Shanwick and Gander OCA News

Gander and Edmonton SATCOMVoice

SATVOICE is not a replacement for ADS-C, CPDLC, VHF, or HF communications. SATCOMVoice can be used as a means of reducing the risk during a communications failure, improving the safety of operations, and alleviating HF congestion.

In the Edmonton FIR, SATVOICE calls should be made directly to the ZEG SATVOICE number. In the Gander Domestic and Oceanic FIRs, SATVOICE calls should be made to Gander international flight service station (IFSS) except in urgent situations, when the call can be made directly to the appropriate air traffic control (ATC) unit. Refer to the table below for the updated short and long codes for SATVOICE services provided by Edmonton and Gander FIRs.

Inmarsat satellite coverage has limitations in the north so flights operating only with Inmarsat equipment may experience unreliability north of 72N. There is no Inmarsat satellite coverage north of 80N.Iridium SATVOICE services are available north of 80N.

Operators of aircraft that are equipped with both Inmarsat and Iridium modems should ensure that they switch to the Iridium system before operating north of 72N.

Operators should ensure the following is contained in the flight plan for aircraft capable of both Air-to-Ground and Ground-to-Air SATVOICE calling:

In item#10A, as appropriate insert:

− “M1” for ATC RTF INMARSAT capability and/or

− “M3” for ATC RTF IRIDIUM capability; and

In Item #18, insert:

− the indicator REG/ followed by the aircraft registration; and

− the indicator CODE/ followed by the aircraft address expressed in the form of  an alphanumerical code of six hexadecimal characters.

Shanwick Message Latency Timer

The intention of the message latency monitor function is to prevent pilots from acting on a CPDLC uplink message that has been delayed in the network. The most serious of such cases would be the pilot executing a clearance that was no longer valid.

There are variations between aircraft types. Because aircraft implementations are varied, it is impossible for ATC to tailor the uplink of the message “SET MAX UPLINK DELAY VALUE TO 300 SEC” to different aircraft types. It has therefore been decided by the NAT ATC providers to uplink this message to all CPDLC connected aircraft immediately after they enter each control area. An aircraft crossing several different FIR/OCA’s may receive this message multiple times during a flight.

NAT ATC has discontinued the CPDLC message “THIS IS AN AUTOMATED MESSAGE TO CONFIRM CPDLC CONTACT WITH SHANWICK CENTER” upon entry and has replaced this with “SET MAX UPLINK DELAY VALUE TO 300 SEC”. 

This new message will therefore serve two purposes. One, to prompt the pilot to set the specified uplink delay value in the aircraft avionics and two, establish the Current DATA authority (CDA) for ATC.

Pilots will need be familiar with their individual aircraft latency timer functions, (AUTO, MANUAL or TIMER NOT AVAIABLE).

When the pilot receives the uplink CPDLC message “SET MAX UPLINK DELAY VALUE TO 300 SEC”, the pilot is expected to send a positive response to ATC as prompted by the avionics (ACCEPT [ROGER]) regardless of whether the aircraft supports the latency tier or not. If AUTO, the timer will be set by the avionics. If MANUAL, the pilot will need to take action to set the timer to the direct value. If TIMER NOT AVAIABLE, this needs to be sent via freetext.