B737-800 AFDS Unit - Converted and Installed to MIP

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OEM AFDS and bracket is a solid piece of engineering.  it looks like a small 'brick'.  The three angled annunciators can easily be seen in the photograph as can the attachment bracket and screws

The Autopilot Flight Director System (AFDS) is located on the Main Instrument Panel (MIP).  There are two identical units; one situated the Captain-side and the other on the First officer-side. 

The AFDS is one of several components belonging to the Automatic Flight System (AFS) and is also referred to as the autoflight annunciator and autopilot/autothrottle indicator.  The FMC annunciator is often referred to as the FMC alerting indicator.

The purpose of the unit is two-fold; to provide the flight crew with a visual warning of disengagement of the Autopilot and Autothrottle, to an alert on the FMC, and to enable the resetting of and testing of the unit (light test). 

The unit has two annunciation colours, red and amber in either a flashing or steady state which correspond to either an alerting or advisory messages.  Red precedes Amber in the level of importance.  The A/P and A/T annunciators have dual colour capability while the FMC annunciator displays only amber.

This unit was removed from an United Airlines Boeing 737.  On inspection, it was observed that the toggle was slightly bent.  The bent toggle may have been the reason why the part was scrapped; it failed certification. The toggle was easily straightened.

Conditions for Operation

There are four operating conditions:

1:    Autopilot (A/P) Disengage Light

The annunciator will flash RED if either the autopilot or autothrottle is disengaged. The former will also trigger the A/P disengaged tone (whoop, whoop, whoop).  To extinguish the flashing light and reset the unit, the flight crew must push either of the two annunciators (A/P P/RST or A/T P/RST) or press the yoke disengage switch twice.

The annunciator will illuminate a steady RED in any of the following conditions:

  • The stabilizer is out of trim below 800 feet RA on a duel channel approach

  • The ALT ACQ mode is inhibited during an autopilot go-around (is stabilizer not trimmed correctly)

  • The disengage light test switch is held in position 2, or

  • The automatic ground system fails.

The annunciator will illuminate flashing AMBER when the autopilot automatically reverts to CWS pitch or roll mode while the in Command (CMD).   To extinguish the light, press either the A/P P/RST annunciator or press another mode of the MCP.

The annunciator will illuminate steady AMBER when the light test switch is held in position 1, or when a downgrade in autoland capability occurs.

2:  Autothrottle (A/T) Disengage Light

The annunciator will illuminate flashing RED if the autothrottle (A/T) is disengaged.

The annunciator will illuminate steady RED if the light test switch is held in position 2.

The annunciator will illuminate flashing AMBER to indicate an autothrottle airspeed error exists under either of the following conditions:   

  • Inflight

  • Flaps not up, or

  • Airspeed differs from the commanded value by +10 or -5 knots and is not approaching the commanded value.

The annunciator will illuminate steady AMBER if the light test switch is held in position 1.

3:  Light Test Switch

The AFDS is not connected to the main light test toggle; therefore, it’s equipped with its own light test switch.  The central spring-loaded toggle is used to determine if the unit is operational. 

If the toggle is pushed toward TEST 1, it will illuminate the autopilot, autothrottle and FMC alert annunciator in a steady AMBER colour.  The FMC alert is delayed a few seconds.

If the toggle is pushed toward TEST 2, it will illuminate the autopilot and autothrottle annunciator in a steady RED colour and the FMC alert annunciator will illuminate steady AMBER.  The FMC alert is delayed a few seconds (see last photograph this page).

4:  FMC Alert Light

The FMC P/RST will illuminate steady AMBER when an alerting message exists on the CDU, the fail light on the CDU is illuminated, or the test switch is in position 1 or 2.  To extinguish the annunciation the flight crew can either clear the message from the CDU scratchpad or push the FMC annunciator.

FCOM - Simple yet Confusing

The above information has been interpreted from official documentation from Boeing and whilst straightforward to understand, can appear confusing because of to the repetitious nature of the information and the similar functionality of the unit.

The AFDS is powered by 28 Volts and when illuminated the legends are exceptionally bright and very sharp

Simply put, The AFDS is a caution and advisory panel that illuminates when there is a change from normal flight operations in the autopilot system.  For example, if VNAV disconnects for whatever reason, the A/P annunciator will illuminate (flashing AMBER) to caution the flight crew that something has disengaged in the autopilot system, in this case VNAV.

Anatomy of the AFDS Unit

The AFDS is a solid piece of engineering that contains it's own logic.  The unit has three buttons (annunciators) that illuminate when specific conditions are met.  Each button can be depressed to either cancel/extinguish a caution.  Interestingly, the buttons on the AFDS are angled downwards and are depressed in this direction - the push to cancel is not a direct push as you would expect with normal style korry (see first photograph).

oem AFDS button partially removed showing location of four bullet-style 28 Volt bulbs.  The button when removed from the lightplate hangs by a plastic ball which allows the button to be rotated in either direction

Each annunciator is fitted with four 28 Volt bulbs and depending upon the ‘caution’ either illuminate an amber of red coloured lens plate in a steady or flashing state.  

Removing the button to replace a bulb or troubleshoot highlights the advanced yet simplistic engineering.  A small insert is located on each side of the button and inserting a flat device such as a blade screwdriver or blunt pen knife bland into the insert allows the button to be slowly loosened. 

The complete button when carefully pulled from the unit will hang vertically from a plastic bracket that has been designed with a ball which allows the korry to be turned 360 degrees for bulb access.

Interfacing and Configuration

A Phidget 0/16/16 card is used to interface the unit with the avionics software.   Phidgets Manager 21 (free from Phidgets) is required to interface between the flight avionics suite and the actual analogue inputs from the unit.  

The AFDS annunciators are powered by 28 Volts and like the annunciators on the Master Caution System (six packs) there are exceptionally bright to ensure a flight crew notices them when they are illuminated.  

The AFDS, as with many OEM parts, is fitted with two Canon plugs on the rear of the unit (left image).  These plugs make connecting the unit to the Phidget card very easy – provided you know the plug pin outs.  The benefit of using the default Canon plugs are seven-fold: the connection is very good, they are the plug designed for the unit, they look neat and lastly, the plugs are easy to separate if you need to remove the unit for whatever reason.

I am not going to explain how to determine the pin outs.  This information has been documented several times in earlier posts.  For a detailed review see this link - How To Determine Connectivity.

Another post of interest is Using Interface Cards & Canon Plugs to Convert OEM 737 Parts.

Configuration in ProSim737

It is a two-step process to configure the AFDS unit.  First, the Phidget Manager 21 software must be opened to check the 0/16/16 card designation number and to determine the digital output numbers for the three AFDS switches.  To find the outputs, press any of the switches on the AFDS and note the output number.

Next, open the configuration menu in ProSim737.  You need to configure both switches and indicators (lights).  Find the specific switch in the switches menu and push one of the three switches on the AFDS and assign this to the Phidget 0/16/16 card in the drop down menu.  The output for the switch can be seen at the top of the configuration screen.  ProSim737 also has a very easy to use auto find option.  Press the AFDS switch followed by F and the software automatically assigns this switch to the correct

Interface Card and Outputs

Then in indicators, use the same card designation used in switches and assign the digital output (found in the Phidget Manager 21 software).  ProSim737 has an automated method for determining the lights/indicators.  Open the configuration menu and selecting the letter F opposite the function required.  The software will then do a sweep of all lights and functions determining the appropriate setting.

Whilst this sounds confusing, it’s very straightforward and comparatively easy to accomplish.

Matching OEM AFDS units.  The marks on the glass are scuff marks only and were subsequently cleaned

Although the hole for the AFDS can be enlarged with the MIP plate in-situ, any filing will result in a fair amount of waste filings.  The AFDS MIP plate should be removed to facilitate easier cutting and enlargement of the hole (if necessary)

Installation to MIP

It’s not difficult to mount the unit to the Main Instrument Panel (MIP) as there is already a gap in the MIP where the reproduction unit was fitted.  Depending upon which MIP type you are using, the hole may have to be enlarged with a dremel or a number 2 ‘bastard’ metal file before being finely finished using to remove any sharp edges.

The size of the hole should allow the AFDS unit to be firmly placed in the MIP so that the switches and buttons can be firmly pressed without the unit being dislodged. 

The difference in the length of the unit compared with a reproduction unit is obvious, which is why a secure method of attachment is paramount.  There are several methods in which to secure the unit; the best method to use is the original attachment bracket (seen in the first image).  If the bracket is missing, a solid sealant works well.

AFDS Bracket and Screws

The bracket is a specialist bracket designed to hold the AFDS unit securely to the MIP.  Once the unit is fitted to the MIP, the bracket is slid over the AFDS unit until snug with the rear of the MIP.  The four screws are then placed through the MIP from the front and tightened against the bracket.  This ensures that the unit will not dislodge.  Note that the screws are of two sizes. 

There is strong possibility that the MIP used will not feature the four holes to secure an OEM AFDS unit to the bracket and MIP.  These holes must be drilled into the MIP.  This task requires a solid eye as if the screw holes are not aligned correctly with the bracket, the unit will not fit correctly.

The AFDS units in these images lack the screws as the bracket has yet to be fitted.

OEM Verses Reproduction

First off, most the reproduction units are very good.  There is not a lot to the ADFS unit - basically three push annunciators and a two-way toggle.  The main difference between OEM and reproduction units is:

  • Brightness of annunciations and spread of light – 28 Volt bulbs verses the lower brightness and light spread of LEDS;

  • annunciator legends are laser engraved and are easy to read;

  • feel of the actual annunciators and toggle;

  • the outside appearance of the unit; being OEM, the unit cannot look any better than what it does…;

  • power Consumption and Heat Generation; and, the

  • the four screws on the front of the MIP which secure the bracket to the MIP.  These are rarely replicated correctly on reproduction AFDS units or MIPs.

oem AFDS with three annunciators illuminated during daylight by pressing test 2.  The 28 Volts provides ample power to allow the lights to be seen easily during daylight flying.  Note that the four screws are not visible in the photograph as the bracket still needs to be fitted. 

As with most OEM parts the AFDS units are not brand new but exhibit the usual expected service wear.  This second-hand look may not 'appeal' to everyone.

Power Consumptions (bulbs and LEDS)

It is often said that a benefit of using LEDS is the saving of power and generation of less heat.  Whilst this is definitely true for items that are permanently on and illuminated, such as backlighting, many Korrys only illuminate when a specific event triggers them, and then they are only lit up for a very short period of time.  Therefore; the amount of heat and subsequent power draw is negligible.

Another point in question is the use of bulbs and LEDS in the same airframe.  Whilst it is true that LEDS are replacing bulbs in more modern airframes, it is not unrealistic to have a B737-800 with a collection of bulbs and LEDS.  As modules are replaced with newer units, LED technology will slowly creep into the older style flight decks.  

If you are having difficulty coming to grips with using either bulbs or LEDS be assured that both are realistic.

Acronyms and Glossary

The meaning of the below acronyms are second nature to many of you; however, bear in mind that everyone has to begin somewhere and some readers may not yet understand what each acronym stands for.

  • AFDS - Autopilot Flight Director System

  • AFS - Automatic Flight System

  • ALT ACQ – Altitude Acquisition

  • A/P - Autopilot

  • A/T - Autothrottle

  • CDU – Control Display Unit (used in this website interchangeably with FMC)

  • CMD - Command A or B engage button on MCP (autopilot activation)

  • CWS – Control Wheel Steering

  • FMC - Flight Management Computer (used interchangeably in this website with CDU)

  • Korry – See Annunciator.  A brand of annunciator used in the Boeing 737 airframe

  • Legend – the engraved light plate on the front of a Korry (for example, FMC P/RST)

  • OEM – original Aircraft Manufacture (real aviation part)

  • Phidget Manager 21 – Software downloadable from Phidgets website that allows card to be interfaced between OEM part and avionics suite

  • RA – Radio Altitude

Using Interface Cards and Canon Plugs To Convert OEM B737 Parts

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an example of oem wiring and a canon plug

There is little argument that real aircraft parts add a level of realism and immersion to the flight simulator experience.  Furthermore, real parts (Original Equipment Manufacture/OEM) are built to last and if converted correctly will provide many years of trouble-free operation and enjoyment.

For the uninitiated, conversion of OEM parts can appear problematic.  Where does one begin to convert an aircraft part for simulator use?  

This post will attempt to explain the basics behind converting and connecting an OEM module via an interface card and Canon plug to Flight Simulator using ProSim737.   Additionally, it will introduce and provide a general overview of Phidget Manager 21 (PM-21) software.

Please note, I am not an expert on electronics.  My background is Earth Science (geology) which is far removed from electronics...  Like others, I have learnt how things are done by 'trial and error' and listening to those more knowledgeable than myself in this field.

OEM Parts - Modules and Panels

The first thing you will notice about an OEM part (module/panel) is the build, feel and appearance is much better than a reproduction part.  It is at this stage you will be thinking ‘I don’t really want to destroy the part by opening it and rewiring everything’.  The good news is that, while some parts certainly do need rewiring, many do not.

Fortunately, the process to convert many OEM components is similar.  Granted the pin-outs and wiring are different between units, but the methodology used to determine the pin-outs is identical.  It’s a matter of replicating your methodology with each part.

Canon Plugs - The Interface to a Wiring Maze

If you look inside a OEM panel you will be surprised at the multitude of multicolored wires that connect to various relays, switches, solenoids and circuitry. Moreover you will be very impressed with the neatness and integrity of the wiring harness and as mentioned earlier, you will be loath to destroy the craftsmanship employed.

Twin Canon plugs belonging to a OEM 737 AFDS. The plug on the right is OEM while the left is bespoke

In the real aircraft, a module is connected to the aircraft’s wiring harness by a Canon plug which is a plug with any number of pins; each pin corresponding to particular function.  A Canon plug can be locked in place with the clockwise turn of the locking cap providing a solid yet removeable connection.

The benefit of Canon plugs, amongst others, is that they provide an easy and solid connection to the module’s internal wiring.    Many individuals remove these plugs, pull apart the module and gut the wiring starting afresh.  While this certainly is possible, why do it when all that is required is to ascertain the pin-outs of the Canon plug to connect to the wiring inside the module.  I doubt many of us, with the exception of a professional electrical craftsman, have the ability to duplicate the quality of workmanship seen in an OEM module.

Unfortunately, it is common place to find modules that are sold without the corresponding male or female side of the plug.  In this case the correct male or female plug must be bought separately, an existing plug converted, or a new plug fabricated.  If you have the opportunity to use a Canon plug, always try to use it before cutting the plug from the unit.  

Determining Pin outs - The Value of a Good Multimeter

The crux of converting an OEM module is to understand the functionality of the module in question.  The best place to begin learning how a module operates is the latest FCOM.  OEM modules are made for real aircraft and as such often have functions that may not be incorporated into flight simulator.  After arming yourself with 'operator knowledge', the next step is to decipher the often cryptic maze of pins in the Canon plug.  Once this is understood, the conversion is relatively straightforward with the addition of an interface card and power supply (if needed).

oem Canon plugs showing the snake-like pattern of pin location and numbering.  This module uses two Canon plugs marked J1 and J2

The pins of a Canon plug will provide at the minimum: functionality for the part, an earth (common) and a pin (s) dedicated to power.  Traditionally, all modules have used incandescent bulbs for backlighting which is powered by 5 Volts.  Depending upon functionality, some modules require different voltages with 28 Volts being the norm.

It’s important to be able to decipher which pin does what to ensure correct functionality within Flight Simulator.  This involves logical thinking and little bit of trial and error.  It is a high probability that not all the pins in the Canon plug will be used or needed in Flight Simulator.  Remember, that in a real aircraft there are multiple systems and some wires and pins will connect with these 'unneeded' systems.  

If you carefully study the pin layout in a Canon plug you will note it is not random – there is a definite order in how the pins are presented.  You will note that in all probability some pins are numbered, but not all.  The numbers move sequentially so the pin beside the pin marked ‘5’ will either be pin ‘4’or pin ‘3’.  The snake-like pattern printed on the inside of the plug is there for good reason - it acts as map guiding you from the highest number to the lowest.

By far the easiest way to determine pin-outs for functionality and power, if you do not have a wiring schematic, is to use a multimeter set to continuity mode (beep mode). 

Phidget card 0/16/16 (one of several types).  Phidgets are a proven way to convert many OEM components; the 0/0/4, 0/16/16, 1066 analogue and servo cards are mainstays.

Which Interface Card

Most parts require an interface card of some type to allow communication between the part and flight simulator.  There are several cards that, depending upon the part’s functionality, can be used: Leo Bodnar joystick cards and PoKeys cards are commonly used while Phidget cards have been the mainstay for quite a few years.  Flight Deck Solutions also produce some excellent system cards while Pololu is another manufacturer.

Which interface card is used will depend on the functionality of the module.  A simple on/off switch or a rotary knob can be interfaced using a PoKeys, Leo Bodnar Joystick or another similar 'button-type' card.  If you have a lever that needs calibration then a potentiometer will be needed.  The Leo Bodnar card is an excellent choice and will automatically register the potentiometer’s movement as an axis when the card is activated in Windows.  A light indication (korry), or a more complicated module may require a card such as Phidget 0/16/16 or 0/0/4 card.  Throttle automation and motor activation will need additional cards such as a Phidget Advanced Servo card or Pololu card.

Phidget Cards

Phidget cards, or Phidgets, have been around for a considerable time and have been the mainstay for enthusiasts wishing to control robots, cars, airplanes and the like.  Phidgets produce several cards; however, the core cards used in flight simulation are the Phidget advanced servo cards, 0/16/16, 0/0/8 and 0/0/4 cards.  To read more about Phidget cards, navigate to the Phidget website and enter the card type into the search bar.

What Does the Interface Card Do?

The interface card is placed between the computer and the OEM module and the wires from the Canon plug are fed directly to the card (power wires usually do not connect with the card).  The card provides you with three things: an input, an output and a USB connection to the computer (or a powered hub that is then connected to the computer). Once connected, the card acts as an interface which converts an inbound analogue signal (For example, the upwards or downwards ‘throw’ of a switch) to an outgoing digital signal. For every analogue input there will be a corresponding digital output. 

An interface card requires software/logic which either comes with the card (embedded) or is downloaded from the developer’s website.  Some cards utilize Windows and the process of plugging the card into the computer will initialize the card allowing the embedded software of the card to be viewed from in Windows.  The software is found by opening the  joystick controllers menu - type ‘joy’ into the search tab of the computer to be directed to this joystick wizard. 

An example of a card that has embedded software and comes pre-calibrated is the Leo Bodnar Joystick card.  The 'Leo' card uses the joystick controller menu in Windows to allow access to the card logic. Other cards such as Polulu require calibration and programming in their own software and without calibration and programming will appear unresponsive when first connected to a computer.  Phidget cards utilize their own software (Phidget Manager 21) downloadable from the Phidgets website.

If using multiple cards of the same make and type, each card will be assigned a dedicated number allowing you to know which card controls what module.

To connect a function (for example a switch) to the Interface card you run the wire from the Canon plug/terminal to the input terminal on the card.  This process is replicated for each function of the module, bearing in mind that some functions on the Captain and First Officer side may be duplicated.  If this is the case, the wires from the module are connected into the same input terminal on the card. 

If power is required to operate the module's function or for backlighting of the panel, then a wire from the power supply will need to be connected to the correct pin in the Canon plug of the OEM module.  The usual method is to connect  power from the power supply to a solid high amperage terminal block and then to the OEM module.  Power is not normally connected directly to an interface card, unless the card has this particular capability. 

The connection of the wires to the card and connection of the card to the computer provides the link to enable the various inputs and outputs to be read either by standalone software, Windows, or directly in ProSim737.

Phidget Manager 21 User Interface.  Each serial number is specific to an individual card that is allocated when configuring the output in ProSim737

Phidget Manager 21 (PM-21) - The Bare-shell Basics

PM-21 is the replacement for the older styled Phidget’s Library.

Phidget Manager 21 (PM-21) software when installed to your computer generates a list indicating which Phidget cards are currently connected to the computer.  Each connected Phidget card can be opened individually from this list. Selecting a card will open a sub-window providing set-up information and the inputs and outputs for the selected Phidget card. 

There is also a testing area to check the functionality (inputs & outputs) of the module in addition to several other specialist features.

It is a little difficult to explain, but when this screen is open you can as in the above example, manipulate the switch up or downwards and a corresponding tick (check mark) will be seen in the input.  PM-21 will then assign this item (switch) to a dedicated output number specific only to this card.  The output number is what is used when configuring the device in ProSim737.

If converting an indicator (light) or mechanically-produced sound, the software can be used to determine if the indicator has been wired correctly.  Selecting the input section and placing a tick (check) into the appropriate box will cause the indicator to illuminate or the sound to become audible.

PM-21 UI for Phidget 0/16/16 card that controls fire suppression panel.  Moving a switch on the hardware will show a corresponding tick in the input section.  The output section can be used to test the hardware to ensure the function is working correctly

It is important to remember that the  Phidgets 21 Manager can only read installed cards if ProSim737 is closed (as of ProSim737 Version 1:34).  If the ProSim737 main menu is open, PM-21 cannot obtain the necessary information to read the card correctly.

Configuring the Interface Card in ProSim737

Once the wires from the module have been connected to the inputs of the interface card and inspected (in PM-21, Windows, or whatever software) for correct connection, the output from the interface card must be configured in ProSim737.

Before proceeding further, it is important to determine if the cards you are using are being read by ProSim737.  Open the main ProSim737 menu and select configuration/drivers and confirm that each box corresponding to the card type installed has been checked/ticked.  After this has been verified, the main ProSim737 screen will indicate which cards ProSim737 is reading.  This is a handy way to know if your interface cards are connecting correctly to your computer and are being correctly read by ProSim737.

The process to configure an output is addressed in the ProSim737 manual.  Therefore, the following is an overview.

To configure an output:

  1. Select the appropriate tab in the configuration menu (configuration/switches, configuration/indicators, etc.) that corresponds to the function of the module (i.e. light test switch)  

  2. Scroll down through the list to find the correct function (i.e. light test switch)

  3.  Move the switch on the module noting the input/output variables at the top of the computer screen

  4. From the drop down box beside the function, select the correct interface card type and serial number. (Another method is to press A located beside the function.  This will automatically select the last known position of the switch and automatically assign it).

  5. Beside the interface card drop down menu, there is another drop down menu.  Select this menu and select the correct digital output (variable shown on the screen when the switch was moved)

A similar method can be used for indicators.

Once this is done, close and reopen the ProSim737 main menu.  The function should now be registered in ProSim737. Although this process sounds rather convoluted, once done a few times it becomes second nature.

Conclusion

This is a very simple introduction to the conversion of OEM parts using the Canon plug system and the use of interface cards, in particular Phidget cards and the use of Phidget Manager 21 software. 

In general, PoKeys, Leo Bodnar joystick cards and Phidget cards (type 0/16/16 and 0/0/4) will cover the interfacing of many functions used in real aircraft modules.  However, not every part is as easy as a switch to convert.  Depending upon the complexity of the module, there may be multiple pin outs that need to be deciphered, additional logic needed, and the requirement to use multiple or single interface and/or relay cards before the part will successfully connect with Flight Simulator.

Acronyms and Glossary

  • Canon Plug – A plug made by Canon that allows a secure link between wiring systems.  The plug incorporates any number of pins, each pin corresponding to a particular functionality.  Many Boeing modules incorporate one, two, three or four Canon plugs depending upon the degree of sophistication in the module.

  • Module or Panel – Boeing parts are often called modules or panels (I use both words interchangeably)

  • OEM – Original Aircraft Manufacture (real aviation part).

  • Phidget Manager 21 (PM-21) – Software supplied by Phidgets that provides the logic behind the various Phidget interface cards.

OEM Boeing 737 Stick Shaker - Interfacing and Operation

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OEM 737 stick shaker installed to Captain-side column.  The lower section of device is what vibrates

The stick shaker is standard on all Boeing series aircraft; the Next Generation having two units (Captain and First Officer) and the earlier classic series having one unit.  The stick shaker is mounted directly to the control column and is designed to vibrate if air speed degrades to stall speed.  The Stick shaker I am using is manufactured by a company in New York. It is powered by 28 Volts (27.5 Volts to be exact).  

Configuration

Configuration of the stick shaker is a relatively easy task.  The electrical cable from the device is connected to 28 Volts, or if this is not available 12 Volts;  12 Volts still produces enough power for the shaker to vibrate, although the intensity is not as great as if the unit was connected to 28 Volts. 

To allow Flight Simulator to connect to the stick shaker, a relay card is required such as a Phidget 0/4/4 relay card.  A USB cable then connects from the card to the computer.  The stick shaker will vibrate when variables that relate to low air speed are met.  The variables are determined by the flight avionics software (ProSim737 or Sim Avionics).

Phidget 0/0/4 relay card showing the main positive wire (red wire) cut with each end inserted into the correct terminals of the relay card

Interfacing and Wiring

The Phidget 0/0/4 relay card is mounted in-line between the 28 Volt power supply and the stick shaker.    Either of the two wires (+-) from the power supply can be cut to install the in-line relay; however, only one wire is cut; the other remaining unbroken from the power supply to the stick shaker.

The 0/0/4 relay card has four relays of which one is required.  Each relay has three terminals: normally open (NO), common (C) and normally closed (NC).  For the stick shaker the common and normally open terminals are used.

Carefully cut one of the two wires leading from the 28 Volt power supply.  Insert the wire coming directly from the power supply into the terminal marked common (1C, 2C, 3C or 4C).  The other end of the cut wire, which comes from the stick shaker is inserted into the terminal marked NO (normally open) of the same terminal.

If the wires have been inserted into the correct terminal of the relay card, the circuit will be complete only when the parameters established within the flight avionics software are valid.  At all other times the relay will break the circuit by not allowing the power to reach the stick shaker. If you have made a mistake, the stick shaker will vibrate continuously.

Protection

When connecting the stick shaker, it is a good idea to include a diode to protect your computer from any magnetic return signal should the relay fail.  A return signal to the computer may cause problems with the computer, and in it worse instance allow 28 volts to surge into the computer destroying your mother board. 

Positive and negative wires from the stick shaker enter the terminal block on the right.  A diode is placed on the corresponding end of the terminal block prior to the two wires running to the relay (not shown)

A high-end relay, such as a Phidget 0/0/4 relay should not fail, and if it does it should fail in the closed position.  However, if 'Murphy' or 'Sod' is your First Officer then it is better to be safe than sorry, so best install a diode.

A diode is an inexpensive and very simple device that behaves in a similar way to a black hole (astronomy).  In a black hole all matter is sucked into the hole and no matter, including light leaves the hole; it is one way trap.  A diode behaves in exactly the same way.  If a failure of the relay occurs, any power that is being transmitted through the wire from the stick shaker (28 volts) will enter the diode and be trapped.  No current will leave the diode.

Three 6 cm diodes.  The silver spirals indicate the positive side (red tape) while the opposite end is the negative (white tape).  Diodes come in an array of differing shapes, sizes and trapping capacities

The heavy duty diode should be placed in parallel between the stick shaker and the relay card.  It is best to try and place the diode as close to the stick shaker as possible.  Place the positive side of the diode (usually appropriately marked) on the positive side.  The other end of the diode place on the negative side.  If you use a terminal block it is very easy to connect a diode into the circuit (see photograph).

Incorrect Wiring

Do not become concerned if you have connected the wire to the wrong terminal - the stick shaker will not be destroyed.  It will be obvious if you have inserted the wires incorrectly, as the stick shaker will operate continuously as it has unbroken power.

I was debating to re-paint the stick shaker, however, decided to keep it as it is.  I like the used look rather than the pristine 'never been there' look.

Although the stick shaker is not essential, it’s often the smaller things and attention to detail which help bring the simulator to the next level.  I am using OEM control columns and adding a stick shaker enhances the immersion.

OEM and Reproduction

When an OEM stick shaker vibrates, especially when you are not expecting it, the vibrations startle you . The yoke vibrates and the noise of the vibrations is quite loud. In contrast, reproduction stick shakers generate lower vibrations and noise.

Acronyms 

  • OEM - Original Equipment Manufacture (real aviation parts)

BELOW:  A short video demonstrating the noise and vibration made to the control column and yoke by the stick shaker when approaching stall speed.

 
 

V1-Avionics, ARINC 429 Protocol & SIM429-11 Interface - Interfacing OEM Aviation Parts

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There’s nothing like using a genuine aviation part in Flight Simulator.  Real parts are made to last, cannot be upgraded, and offer a level of immersion rarely attributable to a reproduction part.  There is also the historical perspective knowing what airframe the part was removed from.  This said, although OEM parts are not difficult to find, a solid level of ability is needed to successfully convert many parts to use in Flight simulator.  

Conversion of an OEM part can involve  re-wiring, determining the pin-outs for each function of the part, interfacing with an appropriate card such as a PoKeys or Phidget card and connecting to a suitable power supply.  OEM parts that are more complicated in nature may involve further work to determine functionality and necessitate several interface cards and relays for correct operation.

ARINC 429 Protocol & SIM429-11 Interface

Put very simply, ARINC 429 is a data communication protocol used on most higher-end commercial, military and transport aircraft.  The protocol defines the physical and electrical interfaces to support an aircraft’s avionics instruments.  

With knowledge of the protocol, many instruments can be converted for flight simulator use if an appropriate avionics interface is used between the simulator and the OEM part.

 V1 Avionics has developed a low-cost interface called the SIM429-11 Interface.  This interface will allow easy connection of OEM instruments avoiding the necessity of rewiring and conversion.

Whilst the Protocol is used by many OEM parts, it is not used by all; therefore, if the Protocol is not supported, conversion of that part to Flight Simulator will still be the traditional way using an interface card.

V1-Avionics

V1-Avionics is the company behind the development of the SIM429-11.  The project team comes from a background in telecommunications, engineering and aerospace applications and is ideally positioned to unravel the intricacies of the ARINC 429 Protocol, to develop, and eventually release the SIM429-11 interface for public use.

LEFT:  SIM 429 enclosure by V1-Avionics - compact and easy to install (image copyright V1 Avionics).

Once the interface is released, conversion of OEM avionics instruments will become easier, more streamline, and within the reach of all flight simulator enthusiasts.

I'll post additional information as this technology unfolds.

Acronyms 

OEM - Original Equipment Manufacture (real aviation parts)

Boeing 737 NG Master Caution System ('six packs') Installed and Operational

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There is no mistaking the clarity and brightness of an OEM unit.  This is the Captain-side Master Caution System (MCS)

In my opinion, many simulators fall short when it comes to replicating the Master Caution System (MCS).  Most companies offerings are cheesy-looking in appearance, exhibit the incorrect colour hue, and lack the brightness seen is the OEM unit.  

This post will examine the use of Master Caution System and explain how the OEM items were fitted to the simulator and interfaced with ProSim737 avionics suite.  It will also briefly compare the real unit to the reproduction unit.

Click images for larger view.

Boeing Master Caution System (MCS) - Overview and Use

The Master Caution System (MCS) was developed for the Boeing 737 to ease pilot workload as it was the first Boeing airliner to be produced without a flight engineer. In simple terms the system has been designed to be an attention getter - the brightly illuminated version of a flight engineer’s 'barked' out commands…

The MCS comprises four annunciators (warning buttons) and two System Annunciator Panels (six packs) located on the Main Instrument Panel (MIP) in the glareshield on both the Captain and First Officer sides.  

The location of the annunciators and the intensity of illumination is important.  If an annunciator should illuminate, the positioning and brightness is such, that there is minimal possibility of a flight crew ignoring the warning.  Whilst the warning buttons are duplicated on both sides of the MIP, the annunciation panels provide different 'cautions' for the Captain and First Officer.  

Fire Warning and Master Caution annunciators showing The detailed engraving on the legends

Fire Warning (Fire Warn) Annunciator

If a fire is detected in the APU, main gear well, cargo compartment or during a fire warning (or system test) in either engine, the Master Fire Warning annunciator (button) will illuminate RED.  The fire bell, and if on the ground the remote APU fire warning horn will also activate.  

Depressing the button from either the Captain or First Officer's side with a firm push will extinguish the button’s light and silence the audible fire bell and APU warning horn, in addition to resetting the system for additional warnings.  Pushing the fire warning bell cut-out switch on the overheat/fire protection panel (fire suppression module or fire handles) accomplishes the same action.

Master Caution Annunciator

The Master Caution annunciator (button) is coloured AMBER.  The button will illuminate when a system annunciator (six pack) has been triggered indicating a fault has been detected within the aircraft systems.

Depressing the button with a solid push (Captain or First Officer side) will extinguish the button’s light and reset the system for additional master caution conditions.

System Annunciator Panel ('six packs')

There are two System Annunciator Panels, one on the Captain side and one on the First Officer side.  Each light plate has six different AMBER coloured 'cautions' which are arranged such that the 'cautions' are in the same orientation as the overhead panel.  For example, FUEL is bottom left.  

Components of the Master Caution System:  Two duplicated Fire Warning and Master Caution buttons and the two System Annunciator Panels (six packs).  The diagram shows the various cautions that a flight crew can expect to observe (image copyright FCOM).  The MCS is identical for all Boeing series airframes 600 through 900 including the Boeing Business Jet (BBJ)

The display annunciations relate a specific aircraft system.  The following are displayed on the Captain-side panel: FLT CONT, IRS, FUEL, ELEC, APU and OVHT/DET.  The displays for the First officer side panel are: ANTI-ICE, HYD, DOORS, WNG, OVERHEAD and AIR COND.

If a master caution condition exists, the Master Caution light will illuminate AMBER along with the appropriate system annunciator.  Likewise, if a caution exists and is displayed on either six pack the Master Caution button will illuminate.

To extinguish the System Annunciator display, the Master Caution button should be firmly depressed.

Self-Test and Recall

The System Annunciators have a self-test and recall function.  Firmly pressing and holding either light plate will cause all annunciation lights to display (self-test).   To recall the last displayed 'caution', the light plate is pressed once and released.  After release the system annunciator will display whatever "caution" was last detected.

There is little argument that the OEM Master Caution System exceeds the quality of reproduction units.  This is the MCS from a top shelf manufacturer.  Compare this with the OEM counterpart. Reproduction units could be easily improved if they used a number of high intensity LEDS aligned in an array so that the light had better coverage

Reproduction Verses OEM

Broadly speaking, there is a large gap in quality between reproduction MCS units and the OEM version.  

For the most part, reproduction annunciators are very easy to depress - a tap of a finger will deactivate a warning or recall a ‘caution’.  The legend is printed rather than laser engraved and the colour of the light is often an incorrect colour hue which lacks the brightness of the real unit.  The last point is caused by low voltage LEDs which are not bright enough and do not have an adequate throw of light to illuminate all of the legend.  Furthermore, reproduction units are for the most part made from plastic, rather than longer lasting aluminium.

This said, some highly priced units do replicate the OEM part very well but they do cost upwards of $450.00 USD (see Fly Engravity).

In contrast, the OEM unit has engraved legends that are very distinct and easy to read, require a firm press to engage, and are very bright.  OEM units use 28 Volt bulbs which burn very brightly.

Not Just A Finger Tap - Firmness in Operation

An OEM annunciator requires a bit more force to depress the button in comparison to a reproduction unit.  I'm uncertain if this is due to the strength or weakness of the internal spring mechanism or as I've been lead to believe, is a built-in safety feature; thereby minimising the chance of a flight crew accidentally depressing and cancelling an annunciator ‘caution or warning’ with a light tap or brush of the finger or hand.

Classics Verses Next Generation (NG)

Both airframes incorporate the Master Caution System; however, the classics use different display cautions for the system annunciators. I believe there are five 'cautions' on the classic in contrast to six on the NG (600, 700, 800 & 900).  The fire and master caution annunciators are identical on all Boeing airframes.

Interfacing and Power Requirements

To interface the unit requires a Phidget 0/16/16 interface card while the power to illuminate the bulbs is from a 28 Volt power supply.  A 0/16/16 card provides 16 inputs and 16 outputs which allows complete coverage of all functions remembering some functions duplicated on the Captain and First Officer-side have wires placed into the same input terminal. The duplicated items are the fire and master caution annunciations.

Each of the four annunciators has three terminals.  A multimeter set to conductivity or beep mode is used to determine which terminal connects to which button press. 

  • To learn how to use a multimeter, read this article.

The System Annunciator Panel (six pack) is a little more convoluted as it has a recall facility and has different cautions between the Captain and First Officer units.  However, with a little diligence it’s possible to work out the terminal and wiring sequence.

Anatomy of a System Annunciator (aka six pack)

Each unit is made up of three parts:  the actual annunciator, the light plate (which incorporates the legend), and a rectangular housing that I call the cigarette packet. The housing is attached to the annunciator by two hex screws.

Light plate removed from housing and rear terminals.  Note individual pins for specific display cautions and "clam shells" for connection

The light plate has a number of pins that connect with the annunciator base, and on the rear there are eight terminals (lower image) each connecting with a specific terminal.

If you remove the outer casing, a circuit diagram has been stencilled to the unit.  It’s trial and error using this diagram to determine the correct pin outs for the terminals, but once known it’s only a matter of connecting the various wires from the terminals to the 0/16/16 card.

Eight terminals.  The outer edge of the hex nut can easily be observed on the upper left side of the annunciator

It’s important to note that if removing or loosening the outer cigarette-style housing, a hex screw located at the corner edge of the unit will need to be loosened. 

Phidgets 21 Manager

The Phidget 21 Manager is provided by Phidget and can be downloaded from their website.  This software will, when a Phidget card is connected, register that card and its distinctive number. 

Opening the Manager and then selecting the card number ID tag will allow you to see what inputs and outputs you have wired and assigned to whatever item you have connected.  You will also be able to easily test any output.

Configuring in ProSim737

Once the pin outs have been correctly determined, configuring in ProSim737 is very easy.  Open the configuration tab and select the indicators menu (tab).  Next find the appropriate names (DOORS, ELEC, APU, ANTI-ICE, etc) and in the drop down box assign the correct Phidget card and output number.

Installing to the Glareshield

Main Instrument Panels (MIPS) manufactured by different companies are rarely identical; each MIP has subtle differences – some are easier to install OEM items to than others.

Detail of Master Fire Warning annunciator showing manufacturer name and threaded button with hexagonal attachment nut.  different manufacturers produce slightly different shaped bodies

Reproduction annunciators are usually secured to the glareshield by screws; however, OEM parts often require retrofitting to allow the item to be fitted correctly. 

In the case of the FDS MIP, a backing plate made from ABS plastic was crafted to fit into the gap where the fire warning and master caution buttons reside; the plate was secured to the glareshield by self-tapping screws.

Two holes were then carefully drilled at the correct distance to allow the circular shaft of each button to be fitted through the plastic.  Once the button was sitting proud in the correct position, the screw and nut assembly was tightened against the backing plate.  

The annunciators are not designed to sit neatly side by side in the glareshield; they can be twirled to any orientation; therefore, it’s not necessary to be perfect in the alignment of the drill hole – just very close!

Securing the system annunciators to the MIP was slightly more problematic and involved using a spacer between the outside of the housing and the gap in the glareshield.  The spacer expands as you push the six pack into position, and it’s a matter of enlarging the spacer to secure the unit in the correct position.  This said, the method used is not optimal and a more secure method needs to be developed.

Video (Captain-side only)

A short video demonstrates the brightness of the buttons and display cautions.

The annunciator light plate displayed in the video is not in the best condition; it is common for airlines to place clear tape over the legends to protect them.  This did not concern me at the time, as six packs are scarce to find.  However, I have since found four buttons in better condition and will soon exchange them.

  • For those interested, to silence the fire bell in the video, I used the bell cut-out switch on the fire suppression module rather than depressing the Fire Warning Annunciator, which would have accomplished the same task.

 

737 Master Caution System and six packs

Acronyms and 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 often are called KORRYS (KORRY is the name of a manufacturer).

  • Cautions – Annunciations from the System Annunciation Panel in amber colour.  For example, DOORS, APU and ELEC.  An annunciation 'caution' triggers the Master Caution Warning light.

  • FDS – Flight Deck Solutions

  • Light Plate - the actual forward portion of the annunciator separated from the rear section and the housing.

  • Legend – The portion of the light plate that includes the engraved display (for example, ELEC or DOORS)

  • MCS – Master Caution System incorporating: Fire Warning, Master Caution Warning and two annunciator panels (six packs)

  • MIP – Main Instrument Panel

  • OEM – Original Equipment Manufacture (real Boeing part)

  • Phidget 21 Manager – Configuration software to use a Phidget card

  • 'Six Pack' – Nickname for System Annunciator Panel

  • System Annunciator Panel (SAP) – Light plate with six 'cautions' and recall facility (NG only).  Also known as 'six pack'

Update

UPDATE ON 2015-07-29 13:10 by FLAPS 2 APPROACH

Captain side straight-through cable connector mounted beneath the glare wing. The colour-coded internal wiring of the lumen can be seen.

The white terminal block facilitates connection of the MCS with the Lights Test functionality (Lights Test toggle located on the MIP).  To the terminal block, a wire connects directly to a Lights Test Busbar located in the center pedestal.  The busbar then connects directly with the OEM lights test toggle switch. The brackets are made from ABS plastic

In June 2015, the wiring design for the simulator was changed, and the annunciators were rewired to facilitate conformity with the wiring of other OEM parts.  The Captain and First Officer annunciators were separated and wired directly to a Phidget 0/16/16 card. 

To ensure that the wiring was easily identified, wiring for the Master Caution System was color-coded to avoid any confusion with the wires that have been used to wire the AFDS units.

The new wiring design called for each MCS to be independently wired and separated from the other.  Each system has the wires budded into a dedicated, colour-coded lumen which is then connected to a serial port connector mounted to a bracket.  The bracket is attached to the underside of the glare wing at the rear of the MIP glareshield.  The connectors have straight-through cables that snake behind the MIP to mate with their respective connectors on the SMART module.

Main Instrument Panel (MIP) - Seeking Accuracy in Design

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OEM 737-800 MIP AND COMPONENTS (Shawn from Airdrie, Canada, 737NG Panel (4559309701), CC BY-SA 2.0)

A reproduction Main Instrument Panel (MIP) may appear identical to its OEM counterpart, but there can be there can be subtle differences depending upon which company you purchase a MIP from. 

The disparity may not be important to individuals who decide to use a full reproduction flight deck from the same company. However, problems will soon surface if mixing parts from other companies’ or using OEM components.

The following relate to all reproduction MIPS.

The 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 manufacturers 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 knob than the one currently used by Flight Deck Solutions. The landing gear knob in the real aircraft is translucent.  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 and the trigger.

Fuel Flow Reset Switch. The real aircraft uses a switch/toggle with a larger defined and bulbous-looking head, rather than the 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 to most reproductions.  Many reproduction knobs have the grub screw located at the rear of the knob. 

Additionally, 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 metal 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 Next Generation 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 often lift and peel away, and hand application is often haphazard with some transfers straight and others being off-center.

Annunciators (Korrys). The annunciators on most reproduction MIPs use LED technology 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 the lettering is very sharp 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. Be aware that some newer Next Generation 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. OEM and reproduction panels both share varied colour hues of RAL 7011.

Dimensions & 1:1 Ratio.  High-end MIPs for the most part are very close to the correct 1:1 ratio of the OEM item and differences, if noticeable, are marginal.  But, less expensive MIPs can have the incorrect dimensions.  It is 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 are using reproduction gauges 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, then it is essential to know what is fact and what is fiction (Disneyland). 

Important Point:

  • There are many nuisances between MIP manufactures. I have mentioned but a few in this article.

System Simulation is a Priority

As I move more into the 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 in 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.

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 lens.

  • MIP - Main Instrument Panel.

  • OEM - Original Aircraft Manufacture (aka real aircraft part).

  • RAL - International colour matching system.

Ferrules

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ferrules. They enable easy connection of thin wires to terminal blocks

What are ferrules some of you may ask – no they are not the undesirable neighbours that play loud music and park old cars in front of your house; they are called “feral”… 

A ferrule is a small electrical connector that comes in a variety of different sizes that is very handy when connecting electrical wires.  The metal needle of the ferrule is hollow allowing you to fit the correctly sized wire for maximum connectivity and faithful conductivity.

Solid Connection

1mm red ferrules connected to a terminal block

Building a simulator involves the connection of a multitude of wires to interface cards, power supplies, terminal blocks and other electronic components.  Having a method to easily secure wires that ensures reliability is a great asset.

Whilst you can solder wires to the above items, it is often necessary to remove a wire for testing purposes or to add an additional function to the connection.  Twisting and clamping the wire beneath the screws or under a screw tab while functional is far from tidy, and eventually the wire will become damaged with loose wire strands. 

Loose and damaged wires can translate to poor connectivity leading to frustration when something does not work correctly.

A ferrule can easily be attached to the end of a small wire (22 gauge) and crimped.  The ferrule needle can then be cut to size to fit into an interface card or terminal block.  Ferrules come in a variety of colour-coded sizes and can be used for differing wire gauges.

A special crimper tool is used to crimp' the ferrule in place securing the wire.

I’ll submit that ferrules are not suitable to use everywhere; however, for certain applications they are useful to have in your simulator-building toolkit.

Changing Pilot Automation Dependency

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Cp Flight MCP

Although this website primarily discusses construction and flying techniques of the Boeing 737, I believe it's pertinent to include articles that relate to flying in general and have merit to both real-time aviators and virtual pilots.

This article supplements an article that discusses the Speed, VNAV and Altitude Intervention (INTV) system.

Rather than create a link to an interesting article which may at some stage be removed, I’ve copied the article verbatim below.  The article which came from Aviation Week Space and Technology is a little long, but well worth a read.

How To End Pilot Automation Dependency

It is foolhardy to draw hasty conclusions about accidents. The investigation into the cause of the Asiana 214 Boeing 777-200ER crash at San Francisco International Airport on July 6 is still in its early stages. While it is not clear exactly how crew performance figured into the accident that claimed three lives, we believe that there is no excuse for landing short on a calm, clear day in a fully functioning jetliner. If the NTSB determines that the 777-200ER ‘s engines and systems were working properly, then how could the Asiana pilots have gotten themselves into that jam?

It may be that the crew was acting primarily as “automation managers” and not remaining sufficiently engaged in actively flying the airplane. It would not be the first time that this has been a factor in an accident . In the final 2.5 min. of the flight, the NTSB says, “multiple autopilot modes and multiple autothrottle modes” were inputted—all while airspeed was allowed to drop far below the 137-kt. target. It also may turn out that software rules governing interaction of the autopilot and autothrottle in the 777 are not intuitive under some settings and problematic for landing (see page 25). But that would be no excuse for flying into the ground.

On balance, automation has been a major contributor to the safer, more efficient operation of airliners. But automation has not reached the point where it can handle all contingencies. We have not arrived at the point alluded to in the joke about the crew of the future being a pilot and a dog (the pilot is there to feed the dog, the dog is there to bite the pilot if he touches the controls). So humans must be prepared to hand-fly an aircraft at any point .

For years now, concern has been growing that airline pilot's basic stick, rudder and energy management skills are becoming weak due to over-reliance on automation systems. Pilots have become, in the words of Capt. Warren VanderBurgh of American Airlines dependent upon computers that generate the purple-pink cues on cockpit displays.

There is nothing inherently risky about using automation, he explains in a famous lecture, but there is a paradox about automation that crews must be aware of: In most situations, automation reduces workload. But in some situations, especially when time is critical, automation increases workload. For example, it is harder to rapidly and correctly reprogram a flight-management computer to avoid a midair collision than it is to turn off automated systems, grab the controls and take evasive action on one’s own.

This addiction to automation is particularly troubling because of the rapid growth of the international airline industry in the last two decades, notably in Asia and the Middle East. Many nations, including South Korea, do not have robust general aviation, light air freight and commuter airline sectors where pilots can amass hundreds of hand-flown takeoffs and departures, arrivals and landings before graduating to the cockpit of an Airbus or a Boeing airplane carrying scores of passengers.

In the wake of the Asiana crash , Tom Brown, a retired United Airlines 747-400 standards captain and former instructor of Asiana pilots , said in an email to friends that while he worked in South Korea, he “was shocked and surprised by the lack of basic piloting skills.” Requiring pilots “to shoot a visual approach struck fear into their hearts.”

Other expatriate training pilots who have worked in Asia and the Middle East tell similar stories about lack of basic head-up airmanship skills and preoccupation with head-down button pushing. They can perfectly punch numbers into the flight-management computer but if something unexpectedly crops up late in the flight, such as an air traffic control reroute close to the airport or a runway change, crews may not have time to punch, twist, push and flick all the controls required for the automation to make critical changes to the aircraft’s flight path. And head-down, they risk losing situational awareness.

This pitfall is not peculiar to developing regions, of course. Advanced automation can lull any crew into becoming mere systems monitors.

So what should be done? The automation dependency paradigm must be changed now. Crews must be trained to remain mentally engaged and, at low altitudes, tactility connected to the controls —even when automation is being employed. They should be drilled that, at low altitudes, anytime they wonder “what’s it doing now?” the response should be to turn automation off and fly by hand.

Aviation agencies need to update standards for certifying air carriers. There needs to be a new performance-based model that requires flight crews to log a minimum number of hand-flown takeoffs and departures, approaches and landings every six months, including some without autothrottle use. Honing basic pilot skills is more critical to improving airline safety than virtually any other human factor.

BELOW: Capt. Warren VanderBurgh’s 'children of the magenta' lecture (also viewable on VIMEO and UTube).

 
 

RMI Knobs Installed to Main Instrument Panel (MIP)

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oem rmi knobs

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.

The replacement knobs are highly detailed reproductions of the original 737-800 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 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.

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 that at the moment I do not want to contemplate.  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.

UPDATE

Acronyms

  • MIP – Main Instrument Panel

  • RMI – Radio Magnetic Indicator.  The gauge that displays VOR and ADF mode.  Part of B737 NG stand-by instrument cluster

RMI Switch Assembly (ADF/VOR) Installed to Center Pedestal - Flying by VOR & NDB Made Easier

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RMI Switch Assembly dated stamped 1967 (727 or 737-100/200).  RMI switch has been custom fitted to blanking plate

It probably seems an oddity to install into the center pedestal a switch manufactured in 1967 that in all probability was used in a an early model Boeing 737 or more likely a 727.

My reasoning is quite simple. I enjoy flying using VORS and NDBs and the use of the older style 737 switch assembly replicates some the functionality of the stand-by RMI buttons on the MIP. In time, the panel will be replaced when I find OEM 737-800 RMI knobs.

VOR and NDB Flying (NG)

The Next Generation allows tracking of the primary and secondary VOR/NDB with a visual display on the Navigation Display (ND).  The display can be turned on and off from the either the Captain or First Officer side EFIS.  Tuning to the VOR and NDB is accomplished by dialing in the correct frequency on the NAV and ADF radio panels. 

The navigation output is duplicated and shown as dual needle movement on the RMI gauge which is the third gauge within the stand-by instrument cluster.  In the real 737 aircraft, the mode of the RMI gauge can be toggled between VOR 1/2 and ADF 1/2, or a combination, by the small knobs on the front of the RMI that protrude through the Main Instrument Panel (MIP).  

RMI Knobs

It’s unfortunate that many manufacturers of reproduction Main Instrument Panels (MIPS) do not include functionality to these two small knobs and provide only a rough facsimile of an original knob.  

Early Boeing N737 RMI Switch Assembly showing detail of two switches, Canon plug, wiring harness and front panel. The original Canon plug and pib-outs was used in the conversion

Interfacing, Wiring and Blanking Plate

The switch assembly was interfaced to function with ProSim737 using a PoKeys55 interface card.  In my simulator ,the PoKeys card resides in the System Interface Module (SIM) and the five wires from the 737 switch were run through a piece of conduit (plastic piping) beneath the platform to the System Interface Module (SIM) located forward of the MIP.

The five wires correspond to VOR 1/2 and ADF 1/2.  The fifth wire is the common (earth).  Two additional wires (positive and negative) connect to the 5 Volt busbar located in the center pedestal and is used to power the backlighting of the panel.

Canon Plugs - Why Change a Perfect System

The switch assembly included a male Canon plug in very good condition; therefore, it was decided to use the Canon plug system rather than wire separately.  A female Canon plug was purchased from E-Bay and a multimeter, set to continuity mode, was used to determine the correct pin-outs for the plug.

A longer wire harness was made to allow the harness to reach the System Interface Module forward of the MIP.  Using Canon plugs keeps the wiring very neat and allows for an easy disconnect should you need to remove the panel from the pedestal.

oem 727 early 737 cl RMI Switch Assembly installed to the center pedestal.  Selection can be either ADF1/2, VOR1/2 or a combination.  Switches and panel are backlit by 5 Volts which is the standard voltage used in many panels. This panel would never be seen in a 737 Next Generation center pedestal

Blanking Plate

In the Boeing 727 and earlier 737 classic airframes, the RMI Switch Assembly is mounted to the lower part of the MIP (from memory).  In this era (circa 1967) modern-style EFIS units had yet to be developed. 

As such, the switch does not require a lightplate as it is attached to the MIP by four screws.  To facilitate the switch being installed to the center pedestal, a blanking plate had the center portion cut out using a  dremel cutter.  The switch assembly could then by placed in the cut hole and attached directly into the blanking plate via the four screws and the panel secured to the pedestal by DZUS fasteners.

Mapping Functions

To configure the functionality of the Switch Assembly to ProSim737 was straightforward, as the functions have already been mapped within ProSim's configuration menu.  This is one of the major advantages to using ProSim737 as the avionics suite; many functions have been mapped and you do not need to delve into the world of FSUIPC offsets in an attempt to get something working (This what must be done if you use Sim Avionics).

Never on a Next Generation

Although you would never see the panel on a 737 Next Generation aircraft, the switch assembly is very enjoyable to use and makes using the alternate RMI gauge more user friendly - at least until OEM RMI knobs are obtained and configured for use, or an OEM RMI gauge acquired.

Acronyms & Glossary

  • ADF – Automatic Direction Finder

  • Blanking Plate - An aluminium plate used to cover a gap in the pedestal or overhead.  The plate is equipped with DZUS fasteners for attachment to the DZUS rail VOR - Omni Directional Radio Range

  • EFIS – Electronic Flight Instrument System

  • IMM – Interface Master Module

  • MIP – Main Instrument Panel

  • NDB – Non Directional Beacon

  • PANEL – Refers to actual avionics module.  Panel and module are interchangeable

  • RMI – Radio Magnetic Indicator.  The gauge that displays VOR and ADF mode.  Part of B737 NG stand-by instrument cluster

B737-800 NG EVAC Panel - A Nice-looking Panel

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oem 737-800 evacuation panel (evac)

A quick post to showcase an OEM evacuation (EVAC) panel. The panel is usually mounted in the AFT overhead; however, as I am still developing the overhead panels I have temporarily installed it into the center pedestal.  

The EVAC panel’s use needs no introduction – it is triggered by the flight crew if and when evacuation of the aircraft is required / occurring.  A switch in the passenger cabin can be triggered by the cabin crew alerting the flight crew that an evacuation is imminent.  The panel is only used when on the ground (obviously).

The EVAC panel is from a 737-800 and the functionality includes: an arming/off switch, flashing red coloured EVAC annunciation, alarm cancelling pull knob, and a piecing alarm (horn). 

The panel is not connected to any function within Flight Simulator; therefore, an interface card is not required.  A continuity test, using a multimeter, is used to determine which pins in the Canon plug correspond to which switch/toggle/alarm.  The backlighting is powered by 5 Volts whilst the alarm and annunciator is 28 Volts.

Although the panel serves no true function in the simulator, it is a good-looking panel that improves the aesthetics of the center pedestal.  Once the overhead is fully developed the EVAC panel will be removed from the pedestal and placed in the aft overhead panel (the correct location).

The EVAC panel is an airline option.

Below is a video showing the panel’s use.

 

737-800 EVAC panel operation

 

B737-800 NG Fuel Flow Reset Switch - OEM Switch Installed and Functional

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oem 737-800 fuel flow switch can clearly be identified by its bulbous head.  I have observed that on some air frames this switch has a cross hatch design

I have replaced the reproduction Fuel Flow Reset Switch (FFRS) with an OEM switch.  I was not happy with the reproduction switch, which did not function correctly or look anything like the real switch used in the aircraft; the genuine switch is spring-loaded, quite large, and has a bulbous head.  The FFRS is a new switch which was probably destined to be installed into a Boeing Next Generation aircraft.

FFRS Functionality

The Fuel Flow Reset Switch resides on the center forward panel immediately above the central display unit on the Main Instrument Panel (MIP).  The function of the FFRS is to provide information on the fuel flow and fuel used.  The fuel flow/used indications are displayed on the lower display unit (depending on your avionics set-up preferences). 

The switch is a one-pole spring-loaded two-stage three-way momentary toggle switch.  The normal 'resting' position of the switch is in the central (RATE) position.  In this position the display unit indicates the fuel currently being used.  Pushing the switch downwards to (USED) changes the display indication to read the fuel that has been used.  Pulling the bulbous knob towards you whilst simultaneously pushing the switch upwards (RESET) resets the fuel used to zero.  The downward and upward throw of the switch is momentary which means that when the switch is released it will automatically return to its central "resting" position.

The reason the switch is two stage for upwards deployment (pull and push upwards) is for safety; a flight crew cannot inadvertently push the switch to the upwards position resetting the fuel used.

Installation and Wiring

Depending upon what MIP you are using, installation of the switch may require enlarging the circular hole in the MIP. This is to enable the shaft of the OEM switch to fit through the MIP frame and the light plate of the Center Forward Panel.  If the hole must be enlarged, care must be taken to not damage the light plate. 

If the MIP you are using is 1:1 ratio, then the switch should fit through the hole perfectly.  The switch is secured behind the light plate with a hexagonal nut.  This switch fits the FDS MIP without need for enlarging the hole.

The rear of the FFRS has three standard-style screw post connections, each connection being either positive, negative or common (earth).  To determine which throw of the switch does what, it’s necessary to use a multimeter set to continuity (beep mode).  Place the black probe of the multimeter on the central screw post and then place the red probe on either of the other two screw posts.  When you move the switch you will hear an audible beep indicating that function is “active” for that screw post.

diagram 1; fuel flow switch display indications (copyright Boeing fcom)

Interfacing

An I/O card is required for the switch to interface with the avionics suite.  A PoKeys card will suffice; however, I have used a Phidget 0/16/16 card; this card is installed in the SMART module.  This card has been used primarily because it had unused inputs.

Establishing the correct functionality is done within the flight avionics software.  If using ProSim737 it’s a matter of finding the fuel flow switch functions within the switches section of the configuration menu and assigning them.  Failing this FSUIPC can be used.

The FFRS is but a small item; however, many small items make a sum.  By using an OEM switch, you have the correct functionality of the switch in the simulator, and you improve the aesthetics.

The serial/part number for the switch is: MS-24659-27L, or for the non military specification 1TL1-7N.

Acronyms and Glossary

  • FFRS – Fuel Flow Reset Switch (also known as the Used Fuel Toggle)

  • OEM – Original Equipment Manufacturer

  • MIP – Main Instrument Panel

  • Momentary Switch - a switch which can be pushed downwards or upwards and when released returns to a central "resting" position

  • Two-Stage Switch - A switch that requires two events to activate the switch.  For example, simultaneously pulling and pushing upwards on the switch

B737 Throttle Quadrant - Automated Thrust Lever Movement

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Autothrottle arming switch is a solenoid operated switch clearly identified on the main Instrument Panel (MCP).  The switch is linked to the IAS/MACH speed window (adjacent) and to two A/T disconnect buttons located either side of the throttle lever handles. cp flight pro mcp

In this final post dealing with the conversion of the 737-500 throttle quadrant. I will discuss the automation and movement of the throttle thrust levers and touch on some problems that occurred.  I will also briefly discuss the installation and use of potentiometers.  Part of this post will be repetitive as I briefly discussed automation in an earlier post.

Avoiding Confusion - Automation

To avoid confusion, automation refers only to the movement of the two throttle thrust levers in relation to the %N1 output.  These N1 limits and targets are provided by the Flight Management Computer (FMC) and normally are used by the Autopilot Flight Director System (AFDS) and the Auto Throttle (A/T) to maintain airspeed and/or thrust setting.  

Automation and Movement - Interface Cards

Automation is the use of CMD A or CMD B (autopilot) to control the %N1 outputs from the Autothrottle (logic), and motorization is the moving of the throttle levers in unison with %N1 output.  To achieve this seamlessly, two interface and one controller card are used.

Alpha Quadrant Cards (2):  Each  motor controller card has the automation logic programmed directly to the card (via propriety software).  One card controls Auto Pilot CMD A while the other card controls Autopilot CMD B.

Phidget Advanced Servo Card (2):  This card acts as an interface and bridge between the Alpha Quadrant cards and the flight simulator platform used.

The card does not provide movement for the throttle thrust levers; this is controlled by a Phidget Motor Controller card.

Leo Bodnar BUO 836 A Joystick Controller Card:  This card will register in Windows the movement of levers, buttons and switches on the TQ.  Calibration of this card is done first in Windows, then in Flight Simulator (FSX/P3D), FSUIPC or the avionics suite used; for example, ProSim737.

The interface cards are mounted forward of the MIP within the Throttle Interface Module (TIM) and are connected to the throttle unit by custom VGA straight-through cables and to the computer by a single USB cable.

Main Controller Cards

The controller card I have used is not a Phidget card but a specialist card often used in robotics (Alpha Quadrant card).  The software to program the card has been independently developed by a software engineer and does not utilize Phidgets.

The technology used in the controller card is very similar to that utilized by NASA to control their robotic landers used in the space industry.  The technology is also used to control robots used in the car industry and in other mass production streams.  One of the benefits of the card is that it utilizes a software chip (firmware) that can be easily upgraded, reprogrammed, or replaced.  

The Alpha Quadrant cards provide the logic to operate the throttle automation (the movement of the thrust levers) and act as a bridge between the two cards and the avionics suite.

Being able to program each card allows replication of real aircraft logic and systems.  Whenever possible, these systems and their logic have been faithfully reproduced.

oem throttle. toga switches clearly seen

CMD A/B Autopilot - Two Independent Systems

Most throttle units only use one motor controller card which controls either CMD A or CMD B; whichever autopilot you select is controlled by the same card.  

In the real aircraft to provide for redundancy, each auto pilot system is separate.  This redundancy has been duplicated by using two Alpha Quadrant controller cards, rather than a single card.  Each controller card has been independently programmed and wired to operate on a separate system.  Therefore, although only one CMD is operational at any one time, a completely separate second system is available if CMD A or B is selected on the MCP.

Synchronized or Independent Lever Motorization

Synchronization refers to whether the two throttle thrust levers, based upon separate engine %N1 outputs, move in unison with each other (together) or move independently.

In earlier Boeing aircraft, such as the 707, 727 and 737 classics, the levers were roughly synchronized; however, the Next Generation has as a computer-operated fuel control system which can minutely adjust the %N1 of each engine.  This advanced fuel management can be observed in a real aircraft whereby each throttle lever creeps forward or aft independent of the other lever.

Programming flight simulator to read separate %N1 outputs for each engine, and then extrapolating the data to allow two motors to move the throttle levers independently is possible; however, the outputs are often inaccurate (for varying reasons).  This inaccuracy can often be observed on reproduction throttle units that exhibit a gap between lever one and lever two when automating %N1 outputs.  

It was decided to maintain the older system and have both levers synchronized.  Although this is not replicating the Next Generation system, it does make calibration easier.  If in the future incremental thrust lever movement is required, it’s a matter of adding another 12 Volt motor to the front of the throttle bulkhead to power the second thrust lever.  

Autothrottle activation will advance both thrust levers in unison to the fmc calculated %N1 output

Be aware that although both thrust levers are synchronized, the throttle handles may still show a slight difference in position in relation to each other.  This is caused by the varying tension that needs to be maintained on the fan belt connecting the 12 Volt motor to the mechanical system beneath the thrust levers.

Another aspect to note is that the position of the thrust levers during automation is arbitrary and is a visual representation of the %N1 output; it may or may not reflect the exact position on the throttle arc that the thrust lever would be placed if moved manually (by hand with Autothrottle turned off).  

Although the throttle is automated, manual override (moving the thrust levers by hand) is possible at any time, provided the override is within the constraints of the aircraft logic (programmed into the Alpha Quadrant card), and that provided by the flight avionics (ProSim737).  

Power Requirements and Mechanics

To provide the power to move the throttle thrust levers, a 12 Volt motor previously used to power electric automobile windows, is mounted forward of the throttle bulkhead (see image at bottom of post).  Connected to the motor's pulley is a fan belt that connects to the main pulley located beneath the thrust levers.  To enable the thrust levers to move in unison, a slip clutch, which is part of the main pulley assembly, is used.  

Captain-side TO/GA button is clearly seen below lever handles.  The button at the end of the handle is the Autothrottle disconnect button

ProSim737 Limitations - TO/GA and Auto Throttle Override

Unfortunately, concerning automation the ProSim737 is deficient in two areas: TO/GA and A/T Override.

(A)  TO/GA

In the real aircraft, the flight crew advances the thrust levers to power 40%N1 (or to whatever the airline policy dictates), allows the engines to spool, and then pushes the TO/GA button/s.  Pressing TO/GA causes the throttle to go on-line and to be controlled by the AFDS logic.  The throttle levers then advance automatically to whatever %N1 the logic deems appropriate based on takeoff calculations.

As at the time of writing. If you're using ProSim737, this will NOT occur.  Rather, you will observe the thrust levers retard before they advance (assuming you have moved the thrust levers to %40 N1).  The reason for this is nothing to do with how the throttle is calibrated, FSUIPC or anything else.  ProSim737 software controls the %N1 outputs for the automation of the thrust levers and the developer of the software has not fine-tuned the calibration in the software to take into account real-world avionics logic.  This thread located on the ProSim737 forum provides additional information. 

I have not tested Sim Avionics, but have been told this issue doesn't occur in their avionics suite.

There are two workarounds:  Engage TO/GA from idle (hardly realistic) or push the thrust levers to around 80% N1, allow the engines to spool, then push TO/GA.  Anything less that around 80% N1 will cause the thrust levers to retard before advancing.

Latest ProSim737 release (V133)

The latest version of ProSim737 (V-133) has provided improvement to the above issue.  Throttles can now be advanced to ~60% N1 and TOGA engaged without the throttle levers retarding.  This is possible ONLY if you calibrate the throttle levers within ProSim and allow ProSim to control the throttle output logic.  if you calibrate within FSUIPC then the same issue will apply.

According to ProSim developers, this issue is probably related to the calibration of the ProSim servo output. When you press TO/GA, the current N1 is taken and calculated back to a throttle percentage. This throttle percentage, when combined with the servo calibration data from ProSim results in a servo output. The servo calibration at the moment only has 2 calibration points, which are 0 and 100%. This results in a linear behavior between the two points, while depending on the construction of the throttle, the relationship might be non-linear. This would require a multi point calibration which is hard to do at the moment, because a throttle does not have exact readouts of the current position, so it will be hard to calibrate a 50% point.

This may need improvement in the code to auto calibrate the throttle system.

It's hoped that future release of ProSim737 will rectify this issue.

(B) Autothrottle Manual Override

In the real aircraft, manual override is available to a flight crew and the thrust levers can be retarded with the Autothrottle engaged.  When the flight crew release pressure on the thrust levers the Autothrottle will take control again and return the thrust levers to the appropriate position on the throttle arc dependent upon the speed indicated in the speed window of the MCP.

ProSim737 will not temporarily disconnect (manual override) the Autothrottle.  

At the time of writing, there is no workaround to solve this.

Potentiometers

There are many types of potentiometers; the two types most commonly used in flight simulation are the linear and rotary types. Linear potentiometers are inexpensive, often have a +- percentage variance, are compact, have a minimal throw depending upon the size of the device, and are not immune to contaminates building up on their carbon track. 

The last point is worth mentioning, as it is wrongly assumed that a potentiometer will remain correctly calibrated for the life of the unit.  General wear and tear, dust, and other debris will accumulate on the potentiometer; any of which may cause calibration and accuracy problems.  Keeping the potentiometers free of dust is important.

Rotary potentiometers (which may have a string attached) are very accurate, are in a sealed case and have very minimum chance of contamination. They are also made too exacting standards, are larger in size, and are expensive.

To read further about potentiometers

QAMP secured to base of throttle unit.  Thumb screws are visible on each corner of the plate.  A possible add on modification to reduce the risk of dust contamination to the potentiometers is a plastic cover that fits over the plate (a lunch box)

Calibration of Potentiometers

The main method of calibrating the position of the thrust levers is by calibrating the potentiometer in Windows, then in FSX followed by fine tuning in FSUIPC (if needed).  

At the moment I am using linear potentiometers; therefore, at some stage cleaning or replacement may be required.   The 737 throttle quadrant is not cavernous and only certain sized potentiometers will fit into the unit; this combined with other parts and wiring means that the potentiometers are often inaccessible without removing other components.  

To allow speedier access to the potentiometers, a Quick Assess Mounting Plate was designed.

quick access mounting plate (QAMP). four linear potentiometers are mounted to the plate. Two grub screws secure the plate to the throttle chassis

Quick Access Mounting Plate (QAMP)

The potentiometers are mounted directly onto a custom-made aluminum plate that is attached to the inside of the throttle unit by solid thumb screws.   To access the plate, the side inspection cover of the throttle is removed (a few screws) followed by turning the thumb screws on the access plate.  This releases the plate.

A similar plate has been designed and constructed for use with the stand-by potentiometer that controls the flaps.  A more detailed picture of the QAMP can be seen here..

Below is a video showing the movement of the thrust levers with the autothrottle engaged recorded during a test flight. 

 
 

Teething Issues with the Throttle Conversion

It was envisaged that more problems would have surfaced than have occurred.  The major issues are outlined below:

(A) Trim Wheels

An early problem encountered was that the trim wheels when engaging generated considerable noise.  After checking through the system, it was discovered that the two-speed rotation of the trim wheels were causing the two nuts that hold each of the trim wheels in place to become loose.  This in turn caused the trim wheels to wobble  slightly generating undue noise.  

Solution:

Tighten the two nuts at the end of the rod that holds the two trim wheels in place.

(B) Flaps 5 Not Engaging

The problem with the flaps 5 micro-button has been discussed in an earlier post.  To summarize, when you moved the flaps lever to flaps 5 the correct flaps were not selected on the aircraft or registered on the PoKeys 55 interface card.  Several hours were spent checking connections, micro-buttons, wiring and the custom VGA cables that connect the flaps section of the quadrant to the appropriate interface module; the problem could not be discovered.  

Solution:

One of the two Belkin powered hubs located within the IMM had been replaced with another powered unit.  It appears the problem was that the replacement hub had too low a voltage, as a replacement with a higher voltage solved the problem.

(C) Throttle Thrust Levers Not Synchronizing (A/T on)

The two thrust levers of the quadrant did not synchronize when the Auto Throttle (A/T) was engaged; one lever would always be ahead or behind of the other.  At other times they would split apart (do the splits) when A/T was engaged.  

Solution:

The problem was easily solved by altering the tension on the slip clutch nut.  When the nut was  tightened, both levers moved together as one unit.  The secret was finding the appropriate torque.

(D) Throttle Thrust Levers Difficult To Move in Manual Mode (A/T Off)

The ability to move the thrust levers in manual mode (Autothrottle turned off) was not fluid and the levers occasionally snagged or were sticky when trying to move them.  

The fan belt is barely visible linking the pulley of the motor to the main pulley inside the quadrant

This is caused by the fan belt not moving smoothly through the groove of the pulley wheel.   The Autothrottle when engaged overrides any stickiness due to the power and torque of the Auto Throttle motor.

Solution:

Unfortunately, there isn’t a lot you can do to rectify this issue as it’s a by-product of using a mechanical system in which the fan belt is central to the consistent operation of the unit.  

The conundrum is that if you tighten the fan belt too much you will be unable to manually move the thrust levers as they will be exceptionally stiff and difficult to move (as you are pushing against the tension of the fan belt); however, if you loosen the fan belt too much, although the levers will move fluidly by hand, the fan belt may not have enough tension to move the levers when Auto throttle is engaged.  It’s a matter of compromise; selecting an appropriate in-between tension to allow acceptable manual and Autothrottle operation.

A more reliable method is to use a small gearbox, a simple slip clutch and a coupler to connect to the spur gear.  Another option is to use an electrical system.

Further thought needs to be done in this area before a decision is made to replace the fan belt system.  If a new system is incorporated, the change-out will be documented in a future post.

Conclusion

Despite some of the shortcomings to this conversion, in particular the mechanical fan belt system, the throttle unit shows a marked improvement on the earlier 300 series conversion. 

Since the project began there has been three throttle conversions, with each conversion building upon knowledge learnt from earlier conversions.  Initially there was the 737-300 conversion that was completed in 2012. This conversion was rudimentary and the throttle operated only in manual mode (no autothrottle operation).  This was followed by the conversion in 2016 of the 737-500.  This throttle was then rebuilt and upgraded in 2017.

Further Information

  • A summary of the articles that address the conversion of the 737-500 series throttle quadrant conversion, and the rebuild and update can be found in Flight Controls/Throttle Quadrant.

Acronyms and Glossary

  • AFDS - Autopilot Flight Director system

  • A/T – Autothrottle

  • CMD A/B - Autopilot on/off for system A or system B

  • Flight Avionics Software - Sim Avionics, ProSim737 or similar

  • FMC - Flight Management Computer

  • MCP - Main Control Panel

  • QAMP – Quick Access Mounting Plate

  • Throttle Arc – The arc of the thrust levers from the end of the blocks to fully forward.  The term refers to the curved piece of aluminum that the throttle levers are moved along

  • TO/GA - Takeoff Go-around switch

  • %N1 -  Very simply explained, %N1 is throttle demand and as N1 (and N2) spin at absurdly high speeds, it is easier to simply reference a percentage and display that to the crew. It's much easier for our brains to interpret a value on a scale of 0-100% rather than tens of thousands of RPM