Title: ADS - Error in Tables 2.2.1.5-31 and 32
     
PDR Reference:                    	98030001 
Originator Reference:			-
SARPs Document Reference:          	ADS SARPs, Tables 2.2.1.5-31 and 32 
Status:                          	RESOLVED
Impact:					C (Clarification)
PDR Revision Date:               	25/06/98 (PROPOSED -> RESOLVED)	
						25/05/98 (ACCEPTED -> PROPOSED)
						13/03/98 (SUBMITTED -> ACCEPTED)
						04/03/98 (SUBMITTED)
Submitting State/Organization:  	CENA - DGAC 
Submitting Author Name:           	Jean, M
Submitting Author E-mail Address:	jean@cenatls.cena.dgac.fr
Submitting Author Supplemental
Contact Information:
SARPs Date:                 		IV2.2, Rio 
SARPs Language:                    	English
     
Summary of Defect:

Upon receipt of an ADS-cancel-contract-PDU, the air EC module shall invoke an ADS-cancel indication with the contract type parameter set to the value "event-contract" and create an ADS-positive-acknowledgement-PDU with the Request type APDU-element set to the value "cancel-event-contract".

Tables 2.2.1.5-31 and 2.2.1.5-32 specify the two values in the reverse order.

If implemented as described in the SARPs, any attempt to cancel an event contract causes the abort of the dialogue and all pending ADS contracts by the ADS-ground-ASE. The ADS-air-user receives an ADS-provider-abort indication with abort reason "invalid-PDU". 

Impact on Interoperability:
None.

Impact on Safety:

Presenting an abort to the pilot - algthough all procedures have been correctly followed - could be potentially dangerous and distracting. The pilot has to figure out in that particular case (reception of an ADS-cancel indication followed by an ADS-abort indication) that the abort is (probably) a false alarm.
          
Assigned SME:                    		Sub-Volume II SME

Proposed SARPs amendment:

1/ Change Table 2.2.1.5-31 from:
Contract type	| cancel-event-contract

to:
Contract type	| event-contract
 
2/ Change Table 2.2.1.5-32 from
Request type      | event-contract

to:
Request type      | cancel-event-contract
    

SME Recommendation to CCB:          	
     
CCB Decision:              	CCB-5 (Rio): ACCEPTED
					atnp_ccb_chair: PROPOSED (25/05/98)
					CCB-6 (Utrecht): RESOLVED