FMC—FMCS系统及相关故障汇总

FMCS系统原理

1、737NG/MAX飞机与FMCS交联的子系统如下：

(1) Airline Communication and Reporting System (ACARS) (option)

(2) Air Data Inertial Reference System (ADIRS)

(3) Air Data Inertial Reference Unit (ADIRU)

(4) Air Data Computer (ADC)

(5) Autopilot/Flight Director System (AFDS)

(6) Autothrottle (A/T)

(7) Common Display System (CDS)

(8) Common Display System Display Electronics Unit (DEU)

(9) FMC Source Select Switch (Dual FMC Installations)

(10) MAX Display Processing Computers (DPC)

(11) Fuel Quantity Indicator System (FQIS)

(12) Global Positioning System (GPS) (option)

(13) GMT Clock

(14) Mode Control Panel (MCP)

(15) MAX Display System (MDS)

(16) Multi−Mode Radio (MMR)

(17) Printer (option)

2、FMCS构型（FMC、MCDU和FANS MCDU（Future Air Navigation System））：

3、MCDU指示：MCDU显示面板有5个指示EXEC，DSPY/CALL, FAIL, MSG和OFST。

4、Source Select Switch (Dual Installations Only)

（1）NAV Master

Regardless of the type of airplane (Classics or NGs) the system is installed in, when the FMC Source Select Switch is in NORMAL or BOTH ON L position, the left FMC (FMC−L) is the navigation master and and the primary. The right FMC (FMC−R) is the secondary.When the FMC Source Select Switch is in BOTH ON R, FMC−R becomes the navigation master and FMC−L becomes the secondary.

During flight, both FMCs compute a navigation solution simultaneously. The primary FMC picks Navaids from the available Navaid list for itself and assigns Navaids to the secondary FMC. The two navigation solutions are continuously being compared. When the solutions are too far apart, the NAV master instructs the follower to perform a restart and recompute the navigation solution. This is allowed to happen three consecutive times before the primary FMC declares the follower FMC failed and drops to single mode.Under these conditions the FMCS display unit will have displayed the message SINGLE FMC OPERATION in the scratch pad.

This action does not necessarily indicate a failed FMC. This means the FMC solutions differed by more than the allowable tolerance. This could be caused by bad data from other FMS sources.

（2）Sub−System Interfaces

The FMC Source Select Switch also determines which FMC communicates with which sub−systems.

(a) FMC Source Select Switch is in the NORMAL position.

All left side sub−systems interface with the left FMC.

All right side sub−systems interface with the right FMC.

The Data Loader, ACARS MU, and both CDUs interface with the left FMC.

(b) FMC Source Select Switch is in the BOTH ON L position.

All sub−systems interface with the left FMC.

The Data Loader, ACARS MU, and both CDUs interface with the left FMC.

(c) FMC Source Select Switch is in the BOTH ON R position.

All sub−systems interface with the right FMC.

The Data Loader, ACARS MU, and both CDUs interface with the right FMC.

5、FMC软件检查：

You must install the software options database for the FMC to operate. If you did not install a software options database the CDU will show DEFAULT050 below SW OPTIONS.

You must install the model/engine database for the FMC to operate. If INVALID shows on the CDU, the model/engine database was not installed. If PROGRAM PIN NOT IN MODEL/ENGINE DATABSE shows, the model/engine database installed does not match the airframe/engine program pin configuration.

FMC不匹配或单FMC工作

1、FMC MISMATCH和SINGLE FMC OPERATION：

2、FMC MISMACH条件：

OFPs不是相同的版本（或一个FMC没有安装）

数据库不相同（或一个FMC没有安装）

飞机构型离散输入不匹配

性能参数不相同（或一个FMC没有安装）

（1）软件不匹配或失效：

当探测到一个数据库不匹配或失效的数据库，主FMC显示DATABASE CROSSLOAD页面，数据库按下列顺序进行交输：

Source/Destination Indicator

SOFTWARE OPTIONS（OPC）

模型/发动机数据（MEDB）

NAV DATA（NDB）

PERF DEFAULTS（LDDB）

另外，当OPC使能的话下列的数据库也将交输：

QRH T/O SPEED

DATALINK CONFIG（ADDB）

Flight Plan Data

（2）模拟离散和性能因子不匹配：

任何存在的程序和数据库不匹配状态纠正，模拟离散和性能因子不匹配状态按顺序处理。当这些不匹配状态存在时，ANALOG DISC和PERF FACTOR页面自动显示出来，不匹配的参数也会高亮显示。

故障案例

1、上电后CDU显示SINGLE FMC OPERATION信息，通过FMC自检测试和对离散页面检查发现左右FMC的ACARS INSTALLED显示不一致（ON/OFF高亮）。通过复位FMC跳开关后信息消失，信息消失时两侧显示OFF或ON，手册要求都是ON，此时ACARS使用都正常。

检查FMC程序销钉M1991模块1#开关，作动开关后CDU显示不变，复位FMC跳开关或飞机重新上电后显示偶尔会变化，线路检查正常，单独测量M1991模块1#开关通断，会发现阻值变化异常。将1#开关的销钉安装到备用开关2#位置，检查显示正常，重新上电后显示也正常。因为ACARS INSTALLIED信号为静态离散信号，以系统上电时检测到的信号为准。

2、落地后两侧ND显示FMC DISAGREE信息。

FMC自检测试有FMC MISMATCH信息：

进一步检查离散信号左右FMC航向参数不一致，串件隔离确认FMC-R故障。

3、机组反映无法输入到计划高度参数，CDU提示MAX ALT FL310。检查发现性能因子参数不正确。

对于新换上的FMC，燃油因子F-F可能与另一侧的不一致会导致FMC故障灯亮。更换FMC的AMM手册要求检查F-F，左右必须一致且要在范围内，如果不一致需要更改到一致，更改性能因子的AMM给出了每个参数的范围值，切记更改其他参数，参数设置错误可能会导致机组无法正常使用FMCS，航路点无法输入，变签行显示高度限制等等。

DRAG FACTOR+0.0，F-F FACTOR +0.0，MNVR MARGIN 1.30， MIN CRZ TIME 1，MIN R/C CLB 300，CRZ 100 ，ENG OUT 100。

4、性能起始页面巡航高度和油量输入框显示空白（无输入框），有

MODEL/ENG DATA INVALID信息。检查识别页面的MODEL 和ENG RATING栏显示空白。

检查FMC离散页面3/4检查MODEL/ENG是否有效：

检查软件是否正确（如下图无性能数据）：

5、琥珀色MAP和VTK（vertical track）故障旗在MAP和PLAN模式显示。

The FMCS formats and transmits the data (FMC bus 08 and FMC bus 09) to show the airplane position with respect to the flight plan and vertical profile. The CDS controls symbol color, size, and brightness.

The MAP flag shows if the map data from the FMC is invalid or NCD. All map data is blanked in this condition.

The VTK (vertical track) flag shows when the vertical deviation data from the FMC is invalid or NCD. Only the vertical deviation scale is blanked in this condition.

If a problem reported by the flight crew is based on a software fault, replacing the FMC will not result in correction of the reported fault. Example: VTK Flag on the map display is indicative that the associated FMC was either offline or restarting.

6、两侧MCDU都显示PROGRAM PIN ERROR，进入CDU离散页面检查MODEL/ENG参数显示PARITY。

FMC机身/发动机程序销钉奇偶校验错误时或SDI离散销钉不正确时PROGRAM PIN ERROR信息出现在CDU上，可能故障原因(1)机身/发动机程序销钉，(2) SDI离散销钉，(3) FMC。

在两个CDU上进入FMCS ANALOG DISC 2/4页面，检查3R（SRCE/DEST INDENT）显示LEFT/RIGHT是否正确，按需检查对应FMC的SDI离散，左右FMC离散3/4页面检查MODEL/ENG，是否VAILD，如果错误则显示PARITY ERROR。测量FMC1和2各自后部插头的B12（MODEL/ENG销钉为B12）至程序销钉PIN8之间的导通电阻和绝缘电阻正常，扰动后续线束未见量线阻值跳动。更换M1990程序销钉。