E-mail Subscription

Enter your email address:

Delivered by FeedBurner

Syndicate RSS

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!


Find more about Weather in Hobart, AU
Click for weather forecast






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

Journal Archive (Newest First)

Entries in Main Instrument Panel (7)


Original Equipment Manufacture (OEM) Boeing 737NG Lights Test Toggle Switch - Wired and Installed to MIP

The lights test is an often misunderstood but simple procedure.  The light test is carried out by the crew before each flight to determine if all the annunciators are operating correctly (illuminating).  The crew will toggle the switch upward to lights test followed by a routine scan of each annunciator on the overhead, center pedestal and instrument panel.  An inoperative light may preclude take off.

LEFT: OEM Lights Test Switch (before cleaning...) One switch comprising several switches (click to enlarge).

The lights test switch is a three-way switch which can be placed (and locked) in one of three positions; it is not a momentary switch.  Toggling the switch upwards (lights test) illuminates all annunciators located in the MIP, forward and aft overhead and fire suppression panel (wheel well annunciator may not illuminate), while the central position (BRT) provides the brightest illumination for the annunciators (normal operation).  Toggling the switch downwards activates the DIM function dimming the brightness by roughly half that observed when the toggle is in BRT mode.

Depending upon which manufacturer’s Main Instrument Panel (MIP) you are using, the toggle switch may not function this way.  For example, Flight Deck Solutions (FDS) provide a three-way momentary toggle which is not the correct style of switch.  You should not have to hold the toggle to light test as you make your pre-flight scan.  The real toggle switch in the Boeing 737 aircraft is not a momentary switch.

Anatomy of the Toggle Switch

The OEM Light Test switch may appear to be a ‘glorified’ toggle switch with an aviation-sized price tag; however, there is a difference and a reason for this high price tag.  

The switch although relatively simple in output, encompasses 18 (6+6+6) high amperage individual switches assigned to three terminals located on the rear of the switch.  Each terminal can be used to connect to a particular aircraft system, and then to each other.  This allows the toggle switch to turn on or off multiple aircraft systems during the light test. 

The purpose of these multi-terminals is to allow the toggle switch to cater towards the high amperage flow of several dozen annunciators being turned on at any one time during the lights test, in addition to generators and other aircraft systems that are not simulated in Flight Simulator.  In this way, the switch can share the amperage load that the annunciators draw when activated during the light test.

The switch can control the annunciators (korrys) for the MIP, forward overhead, aft overhead, fire suppression panel and any number of modules located in the center pedestal.  

Terminals, Interfacing and Connection

To determine the correct terminals to be used for the light test is no different to a normal toggle-style switch. 

LEFT:  OEM Lights Test switch.  The appearance of the OEM switch is not dissimilar to a normal toggle switch; however, the functionality is different in that there are a number of terminals on the rear of the switch to allow multi-system connection (click to enlarge).

First, ascertain which of the six terminals correlate to the switch movement (toggle up, center and down).  The three unused terminals are used to connect with other systems in the real aircraft (not used in Flight Simulator).

To determine the correct terminals for wiring, a multimeter is set to conductivity (beep) mode.  Place one of the two multimeter prongs on a terminal and then place the other prong on the earth (common) terminal.  Gently move the toggle.   If you have the correct terminal for the position of the toggle, the multimeter will beep indicating an open circuit. The toggle switch does not require a power source, but power is required to illuminate the annunciators during the lights test.  

For an overview of how to use a multimeter see this post - Flight Deck Builders Toolbox - Multimeter.

Daisy Chaining and Systems

Any annunciator can be connected to the light test function, and considering the number of annunciators that the light test function interrogates, it is apparent that you will soon have several dozen wires that need to be accommodated. 

Rather than think of individual annunciators, it is easier to relate a group of like-minded components as a system.  As such, depending upon your simulator set-up, you may have the MIP annunciators as one system, the overhead annunciators as another and the fire suppression panel and modules mounted in the center pedestal as yet another.  If these components are daisy chained together (1+1+11+1+1=connection), only one power wire will be required to be connected at the end of the array.  This minimises the amount of wire required and makes connection easier with the toggle switch.

Two Methods to Connect to the Switch

There are two ways to wire the switch; either through the flight avionics software (software-based solution), or as a stand-alone mechanical system.  There is no particular benefit to either system.  The software solution triggers the Lights Test by opening the circuit on the I/O cards that are attached to the computer, while, the mechanical system replicates how it is done in the real Boring aircraft.

Switch in-line (software connection using ProSim737)

The on/off terminal of the toggle switch is connected to a Leo Bodnar card or other suitable card (I use a Flight Deck Solutions System card), and the card’s USB cable connected to the main computer.  Once the card is connected, the avionics suite software (ProSim737) will automatically register the card with to allow configuration.  Depending upon the type of card used, registration of the inputs and outputs for the card may first need to be registered in Windows (if using Windows 7 type into the search bar joystick and select calibration).

To configure the toggle switch in ProSim737, open the configuration/switches tab and scroll downward until you find the lights test function.  Open the tab beside the name; select the appropriate interface card (Leo Bodnar card) from the drop down menu and save the configuration.  

ProSim737 will automatically scan the interface cards that are installed, and if there is a card that has a power requirement, such as a Phidget 0/16/16 card (used to convert OEM annunciators, modules and panels), the software will make a connection enabling the lights test to function.

Considering the connection is accomplished within the ProSim737 software, it stands to reason the lights test will only operate when ProSim737 is open.

To illuminate the annunciators when the switch is thrown, a 28 volt power supply will need to be connected to the annunciators either separately or in a daisy chain array.

Stand-alone (mechanical connection)

The second method, which is the way it is done in the real aircraft, is to use an OEM 50 amp 6 pull/6 throw relay device. 

Depending upon the type of relay device used (there are several types), it may be possible to connect up to three systems to the one relay.

LEFT:  OEM aviation relay mounted in center pedestal (click to enlarge).

Lights Test Busbar

Although the Lights Test switch has the capacity to connect several systems to the switch itself, it would be unmanageable to attempt to connect each panel to the lights test switch.

To solve this issue a centrally-placed aviation-grade relay has been used in association with a busbar.

A benefit of using an OEM relay and busbar is that the relay acts as a central point for all wires to attach.  The wires from the various systems (panels, korrys, etc) attach to the busbar which in turn connects to the various posts on the relay.

The relay will then open or close the relay enabling power to reach the annunciators (via the busbar) when the switch is positioned to Lights Test.

The stand-alone system will enable the lights test to be carried out without ProSim737 being open.

Although the relay is not large (size of a small entree plate), it can be problematic finding a suitable area in which to mount the relay where it is out of the way.  A good location is to mount the relay inside the pedestal bay either directly to the platform floor or to a wooden flat board that is screwed to the lower section of the center pedestal.

Using the DIM Funtionality (toggle thrown downwards)

This post has only discussed the lights test.  The DIM switch is used to dim the OEM annunciators (korrys) for night work.  Another article explains the DIM functionality.

BELOW: Two very basic flow diagrams provide an overview of the two methods of connection (click diagrams to enlarge).













OEM Brackets to Secure Gauges and Modules to Boeing 737 MIP

Original Equipment Manufacturer (OEM) parts usually attach to the infrastructure of the flight deck by the use of DZUS fasteners.  The easy to use fasteners allow quick and easy removal of panels and modules.  But what about the gauges that are used in the Main Instrument Panel (MIP); for example, the yaw dampener, brake pressure and AFDS module.

LEFT:  Take your pick – brackets for different sized modules and gauges.  The brackets when tightened provide a snug and secure fit for any OEM gauge or module.

These items do not use DZUS fasteners for attachment to the MIP; rather they are inserted into the MIP from the front and secured from behind by a specially designed bracket.  The different sized brackets are made from lightweight aluminum and are designed to fit particular gauges and modules.   Each bracket incorporates, depending on the style, a number of screws.  These screws are used to loosen or tighten the bracket. 

The gauge is inserted into the MIP from the front.  The bracket is then placed over the gauge from behind the MIP and tightened by one or more of the resident screws.  The screws cause the bracket to clamp tightly to the shaft of the gauge and ‘sandwich’ the MIP between the flanges of the gauge and the edge of the bracket.  Once fitted, the Canon plug is then re-attached to the gauge.

LEFT:  Selection of gauges.  Note the flange on the forward part of the yaw dampener and brake pressure gauge (nearest glass) Click image to enlarge.

Of interest is that some brackets have been designed to fit the differing thicknesses between MIPs.  By turning the bracket end on end the appropriate thickness of the MIP is selected.  

As mentioned above, the brackets are designed to fit specifically sized and shaped gauges and modules; therefore, it is important to purchase the bracket that fits the gauge you are using.  There are several different sized brackets on the market that are used in the Boeing 737 classics and NG airframes.  The 'NG' for the most part incorporates identically sized gauges as the classics, so a bracket is not necessarily NG specific.

One of the benefits in using the OEM brackets is that they are designed for the purpose, are very easy to install, and facilitate the quick removal of a gauge or module should it be necessary.

In the next post we look more at flight training and discuss corsswind landings.


Main Instrument Panel (MIP) - Seeking Accuracy in Design

I’ve posted this image of the Main Instrument Panel (MIP) of the B737-800NG to briefly examine a few of the differences between a real MIP and a reproduction MIP.   Although a reproduction MIP may appear identical to the real item, there can be subtle differences. 

Let’s look at a few of these differences using the photograph as a reference.

LEFT:  MIP (OEM) from 737-800 NG (click image to enlarge).

Bezel. The bezel is the frame that surrounds the display units (DUs).  In the real aircraft the bezel forms part of the display unit, which is why the bezel breaks open in the lower area; to allow access to and removal of the unit. 

If you carefully look you will note there are no screws that hold the bezel in place to the MIP.  Quite a few manufactures use Phillip head screws in each corner of the bezel to attach the bezel to the MIP

In the real aircraft the bezel is made from machined aluminum.  

Landing Gear Lever.  The real aircraft has a smaller than often seen landing gear knob (the translucent knob).  Further, when the landing gear is in the down and locked position, the red trigger located on the gear shaft completely recesses between the two half-moon protectors. The trigger also is spring-loaded allowing the gear lever to be unlocked by depressing the trigger in specific conditions.

Fuel Flow Reset Switch. The real aircraft incorporates a switch/toggle with a larger defined and bulbous-looking head, rather than a standard-style toggle most manufacturers use.  The OEM toggle is also very specific in operation (3 way pull & release). 

The knobs used on the MIP. These knobs are called general purpose knobs (GPK) and it's uncommon for a reproduction knob to look identical to an OEM knob.  OEM knobs present with curved rather than straight edges and have the grub screw located in a different position.  Many reproduction knobs lack this detail and have the grub screw located at the rear of the knob. 

Furthermore, OEM knobs have an inside metal shroud (circular metal retainer) and a metal grub screw thread, both important to ensure operational longevity of the knob; reproduction knobs usually do not have this.  The shroud can be important as it increases the longevity of the knob as it stops the acrylic from being worn down over time with continual use.

The NG also has a backlit black coloured line that runs adjacent to a translucent line on the front of the knob; at night this line is backlit. Most of the replica knobs have a black line which is a transfer (sticker) that has been hand applied to the knob.  Stickers and transfers over time often lift, especially at the ends and hand application is often haphazard with some transfers straight and other a little off center.

In my opinion, any high end MIP of considerable financial outlay should have appropriate knobs that are high fidelity and replicate the OEM item.

If you look carefully at the photograph you will note that the knobs have curved edges and the Used Fuel Reset Switch has a bulbous appearing toggle.

I am currently writing a short article on "knobs" which will be published in the near future.

Annunciators (Korrys).  The annunciators on reproduction MIPs use LED technology, are only lights/lamps/indicators, and may exhibit an incorrect colour hue in contrast to the OEM part.  Reproductions can also be lacking with regard to the legend, as OEM legends are lazer cut and well-defined. 

Annunciators in the real aircraft are illuminated by 28 Volt bulbs contrasting the low brightness LEDs seen in reproduction Korrys - this alone can make a huge difference in aesthetics.  Finally, the push to test function seen in the real item, to my knowledge, is lacking in reproductions.

  • Note that some newer airframes may use LEDs in favour of bulbs.

Colour.   Boeing grey (RAL 7011), has a specific RAL colour number; however, rarely is every MIP or aviation part painted exactly the same grey colour; there are sublime differences in shade, colour and hue.  Inspect any flight deck and you will observe small colour variations.  Type RAL 7011 into Google and note the varying shades for a specific RAL number.

Dimensions & 1:1 Ratio.  High-end MIPs for the most part are very close to the correct 1:1 ratio of the real item and differences, if noticeable, are marginal.  But, less expensive MIPs can have the incorrect dimensions.  It's not only the overall dimensions that are important, but the dimensions of the spaces, gaps and holes in the MIP that allow fitment of the various instruments and modules.

Whilst this may not be a concern if you're using the stock gauges, etc that came packaged with your MIP, it can become problematic if you decide to use OEM parts.  There is nothing worse that using a Dremel to enlarge a hole in a MIP that isn't quite the correct size.  Worse still, is if the hole in larger than it should be.

Musings - Does it Matter ?

If everything fits correctly into whatever shell you're using, then a small difference here and there is inconsequential.  However, if you are striving for 1:1 100% accuracy then it's essential to know what’s reproduced factually and what is fiction (Disneyland). 

I have only mentioned differences based on what can be seen in the photograph.  There are additional nuances that differ between MIP manufacturers. 

System Simulation is a Priority

As I move more into my project, I realize that many items available in the reproduction market are not identical to the real aircraft; a certain artistic license has been taken by many manufacturers.  This said, while it's commendable to have an exact reproduction of a flight deck, keep in mind that a simulator is primarily a simulation of aircraft systems.

Of course this doesn't mean you throw everything to the wind aesthetically.  To do so would mean you would have an office chair, desk and PMDG in front of you.  Aesthetics are important as they stimulate by visual cues, a level of immersion that allows the virtual pilot to believe they are somewhere other than their own home.

If you inspect real-world flight simulators used by aircraft companies, you will quickly note, that many of the simulators do not replicate everything or strive to have everything looking just like the real aircraft.  Simulators are designed for training and whilst a level of immersion must be apparent, replicating aircraft systems takes priority.

B 737-800 NG Project Status

The overheads are my main concern at the moment; however, I am also working on replacing as much as possible on the Main Instrument Panel with OEM items.  Once completed, all that will remain is the FDS MIP skeleton and a few bits and pieces.  A decision has yet to be made concerning replacement of the glareshield.

The question is probably asked - why not replace the FDS MIP with a OEM MIP.  Whilst this is possible, a NG style OEM MIP apart from being difficult to find and expensive, would require consdierable fabrication to use in a Flight Simulator.  It's far easier to use a commerical MIP as a template and then replace as much as possible with OEM items.

As the MIP project progresses updates will be made.

Acronyms & Glossary

Annunciator - A single coloured light or group of lights used as a central indicator of status of equipment or systems in an aircraft. Usually, the annunciator panel includes a main warning lamp or audible signal to draw the attention of operating personnel to the annunciator panel for abnormal events or conditions.  To annunciate means to display or to become audible.  Annunciators are often called Korrys; Korry is a manufacturer of annunciators.
FDS - Flight Deck Solutions
Korry – See Annunciator.  A brand of annunciator used in the Boeing 737 airframe.
Legend - The plastic lens plate that clips to the annunciator.  the legend is the actual engraved writing on the lense.
MIP - Main Instrument Panel.
OEM - Original Aircraft Manufacture (aka real aircraft part).
RAL - International colour matching system.


RMI Knobs Installed to Main Instrument Panel (MIP)

Following on with the theme from my last post, I have replaced the two tear-drop style RMI knobs supplied by Flight Deck Solutions on their Main Instrument Panel with two replacement knobs.

LEFT:  RMI knobs fitted to the RMI frame of the MIP.  ProSim737 allows for a number of differing style RMI gauges to be displayed - framed and frameless (click to enlarge).

The replacement knobs are highly detailed reproductions of the original B737-800 RMI knobs.  I would like to have used genuine knobs; however, as they are usually attached to an RMI gauge, finding the knobs alone at a reasonable price would be a difficult if not an impossible task.

The knobs have been individually sculptured using clear ABS plastic while the front plate is made from clear acrylic.  The knobs are then painted in the correct Boeing grey colour and the black and white stenciling applied directly to the front of the knob.  The knobs can be easily backlit using an LED, although I have yet to do this.  The sizing of the knobs can be determined from information supplied by EHC Knobs located in Farmingdale, New York.

Stand-by Instruments - RMI Gauge

There is no "stock standard" concerning how the stand-by instruments are displayed with a reproduction MIP.   You may have the capacity to include real stand-by gauges (lucky you…) or reproduction solid state gauges manufactured by Flight Illusion, Sim Kits or similar. 

Flight Deck Solutions (FDS) have choosen to use a single LCD monitor to cover the EICAS and stand-by gauges.  Fly Engravity use solid state Flight Illusion gauges. 

Looking Pretty.....

At the moment the knobs have not been interfaced and just sit there “looking pretty”

In the future, I may interface the knobs by installing micro-buttons and/or a micro- rotary behind each knob.  The knobs will then be connected to an interface card.  However, at the minimum this requires cutting the MIP to create additional space for the location of the micro-switches – something I do not want to contemplate at the moment.  If given a choice, procuring a genuine OEM RMI gauge would be my preferred option.

In the interim, the RMI Switch Assembly panel discussed in my earlier post will suffice.

The RMI knobs are now replaced with OEM knobs from a B737-800 that are fully functional.


MIP – Main Instrument Panel
RMIRadio Magnetic Indicator.  The gauge that displays VOR and ADF mode.  Part of B737 NG stand-by instrument cluster


Replacement Sidewalls for FDS MIP

I have mentioned in my earlier post discussing the Main Instrument Panel (MIP) from Flight Deck Solutions, that the unit was a little wobbly due to the thin metal used on the side-walls.  Whilst this is not a huge problem and certainly not an issue when the MIP is "locked" into a shell, it does pose a minor issue when used without a shell.   Therefore, I decided to fabricate some replacement side stands for the MIP from 3mm aluminium sheet.

AutoCad was used to copy the dimensions of the original FDS sidewalls, and a lazer cutter cut the aluminium sheeting to the exact measurement.  Using a standard pipe bender, I bent the sides out at 45 degrees to allow slightly larger spacing for the rudder pedals.  I also increased the surface area of the metal which is used to attach the MIP to the platform, this ensures a more stable and secure attachment point for the MIP.  To replicate the MIP side-walls exactly, I TIG welded the narrow section that folds behind the stand.

Currently the aluminum is unpainted.  At some stage in the near future I'll either have the two units powder-coated in Boeing grey to match the colour of the MIP, or more than likely I'll prime and paint them myself.

The MIP is now very stable and does not wobble at all.