B737-800 NG Flight Mode Annunciator (FMA)
September 18, 2014 at 21:44
FLAPS 2 APPROACH in Annunciators, Automatic Flight Systems, B737 Flight Simulator, B737-800, B737-800 Flight Simulator, Boeing 737-800 NG Flight Simulator, FMA, FSX, Flight Mode Annunciator, Flight Simulator, Mode Control Panel (MCP)

Automatic Flight System - Background

The Boeing 737-80 has a relatively sophisticated Automatic Flight System (AFS) consisting of the Autopilot Flight Director System (AFDS) and the Autothrottle (A/T).  

LEFT:  Flight Mode Annunciator (FMA).  This is photograph has been take in a real aircraft and provides a good idea to the size, font and position of the FMA.

The Boeing 737-800 NG has a relatively sophisticated Automatic Flight System (AFS) consisting of the Autopilot Flight Director System (AFDS) and the Autothrottle (A/T).   The system is as follows:

If you read through the above slowly and carefully it actually does make sense; however, during in-flight operations it can be quite confusing to determine which system is engaged and controlling the aircraft at any particular time.

Reliance on MCP Annunciations

Without appropriate training, there can be a reliance on the various annunciations and lights displayed on the Mode Control Panel (MCP).  While some annunciations are straightforward and only illuminate when a function is on or off (such as the CMD button), others can be confusing, for example VNAV.

Do not reply on the MCP.  Always refer to the FMA to see what mode is controlling the aircraft.

Flight Mode Annunciator (FMA)

All Boeing aircraft are fitted with an FMA of some type and style.  The FMA on the Next Generation is located on the Captain and First Officer side Primary Flight Display, and is continuously displayed.  The FMA indicates what system is controlling the aircraft and what mode is operational.  All flight crews should observe the FMA to determine operational status of the aircraft and not rely on the annunciators on the MCP that may, or may not indicate a selected function.

The FMA is divided into three columns and two rows. The left column relates to the Autothrottle while the center and right hand column display roll and pitch modes respectively.  The two rows provide space for armed and selected annunciations to be displayed.  Selected modes that are operational are always coloured green while armed modes are coloured white. 

Below the two rows are the Autopilot Status alerts which are in larger green-coloured font, and the Control Wheel Steering (CWS) displays which are coloured yellow.  The Autopilot Status alerts are dependent upon whether a particular system has been installed into that aircraft.  For example, Integrated Approach Navigation (IAN), and various autoland capabilities.

When a change to a mode occurs (either by by a flight crew or by the Automatic Flight System), a mode change highlight symbol (green-coloured rectangle) is displayed around the changed mode annunciation.  The rectangle will be displayed for 10 seconds following the change in mode.

Unfortunately, not all avionics suites have the correct timing (10 seconds) and some displays the rectangle for only 2 seconds.  According to the Boeing manual the default time should be 10 seconds.

Important Points:


The following U-Tube link is a very good video that shows several annunciations being displayed on the Primary Flight Display.

The below image and table (ProSim-AR 737 avionics suite) indicates the more common mode annunciations that the FMA can display.  In the image, the pitch mode column and CWS display are not populated.  Furthermore, the FMA annunciations may differ between airframes depending upon the software installed to the aircraft (and avionics suite used in your simulation).  G, W and Y indicates the colour of the annunciation (green, white, or yellow).

NOTE:  Autoland capability and IAN have not been addressed as not every aircraft has these features installed.

ERRATUM to table: I have failed to mention in this image ILS, SINGLE CH and IDLE (update to come as time permits) - apologies....

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