While traditional Secondary Surveillance Radar (SSR) stations interrogate all aircraft within their range, Mode S (Select) establishes selective and addressed interrogations with aircraft within its coverage. 这种选择性询问提高了检测的质量和完整性, 识别和高度报告. The Mode S system is a combined secondary surveillance radar (beacon) and ground-air-ground data link system. 该技术可以提高飞机的探测质量, 识别和高度报告信息.
除了, Mode S provides the medium for a digital data link which can be used to exchange information between aircraft and various air traffic control functions and weather databases. 这种技术, 随着未来的改进, ADS-B装备是否会在许多商务飞机上使用. Through the Mode S ‘extended squitter’ function used by ADS-B systems aircraft are able to transmit their position and also report their unique aircraft identity (call sign).
从90年代中期开始, 在欧洲核心空域使用的飞机监视系统已达到最大容量. 以便持续增长, 模式S计划使用模式a /C应答器作为SSR的替代品. 该计划于2009年全面实施. 目前SSR模式有两个级别, 模式S基本监视(ELS), S模式加强监察(EHS).
模式S ELS目前需要在欧洲大部分空域的IFR飞行, 包括:比利时, 法国, 德国, 卢森堡, 荷兰, 瑞士, 意大利, 捷克共和国, 匈牙利和希腊.
One of the key benefits of 模式S船 is the assignment to each aircraft of a unique ICAO 24-bit address by the state of registry. 模式S船 uses this unique 24-bit aircraft address for selective interrogation and to acquire down linked aircraft identification, 即航班标识或飞机呼号. 该技术还允许ATC设备以25英尺的增量获取高度.
最大起飞重量大于12的飞机,566磅(5,700 kg) or a maximum cruise true airspeed greater than 250 knots must be equipped with 模式S EHS to operate in the United Kingdom, 德国和法国.
EHS is intended to provide additional information about an aircraft’s state and intent for use by air traffic controllers. 它包括信息元素(称为下行飞机参数- DAPs). 衣冠楚楚的包括:
This information is designed to offer improved situational awareness for air traffic control while reducing radio congestion. Access by controllers to aircraft intent DAPs allows cross-checking of climb/descent instructions and help the early identification of potential loss of separation incidents.
Eurocontrol has identified certain aircraft that are unable to support the full set of DAPs due to avionics equipage issues. Aircraft that are unable to provide the full set of 8 DAPs are considered to be 模式S EHS non-capable and may be able to obtain an exemption, 如果飞机装备模式S ELS. Exemptions may also be available for aircraft conducting test, delivery or maintenance flights. National Aviation Authorities are now responsible for granting exemptions for each respective country. 参观 欧洲管制模式- s豁免页 的更多信息.