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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.


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).


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

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Entries in B737-800 Flight Simulator (45)


Book Review - Touch and Go Landings by Jonathan Fyfe

I read Jonathan Fyfe’s initial on-line tutorial ‘Flying the Circuit in the B737’ some time ago.  I was impressed with Fyfe’s writing style which is succinct and easy to read.  As a result I was keen to review his latest publication ‘Touch and Go Landings in the 737 NGX’ which is a follows on from his original tutorial.


The book (here on referred to as a guide) is paperback A5 in size, is 135 pages in length and has been printed in colour.  The guide is printed on quality paper and has a glossy-style plastic cover.

As the title of the text eludes, the guide examines in-depth all the aspects needed by a flight crew to successfully fly the Boeing 737 in a standard circuit, including crosswind approaches, missed approaches, engine out operations and rejected takeoffs.   Although the title of the guide may not appear substantive, the guide addresses nearly everything required to conduct a manual/part automated takeoff and landing.


I was surprised at the volume of information that Fyfe has managed to place in the guide; initially I thought the content appeared rather thin; however, closer examination revealed a wealth of information covering both systems and procedures.  This is in addition, to pictures that demonstrate correct landing technique and diagrams that are well-presented and clear. 

Derated takeoffs, assumed temperature thrust reduction, descent profiles, runway markings, drift calculations and aircraft systems data, which include: spoiler use, flap schedules, flight deck warnings, use the autothrottle and controlled wheel steering – too mention a few, are explained.

Well-written Framwork

Fyfe’s ability as a flight instructor and educator comes to bear in the nature of how he explains the various procedures.  He does not ‘parrot’ procedures, the FCOM or FCTM, but rather adds to this information by his ability to be able to shape the material into a parcel that is easily understood.

Many of the more complicated aspects, such as crosswind approaches, the effects of wind and the balanced field length are explained more clearly by the use of coloured diagrams.  This translates to a guide that is very easy to comprehend allowing the reader to easily apply the information when flying their simulated aircraft. 


The guide is divided into three primary lessons which encompass: standard circuits, missed approach and crosswind circuits and engine out/asymmetrics. 

Each section has three sub-sections.

(i)         Groundwork;
(ii)         Systems; and,
(iii)        Air Work.  

In groundwork, the theory and methodology for the upcoming lesson is primarily discussed, along with a lesson briefing.  In Systems, the focus is towards pertinent information that relates to the lesson; for example, flap positions, warning horns, autothrottle, N1 calculations and FMA annunciations.  In Air Work, a tutorial-style lesson is presented, in which Fyfe explains the necessary procedures to complete the lesson.   The student (you) can set-up their simulator to mimic the same conditions that Fyfe is flying.  This allows the student to self-evaluate their ability. 

All the sub-sections, but especially so in air work, are augmented by several screenshots depicting aircraft positions and instrument readings.

The lessons revolve around the use of the Boeing 737 NGX produced by Precision Manuals Development Group (PMDG) and Flight Simulator 10 (FSX); however, the information can easily be applied to any simulated B737 that is using a professional avionics suite, such as ProSim737, Sim Avionics, Project Magenta, I-Fly, etc. 

Some enthusiasts may find the guide lacking in that it does not attempt to explain or demonstrate the various automated-style approaches that the B737 is capable of (ILS, VOR, IAN, RNAV, etc.).  Nor does it cover off on climbing to altitude, descent or cruise. Although this knowledge is important, it is not relevant to touch and go takeoffs and landings.

Peer Review

The amount of information, especially on the Internet concerning flying the Boeing 737 aircraft is voluminous; however, a  caveat must be issued in that much of this information has not been peer reviewed and in many instances is not correct.  Although there are numerous monographs available that deal with the Boeing aircraft, these texts are usually very expensive and have not been written with the lay person in mind; often they are technical and assume an inherent level of prior knowledge.  Likewise, the FCOM, FCTM are certainly very helpful documents; however, they have been written for trained flight crews and their method of explanation is often clouded without prior knowledge and experience in aircraft systems. 

In this guide, Fyfe has succeeded in translating much of this information in a concise way that is easy to read and comprehend.

Why Touch and Go - Why Are They Important

Some enthusiasts may wonder why knowing how to accomplish a touch and go landing is important.  After all, surely it is more important to understand the intricacies of a full stop landing using one of the several approach types that the B737 is certified to carry out, and be able tom land the aircraft following the procedure outlined in the approach chart.

LEFT: FedEx - steep climb out after touch and go (photograph copyright Bob Wood).

Flying circuits and performing touch and go landings will vastly improve your airmanship, as a good majority of what is required during touch and go landings can be applied to other aspects of flying the B737.  Additionally, the touch and go procedures are consolidated into a time-dependent envelope in which everything occurs relatively quickly.  If a virtual flyer is competent in carrying out a touch and go landing, then it is a very easy transition to use one of the more advanced approach formats.

Final Call and Score

‘Touch and Go Landings’ is aimed at the novice to intermediate virtual pilot who wishes to learn the correct procedures first time around; advanced users will also benefit by not second guessing procedures they are presently using.   This said, there are many ways to fly the Boeing 737 aircraft, and often the method chosen depends on the flight crew, environmental constraints and the airline policy. 

It is important to realise that the guide is not a glorified tutorial written by an aviation enthusiast, but rather is a thoroughly researched and well written and easy to read text, that provides a pallet of information and comprehensive procedures that are relevant to flying the B737.  The guide not only provides a framework of what to do, but it also explains the how and why.

To read more about the guide or to purchase a copy, navigate to the author's website at www.jf737ngx.wordpress.com. Otherwise, copies can be purchaed directly from Amazon.

The current retail price is $24.95. 

Introductory discount coupons are available, for a limited time, at Jonathan Fyfe’s website.

I have given the guide a score of 9/10.


I have not received remuneration for this review; however, I was provided a guide ‘gratis’ to read.  The review is solely my opinion. 

Glossary and Acronyms

FCOM – Flight Crew Operations Manual (Boeing airline specific document)
FCTM – Flight Crew Training Manual (Boeing airline specific document)
FMA – Flight Mode Annunciations


B737 Original Equipment Manufacture RMI Knobs Fully Functional

In two previous posts, I documented the installation of two home made reproduction RMI knobs, and a OEM RMI switch assembly (ADF/VOR).  The switch assembly was mounted in the center pedestal.  The purpose of the switch assembly, which originally was used in a Boeing 727 airframe, was to provide an easy method to switch between ADF and VOR as the two knobs mounted on the RMI were non-functional.

RMI Knobs Installed to Main Instrument Panel

RMI Switch Assembly

With the acquisition of OEM RMI knobs, the next step was to implement the functionality of these knobs by installing micro-rotary switches to the RMI frame behind each knob.  The non NG compliant RMI Switch Assembly panel would then be superfluous and removed from the center pedestal.

Installing the Micro-rotary Switches to the RMI Frame

The first step was to remove the RMI frame from the MIP and enlarge the holes that the RMI knobs reside.  This is to allow the installation of the two micro-rotary switches. To do this, a Dremel rotary tool was used.   

To enable the wires from the rotary switches to be routed neatly behind the RMI frame, a very narrow trench was cut into the rear of the plastic frame.  It is very important that this task is done with due diligence as the RMI frame produced by Flight Deck Solutions (FDS) is manufactured from ABS plastic and not metal – if the cut is too deep or too much pressure is applied to the Dremel, then the frame will be damaged.

The wires from the the RMI knobs are then laid inside the earlier cut trench and aluminum-based tape is  applied over the wires.  This ensures the wires are secure and do not dislodge from the RMI frame.

The micro-rotary switches used in this conversion are 1 cm in length (depth); therefore, to use these rotaries successfully you will need to have a certain amount of airspace between the rear of the RMI frame and front of the computer screen (central display unit).  Whether there is enough room to facilitate the installation of the rotary switch, will depend upon the manufacturer of the MIP and RMI frame – some manufacturers have allowed a centimeter or so of space behind the RMI frame while others have the frame more or less flush to the center display unit screen.  If the air space is minimal, the rear of the rotary may rub against the display unit.

There are several methods that can be used to secure the rotaries to the RMI frame.  By far the easiest is to enlarge the hole in the RMI frame to a diameter that the rotary can be firmly pushed through the hole and not work its way loose.  Another method, more permanent, is to glue the rotary inside the hole.  No matter which method used, the rotary must be secured inside the hole otherwise when the RMI knob is turned the rotary will swivel within the hole.

LEFT:  RMI frame with OEM knobs - albeit on the wrong side :).  Note the metal sleeve and grub screw in the knob (click to enlarge).

Once the rotaries are installed to the frame, the OEM knobs are carefully pushed over the rotaries and the metal grub screws on the knob tightened.  One of the benefits of using OEM knobs is that the inside of the knob has a metal sleeve which ensures that the knob will not wear out and slip with continual use – reproduction knobs rarely are manufactured with an inside metal sleeve.

Interface Card and Configuration

To enable functionality, the wires from the rotaries are carefully threaded through the MIP wall and routed to an interface card; A PoKeys card, mounted in the System Interface Module (SIM), has been used.  It is not necessary to use a large gauge wire to connect the rotaries to the interface card.  This is because the electrical impulse that travels through the wire is only when the RMI knob is turned, and then it is only for a scond or so.  

The functionality for the RMI knobs is configured within the ProSim737 avionics suite in the configuration/switches area of the software.

Micro-rotary Switches

There are several micro-rotary switches available in the market.  This conversion uses A6A sealed rotary DIP switches; they are compact and inexpensive.

When selecting a rotary, bear in mind that many rotaries are either two, three or four clicks in design.  This means that for a 90 degree turn, such as required when altering the RMI from VOR to ADF, the rotary will need to travel through a number of clicks to correspond with the visual position of the switch.

The A6A type mentioned above are a two click type.  The first click will change the designation (VOR to ADF or back again), however, for realism two clicks are made (90 degree turn).  At the time of the conversion it was not possible to find a small enough rotary that was one click.  Despite this shortcoming, the physical clicks are not very noticeable.

This conversion is very simple and is probably one of the easiest conversions that can be done to implement the use of OEM knobs.  There is minimal technical skill needed, but a steady hand and a good eye is needed to ensure the RMI frame is not damaged when preparing the frame for the installation of the two rotary switches.


This  conversion uses two OEM RMI knobs and rotaries to interface with the standard virtual RMI gauge provided within the ProSim737 avionics suite.  Converting an OEM RMI gauge for standalone operation is possible and has been accomplished by other enthusiasts; however, whether a full RMI conversion can be done very much depends upon your particular simulation set-up.

If a OEM RMI gauge is installed, there may be a spacing issue with the other alternate gauges.  In particular, the Integrated Standby Flight Display (ISFD) will require a smaller dedicated display screen.  Likewise, the EICAS display screen will need to be smaller so as to fit between the RMI gauge and the landing gear assembly.  Also, an extra display port will be required for the computer to read the ISFD display screen. 

Certainly, a complete conversion of a RMI gauge is the best way to proceed, if you already own a OEM RMI unit, and if the set-up problems are not too difficult to overcome.


MIP – Main Instrument Panel
OEM – Original Equipment Manufacturer
RMI – Radio Magnetic Indicator


Boeing Nut Cracker - Loosening Stab Trim Wheel Nuts

Any industry has tools that have been designed for a specific task – whether it is for automotive, construction or aviation.  

Specialist tools enable a particular job to be accomplished quickly and effectively with the minimum of fuss.  More importantly, damage to a part is lessoned when using a specialised tool. 

LEFT: Boeing Nut Cracker - two raised lugs fit firmly into their opposite number to enable the stab trim wheel nut to be easily loosened or tightened (click to enlarge).

A person who makes tools usually has a trade certificate and those who are gifted in this area are called boiler makers; a gifted boiler maker can literally

make anything.

Stab Trim Wheel Nut

The stab trim wheels have two nuts that hold the wheels in place - one on each side of the throttle quadrant.  When attempting to remove the nut it is a good idea to use a tool, as the nut can be easily damaged (burred).

LEFT:  Captain-side stab trim wheel nut showing recessed indentations on the nut.  The screwed rod (tip showing in photograph) is ~40 cm in length and is inserted through one of the  trim wheels, through the throttle quadrant, and is then secured by the unique nut on the opposite trim wheel (click image to enlarge).

The nut has two shallow indentations each side of it to enable it to be firmly tightened. 

Often the nut is over-tightened by the continual rotation of the trim wheels, or by an overzealous technician applying more force than they should.  If the nut has been over tightened, removing the trim wheels can be problematic. 

A common man’s blade screwdriver can be used to loosen the nut, by applying the blade to one side of the two indentations, grasping the trim wheel and turning the driver.  But, do not be surprised if the recessed indents are damaged, the screwdriver slips and scratches something, or worse you end up with the blade of the screwdriver through your hand!

Boeing Specialised Tool

Boeing technicians use a specialised tool to loosen and tighten the nuts that hold the trim wheels in place – no doubt it also has a special name (?).  This tool, like all specialist tools is expen$ive, and more so because it is used in the aviation industry. 

I explained the problem to a friend of mine who like a ‘genie in a bottle’, designed and made this small tool for me.  It is not fancy or technical, but it does the job it has been designed to do especially well – every time. 

The tool is made from aluminium with two raised indentations that fit into the two recessed indentations on the trim wheel nut.  A simple shaft placed through a drilled hole in the stem of the tool enables the user to apply enough leverage to 'crack' all but the most resistant of trim wheel nuts. 

Caution - Removing the Trim Wheels from the Main Shaft 

Whenever the trim wheels have to be removed from the throttle quadrant, it is very important not to dislodge the cogs by pushing or pulling them through the throttle unit.  This is relatively easy to do as often the trim wheels adhere to the cog.

LEFT:  The heavy duty cog wheel that the trim wheels are secured to.  When removing the trim wheels it is very important not to dislodge the cog as the bearings on the inner side of the cog will fall out of alignment (click image to enlarge).

Attached to the cog and shaft are several bearings, which if dislodged, will fall out of alignment.  The bearings are important to the correct functioning of the trim wheels and it is very difficult to put the bearings back into alignment after they have fallen out of place.

When removing the trim wheels, carefully 'jiggle' the trim wheel until it works its way loose of the cog - never forcefully pull the trim wheel outwards as the cog may dislodge along with the wheel.  Furthermore, be mindful that when you remove one of the trim wheels the other may rotate forward or backwards due to centrifugal force.

Before replacing the trim wheels, to help avoid the wheel from sticking to the cog, apply an amount of grease to the cog teeth.


OEM Annunciators Replace Reproduction Korrys in Main Instrument Panel (MIP)

A task completed recently has been the replacement of the reproduction annunciators located on the Main Instrument Panel (MIP) with OEM annunciators. 

LEFT:  There can be little doubt that OEM annunciators shine far brighter than their reproduction counterparts.  The korrys are lit during the lights test.  Flaps gauge yet to be installed.   (click to enlarge).

The reason for changing to OEM annunciators was several-fold.  First, anything OEM is superior to a reproduction item.  Second, I wanted to reproduce the same korry annuciation  lighting observed in the OEM panels in the center pedestal, fire suppression panel, and when fitted, the forward and aft overhead panels.  Additionally, it was also to enable the push-to-test functionality and to provide better illuminance during daylight.  Certain reproduction korrys are not that bright when annunciated and are diffiucult to see during the day.

This post will explain the anatomy of the annunciators that are fitted to the Main Instrument Panel (MIP).  It will also detail how the annunciators are wired and configured in ProSim737, and provide incite into some of the advantages and functionality that can be expected when using OEM annunciators.

Anatomy of a Annunciator

An annunciator is a light which is illuminated when a specific function occurs on the aircraft.  Annunciators are often called by the generic name of a ‘korry’, as korry is the registered trademark used by a company called Esterline that manufactures annunciators.  

There are two types of annunciators used in the Boeing aircraft, the 318 and the 319 which are either a Type 1 circuit or a Type 2 circuit.

The 318 and 319 korrys are not interchangeable.  Each Korry has a different style of bulb, differing electrical circuits, and a different method of internal attachment (captive hex screw verses two blade-style screws).  The only similarity between the 318 and 319 korrys is that the hole needed to house the korry in the MIP is identical in size - .440” x .940”.  

The circuit type refers to the electrical circuit used in the Korry.    Both circuit types require a ground-controlled circuit to turn it on, however, Type 1 circuits are ground-seeking while Type 2 circuits are power-seeking.    Typically, a Boeing 737 uses Type 1 circuits.

Annunciators have five parts that comprise:

(i)     The lower assembly and terminals (usually four terminals in number);
(ii)    The upper assembly;
(iii)    The outer housing/sleeve which has a lip to allow a firm connection with the MIP;
(iv)    The push-in light plate which includes the bulbs; and,
(v)    The legend, which incorporates a replaceable coloured lens.

The four terminal connections on the rear of each annunciator are specific to the functionality of the unit.  Each will exhibit a differing circuit dependent upon its function.  Likewise, each annunciator is individually indexed to ensure that the upper assembly cannot be inadvertently mated with the incorrect lower assembly.

LEFT:  A disassembled annunciator showing the main components (click to enlarge).

Annunciators typically are powered by 28 Volts, use two incandescent ‘push-in style’ bulbs, and dependent upon the korry’s function, may have a light plate coloured amber, white red or green.  The legend is the name plate, and legends are usually laser engraved into the light plate to ensure ease of reading.  The engraved letters are in-filled with colour to allow the printing to stand out from the light plate’s lens colour.

Specialised Korry

The Next Generation series of aircraft use a korry, a type 318, that is slightly different to the standard Korry. This Korry enables the functionality for the BELOW G/S – P-Inhibit function.  

The Type 318 differs from other korrys used in the MIP in that it has a dry set of momentary contacts which are controlled by pressing the light plate.  Pressing the illuminated light plate extinguishes the annunciator and cancels the aural ‘Below Glideslope’ caution.

Reproduction Verses Original Equipment Manufacture (OEM)

The four biggest differences between reproduction and OEM annunciators are:

(i)     The ability to depress the light plate in the OEM unit for Push-To-Test function;
(ii)    The ability to replicate specific functions, for example the Below G/S P-Inhibit korry;
(iii)    The hue (colour) of the lens and crispness of the legend; and,
(iv)    The brightness of the annunciator when illuminated (5 volts verses 28 volts).

Reproduction Korry Shortfalls

Two areas lacking in reproduction units is the brightness of the annunciator when illuminated, and poorly defined legends.  

For the most part, reproductions use 5 volts to illuminate two LEDS located behind the lens.  Whilst it is true that the use of LED technology minimises power consumption and heat generation, the brightness of the LEDS, especially during the day,  may not be as bright as the two 28 volt incandescent bulbs used in an OEM annunciator.   Moreover, 5 volts does not allow the successful use of DIM functionality.  

It is unfortunate that many lower priced annunciators also lack well defined engraved lens plates making the ability to read the annunciator legend difficult at best.

Shortfalls notwithstanding, most high-end reproduction annunciators are of high quality and do the job very well.  

Table 1: provides a quick reference to determine the main differences between OEM and reproduction annunciators. Note that the appearance of the annunciator can alter markedly between different manufacturers of reproduction units.

Installation, Interfacing and Configuration of OEM Annunciators

Replacing a reproduction annunciator with its OEM counterpart is straightforward if the Main Instrument Panel (MIP) has been produced 1:1; however, reproduction MIPs are rarely exactly 1:1 and in all probability you may need to enlarge the hole that the annunciator resides.  If this is the case, ensure you use a fine-grade aluminum file and gentle abrade the hole to enlarge it.  When enlarging the hole, ensure you continually check the hole size by inserting the korry – if the hole is enlarged too much, the korry will be loose and will require additional methods to secure to the MIP.

Disassembling a Korry

It is important to understand how to disassemble the annunciator.  

LEFT: The individual indexing can be observed on the top surface of the upper assembly.  To separate the two assemblies a hex screw must be used to loosen the hex screw located inside the brass-coloured circular fitting.  Note that this is a new style LED korry which does not support the older incandescent bulbs (click to enlarge).

First, the light plate has to be gently pried loose from the upper assembly.  Once this is done, the upper and lower assemblies must be separated to allow the outer/sleeve to be removed.  The Type 318 annunciators have a hex screw, located in the lower assembly unit, which needs to be loosened with a 5/64th hex wrench to allow separation, while the Type 319 annunciators are secured by two standard screws that require a small blade screwdriver.  

Once the two parts are separated, it should be noted that the upper assembly has a flange at the forward end; this flange enables the annunciator to be firmly connected to the MIP.   

Attaching a Korry to the MIP

Insert the upper assembly into the MIP flange facing forward.  Next, slide the housing over the rear of the mechanism from the rear of the MIP.  Rejoin the lower section and tighten the hex screw.    If the MIP is 1:1, the annunciator should now be firmly secured to the MIP wall. The light plate can now be pushed into the mechanism.

LEFT:  Is your MIP 1:1 and will it fit OEM korrys without further to do?  Click the diagram to see the dimensions of korrys (with thanks to Mongoose for diagram).

If the annunciator does not fit firmly into the MIP, it can be secured by using silastic or a glue/metal compound.  (I do not recommend this.  It is best to ensure the hole is the correct size or a tad too small.  This will guarantee that the annunciator will have a firm fit).

Provided the mechanism is not faulty or does not break, the chance that it will need to remove it is very remote.  If the bulbs fail, they are easily replaced as they are contained within the light plate.

Wiring - Procedure

Wiring the MIP annunciators is a convoluted and repetitious process that involves daisy-chaining the various annunciators together.  Because wiring is to and from four terminals, it can be difficult to remember which wire goes where.  As such, it is recommended to use coloured wire, label each wire and keep meticulous notes.  

Each annunciator has four terminals located on the rear of the unit that corresponds to:

(i)      Positive (28 volts);
(ii)     Logic for the function of the korry;
(iii)    Lights test; and,
(iv)    Push-To-Test.  

To crosscheck the above, each Type 2 korry has a circuit diagram stenciled on the side of the assembly.

Figure 1: A schematic of the three types of korrys used in the Boeing 737.  The left diagram is from the 318 push to inhibit korry.

For the OEM korrys to function correctly, they need to be connected with an interface card (I/O card).  An example of such a card is a Phidget 0/16/16 card.

(i)    Designate the annunciator closest the I/O card and power supply as the lead annunciator (alpha).  

(ii)    Terminal 1 and Terminal 4 are the power terminals for each korry.  Connect to the alpha korry the positive wire from the 28 Volt power supply to terminal 1 and the 28 Volt negative wire to terminal 4.  The wires from these two terminals are then daisy-chained to the identical terminals on the other korrys in the system.

(iii)    Terminal 2 controls the logic behind the function for each korry.  A wire must connect from terminal 2 of each korry to the output side of the I/O card.  To close the loop in the I/O card, a wire is placed from 28 Volts negative to the ground terminal on the card (input).

(iv)    Terminal 3 controls the logic behind the light test toggle.  A wire is daisy-chained from terminal 3 of the alpha korry to all other korrys in the system.  A wire is then extended from the final korry to the lights test toggle switch.  This switch has been discussed in detail in a separate post.

Quite a bit of wire will be needed to connect the thirteen or more annunciators and it is a good idea to try and keep the wire neat and tidy by using a lumen to secure it to the rear of the MIP.

Mounting and Brackets

Every simulator design is different, and what is suitable for one set-up may not be applicable to another.  

The I/O card that is used to control the MIP annunciators is mounted within the System Interface Module (SIM).  To this a straight-through cable is securely attached that connects to a D-Sub connector mounted on an aluminum bracket.  The bracket and two terminal blocks are strategically mounted on the rear of the MIP and enable the various wires from the korrys to connect with the straight-through cable.

Interfacing and Configuration Using ProSim737

To interface the annunciators, follow the directions on how to wire your I/O card.

This article provides information on the Phidget 21 Manager (software) and how a Phidget interface card is used.

If the annunciators have been correctly daisy-chained together, only the wires from terminal 2 of each korry will need to be connected to Phidget card.  When power is applied, the Phidgets software will automatically assign outputs to any device (korry) attached to the 0/16/16 card.  

To determine the digital output number for each annunciator, open the Phidgets 21 Manager, push the light plate on a chosen annunciator and record the allocated output number.  The output numbers are used by ProSim737 to allocate that annunciator to a specific software command line.  

Configuring the MIP annunciators in ProSim737 is a two-step process.  First, the annunciator must be assigned as a switch (for the puhs- to-test function to operate), then as an indicator (for the annunciator to illuminate).  Before commencing, check that Phidgets have been assigned in the driver section of the configuration section of the main ProSim737 menu.  

Open the configuration screen and select switches and scroll downwards until you find the appropriate switch that corresponds to the annunciator.  Assign this switch to the output number assigned by the Phidgets software (If you have multiple Phidget cards installed ensure the correct card is assigned).  

After this has been completed, continue the configuration process by assigning each annunciator to the appropriate indicator in the configuration/indicators section.

Lights Test

A lights test is used to determine whether all the annunciators are operating correctly.  A lights test can be accomplished two ways. 

The first method is to press the light plate of an annunciator which operates a momentary switch that causes the light to illuminate (push-to-test).  This is an ideal way to determine if an individual annunciator is working correctly.

The second method is to use the MIP toggle switch.  Engaging the toggle switch to the on position will illuminate all the annunciators that are connected to the toggle switch.  This is an excellent way to ensure all the annunciators are operational and is standard practice before beginning a flight.

It should be noted that for all the annunciators to illuminate, each korry must be connected to the toggle switch. 

An earlier post explained the conversion and use of a OEM 'Lights Test' toggle switch.

Korry Systems

This post has discussed the main annunciators on the MIP which is but one system.  Other systems include the annunciators for the forward and aft overhead annunciators, fire suppression panel and several other panels.

LEFT:  The fire suppression panel annunciators are also korrys.  Like their MIP sisters, the korrys are very bright when illuminated as they are powered by 28 volts (click to enlarge).

To connect additional systems to the enable a full lights test to be done, an OEM aircraft high amperage relay can be used.  

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.  This is made possible by the unique multi-segment system that the OEM toggle switch provides and the ability of the relay to handle high amperages from multiple aircraft systems.

LEFT:  OEM multi-relay device.  The relay from a Boeing aircraft is not necessary; any aircraft relay will suffice.  It's wise to choose a relay that has multiple connection posts as this will enable different systems to be connected to the relay.  The relay is easily fitted to the rear of the MIP or to the inside of the center pedestal.

A benefit of using an OEM relay is that it provides a central point for all wires from the various systems to attach, before connecting to the lights test toggle switch.  Note that 28 volts bmust be connected directly to the relay for correct operation.

The relay will, depending upon the throw of the toggle switch (lights test), open or close the circuit of the relay.  Opening rhe relay circuit (when the light test toggle is thrown) enables 28 volts to flow through the relay and illuminate any annunciators connected to the system.


Fortunately, apart from a few functions, there is little difference between older style annunciators used in the classic series airframes and those used in the Next Generation aircraft - an annunciator is an annunciator no matter from what airframe (200 series, Classic or Next Generation).

Annunciators are relatively common and are often found ion e-Bay.  However, to acquire a complete collection that is NG compliant can be time consuming, unless a complete panel is purchased and the annunciators removed.


The annunciators used in the simulator came from a B737-400 airframe.   This aircraft - serial number N843BB and construction number 25843 had a rather interesting lineage. 

LEFT:  25843 B737-400 in service with British Airways (click to enlarge).

It began service life in March 1992 with British Airways as G-DOCM before being transferred to Fly Dubai and Air One in 2004.  Late 2004 the airframe was purchased by Ryan International and the registration changed to N843BB.  Between 2005 and 2010 the aircraft was leased to the Sundowner LCC who at the time was contracted to the US Dept. of Justice.   The aircraft was returned to Ryan International mid 2010 and subsequently scrapped.


OEM - Original Equipment Manufacturer (aka real B737 aircraft part)


New Interface Modules 

My friend and I have not been sitting idle.  Part of the upgrade to the simulator has been additional interface modules.

In early 2014, an Interface Master Module (IMM) was constructed to trial the modular concept.  This module housed most of the interface cards and relays that, at the time, were used in the simulator.  This trail was successful.  The single trial IMM has now been discarded and has been replaced with the:

•    Throttle Interface Module (TIM);
•    Throttle Communication Module (TCM);
•    System Interface Module (SIM); and,
•    A more advanced Interface Alert System (IAS) that connects to the TIM and a lesser degree the TCM.

Information concerning each of these modules, including an introduction to the modular concept, can be found in a new section on the website named Interface Modules.  Interface Modules can be assessed from the main menu tabs located at the top of each website page.

It has taken considerable time to design and construct, and then interface these modules to the simulator.  To some, the process may appear complex and convoluted.  However, in the long term the idea is sound and a centralized area offers considerable advantages.

I hope you enjoy reading about the new modular systems.

If you note any problems with the new pages, please contact me so I can rectify this issue.

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