Publication: Magyar Közlöny
Issue: MK-2009-104 (Year: 2009, Number: 104)
Era: 2004-2010
Section: 
Paragraph Index: 2354

(3) The variables in these inequalities shall be defined as follows: it = number of interrogations (Mode A/C and Mode S) transmitted in a 1 s interrogation cycle; Annex 10 — Aeronautical Telecommunications Volume IV 22/11/07 4-8 i = index number for Mode A/C and Mode S interrogations, i = 1, 2,..., it; α = the minimum of α 1 calculated as 1/4 [nb/nc] subject to the special conditions given below and α 2 calculated as Log10 [na/nb] / Log10 25, where nb and nc are defined as the number of operating ACAS II and ACAS III equipped aircraft (airborne or on the ground) within 11.2 km (6 NM) and 5.6 km (3 NM) respectively, of own ACAS (based on ACAS surveillance). ACAS aircraft operating at or below a radio altitude of 610 m (2 000 ft) AGL shall include both airborne and on-ground ACAS II and ACAS III aircraft in the value for nb and nc. Otherwise, ACAS shall include only airborne ACAS II and ACAS III aircraft in the value for nb and nc. The value of a is further constrained to a minimum of 0.5 and a maximum of 1.0. In addition; IF [(nb ≤ 1) OR (nb > 4nc) OR (nb ≤ 4 AND nc ≤ 2 AND na > 25)] THEN α1 = 1.0, IF [(nc > 2) AND (nb > 2 nc ) AND (na < 40)] THEN α1 = 0.5; p(i) = peak power radiated from the antenna in all directions of the pulse having the largest amplitude in the group of pulses comprising a single interrogation during the ith interrogation in a 1 s interrogation cycle, W; m(i) = duration of the mutual suppression interval for own transponder associated with the ith interrogation in a 1 s interrogation cycle, s; B = beam sharpening factor (ratio of 3 dB beam width to beamwidth resulting from interrogation side-lobe suppression). For ACAS interrogators that employ transmitter side-lobe suppression (SLS), the appropriate beamwidth shall be the extent in azimuth angle of the Mode A/C replies from one transponder as limited by SLS, averaged over the transponder population; { } see 4.2.3.3.3 Pa(k) " k " kt " na " Note.— RA and ACAS broadcasts (4.3.6.2.1 and 4.3.7.1.2.4) are interrogations. 4.3.2.2.2.2.1 Transmissions during RAs. All air-to-air coordination interrogations and RA and ACAS broadcasts shall be transmitted at full power and these interrogations shall be excluded from the summations of Mode S interrogations in the left-hand terms of inequalities (1) and (2) in 4.3.2.2.2.2 for the duration of the RA. 4.3.2.2.2.2.2 Transmissions from ACAS units on the ground. Whenever the ACAS aircraft indicates that it is on the ground, ACAS interrogations shall be limited by setting the number of other ACAS II and III aircraft (na) count in the interference limiting inequalities to a value that is three times the value obtained based on ACAS broadcasts received with a transponder receiver threshold of –74 dBm. Whenever Mode A/C interrogation power is reduced because of interference limiting, the Mode A/C interrogation power in the forward beam shall be reduced first until the forward sequence matches the right and left sequences. The forward, right and left interrogation powers shall then sequentially be reduced until they match the rear interrogation power. Further reduction of Mode A/C power shall be accomplished by sequentially reducing the forward, side and rear interrogation powers. 4.3.2.2.2.2.3 Transmissions from ACAS units above 5 490 m (18 000 ft) altitude. Each ACAS interrogator operating above a pressure-altitude of 5 490 m (18 000 ft) shall control its interrogation rate or power or both such that inequalities (1) and (3) in 4.3.2.2.2.2 remain true when na and a are equal to 1, except as provided in 4.3.2.2.2.2.1. Chapter 4 Annex 10 — Aeronautical Telecommunications 4-9 22/11/07 4.3.3 Traffic advisories (TAs) 4.3.3.1 TA function. ACAS shall provide TAs to alert the flight crew to potential threats. Such TAs shall be accompanied by an indication of the approximate relative position of potential threats. 4.3.3.2 PROXIMATE TRAFFIC DISPLAY Recommendation.— While any RA and/or TA are displayed, proximate traffic within 11 km (6 NM) range and, if altitude reporting, ±370 m (1 200 ft) altitude should be displayed. This proximate traffic should be distinguished (e.g. by colour or symbol type) from threats and potential threats, which should be more prominently displayed. 4.3.3.3 TAs as RA precursors. The criteria for TAs shall be such that they are satisfied before those for an RA. 4.3.3.3.1 TA warning time. For intruders reporting altitude, the nominal TA warning time shall not be greater than (T+20 s) where T is the nominal warning time for the generation of the resolution advisory. Note.— Ideally, RAs would always be preceded by a TA but this is not always possible, e.g. the RA criteria might be already satisfied when a track is first established, or a sudden and sharp manoeuvre by the intruder could cause the TA lead time to be less than a cycle. 4.3.4 Threat detection 4.3.4.1 Declaration of threat. ACAS shall evaluate appropriate characteristics of each intruder to determine whether or not it is a threat. 4.3.4.1.1 Intruder characteristics. As a minimum, the characteristics of an intruder that are used to identify a threat shall include:

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