|
|
start | weblog | knowledge base | for sale | photo dump | measurement data |
| Airbus 125VU Engine Master Switch panel |
| introduction |
 This article is about the Airbus 125VU Engine Master Switch panel. This panel is used to activate or deactivate each of the four jet engines installed on the Airbus A340. This panel is installed in the pedestal in front of the throttle quadrant.The main engines are too big to start electrically. So the startup is a little bit more complicated. The APU (Auxiliary Power Unit) is an (electrically started) jet engine that supplies electrical power and air during startup phase if the main engines are still off. Each main engine is started by supplying the bleed air from the APU to a main engine. The bleed air is used to spin up a main engine to be started. Since the available air is limited, each engine is started individually. By selecting the desired master engine switch the desired engine is started. If the selected engine has a certain speed, the fuel is injected,the ignition is started and the bleed air valve (for starting) is closed. Than the next engine can be started my switching the next engine master switch for the desired engine until all four engines are up and running. Now the main engines are used to supply bleed air, electrical power, hydraulic power and eventually thrust for flying. Each master switch is locked, so it must be lifted to change position to prevent accidental switching an engine off (during flight). For each switch is also an indicator lamp installed. The top half of the indicator can show [FIRE] to indicate an engine fire and the bottom half of the indicator shows [FAULT] to indicate a faulty state. Note that the indicator lamp has in this case no switch function and can't be pressed. |
| reverse engineering |
 Unfortunately schematics of avionics are very hard to find, so reverse engineering is the way to go. I spent some time making the reverse engineering drawing of the panel. The raw notes are shown below. |
| panel illumination and ground connections |
On the image below is the reverse engineering schematic shown for the ground connection and the panel illumination. There are two wires used for the ground connection of the aluminium base plate of the panel. For the panel illumination is +28 VDC used to power the illumination circuit. There's a printed circuit board in the front panel with some logic electronics and leds for illumination. The 5 Volt input is used to control the brightness of the panel. Originally 5 VAC is used for illumination control, but 5 VDC works also perfect. The current draw is rather low since the panel contains leds instead of incandescent light bulbs like in the older style panels as used in the Airbus A320. |
| Korry indicator lamps |
Each of the four engine switches has also an Korry style indicator lamp installed. The top half of the indicator can show 'FIRE' and the bottom half can show 'FAULT'. In case of an engine fire the corresponding engine master switch is hereby easily recognised. There are also 'Korry' indicators with a switch built in. In this case there's no switch built in and only the indicators are used. Each half has two 5V incandescent light bulbs that draw approximately 110mA each.  |
| the engine master switches |
There are four engine master switches. One switch for each engine. Although each switch has only an off and on position, each switch has six sections. Each section has a common contact, a normally closed (NC) and a normally open (NO) position. All the contacts are shown on the drawing below. For simulator use only two wires have to be used like the common and the normally open connection. The rest is for redundancy. The switches are drawn in the 'off' position. |
|
Service ➤ About ➤ Contact |
Over deze site ➤ Taal naar Nederlands (mits beschikbaar) ➤ Cookie information ➤ Reset session ➤ Disclaimer/Proclaimer ➤ Copyright |
| Copyright © reiding.com 1984 - 2025. All rights reserved. |