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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.

 

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

 

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Journal Archive (Newest First)

Entries by FLAPS 2 APPROACH (193)

Monday
May152017

MCP and EFIS By SimWorld - Review

This article will review and evaluate the Mode Control Panel (MCP) and Electronic Flight Instrument System (EFIS) produced by SimWorld in Poland.  It will also briefly examine the use of the CANBUS controller system (SimBox). 

LEFT:  Mode Control Panel (MCP) by SimWorld.  The image looks impressive and the looks do not deceive as this MCP has many advantages over other panels. (promotional photograph © SimWorld (click to enlarge at super size).

The MCP will be discussed first followed by the EFIS and CANBUS system.  Where some areas overlap they will be discussed together.  I use the word panel to denote either the MCP or EFIS.  Also, OEM is an acronym for Original Equipment Manufacturer (aka real aircraft part).  

This review is not endorsed by SimWorld and is entirely my view based on first-hand experience using the MCP and EFIS.  

Background

The mainstay for several years has been the MCP and EFIS produced by CP Flight in Italy.  For the most part, these panels have delivered consistent and reliable performance, despite their rather dated design and engineering.  

However, there are several distinct differences in aesthetics and functionality between the CP Flight units and OEM counterparts.  Furthermore, many CP Flight panels had connection problems caused by the nature of how the MCP was connected to the server computer (using a virtual communication port).  

Reason for Updating MCP and EFIS

Until updating to the SimWorld MCP and EFIS, I had used the panels manufactured by CP Flight (2015 Pro USB interface model), but technology is not idle.  The use of high-end CNC machines and electronics has enabled many parts to me made, that are in many respects indiscernible from the real item.

Initially, I attempted to find OEM panels.  Although the older non-Collins style MCP could be found, it wasn’t possible to find the newer Collins unit at an affordable price.   

SimWorld provides, at the time of writing, the closest resemblance to the OEM panels.  Furthermore, the use of the CANBUS enables trouble-free connection.

Pre-Sale

The MCP and EFIS are not inexpensive; add to this Government import charges and UPS freight and you have spent a considerable sum of money.   With an increased price comes the expectation of higher quality, reliability, robustness, and attention to detail; let’s examine how SimWorld shapes up to this maxim.

The SimWorld website provides considerable information, including photographs and a video demonstrating the MCP and EFIS.  Although imagery can save a thousand words, questions usually need to be asked.   Filip and Piotr spent considerable time answering my specific queries and e-mails were replied to in a timely manner.   Their customer focus has been top shelf in every respect.

Aesthetics, Manufacture and Detail - MCP

The Mode Control Panel (MCP) and Electronic Flight Instrument System (EFIS) are the main avionics panels used in a simulator, and most enthusiasts strive to replicate the appearance and functionality of these panels as closely as possible to the those in the real aircraft.  

Quick List Main Advantages (SimWorld MCP):

(i)         1:1 in comparison to the OEM MCP;
(ii)         Correct Boeing-grey colour;
(iii)        Screws located in the correct location on the front panel;
(iv)        Flight Director thumb stops;
(v)         Use of externally protected printed circuit boards (PCBs);
(vi)        Motorised autothrottle arming switch with automatic release to off;
(vii)       Ambient sensor (2017 MCP model, not functional);
(viii)      Does not use seven-segmented displays;
(ix)       Ability to accurately display +- and other specialist fonts;
(x)        Push to engage annunciators are backlit in green (when depressed) and are separate to the colour of the backlighting;
(xi)       Integrated backlighting uses a built-in PCB for reliable dimming control;
(xii)      Correct styled knobs made from painted aluminum;
(xiii)     Correct smoky-coloured display windows positioned in frames identical to the OEM MCP;
(xiv)     Functionality that replicates the OEM MCP (depends on avionics suite used); and,
(xv)      Use of commercial grade rotary encoders.

Internal Components

The components for the MCP and EFIS panels are for the most part machine-made; however, the components are assembled by hand on a market-demand basis.   To ensure production repeatability, SimWorld use a number of printed circuit boards (PCBs) sandwiched together to provide core functionality.

LEFT:  External casing removed showing multiple Printed Circuit Boards PCBs).  Click to enlarge.

A PCB contains numerous ‘tracks and pads’, that are used for input and output devices, memory chips and processors, and various electrical components such as resistors and capacitors.  An advantage of using PCBs is that troubleshooting can be done via a tethered computer, and if a problem is detected, a board can easily be replaced.  This is because, theoretically, each PCB for each panel is identical in design, layout and population.

System Logic and Functionality

The MCP and EFIS are a hardware-user interface that has been designed from the outset to provide full flexibility in relation to functionality.   However, although the panels may have the appropriate hardware in place, the logic to enable the functionality to operate is supplied by the avionics suite in use (for example, ProSim-AR).  

MCP Light Plate

The light plate has been professionally made and the various precut holes (cut-outs) are well finished.  The laser-engraved lettering on the light plate is precise, evenly cut, and does not differ across the unit.  Additionally, the colour of the paint is the correct Boeing gray and does not differ in hue between the MCP and EFIS light plates.

The manufacture of a light plate is quite involved, and an individual plate or batch will take on average 3 days to complete.   Prior to cutting, several thin layers of paint are applied to the light plate.  A laser is then used to engrave the required letters down to the white-coloured base layer.  The base layer is transparent to light, and when backlit, the lettering can easily be read.

SimWorld use the same technology (or very close to it), that is used to manufacture the OEM light plate.

Exterior Casing

The light plate is attached to a series of printed circuit boards (PCBs).  The PCBs and electronics are protected by a 1 mm thick exterior casing.  The casing is made from aluminum and measures 3 inches in depth perpendicular to the front of the light plate.  The casing is powder coated and coloured black.

On the rear of the panel is a female 12 Volt DC power connector, and a connection for the plug that connects the MCP to the CANBUS system.

Knobs

The appearance and colour of the knobs is very similar to the OEM knobs.  Each knob, with the exception of the vertical speed wheel, is made from machine-cut aluminum and is the correct colour.  The knobs are well finished with no sharp edges, or left over metal from the milling process.   One or two metal set screws secure each knob to the shaft of the rotary encoder.

LEFT:  Detail of heading knob and bank selector pointer.  Note the detail in the window bezel and the well defined laser engraving on the lightplate (click to enlarge).

The heading knob incorporates a functional bank selector pointer (made from plastic), and the vertical speed wheel is produced from high grade molded plastic.  There are no injection holes in the plastic and the end finish passes scrutiny.

The knobs are tactile (feel solid to touch) and when rotated generate a well-defined audible click (similar to the OEM knobs on the MCP).  

Rotary Encoders

Not all rotary encoders are made equal: a high-end encoder is constructed to an exacting standard predominately using metallic components.  To rotate such an encoder requires a mild effort; there is resistance – it isn’t difficult, but you can’t move it left or right with a flip of a finger.   

In comparison, hobbyist-style encoders are considerably cheaper to purchase, are made to a less exacting standard and usually have a shaft and body produced from plastic.  The encoders are easy to rotate and can also wear out prematurely with extended use.

SimWorld use quality Swiss made rotary encoders, rather than using low quality encoders from China.  Each encoder has a cylindrical metal shaft.  A metal shaft is important as a plastic shaft can wear prematurely, in addition to becoming damaged from overzealous tightening of set screws (which hold the knob in place).

I have been told that military specification (MilSpec) encoders are available, however, SimWorld use these encoders only for high-end commercial simulators.

Resistance When Rotating Knobs - Comparison With OEM Honeywell and Collins MCP

Resistance when rotating the knobs will depend on the MCP model.  The knobs on the older Honeywell models are very easy to rotate - A finger with just a ‘tad’ of pressure will move the knobs, however, the newer Collins model has more resistance, but the knobs are still very easy to rotate with minimal force.   As one First Officer stated: ‘You can definitely hear a soft click as you move the encoders - especially on the Honeywell models’.

By comparison, the resistance felt when rotating the knobs on the SimWorld MCP, although difficult to quantify, is similar to the resistance felt when rotating the knobs on the OEM MCP – It is realistic and does not feel ‘toy like’.  

Backlighting

The backlighting is controlled by a number of 5 Volt light emitting diodes (LEDs).  Each LED has been strategically located in the light plate to ensure even coverage and intensity of light.  

However, the MCP does exhibit slight light bleed along the join between the light plate and the protective casing.  This is not a problem as when the MCP is mounted into the MIP, the stray light is not noticeable.  If necessary, cloth tape can be placed over the join to eliminate any stray light.

LEFT:  The stray light is at the interface where the exterior casing joins the lightplate.  This area is covered by the MIP when the panel is mounted (click to enlarge).

Backlight Dimming - Dimmer Interface Card (DIC)

The MCP and Captain-side EFIS can be dimmed together, while The First Officer EFIS is capable of being dimmed independent of the Captain side EFIS.  This is how it occurs in the real aircraft.

To enable the panel backlighting to be dimmed, SimWorld have used a dedicated PCB (DIC).  The use of a PCB ensures that dimming is reliable, accurate, and highly controllable.   The PCB is standalone, is roughly the size of two credit cards and can be mounted anywhere.

The DIC is connected to the CANBUS system via the custom wiring harness and then to the appropriate potentiometer that controls panel backlighting.   Panel backlighting can be dimmed from off to any brightness level.  

To enable dimming, a potentiometer must be wired to the PCB (DIC).  

Power

The MCP requires 12 Volt power, while the backlighting uses 5 Volt power that is connected to the DIC.

MCP Annunciators

The annunciators are not glorified micro-switches, but are push on/off buttons that when depressed emit an audible click.  The resistance felt as the button is pressed, is slightly less than the pressure required to engage an OEM annunciator.  The square push button and frame is made from plastic, and the cylindrical shaft that the button connects with is made from metal.  

SimWorld have replicated each of the square-shaped buttons exceptionally well, and for the most part their external appearance is identical to the OEM counterpart.

Each annunciator is connected to the primary MCP PCB, thus eliminating the use of wires.  If an annunciator is broken during the course of its life, replacement is relatively straightforward and involves soldering the connection of the replacement annunciator to the PCB.

Status Checkerboard and Legend

Each annunciator on the MCP comprises a square push button, a rectangular-shaped checkerboard, and a legend.

The checkerboard is made by engraving a number of holes that, when the annunciator is pressed, enables green-coloured light to be transmitted through the checkerboard.  The checkerboard is similar to the OEM panel and has the same number of engraved holes.

Each annunciator has a legend that uses multi layer technology (proprietary to SimWorld).  Multi layer technology is what enables the backlighting of the checkerboard and legend to be a different colour.  The name of each annunciator (speed, VNAV, N1, etc.) has been engraved into the legend.   

Unfortunately, the engraved letters are not as defined as you would expect; the lettering is slightly jagged in appearance (enlarge above image). 

LEFT:  The detail of the annunciators is very good and the jagged appearance of the lettering only becomes apparent when they are backlit.  The backlight intensity is set to 100% (click to engage).

This is noticeable only when observed very close-up; from a normal distance (seated) this is barely noticeable and therefore, not really an issue.   However, the ability of the legend to transmit light evenly through the cut-out lettering is noticeable as the jagged appearance causes the names to appear slightly ‘furry’ (brighter or dimmer) depending upon the amount of light that can travel through the lettering, and your viewing position.

The annunciator legends and the checkerboard, are illuminated by strategically-placed LEDs.  

Window Bezels and Liquid Crystal Displays (LCDs)

The two main differences that separate an OEM MCP from a reproduction MCP are the design and appearance of the bezels that surround the display window, and how the actual characters (digits) are displayed.

SimWorld have used a black-coloured bezel that surrounds each of the display windows.  The bezel is identical to the bezels in the OEM MCP, and the join between the bezel and the display frame is seamless.

Equally, the use of custom-made Liquid Crystal Displays (LCDs), with each display backlit by one LED, is what causes SimWorld’s design to stand-out above its competition.  

The combined use of LCDs and LEDs enables each character (digit) to be displayed in the correct shape, colour and size.  This is in addition to displaying the specific characters used in the speed window (under and overspeed conditions) and the +- symbols displayed in the vertical speed window.

LEFT:  The checkerboard is identical in appearance across all annunciators.  Note the ambient sensor and + character in the vertical speed window.  Also the very slight difference in the illumination of the + sign  Backlightng is set ~50% intensity (click to enlarge).

Although appearing rudimentary, this is similar to how the OEM displays are illuminated.  To my knowledge, all other manufacturers of reproduction MCPs use seven-segmented displays.

While the use of this type of display is a positive step forward, it is not without its negatives; if the LEDS are incorrectly positioned, or the throw of light is not even across the rear of the LCD, then the characters will not be evenly lit.  This may cause some of the characters in a display to be brighter or dimmer (hot or cold spot).

To counter against this, quality assurance (QA) must be exceptionally thorough.  I will discuss QA later in this article.

LCD Brightness

As discussed earlier, each LCD is backlit by a single LED (this is how the characters (digits) are illuminated).

LEFT: Backlighting at full intensity is excellent (click to enlarge).

The brightness of the digits is linked to the intensity of the backlight dimming.  Therefore, as backlighting is dimmed, the brightness of the LEDs behind each LCD is lowered.   Although this is exactly how dimming operates in the real aircraft, I find that during the day in bright conditions, with the backlighting turned off, it’s difficult to read the digits as their intensity is not very bright.  At night and in low light conditions this is not an issue as the digits can easily be read. 

A solution to this issue is for SimWorld to enable an alternate method (although not as done in the real aircraft) to allow the brightness of the LEDs to be independent of backlighting.

Autothorttle (A/T)

The A/T toggle, controlled by a solenoid-release mechanism, resembles the OEM toggle.

The system logic SimWorld use in the toggle is slightly different to other reproduction MCPs, in that the toggle can only be engaged when certain conditions are met (system logic).

If the correct conditions are not met, then the toggle cannot be engaged; the toggle will not stay in the engaged position (up) but flick back to the disengaged position (down).  Be aware that for this functionality to operate, the avionics suite in use must also have this capability.

 

Electronic Flight Instrument System (EFIS)

Disregarding OEM panels, the SimWorld EFIS is probably the best on the market (at the time of writing).   Each EFIS replicates its OEM counterpart in both appearance and functionality, and is the correct size (1:1).

LEFT:  Captain-side EFIS panel with backlighting at full intensity.  The lightplate is well made and the laser engraving is well defined enabling even illumination of backlighting accross the panel.  The BARO STD knob has purposely been left slightly left of center.  When the BARO knob is released it will spring back to the central position (click to enlarge).

Two noticeable positives are the concave-designed push in/out function buttons on the lower portion of the unit, and the use of independent duel rotaries that are centrally spring-loaded.  

Quick ListMain Advantages (SimWorld EFIS):

(i)      Correct size and dimensions (1:1);
(ii)     Use of externally protected printed circuit boards (PCB);
(iii)    Correct Boeing-grey colour;
(iv)    Accurate aluminum knobs with set screws;
(v)     Independent backlighting between Captain-side and F/O side EFIS units;
(vi)    Two speed rotary encoders which auto-center (BARO and MINS);
(vii)   Well defined laser-cut lettering on light plate; and,
(viii)  Concave-designed push buttons.

Manufacture and Detail - EFIS

The EFIS has been manufactured and assembled in a similar way to the MCP.  The EFIS panels are 1:1, are the correct shaded grey colour, include the appropriate screws located in the correct location, and have the correct styled knobs.  As with the MCP, the EFIS use printed circuit boards which are then protected by an exterior aluminium casing.

LEFT:  First Officer side EFIS.  Knob length, functionality and detail are as per the real aircraft as is concave function buttons and well defined lettering and even backlighting accross the lightplate (click to enlarge).

EFIS Light Plate, Backlight Dimming and Exterior Casing

The laser-cut lettering on the light plate is crisp and sharp, and when the EFIS is backlit the light is evenly spread at the same intensity across the panel. 

Both EFIS panels are dimmed through the same dimmer interface card (DIC) used for the MCP, however, the F/O EFIS panel can be dimmed separately to the Captain-side panel (as it is done in the real aircraft).  

The protective casing that each EFIS resides measures 5 inches in depth perpendicular to the light plate.   On the rear of the unit is a female 5-volt DC power connector, and a connection for the plug that connects the EFIS to the CANBUS system.

Knobs

The manufacture of the knobs is similar to the knobs used on the MCP, with the exception that a centrally-placed disc has been laser engraved to enable the function name to be backlit.  The lettering on the discs is crisp and sharp.  The knobs are held securely to the rotary shaft by two metal set-screws.  

LEFT:  First Officer side EFIS.  The lettering and black disc is well made.  The metal set screw that attaches the upper knob to the dual rotary can be observed.  The upper knob is self centering (click to enlarge).

The pointer (black & white line) on the function selector knob is a transfer that has been glued to the outside of the knob.  The adhesive has been solidly applied and I doubt the transfer will come loose.

Rotary Encoders

The rotary encoders are similar to those used in the MCP and have a metal cylindrical shaft.  Each of the encoders is a double encoder meaning that it has dual functionality.

Specialist Functionality - BARO and MINS

The barometric pressure (BARO) and radio altitude/pressure (minimums) function exactly as those in the real aircraft.  The outer knobs are spring-loaded, and when rotated and released, self-center with the label resetting to the horizontal position.  The knobs also are push to reset.

Each knob has two speeds: a slight turn left or right turn will alter the single digits, while holding the encoder left or right for a longer period of time will change the double digits, and cause the digits to change at a higher rate of speed.   

The below video, taken inside the flight deck of a B73-800 aircraft shows the operation of the OEM BARO and MINS (courtesy Shrike 200).  The SimWorld BARO and MINS knobs operate the same way.

 

Concave-shaped Function Buttons

The function buttons on the EFIS are concave in shape and made from plastic (this differs to the rubberized buttons seen on several OEM EFIS panels).  Each button has the name of the function engraved into the button.  The engraved letters are crisp and sharp and when the panel is backlit, the letters are evenly illuminated without hot or cold spots.  

Each button’s mechanism is made from plastic, and while the use of plastic is understandable, metal probably would increase the mechanism’s service life.  

Minor Problem - Sticky EFIS Button

A minor issue developed after installation of the EFIS into the bracket.  Two function buttons when pressed, would not automatically reset themselves (click in and click out).  The problem only presented when the panel was mounted into the bracket faceplate.

After carefully examining the bracket and protective casing, it was found that when the EFIS was mounted into the MIP, the casing was compressed against the button.  This caused the button to remain pushed in.

The problem was resolved by slightly bending the aluminum external casing so that it did not rub against the button’s mechanism. 

Functionality

The functionality of the EFIS is identical to the OEM EFIS.

MCP and EFIS Bracket

SimWorld provide a sturdy bracket that is used to mount the MCP and EFIS panels to the Main Instrument Panel (MIP).

LEFT:  SimWorld propriety bracket to mount MCP and EFIS into the SimWorld MIP.  The bracket is solid and very well made (click to enlarge)

The bracket consists of a front faceplate and a rigid bracket framework.  Both items are made from 1 mm thick, black-coloured, powder coated aluminum.  The faceplate is precut to allow fitment of the MCP and EFIS.  The framework provides stability to stop the EFIS panels from wobbling in the precut hole.  

Mounting The Bracket To The MIP

The bracket is designed to be used with SimWorld’s propriety MIP, however, the bracket can be used with other MIPs.  Take note that, depending upon which MIP is used, the bracket/MIP may need to be modified.

I retrofitted the bracket to a Flight Deck Solutions (FDS) MIP which was not without its problems. 

Problems Retrofitting The Bracket to the FDS MIP

The FDS MIP, the distance between the Captain-side and F/O-side glarewings did not allow enough room to enable the bracket faceplate to be fitted; the bracket was approximately 1 mm too long, and the bracket framework was too deep to easily slide into the recess of the FDS MIP.

These shortcomings were rectified by shaving away a small portion of the inner side of each glarewing.  This enabled the bracket faceplate to fit snugly between the glarewings.  

To use the bracket framework (which is quite deep), the internal structure of the FDS MIP has to be cutaway, an act that may affect the structure of the MIP.  Therefore, the framework was discarded and only the bracket faceplate was used.  

Without the framework to provide stability, the EFIS panels wobbled somewhat in the bracket faceplate.  To stop the EFIS from wobbling, small wedges made from wood were fabricated and installed between the EFIS and the inside edge of each glarewing.  Once the wedges were installed, the EFIS did not wobble.  The MCP is secured to the bracket faceplate by four screws which inhibits any movement.

A facsimile of the piece of metal that covers the underneath portion of the MCP was made from thin metal, painted black, and the appropriate screws added.

Wiring Harness

SimWorld supply a high quality wiring lumen that consists of four colour-coded wires with connectors.  The wires connect to the MCP and EFIS, and then to a 5 and 12 Volt power supply, dimming interface card (DIC), and the CANBUS system.  The power connections are standard push pull plugs and the wires that connect the MCP and EFIS with CANBUS use wire tap connectors (T-taps).   The length of supplied wire approximately 12 feet and SimWorld provide a basic wiring diagram.

LEFT:  T-taps can damage wires causing connection issues, so should be viewed as a temporary set-up (click to enlarge)

Wire Connectors

The use of wire tap connectors (wire chomper), although very convenient, should probably be looked at only as an initial connection when testing the panels.  For a more permanent connection, soldering the wires is preferable.  Soldering will remove the possibility of any troublesome connection.  

Let me explain,  the act of pressing the wire into this slotted metal piece bludgeons the wire. The concept behind this is fine – it’s supposed to strip back the insulation on the wire to make contact with the wire itself. The problem is that there is no guarantee that you won’t accidentally catch some of the wire in this process and tear some of the individual wire strands.  Additionally, if the insulation is broken over a wire, there is a possibility of corrosion (oxidation) occurring.  

Push-Pull Power Plugs

Although the use of a push/pull power plug is standard to many appliances, the connection is not tight.  If pressure is applied to the power cable, it is easy for the plug to become dislodged and loose connection with the MCP or EFIS.  

LEFT:  Power plug and CANBUS connector.  Each panel is connected to CANBUS by one of these connectors, and then to the dimming interface card (click to enlarge)

On a simulator with motion control, vibration could cause the plug to be dislodged.  An easy matter to rectify, the security of this connection should be improved in future designs.

CANBUS Controller System

The CANBUS system (also called Simbox or CAN controller) enables communication between the server computer and the MCP (and specific SimWorld panels) and is a vital part of the SimWorld architecture.

CAN is an acronym for Controller Area Network and is a bus standard designed to allow micro controllers and devices to communicate with each other.  Simply put, CANBUS translates the CANBUS signal, allowing for control and communication through the computer.

The CAN controller system (printed circuit board) resides in a ribbed-aluminum case with two connectors at each end of the case; one side connects with the computer via a standard USB cable while the other side connects, via a specialist connection, to the wiring harness, and then to the MCP and EFIS panels.  The CAN controller does not require a dedicated power supply.

LEFT:  CANBUS module.  Made from aluminium and housing a Printed Circuit Board (PCB), the CAN controller is what connects the MCP and EFIS tot he server computer.  During all trials, CANBUS performed flawlessly with no drop outs, lags or failures (click to enlarge).

CANBUS is small and light enough that it can be mounted anywhere between the MIP and server computer.  I have the CANBUS unit secured to the rear of the MIP via a Velcro strap.

Connection and Drivers

CANBUS does not require any drivers to operate as it’s detected by ProSim-AR when the software is turned on.  Connection is immediate, and whatever configuration is needed is done automatically through Windows the first time CANBUS in connected to the computer.  

There should not be any connection or communication issues provided you have checked (ticked) the enable SimWorld drivers within the configuration/drivers tab of the ProSim737 software.  

Compatibility

At the time of writing, CANBUS is compatible with ProSim-AR (plug and fly).  A dedicated driver for iFly and PMDG is under development.  Prior to purchase, I would seek the advice of SimWorld to whether CANBUS is compatible with the avionics suite you are using.

Reliability of CANBUS

In one word - 'perfect'.   I have not had the MCP, EFIS or CANBUS disconnect during a flight simulator session.  This is using FSX and ProSim-AR (version 1.49).  As a test, I disconnected the CAN controller during a flight, then reconnected it.  The flight was not disrupted and the reconnection occurred effortlessly.

Robustness and Service Life

The life and serviceability of a product has a direct relationship to how the product is used (or abused) and the duration of use.   Modern electronics are very forgiving, and electronic problems (if any) usually develop soon after an item begins its service life.  If problems are not detected after first use, then it is not unusual for an item to have a considerable service life.

Some of the more common problems that occur with reproduction panels include; failing encoders, damaged plastic encoder shafts, worn out set screws, slippage of knobs, and faulty switches and buttons.  Additionally, knobs may wear out with use, and paint on the lightplate may chip.  

SimWorld have countered potential problems by using printed circuit boards, commercial metal encoders, aluminum knobs, metal set-screws, and by replicated, as much as possible the same processes used in the manufacture of OEM light plates.  

The above said, it's wise to remember that reproduction panels rarely replicate the robustness and exacting standards of an OEM product; therefore, they should be treated with respect and with care.   I expect that in time the paint on knobs will chip and wear thin with use - this is normal wear and tear.  I don't mind this 'wear and tear' look as it is very seldom you a knob that is shiny new - unless the aircraft is new.

Quality Assurance (QA), Customer Service, and My Experience

Put bluntly, when anything is done by hand there must be a very high level of Quality Assurance (QA) to ensure that design specifications and tolerances are met.  QA can be an expensive process as time is needed to inspect each individual panel and then, if imperfections are noted, make required alterations/repairs.

There is a direct relationship between the price that an items costs and the amount and level of QA that is performed.  You would not expect an inexpensive item mass-produced in China to have high QA – and it doesn’t, which is why many Chinese-produced products fail after a short period of time or have obvious defects.   However, if you are purchasing a high-end product with a high price tag then the expectation is that this product will meet specification, will not have problems, and be sold with an excellent warranty and support.

SimWorld realize that enthusiasts demand quality and strive to meet this requirement.  However, not everything passes muster first time around and sometimes products are released that are not quite up-to-standard.   Whenever this occurs the reputation of the company is tested.

To ensure transparency, I have documented the issues below not to provide negative criticism of SimWorld, but to highlight their dedicated customer support and strong company ethics.  

My Experience

The first MCP and EFIS sent to me from SimWorld did not meet my expectations and had several issues.  Namely:  

(i)     Uneven brightness of the characters (digits) across the five LCDs with some characters presenting as hot spots;
(ii)     Rotary encoders cross-referencing values;
(iii)    A/T arming toggle not locking into the arm position (UP position);
(iv)    Crooked LCD in the course display window; and,
(v)     The light plate on the EFIS was not mounted parallel to the backing plate (crooked).

I contacted SimWorld and they requested that I return the panels to Poland (at their expense) for repair.  

The problems experienced were caused by:

(i)     The positioning of the LED behind the LCD was slightly off center.  This was rectified;
(ii)    The rotary encoders were faulty and had been tracked to a bad batch released from the manufacturer.  They were replaced;  
(iii)   The autothrottle toggle was not aligned correctly with the magnetic plate mounted behind the light plate. This was fixed by moving the toggle very slightly to the left;
(iv)    The crooked LCD was straightened.  As the LCDs are mounted by hand, careful attention must be paid to ensuring they are straight; and,
(v)     The misalignment of the F/O EFIS panel was rectified by making it straight against the backing plate.  

Repaired MCP and EFIS

Unfortunately, following receipt of the repaired MCP, the Captain-side course display would not illuminate.

Piotr at SimWorld organized for my computer to be tethered to their technician’s laptop to enable bench testing.   Unfortunately, the technician could not determine what was causing the problem, but thought it may be a faulty capacitor.  

Rather than attempt to repair the MCP again, Filip arranged for a replacement MCP panel to be sent to me by UPS.  

Replacement MCP Panel

The replacement MCP, by chance, was the newer panel manufactured in 2017.  I have not had any problems with the replacement 2017 model MCP and EFIS.  Both panels function flawlessly and the attention to detail on the panels is beyond reproach.  

Warranty and After-Sales Service

The MCP and EFIS is covered by 12-month unconditional warranty.

The after-sales service and warranty cannot be bettered, and I cannot stress the advantages of dealing with a company that treats its customers with respect and places customer service as a priority.  

In relation to the issues I had with the MCP and EFIS, SimWorld responded to my e-mails within 24 hours, followed up on my questions, provided reasons for the problem, and kept me updated with regard to repairs and/or replacement.   The after-sales service and support provided to me has been exemplary.  

Negatives - MCP and EFIS

It’s difficult to find any major negatives.  However, if pressed they are:

(i)    During the day, the digits displayed in the LCDs are difficult to read if the backlighting is dimmed 100%;
(ii)    The power connection on the rear of the MCP and EFIS is not secure.  If any pressure is applied to a cable, then it’s very easy for the connector to become dislodged from the panel;
(iii)    The laser cutting on the annunciator legends (Speed, V/S, RNAV, etc.) could be more precise (this really is not an issue unless you inspect your panel with a macro lens); and,
(iv)    The non-use of D-shaped shafts on the rotary encoders.  If used, this would minimise the chance of any knob slipping on the shaft of an encoder.
(v)   The brightness of the digits displayed in the LCD's, although more or less even accross all characters, does show slight intensity differences.  This is caused by the positioning of the LED that sits behind each LCD. 

Pictures and Videos

I have not included many photographs in an attempt to keep the footprint of the article to a reasonable size. 

Several images can be viewed in the image gallery - SimWorld MCP Version 2.  I have posted several 'very average' photographs in this gallery in an attempt to show you the appearance of the panels.  Promotional images and videos are fine, but they are always professionally made to show the product in its best light.  You will also see a few images of OEM panels in the gallery to compare.

Below are three professionally made videos courtesy of SimWorld.

The panels displayed in the video accurately reflect the appearance, detail and functionality of the MCP and EFIS.  Equally, CANBUS is as straightforwrd to connect as shown in the video.

Photography

A quick word about photography.  Detailed and close-up photographs will always show unwanted blemishes.  The better the lens the more blemishes will become obvious.  It's important to remember that you do not fly the simulator looking through a magnifying loop, but view panels from a moderate distance.  Even OEM panels show inconsistencies when viewed with a macro lens :)

Titbits

This article has taken several months to complete.  Originally it was three times the length and it's taken some time to condense the information to a length that is readable without it being bound in a book!

Final Call

The price paid to own the SimWorld MCP and EFIS is not inexpensive, however, it is nowhere near the price demanded of a OEM Collins panel, or a panel used in a commercial simulator trainer.

SimWorld's use of liquid crystal displays in lieu of seven-segmented displays, the resistance felt when turning the various knobs that closely match the OEM panels, and the close attention paid to detail: for example, the small tabs beside the Flight Director switches, detailed display bezels, ambient sensor, and realistic push to reset barometer and minimums knobs, is what separates this MCP and EFIS from its competition. 

If you want the appearance of the MCP and EFIS to be as close as possible to the OEM equivalent, and want accurate functionality, then you should not discount the panels produced by SimWorld.

Wednesday
Apr262017

Altitude and Speed Intervention Explained 

The flight deck can be an extreme work environment, especially during the high-task descent and approach phase of the flight. 

Altitude and speed intervention were designed to allow pilots to easily and quickly change either the altitude or speed of their aircraft without re-programming the FMC, disengaging VNAV, or spending excessive time 'heads down'.

LEFT:  Altitude Intervention button on MCP.

The intervention buttons are strategically located on the MCP.  When the buttons are selected, the aircraft's altitude or speed can be altered quickly on ‘the fly’

In this article, I will examine the use of Altitude and Speed Intervention and demonstrate the use of these modes.  In a follow-on article, I will discuss alternate methods that can be used to change altitude whilst maintaining Vertical Navigation.  The reason for separating the two articles, is to avoid confusion that can develop between the different modes.

I recommend reading the appropriate section in the Flight Crew Operations Manual (FCOM) , Flight Crew Training Manual (FCTM) and the Cockpit Companion for a more thorough understanding. 

Furthermore, whether intervention modes function in the simulator will depend upon which avionics suite and FMC software version is used.  This article will deal only with ProSim-AR (ProSim737 avionics suite) which uses U10.8 A.  In this article I use the words altitude and flight level (FL) interchangeably.

Important Points:

  • Altitude and Speed Intervention are company options that may or may not be ordered at the time of airframe purchase.
  • Altitude and Speed Intervention will only operate when an a flight plan is active and VNAV is selected.
  • Altitude and Speed Intervention is more often used when a temporary change in altitude and/or speed is required with a return to the original altitude/speed imminent.  

MCP, VNAV & FMA Nomeclature and Displays

Prior to examining altitude and speed intervention, it may be fruitful to quickly discuss common words, that are used when describing the operation of VNAV and the MCP.

(i)       CONDITION means that a mode will become active only when a condition(s) occurs;
(ii)      ARM means that a mode is armed pending engagement;
(iii)     ACTIVE means the mode is engaged/selected;
(iv)     SELECT means to select or engage the mode (turn on); and,
(v)      DESELECT means to deselect or disengage (turn off) the mode.

An often misunderstood facet of the MCP is that the annunciators illuminate to indicate a particular mode is active.  This is not entirely correct, as the presence of an illuminated annunciator light does not always indicate whether a mode is active or not.

Table 1:  FMA displays observed when Altitude and Speed Intervention is engaged (click to enlarge).  Also (downloaded as a .pdf - click FMA displays).

For example, the VNAV annunciator on the MCP will remain illuminated when VNAV is either active or armed.  Furthermore, active modes that are not able to be deselected, do not display an illuminated annunciator.

To determine whether a mode is active or not, the Flight Mode Annunciator (FMA) should be consulted.  The FMA is located above the Primary Flight Display (PFD) and displays various alerts and status messages.  

Refer to Table 1 for a synopsis regarding the various displays that the FMA will generate when intervention is used.

 

 

Important Points:

  • A mode change highlight symbol (green rectangle) is displayed around the command name, in the Flight Mode Annunciator (FMA), whenever a mode has been armed and is about to become active.  The green rectangle will remain displayed for a period of 10 seconds.
  • It’s prudent to cross reference between the FMA, MCP and CDU to determine what mode is armed or active at a given time.
  • Altitude and Speed Intervention, when active, will take precedence over VNAV, although VNAV remains armed.

Scenario

The aircraft is flying at FL150 (15,000 feet) at 275 kias.  The FMC has a flight plan engaged (Company Route) that includes altitude and speed constraints (in the LEGS page of the CDU). 

In level flight, with the autopilot, LNAV and VNAV engaged, the following will be observed:

(i)     LNAV and VNAV will be active;
(ii)    The FMA will display MCP SPD / LNAV / VNAV PTH;  
(iii)   The annunciators on the MCP - LNAV, VNAV & CMD A/B will be illuminated;
(iv)   The speed window located on the MCP will be blank (no speed displayed); and,
(v)    LNAV/VNAV will be displayed in white text on the PFD.

LNAV will be controlling the lateral navigation of the aircraft while VNAV will be controlling the speed and altitude of the aircraft.

ATC request a decrease in speed from 275 kias to 240 kias.

Speed Intervention (SPD INTV)

Select (press) the SPD INTV button on the MCP.  The MCP speed window becomes active and displays the current speed of 275 kias.  Dial in into the speed window the new speed requirement of 240 kias. 

LEFT:  Speed Intervention button.

Notice the speed indicator display above the speed tape on the PFD has changed from 275 kias to the new speed of 240 kias.  Also note that the VNAV annunciator light on the MCP remains illuminated - in this case VNAV is active.  The aircraft will reduce its speed to 240 kias.

If you cross check with the cruise altitude in the CDU (CRZ ALT key/TGT SPD), the FMC will still indicate the original cruise speed of 275 kias.  This is because the speed is an intervention speed and, as such, will not have been updated in the FMC.

If you wish to stay at this speed (240 kias), you will need to manually change the cruise speed to 240 kias in the CDU.  However, in this case the reduction in speed is momentary, and ATC advise you to return to your original speed.  

Returning to Original Speed

Press the SPD INTV button (or unselect and reselect VNAV on the MCP).  Doing this, will return the speed to the original speed (275 kias).  It will also change the speed indication on the PFD from 240 kias back to 275 kias.  The MCP speed window will also become blank (no speed displayed). 

Important Point:

  • When SPD INTV is active, the FMA will display MCP SPD.  When SPD INTV is not active (deselected) the FMA will revert to FMC SPD.

Altitude Intervention (ALT INTV)

Altitude Intervention is slightly more sophisticated in comparison to Speed Intervention.  This is because, amongst other factors, the relationship changes when the aircraft is ascending or descending.

LEFT:  ALT INTV button on MCP.

In level flight, with the autopilot, LNAV and VNAV engaged, the following will be observed:

(i)     LNAV and VNAV will be active;
(ii)    The FMA will display FMC SPD / LNAV / VNAV PTH;  
(iii)   The annunciators on the MCP - LNAV, VNAV & CMD A/B will be illuminated;
(iv)   The speed window located on the MCP will be blank (no speed displayed); and,
(v)    LNAV/VNAV will be displayed in white text on the PFD.

ATC request a descent from FL150 to FL120.

DESCENT Using ALT INTV (descent from FL150 to FL120)

Dial into the MCP altitude window the new altitude (FL120). 

Notice the altitude display above the altitude tape on the PFD has changed from FL150 to the new altitude of FL120.   Also note that the VNAV annunciator light on the MCP remains illuminated - in this case VNAV is armed.  ALT INTV takes precedence over VNAV.  

LEFT:  CDU cruise page showing 12000 in scratch pad.  Selecting line select 1 left will update FMC.

Select (press) ALT INTV button on the MCP and the FMA will annunciate FMC SPD / LNAV / VNAV PTH.   The aircraft will descend at 1000 fpm (default) until FL120 is reached.  

If you cross-check the cruise altitude in the CDU (INIT PERF/PERF/CRZ ALT or CRZ key/CRZ ALT), it will display the original cruise altitude of FL150.  The FMC has NOT automatically updated to the lower altitude – this is normal and not a fault.  

By default, Altitude Intervention will always maintain a vertical descent at 1000 fpm. 

If you want to remain at FL120, you will need to manually update the cruise altitude in the FMC (INIT PERF/PERF/CRZ ALT), or (CRZ key/CRZ ALT) and press the EXEC key.  

Important Point:

  • When the CDU page is open on CRZ (CRZ key), it will display in the scratch pad any change to the altitude in the MCP.  This provides a ‘shortcut’ to insert the new flight level should it be desired to make it permanent.  All that is needed is to press the CRZ/CRZ ALT (in the CRZ page) and the FMC cruise altitude will be updated.  The altitude in the LEGS page will also be updated.

Returning to Original Flight Level

To return to the original flight level (FL150), dial into the MCP the previous flight level (FL150) and press ALT INTV.  The aircraft will ascend to FL150.  

Important Points:

  • The FMC will NOT be automatically updated to the lower altitude.  If desired, this will need to be done manually.
  • When returning to the original flight level, VNAV will not engage unless the original flight level (FL150) is manually dialled into the altitude window of the MCP.
  • ALT INTV takes precedence over VNAV.  The VNAV annunciator on the MCP will remain illuminated.  VNAV will be in armed mode.
  • To determine if VNAV is the active mode (or not) the FMA display must be consulted – not the annunciator light on the MCP.

ASCENT Using ALT INTV (ascent from FL120 to FL150)

The ALT INTV button operates a little differently when you ascend.   For a start, it automatically replaces (updates) the flight level (CRZ ALT) in the FMC.  It will also update the altitude in the LEGS page in the CDU. 

The FMA will annunciate  N1 / LNAV / VNAV SPD during the climb phase of the flight, changing to FMC SPD / LNAV / VNAV PTH when the new flight level is reached.  When climbing using ALT INTV, the thrust mode uses N1.

Important Point:

  • When a flight level of a higher altitude is dialled into the altitude window, and ALT INTV selected, the FMC will automatically be updated to the new flight level.

Considerations When Using ALT INTV

When using ALT INTV, several variables that relate to the altitude constraint (s) will change, depending upon whether you are in VNAV climb, cruise or descent.  Rather than rephrase what already has been written, I have scanned the appropriate page (below) from the Cockpit Companion written by Bill Bulfer.

Using ALT INTV and SPD INTV During a VNAV Approach Phase

ALT INTV is a very handy tool, if during an VNAV approach, the flight crew fail to change the altitude in the MCP to the next lowest altitude constraint.  

To demonstrate, the aircraft is flying a published STAR that will join an VNAV approach.  VNAV and LNAV are active and the flight plan has several altitude and speed constraints.  To meet these constraints, the crew must update the MCP altitude to the next lowest altitude (displayed in the LEGS page of the CDU) prior to the aircraft crossing the constraint.

If the crew fails to update the MCP, then the aircraft with transition from descending flight (VNAV PTH) to level flight (VNAV ALT).   In this situation a crew could engage LVL CHG or V/S,  however, doing so would deselect VNAV.  

A simpler solution is to change the altitude in the MCP window to the next lowest altitude constraint (or MDA) and press ALT INTV.  This will cause VNAV to descend the aircraft, at a variable descent rate, to meet the required constraint.   By using ALT INTV, the aircraft will remain in VNAV.

Additionally, SPD INTV is a straightforward way to control the speed of the aircraft during the approach while maintaining VNAV.  Company policy at some airlines insist that Speed Intervention be used approximately 2 nautical miles short of the Final Approach Fix (FAF).

Reliability of ALT INTV in Descent Mode - ProSim-AR

ProSim-AR (Version 1.49) exhibits difficulty in holding a lower altitude level when ALT INTV is used.

The Boeing system is designed in a way that once the V-Path is intercepted; the Flight Director cross hairs maintain the new altitude by pitch.  In ProSim-AR this pitch is often difficult to hold and a resultant pitching of the aircraft (up and down) occurs as the system attempts to hold the lower altitude.  When using LVL CHG or V/S this does not occur.  Note that this behaviour does not occur when using INTV ALT to ascend.

It is not certain if this behaviour is common only to my system or is more widespread; but a way to solve the issue is to either:

(i)   Use an alternate descent mode; or,
(ii)  Manually change the altitude values in the FMC (INDEX/PERF/CRZ ALT), or (CRZ key/CRZ ALT) and press EXEC.

By manually changing the cruise altitude to the lower altitude in the CDU, the aircraft will be stable (no pitching), because the FMC logic now commands the altitude, rather than the logic that commands ALT INTV.

The developers at ProSim-AR are continually tweaking these variables.  In future software releases (post version 1:49) this issue may well be rectified.

Final Call

During a flight there are many of reasons why you may need to alter speed and/or altitude; be it to divert around a localized weather or to abide by an Air Traffic Control.  Whatever the reason, often the changes are short-lived and a return to the original constraint imminent.

The use of Altitude and Speed Intervention, in addition to being a time saver, minimises  time spent in the ‘heads down’ position during the high-task descent and approach phase of a flight.

In this article, I have explained the intervention functionality of the Boeing 737 and provided workarounds should VNAV not operate as anticipated. 

This article has been re-written (for clarity) and updated from a post published in 2013.

Acronyms and Glossary

Annunciator - A push button to engage a particular mode – often has a light that illuminates
ALT INTV - Altitude Intervention

CDU – Control Display Unit (display screen and keyboard to input data into the FMC)
Flight Level – Altitude that the aircraft will fly at (set in FMC)

FMA – Flight Mode Annunciator

FMC – Flight Management Computer  (part of the Flight Management System)
FMS – Flight Management System
LNAV – Lateral Navigation

MCP – Mode Control Panel 

PFD – Primary Flight Display

SPD INTV - Speed Intervention

VNAV – Vertical Navigation

Friday
Apr072017

Alternate Use for OEM Rudder Pedal Circuit Breakers

The picture at left is of an OEM circuit breaker that has been removed from an OEM rudder pedal control mechanism.  The front plate of the control mechanism has several circuit breakers on the Captain and First Officer-side of the flight deck.

LEFT:  OEM circuit breaker switch.  The two connectors on the rear of the switch are very easy to connect to an interface card for push/pull functionality (click to enlarge).

Although connection of the circuit breakers, to the original functionality that was assigned to the switch in the aircraft, is not necessary (unless wanted), there is no reason why the circuit breakers cannot be used for additional functionality outside of the simulator environment.   Many enthusiasts have specially made panels that reside in the center pedestal to address such a need. 

The circuit breakers are basically an on/off push/pull switch.  Each switch can be easily wired to a standard interface card, such as a Pokeys or Leo Bodnar card, and then configured in ProSim-AR to a particular function.  If using FSUPIC, the functionality of the switch can be assigned to any on/off function.

For example, using FSUPIC (buttons) it is possible to assign each circuit breaker to a simulator function such as: pause, sim acceleration, jetway extension, etc.  The list is almost endless.

In my simulator, I have the Captain-side circuit breaker switches configured to simulator pause and simulator time acceleration.  These commands are readily accessible within the FSUPIC framework.

The circuit breaker switches are aesthetics, therefore, configuring the switches to regularly used commands is a way to minimize keyboard usage, and declutter the flight deck.

Friday
Mar242017

OEM Rudder Pedal Mechanism and Handles

The OEM rudder handle mechanisms have been sitting in storage for considerable time, and I thought it was time to add them to the simulator and replace the very poorly made and ‘cheesy’ reproductions that I was using.

LEFT:  OEM rudder handles and mechanism installed to Captain-side kickstand.  The stick shaker can be seen in the foreground (click to enlarge).

The rudder mechanism is not a small item that you can easily screw to the kickstand.  Each handle attaches to a 8-inch-long box, that houses the various circuitry, cabling and a dozen or so aircraft circuit breakers. 

Connection to the aircraft’s system is via two Canon plugs at the rear of the unit, while movement of the pedals forward or aft is facilitated by a long metal cable that connects to the rear of the handle.

The mechanism is not light-weight and weighs in at just over 1 kilogram.

The rudder handles do nothing other than add to the aesthetics of the simulator.  However, if wanted the various circuit breakers can be connected to an interface card (something I will not be doing).

LEFT:  Rudder handle mechanism (prior to cleaning).  The long metal cable that connects to the rear of the handle (enabling the forward and aft adjustment of the pedals) has been removed.  The white handle hangs loose and needs to be attached to the box using plastic fasteners (empty holes).  The black circular pull on/off circuit breakers can be seen below the white handle  (click to enlarge).

Installation to MIP

There are several methods that can be used to install the mechanism to the Main Instrument Panel (MIP).

If you are using an OEM MIP, then connection of the mechanism to the kick-stand is a matter of using the existing bolts and placement holes.  Fitment to a reproduction MIP is accomplished differently and depends upon how the MIP is constructed. 

I fabricated an aluminium cradle (saddle) that is attached by two nuts and bolts to the lower portion of the kickstand (under the kickstand out of sight).  The rudder mechanism slides into the cradle and a small screw holds the mechanism in the correct place.  A similar assembly could easily be made from wood and painted Boeing grey.

Read about an alternate use of the circuit breakers.

Wednesday
Mar082017

OEM B737 CDU Conversion - Introduction

One of the slower projects is the conversion of two B737 CDU units.  The two units were purchased from an aircraft scrap-yard in the US and were formally used in a Boeing 737 operated by United Airlines.  

LEFT:  Straight from United Airlines to me.  Two OEM CDU units.  The rear unit has already had its CRT display removed and is partially  'gutted' (click to enlarge).

The two CDUs came from an airframe of a B737-500, which in 2008 was retired along with other Boeing classics, due to United Airlines decision to adopt the Airbus A-320.

The rear of each unit has a chronometer showing the hours of use - one unit has 5130 hours while the other has 1630 hours.

The CDU presently used in the simulator is manufactured by Flight Deck Solutions (FDS) and although I have been pleased with its operation and reliability, there is little resemblance, other than appearance, to the OEM unit.

LEFT:  Detail of the keyboard and DIM knob.  Interestingly the DIM knob dims the actual screen and not the backlighting (click to enlarge).

The prominent difference is external build quality and the tactile feeling when depressing the keys on the keyboard; the keys don't wobble in their sockets, but are firm to press. 

There is also a strong audible click when a key is depressed.  Furthermore, the backlighting is evenly spread with each key evenly lit.

The OEM CDU is large and VERY heavy.  I was surprised at the weight - a good 6 kilograms.  Most of the weight is made up by the thick glass CRT display screen and other components that reside within the sturdy aluminium case.

LEFT:  The casing removed to show the electronic boards that are secured by lever clips.  Like anything OEM, the unit is made very well from solid components (click to enlarge).

Like the casing, the internal structure is also made from aluminium and has four rails to enable the electronic boards to be installed and secured into place. 

Whenever I look at anything OEM, I am amazed at the workmanship that has gone into producing the item; the CDU does not fall short in this area.

A myriad number of small screws hold together the aluminum casing that protects the internal components.  Not only screws are used, but also special miniature DZUS fasteners than enable the side of the casing to removed easily for maintenance.

Nomenclature

When discussing the CDU there are three similar terms that are often used interchangeably: CDU, FMC and FMS.  In this website, I use the terms CDU and FMC interchangeable which is not quite correct - let me explain.

LEFT:  Protective cover removed to show the main pin-out board, rear of the CRT display, power supply, and electronics.  These parts cause the CDU to be quite heavy.  The two Canon plugs  are just visible at the right of the picture enable connection to the aircraft. (click to enlarge to see detail).

The Control Display Unit (CDU) is the interface that the flight crew use to interrogate the data from the Flight Management Computer (FMC); it's basically a screen and keyboard.  The FMC in turn is but one part of a complex system called the Flight Management System (FMS).  The FMS is capable of four dimensional area navigation.  It is the FMS that contains the navigational database.

CDU vs. MCDU

The older units used in the classic airframes are always referred to as a CDU, while the NG units are called a MCDU.  M stands for multipurpose or multi-function.  Basically, the MCDU has a different key called a menu key.  This key, when pressed, accesses another layer of information that is not available in the earlier CDUs.

For those more military-minded, the CDU in military parlance is called a mission computer.

Aesthetic Differences

The CDU dates from 2008, therefore; it is not exactly identical to the CDU used in the Next Generation airframe, however, it is very close.

Main Differences - 500 series to NG

(i)    The dim knob is a slightly different shape;

(ii)   The display screen is rounded at the edges (the NG is more straight-edged);

(iii)   The absence of the horizontal white lines located on the inside edge of the display frame bezel; and,

(iv)   The display screen is different - cathode ray tube (CRT) verses liquid crystal display (LCD).

(v)   Two of the keys are different.  The NG has a menu and space key whilst the older CDUs have a DIR INTC and a blank key (no lettering on key). 

Other differences, not important in the simulator environment, are the colour of the fonts used; older units have black and white or green font while later model NG units use multi-coloured font.

To a purist, these differences are probably important, and if so, you will have to contend with a reproduction MCDU or pay an exorbitant amount for an NG unit. 

Software

The software used in the OEM CDU is not used in the simulator.  The CDU functionality is dictated by the avionics software (ProSim-AR) in use.  This is also true for the font type and colour.

LEFT:  Completely gutted.  All unnecessary and unusable electronic components have been removed.  These two CDU units will soon operate flawlessly with ProSim-AR and flight simulator (click to enlarge).

Converting the CDU

I am liaising with an Australian company that specialises in converting avionics components used in commercial flight simulators.  This company has had considerable experience converting B747 avionics and is keen to see if their expertise will similarly work with the B737.

In a second article, I will explain in more detail how the conversion was done, and examine some of the problems that needed to be resolved.  I also will discuss the mounting of the unit into the CDU bay. 

More photographs of the CDU are located in the image gallery.  Additional images will be added to the gallery in due course.

Glossary

OEM - Original Equipment Manufacture (aka reral aircraft part).