AFN Flashcards
How may an AFN logon be initiated?
Manually by the pilot during an initial logon or following a failed datalink transfer; OR
By an ATSU using the address-forwarding process
What is the purpose of a CPDLC connection and how many connections may an aircraft have at any one time?
An aircraft can have up to two CPDLC connections at any one time. The active CPDLC connection is held by the ATSU responsible for the control of the flight. The ATSU and the aircraft can exchange CPDLC messages.
MATSOS states Controllers should manage CPDLC connections to ensure a certain requirement is met. What is this requirement?
To ensure that the ATSU with control for the flight holds the active CPDLC connection.
Describe what is meant by the terms active and inactive CPDLC connections? What are these connections referred to as?
The active connection - CPDLC messages can be exchanged with the aircraft. Current Data Authority.
The inactive connection - CPDLC messages cannot be exchanged with the aircraft. Next Data Authority
Describe the effect of sending a CPDLC message to an aircraft when the ATSU has an inactive connection.
The aircraft system rejects the message and sends DM 63 NOT CURRENT DATA AUTHORITY to the ATSU.
Explain the purpose of the Next Data Authority (NDA) message? Why must the NDA be the first step in the CPDLC transfer sequence?
The NDA message shall be sent prior the the Contact Advisory message to avoid a rejection of the Connection Request from the next controlling ATSU. The aircraft avionics must receive the NDA prior to receiving a connection request message otherwise the connection request will be rejected.
Describe how the aircraft system deals with the receipt of multiple NDA messages and its effect on ATSU CPDLC connections. What is the interesting point to note?
The aircraft system will replace the original NDA message with the new NDA message unless the facility designation in the message is the same as the facility designation already held by the aircraft system. If the facility designation is different, the aircraft will terminate any inactive CPDLC connection that an ATSU may have already established.
When should pilots perform the initial AFN logon?
Prior to takeoff, where permitted or required - no earlier than 45 minutes prior to ETD
15 minutes or more prior to FIR boundary estimate - above 10,000feet
Less than 15 minutes prior to the FIR boundary estimate - above 10,000feet
Following an unsuccessful datalink transfer to another ATSU - when detected by the flight crew or upon receipt of instruction by ATC.
Assuming an aircraft has active and inactive CPDLC connections, under normal conditions how does the aircraft respond to an END SERVICE message and what effect does this have on the respective CPDLC connections?
In response to a Termination Request message:
*The aircraft system will downlink a Termination Confirmation (DISCONNECT) message.
- the aircraft system considers the aircraft to be disconnected as soon as the Termination Confirmation message is sent.
*The Current connection is terminated. This activates the inactive connection.
*The subsequent ATSU is then able to exchange CPDLC messages with the aircraft.
The success of the CPDLC transfer depends on the next ATSU establishing an inactive CPDLC connection prior to the Termination Request message being received by the aircraft.
Which field(s) and indicator(s) does OCS use to identify the datalink and ADS capabilities of an aircraft?
- Field 10a - indicators J1 to J7 as applicable to indicate datalink capability
- Field 10b - indicator D1 or G1 to indicate ADS capability
When should the MONITOR/CONTACT instructions and END SERVICE message normally be sent?
Monitor/Contact information is sent automatically by OCS prior to the END SERVICE. Must be sent as separate UPlink messages. The END SERVICE messages are normally sent 3 minutes prior to the FIR boundary which allows the next ATSU’s connection to be active when the aircraft crosses the boundary. The Transfer of Voice communications message should be sent after receipt of the last position report but not less than 5 minutes prior to the FIR boundary.
What actions should a Controller take on becoming aware that the END SERVICE message was not delivered or fails to trigger a disconnection?
Send another END SERVICE message. If this is also unsuccessful, the pilot shall be instructed to terminate the CPDLC connection and logon to the next unit.
When are free text messages permitted to be used?
When an appropriate standard message element does not exist.
If a CPDLC dialogue is interrupted by a system shutdown, what process shall be followed?
The entire dialogue shall be recommenced by voice communication.
How shall controllers respond to a downlinked Clearance Request that must be denied due to conflicting traffic?
The Controller shall use the element “UNABLE (not NEGATIVE) followed by the reason in the uplink response. The aircraft’s current clearance shall not be re-stated. A free text may be used to add supplementary information.
