CAP797 – New FISO Manual

The CAA has recently produced a new manual of Flight Information Services (CAP797) which becomes effective on 1 April 2013. With this new manual, there are some changes to operational procedures used by FISOs that will be applicable to airfields such as Fairoaks operating under a Flight Information Service.

Below is an article from the CAA helping to clarify the different types of services available from UK airfields. Text outlined in bold italics draws attention to changes from the current FISO practice.

Look Who’s Talking

Kevin Crowley, an Air Traffic Standards Specialist at the Civil Aviation Authority takes a look at RT protocol and the importance of good communication. 

Verbal misunderstandings never turn out that well, but in aviation they can be fatal. For a pilot, the difference between an instruction, and the supply of information, can mean the difference between a safe flight, and an incident or accident. As well as understanding what has been said, a pilot should also be aware of who has said it. Is that an Air Traffic Controller (ATCO), Flight Information Service Officer (FISO), or Air Ground Radio Operator you are talking to? Effective communication relies on a two way process, and as well as speaking a common language it helps if both parties are conscious of just who they are communicating with - this determines how a pilot should interpret the language used.  

Many GA pilots, of course, operate quite happily in Class G airspace without needing to talk to anyone at all. However, many do need to use the radio to operate at their local aerodrome, and will receive an Air Traffic Control (ATC) Service, Aerodrome Flight Information Service (AFIS) or Air Ground Communication Service (AGCS). Knowing what to and what not to expect from each service, and the phraseology used in the provision of each service is something any pilot with a Radiotelephony licence will have covered in their training. However, knowledge fades and misconceptions creep in with time.

The UK Civil Aviation Authority (CAA) has recently published a new document, CAP 797 Flight Information Service Officer Manual, containing procedures and phraseology for use by a FISO, and can be found on the CAA website at The manual is the result of an extensive consultation process with the aviation community and will have an impact for operations at all aerodromes providing an AFIS.

Although the new manual is primarily intended for use by FISOs, it makes interesting reading for general aviation pilots as it details the procedures and phraseology which they will encounter when operating at an aerodrome with an AFIS.

Looking at the various levels of service available at aerodromes, they can be identified from the radiotelephony callsign used, as follows:




So what exactly is the difference between ATC, AFIS, and AGCS?


ATC provides instructions and clearances to assist in the prevention of collisions and to expedite and maintain an orderly flow of air traffic. Instructions and clearances from ATC to an aircraft on the ground, and whilst flying within controlled airspace and/or an Aerodrome Traffic Zone in Class G airspace, must be complied with at all times, unless the commander of the aircraft considers it unsafe to do so, in which case you must notify ATC. This includes compliance with the order in which ATC direct aircraft to approach to land and clearances to use the runway for take-off and landing.

If you are unsure of the clearance or instruction which has been passed, you must query it with ATC. Likewise if ATC communicate an order in which aircraft are to approach to land and you cannot see the traffic you are required to fit in behind, you must advise ATC, so that they can update you with the location of other traffic or communicate an alternative plan.

Whilst ATC will provide you with the location of other traffic which may affect your flight, not all aerodromes providing an ATC service will have the benefit of radar to see aircraft, therefore you must keep a good lookout for other aircraft in case they appear in a location which you were not expecting.

At an aerodrome with ATC you will hear the following phraseology when taking-off or landing:

‘Cleared for take-off’ – This is a clearance

‘Cleared to land’ – This is a clearance

 You may also hear:

‘Go around I say again go around acknowledge’ – This is an instruction used when the air traffic controller considers it is not safe for you to continue your approach.


AFIS provides instructions to aircraft only while manoeuvring on the apron, and taxiway up to the holding point, or on completion of the landing roll back to your parking area. These ground instructions may include the use of ‘Hold position’ when you are at the holding point, which you are required to comply with.

In all other circumstances AFIS provides information and advice only, useful for the safe and efficient conduct of flight.

When you have reported ready for departure and the Aerodrome FISO (AFISO) advises you that you may ‘take-off at your discretion’, do not assume it is safe to do so, it is your responsibility to evaluate any traffic information which they have passed and decide if it is safe to take-off. If you decide that this is not the case you must advise the AFISO accordingly and tell him/her that you are ‘holding’.

There may be occasions when you report ready for departure that the AFISO passes you information on relevant aerodrome traffic and requests you to ‘report lined up’ This may occur when an aircraft which has already landed has yet to vacate the runway. You must decide whether it is safe to enter the runway based on the information the AFISO has passed you. If in the example given, you feel there will not be sufficient time for the landed aircraft to vacate the runway and for you to take-off safely before the next landing aircraft you must advise the AFISO accordingly, advising him/her that you are ‘holding’. If you do enter the runway, the AFISO will then inform you either ‘Runway Occupied’ or ‘Take-off at your discretion’ when you report lined up, depending on the circumstances.

In the case of landing when you are advised ‘land at your discretion’, the AFISO is advising you that they do not know of any other traffic to affect your landing, but you must still decide if it is safe to do so whilst keeping a good lookout for any other traffic which may appear. Remember that the Rules of the Air do not permit two landing aircraft to be on the runway at the same time at an aerodrome providing AFIS or AGCS.

AFISOs are not permitted to instruct you to execute a go around and therefore you must make this decision if the landing area is occupied, or it is not safe to land for some other reason, advising the AFISO accordingly that you are executing a go  around. Bearing this in mind, there may be an occasion where having passed ‘land at your discretion’ the AFISO receives a request from an agency requiring an emergency crossing of the runway, such as the aerodrome fire service attending an incident on the aerodrome. In such circumstances the AFISO will assess your distance from touchdown and may if they feel it is safe to do so, advise you ‘runway occupied’ and receive an acknowledgement from you before allowing the vehicle to cross the runway. Once the vehicle has crossed the runway and provided it is safe to do so they will advise you ‘Land at your discretion’. If at any time you consider it is not safe to continue your approach, it is your responsibility to execute a go-around and advise the AFISO accordingly.

In relation to backtracking a runway, an AFISO may instruct you to do so by use of the phraseology ‘Backtrack’ when you will be utilising the runway for taxiing. However when you have reported ready for departure, but require a backtrack because you  are entering the runway at an intersection, the phraseology will be ‘At your discretion backtrack’. In the latter case you must assess the information which the AFISO has passed you on other aerodrome traffic and decide if there is sufficient time for you to safely backtrack the runway for departure, taking into account the next landing aircraft. If there is not then advise the AFISO accordingly, telling him/her that you are 'holding’.

When you are airborne and operating in the vicinity of the aerodrome, whether  joining, leaving or operating in the aerodrome traffic pattern, the AFISO will provide you with information on other known aircraft operating in the vicinity of the aerodrome. An AFISO does not have a radar display so the information provided will be based on what he has been told by pilots; therefore you must keep a good lookout. You should also keep a good lookout for aircraft which may not have called the aerodrome and which the AFISO is therefore not aware of. It is important therefore when passing your own position, to be as accurate as possible as this will assist the AFISO and other aircraft in the vicinity to visually acquire your aircraft.

Pilots are responsible for safe integration with other aerodrome traffic and are required by the Rules of the Air to conform to the established traffic pattern. An overhead join may help in this respect, allowing you more time to visually acquire and integrate with other aerodrome traffic, but remember to check local procedures before getting airborne because local conditions such as airspace restrictions and other activities at the aerodrome may mean that another joining procedure is more appropriate.

Remember therefore, at an aerodrome with an AFIS you will hear the following phraseology when taking-off or landing:

‘Take-off at your discretion’ – This is advice and is not a clearance, you must decide if it is safe to do so

‘Land at your discretion’ –  This is advice and is not a clearance, you must decide if it is safe to do so


No instructions should ever be given by AGCS. The service only provides information to assist a pilot in safe conduct of his/her flight. Information provided on other traffic will be based on pilot reports and so a good lookout should be maintained both on the ground and in the air. Also bear in mind that AGCS operators often do not have a full and complete view of the aerodrome surface or its local airspace.

In summary, it is important that pilots are familiar with the services provided at aerodromes, that they assume responsibility for the safety of their flight, and at all times display good judgement and airmanship.

To further help pilots communicate effectively, the CAA also publishes a comprehensive reference guide to radiotelephony phraseology, CAP 413, which is available at It covers phrases to be used when arriving at and departing from aerodromes, flying cross country, operating at unattended aerodromes, carrying out instrument approaches and relaying emergency messages.