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Welcome

Mission Statement 

The purpose of FLAPS-2-APPROACH is two-fold:  To document the construction of a Boeing 737 flight simulator, and to act as a platform to share aviation-related articles pertaining to the Boeing 737; thereby, providing a source of inspiration and reference to like-minded individuals.

I am not a professional journalist.  Writing for a cross section of readers from differing cultures and languages with varying degrees of technical ability, can at times be challenging. I hope there are not too many spelling and grammatical mistakes.

 

Note:   I have NO affiliation with ANY manufacturer or reseller.  All reviews and content are 'frank and fearless' - I tell it as I see it.  Do not complain if you do not like what you read.

I use the words 'modules & panels' and 'CDU & FMC' interchangeably.  The definition of the acronym 'OEM' is Original Equipment Manufacturer (aka real aicraft part).

 

All funds are used to offset the cost of server and website hosting (Thank You...)

No advertising on this website - EVER!

 

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If you see any errors or omissions, please contact me to correct the information. 

Journal Archive (Newest First)
Saturday
Mar032018

Wind Correction (WIND CORR) Function - CDU

Wind Correction (WIND CORR)

The approach page in the CDU has a field named WIN CORR (Wind Correction Field or WCF).  Using WIND CORR, a flight crew can alter the Vref+ speed (additive) that is used by the autothrottle to take into account headwinds greater than 5 knots. 

LEFT:  OEM CDU showing WIND CORR display in Approach Ref page (click to enlarge).

The default reading is +5 knots.   Any change will alter how the FMC calculates the command speed that the autothrottle uses.  Any change is reflected in the LEGS page. 

It's important to update the WIND CORR field if VNAV is used for the approach or of executing an RNAV Approach, as VNAV uses data from the Flight Management System to fly the approach.   However, if hand flying the aircraft, or executing an ILS Approach, it's often easier to add the Vref additive to the speed window in the MCP.  Indeed, flight crews for the most part, other than when using VNAV, leave the WIND CORR as its default (+5 knots), and change airspeed by using the MCP or by using Speed Intervention (SPD INTV).

WIND CORR Explained

The ability to increase the Vref speed is very handy if a flight crew wishes to increase the safety margin the autothrottle algorithm operates.

Boeing when they designed the autothrottle algorithm programmed a speed additive that the A/T automatically adds to Vref when the A/T is engaged.  The reason for adding this speed is to provide a safety buffer to ensure that the A/T does not command a speed equal to or lower than Vref.   (recall that wind gusts can cause the autothrottle to spool up or down depending upon the gust strength). 

A Vref+ speed higher than +5 can be inputted when gusty or headwind conditions are above what are considered normal.  By increasing the +speed, the  speed commanded by the autothrottle will not degrade to a speed lower than that inputted.

How To Use WIND CORR

WIND CORR is straightforward to use.   

Navigate to the approach page in the CDU (press INIT REF key to open the Approach Reference page).  Then double press the key adjacent to the required flaps for approach (for example, flaps 30).  Double selecting the key causes the flap/speed setting to be automatically populated to the FLAP/SPD line. 

It’s important to understand that this is the Vref.  This calculation ALREADY has the +5 additive added; this is the speed that the aircraft should be at when crossing the runway threshold.  

LEFT:  Virtual CDU (ProSim-AR) showing the difference in Vref between a +5 and +13 Knot Wind Correction change.  Vref altered from 152 knots to 160 knots (click to enlarge).

If the headwind is greater than 5 knots, then WIND CORR can be used to increase the additive from the default +5 knots to anything up to but not exceeding 20 knots. 

Type the desired additive into the scratch pad of the CDU and up-select to the WIND CORR line.  The revised speed will change the original Vref speed and take the headwind component into account.  If you navigate to the LEGS page in the CDU, you will observe the change. 

Note that the Vref speed displayed on the Primary Flight Display (PFD) does not change.  This remains at Vref +5.

For a full review on how to calculate wind speed, review this article: Crosswind landing Techniques - Calculations, or read the cheat sheet below.         

LEFT:  Wind calculation cheat sheet (click to enlarge).

Important Varibles - Aircraft Weight

To obtain the most accurate Vref for landing, the weight of the aircraft must be known minus the fuel that has been consumed during the flight.

Fortunately, the Flight Management System updates this information in real-time and provides access to the information in the CDU.  It's important that if an approach is lengthy (time consuming) and/or involves holds, the Vref data shown will not be up-to-date (assuming you calculated this at time of descent); the FLAPS/Vref display will show a different speed to that displayed in the FLAP/SPD display.  To update this data, double press the key adjacent to the flaps/speed required and the information will update to the new speed.

Interestingly, the difference that fuel burn and aircraft weight can play in the final Vref speed is quite substantial (assuming all variables, except fuel, are equal).  To demonstrate:

  • Aircraft weight at 74.5 tonnes with fuel tanks 100% full – flaps/Vref 30/158.
  • Aircraft weight at 60.0 tonnes with fuel tanks 25% full   – flaps/Vref 30/142.

 Important Points:

  • During the approach, V speeds are important to maintain.  A commanded speed that is below optimal can be dangerous, especially if the crew needs to conduct a go-around, or if winds suddenly increase or decrease.  An increase or decrease in wind can cause pitch coupling.
  • If executing an RNAV Approach, it's important to update the WIND CORR field to the correct headwind speed based on conditions.  This is because VNAV uses the data from the Flight Management System (FMS).
  • If an approach is lengthy, the Vref speed will need to be updated to take into account the fuel used in the aircraft.  

Autoland

Autolands are rarely done in the Boeing 737, however, if executing an autoland, the WIND CORR field is left as +5 knots (default).  The autoland and autothrottle logic will command the correct approach and landing speed.

Functionality

WIND CORR may or may not be functional in the avionics software you use.  It is 100% functional in the ProSim-AR 737 avionics suite (Version 2).

Acronyms

CDU – Control Display Unit
FMC – Flight Management Computer
FMS – Flight Management System (comprising the FMC and CDU)
Vref - The final approach speed is based on the reference landing speed
Vapp – Vapp is your approach speed, and is adjusted for any wind component you might have. You drop from Vapp to Vref usually by just going idle at a certain point in the flare

Thursday
Feb012018

Variation in Panel Colour, Manufacture & Location - Center Pedestal

The center pedestal in the Boeing 737 accommodates a number of panels, several of which are standard for all commercial passenger airlines.  All high-end simulators replicate these panels and enthusiasts often fixate on several issues.  Namely:

(i)         The colour of the panel and lightplate;

(ii)        The position of the panel in the center pedestal;

(iii)       The backlighting of the lightplate (bulbs verses LEDs);

(iv)       The manufacturer of the panel, and;

(v)        The aesthetic condition of the lightplate.

Although seemingly important to a cockpit builder, to the casual observe, or indeed to many pilots, these attributes are of little consequence.  Nevertheless, it's understandable why many believe all the panels are identical in all B737 airframes.

Whilst it's true that all airlines must meet aviation standards for the type of operation they fly, the panel manufacturer and where in the pedestal the panel is located is at the discretion of the airline.  Furthermore, it's not uncommon to observe older style panels mixed with modern panels and to see lightplates that are illuminated by bulbs and LEDs side by side.

Note that some of this information probably pertains more to older Next Generation 737s than to the latest airframe build released from Boeing.  I use the word 'panel' to denote an avionics module.

Colour of Lightplates

The official colour shade used by Boeing is Federal Standard 5956 36440 (light gull grey).  However, OEM part manufacturers may use slightly different colour hues.  For example, IPECO use British Standard 381C-632 (dark admiralty grey) and Gables use RAL 7011.  This said, often an airline will 'touch up' a lightplate that is damaged or faded - this introduces a further colour variant. 

LEFT:  Air Alaska 737-700 pedestal.  Note higher than standard position of ACP panels and relocated position of the door lock panel.  Also high mounted position of rudder trim panel (click to enlarge).

As an example, a lightplate I repaired from a B737-500 airframe revealed three differing shades of grey beneath the final top coat of paint.  This is not to mention that, depending on the manufacturer of the lightplate, the final coat of paint may be matt, semi-matt or gloss.

From the perspective of an engineer, the colour (and to a certain extent aesthetic  condition) is unimportant when replacing a defective part with another.  Time spent in the hanger equates to a loss in revenue by the airline.  Therefore turn-around times are as brief as possible and keeping an aircraft on the ground while procuring the correct shade of Boeing grey does not enter the equation.

Position of Panels in the Center Pedestal

Boeing recommends a more or less standard position for the essential panels in the center pedestal (NAV, COM, ADF, ASP, rudder trim, door lock and panel flood), however, the location of the panels is often altered by the receiving airline, and is to a certain extent is determined by what other panels are installed to the pedestal.  Areas (holes) in the pedestal not used by a panel are covered over with a grey-coloured metal blank.

LEFT:  This photograph of the center pedestal of a Boeing 737-500 was taken in 2016.  The aircraft is a freighter used to transport parcels that has been converted from a passenger aircraft.  Apart from the older style ACP panels, note the disparate displays between the NAV and COM radios.  Also note the position of the ADF radios and some of the other panels; they do not conform to what is usually thought of as a standard set-out.  Finally, note the scratches on the pedestal and on some of the panels and lightplates - they hardly look new (click to enlarge).

Panels are manufactured by several companies, and often there appearance will differ slightly between manufacturer, although the panel's functionality will be identical.  The airline more often than not chooses which panel is used, and often the decision is biased by the cost of the panel.  Therefore, it's not uncommon to observe several airframes of a similar age with differing panels positioned in different areas of the center pedestal.

Panel Condition

Enthusiasts pride themselves in having a simulator that looks brand new.  However, in the real world a Level D simulator or flight deck rarely looks new after entering service.  Panels can be soiled and paint is chipped and scratched, and depending on age, some lightplates are faded to due to the high UV environment that is present in a flight deck.

So where am I going with this?  Enthusiasts strive to match their panels with those observed in a real airliner, however, more often than not this information comes from photographs distributed by Boeing Corporation (which nearly always depict panels in a standard position in the center pedestal). 

The variables noted by enthusiasts should not cause consternation, as real aircraft show similar variation.  Remember that in the real aircraft, colour, manufacturer, and to a certain extent aesthetic condition is not important - functionality is.

To see additional photographs, navigate to the image portal.

Tuesday
Dec192017

Maintaining Backlighting Brightness Across OEM and Reproduction Panels

Many enthusiasts are now using Original Aircraft Equipment (OEM) panels in their simulators.  These panels are connected to Flight Simulator using a variety of interface cards.  Unless the flight deck uses all OEM panels, or all reproduction panels, there will be a difference in backlighting when the light plates are illuminated.

LEFT:  FDS-IBL-DIST-DIM.  A card that makes diming backlighting very easy.  Potentiometer is not shown (click to enlarge).

Reproduction panels, with the exception of expensive very high end types, will have exceptionally bright backlighting.  Manufacturers of reproduction panels want their panel to look good and appeal to a prospective buyer – this is why they have bright backlighting.  In contrast, OEM panels do not have  bright backlighting, and in some cases, depending upon the manufacturer of the panel, the backlighting will appear rather dim.  

Therefore, the brightness of the backlighting when using ‘run of the mill’ reproduction panels is not realistic in comparison to that observed in a real aircraft.

So how does a cockpit builder solve this conundrum of brightness if he or she has a mix of reproduction and OEM panels.  The solution is very simple – install a dimmer switch into your flight deck.

Dimmer Control

There are a number of 5 volt dimmer switches on the market and some are better than others.  For those with electrical knowledge it’s relatively straightforward to make your own dimmer switch, but what about the rest of us?  An excellent solution is the distribution board with built in dimmer control manufactured by Flight Deck Solutions (FDS).  The board keeps with the principle of KIS (keep it simple).  

FDS-IBL-DIST-DIM

The distribution board is well made, small, is fuse protected, and have the capability to connect up to 14 accessory LEDS or bulbs via propriety board connectors.  The board also can be used as a slave, meaning it can be daisy-chained to another board to increase the number items attached.

The distribution board includes a pre-wired metal potentiometer which allows all the LEDS/bulbs attached to the board to be dimmed from on to off or anywhere in-between.  The potentiometer is a standard size and fits the hole located in the panel lights panel on either a reproduction panel or an OEM panel.

One limiting feature that should be noted is that each distribution board will only support 10 amps - the rating of the fuze. 

Of more importance, the board operates flawlessly and is a very easy solution to maintaining an even brightness across reproduction and OEM panels; adjust the brightness of the reproduction panels to the same level as the OEM panels.

Connection

Connection is straightforward and requires +- 5 volts to be connected to the board.  Each LED (or bulb) that requires dim control is then connected to the board connectors.  If using an FDS panel this is very easy as the FDS panels already use the correct female attachment plugs (FDS also use bulbs and not LEDS).  Failing this, a little extra work is required to source the correct plugs and wire them to the +- wires that connect to the light plate.

Bulbs and LEDS

On another note, with the exception of late model airframes, the Next Generation B737 use 5 volt incandescent bulbs in their panels for backlighting.  This is in contrast to reproduction panels that, for the most part, use LEDS.  

The difference between bulbs and LEDS, other than construction, is the temperature they generate when turned on.  A bulb will generate considerable heat and the colour of the light will appear as a warmer hue.  A LED does not generate heat when turned on.  Therefore, an LED will have a cooler temperature and the colour of the light will be colder and more stark in its appearance.

However, before changing out all your bulbs or LEDS to maintain colour consistency, study the flight deck of a real aircraft.  Panels on all aircraft fail or need upgrading from time to time.  Therefore, it is not unrealistic o have a flight deck consisting of both LEDS and bulbs.  Airlines are in the business of making money, and pilots fly.  Neither are particularly interested in whether the ADF radio has a bulb or LED.

Additional Information

Soar-By-Wire has also discussed this subject.  Although his information relates to the Airbus, the same proceedure can be done for Boeing OEM panels.

Disclaimer

I do not represent Flight Deck Solutions or any other manufacturer and have no received any fee or reward for discussing one of their interface components.

Further information pertaining to the distribution board can be found on the Flight Deck Solutions website.

A fellow enthusiast has written more information on his website about the distribution board as it relates to Airbus - Soarbywire.  What he has written is well worth the time reading.

Friday
Nov172017

Sounds Reworked - Flight Sim Set Volume (FSSV) - Review

Immersion is a perception of being physically present in a non-physical world.  The perception is created by surrounding the user of the simulator in images, sound or other stimuli that provide an engrossing total environment.  When something does not replicate its real world counterpart, the illusion and immersion effect is degraded.

LEFT:  Engine sounds will be at their highest at takeoff.

Engine Sound Output

The sound output generated by a jet aircraft as heard from the flight deck is markedly different when the aircraft is at altitude.  This is because of differences in air density, temperature, the speed of the aircraft, drag, and thrust settings.  The noise emitted from the engines will always be highest at takeoff when full thrust is applied.  At this time, the noise generated from wind blowing over the airframe will be at its lowest.  At some stage, these variables will change and wind noise will dominate over engine noise.

As an aircraft gathers speed and increases altitude, engine sound levels lower and wind levels, caused by drag, increase.  Furthermore, certain sounds are barely audible from the flight deck on the ground let alone in the air; sounds such the movement of flaps and the extension of flight spoilers (speedbrake).

Being a virtual flyer, the sound levels heard and the ratio between wind and engine sound at altitude is subjective, however, a visit to a flight deck on a real jet liner will enlighten you to the fact that that Flight Simulator’s constant-level sound output is far from realistic.

Add On Programs

Two programs which strive to counter this shortcoming (using different variables) are Accu-Feel by A2A Simulations and FS Set Volume (FSSV).  This article will discuss the attributes of FSSV (Sounds Reworked).

Flight Sim Set Volume (FSSV)

FSSV is a very basic program that reads customized variables to alter the volume of sound generated from Flight Simulator.  The program is standalone and can be copied into any folder on your computer, however, does require FSUIPC to connect with Flight Simulator.  Wide FS enables FSSV to be installed on a client computer and run across a network.  

The following variables can be customised:

(i)     Maximum volume
(ii)    Minimum volume
(iii)   Upper mach threshold
(iv)   Lower mach threshold
(v)    Engine volume ratio

Each of the variables will alter to varying degrees the Mach, engine %N1, rounded engine speed and volume percentage.  

For the program to have effect it must be opened either prior to or after the flight simulator session is opened. 

LEFT:  FSSV pop-up screen showing customised variables (default) that can be set and current reads-outs for the simulator session (click to enlarge).

It’s an easy fix to automate the opening of the program to coincide with Flight Simulator opening by including the program .exe in a batch file

A pop-up window, which opens automatically when the program is started, will display the variables selected and the outputs of each variables.  If the window is kept open, the variables can be observed ‘on the fly’ as the simulation session progresses.  Once you are pleased with the effects of the various settings, a save menu allows the settings to be saved to an .ini file.  The pop-up window can then be set to be minimized when you start a flight simulator session.  

How FSSV Works

The program reads the sound output from the computers primary sound device and alters the various sound outputs based upon customized variables.  The program then lowers the master volume at the appropriate time to match the variables selected.  FSSV will only alter the sound output on the computer that the program is installed.  Therefore, if FSSV is installed to the same computer as Flight Simulator (server computer) then the sound for that computer will only be affected.

Possible Issue (depends on set-up)

An issue may develop if FSSV is installed on a client computer and run across a network via Wide FS, then the program will not only affect the sound output from the server computer, but it also will affect the sound output from the client computer.  

A workaround to rectify this is to split the sound that comes from the sever computer with a y-adapter and connect it to the line-in of another computer, or use a third computer (if one is spare).

In my opinion, it’s simpler to install and run the program via a batch file on the server computer that flight simulator is installed.  The program is small and any drop in performance or frame rates is insignificant.

Summary

The program, although basic, is very easy to configure and use - a little trial and error should enable the aircraft sounds to play with a higher degree of realism.  However, the level that you alter the variables to is subjective; it depends on your perception to the level of sound heard on a flight deck – each virtual flyer will his or her own perception to what is correct. 

The program functions with FSX and P3D flawlessly. 

Finally, If you are unhappy with the result, it’s only a matter of removing/deleting the folder you installed the program to, or close the program during your simulator session to return the sound levels to what they previously were.  FS Set Volume can be downloaded at no charge at http://forum.simflight.com/topic/81553-fs-set-volume/.  

Video

The below video is courtesy of the FSSV website.

Friday
Aug042017

OEM B737 CDU Conversion - Using SimStacks To Convert The CDU

This article follows on from an earlier post that introduced the concept of converting an OEM CDU to use in flight simulator.  The conversion has now been completed and the CDU operates seamlessly with ProSim-AR.   

LEFT:  OEM CDU fully converted and operational.  The CDU is from a classic 500 series aircraft.  Prior to my ownership, the CDU was used by United Airlines (click to enlarge)

Historical Conversion Techniques

To date, various OEM parts have been converted using Phidget cards, and to a lesser extent Leo Bodnar cards, Flight Deck Solutions system cards, and PoKeys interface cards.  Phidgets provide a stable platform, despite the disadvantage that they, at time of writing, only connect via USB to the server computer.  The primary advantage of using Phidgets is that they have been used in a wide variety of applications, are inherently stable (for the most part), and their configuration is well documented.

The conversion of the CDU was slightly different to the norm, in that a different interface system was used. 

SimStacks by Simulator Solutions

The conversion of the CDU was done in collaboration with Sydney-based company Simulator Solutions Pty Ltd.  Simulator Solutions utilise their propriety interface boards called SimStacks to convert OEM parts for use in commercial-grade simulators

SimStacks is a modular, stackable, and scalable hardware interface that is designed to integrate OEM parts into your simulator with little or no modification.    One of the many advantages in using a SimStack Foundation Board (SFB) is that the interface can connect with either the server or client computer via Ethernet (as opposed to Phidgets). 

To date, Simulator Solution’s experience has been predominately with the conversion of B747 parts and Rodney and John (owners) were excited to have the opportunity to evaluate their software on the 737 platform, with the 737 CDU being the ‘first cab off the rank’.

This article will not delve deeply into the SimStack architecture, nor will it document the wire pin-outs used with the interface card; a future post will tackle this topic in more detail. 

CDU Conversion - Choose Your Poison

There are two main camps when discussing how to convert an OEM part.  The first is to utilise as much of the original wiring and parts as possible.  The second is to completely ‘gut’ the part and convert it cleanly using an interface that connects seamlessly with the avionics software in use (ProSim-AR).  A third option, although expensive and in many respects ‘experimental’, is to use ARINC 429.

With regard to the CDU, the easiest route was option two; everything in the CDU was removed with the exception of the internal shelf divider and keypad.  In hindsight, the pin-outs of the Canon plugs could have been used, but to do so a female Canon plug would have been required, and for the use of a couple of pins, this seemed to be overkill.

Keypad and Screen

The keypad and screen are the two most important parts of the CDU, and it's vital that the connection between the keypad, screen, and the SimStacks Foundation Board is not compromised.  The actual functionality of the CDU is controlled by the avionics suite.

Keypad

The keypad forms part of the lightplate in which 5 Volt incandescent bulbs are strategically located to ensure even backlighting of the keys.  Disassembling and removing the keypad from the main body of the CDU is straightforward; several small Philips head screws hold the keypad in place.  Once the keypad has been removed, any ‘blown’ bulbs can be replaced. 

Table 1: Overview of bulb location, part number and quantity.

The keypad has several wires that connect to a terminus inside the main body of the CDU.  Care must be taken when cutting the strands of wire to ensure the connection between the terminus and the keypad is not damaged.  Depending upon your skill, the terminus can be removed and a longer wire soldered to the keypad connector, or the wire can be lengthened (by splicing).  The wires from the terminus connect with the SimStack Foundation Board.

CRT and LCD Screen

The Classic CDU is fitted with a solid glass cathode ray tube (CRT) screen.  The CRT screen is approximately 2 cm thick and fits snugly within the display frame of the CDU. 

LEFT:  The CRT screen forms part of the CDU casing.  The silver coloured foil indicates the thickness of the replacement glass that needed to be ground (click to enlarge).

It’s possible to make the CRT screen operational, however,  the display would be monochromatic (green) and the screen resolution poor.  Therefore, the CRT was replaced with a custom-sized high resolution colour LCD screen.

To retrofit a replacement screen is not without its challenges.  The LCD screen is not as thick as the CRT screen, and is also not the same shape.  Therefore, the screen will not fit snugly within the display recess.  To rectify this shortfall, a piece of clear glass was ground to correctly fit within the display frame of the CDU.  This piece of glass replaces the 2 cm thick CRT glass.  The thin LCD screen was then mounted behind the clear glass in a central position.

During the design phase, it was thought that the thick piece of glass would cause a refraction problem.  However, although the theory suggests refraction will occur, the practical application has been such that any refraction is not readily noticeable.

Mounting the LCD Screen

Mounting the LCD screen can be done a number of ways.  Commercial grade double-sided sticky tape is the easiest method, but it is rudimentary.

LEFT:  LCD screen is fitted and temporarily held in position by commercial tape and a foam spacer.  Prior to revamping the CDU, this area was used to house the very large square shaped CRT screen.  Note the ribbon cable linking the screen to the screen interface card and the two white cables that connect to the screen controller card and SFB (click to enlarge).

To secure the LCD so that the screen sat firmly against the glass, thin metal plate was used to replace the open space that was left after removal of the CRT screen.  The sides of the metal plate were fabricated to push against the rear edge of the LCD.  This firmly secured the LCD screen against the rear of the clear glass.

LEFT:  The photograph shows the metal plate that was fabricated to replace the original CRT unit.  The edge of the plate pushes against the rear of the LCD screen holding the screen in place.  To remove the plate cover, 2 screws need to be removed.  It's amazing that the CRT screen required the amount of space that it did  - about 5 inches square! (click to enlarge).

Although the use of metal plate appears slightly unattractive, the plate only serves to enclose the CDU.  Once the CDU is slid into the CDU bay, the the casing of the CDU is not visible.

An alterative to using metal plate is to use ABS plastic painted the correct Boeing grey colour.

SimStack Foundation Board, External Wires and Screen Controller Card

To ensure that the CDU is standalone and will function without external inputs other than power supplies, four items need to be mounted inside the CDU.

(i)    The generic Interface card that controls the LCD screen;

(ii)    The LCD screen controller (buttons that control brightness, contrast, etc);

(iii)   The SimStack Foundation Board; and,

(iv)   The wiring to connect the keyboard to the Foundation Board.

Fortunately, there is ample room in the cavernous interior of the CDU to fit these items.

LEFT:  SimStack Foundation Board (SFB) mounted into the lower section of the CDU casing.  The SFB is responsible  for registering the key presses made on the keypad which are then deciphered and communicated to the avionics suite (ProSim-AR).  Click to enlarge.

The SimStack Foundation Board is mounted on an angular metal bracket that is attached directly to the bottom of the CDU, while the LCD interface card has been installed on the upper shelf along with the screen controller.  A ribbon cable connects the LCD screen to the interface card while a standard VGA cable connects the LCD screen to the client computer. 

The SimStack Foundation Board is Ethernet ready and requires a standard Ethernet cable (CAT 6) to connect from the card to an Ethernet switch (located behind the MIP). 

In addition to the Ethernet  and VGA cable, six power wires leave the CDU via the rear of the casing; four from the SimStack Foundation Board (5 and 12 volts +-) and two from the keypad (5 volts +-) to control the backlighting.

Toggle Switch

A standard two-way toggle switch is mounted to the rear of the CDU casing.  This switch is used to control whether the LCD screen, used in the CDU, is always on, or is only turned on when ProSim-AR is activated.  The switch is set and forget, however, access to the switch can be made from the front of the MIP or by sliding the CDU our of the CDU bay.

 

LEFT:  Toggle switch and wire harness leaving the base of the CDU casing.  The switch position and harness use the existing holes in the casing that were previously used by the Canon plugs.  5 and 12 volt wires are connected to appropriate busbars behind the MIP, while the VGA cable connects with the client computer.  The Ethernet cable connects into the Ethernet switch, also mounted at the front of the MIP (click to enlarge).

Power Supply

To operate the CDU requires a 5 and 12 volt power supply.  The backlighting of the keypad is powered by 5 volts while the SimStack Foundation Board and CDU operation require 12 volts.

Backlight Dimming

On my set-up, to enable the CDU keyboard to be dimmed, the 5 volt wires that leave the lower section of the CDU, are connected to a dedicated 5 volt Busbar located in the center pedestal.  This Busbar is used to connect the backlighting from all OEM panels.  The Busbar is then connected to the panel knob on the center pedestal.  The ability to turn the backlighting on and off is controlled by opening or closing a 12 volt relay (attached in line between the panel knob and Busbar).  Dimming is controlled by a dimmer circuit.

Mounting the CDU to Flight Deck Solutions MIP

The MIP skeleton and CDU bay is manufactured by Flight Deck Solutions (FDS), and is designed to fit FDS’s propriety CDU unit (MX Pro) and not an OEM unit.

The casing for the OEM CDU is much longer than the FDS CDU and measures 24 cm in length.

The FDS MIP incorporates an aluminum shelf (used by FDS to mount various interface cards) that protrudes slightly into the CDU bay.  This protrusion stops the OEM casing from sliding all the way into the bay.  To enable the CDU casing to slide fully into the bay, a small section of the shelf must be cut away.

A small metal saw is used to trim the metal away from the shelf, and although an easy task, care must be taken not to ‘saw away’ too much metal.  Once the piece of offending aluminum is removed, the casing of the CDU slides perfectly into the bay, to be secured by the DZUS fasteners to the DZUS rail.

LEFT:  Using a small metal saw, s small section of the shelf is removed.  This enables the CDU to slide into the CDU bay.  Left image is the shelf projecting into the CDU bay while the right image shows the shelf removed and covered in protective tape (to minimise abrasion).  A small notch was made at the corner to facilitate the safe routing of the wires used to enable the Lights Test (click to enlarge).

Functionality and Operation

The CDU is not intelligent; it’s basically a glorified keyboard that requires interfacing with software for functionality.  The functionality, fonts, colour, etc are provided by the avionics suite (in this case ProSim-AR, but arguably it could also be Sim Avionics or Project Magenta). 

To enable communication between the avionics suite and the SimStack Foundation Board (in the CDU casing), SimStack proprietary software must be installed.

SimStack Software - SimSwitch

SimSwitch is installed on the client computer and when configured interfaces with ProSim-AR on the server computer and the network.  Configuring SimSwitch is straightforward and involves inputting the correct static IP address and port numbers.

LEFT:  Screen grab showing SimSwitch software interface.  This is located on the client computer.  The interface, once configured, is standalone.  The software can easily be opened in minimized mode via a batch file (click to enlarge).

SimSwitch can also be used to monitor all connected OEM panels and provide debugging information if needed.

SimSwitch is a JAR archive executable file.  The file must be in operation to eanable the CDU to communicate with the avionics suite. 

The JAR file and the ProSim CDU .exe file must both be open for the CDU to function correctly.  To expedite a simulator session, the JAR file can very easily be added to a batch file for automatic loading of software prior to a simulator session.  A timer command can be added to the batch file line ensuring the JAR file opens before the ProSim CDU.exe file. 

First Officer CDU

The First Officer CDU will be converted using a similar technique, with the exception that this unit will be converted more ‘cleanly’.

(i)    A dedicated plate (rather than an angular bracket) will be fitted to the inside of the CDU casing.  This will facilitate the mounting of the SimStacks Foundation Board;

(ii)    The LCD screen controller will be attached to the inside of the casing in a more accessible area;

(iii)    The LCD screen will be fitted to customised bracket making installation easier; and.

(iv)    The LCD controller card will be fitted to the rear of the screen; and,

(v)    The Ethernet cable connector will located outside the casing.  This will provide easier access and also enable less of a tight fit when reassembling the casing.

Additional Photographs and Video

Additional photographs can be viewed in the image gallery.

BELOW: A short video demonstrating the operation of the OEM CDU using ProSim-AR. 

Main points to note in the video are:

(i)    Heavy duty tactile keys;

(ii)   The definite click that is heard when depressing a key;

(iii)  The solid keypad (the keys do not wobble about in their sockets); and,

(iv) Although subjective, the appearance of the OEM CDU looks more aesthetically pleasing that a reproduction unit.

Final Call

This conversion, by using a SimStack Foundation Board (SFB), has enabled full functionality of the OEM CDU using ProSim-AR.  The SFB can also be used to connect with other avionics suites, such as Sim Avionics and Project Magenta.  However, although the wiring of the SFB would be identical, the way in which the card interfaces and communicates with the avionics suite will differ.

Glossary

ARINC429 –  A standard used to  address data communications between avionics components.  The most widely used  standard is an avionics data bus.  ARINC 429 enables a single transmitter to communicate data to up to 20 receivers over a single bus.

SFB - SimStacks Foundation Board.

Standalone – Two meanings.  (i)   Operation does not require an interface card to be mounted outside of the panel/part; and, (ii)  In relation to software, the executable file (.exe) does not need to be installed to C Drive, but can be executed from any folder or the desktop.