时间：2011-04-18 00:50来源：蓝天飞行翻译 作者：航空 点击：次
|
(c)The intruder altitude is 700 feet less than or below the client aircraft, indicated by the “.07” located under the symbol. (d)The intruder is descending >500 fpm, indicated by the downward arrow next to the “.07” relative altitude information. The absence of this arrow when an altitude tag is present indicates level flight or a climb/descent rate less than 500 fpm. NOTE. If the intruder did not have an operating altitude encoder (Mode C), the altitude and altitude trend “tags” would have been omitted. d. Limitations 1.TIS is NOT intended to be used as a collision avoidance system and does not relieve the pilot responsibility to “see and avoid” other aircraft (see paragraph 5.5.8, See and Avoid). TIS shall not be for avoidance maneuvers during IMC or other times when there is no visual contact with the intruder aircraft. TIS is intended only to assist in visual acquisition of other aircraft in VMC. No recom-mended avoidance maneuvers are provided for, nor authorized, as a direct result of a TIS intruder display or TIS alert. 2.While TIS is a useful aid to visual traffic avoidance, it has some system limitations that must be fully understood to ensure proper use. Many of these limitations are inherent in secondary radar surveillance. In other words, the information provided by TIS will be no better than that provided to ATC. Other limitations and anomalies are associated with the TIS predictive algorithm. (a)Intruder Display Limitations. TIS will only display aircraft with operating transponders installed. TIS relies on surveillance of the Mode S radar, which is a “secondary surveillance” radar similar to the ATCRBS described in para-graph 4.5.2. (b)TIS Client Altitude Reporting Require-ment. Altitude reporting is required by the TIS client aircraft in order to receive TIS. If the altitude encoder is inoperative or disabled, TIS will be unavailable, as TIS requests will not be honored by the ground system. As such, TIS requires altitude reporting to determine the Proximity Coverage Volume as 4.5.12 Surveillance Systems indicated in FIG 4.5.4. TIS users must be alert to altitude encoder malfunctions, as TIS has no mechanism to determine if client altitude reporting is correct. A failure of this nature will cause erroneous and possibly unpredictable TIS operation. If this malfunction is suspected, confirmation of altitude reporting with ATC is suggested. (c)Intruder Altitude Reporting. Intruders without altitude reporting capability will be dis-played without the accompanying altitude tag. Additionally, nonaltitude reporting intruders are assumed to be at the same altitude as the TIS client for alert computations. This helps to ensure that the pilot will be alerted to all traffic under radar coverage, but the actual altitude difference may be substantial. Therefore, visual acquisition may be difficult in this instance. (d)Coverage Limitations. Since TIS is provided by ground.based, secondary surveillance radar, it is subject to all limitations of that radar. If an aircraft is not detected by the radar, it cannot be displayed on TIS. Examples of these limitations are as follows: (1)TIS will typically be provided within 55 NM of the radars depicted in FIG 4.5.5, Terminal Mode S Radar Sites. This maximum range can vary by radar site and is always subject to “line of sight” limitations; the radar and data link signals will be blocked by obstructions, terrain, and curvature of the earth. (2)TIS will be unavailable at low altitudes in many areas of the country, particularly in mountainous regions. Also, when flying near the “floor” of radar coverage in a particular area, intruders below the client aircraft may not be detected by TIS. (3)TIS will be temporarily disrupted when flying directly over the radar site providing coverage if no adjacent site assumes the service. A ground.based radar, like a VOR or NDB, has a zenith cone, sometimes referred to as the cone of confusion or cone of silence. This is the area of ambiguity directly above the station where bearing information is unreliable. The zenith cone setting for TIS is 34 degrees: Any aircraft above that angle with respect to the radar horizon will lose TIS coverage from that radar until it is below this 34 degree angle. The aircraft may not actually lose service in areas of AIM multiple radar coverage since an adjacent radar will provide TIS. If no other TIS.capable radar is available, the “Good.bye” message will be received and TIS terminated until coverage is resumed. (e)Intermittent Operations. TIS operation may be intermittent during turns or other maneuver-ing, particularly if the transponder system does not include antenna diversity (antenna mounted on the top and bottom of the aircraft). As in (d) above, TIS is dependent on two.way, “line of sight” communica-tions between the aircraft and the Mode S radar. Whenever the structure of the client aircraft comes between the transponder antenna (usually located on the underside of the aircraft) and the ground.based radar antenna, the signal may be temporarily interrupted. (f)TIS Predictive Algorithm. TIS informa-tion is collected one radar scan prior to the scan during which the uplink occurs. Therefore, the surveillance information is approximately 5 seconds old. In order to present the intruders in a “real time” position, TIS uses a “predictive algorithm” in its tracking software. This algorithm uses track history data to extrapolate intruders to their expected positions consistent with the time of display in the cockpit. Occasionally, aircraft maneuvering will cause this algorithm to induce errors in the TIS display. These errors primarily affect relative bearing information; intruder distance and altitude will remain relatively accurate and may be used to assist in “see and avoid.” Some of the more common examples of these errors are as follows: |
