Tercera hipótesis específica

Note 1.— A dependent clearance is a message consisting of more than one clearance element, where the flight crew is required to comply with each of the elements. A rejection of any of the elements, either singly or in combination, renders the entire clearance invalid.

Note 2.— Sending the elements as individual messages may compromise safety or separation if the flight crew accepts the first uplink of a dependent clearance, complies with the instruction, and then responds DM 1 UNABLE to the next message when received.

Note 3.— The flight crew will respond to the multi-element uplink message with either DM 0 WILCO or DM 1 UNABLE, which applies to the entire message, per paragraph 5.3.1.2.

Note 4.— The controller should not send a dependent clearance in a single multi-element uplink message containing the condition THEN. In the following example, the message element UM 165 THEN followed by the route clearance message element UM 74 PROCEED DIRECT TO [position] does not clearly convey that the flight crew needs to complete the climb clearance prior to commencing the route clearance change.

Controller CLIMB TO AND MAINTAIN FL330 THEN

PROCEED DIRECT TO TUNTO

Example 2: The controller sends a single multi-element uplink message containing an amended route clearance that is dependent on a vertical clearance. To eliminate any potential ambiguity, the controller chose the second element to reinforce that the flight crew needs to comply with the vertical clearance prior to complying with the amend route clearance.

Controller UM 20 CLIMB TO FL330 or CLIMB TO AND MAINTAIN FL330 UM 78 AT FL330 PROCEED DIRECT TO TUNTO

UM 129 REPORT MAINTAINING FL330 or REPORT LEVEL FL330.

4.3.7 Weather deviations

Note.— For an ATN-B1 ATSU, message elements supporting weather deviations are not available.

4.3.7.1 When issuing a deviation clearance, the controller should use UM 82 CLEARED TO DEVIATE UP TO [specified distance] [direction] OF ROUTE and append UM 127 REPORT BACK ON ROUTE.

Note.— If a clearance direct to a waypoint is issued before the deviating aircraft has reported back on route, the controller will need to determine the aircraft’s location or continue to protect the airspace affected by the weather deviation clearance until the aircraft sequences the specified waypoint.

4.3.7.2 A weather deviation clearance remains in effect until either:

a) A “back on route” report is received; or

b) The aircraft reaches a subsequent waypoint to which it has been cleared when clear of weather.

4.4 CPDLC – Downlinks

4.4.1 General

4.4.1.1 The ATSU should respond to a downlink message that it does not support according to paragraph 3.1.2.5.3.

4.4.1.2 The ATSU should respond to an incoming request as soon as practicable to avoid the flight crew initiating a duplicate request.

Note.— ATN B1 ground systems provide for automatic timeout of messages that are not responded to, while FANS 1/A ground system messages can remain open indefinitely.

4.4.2 Clarifying a downlink message

4.4.2.1 In the case of a controller having any doubt as to the intent of a downlink message, or if any other ambiguity exists, the controller should seek clarification using CPDLC or voice. The controller should then respond to the downlink message with a CPDLC message consistent with the clarification to prevent confusion and to close the open downlink message.

4.4.3 Responses/acknowledgements

4.4.3.1 The controller should respond to a clearance request by issuing a clearance using an appropriate standard message element, UM 1 STANDBY or UM 0 UNABLE.

4.4.3.2 When a clearance request is denied, the controller should send UM 0 UNABLE and, when practicable, append a reason for the non-availability of the clearance.

Note.— The controller should not restate the aircraft’s current clearance.

4.4.3.3 The controller should send UM 1 STANDBY to provide advice to the flight crew that the requested clearance is being assessed, but is not readily available, for example, due to traffic or delays in coordination with the next sector or ATSU.

Note 1.— Some ATSUs automatically send a UM 1 STANDBY to acknowledge that it received a downlink request (refer to Appendix E).

Note 2.— Some FANS 1/A aircraft may reject the actual response after having received a preliminary UM 1 STANDBY for the downlink request (refer to Appendix F, paragraph F.24).

4.4.3.4 If a UM 1 STANDBY response is sent, the controller should subsequently send another response within a reasonable period of time, or as required to prevent message timeout or flight crew confusion.

Note.— The downlink message remains open. If the controller does not respond within this time, the flight crew may query the controller per paragraph 5.4.1.5.

4.4.3.5 If a duplicate CPDLC request is received prior to having responded to the first request, the controller should send appropriate responses to both of the requests.

Note.— Responding to both requests will close the downlink messages. Depending on the ground system, the closure response for the second request may be:

a) a re-iteration of the response for the first downlink request (e.g. a clearance or UM 0 UNABLE);

or

b) some other uplink message that does not contradict any previous clearance that may have been sent (i.e. avoid sending a clearance to one downlink request and UM 0 UNABLE to the duplicated downlink message)

Example 1:

Dialogue 1 Dialogue 2

Flight crew DM 9 REQUEST CLIMB TO FL370

Flight crew DM 9 REQUEST CLIMB TO FL370

Controller UM 0 UNABLE

Controller UM 0 UNABLE

Example 2:

Dialogue 1 Dialogue 2

Flight crew DM 9 REQUEST CLIMB TO FL370

Flight crew DM 9 REQUEST CLIMB TO FL370

Controller UM 20 CLIMB TO FL370 or CLIMB TO AND MAINTAIN FL370

Controller UM 20 CLIMB TO FL370 or CLIMB TO

AND MAINTAIN FL370; or (for example) UM 169 CLEARANCE ALREADY SENT Flight crew DM 0 WILCO

Flight crew DM 0 WILCO or DM 3 ROGER, as

appropriate

4.4.3.6 If a UM 1 STANDBY message had previously been sent when a duplicated request is received, and additional time is required before the clearance is available, the controller should respond with UM 2 REQUEST DEFERRED, when appropriate.

Example:

Dialogue 1 Dialogue 2

Flight crew DM 9 REQUEST CLIMB TO FL370 Controller UM 1 STANDBY

Flight crew DM 9 REQUEST CLIMB TO FL370

Controller UM 2 REQUEST DEFERRED

Time passes until clearance is available.

Controller UM 20 CLIMB TO FL370 or CLIMB TO AND MAINTAIN FL370

Controller UM 20 CLIMB TO FL370 or CLIMB TO

AND MAINTAIN FL370; or (for example) UM 169 CLEARANCE ALREADY SENT Flight crew DM 0 WILCO

Flight crew DM 0 WILCO

4.4.4 Responding to multi-element requests

4.4.4.1 While it is recommended that the flight crew avoid requests for multiple clearances in a single CPDLC message per paragraph 5.4.1.4, such requests can occur.

4.4.4.2 If the controller receives multiple clearance requests in a single message and can approve all clearance requests, the controller should respond in a single message that includes the appropriate clearance for each request in the message.

Example:

Flight crew DM 9 REQUEST CLIMB TO FL370 DM 22 REQUEST DIRECT TO TUNTO

Controller UM 20 CLIMB TO FL370 or CLIMB TO AND MAINTAIN FL370 UM 74 PROCEED DIRECT TO TUNTO

4.4.4.3 If the controller receives multiple clearance requests in a single message and cannot approve all of the clearance request elements, the controller should send, in a single message, UM 0 UNABLE, which applies to all elements of the original message.

Note 1.— The controller should not restate the aircraft’s current clearance.

Note 2.— The controller should not send a single message containing UM 0 UNABLE for elements of the multiple clearance request that cannot be granted and a clearance for the remaining elements.

Note 3.— The controller may include a reason to remove any ambiguity and, if appropriate, information on when the portions of the clearance request that are available might be expected.

Note 4.— The controller may, following the UM 0 UNABLE [reason] message, send a separate CPDLC message (or messages) to respond to those elements for which they can issue an appropriate clearance.

Example 1:

Flight crew DM 9 REQUEST CLIMB TO FL370 DM 22 REQUEST DIRECT TO TUNTO Controller UM 0 UNABLE

Example 2:

Flight crew DM 9 REQUEST CLIMB TO FL370 DM 22 REQUEST DIRECT TO TUNTO Controller