R Mod : 3832 or 8259
ATR 42 Model : 400/500
TCAS
COMMUNICATIONS
P 4
NOV 01
060
1.05
.
20
20.3 OPERATION
The TCAS provides two levels of threat advisories :
If the traffic gets between 20 and 48 seconds (depending on aircraft altitude) of projected
Closest Point of Approach (CPA), it is then considered an intruder, and an aural and visual
traffic advisory is issued. This level calls attention to a developing collision threat using
the traffic advisory display and the voice message, TRAFFIC TRAFFIC". It permits
mental and physical preparation for a possible maneuver to follow, and assists the pilot in
achieving visual acquisition of the threat aircraft.
If the intruder gets between 15 and 35 seconds (depending on aircraft altitude), of CPA, it
is considered a threat and an aural and visual resolution advisory is issued. This level
provides a recommanded vertical maneuver using modified TCAS VSI's and voice
messages to provide adequate vertical separation from the threat aircraft, or prevents
initiation of a maneuver that would place the TCAS aircraft in jeopardy.
The TCAS resolution advisories are annunciated by the following voice messages, as
appropriate :
"CLIMB, CLIMB, CLIMB"
:
(Climb at the rate depicted by the green (fly to) arc on the TCAS VSI).
DESCEND, DESCEND, DESCEND" :
(Descend at the rate depicted by the green (fly to) arc.).
MONITOR VERTICAL SPEED, MONITOR VERTICAL SPEED" :
(Spoken only once if issued after a previous corrective advisory). Assure that vertical
speed is out of the illuminated TCAS VSI red arc.
REDUCE CLIMB-REDUCE CLIMB" :
(Reduce vertical speed to a value within the illuminated green arc).
CLEAR OF CONFLICT" :
(Range is increasing, and separation is adequate, return to assigned clearance).
CLIMB, CROSSING CLIMB, CLIMB, CROSSING CLIMB" :
(Climb at the rate depicted by the green (fly to) arc on the TCAS VSI). Safe separation
will best be achieved by climbing through the threat's flight path.
REDUCE DESCENT-REDUCE DESCENT" :
(Reduce vertical speed to a value within the illuminated green arc).
DESCEND, CROSSING DESCEND, DESCEND, CROSSING DESCEND" :
(Descend at the rate depicted by the green (fly to) arc or the TCAS VSI) safe
separation will best be achieved by descending through the intruder's flight path.
AA
A
B
C
D
E
F
G
H
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