Take the 2-minute tour ×
Aviation Stack Exchange is a question and answer site for aircraft pilots, mechanics, and enthusiasts. It's 100% free, no registration required.

When listening to ATC broadcasting (at least for ULLI), phrase "Information <Charlie|India|whiskey|etc.> on board" may be heard. Charlie, India, Whiskey, etc. refer to "C", "I", "W" but what do these codes mean? What kind of information is this?

share|improve this question
4  
Charlie is one of the controllers' boyfriends who lives out of town and can only visit every few weeks; India obviously refers to the nationality of the passengers and whiskey to the contents of the drinks trolley. ;-) –  David Richerby Jul 10 at 9:40
4  
...and Bravo clearly refers to the applause that comment gets for making me chuckle :) –  voretaq7 Jul 10 at 17:15

3 Answers 3

up vote 17 down vote accepted

This is a simple versioning system used in ATIS (Automatic Terminal Information Service). ATIS messages contain information about the wheather at the airport, runways in use etc. This information is transmitted on a dedicated radio frequency and repeated in a loop. The ATIS messages are updated frequently as the wheather or operations on the airport change. Every time a new ATIS message is generated, the letter is changed.

Example of an ATIS message:

This is Schiphol arrival information Kilo, main landing runway 18Right. Transition level 50. Two zero zero degrees, one one knots. Visibility 10 kilometres. Few 1300 feet, scattered 1800 feet, broken 2000 feet. Temperature 15, dewpoint 13. QNH 995 hectopascal. No significant change. Contact Approach and Arrival callsign only. End of information Kilo.

Now when for example the temperature or pressure at the airport changes, the ATIS information is updated:

This is Schiphol arrival information Lima, main landing runway 18Right. Transition level 50. Two zero zero degrees, one two knots. Visibility 10 kilometres. Few 1300 feet, scattered 1800 feet, broken 2000 feet. Temperature 16, dewpoint 13. QNH 994 hectopascal. No significant change. Contact Approach and Arrival callsign only. End of information Lima.

The flight crew will listen to the ATIS often before they are in contact with the Air Traffic Control of the airport. They note the information in the ATIS, together with the information version letter.

On first contact with the airport's Air Traffic Control, they will then state what version of the ATIS they have listened to.

Schiphol approach, this is KLM1234 with information Lima.

The Air Traffic Controller can then verify this is the latest version of the ATIS, or if there is newer information available that should be passed on to the flight crew.

share|improve this answer
6  
This was Aviation SE information DeltaLima. –  David Richerby Jul 10 at 9:55
1  
when does it reset? –  ratchet freak Jul 10 at 9:58
2  
@DeltaMike Indeed. –  David Richerby Jul 10 at 10:19
1  
@ratchetfreak FYI Schiphol just went from Lima to Mike and then back to Alfa –  DeltaLima Jul 10 at 10:28
1  
One halloween, just for fun, the local airport was publishing information "Spooky", "Transylvannia", "Undertaker", "Vampire", , etc... I think the pilots enjoyed that little deviation from the regs. :) –  abelenky Jul 10 at 17:01

In the US, ATIS info is typically updated hourly - unless something unusual/unpredicted happens that is relevant to approaching or departing aircraft. In the US, ATIS broadcasts include:

  • Airport Name.
  • Information letter (Alpha, Bravo, Charlie...).
  • Time Hour/Minute in Zulu (GMT) when the observation was made
  • Winds - direction, speed, and sometimes gusts, variability.
  • Sky Condition - cloud cover (clear, few, scattered, broken, overcast) and altitude of the layer(s).
  • Barometric Pressure - which is used to set the aircraft's onboard altimeter to an accurate reference for the airport it's approaching/departing).
  • Other remarks, such as runway/taxiway closures, lighting or navigational aids down, etc.
share|improve this answer

The letters refer to ATIS information, which stands for Automatic Terminal Information Service. ATIS messages are broadcast on a loop on a separate frequency from approach and tower frequencies and inform pilots of weather conditions, active runways, runway conditions, and other important data. Each time the information changes a new recording is made and the version letter increments.

Pilots listen to this information before contacting the approach/tower frequency so that the controllers don't spend their entire day reciting it over and over again.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.