ci sono decine di AIC in vigore. Ne cito uno del 2006:
Callsign Confusion
1. Introduction
1.1 It has been noted that there has been an increase in the number of occurrences involving RTF callsign confusion between two or more aircraft having the same or similar flight numbers. Such events may give rise to potential and actual flight safety incidents.
1.2 RTF callsign confusion can occur when:
a) different airlines operate services with the same flight number;
b) within a short period of time an airline operates a number of services with near- sequential or similar flight numbers (more than 50% of same digits);
c) within a short period of time a company operates an extra or delayed service with a flight number very similar to the normal service’s flight number.
1.3 There have also been a number of cases where ATC instructions have been misinterpreted because airlines use flight numbers that are the same as commonly used flight levels or radar headings.
2. Advice to Airlines
2.1 Airlines should review their flight numbering system and assign different flight numbers to services where currently there are similar flight numbers that could lead to RTF callsign confusion.
2.2 Airlines should allocate flight numbers :
a) on a more random basis to avoid bunching of similar or sequential callsigns; e.g. allocating the first service of the day from 0 or 1 and subsequent services of the day with 2 or 3 and so on.
b) not ending with ‘0’ or ‘5’ in the range ‘005’ to ‘360’ to avoid confusion with ATC radar headings;
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c) not ending with ‘0’ for flight numbers in the range ‘110’ to ‘400’ to avoid misunderstandings with ATC flight levels;
d) not using a current flight number and adding another digit either in front or at the end as the flight number of an extra sector service.
2.3 Airlines should avoid using flight numbers with multiple use of the same digit, e.g. ABC 888.
2.4 Airlines should co-ordinate with the Airport Scheduling Committee on the flight numbers preferably before a service received approvals from all appropriate authorities so as to minimize operating the service with callsign similar to an incumbent carrier and thus a possible risk of callsign confusion.
2.5 When, due to operational or commercial reasons, two consecutive sectors of a service, e.g. Bangkok to Hong Kong and Hong Kong to Anchorage, are operated by two aircraft and their SETA and SETD are close to each other, different flight numbers should be used.
3. Advice to Flight Crew
3.1 If an ATC instruction is not clearly understood by the flight crew member responsible for the RTF, or if there is any doubt concerning the instruction, the flight crew member must request ATC to repeat the message. Seeking confirmation directly rather than consulting other crew member(s) is the rational course of action. Do not execute the clearance prior to confirmation.
3.2 Use correct RTF phraseology and procedure at all times. All messages must be prefixed with the airline callsign and flight number.
3.3 Use headsets during periods of high cockpit workload, e.g. take off, climb, descent and landing etc; and actively monitor ATC transmissions and compliance with them, particularly when some flight crew members are carrying out other tasks and rendering them not able to monitor the RTF.
3.4 Ensure the complete RTF message is transmitted and that the beginning and end of the message are not clipped.
3.5 Advise ATC when an ATC transmission is blocked by another transmission or if it is suspected that another aircraft has misinterpreted an instruction. ATC may be unaware of this fact.
3.6 Request ATC to repeat any unexpected instructions during any stage of the flight.
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4. Advice to Controllers
4.1 The similarity of some aircraft callsigns on the same frequency can cause confusion which may lead to an incident. Controllers are to warn pilots concerned and, if necessary, instruct one or both aircraft to use alternative callsigns, e.g. registration mark/number, while they are on the frequency.
4.2 Observe correct RTF discipline at all times.
4.3 Do not clip transmissions.
4.4 Do not use readback time to execute other tasks.
4.5 Ensure clearances are readback correctly.
4.6 Exercise particular caution when language difficulties may exist.
4.7 Always use headsets especially during periods of high workload and/or RTF load and actively monitor flight crew transmissions and their compliance with RTF callsign use.
4.8 Advise adjacent sectors/Area Control Centres if it is felt that potential confusion may exist between aircraft likely to enter their airspaces.
