Title: 	CPDLC -	Adding 3 new messages : WE CAN ACCEPT ... AT [position]
PDR Reference:				M2030001
Originator Reference: 			-
SARPs Document Reference:		-
Status: 				FORWARDED
Impact:					-
PDR Revision Date:			13/03/2002 (ACCEPTED -> FORWARDED)
PDR Submission Date:  			08/03/2002 (SUBMITTED -> ACCEPTED)
					07/02/2002
Submitting State/Organization:		AIRBUS France
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:		-

Addition of new CPDLC messages shall first be agreed by the OPLINKP. ATNP is not the relevant group for the request. The request is however logged in the SGA2 OR repository document for future work in the future.

CCB Decision:				atnp_ccb_chair (O8/03/02): ACCEPTED
					ccb-15 Phuket (13/03/02): FORWARDED