range - X (DMOD) to the power two TAU = ----------with X = ---------
range rate range This formula represents an estimate of the time the aircraft would take to penetrate a sphere around the intruder with a radius equal to (DMOD)expnt2/range. The DMOD coefficients are in function of altitude, ranging from 0.20 NM for 1000-2350ft, to 1.1 NM above 20,000 ft as shown below:
Altitude DMOD (ft) (NM) 0-1000
1000-2350 0.20 2350-5000 0.35 5000-10000 0.55 10000-20000 0.80 20000-42000 1.10 above 42000 1.10
R **ON A/C 001-049, 051-061, 101-149, 201-299, 301-399, 401-499,
E. Definition of Target Aircraft Target aircraft are divided into four categories: OTHER - PROXIMATE -TRAFFIC ADVISORY (TA) RESOLUTION ADVISORY (RA).
NOTE : Since the Display Management Computers (DMC) do not sort the OTHER
____ intruders, the latter are not presented on the NDs. Their presentation is optional. It is activated by pin programming and replacement of ATC/TCAS control unit (ALL TRAFFIC configuration).
R 1EFF : 001-049, 051-061, 101-149, 201-299, 1 34-43-00Page 75 1301-399, 401-499, 1Aug 01/05 1 1 1CES 1
(1)
Other traffic (optional) Aircraft detected by the TCAS are defined as OTHER traffic if:
-they are within + or - 2700 ft vertically of own aircraft
-and if they do not enter in the PROXIMATE, TA or RA categories. These targets are represented by a white diamond, outline only, on the ND.
(2)
Proximate aircraft Targets are defined as proximate traffic if the difference between their altitude and that of the TCAS aircraft is less than 1200 ft and if their range is within 6 NM. Their presentation on the ND is conditioned by the presence of another TA or RA intruder (THREAT TRAFFIC function). Generally aircraft not in the immediate vicinity enter into this category. Depending on their trajectory, they may:
-conserve this status and move away without an advisory being declared. In this case the pilot is informed of their presence on the ND by a white filled diamond symbol and can monitor their progress, or
-have a trajectory liable to lead to a conflict situation and in this case they require a traffic advisory and their symbol changes.
(3)
Traffic advisory aircraft
(Ref. Fig. 022) When an intruder is relatively near but does not represent an immediate threat the TCAS issues a traffic advisory. Its presence is displayed on the ND by an amber filled circle. Its display is accompanied by an aural alert: "Traffic Traffic". The pilot is therefore aware of its presence and knows its range and relative bearing. Its display is linked to vertical separation and time TAU before CPA values. Depending on its trajectory, an intruder may conserve this status and move away, or it may become a collision threat. In this case avoidance maneuvers are suggested to the pilot via a resolution advisory.
(4)
Resolution advisory aircraft
(Ref. Fig. 022) In resolution displays, the intruder is represented on the ND by a red filled square and corrective orders are issued on the vertical speed scale of the PFD. Crossing into resolution advisory occurs for a TAU time threshold 10 to 15 seconds lower than a traffic advisory threshold.
R 1EFF : 001-049, 051-061, 101-149, 201-299, 1 34-43-00Page 76 1301-399, 401-499, 1Aug 01/05 1 1 1CES 1
TCAS - Threat Threshold Scale Figure 022
R 1EFF : 1 1 1CES ALL 1 111 34-43-00 Page 77 May 01/05
Vertical separation between the two aircraft is also taken into account for this category. There are two types of resolution advisory, in function of the vertical separation value:
-Preventive Advisories
-Corrective Advisories.
(a)
Preventive Advisory In this case the vertical separation is less than a threshold S1 and greater than a threshold S2. The advisory instructs the pilot to avoid certain deviations from current vertical rate, this measure being sufficient to avoid a risk of collision. On the PFD speed scale, the forbidden values are indicated by red sectors.
(b)
Corrective advisory In this case, the vertical separation is lower than the threshold S2. On the vertical speed scale of the PFD, colored sectors depict avoidance maneuvers to be performed:
-red sector = forbidden vertical speeds
-green "fly to" sector = a vertical speed range to be respected.
(Ref. Fig. 022)
R **ON A/C 001-049, 051-099, 101-105, 151-199,
R Post SB 34-1177 For A/C 001-049,101-105,
E. Definition of Target Aircraft Target aircraft are divided into four categories: OTHER - PROXIMATE -TRAFFIC ADVISORY (TA) RESOLUTION ADVISORY (RA).
NOTE : Since the Display Management Computers (DMC) do not sort the OTHER
____ intruders, the latter are not presented on the NDs. Their presentation is optional. It is activated by pin programming and replacement of ATC/TCAS control unit (ALL TRAFFIC configuration).
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