Title: ADS - Validity Indication for Downlink Parameters PDR Reference: 97060004 Originator Reference: A047PD0A SARPs Document Reference: ADS SARPs, Section 2.2.1.4.2.1 Status: ADOPTED PDR Revision Date: 18/08/97 (add "Proposed SARPs amendment") 22/09/97 (SUBMITTED -> ACCEPTED) 06/10/97 (New proposed solution) 20/10/97 (ACCEPTED -> PROPOSED) 29/0/97 (RESOLVED) PDR Submission Date: 27/06/97 Submitting State/Organization: Aérospatiale Submitting Author Name: Monteil, A Populus, F Submitting Author E-mail Address: arnaud.monteil@avions.aerospatiale.fr frederique.populus@avions.aerospatiale.fr Submitting Author Supplemental Contact Information: Mr. Arnaud MONTEIL, A/BTE/SY/GGV B0403, AEROSPATIALE, 316 route de Bayonne, 31060 Toulouse, France Tel: 33 (0) 5 61 18 44 29 Fax: 33 (0) 5 61 93 80 06 Mrs. Frédérique POPULUS, A/BTE/SY/GGV B0403, AEROSPATIALE, 316 route de Bayonne, 31060 Toulouse, France Tel: 33 (0) 5 61 18 44 18 Fax: 33 (0) 5 61 93 80 06 SARPs Date: IV1.1, March 1997 SARPs Language: English Summary of Defect: 1/ What shall be done if a data of an ADS report is temporarily invalid / not available (for any reason in the avionics)? 2/ What shall be done if a contracted ADS event cannot temporarily be detected (for any reason in the avionics)? The following additional clarification has been added by T I Maude (maude@level-7.co.uk). 1/ The ADS SARPs does not cover the case when the information needed for the report is temporarliy unavailable. For example, if a periodic contract requests weather information and, during the operation of the contract, the instrumentation that detects the temperature fails. In this case, the SARPs does not state what should be done. If left unchanged, then different implementations may choose different solutions to this problem - for example, some may send the last available information, some may send a default value, and some may not send the information at all. 2/ The case where the events cannot be detected is already covered by the SARPs (see 2.2.1.7.3.5.14). Assigned SME: Sub-Volume II SME Proposed SARPs amendment: The possible solutions are: 1) Do not send the report at all. This is NOT recommended as it could be safety critical (e.g. an event report) 2) Do not send the information field that is unavailable. This is NOT recommended as not all fields are optional (e.g. position). 3) Send a default value. This is NOT recommended all values are valid in many fields (e.g. heading is 1 to 360 degrees all of which are valid). 4) Abort the connection. This is NOT recommended as it is too drastic an action for what may potentially not be a critical situation. 5) Change the ASN.1 to include validity bits on a field by field basis (as in the solution recommended above. This is possible but gives a large change to the ASN.1 6) Change the ASN.1 to include validity bits on a group by group basis. This changes the ASN.1 - but there is less of a change than solution 5). 7) A combination of more than one of the above. The proposed solution discussed and recommended by ATNP/WG3/SG2 (Columbia meeting) is a combination of the above, and is as follows: Under 2.2.1.7.1.5 Miscellaneous Air User Requirements add: 2.2.1.7.1.5.5 If, after accepting a contract, the ADS-air-user is unable to provide the information required, either because it is unavailable, invalid or because its validity is uncertain, then: a) if the information forms part of position, timestamp or FOM, then: 1) the ADS-air-user shall stop all contracts with the ADS-ground-user, and 2) the ADS-air-user shall invoke ADS-user-abort request, and b) if the information is the aircraft-address, the ADS-air-user shall omit the aircraft-address from any ADS-reports or ADS-emergency-reports that require it, and c) if the information is part of the projected-profile, the ADS-air-user shall omit the projected-profile from any ADS-reports that require it, and d) if the information is part of the ground-vector, the ADS-air-user shall omit the ground-vector from any ADS-reports or ADS-emergency-reports that require it, and e) if the information is part of the air-vector, the ADS-air-user shall omit the air-vector from any ADS-reports that require it, and f) if the information is part of the weather, the ADS-air-user shall omit the weather from any ADS-reports that require it, and g) if the information is part of the short-term-intent, the ADS-air-user shall omit the short-term-intent from any ADS-reports that require it, and h) if the information is part of the extended-projected-profile, the ADS-air-user shall omit the extended-projected-profile from any ADS-reports that require it. <> Note 1.-- If information is not available for more than one optional field, then both are omitted. If information is not available for position, timestamp or FOM as well as one or more optional fields, then the ADS-air-user will abort. <> Note 2.-- The ADS-air-user must be able to detect when information becomes unavailable. The ADS-air-user must be able to detect if the information is invalid, or its validity is uncertain. <> Note 3.-- The ADS-ground-user will know what information is expected in any ADS-report or ADS-emergency-report. It is therefore able to tell when the information is unavailable or possible invalid. Sections 2.2.1.7.2.4.1, 2.2.1.7.3.5.1 to 2.2.1.7.3.5.13, 2.2.1.7.4.4.5 and 2.2.1.7.6.3.5 will be altered to include the caveat "subject to the restrictions stated in 2.2.1.7.1.5.5" SME Recommendation to CCB: RESOLVED CCB Decision: CCB-2(Langen): SUBMITTED atnp_ccb_chair: ACCEPTED (22/09/97) CCB-3: RESOLVED