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Airbus 117VU parking brake panel
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introduction
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 This article is about the Airbus 117VU parking brake panel. This is a panel that's located at the left lane of the pedestal of the Airbus A340 cockpit. The panel is 'just a fancy switch' to (de)activate the parking brake. There's a large two position rotary switch installed with a knob that has to be lifted for changing the position. At first sight of the parking brake this looked like some mechanical switch, but a toggle switch would technically do the same. Since you don't want to slip the switch by accident, the large lift knob prevents accidental position change.
 Panel identification: 117VU
Part number: F925 10070 000 00
Part number: F925.10070.000.00
Part number: F9251007000000
Note: This panel is fully functional still, but it's service life is expired. Therefore the serial number is removed to prevent usage of the panel in another aircraft. This makes these panels affordable for hobbyists since serviceable parts are usually rather expensive.
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panel description
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 The Airbus 117VU panel is 'just' a panel like the other panels applied. The construction of the panels are rather similar. There's am aluminium front panel with a blue/grey coated translucent plastic cover. The rear panel with the connectors is mounted on a set of stand-offs. The wiring is properly tie-wrapped and marked where needed. All the relevant components are identified like '3GZ' for the rotary switch and '695VN' for the ground post.
The used machine screws are the TORQ-SET type. Don't mistake the name with TORX and don't mistake the shape with Phillips nor Pozidrive.
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backlight
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 The Airbus A320/A340 panels are equipped with 'advanced' illumination. Older panels have regular 5 Volt incandescent light bulbs or later on leds as a light source. (28 Volt illumination is also possible.) By regulating the voltage, the brightness can be regulated for these older style panels. These Airbus panels are 'smarter'. Each panel has an printed circuit board that operates on 28VDC. By regulating a 0...5 Volt signal, the brightness can be controlled. So each overhead/pedestal panel is fed with a common 28 VDC power source and a 0...5 Volts brightness regulating signal. The brightness signal is an 0...5 VAC signal as marked on the front panel, but a 0...5 VDC works also perfect. (5 VAC signals are rather common for panel illumination, so applying this standard is rather wise.)
At full brightness (28 VDC + 5 VDC), the current consumption at 28 VDC is just 34 mA. That's just below 1 Watt of total power used. The current of the 0...5 Volt brightness signal is negligible.
There are a couple of light control knobs available. The brightness of the pedestal panels are regulated by a variable resistor placed in the INTEG LT panel.
 On the image can be seen where the parking brake panel is located. It's located at the left side of the pedestal. The brightness of the overhead and pedestal 'contour lighting' is controlled by light panel 111VU. The middle knob is the 'INTEG LT' (integral lighting) knob for regulating the panel brightness.
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panel details
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Since a couple of panels are damaged that I want to restore, I wanted to find out the colour coding. Based on my experience the colour code for Airbus panels is RAL7031 (marine blue). Usually airplane structural parts are zinc chromate coated and have a 'green yellowish' colour. I planned to create a frame for my overhead panel and I want to make this as realistic as reasonably possible. Therefore my idea is to coat the aluminium frame in the same colour as the zinc chromate parts. Since chrome based paints are bad for your health, I don't want to use the original paint. Therefore I'll use 'regular' paint in the same colour. Based on my perception the colour matches the RAL1020 (olive yellow) number.
The panel is a DZUS mount panel of seven height units. Every unit is 3/8" or 9,525 mm. Therefore the space needed in the pedestal is 66,675 mm high. The width of the needed panel space is 5,75" = 146,05 mm. The actual panel size is a little bit smaller to create some play around the panel. (Likely is the panel 1/64" = 0,016" = 0.40 mm trimmed.) The horizontal DZUS center to center distance is 5 3/8" = 136,53 mm. See this article for more DZUS panel details.
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reverse engineering
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To use the parking brake panel functional, I need the schematic. Therefore I reverse engineered the electrical schematic. To find out the design, the panel is partially disassembled. One of the findings is that he panel is very, very dirty! The panel is placed horizontal and therefore all the food particles, dust and stuff is collected onto the top of the panel. The result is a 'nice' collection of sticky filth. So the next step is further disassembly and deep clean everything.
The design is rather simple so reverse engineering was rater easy. It's 'just' an illuminated panel with a rotary switch...
I spent some time reverse engineering the 117VU parking brake panel and documenting the wiring. I want to wire the panel to some controller vor simulator purposes and I wanted to keep the panels in it's original state. So (non destructive) reverse engineering was the way to go. Easier is to cut all the wires and remove unwanted parts, but that's not my strategy. I made a document with the relevant technical information. The technical document of the 117VU parking brake panel can be found by clicking this text.
To make this article more readable I copied the relevant information from the document to the images below. Im the image below is the wiring visible of the parking brakt rotary switch. The (3GZ) switch has four linked switches built in. The contacts are directly wired to the pins of connectors 695VC and 697VC. The pin markings are shown in the circle and the corresponding connector identification is also noted for each contact. Remind that the switch has internal electrical links as drawn.
To make things easier I made two truth tables. Based on the tables below it's possible to wire the parkin brake without too much of a hassle.
The front panel is equipped with an illumination controller board. By applying 28 VDC to pin 'E', connecting the power return (ground) to pin 'F' and applying a 0...5 Volt control signal to pin 'G', the panel illumination can be controlled. This illumination lights up the text on the panel.
There are also two ground wires installed to pins 'J' and 'H'. The (simple) wiring is shown below.
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connectors
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 There are two connectors available on the rear panel. Both connectors are clearly marked. Connector 697VC is the 'main' connector for the ground connection, the panel illumination and the half of the parking brake switch connections. The other connector is the 695VC connector. This connector has the connections of the other half of the parking brake rotary switch. 'Only' five pins are used of this connector.
The used pins are gold plated. The not used pins are installed but not gold plated.
The small connector 695VC has a regular key position at the 'A' pin. The larger 697VC connector has a small angle offset compared to a regular connector. Usually the centre 'A' pin is located at the key of the connector. To prevent a wrong connection to a panel with a connector of the same shell size and same number of pins, the keyway can be rotated in several positions. Probably this connector is near another connector of the same shell size and pins number so the angle offset is needed to prevent connector/plug mix-up.
A nice thing is that the connectors are anodized aluminium instead of (toxic!) cadmium plated connectors. The construction is rather simple and straight forward. The panels are durable but also engineered to be as light as possible without the risk of losing it's quality.
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my project
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 By some 'coincidence' I got the opportunity to buy overhead panels of an Airbus A340. I saw this as once of a lifetime opportunity so I bought the stuff. Unfortunately some panels are missing like the light panel 215VU. A year later I bought an additional set of panels for almost completing the overhead panel. My idea is to make the overhead panel 'Arduino functional' so the buttons, lights an annunciators can be controlled by the Arduino code. Since I have some surplus panels (flaps, parking brake, light control panels and ECAM swirch panel the idea is now also to build the pedestal. To get everything working will probably take a lot of time, so no hurries here. The idea is also to document every panel for anyone can use the information like simulator builders...
It's not my intention to build a fully functional simulator or an exact copy. To get everything 'right' takes too much money I guess. I don't have the radio not audio panels, so I'll use look alike panels that are 'in stock' here. ;-) The idea is to get the radio's functional tough. (Something with a modified panel, an Arduino controller and a Kenwood TH-D7E transceiver...)
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former aircraft
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 This panel has marking *AV307* so it's likely that this is a panel from an 340-313X with registration F-GLZR formerly of Air France. This plane is built on 11 October 1999, the first flight was on 19 October 1999, stored in January 2018 and scrapped on October of 2018. For the data lovers: the seat configuration was C30 W21 Y224 and it had four CFMI CFM56-5C4 engines.
Credits to Alexis Boidro from France for the photo!
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Source: Photo: Alexis Boidro
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