mercoledì 1 febbraio 2017

Avionics bending: Symbol Generator

A. The flight instrument system provides the main displays for most of the airplane's navigation systems. It includes the electronic flight instrument system (EFIS), the radio distance magnetic indicators (RDMI), and the vertical speed indicators (VSI). It also includes the switches on the instrument source select panels.

B. The EFIS uses CRT indicators. It provides multicolor navigation displays. The system displays the following:

(1) Pitch, roll, and directional data; map displays and flight path data; weather radar data; altitude and decision height; autopilot mode data; and input system fault annunciations.

(2)Airspeed data.

(3)Traffic alert and collision avoidance data.

C. The two displays associated with the EFIS are the Electronic Horizontal Situation Indicator (EHSI) and the Electronic Attitude Director Indicator (EADI). Two units of each display are installed.
Each set operates independently under normal conditions. Each display set has a dedicated control panel, remote light sensor, and a symbol generator. A third symbol generator is installed, as a backup, for either display set.

D. The switches on the instrument source select panels provide selection for backup data sources in the event of a main data source failure.

E. Normally, the left and right symbol generators supply the corresponding display set. If a fault is detected by the operating symbol generator, either display set can be switched to the center symbol generator. The RDMIs and VSIs can be switched to the center IRU if a source fault is detected.
F. If the captain and F/O select the center EFIS system, a level B caution message - INSTR SWITCH - will appear on the EICAS Display.
G. The RDMIs are the secondary heading, bearing, and distance displays. A portion of the indicators display the airplane's present heading. They also display the directional bearing and navigational distance to selected reference points.
H. The RDMIs receive this data from the IRS, VOR, DME, and ADF systems.
I. The VSIs are the main vertical rate-of-climb and descent display. They receive this data from the inertial reference system.
In the following pics, a view inside of a Symbol generator during cleaning process
All Boars and power supply removed
Power supply installed
 Display driver card installed
 All cards installed, ready to be closed
SG front view