15 AirTraffic Services
15.19 Clearance Read-back. Flight crews are required to ‘read back’ to the air traffic controller, safety related parts of ATC clearances and instructions which are communicated by voice. The following items must always be read back:
•ATC route clearances
•Clearance relating to the use of runways (i.e. land, take off, cross, enter and back-track, hold short of)
•Runway in use; altimeter settings; SSR codes; level instructions; heading and speed instructions; transition levels
15.20 Air Traffic Flow Management (ATFM). Using modern data processing systems and prior flight planning, especially using repetitive flight plans (RPLs), it is now possible to predict traffic loading in each sector of the route structure of the airspace within an FIR. Where this exceeds that which can normally be accommodated, the ATFM unit in the ACC will advise flight crews and operators that delays are likely or that restrictions may be applied. Such information is disseminated generally so that operators can see that any disruption is incurred equitably. In practice, predictable delays are handled by delaying the take-off of an aeroplane such that the delay is absorbed on the ground rather than in the terminal phase of a flight. Clearly, this has economic, environmental and safety advantages and is the most obvious practical advantage of ATFM.
Control of Persons and Vehicles at Aerodromes
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15.21 |
Rules of the Air. The movement of persons or vehicles including towed aircraft on the |
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manoeuvring area of an aerodrome is to be controlled by the aerodrome control tower as |
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necessary to avoid hazards to them or to aircraft landing, taxiing or taking off. |
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15.22 |
Low Visibility Procedures. When Low Visibility Operations are in force (ground |
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visibility below 800 m) persons and vehicles operating on the manoeuvring area will be kept to |
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a minimum. Special procedures will be implemented to safeguard the ILS/MLS sensitive areas |
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when CAT II and CAT III precision instrument operations are in progress (ground visibility less |
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than 550 m). |
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15.23 |
Emergency Vehicles. Emergency vehicles proceeding to the scene of an accident or |
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incident will have priority over all other surface movement traffic. |
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15.24 |
Vehicles on the Manoeuvring Area. The following rules cover the movement of |
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vehicles on the manoeuvring area of an aerodrome:
• Vehicles and vehicles towing aircraft are to give way to aircraft that are landing, taxiing or taking off.
• Vehicles are to give way to vehicles towing aircraft.
• Vehicles will give way to other vehicles in accordance with ATS unit instructions.
• Notwithstanding the above, vehicles and vehicles towing aircraft are to comply with instructions issued by the aerodrome control tower.
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The Flight Information Service
15.25Introduction. As already stated, the basic unit of airspace within a state is the Flight Information Region (FIR). In theory, an FIR can exists without CAS, in which case the only services provided to air traffic would be a flight information service (FIS) and the alerting service. Even where ATC is provided inside CAS, FIS will be provided although at a lower priority to ATC. The provision of any service relies on a regular flow of information and the provision of FIS relies heavily on the Aeronautical Information Service (AIS) established by each state in accordance with Annex 15. AIS is covered in Chapter 18 of these notes.
15.26FISOs. Outside of CAS and at uncontrolled aerodromes, flight information is provided by Flight Information Service Officers (FISOs) operating from a Flight Information Centre (FIC). Where a FIS is provided the name of the office providing the service will be suffixed ‘information.’ FISOs are licensed to provide the service but are not permitted to offer any service that can be described as ATC. The only exception to this is the provision of ATC to aircraft taxiing on the ground at a controlled aerodrome but this is strictly limited to movements prior to entering the runway for take-off. The FIS provided in the London FIR is by ‘London Information’ in three geographic sectors on dedicated VHF frequencies.
15.27Operation. Flight Information is provided to all air traffic that is likely to be affected by the information. Specifically:
•Aircraft which are provided with an ATC service;
•Aircraft which are otherwise known to the relevant ATS units.
The information provided by the FIS is to include:
•SIGMET and AIRMET (see definition below);
•Volcanic eruption activity;
•Release of radioactive or toxic material into the atmosphere;
•Information concerning change of serviceability of radio navigation aids;
•Information concerning change of conditions concerning aerodromes;
•Information concerning unmanned free balloons;
•Other information considered pertinent to safety.
Additionally, information is to be provided concerning:
•Weather conditions reported or forecast at departure, destination or alternate aerodromes;
•Collision hazards to aircraft operating in classes C, D, E, F and G airspace;
•For flights over sea areas (when requested by pilots), details of surface vessels.
Apart from the delivery of FIS on discrete VHF frequencies, the majority of ‘routine’ FIS is broadcast by the Operational Flight Information Service (OFIS).
15.28 AIRMET. According to Annex 11, AIRMET is defined as:
‘Information concerning the occurrence or expected occurrence of specified en route weather phenomena which may affect the safety of low-level aircraft operations and which was not already included in the forecast issued for low-level flights in the FIR concerned or sub-area thereof.’
Air Traffic Services 15
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Services Traffic Air 15
15.29 SIGMET. According to Annex 11, AIRMET is defined as:
‘Information issued by a meteorological watch office concerning the occurrence or expected occurrence of specified en route weather phenomena which may affect the safety of aircraft operations.’
15.30 OFIS. OFIS is broadcast in three specific areas:
•HF OFIS
•VHF OFIS
•ATIS
Both HF OFIS and VHF OFIS broadcast VOLMET (METAR, SIGMET and TAF) information for specific aerodromes (or groups of aerodromes) in accordance with a schedule. The table below shows the VHF OFIS Volmet coverage in the London, Scottish and Shannon FIRs.
Location |
Frequency |
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Airports covered |
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London Main |
135.375 |
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Amsterdam, Brussels, Dublin, Glasgow, London LGW, |
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London LHR, London STN, Manchester, Paris CDG |
London North |
126.6 |
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Blackpool, East Midlands, Leeds Bradford, Liverpool, |
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London LGW, Manchester, Newcastle, Isle of Man, |
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Teeside |
London South |
128.6 |
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Birmingham, Bournemouth, Bristol, Cardiff, Jersey, |
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Luton, Norwich, Southampton, Southend |
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Scottish |
125.725 |
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Aberdeen, Belfast BFS, Edinburgh, Glasgow, Inverness, |
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London LHR, Prestwick, Stornoway, Sumburgh |
Dublin |
127.0 |
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Dublin, Shannon, Cork, Belfast BFS, Glasgow, Prestwick, |
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Manchester, London LHR, London LGW |
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Figure 15.1 Volmet broadcasts |
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HF OFIS Volmet is broadcast by the Oceanic Control Centres (e.g. Shanwick) and covers the aerodromes used by transiting traffic.
15.31ATIS. Automatic Terminal Information Service broadcasts (ATIS) consist of two types of broadcast: Voice ATIS and Data ATIS. The preparation and dissemination of ATIS is the responsibility of ATS.
15.32Voice ATIS. This is provided at aerodromes where there is a requirement to reduce voice channel communications. ATIS broadcasts comprise:
•One broadcast serving arriving aircraft; or
•One broadcast serving departing aircraft; or
•One broadcast serving both arriving and departing aircraft; or
•Two broadcasts serving arriving or departing aircraft where one broadcast would be exceptionally long.
15.33 Transmission. Voice ATIS is usually transmitted on a discrete VHF frequency (displayed on all aerodrome plates). It may be transmitted on the voice channel of a relevant VOR (e.g. departure ATIS on the VOR used as the primary VOR for a SID; or arrival ATIS on the VOR that serves as the IAF for a procedure). ATIS is never transmitted on the voice channel of ILS. Voice ATIS is continuous and repetitive.
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15.34 ATIS Information. ATIS information normally relates to a single aerodrome and the broadcast should not last longer than 30 seconds. It is updated immediately any significant change occurs. ATS is responsible for making sure that the service is available and up to date. Each sequence of ATIS broadcasts will have a specific sequential broadcast designator letter. On initial contact with ATC, aircraft are to acknowledge receipt of the relevant ATIS with reference to the current information designator.
“Oxford Tower G-ABCD bay 27, information Charlie, QNH 1003 request start”
15.35Cloud Information. The ATIS broadcast will only include cloud cover when the cloud base is below 5000 ft or the highest MSA (whichever is higher), or when cumulonimbus cloud is present.
15.36Acknowledgment of a Non-current ATIS. Should an aircraft acknowledge an ATIS that is no longer current, any element of information that needs up-dating shall be transmitted to the aircraft by the ATCU without delay.
The Alerting Service
15.37 Introduction. Within an FIR, the provision of service to aircraft requesting assistance or |
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indicating that they may require assistance is the responsibility of the Alerting Service of ATS. |
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This service is provided by any ATS unit (ACC, ATCU, FIC etc…) regardless of the type of service |
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normally offered. The Alerting Service is the link between the aircraft needing assistance, and |
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the services that can provide that assistance. Where necessary, the provision of a service to |
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aircraft in need of assistance will have priority over all other air traffic services. |
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15.38 Application. The Alerting Service is provided to: |
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• All aircraft provided with ATC; |
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• As far as practicable, all aircraft that have filed a FP or are otherwise known to ATC, and |
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• Any aircraft known (or believed to be) the subject of unlawful interference. |
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FICs and ACCs will serve as the central point for collecting all information relevant to an aircraft |
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state of emergency, and forwarding such information to the appropriate rescue co-ordination |
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centre (RCC). If an emergency arises when an aircraft is under the control of the aerodrome or |
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approach controller, that office will notify the ACC or FIC which in turn will notify the RCC. If |
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the urgency of the situation dictates, the aerodrome or approach office will set in motion all |
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necessary local emergency organizations that can give immediate assistance. |
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15.39 Communication of Information. Where it is established by an ATS unit that an aircraft |
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is in a state of emergency in the vicinity of other aircraft, the ATS unit will inform the other |
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aircraft of the nature of the emergency as soon as possible. If an aircraft is being subjected |
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to unlawful interference, no reference will be made in ATC communications unless it has been |
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referred to in communications from the aircraft in the first place, and such communication will |
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not make the situation worse. |
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