ATIS

[SwingWingJoc]

In the UK, it would appear that the ATIS code changes every 30mins. This means that during almost every approach from top of decent the ATIS code will change. More often than not, there are no significant changes to ATC/weather/info. Why?

[niknak]

The ATIS information code (letter) will change everytime there the metar is updated, and/or when there is a significant change of any other condition broadcast on that particular ATIS.

That means that, at our place (not too far away from you), every time we make a weather observation and transmit it as a metar (every 30 mins), the ATIS will change letter.
If there is a significant change in any element of the weather between that time we also transmit that, it goes to the Met Office as a metar "special" but also goes onto the ATIS and the letter changes.
If we change runway, or need to notify pilots of a significant event or unservicability i.e Windshear, U/S Nav aid, partial unservicability, airport closed, change of runway surface conditions etc, it goes out on the ATIS and the letter will change.

If an aircraft is inbound and not yet on final approach, we will endeavour to pass the changes verbally, if we're too busy we inform them that ATIS is now information "C" and the pilot is obliged to listen again.
If the aircraft is established or nearly so, on the final approach aid, the significant change will be passed to them verbally.

There are instances when the change will not be passed because it is not relavant to that particular flight.