AFTN circuit failure with a runway-closure NOTAM waiting
At 0215 UTC the AFTN circuit linking the KDRX communication centre to the regional COM centre fails; the terminal shows no line sync and repeated retries fail. A backup dial-up link exists but must be established manually by the on-call technician, who will not arrive for 45 minutes. At 0225 an AIS officer telephones from an adjacent unit with a flight-safety NOTAM: the only runway at a neighbouring aerodrome is closed because of a disabled aircraft, effective immediately, and the information must reach all AFTN addressees without delay. The operator's outbound queue already holds one DD message from an airline about a medical-evacuation connection and six routine GG messages. The AIS officer reads the NOTAM text over the telephone and asks the operator to 'just send it as urgent as possible'. The operator must decide how traffic is moved, in what order, and in what form.
1. State the order in which the queued traffic should be transmitted once a path exists, and justify it against the AFTN priority scheme.
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The AFTN priority order is SS (distress) > DD (urgency) > FF (flight safety) > GG (routine), and within a priority the rule is first-in, first-out. Applying it:
- DD medical-evacuation message - urgency, already waiting, and it outranks the NOTAM. It moves first the moment any path opens.
- FF runway-closure NOTAM - flight safety. It must not wait behind the GG backlog, but it does not displace a DD.
- Six GG messages - routine, last, and only as capacity allows.
The temptation is to send the NOTAM first because it feels more dramatic. That is exactly the judgement the priority scheme exists to remove: an operator who promotes messages by personal judgement destroys the predictability that other units rely on. The correct answer is DD then FF, with the NOTAM going within minutes of the DD, not hours later.
One caveat is worth stating: if the DD were later cancelled or downgraded by the originator, the FF NOTAM becomes head of the queue. If the disabled aircraft were still on the runway with traffic inbound and no other unit had warned them, an argument could be made for DD on the NOTAM itself, but that decision belongs to the originator, not the relay operator.
2. Describe how the FF NOTAM is actually moved while the primary circuit is down, and what must be recorded.
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The operator has three levers and should use them in parallel rather than in sequence:
- Service restoration: report the outage to the COM centre's technical control immediately with the time of failure and the symptom (no line sync), and press for the dial-up link to be established - this is the technician's job and the call starts the clock on it.
- Alternate routing: ask the COM centre whether traffic can be relayed through another AFTN station that still has a path, and use that route rather than holding the message.
- Fastest available means: if the NOTAM must move before restoration, pass it by telephone or message link directly to the addressee units entitled to receive it, read back field by field, and obtain an explicit acknowledgement of receipt. Never assume a telephone read-out constitutes delivery without confirmation.
Record in the log: the outage time and symptom; the time the NOTAM was received from the AIS officer and by what means; the priority assigned and why; the transmission route used; the time of each delivery and the name or identifier of the person who acknowledged it; the time the primary circuit was restored and by whom. If the message moves by telephone, the originator must later be told that the AFTN copy went by alternate means so that normal dissemination can be reconciled.
3. The operator drafts the message and is unsure of the addressing. What must an AFTN message of this kind carry, and what should be done if a wrong eight-letter addressee indicator is later discovered?
Read the worked answer
An AFTN message needs, as a minimum: the originator indicator, the priority indicator (here FF), the addressee indicator(s), the filing time in DDHHMM, and the text. For a NOTAM the text must be the complete, unabbreviated NOTAM issued by the originating AIS/NOF, with its series and number, because a relay operator is not authorised to edit NOTAM content.
The originator here is the AIS unit that issued the NOTAM, not the KDRX operator who happens to be relaying it. The operator must not put his own indicator in the originator field to make the message look locally generated - that breaks the audit trail and can cause the message to be rejected or duplicated.
If a wrong eight-letter indicator is discovered after transmission:
- Do not silently amend and re-send. A corrected message that appears to come from the original originator without explanation can be treated as a duplicate or as a forgery.
- Notify the originator immediately and let them decide whether a service message, a correction, or a fresh transmission is appropriate.
- Send a service message to the misaddressed station asking them to disregard the message and to confirm that they have not acted on it.
- Record the error, the recipients affected, the corrective action and the times in the log.
The underlying principle is that a relay station routes and delivers traffic; it does not own it.