曝光台 注意防骗
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ATC procedures and the “see and avoid” concept continue to be the primary means of ensuring aircraft separation. However, TCAS adds a significant backup for collision avoidance.
TCAS can display up to 30 aircraft at a time. The system uses range relative bearing, and altitude of the intruder (if reported) to predict the time to and the vertical separation of the intruder at the closest point of approach (CPA). If the system predicts that safe boundaries may be violated, it issues a traffic advisory (TA) to alert the crew. If the intruder continues to close and unsafe separation will occur, a resolution advisory (RA) is issued.
For two TCAS equipped aircraft, the systems coordinate the resolution advisories using the Mode S transponder data links. This ensures complementary advisories are issued in each aircraft. Generation of the alarm is based on a 5 second crew reaction time and a .25 G maneuvering force to achieve adequate separation. Increase or reversal of an RA requires a reaction in 2. seconds with a .35 G maneuvering force.
Symbology and Indication
There are two TCAS displays: the traffic advisory (TA) display (on weather radar), and the resolution advisory (RA) display (on the VSI). The RA indication is incorporated into the VSI with illuminated red and green arcs around the dial indicating the required vertical speed to avoid a possible collision. The TA indications are displayed as four different traffic symbols on the radar PPI indicator. The symbols change shape and color to represent increasing levels of urgency.
The traffic symbols may have an altitude tag, which shows relative altitude in hundreds of feet, and a trend arrow. A plus (+) sign and number above the symbol means the intruder is above your altitude. A minus (-) sign and number below the symbol indicates the intruder is below your altitude. A trend arrow indicates whether the intruder is climbing or descending at a rate of 500 FPM or greater.
If the intruder is non-altitude reporting, the traffic symbol appears without an altitude number or trend arrow. An RA is not generated for non-altitude reporting aircraft since TCAS does not know the intruder’s altitude.
The type of symbol is based on the intruder’s location and closing rate. Should TCAS direction finding techniques fail to locate the azimuth of an aircraft causing a TA or RA, a NO BEARING message appears on the radar.
The presence of TA or RA aircraft that are beyond the selected display range is indicated by one half of the appropriate traffic symbol at the edge of the radar display. The position of the half-symbol represents the bearing of the intruder.
Resolution advisories are grouped as corrective advisories or preventive advisories. Corrective advisories require a positive action by the crew and are accompanied by a green arc on the VSI showing fly-to guidance, plus a red arc on the VSI for the vertical speeds to be avoided.
Preventative advisories require no action be taken to alter the flight path of the aircraft. The vertical speeds to be avoided are indicated by the red arcs. Preventative advisories do not have the green arc fly-to guidance.
An RA may be presented for as many as three threat aircraft simultaneously. For example, a do-not-descend indication may be visible at the same time a do-not-climb indication appears because of threat aircraft above and below your own aircraft.
Synthesized voice announcements are issued by TCAS over the aircraft audio system.
Continental
Rev. 12/01/00 #29 Flight Manual
An open white diamond indicates that an intruder’s relative altitude is greater than plus or minus 1200 feet or its distance is beyond 6 nm range. It is not yet considered a threat.
This one is 1700 feet below your own altitude, climbing at 500 feet per minute or greater.
A filled white diamond indicates that the
intruding aircraft is within plus or minus
1200 feet and within 6 nm range, but is
still not considered a threat.
This intruder is now 1000 feet below your
aircraft and climbing.
A symbol change to a filled yellow circle indicates that the intruding aircraft is considered to be potentially hazardous. Depending on your altitude TCAS will display a TA when the time to CPA is between 35 and 45 seconds.
Here the intruder is 900 feet below your aircraft, climbing at 500 FPM or greater. A voice announcement is heard in the cockpit advising: “TRAFFIC, TRAFFIC.”
Under normal conditions a TA will precede an RA by 15 seconds. The crew should attempt to gain visual contact with the intruder and be prepared to maneuver should an RA be sounded. The crew should take no evasive action based solely on the TCAS display.
A solid red square indicates that the intruding aircraft is projected to be a collision threat. TCAS calculates that the intruder has reached the point where an RA is necessary. The time to closest approach with the intruder is now between 20 and 30 seconds depending on your altitude. The symbol appears together with an appropriate audio warning and a vertical maneuver indication on the RA/VSI.
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