Meteorological Information for Aircraft in Flight — Page 549, Lesson 525

I want to walk you through the Automatic Terminal Information Service — ATIS — and how it works in practice. This is a core part of the meteorological information available to you as a pilot, both before you start moving and while you're in flight. Let's begin with how you find out what ATIS is available. Figure 29.4 shows an extract from the Aerodrome section of the United Kingdom Aeronautical Information Publication — the UK AIP. That extract illustrates that at Manchester Airport, both an arrival ATIS and a departure ATIS are available, and they operate on different frequencies. So if you're arriving at Manchester, you tune one frequency; if you're departing, you tune another. The extract also shows that at Southampton Airport, the ATIS broadcast is made on the Southampton VOR frequency itself — meaning you can pick up the aerodrome's weather information while you're navigating using that VOR. Now, how does ATIS stay current? If the current aerodrome weather conditions change, or if there is any change in other pertinent aerodrome information — for example, a different runway in use, or a change in the altimeter setting — the ATIS broadcast is immediately updated to reflect those changes. The updated broadcast is then given a new, sequential alphabetical code. So if the previous broadcast was ALPHA, the updated one becomes BRAVO. This letter code is crucial. Why? Because on initial contact with Air Traffic Control, a pilot is required to state the identifying letter code of the ATIS information last received. That way, ATC knows that the pilot has the most recent information. If you say "I have information BRAVO," the controller knows you're up to date. If you say "ALPHA," they know you have old information and will need to be updated. ATIS is broadcast in plain language — not in coded shorthand — and it contains some or all of the following items, if they are applicable. Let me list them for you: - The aerodrome name. - The ATIS sequence designator, which is that information code — ALPHA, BRAVO, etc. - The time of observation — when the weather was actually measured. - The runway in use and its status — for example, whether it's wet or dry. - Surface wind in knots, and referenced to magnetic north — so you know the direction the wind is coming from relative to magnetic heading. - Visibility and RVR — Runway Visual Range. - Present weather — what's actually happening, like rain or snow. - Significant cloud — cloud amount and height. - Temperature and dew point. - Altimeter setting — the QNH, which you set on your altimeter. - Transition level — the altitude at which you change from local pressure setting to the standard 1013.2 hPa. - Type of approach expected — for example, an ILS approach or a visual approach. - And finally, any warnings pertinent to flight operations — things like wind shear advisories or bird activity. Now let's talk about how you actually use ATIS. On departure from an aerodrome, you should obtain the ATIS information before you make initial contact with Air Traffic Control. When you do make that first call, you must mention the identifying letter of the ATIS broadcast you obtained. That confirms to the controller that you have the latest airfield information. For a pilot arriving at an aerodrome, the same principle applies: you should listen to the ATIS broadcast before transmitting on the aerodrome's initial contact frequency. When the controller hears that you have the latest ATIS, they may omit certain details in their reply that are already contained in the ATIS broadcast — that keeps the radio transmission shorter. However, the aerodrome QNH will normally always be confirmed by the controller anyway, just to be sure. What if you don't acknowledge receipt of the latest ATIS broadcast on initial contact? In that case, the controller will pass the essential aerodrome information to you directly. So it's in your interest to have listened to ATIS first, because otherwise you'll get a longer transmission from the controller. The whole point of this system is efficiency. Obtaining the latest ATIS information helps ensure that radio transmissions between Air Traffic Control and the pilot are kept to a minimum. This is especially important in busy airspace, where radio transmissions must be kept short to allow for effective communication between controllers and all the aircraft they are serving. ATIS lets you get the bulk of the information without having to ask for it, and without the controller having to read it all out to every aircraft.