one two thousand” – this means that there may be clouds (even overcast) above 12,000′ AGL, but that is beyond the ability of the sensor to detect (or for most VFR pilots to care).

A complicated example might be “few clouds at eight hundred, scattered at two thousand, ceiling four thousand broken, one six thousand overcast”: FEW008, SCT020, BKN040, OVC160. A ceiling is defined as the lowest level that is either broken or overcast, with the assumption that VFR pilots may be unable to get above that layer. Since altitudes are not given more precisely than hundreds of feet, we drop the trailing “00” in altitudes in METARs and usually when transcribing the ATIS.

6. Temperature/dew point

This is the temperature and dew point in degrees celsius. For example, “temperature two two, dew point one four”: 22/14. The smaller the spread, the more humid and the greater the likelihood of haze, mist, or low clouds. This is omitted in some ATIS reports.

7. Altimeter setting

In the US, this is given in inches of mercury (” Hg). “altimeter two niner eight niner”: 29.89″ Hg  Once you enter the setting into the altimeter on the ground, make sure the altitude makes sense for the airport; if the altimeter setting gives the elevation as 400′ at El Monte, something is wrong (it should be around 300′).

8. Approach and runways in use

“VOR alpha approach in use, landing and departing runway one niner”. This tells us the runway(s) we should expect to be assigned for takeoff or landing. The approach information is useful to IFR (instrument flight rules) pilots. At airports with multiple runways, it may be more complicated: “ILS two six right approach in use, landing and departing runways two six left and two six right”. Sometimes parallel runways may be abbreviated as “runways two niner”  instead of “runways two niner left and two niner right”.

9. Remarks

This is the one with the most variety. Almost anything of interest to pilots can be thrown in here. At El Monte, we usually have some variation on “all aircraft read back call sign and runway assignment with all taxi and hold short instructions”. This is a reminder to do what we should already be doing in reading back certain instructions.

Another common remark at many airports is something like “use caution for birds, on, and in the vicinity of the airport” (birds like to congregate at airports).

The remarks could also indicate any special procedures at the airport, like Santa Monica’s request that “pilots contact ground control in the runup area when ready for takeoff”.

This is also where closures may be noted: “taxiways bravo and charlie closed”. It could tell you that fuel truck is broken “one hundred low lead fuel truck out of service until further notice” – 100LL OTS.

Remarks are also used to warn of nearby hazards or restrictions: “unlit crane two and a half miles northeast below four hundred AGL” or “temporary flight restriction in effect northeast, contact flight service for more information”.

If you are unsure about something included in the remarks, ask the controller.

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