Doc 9863. Edition 2
Corrigendum No. 3
(English and Russian)
30/11/17
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Doc 9863 Second Edition Corrigendum No. 3 English and Russian 30/11/17 AIRBORNE COLLISION AVOIDANCE SYSTEM ACAS MANUAL CORRIGENDUM No. 3 1. Please replace the existing pages 3-68 and 3-69 by the attached new pages bearing the notation Corr. 3, dated 30/11/17. 2. Record the entry of this corrigendum on page iii of the manual.
Chapter 3. Functions and capabilities 3-67 the RA is a vertical speed limit RA requiring a limit of 0 m/s 0 ft/min and own altitude rate exceeds 7.6 m/s 1 500 ft/min. 3.15.14.4 Strength selection for non-crossing RAs against ACAS-equipped threats. In a conflict with an ACAS-equipped threat, in which the reference logic would normally generate a non-crossing climb or descend RA that is opposite in direction to own aircrafts existing vertical rate, an RA to limit the vertical rate to 0 ft/min will be generated instead, if the following conditions are met a own aircraft and the threat are converging vertically b own aircrafts vertical rate exceeds lo c the threat aircrafts vertical rate is less than lo and d the vertical separation that would be achieved at CPA if both aircraft were to level off exceeds losep. 3.15.14.4.1 The vertical speed limit 0 ft/min RA generated in accordance with 3.15.14.4 is retained if neither aircraft accelerates vertically toward the other with a change in rate in excess of l. Otherwise, the reference logic will immediately generate a climb or descend RA as appropriate for the RA sense. 3.15.14.4.2 The value 5.1 m/s 1 000 ft/min is used for lo. The value 244 m 800 ft is used for losep. 3.16 ACAS II USE OF HYBRID SURVEILLANCE TECHNIQUES Note. The RTCA DO-300A Change 1 contains the MOPS on hybrid surveillance. 3.16.1 Hybrid surveillance is the technique used by ACAS to take advantage of passive position information available via extended squitter to reduce the number of active interrogations required. There are two different modes of hybrid surveillance the extended hybrid surveillance mode and the hybrid surveillance mode. 3.16.1.1 The extended hybrid surveillance mode is used when the intruder is not a near threat in altitude and range, ADS-B position data have a sufficient level of quality, and signal strength is lower than a defined extended hybrid surveillance MTL. In this mode, there is no ACAS active interrogation. 3.16.1.2 When hybrid surveillance mode is used, the intruder is also not a near threat in altitude and range, but the ADS-B traffic own aircraft data do not have a sufficient level of quality, or, the received signal indicates that the aircraft is in close proximity. In this mode, a first validation of the ADS-B data is performed, followed by revalidation of the hybrid surveillance track with an ACAS active interrogation at different time intervals every 10 to 60 seconds. 3.16.1.3 ACAS validates the position provided by extended squitter through direct active range measurement extended squitter data failing this test are not used. If an intruder becomes a near threat in range and in altitude, ACAS transitions to active surveillance, whether it was tracked in extended hybrid surveillance or in hybrid surveillance mode. 3.16.1.4 In active surveillance mode, regular once-per-second active surveillance is performed on intruders. In this manner, passive surveillance can be used for non-threatening intruders, thus lowering the ACAS interrogation rate. Active surveillance is used whenever an intruder becomes a near threat. A track under active surveillance cannot transit to extended hybrid surveillance without first being validated in hybrid surveillance mode, except when the aircraft is on the airport surface. A block diagram of the transitions between the different modes of ACAS extended hybrid surveillance for own aircraft taking off/airborne is presented in Figure 3-12. 15/9/17 Amdt. 1
3-68 Airborne Collision Avoidance System ACAS Manual 3.16.2 The altitude recorded in the extended squitter position report is loaded within the Mode S transponder from the same source used to provide the altitude reported in the reply to an ACAS addressed interrogation. Figure 3-12. Transition between the different modes of ACAS extended hybrid surveillance own aircraft taking off/airborne Active Extended hybrid Hybrid Range AND altitude hybrid threat criteria met ORfailedvalidationDO3002.2.6.1 Range AND altitude hybrid threat criteria met DO-300 2.2.6.1.4 If not qualified for extended hybrid surveillance Standard active acquisition is used Not within range OR altitude of modified hybrid threat criteria DO-300 2.2.7.1.2 AND validated signal Extended hybrid surv MTL OR traffic / own data quality fails Traffic / own data quality good AND signal extended hybrid surv MTL Acquired through exclusive use of ADS-B IF traffic / own data quality good AND signal extended hybrid surv MTL 15/9/17 Amdt. 1 30/11/17Corr. 3
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