Air Traffic Services — Page 282, Lesson 367

Right, let's pick this up with the ATIS broadcast itself. We've covered what ATIS is, so now we're looking at the specific rules that govern the information it carries. First, the timing and scope. ATIS information normally relates to a single aerodrome, and the broadcast should not last longer than 30 seconds. That's a hard limit on the recording length. It's updated immediately any significant change occurs, and the ATS — the Air Traffic Service — is responsible for making sure the service is available and up to date. Now, the designator. Each sequence of ATIS broadcasts will have a specific sequential broadcast designator letter. So the first broadcast of the day is Alpha, the next is Bravo, then Charlie, and so on. This letter is crucial because it tells everyone which version of the information is current. On initial contact with ATC, aircraft are to acknowledge receipt of the relevant ATIS with reference to the current information designator. So you don't just say "information received" — you state the letter. The example in the text is: "Oxford Tower G-ABCD bay 27, information Charlie, QNH 1003 request start." You can see the pilot is quoting the designator, "Charlie," and the QNH, which is the altimeter setting, all in that first call. Next, cloud information. The ATIS broadcast will only include cloud cover when the cloud base is below 5000 ft, or the highest MSA — that's the Minimum Sector Altitude — whichever is higher. So if the cloud base is above 5000 feet, it's not included unless the MSA is higher than that. And there's one more condition: cloud cover is also included when cumulonimbus cloud is present. Cumulonimbus is the thunderstorm cloud, and its presence is always significant enough to broadcast. Now, what happens if an aircraft acknowledges an ATIS that is no longer current? This is the non-current ATIS situation. Should that happen, any element of information that needs up-dating shall be transmitted to the aircraft by the ATCU — that's the Air Traffic Control Unit — without delay. So the controller must immediately pass the new, correct information to that aircraft. Let's move on to a new service now: the Alerting Service. Within an FIR — a Flight Information Region — the provision of service to aircraft requesting assistance, or indicating that they may require assistance, is the responsibility of the Alerting Service of ATS. This service is provided by any ATS unit — that includes the ACC, the Area Control Centre; the ATCU, the Air Traffic Control Unit; the FIC, the Flight Information Centre, and so on — regardless of the type of service normally offered. The Alerting Service is the link between the aircraft needing assistance and the services that can provide that assistance. And here's a key priority: where necessary, the provision of a service to aircraft in need of assistance will have priority over all other air traffic services. Now, who gets the Alerting Service? It's provided to three categories. First, all aircraft provided with ATC. Second, as far as practicable, all aircraft that have filed a FP — that's a Flight Plan — or are otherwise known to ATC. And third, any aircraft known, or believed to be, the subject of unlawful interference. The FICs and ACCs will serve as the central point for collecting all information relevant to an aircraft state of emergency, and forwarding that information to the appropriate rescue co-ordination centre, the RCC. Now, if an emergency arises when an aircraft is under the control of the aerodrome or approach controller, that office will notify the ACC or FIC, which in turn will notify the RCC. But if the urgency of the situation dictates, the aerodrome or approach office will set in motion all necessary local emergency organizations that can give immediate assistance. So there's a chain of notification, but local action can be taken directly if time is critical. Finally, communication of information. Where it is established by an ATS unit that an aircraft is in a state of emergency in the vicinity of other aircraft, the ATS unit will inform the other aircraft of the nature of the emergency as soon as possible. But there's a very specific rule for unlawful interference. If an aircraft is being subjected to unlawful interference, no reference will be made in ATC communications unless it has been referred to in communications from the aircraft in the first place. And even then, such communication will not make the situation worse. So the controller cannot broadcast that an aircraft is being hijacked unless the aircraft itself has already mentioned it, and even then, only if it won't worsen the situation.