近地警告系统

• Terrain display.
EGPWS: Look-ahead Terrain Alerting
➢The EGPWS provides caution-and–warning-level alerts to the flight crew about potential terrain conflicts earlier than basic GPWS. ➢The alerts are based primarily on the airplane position and barometric altitude information passed to the EGPWS. Either a flight management system (FMS) or global positioning system (GPS) can provide airplane position (latitude and longitude) to the EGPWS. ➢The look-ahead distance varies mainly with ground speed, The look-ahead caution alert is provided approximately 40 to 60 seconds before a potential terrain conflict, and the look-ahead warning alert is provided approximately 20 to 30 seconds before such a conflict. ➢The altitude offset is normally 700 feet (213m) below the airplane. The purpose of the offset is to provide terrain alerting when the airplane has less than the normal terrain clearance.
❖ EGPWS corrects this problem by integrating an aircraft navigational source into the system. GPS position in conjunction with a terrain database is used to help predict terrain conflict.
❖ 如果EGPWS认为飞机的航迹在某处与地 形太近，它会提前一分钟以上发出音频 和视频告警信号。
❖ 当EGPWS系统发出告警时，在飞行仪表 上将用彩色固定方块来加以强调，表示 会引发危险的地形，同时还伴随有相应 的音响告警。
❖ 固定的红色方块表示地形处在30秒的飞 行时间范围内，要求机组立即执行避开 地形机动程序；而固定的黄色方块则表 示地形处在大约30到60秒的飞行时间范 围内，要求机组立即检查飞行轨迹按需 修正，并执行相应地形机动程序。
如何发出警告
❖ EGPWS可以向机组提供警戒或警告信息。 当前飞行状况导致EGPWS警戒或警告启 动时，无论机组是否选择，地形图将强 制性的自动显示在飞行仪表上。
❖ 在EGPWS中，计算机沿着飞机的预定航 迹连续搜索地形数据库，这样可使系统 具有虚拟的前视能力。若飞机正在下降， 计算机会沿下滑航迹进行搜索；若飞机 正在转弯，则沿转弯航迹搜索。
❖ Mode 3: Altitude Loss After Takeoff(在航机起飞（Takeoff）或 重飞（Go around）爬升时航机高度值过度下降(Altitude loss))。 （"DON'T SINK"）
❖ Honeywe11公司在原有GPWS基础上，开发出新型增强型近 地警告计算机系统，该系统不仅增加了警告时间，还提供 非常直观的地形显示，方便机组发现潜在的危险地形状况， 避免 CFIT事故的发生。
HOW IT WORKS
❖ GPWS是当航机在异常接近地障的状况下,使用语音,灯号以及在萤幕显 示警告文字来警告飞行员.这套系统只有在RA(Radio Altitude)2450 尺以下才会作用启动.
❖ The heart of the GPWS is a computer processor which which can analyze the data from: ▪ Radar altimeter（雷达高度计） ▪ Air data computer（大气数据计算机） ▪ UHF Nav receiver（Ultra-high frequency导航接收机） ▪ Gear and flap indicating system（起落架和襟翼指示系统） ▪ Roll attitude input sensor（滚动姿态输入传感器）
Enhanced GPWS Features
In addition to retaining current GPWS alerting functions, the EGPWS offers two new major features :
• Look-ahead terrain alerting.
EGPWS: Terrain Display
➢To reduce clutter on the display, any terrain more than 2,000 feet (610m) below the airplane is not displayed, and instead remains the background color of black. ➢Because the terrain colors are displayed relative to the current airplane altitude, the colors will change as the airplane climbs or descends. ➢In those areas of the world for which the EGPWS terrain database does not yet contain terrain data, a dotted magenta pattern will show on the display.
❖ The computer analyzes a number of parameters including aircraft configuration, speed, proximity to terrain, and descent rate in order to issue appropriate warnings.
近地警告系统 （GPWS）
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CFIT（可控飞行撞地）
❖ CFIT: Controlled flight into terrain. 为民航两大 主要航空事故之一（ALA： Approach and Landing）， 为一架飞机由机师正常控制，但因为一些失误而撞上地 面、阻碍物或水面坠毁。
❖ 根据国际民航组织的统计，可控飞行撞地是加装GPWS之 前商用喷气飞机机体损毁事故和人员死亡事故的元凶。 1974年，FAA开始对在美国空域飞行的航班上的GPWS进行 强制安装要求（Honeywell），此后CFIT事故急剧减少。 1985年后，CFIT事故每年仅发生1到2次，而强制要求安 装前每年发生7到8次。目前，全球几乎所有的商用喷气 飞机均装备GPWS。
❖ GPWS is a system developed to help prevent CFIT accidents.
GPWS
❖ 定义：地面迫近警告系统（GPWS, Ground Proximity Warning System），又称近地警告系统， 是防止飞机因为离地过近而发生 事故的系统，与TCAS搭配成为保 护飞航安全的两大防线。
Operation mode
❖ Mode 1: Excessive Descent Rate(过度的下降速率)。（"SINK RATE" "PULL UP"）
❖ Mode 2: Excessive Closure to Terrain(过度的地障接近率)。 （"TERRAIN...TERRAIN" "PULL UP"）
--dotted red: 2,000 feet (610m) above the airplane altitude --dotted amber: from 500 feet (152m) below the current airplane altitude to 2,000 feet (610m) above --dotted green: 500 feet (152m) below
❖ 原理：GPWS在起飞开始到降落地 面为止，持续监视飞机离地高度， 利用无线电高度表获得离地高度， 并且以电脑计算出飞机的飞行趋 势，若有危险时会以视觉与语音 警告飞行员采取避险措施。
EGPWS
❖ Enhanced Ground Proximity Warning Systems (EGPWS), also called Terrain Awareness Warning Systems (TAWS).
Reference altitude
Peak display
The following image illustrates the Peaks display at a low relative altitude.
The following image illustrates the Peaks display at a high relative altitude.
❖ A limitation of GPWS is the fact that with radar altimeter information the aircraft is only capable of seeing terrain directly below. In the case of rapidly rising terrain it may not react quick enough to issue a warning in time.