CPDLC Route Uplink Options for Oceanic Clearances or Track Change
CPDLC Route Uplinks
· UM 79 CLEARED TO [position] VIA [route clearance]
· UM 80 CLEARED [route clearance]
· UM 83 AT [position] CLEARED [route clearance]
CPDLC Route Uplinks ATSU Concerns
· Routing to destination
· Route discontinuities
· Loss of Wx data (winds and temperature)
CPDLC Route Uplink Options (Flight on Original Flight Plan)
ELSIR / 50N050W / 50N040W / 50N030W / 50N020W / SOMAX / ATSUR / LND / Original Routingw------w ------w ------w ------w ------w ------w ------w ------w ------w
UM 79 CLEARED TO LND VIA ELSIR 50N050W 50N040W 50N030W 50N020W SOMAX ATSUR
· Routing to destination
· No discontinuity
· Loss of Wx data on track only
UM 80 CLEARED ELSIR 50N050W 50N040W 50N030W 50N020W SOMAX ATSUR LND Original Routing
· ATSU will have to “append” original routing
· No discontinuity
· Loss of all Wx data
CPDLC Route Uplink Options (Track Change)
Original
ELSIR / 50N050W / 50N040W / 50N030W / 50N020W / SOMAX / ATSUR / LND / Original Routingw------w ------w ------w ------w ------w ------w ------w ------w ------w
New
JOOPY / 49N050W / 49N040W / 49N030W / 49N020W / BEDRA / NERTUw------w ------w ------w ------w ------w ------w ----
UM 79 CLEARED TO LND VIA JOOPY 49N050W 49N040W 49N030W 49N020W BEDRA NERTU
JOOPY / 49N050W / 49N040W / 49N030W / 49N020W / BEDRA / NERTU / LND / Original Routingw------w ------w ------w ------w ------w ------w ------w ------w ------w
To avoid a route discontinuity, the uplink can be “anchored” to the first significant point after the original track exit point; in this case LND.
· Routing to destination
· No discontinuity
· Loss of Wx data for track only
CPDLC Route Uplinks Pros and Cons
Pros
· Replace ACARS 623 Oceanic Clearances
· Eliminates flight crew “typing”
· All Oceanic Clearances whether the original filed or a track change are loaded directly into the FMS
· Better ATC assurance that the FMS is loaded with the proper waypoints
· UM 137 CONFIRM ASSIGNED ROUTE could be integrated into conformance monitoring and provide immediate information as to whether the cleared route is loaded in the FMS.
· ADS-C helps mitigate loss of some or all Wx data
Cons
· ANSPs will need to develop procedures for “appending original routing” and the use of a significant waypoint after track exit
· Procedures would have to be implemented to allow route uplinks to be potentially sent from a preceding ATSU
· Loss of some or all Wx data
· UM 137 CONFIRM ASSIGNED ROUTE can only be used with operators using full Lat/Long
· ARINC 424 operators would receive uplink in a full Lat/Long format and would need to understand the importance of waypoint verification procedures
Summary
The use of CPDLC route uplinks (specifically UM 79 in the event of a track change) can significantly help in eliminating ALL track errors, half degree or whole. Issues on how to “construct” it and “when and how” to send it need more discussion amongst the ANSPs. Any track change should include flight crew and ATC procedures to verify routing after track exit. The loss of Wx data can easily be mitigated by using information on the original flight plan or receipt from AOC via data link; ADS-C could also help.
The expanded discussion below was offered in a WP presented by Gordon Sandell at CNSG/5. It was used as a source document for the information provided above.
NORTH ATLANTIC COMMUNICATIONS, SURVEILLANCE AND NAVIGATION GROUP
(NAT CNSG)
FIFTH MEETING
(Bodo, Norway, 26-30 September 2011)
Agenda Item 5: Planning and implementation
b) Use of CPDLC for oceanic route re-clearances to destination without discontinuities
Loading of Route Clearances
(Presented by United States of America)
Summary
This paper provides an overview of how route loading to the FMC occurs when using the various uplink messages containing the [routeclearance] parameter.
1 Introduction
1.1 The NAT CNSG intends to provide recommendations to stakeholders, on which uplink messages should be used to send route clearances to airplanes, so that they can be loaded appropriately.
1.2 In order to be able to provide such a recommendation, it is necessary to understand how such clearances are loaded by the airplane avionics systems, and how this may differ between airplane and equipment manufacturers. The purpose of this paper is to provide that guidance..
2 Discussion
2.1 The FANS-1/A message set includes four uplink messages that contain the [routeclearance] parameter. One of those is um73 (pre departure clearance), which is not relevant to oceanic operation. There is also an uplink for EXPECT [routeclearance], but that is not loadable. The loadable route clearance uplinks of interest are therefore:
Um79 CLEARED TO [position] VIA [routeclearance]
Um80 CLEARED [routeclearance]
Um83 AT [position] CLEARED [routeclearance]
2.2 Um79, when loaded into the Flight Management System, will replace the entire flight plan, as far as the waypoint identified by the [position] parameter. This is shown in the diagram below.
2.3 If the terminating fix (JKLMN in the example) does not exist in the active route, then the resulting flight plan will consist of the uplinked route, the terminating fix, a flight plan discontinuity, and then the entire existing flight plan. This is shown in the figure below.
2.4 Um80 will replace the entire flight plan route, as shown in the figure below.
2.5 Um83 is implemented differently by different airplane/equipment manufacturers. The basic implementation is the same. The route is replaced after the specified position. This is shown in the figure below.
2.6 In the case of Boeing airplanes, the entire route from that point on is replaced. On Airbus airplanes, if the final fix in the route exists in the existing flight plan, then the route from that point on is retained. These two different approaches are shown in the figure below.
2.7 If the specified [position] does not exist in the flight plan, then the entire uplinked route is appended to the current route, with a flight plan discontinuity between them. This is shown in the figure below.
2.8 Flight can discontinuities can also result when a fix or airway in the uplink cannot be found in the airplane’s navigation database, or if the terminal area procedures do not include appropriate transitions.
3 Action by the meeting
3.1 The Group is invited to consider the information contained in this paper in determining the best approach for uplinking route clearances.