Title: 		Adding 3 new messages : WE CAN ACCEPT ... AT [position]

PDR Reference:

Originator Reference: 			US-SV4-02-02

SARPs Document Reference:		Predicates p4, p5, p6

Status: 					SUBMITTED

Impact:

PDR Revision Date:

PDR Submission Date:  			07/03/2002

Submitting State/Organization:	USA

Submitting Author Name: 		Stephane Marche

Submitting Author E-mail Address: 	stephane.marche@airbus.aeromatra.com

Submitting Author Supplemental Contact Information:
	
SARPs Date: 				Edition 3

SARPs Language:  				English

Summary of Defect:

When using the FANS/A, crews are sometimes inclined to respond WE CAN ACCEPT [level] AT [position] to an uplink message WHEN CAN YOU ACCEPT [level] (uM148). There is no corresponding message in CPDLC SARPS (ICAO doc 9705 definition).
The only matching affirmative response available is WE CAN ACCEPT [level] AT [time] (dM81).
In response to the message WHEN CAN YOU ACCEPT [speed] (uM151),
there are situations where crews would like to respond WE CAN ACCEPT [speed] AT [position].
There is no corresponding message in the CPDLC SARPS message set.
In response to the message WHEN CAN YOU ACCEPT [specifiedDistance] [direction] (uM152),
there are situations where crews would like to respond WE CAN ACCEPT [specifiedDistance] [direction] AT [position].
There is no corresponding message in the CPDLC SARPS message set.

The presence of message element um149 CAN YOU ACCEPT [level] AT [position] shows that the combination of altitude and position has been considered for the uplink.
For pilots it is also often easier to refer to a published waypoint of the route rather than refering to an absolute time. To provide the time, they must search for the estimated time at a given waypoint.
Some could argue that a response to a “WHEN CAN YOU” message should be expressed as a [time] value for semantic reasons. But pilots insist on the fact that they must be allowed to provide a position in the response.
Note : This subject will also be raised at Oplink.

Assigned SME:  				SV2 SME

Proposed SARPs amendment:

It is proposed to add three messages to the CPDLC message set in order to cover these operational needs.

Message Element                                              | URG  | ALRT | RESP |
-----------------------------------------------------------------------------------
WE CAN ACCEPT [level] AT [position]                          |  L   |  L   |  N   | 
WE CAN ACCEPT [speed] AT [position]                          |  L   |  L   |  N   |
WE CAN ACCEPT [specifiedDistance] [direction] AT [position]  |  L   |  L   |  N   |

Impact on Interoperability:


PDR Validation Status:


SME Recommendation to CCB:


CCB Decision: