Basic Interfacing
The diagram below illustrates the basic interfacing of the GCU to the operator and the other system components.
Operator Interface
The pilot has one switch to control and one annunciation light to monitor:
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The GEN on-off switch will turn the power generation ON or turn it OFF.
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The GEN-OFF light will light-up when power generation is OFF-LINE.
Starter-Generator / Line-Contactor / Electrical System Interface
The GCU interfaces with the starter/generator to drive the shunt field, and measure generator loading and voltage.
The line-contactor links the main aircraft electrical bus to the starter/generator and is also controlled by the GCU.
Operational Scenario
When you switch the aircraft MASTER switch ON you will notice the GEN-OFF indicator turns on for about
2 seconds while the GCU performs a system self-check. The light goes out to show all is good and ready.
You perform a start.
After the start as your engine reaches idle speed, the GEN-OFF light comes on.
You switch the GEN on-off switch to ON.
The GEN-OFF light goes dark.
The generator is now on-line.
Should you decide to turn the generator off, you can simply move the GEN on-off switch to the OFF position. With the engine
turning the GEN-OFF light comes on to indicate the generator is now off-line. To bring the generator back on-line you simply
return the GEN on-off switch to the ON position. The GEN-OFF light will go dark as the generator again kicks in.
The GCU has built-in protection against fault conditions as listed under features above. If one of the conditions is detected
by the GCU, it will firstly take the generator off-line by opening the line-contactor to isolate the starter/generator from the main bus.
Secondly, the GEN-OFF light will turn on. The pilot can address the cause of the fault and decide to
re-engage (reset) the generator. This is done by switching the GEN on-off switch to OFF for about a second and then back to ON again.
The GCU will attempt to bring the generator back on-line, and if successful the GEN-OFF light will turn off and stay dark.
Maintenance Operations
From time to time a Laptop PC and USB-to-Serial Converter may be connected to the GCU within the system,
as depicted below, in order to perform maintenance operations on an installed system.
Maintenance operations allow you to confirm (troubleshoot) your installation, make adjustments,
view operational information and record a certain operation. All these tasks are done through the
VR System Link software running on the laptop.
System Link enables making adjustments to set-points, calibration values and
other configuration settings, such as adjusting the relugation voltage set-point (26.0V to 30.0V).
More Information
Additional information is contained in our GCU manual, wiring diagrams, etc. listed in the colum
on the right side of the web page. You'll also find GCU firmware updates here that we provide free of charge to all customers.
This firmware will be updated from time to time to provide additional features and improvements.
Also, please feel free to contact us with any query you may have regarding any of our products.
Register your Interest
You may register your interest by contacting us so we will be able to keep you informed as to the progress
of this product and when it will become available. You are also very welcome to ask questions or make suggestions regarding the product.
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