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[1] The alternate ( or auxiliary ) navigation control display unit ( ANCDU ) in its normal function provides the interface between the flight crew and the FMC, and contains circuitry to support this function. The ANCDU contains a keyboard for data entry or for requesting data to be displayed; a cathod ray tube ( CRT) that displays information; a microprocessor that controls the operation of the CDU; a receiver that receives information from the FMC; and circuits that control character generation and display on the CRT. The display format is contained in the FMC .Two ANCDU are installed in the FMCS. The CDUs are physically and functionally identical. Both CDU can be used independently or simultaneously for control and display during a flight. Either CDU may be utilized to enter system data. The basic display format consists of an array of fourteen 24-character lines. A variety of alpha- numeric characters and symbols can be presented on each line under the control of the FMC.
[2] The CDU alpha-numeric keyboard provides the operator with a means of entering data into the system for initialization of the
Fig. 37-1 Alternate Navigation CDU (normal function)
LNAV/ VNAV navigation and guidance modes, and for modification of flight plans . The alpha-numeric key group also includes the special purpose slash (/) , change sign (+/-), decimal point (.), and clear (CLR ) keys. All entries initiated by operation of the alpha-numeric keyboard initially appear in the scratch pad area of the display. The scratch pad content can be edited or cleared by pressing the CLR key. When an entry is present in the scratch pad, a brief depression of the CLR key will clear the last character in the entry. If the CLR key is held down for more than 1 second, the entire entry in the scratch pad wil be cleared. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：第31课 大气数据系统 LESSON 31 AIR DATA SYSTEM(32)
