RNAV, RNP, LNAV and VNAV Operations - Overview

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Collins Mode Control Panel (MCP) showing lnav and vnav buttons

New flyers to the Boeing 737NG often become confused understanding the various terminology used with modern on-board navigational systems.

Although the concepts are easy to understand, the inter-relationship between systems can become blurred when the various types of approaches and departures are incorporated into the navigational system.

This post will not provide an in-depth review of these systems; such a review would be lengthy, confusing and counterproductive to a new virtual flyer.  Rather, this post will be a ‘grass-roots’ introduction to the concept of RNAV, RNP, LNAV and VNAV.  I will also touch on the concept of Performance Based Navigation (PBN).

In the Beginning there was RNAV

RNAV is is an acronym for Area Navigation (aRea NAVigation). 

Prior to complex computers, pilots were required to use established on-the-ground navigational aids and would fly directly over the navaid.  Such a navaid may be a VOR, NDB or similar device.  Flying over the various navaids was to ensure that the flight was on the correct route.  Often this entailed a zigzag course as navaids could not be perfectly aligned with each other in a straight line - airport to airport. 

When computers entered the aviation world it became possible for the computer to 'create' an imaginary navigation aid based on a direction and distance from a ground-based navaid.  Therefore, a straight line could be virtually drawn from your origin to destination and several waypoints could be generated along this line.   The waypoints were calculated by the computer based on ground VORs and positioned in such a way to ensure more or less straight-line navigation.

In essence, RNAV can be loosely defined as any 'straight line' navigation method similar to GPS that allows the aircraft to fly on any desired path within the coverage of referenced NAVAIDS.

Required Navigation Performance (RNP) and Performance Based Navigation (PBN)

Simply explained, Required Navigation Performance (RNP) is a term that encompasses the practical application of advanced RNAV concepts using Global Navigation Satellite Systems (GNSS).

However, there is a slight difference between RNP and RNAV although the principles of both systems are very similar. 

RNAV airspace generally mandates a certain level of equipment and assumes you have a 95% chance of keeping to a stated level of navigation accuracy.  On the other hand, RNP is performance based and requires a level of on-board performance monitoring and alerting.  This concept is called Performance Based Navigation (PBN).

RNAV and RNP both state a 0.95 probability of staying within 1 nm of course.  But RNP (through PBN) will let you know when the probability of you staying within 2 nm of that position goes below 0.99999.  In essence, RNP and PBN enable an aircraft to fly through airspace with a higher degree of positional accuracy for a consistently greater period of time. 

To achieve this level of accuracy a selection of navigation sensors and equipment is used to meet the performance requirements.  A further enhancement of this concept is the use of RNP/ANP (Required Navigation Performance and Actual Navigation Performance.  Advanced RNAV concepts use this comparative analysis to determine the level or error between the required navigation (the expected path of the aircraft) and the actual navigation (what path the aircraft is flying.)  This information is then displayed to the flight crew.

LNAV and VNAV

LNAV and VNAV are parts of the Flight Guidance System, and are acronyms for Lateral Navigation and Vertical Navigation'.  Both these functions form part of the automation package that the B737NG is fitted with.

LNAV is the route you fly over the ground. The plane may be using VORs, GPS, DME, or any combination of the above. It's all transparent to the pilot, as the route specified in the clearance and flight plan is loaded into the Flight Management System (FMS), of which the Flight Management Computer (FMC) is the interface.

The route shows up as a magenta line on the Navigation Display (ND), and as long as the LNAV mode on the Mode Control Panel (MCP) is engaged and the autopilot activated, the aircraft will follow that line across the ground. LNAV however, does not tell the plane what altitude to fly, VNAV does this.

VNAV is where the specified altitudes at particular waypoints are entered into the FMS, and the computer determines the best way to accomplish what you want.  The inputs from VNAV are followed whenever the autopilot is engaged (assuming VNAV is also engaged).  

The flight crew can, if necessary alter the VNAV constraints by changing the descent speed and the altitude that the aircraft will cross a particular waypoint, and the computer will re-calculate where to bring the throttles to idle thrust and begin the descent, to allow the aircraft to cross the waypoint, usually in the most economical manner.

VNAV will also function in climb and take into account airspeed restrictions at various altitudes and will fly the aircraft at the desired power setting and angle (angle of attack) to achieve the speed (and efficiency) desired.

There is not a fast rule to whether a flight crew will fly with LNAV and VNAV engaged or not; however, with LNAV and VNAV engaged and the autopilot not engaged, LNAV and VNAV will send their signals to the Flight Director (F/D) allowing the crew to follow the F/D cue display and hand fly the aircraft the way the autopilot would if it were engaged.

Reliance on MCP Annunciators

Flight Mode Annunciator (FMA) showing LNAV and VNAV Path Mode engaged.  The Flight Director provides a visual cue to the attitude of the aircraft while the speed is controlled by the the FMC.  CMD indicates that the autopilot is engaged (ProSim737 avionics suite)

LNAV and VNAV have dedicated annunciators located on the Mode Control Panel (MCP).  These annunciators illuminate to indicate whether  a particular mode is engaged. 

However, reliance on the MCP annunciators to inform you of a mode’s status is not recommended.  Rather, the Flight Mode Annunciator (FMA) which forms part of the upper area of the Primary Flight Display (PFD) should be used to determine which modes are engaged.  Using the FMA will eliminate any confusion to whether VNAV (or any other function) is engaged or not.

This post explains the Flight Mode Annunciators (FMA) in more detail.

Final Call

RNAV is a method of area navigation that was derived from the use of VOR, NDBs and other navaids.  RNP through it use of GNSS systems has enabled Area Navigation to evolve to include LNAV and VNAV which are sub-systems of the Flight Guidance System -  LNAV is the course across the ground, and VNAV is the flight path vertically. 

Historically, navigation has been achieved successfully by other methods, however, the computer can almost always do things better, smoother and a little easier – this translates to less workload on a flight crew.  

In my next post, we will discuss RNAV approaches and how they relate to what has been discussed above.

References

The information for this article came from an online reference for real-world pilots.

Acronyms and Glossary

  • Annunciator – Often called a korry, it is a light that illuminates when a specific condition is met

  • DME – Distance Measuring Equipment

  • FMA - Flight Mode Annunciator

  • FMC – Flight Management Computer

  • FMS – Flight Management System

  • GPS – Global Positioning System

  • GNSS - Global Navigation Satellite System

  • LNAV – Lateral Navigation

  • MCP – Mode Control Panel

  • ND – Navigation Display

  • NPA - Non Precision Approach

  • PBN - Performance-based Navigation

  • RNAV – Area Navigation

  • RNP - Required Navigation Performance

  • VNAV – Vertical Navigation

  • VNAV PTH – Vertical Navigation Path

  • VNAV SPD – Vertical Navigation Speed

  • VOR – VHF Omni Directional Radio Range

Throttle Quadrant Rebuild - Evolution Has Led to Major Alterations

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oem 737-500 thrust levers

Two major changes to the simulator have occurred.  The first concerns the throttle quadrant and the second is the replacement of the trial Interface Master Module with a more permanent modular solution.  The changes will be documented in the near future after final testing is complete.

The throttle quadrant has been completely rebuilt from the ground up.  Although the outside may appear identical to the earlier quadrant, the rebuild has replaced nearly everything inside the quadrant and the end product is far more reliable than its predecessor.

The throttle unit, in its previous revision, worked well, but there were several matters which needed attention.  The automation and functionality was adequate, but could be improved upon.  There were also 'niggling' issues with how the clutch assembly operated - it was somewhat loose which caused several flow-on problems.

Initially, some minor improvements were to be made; however, one thing lead to another and as 'fate would have it' the throttle unit has been rebuilt from the bottom up.

Improvements

The improvements have primarily been to the automation, the autothrottle and the speedbrake system.  However, during the rebuild other functionality have been improved: the synchronised tracking movement of the thrust levers is now more consistent and reliable, and an updated system to operate the parking brake has also been devised.  This system replicates the system used in the real aircraft in which the toe brakes must be depressed before the parking lever can set or disengaged.

Furthermore, the potentiometers controlling the movement of the flaps and thrust levers have been replaced with string potentiometers which increases the throw of the potentiometer and improves accuracy.  The calibration of the flaps and speedbrake is now done within the system, removing the need for 'tricky' calibration in FSUIPC. 

In the previous throttle version there was an issue with the speedbrake not reliably engaging on landing.  This in part was caused by a motor that was not powerful enough to push the lever to the UP position with consistent reliability.  This motor has been replaced with a motor more suitable to the power requirement needed.  The speedbrake is mechanical, mimics the real counterpart in functionality, nd does not require software to operate.

This throttle conversion has maintained the advanced servo card and motor that was used to control the movement of the stab trim tabs (trim indicators); however, the motor that provides the power to rotate the trim wheels has been replaced with a more reliable motor with greater power and torque.  The replacement motor, in conjunction with three speed controller interface cards, have enabled the trim wheels to be rotated at four independent speeds.  This replicates the four speeds that the wheels rotate in the real 737 -800 aircraft.

Finally, the automotive fan-belt system/clutch system which was a chapter from the 'Dark Ages' has been replaced with two mechanical clutch assemblies that has been professionally designed to operate within the throttle unit - this will completely remove any of the 'niggles' with the previous clutch assembly becoming loose and the fan belt slipping.  Each thrust lever has a dedicated poly-clutch and separate high powered motor. 

A brief list of improvements and changes is listed below:

  • Next Generation skirt replaced with more accurate skirt (prototype);

  • Reproduction TO/GA buttons replaced with OEM square TO/GA buttons;

  • Fan belt driven clutch system replaced with slipper clutch system;

  • motors replaced that control lever movement and trim wheels;

  • 95% of wiring re-done to incorporate new interface modules;

  • Replacement interface alert system;

  • Flap potentiometers replaced by string potentiometers;

  • Speedbrake potentiometer replaced by linear potentiometer;

  • Thrust levers potentiometers replaced by dual string potentiometers;

  • Internal mechanism altered to stop noise of chain hitting throttle frame;

  • Thrust lever tracking movement accuracy improved;

  • Thrust reversers now have proportional thrust for each lever 1 and 2; and

  • The parking brake mechanism replaced with a more accurate system that reflects that used in the real aircraft

The conversion of the throttle quadrant has been a learning process, and the changes that have been done improve the unit's functionality and longevity - not too mention accuracy, far beyond what it was previously.

Dedicated Interface Modules

The throttle previously interfaced with the Interface Master Module (IMM).  The IMM was developed as a trial module to evaluate the modular concept.

The throttle quadrant will now directly interface with two dedicated modules called the Throttle Interface Module (TIM) and Throttle Communication Module (TCM).  Both of these modules contain only the interface cards, relays and other components required to operate the throttle and automation.  Additionally, the system incorporates a revised Interface Alert System which evolved from the original concept used in the IMM.

To read more concerning the various interface modules, a new website section has been produced named Interface Modules.  This section is found in the main menu tabs at the top of each page.

Flight Testing (March 2015)

The throttle and replacement interface modules are currently being evaluated and minor issues rectified.

Once testing is complete, the alterations undertaken during the rebuild process will be documented in separate posts and, to facilitate ease of searching, links will be added to the flight controls/throttle quadrant section.

It should be noted that the work done to rebuild the throttle was done with the help a friend, who has a through knowledge of electronics and robotics.

Navigraph Charts Cloud and Charts Desktop - Review

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The traditional leather-bound binder that contains hundreds of Jeppesen charts.  This particular binder belonged to Gene Mac Farland, a Captain who flew for 30 years with Continental Airlines

One aspect of simulation which is identical to the real thing is the use of charts.  Whether a professional real-world pilot approaching Heathrow International or a virtual pilot, the correct approach chart will need to be consulted, interpreted correctly, and followed if a safe landing is to be assured.

Not so long ago, Jeppesen Charts provided the mainstay for all professional navigation charts and these thin paper charts were carried in a brown leather binder.  Pilots carried a number of binders with them to allow access to the appropriate chart where necessary.  It was the responsibility of the pilot to ensure that the contents were up-to-date and reflected the latest chart; a tedious task.

Later years have witnessed the introduction of computers and several companies, including Jeppesen, have provide electronic charts that can be viewed using laptops, smart phones and apple i-pads.  The days of  lugging binders is now over, and a binder such the one depicted in the above photograph have become, for the most part, keepsakes and door stops.

Collecting Charts

Virtual pilots have a tendency to ‘collect’ charts from innumerable locations.  The collection can become quite large, and often it is difficult to collate the charts in such a way that it is easy to find the wanted chart, let alone know whether the chart is the most accurate up-to-date version.  

Navigraph

Serious simulator enthusiasts have probably heard of the European-based company Navigraph.  For several years the company has been responsible for the production and distribution of AIRAC cycles that are used to update the Flight Management System (FMS) to maintain the accuracy of the navigation database.

AIRAC Cycles

AIRAC is an acronym for Aeronautical Information Regulation And Control.  An AIRAC cycle contains the current aviation regulations, procedures, and charts for airport, runway, airspace, Instrument Approach Procedures (IAP), Standard Terminal Arrival Routes (STAR), and Standard Instrument Departures (SID).  The AIRAC cycle updates the database used by the aircraft's FMC/CDU.

Without this up-to-date data it is not possible to program the FMC/CDU with any degree of accuracy. 

Navigraph provide a subscription service to AIRAC cycles which are updated several times a year (usually there are thirteen cycles per year)

Charts Database

Navigraph, in addition to supplying regular updated AIRAC cycles, has implemented three additional products:  airport charts, video tutorials and en-route charts.  These products are available via an annual subscription from a data cloud database and/or desktop program.

 

Area of coverage of Navigraph charts (image courtesy of Navigraph).  This link provides an up-to-date coverage area for Navigraph charts

 

Airport charts include up-to-date charts for approximately 13,000 airports worldwide. Chart information includes at a minimum: runway data, instrument approach procedures, standard terminal arrival routes and standard instrument departures.  To date, there are approximately 40,000 charts and the number is regularly being expanded with quarterly updates.

Furthermore, several dozen video tutorials instructing in the correct interpretation and use of approach charts are available in addition to dozens of en-route charts which include upper and lower airways.  

The information depicted on the charts originates from suppliers of real-world aviation charts (Navtech) and depicts the latest data, in a format that has been designed by human factor research to be user friendly.

Unlike other companies that have attempted to provide charts for virtual pilots (for example, sim charts), Navigraph charts have been vector scanned in high resolution providing a dataset that can be easily enlarged as required, read, and if required printed in high definition.  Additionally, the information is in colour.  

Ease of Access - Key Feature

In a nutshell, Navigraph has allowed a virtual pilot access to information that otherwise would require considerable collating, revision, and pose difficulties concerning easy access when required. The datasets can be immediately assessed on demand either from a data cloud (charts cloud) or via a desktop program (charts desktop).  

Granted there are many on-line resources to find, read and print approach charts - some better than others.  However, the Navigraph search functionality allows the right chart to be found, quickly and easily, at the appropriate time.  In my opinion, this promotes Navigraph over others programs and on-line resources.

Screen capture of charts cloud showing list of available charts for Hobart, Tasmania, Australia.  The chart can be viewed full screen and can be enlarged as required.  Note this screen capture is of a very reduced quality

Charts Cloud

The cloud provides an easy to use on-line interface, with an effective search functionality that can be accessed using different platforms, including portable devices such as i-pads and smart phones.  To allow speedier future access, charts can be placed in a favourites list or listed in a paper clip (a separate folder) that is linked to your account.  The charts cloud does not allow printing or permanent downloading of a chart and charts are only available when on-line.  Access to the data sets ceases after the annual subscription has expired.

The speed at which charts cloud database can be accessed relates to the Internet connection being used; however, for the most part the server Navigraph uses provides consistent access that should be suitable for most users, with the exception of those that use dial-up.

Navigraph Charts 4 desktop opening screen

Charts Desktop

The charts desktop is a program supplied by Navigraph (free of charge), which resides on your computer and allows charts to be downloaded for access when off-line.  This has the obvious benefit of faster access times if the Internet connection is less than optimal.

The program has the capability to list charts as favourites for easy and fast access, in addition to having a highly responsive search engine.  Unlike the charts cloud, the charts desktop allows access to any chart that has been downloaded after the annual subscription has expired; however, after the subscription has expired the charts cannot be updated.  Another benefit in using the program is that charts can be printed.

Updates

Navigraph regularly updates the database with additional charts and changes to pre-exisiting charts.  The program advises you of an update when you mouse over the chart name.  The program will then allow you to maintain the existing chart or download and replace the chart with the newer version.   Updates are usually half a dozen times a year

Is it a Worthwhile Investment ?

Whether Navigraph chart data is of benefit to you will depend upon how many different airports you fly from and to, how often you fly, and how much money you are prepared to shell out for the convenience and ease of accessed chart information.  Certainly, it is far easier to maintain a collection of charts electronically than store several binders of paper!

A subscription (using the charts cloud or desktop program) is currently 47.92 Euro excluding VAT.  This price allows unlimited access to all charts, and includes the ability to view all instructional videos, which have been professionally produced and run each for approximately 8 minutes duration.  Short of a subscription, individual charts and videos can be purchased separately for a once off fee.  In contrast to purchasing the Jeppesen electronic charts from Jeppesen or an ongoing seller, this fee is reasonable.

Short Review

I elected to not write an in-depth review of Navigraph and their products as the Navigraph interface and their products are constantly being upgraded.  A review may soon be out-of-date!  This review has dealt primarily with the airport charts and has not examined in details the en-route charts or training videos that come packaged with a charts cloud subscription.

Navigraph’s website is very comprehensive and includes several images of their charts that depict the high quality of their product, along with examples of the various programs and how they operate. 

Whilst the charts are not 100% identical to Jeppesen real-world counterparts (various information has been merged and interpolated), the detailed datasets, consistent high quality, and ease of searching and accessibility, make the administrative aspect of virtual flying more enjoyable.

Disclosure

The content in this post is not meant to directly promote or endorse Navigraph.  To trial this software, I purchased a subscription to the charts cloud and charts desktop.  To date, I have been very pleased with the quality of the Navigraph charts and will probably continue to supplement my real-world paper charts with information from this source.

UPDATE: There have been massive changes and improvements to Navigraph since this article was published. A more up-to-date review will be written at some stage. Navigate to the Navigraph website.

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 lense.

  • MIP - Main Instrument Panel.

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

  • RAL - International colour matching system.

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

OEM Boeing 737 Control Columns - A Closer Look

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OEM Captain-side 737-500 series control column.  Previously used by Croatian Airlines

The two control columns have been refurbished and installed into the simulator.  The control columns previously were used in a 737-500 airframe operated by Croatian Airlines. 

I was fortunate to have been able to secure these columns, and although there is some wear on the yokes, the buttons, electric trim switches, chart holders, and trip indicators are operational and in good condition.  Furthermore, a working stick shaker is attached to the captain-side control column.

In this article, I use the words control columns and yoke interchangeably.

Mechanical Set Up

To allow the two columns to be fitted to the 5 inch high platform, the lower cogs have been removed and replaced with bearings.  The bearings support a high strength stainless shaft that connects to a rotating disc beneath each of the columns; movement is synchronised between control columns.

Physical movement of the control column is registered by high-end string potentiometers and any movement converted to an electrical signal that can be read by the interface card.  The interface card used is a Leo Bodnar 836X joystick controller.

The interface card, electrical wiring and potentiometers are installed on a piece of plastic board mounted to a dust proof box and attached to the underside of the platform.  Access to the box is via the front of the platform.

Push and Pull Pressures

In the real Boeing 737 aircraft the control columns are hydraulically driven, and a fail-safe cable mechanism provides redundancy should the hydraulics fail.  The 737 is rather unique in that, although hydraulics control movement of the control column, the pressures needed to move the columns (by hand) are quite stiff.  Therefore, hand flying a 737 can be quite tiring; you must use a little muscle to move and maintain the position of the controls.

The specifications for the real aircraft state that the control column has a 37 pounds push/pull value +- 4 pounds, while the roll pressures are 12 pounds +- 3 pounds.  These pressures can differ from aircraft to aircraft, but fall within the published specifications. To replicate the push, pull and roll forces as accurately as possible, four heavy duty springs have been fitted to the column mechanism. 

Heavy duty pre-tensioned springs provide accurate static control loading

The control column pressure can be adjusted by either replacing the springs with higher or lesser tension springs, or by disengaging the outer springs. 

A pressure test determined that push/pull pressure is 20 pounds and roll pressure 15 pounds.  The push/pull pressure is on the low side, however, will be left as is for the time being.  Springs have been used rather than hydraulic rams due to the simplicity of a spring and ease of replacement.

Although the use of springs is rudimentary, it's acts as an interim measure until control force feedback is installed.  When this is done, the force required to move the control column will alter based on aircraft's speed, flap setting, landing gear position and other environmental variables.

The video at the bottom of this article demonstrates the linkage mechanism and springs in motion.

Configuration - Movement and Buttons

Configuration of the control columns is straightforward. Although there are two control columns, each column is linked to the other.  Therefore, only one interface card is required.  The buttons on the yoke, and the electric trim switch are connected to the outputs on the interface card.

Initial registration of the movement of the yoke and buttons is established in the Windows joystick calibration software.  Further calibration is either done directly in the flight simulation program, FSUIPC, or in ProSim737.  Although it is possible to assign buttons directly via the flight simulator set-up menu, the preferred method is to use FSUIPC or ProSim737.

Backlighting (Trip Indicators)

The actual yoke doesn't have backlighting; any illumination of the yoke is achieved by focusing the map light which is attached to the overhead panel.  However, the numbers on the trip indicators do have backlighting (to illuminate the numbers). 

Trip indicators are an airline specific option and do not come as standard issue.  Pilots use the trip indicator to 'scribe' the flight number of the flight, or to document the Vref speed.  Some crews never use the indicators.  I use the trip indicator as a ready memory pad to document the landing Vref speed (Vref+5).  The backlighting for trip the indicators is powered by 5 Volts.

oem chart holder and cheat sheet

Chart Holders

The chart holder is used to secure the approach plate (paper chart) in an area that it can easily be read during flight operations.  The chart holders have a folding mechanism beneath the plate that allows the holder to be either pushed flush to the yoke, or positioned at a user-selected angle. 

Another function of the chart holder is to provide a ready memory jogger for specific flight modes (checklist).  The adhesive transfer on which this information is printed is specific to each aircraft type and /or airline.  illumination of the chart plate, like the yoke, is achieved using the map light.

OEM Verses Reproduction

Several companies manufacture reproduction control columns: Precision Flight Controls (PFC), CH Products, Revolution-Sim and Ace Engineering to name a few.  Over the years I have used products from ACE, CH Products and PFC.  Without transgressing into a 'tit for tat' argument, you get what you pay for.  

A CH yoke retailing at $100.00 cannot be compared with an ACE yoke retailing around $1300.00, however, both products have been manufactured to cater towards differing segments of the market.  This said, the difference between ACE and PFC is marginal.  I cannot comment on Revolution-Sim having not used their products. 

So what is the different between a high-end reproduction yoke and a OEM yoke and column?

The main difference is the feel and finesse of the genuine item.  Boeing has spent a lot of money (more than PFC, ACE or Revolution-Sim combined) in the development and engineering of the control column, and this is very difficult to replicate in a reproduction.

The OEM yoke and column is engineered to provide faithful service for many years.  It's also built to suffer use and abuse from real-world pilots, and I am certain anything a virtual pilot can throw at it, will not cause any damage.  The buttons and electric trim switches are solid, feel good to manipulate and are very reliable.

Yoke Performance

The yoke moves left and right across its range of motion with a smooth and silky feel without staggering, binding or rough patches.  Likewise, the columns move forward and aft very smoothly.

The electric trim switches are far more responsive than the reproduction switches I have used.  A slight application of pressure to the switch engages the electric trim.  The electric trim switches response is a akin to a hair trigger on a firearm - it only needs a light touch to engage. 

The control column is very responsive, and if calibration has been done correctly, very accurate.  If the yoke is turned 15 degrees to the left, the measurement on the aileron tape is exactly 15 degrees.

Synchronization

I was concerned that synchronisation between the two control columns would not be perfect, however, my concern was short-lived.  The use of high-end bearings at the end of the control linkages removes any chance of slop (loose movement) between the two control columns. 

Yoke Switches

  • OEM 737 yokes have several switches and buttons.

  • Momentary press push button - auto pilot deselect.

  • Momentary rocker switch - electric trim up/down. This switch is interesting as it incorporates redundancy.

  • Momentary rocker - push to open channel (push to talk PTT).

  • Rocker switch - Intercom.

  • Trip Indicator - used as memory aid for flight number.

oem 737 flight controls in simulator

Appearance of Yoke - Used Look

If you carefully study the pictures of the yokes, you will observe that the yokes are not pristine condition, but show solid use (and probably abuse when it was striped from the aircraft).

The baked-plastic covering of the yoke shows scratches and some of the metal has been rubbed clean of paint.  Some enthusiasts dislike this look and prefer a brand new 'out of the showroom' appearance.  If this is you, then I suggest an OEM yoke may not be for you, unless you wish to completely overhaul the yoke and pay the large amount of money required to re-bake the plastic coating.

I like the 'used' look and feel it adds to the simulator.  I have been in many cockpits, and very rarely do you find a flightdeck in brand new condition, other than in the first few months of service.  More often than not, gauges, yokes and panels are scratched, dented and stained from many hours of sustained use from individuals that are more interested in flying, and going home after the flight, than maintaining the desk!

Below is a short video showing the under floor mechanism, springs and linkage rods.  If you listen carefully you will hear the springs creaking.  This is not an issue when the simulator is running as any noise is cancelled out by the noise of the engines and flight deck ambient noise (electrics, 400 hertz noise and wind).

 
 

Glossary

Control Wheel - Yoke.

FSUIPC - Flight Simulator Universal Inter-Process Communication (interface software that provides a bridge between flight simulator and outside programs).

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

  • Updated 20 June 2020.

ProSim 737 Glass Cockpit Avionics Suite - Review

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prosim 737 version 1 opening screen

The ProSim737 Glass Cockpit Suite is software developed solely for the Boeing 737-800 aircraft and replicates the avionics required for the operation of the flight deck. ProSim737’s beginning was meager, however, the ongoing development, accuracy, functionality and above else, ease of use and reliability, has ensured that ProSim737 has an exceptionally strong following.  

The developers are based in Luxemburg which is why many users of the software are European based; however, flight simulation transgresses geopolitical boundaries and many users of ProSim737 are located in Asia, Australia, New Zealand and North America.

I’m not going to duplicate what can easily be read in the ProSim737 user manual.  The manual outlines much of what the software can and cannot do and I urge potential buyers to read it.

This review pertains to software release Version 1.

First Off - Caveat Emptor (Latin for buyer beware)

Before continuing, there are several flight avionics suites currently available on the market.  They all replicate the basic avionics functionality of the B737.  However, not everything is operational within each suite, and some functions behave differently between suites.  Therefore, it’s a good idea to research what works and what doesn’t before your purchase.  I have a written an earlier journal post addressing this.

Avionics Suite – The Heart

The heart is the most important organ in the human body.  Likewise, the avionics suite is the heart of the flight simulator, and provides the interface for instrumentation to operate.  If the software used is not reliable, robust and well tested, then problems may develop which ultimately will lead you into a minefield of frustration and confusion as you attempt to unravel the intricacies of the Boeing avionics system.

ProSim737 – Overview and Detail

ProSim737 is a complete avionics solution providing the ability to support all displays and logic found within the B737-800.  The software has been designed to run on one or multiple PC's in various configurations interfacing with FS2004 (FS9) or FSX, via a paid and registered version of FSUIPC.  Wide FS is not required, however can be used if networking other add- on programs.

To achieve this, the software is segregated into four broad modules: PS737 System, PS737 Display, PS737 MCP, and PS737 CDU.  Additional modules are PS737 Audio and PS737 Panel. 

I’ll discuss the details of each briefly.  For a more though dissection, I direct you to the ProSim737 website or user manual.

A short video at the bottom of this post will guide you through the various menus of the ProSim737 Systems Module.

PS737 Systems Module

The Systems Module is the main component of the ProSim family and it’s within this module that configuration of the switches, indicators, drives, and gauges occur.  In addition to providing the detailed logic to replicate the following aircraft systems and components: electrical, pneumatic, fuel, hydraulics, heating, fire detection, IRS and master cautions, the module provides access to a web-based instructor station and server that other ProSim737 modules connect to and from.

The Systems Module, because it houses the server, must be installed on the computer running flight simulator.  Likewise, for any other module to operate, the Systems Module must be opened.

PS737 Display Module

As the name implies, this module supports the main visual displays located in the Main Instrument Panel (MIP) that a pilot views when in the flight deck.  The module also provides several additional “virtual” gauges, such as clocks, stand by instruments and a flaps gauge for those flight deck builders who don’t use reproduction hardware gauges, or converted real instruments.

The following displays and gauges are included in the display module.

  • Captain and First Officer Pilot Flight Display (PFD) and Navigation Display (ND) -  various      configurations

  • EICAS display (upper & lower) with fully integrated EICAS messaging

  • Virtual Main Control Panel (MCP)

  • Virtual EFIS display (two)

  • Virtual overhead panel (forward & aft)

  • Virtual CDU display

  • Virtual stand-by instruments (good selection)

If you’re operating a full flight deck with appropriately supported hardware you won’t require the virtual MCP, EFIS, CDU and overhead displays.

prosim 737 virtual mcp

ProSim737 MCP Module

This module controls the Mode Control Panel (MCP) which is the auto pilot system in the aircraft.  The MCP communicates with the logic coming from the systems module to provide information regarding altitude, direction, speed and other auto pilot constraints.

ProSim737 allows the user to either configure the MCP as a “virtual” MCP panel displayed on a computer monitor, or for builders using a hardware MCP, display minimised.  The virtual MCP includes two Electronic Flight Instrumentation System (EFIS) modules in either Honeywell or Collins configuration.

This MCP module usually resides on the same computer as the systems module.

ProSim737 CDU Module

The Control and Display Unit (CDU) is used to assess information from the Flight Management System (FMS).   A user can either use one, two or any number of instances of the “virtual” CDU and each will display identical information.  If a hardware CDU is being used, there is the ability to turn off the “virtual” CDU and display the data on the hardware unit.  All CDU instances are linked to each other via the ProSim737 Systems Module.  It’s usual practice to install and run this module from a client computer.

ProSim737 Audio Module

The audio module is a stand alone module that allows user customised sounds to be played when various preset functions occur, such as when switches are toggled, speeds are reached, etc.  This module is needed to allow GPWS and TCAS cautions, in addition to V1, V2, Vr and altitude call outs.  The module can be installed and run from any computer and links to the ProSim737 systems module.  The module runs as an additive to ProSim737’s internal sound (located in the Systems Module).

The virtual forward overhead panel.  Many switches are functional and can be moved with the mouse

ProSim737 Overhead Module

This module provides the switches, gauges and dials for the forward and aft sections of the overhead.  The module is installed on the client computer and is usually left open full screen, unless you have a hardware overhead installed.  The module supports functionality essential to the basic operation of the B737.

Reliability, Robustness & User-Friendly

When you evaluate a product, it’s “usually” fairly easy to find inherent problems.  ProSim737 is a different beast; since I began using their software I have not had any problems that suggest inherent problems with the underlying software framework.  It’s a pleasing experience when you open software and it “just works”. 

Of course, variances between computer systems and a wide variety of FS add on programs, can cause minor nuisances to occur – this is normal with any software.

To avoid any issues, I advise that all flight simulator add on programs be removed before evaluating a software suite.  Once you’re happy that everything is functioning as it should, add each FS add on in turn, checking to ensure correct operation.  If a problem does occur, at least you will know which program is causing the issue.

ProSim737 is an exceptionally robust software platform and the program has never crashed despite me changing configurations, etc “on the fly”.  

Software Installation

Simplicity and easy of use are the mantra of the developers of ProSim737.  Opening the ProSim737 package will reveal a number of appropriately named folders.  To install the Systems Module you click an executable file and install to the computer on which flight simulator is installed.  The other folders are then copied to the client computer.  IP addresses must be known to allow communication between modules across the network.

You don’t have to open .ini files or configuration files during installation and you don’t need to copy and paste files between folders.  Basic configuration is achieved by right clicking the mouse which opens a configuration screen.  The set-up is uncomplicated and is logically set out.

The only files you need to cut and paste to a folder are the terrain files and navigation database.  Detailed instructions on how to do this are documented in the comprehensive and well-written manual.

prosim 737 Configuration display when using right mouse click - everything is easy to find and configure with minimal time outlay

Learning Curve and Ease of Use

Any new software has a learning curve; however the curve is very shallow when using ProSim737.  You don’t have to be a programmer or have in-depth computer knowledge to install or use ProSim737.  The software is very easy to install, configure and maintain. 

For example updates, which are frequent, do not require you to manually cut and paste a new version download to several folders.  An update button within the Systems Module completes the update task within minutes.  As you open other modules, they each in turn are updated from the Systems Module.

Another example, which shows the ease of use relates to the configuration of various displays provided in the ProSim737 Display Module.  To set-up a dedicated display, you mouse drag the required display to the monitor of choice and then right click the window to open the configuration menu; resizing the display is done using the mouse.  To avoid the problem of the display accidentally changing size in the future, you tick the “freeze constraints” box. It literally takes less than 10 minutes to establish the visual displays in the flight deck!

Configuring Your Switches and Buttons

Configuring buttons and switches to your set-up relatively uncomplicated involving opening a menu in configuration mode, scrolling to find the particular function you need, and then connecting the output type to a specific output.  Granted there is a learning curve, but the curve is low and essential tasks don’t requite extensive knowledge of computer code.  

Similarly, customised audio files can be added, linked and played in the Audio Module.

Navigational Database and Terrain Files

ProSim737 does not provide the navigational database that is needed by the aircraft.  This must be purchased as a separate item from Navigraph.  This is normal practice and all developers rely on Navigraph to maintain the latest navigation package. 

Installing the database requires you download the data and then extract the data, via an executable file, to a specific folder within ProSim737.  You then must build the database which is achieved by pressing a button within the configuration menu.  

Similarly, the terrain files must be downloaded from the ProSim737 website and manually copied to the appropriate folder.

Driver & Hardware Support

Today, there are several vendors ranging from high end to budget level that are replicating B737 hardware and instrumentation.  ProSim737 development is forward based, meaning they understand the need for avionics software to be compatible with as many hardware types as possible.  Flight Deck Solutions, Engravity, Go Flight, CP Flight, SISMO and Open Cockpits are all supported and several types of I/O cards are supported such as Pokey, FDS SYS and phidgets.  FSUPIC and FSUPIC offsets are also supported by ProSim737.

Determining which hardware is selected for your set-up is as easy as checking a box within the configuration screen of the Systems Module.  

Accuracy and Resolution of the Flight displays

You spend a lot of time staring at the various displays, whether it’s the Pilots Flight Display, Navigation Display, CDU or EICAS; therefore, it important that the graphics are of the highest quality possible; nothing is worse than staring at jagged corners, off-putting colours, or blurry lines.  

Although the quality of any graphics is linked to the resolution of the computer screen, if you use a high resolution screen you will not experience any anomalies associated with poor graphics.  The display graphics are crisp and sharp. 

  • To see images of displays navigate to the ProSim737 website.

All simulation enthusiasts strive for accuracy; some to a greater extent than others.  The displays depict what you would see if you were looking at the displays in a real B737 main instrument panel.  Only the very keen you will note the odd subtle difference between the simulation and the real display, and this is often determined to a certain extent, by the cockpit set-up and carrier options you select from within the instructor station.  

For example, the magenta course line in the Pilots Flight Display appeared to be slightly thinner than on the real aircraft, but no sooner had I noticed the disparity that Marty at ProSim737 had uploaded an update rectifying the issue.

What’s important to realize, is that the developer listens and if inaccuracies are noted rectifies the disparity quickly and without argument.  

ProSim 737 Screen grab showing variations of PFD and ND displays dependent on EFIS setting

Precision

Any software must provide precise outputs when its logic is queried; all virtual pilots demand that software outputs be precise in execution.  To date, ProSim737 has lived up to its reputation and I cannot highlight any major downfall in the precision of the software. 

ProSim 737 Screen grab showing variations of PFD and ND displays dependent on EFIS setting

Vertical Navigation (V-Nav)

A common thread in FS forums is that avionics software has difficulty in replicating Vertical Navigation (V-Nav).  This is especially evident with software supplied by Project Magenta and to a limited extent with Sim Avionics. 

ProSim 737 Screen grab showing variations of PFD and ND displays dependent on EFIS setting

The logic used to replicate V-Nav is not simple; it’s complicated, and the variability in V-Nav usage often causes issues to develop when using V-Nav.  The main problem is that the aircraft may not keep within the constraints entered into the CDU.  Often the aircraft will either over fly an altitude constraint or not maintain a entered speed constraint.

From the outset, V-Nav in ProSim737 has worked exceptionally well.  Altitude and speed constraints, if entered correctly, are maintained and the reliability of V-Nav surpasses those of other software suites I have used.

V-Nav Usage

V-Nav, even to qualified pilots can be a challenge to use correctly.  This is one reason why V-Nav should only be used as a guide and not as an absolute.  If V-Nav, for whatever reason does not function in a method you think is correct, then turn it off and use the more reliable L-Nav, Level Change or Vertical Speed functions.

The challenge, I have discovered when using V-Nav is two-fold.  First, you must use it within the designed capabilities of the program, and two, you must learn how and when to operate V-Nav.  If you enter data that the FMS cannot assimilate, such as an altitude that is too high or too low, for the time required to reach the waypoint, then expect an over fly of the entered restrictions.  This is not the fault of the software, but the fault of the user.

Display Lag

Display lag is term coined to explain the staggering of a display due to information overload, information bottleneck or lack of computer graphical power.  It typically manifests itself when a lot of information is required to be displayed at an identical time that computer processing is required.

For example, another software suite I have used displayed staggering on the altitude tape in the Pilots Flight Display (PFD) when ascending and descending with the “all waypoints” selected from the EFIS.  The staggering stopped when the “all waypoints” were deselected.

I have yet to experience any display staggering with ProSim737, even with the terrain simulation display activated.  

Weather & Terrain Display Functionality

The weather and terrain display function, which is activated either by pressing WXR or TERR on the EFIS unit is functional in ProSim737, however, the weather display is inaccurate and looks very outlandish in its “blocked in” colour display.  

I’m lead to understand that the weather functionality present within other software (Sim Avionics), reads directly from weather depicted by FSX, and then only presents a rough indication of what the weather maybe like at that particular time; it certainly does not mimic and display what the aircraft is actually flying through or about to fly through.  

I am hoping that the developers at ProSim737 will develop a radar module that actually reads the exact weather depicted in FSX and display this weather in a way that is similar to the real radar in the B737.  At the time of writing, the weather displays only in solid colours and does not mimic how real radar operates.  I hope that ProSim737’s developers improve this in due course.

ProSim 737 terrain files (two choices)

Two Terrain File Resolutions

Pressing the terrain (TERR) button on the EFIS unit, displays a graphical representation of the surrounding terrain on the Navigation Display.  There are two variations of the terrain graphics available; one display is slightly blocky and the other display is more detailed.  To select which display is active, right click the screen with your mouse and tick the appropriate box in the configuration menu.


Compatibility of Aircraft with ProSim737

It's always been a concern to what add on aircraft you can use with a particular avionics package.  As an example, Sim Avionics provides several aircraft .cfg files which have been tweaked to their software.  You load the particular aircraft.cfg file for the aircraft you are using and any vagrancy between the aircraft and avionics software is rectified.

ProSim737 has taken a completely different approach and designed a flight model called the JetStream 738, which is tweaked to operate flawlessly with ProSim737.  Of course, you don’t have to use the JetStream if you don’t want to; the default B737 can be used as can the PMDG B737 FS9 version with flight logic removed.  

I will review the JetStream738 in a separate journal post.

CDU - Background Software

No review of any avionics software is complete without a short segment on the CDU.

The ProSim737 CDU module is the controlling software that provides the intelligence behind the CDU.  It's amazing what this software can do, and do so with reliability and consistent behaviour.  More importantly, the software does not crash, even when incorrect data is inputted to the unit.

Many pages associated with a commercial CDU are modelled and updates continue to add new features and improve existing functionality. 

In the real B737 aircraft, not all CDU software is identical.  There are different software versions and each version has slightly different functionality; it’s the decision of the airline to which software version is chosen.  Likewise, not every company producing avionics software models the CDU identically.  In some respects, it depends on which software edition the developer has chosen to replicate. 

Unfortunately, many developers choose to not replicate something or to not provide full functionality.

Often CDU menus and pages may look similar in appearance, but you will be disappointed when trying to access a feature that appears to be modelled but has no functionality.  Some suites offer far greater functionality than others.  I believe ProSim737 provides more functionality than other higher end CDU software available, and more functionality is regularly added through software updates.

Some of the basic features modelled by the CDU software are:

  • Indent page on start-up (weights, fuel, fuel reserves, cost index, cruise altitude, etc)

  • Approach reference page with VREF selection

  • Route, LEGS, Arrival, Departures & Holding pages (user controlled including approaches, STARS, SIDS & transitions)

  • Progress pages (fuel, distance to go, ETA, wind, crosswind component, cross track error, fuel prediction etc)

  • Vertical Bearing Indicator (VBI)

  • V-Nav & L-Nav compliant (climb, cruise and descent)

  • Ground Service - push back

  • NAV/COM radio reference page (ADF, ICAQ, VOR & ILS data) & search

  • ACARS (future installment)

  • Captain & First Officer EFIS control

  • OAT

  • SIM MAINT page (separate commands to control SIM instead of using keyboard) such as pause, freeze & re-set FMC.

The software lacks the ability save a flight plan directly from the CDU; you must use the instructor station to save a flight plan. Also, it’s not possible to reverse a route from the CDU.  It would be helpful if this functionality can be implemented.

The software is compatible with CDU hardware produced by Fly Engravity and Flight Deck Solutions.

prosim 737 ios showing CAT visibility and push back & failures menu

Instructor Station

The instructor station included with the software is a web-based station, meaning you type in the appropriate address into the browser web bar and the instructor station opens on any computer connected to your network – even a laptop.  No other software is needed.

The instructor station is comparatively simple in layout, yet functional.  Without repeating the user manual, which outlines in detail what each section comprises, the station displays the following menus: Quick Start, Cockpit Set-up & Carrier Options, Global Database, Situations & Positions, Company Routes. Flight Plans and Failures.

prosim 737 ios failure screen

Two Instructor Station functions  deserve mention

Company routes allow you to store and manipulate routes you have loaded into a specific folder within ProSim737.  These routes, if not manually built using the CDU and FMS and saved to the instructor station, are usually downloaded from on-line route generators.  As the station has a built in editor these routes can easily be edited and re-saved.  You can also download from the station to the CDU any selected route.

The situation menu I find particularly useful.  Here you can instigate push back, execute day or night and switch to real time at the push of a button.  You can also define visibility as CAT I, CAT II or CAT III.   This can be done on the fly while the aircraft is flying.

The failures menu can be set-up to allow any number of single, multiple or cascading failures to occur either within a predefined time or at random.

ProSim737 Start-up Sequence

Ease of use and simplicity are important to ProSim737 and this mantra is carried through to the operation of the software.  Opening the ProSim737 Systems Module and other associated modules is exceptionally fast and the programs close with minimal lag time.  This is in stark contrast to other software suites which seem to take an eternity to open the various instances of the same program.

To simplify the start-up process when opening a flight session on my two networked computers, I’ve created shortcuts to the required ProSim737 modules and pasted them to the windows menu bar.  This is my start process (included are some add on programs I am running).

Server Computer

  1. Start PM Sounds

  2. Start ProSim737 main module

  3. Start ProSim737 MCP module

  4. Start ProSim737 Audio module

  5. Start FSX

  6. Start FSRAAS2

  7. Start Throttle Quadrant Phidgets

Client Computer

  1. Start PM Sounds

  2. Start ProSim737 Display (Captain PFD& ND)

  3. Start ProSim737 Display (First Officer PFD & ND)

  4. Start ProSim737 Display (EICAS)

  5. Start ProSim737 CDU

  6. Start ProSim737 Overhead Panel

  7. Start ProSim737 Audio module

  8. Start ProSim737 web-based instructor station

The time to start each program is no longer than 4 seconds; FSX takes the longest time to load.  Closure time is similar (mouse right click/close) from the menu bar.  To decrease closure times and mouse movement, a closure batch file can be created.

What is lacking & Possible Improvements

There will probably always be something lacking no matter what software you use, and some enthusiasts are never happy until they have everything – even if they never use or need it.  

The Aircraft Communications Addressing and Reporting System (ACARS) is not supported, although I believe this will be addressed in future updates.  I’ve already discussed some missing functionality with the CDU and touched on the inadequacy of the weather radar.

For the most part, all essential functionality is present within the system, although it would be nice to have more CDU functionality and a list of functions the CDU is capable of.  Currently no such list is available, and if using an official FMC guide it can be "hit & miss" working through he menus to see what is functional.

Several users have commented on the forum, that the %CG calculation in the CDU usually remains the same despite changing the aircraft's overall weight.  Users of TopCat pre-flight software have reported variances in %CG between ProSim737 and TopCat.  This variance may suggest an issue in the calculation of %CG which needs fine-tuning.

The list of hardware supported by ProSim737 is long and continuing to grow.  This said, I have noticed that the CP Flight ATC/Transponder unit which supports full TCAS operation is only partially functional within ProSim737.  TA/RA is inoperative.  Although the responsibility for this incompatibility probably rests with CP Flight, it would be very nice if ProSim737 attempted to rectify this.  CP Flight hardware is used universally and full functionality should be implemented across the complete CP Flight range of hardware.

Continual Development

In my opening paragraph I stated, “Avionics software is the heart of the simulator”.  Therefore, it’s pleasing to see continuing development of the software; updates that add or improve on existing functionality are released on a very regular basis.  Furthermore, the software designer is open to suggestions from users on how to enhance the software.  Shortcomings, when observed are quickly addressed.

One Aircraft - Mono Focus

One very important attribute of ProSim737 is that the developers only produce software for the B737 aircraft.  This means that they focus 100% of their time on replicating this airframe.  Other companies develop software for multiple aircraft and try to incorporate duel systems within their software.

Compromise & Expectations

It’s a fact that human beings rarely enjoy compromising – we want everything and we want it now. 

Some of you maybe "thinking" that ProSim737 has issues that need rectifying.  I'd be lying if I told you everything was 100% perfect - of course there are issues, but these are minor and differ depending upon your set-up.   But, in comparison to other software suites on the market, I feel confident stating that ProSim737 has less issues and rectifies niggling problems much more quickly than their counterparts.

If your expectation is to have software that is absolutely perfect without any glitches at all, then I'd strongly suggest that building a flight simulator is not really your calling. There are so many variables with computer equipment, drivers and the like that minor issues will pop up from time to time.

Developing software that replicates the B737 avionics to the tenth degree is a noble thought, as is maintaining a reasonable price.  However, what builders often fail to remember is that the Boeing software cost millions of dollars to design and implement with a solid team of developers.

ProSim737 delivers an exceptionally good package that is more advanced and feature-rich than its counterparts.  It’s not perfect, but the developers strive for perfection and improvements continually are being released on a regular basis.

Documentation and Support

The definition of osmosis is; “The gradual, often unconscious, adsorption of knowledge or ideas through continual exposure rather than deliberate learning”.  In the previous software suite I used, “osmosis” was very much the method of learning, as were mistakes, wasted time and frustration.

It’s good to see that ProSim737 includes a very detailed and well-written instruction manual which explains how to do nearly everything you need to know to configure the software to your set-up.  Failing this, there is a dedicated interactive forum that is very regularly reviewed both by users, beta testers and ProSim737 staff. 

If a problem does occur, support can be reached either by Private Messaging or e-mail.  

You will not be left “high and dry” by the developers.  They are very enthusiastic about their product and keen to help wherever possible.

A short video will guide you through the various menus of the ProSim737 Systems Module.

 
 

Recommendation & Overall Score

ProSim737 is a stable, well tested and tried software platform that provides most of the real-world avionics of a B737 jet-liner.  The software is easy to install, use, and does not require advanced computer knowledge to get you in the air.  Furthermore, a vast collection of hardware and interfacing cards are supported and new functionality is added on a regular basis.

At the time of writing, if you purchase ProSim737, the software includes full support and updates for an unlimited time period. 

This has been a long post, and if you have read this far, I hope you have gained some incite into ProSim737.

To download a free trail version of the software, visit their website – ProSim737.

My Rating is 9.5/10

Please note that this review is my opinion only and is not endorsed.

Update

on 2014-02-12 23:38 by FLAPS 2 APPROACH

  • Please note that since this review has been written, ProSim737 developers have released several updated versions of the software and three incarnations; Version 3 being the latest (2024).

  • The content of the review is outdated and has been left on the website for historical interest.

Which MIP - Half or Full

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Several companies fabricate 737 Next generation Main Instrument Panels (MIP) and each company offers different design options.  Basically, you have the following main options - some with and without instrument integration.

  • Full MIP with lower kickstand & CDU bay (Double Seat Training Device (DSTD)

  • Full MIP (desktop version) without lower kickstand & CDU bay

  • Half MIP with lower kickstand & CDU bay (Single Seat Training Device (SSTD)

  • Half MIP (desktop version) without lower kickstand & CDU bay

LEFT: A half MIP (SSTD).  Just because you don't have a DSTD doesn't mean you cannot have realism (photo courtesy FDS).

Which MIP is purchased depends on what level of realism is sought, your budget, your time, and your ability to fabricate lower kickstand sections (CDU bay, etc), and most importantly your available floor space.  Floor space is often a forgotten phase of your research.  Saying it will fit and 'she’ll be right mate' often 'doesn’t cut the mustard'.

My previous generic flight sim was very compact and was little larger than a desk.

Initially, I decided that a half MIP with lower kickstand and CDU bay would be ideal for my purpose; the new sim would fit perfectly into the alcove area that my current generic sim resides. 

Granted a half MIP is only a one seater and obviously wouldn't be an honest replication of a two seat aircraft, but the space savings are considerable – sometimes you need to compromise. 

Fly Engravity make an ideal half MIP, from which you can add to, as space and budget dictate.  However, the half MIP doesn’t come with full ICS (instrument integration) meaning you must wire it up yourself; for me, a somewhat daunting task in skill and time.

Flight Deck Solutions produces a half MIP with full ICS, lower kickstand and CDU bay.  But, at the time of writing this MIP is only a special order.  Therefore, if I was to have full ICS, I must purchase a full MIP with lower kickstand and CDU bay.

OEM 737-300 Throttle Quadrant

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oem 737-300 throttle quadrant in tear down yard

I was surprised to find an OEM throttle quadrant, at more or less the same time that I was about to purchase a reproduction throttle.

The throttle quadrant was used in a South West 737-300 series airframe and has a two-bay center pedestal.  The two-bay pedestal will suffice until a three-bay pedestal can be found.

The pedestal still has undamaged DZUS rails so it should be an easy matter to drop in avionics panels (radios, etc).

Proposed Conversion

The Throttle quadrant will be completely dismantled, cleaned and serviced.  Parts that are not required for simulation will be removed.  The lower section of the throttle and center pedestal will be removed as this is not necessary when installing the items to flat platform.

Any cards and other items needed to convert the throttle for flight simulator will be either mounted forward of the throttle on the forward bulkhead, or be hidden from sight in the center pedestal.  USB cabling will be routed along the lower side of the throttle to emerge from the forward bulkhead, and then will be connected to a computer.

The throttle will be converted using Phidget cards and servo motors.

Although the throttle is not going to be motorised (the thrust levers will not move automatically), the use a a DC motor will enable the trim wheels to rotate and the trim tab indicators to move.

Finally, a fresh coat of paint will be applied to the throttle and pedestal and any damaged transfers replaced.

oem 737-300 throttle quadrant in tear down yard

Original Equipment Manufacture (OEM)

A major advantage when using an OEM component such as a throttle is the added realism and immersion, not too mention that it's almost impossible to break an OEM throttle. 

One thing that I found interesting when searching for the throttle quadrant, was the number of throttles that are superficially damaged or are in poor condition.  Often the throttle and pedestal is scratched, dented and stained.  Investigating this further, I learnt that it's not so much the pilots that are doing this, but the dismantling crews.  Throttles are heavy and unwieldy and a dismantling crew has little time to worry about scratching a throttle that is probably going to scrap.

I have been fortunate in that the throttle and pedestal had been removed from the scrapped aircraft relatively carefully.

The pictures shown here were sent to me by the company who dismantled the aircraft.

Update

on 2020-07-14 23:24 by FLAPS 2 APPROACH

I've just received an e-mail from Florida stating the TQ has landed safely and in good order.  Next will be the transition from a scraped throttle quadrant to a working unit.  The timeline for the conversion is around 3-4 weeks.  If everything works out as anticipated, and freight is not delayed, I am expecting delivery to Australia sometime in early October.  Everything is green for go!  :)

Update

on 2020-07-14 23:27 by FLAPS 2 APPROACH

737-300 series throttle dismantled for cleaning.  You will immediately notice the massive internal cogs that control the internal mechanism; it makes a Swiss watch mechanism dim by comparison

After returning from a work trip to east Africa, I have been told that the throttle quadrant has been refurbished and wired to connect to flight simulator.  All that's remaining is to repaint it to Boeing grey.

Rather than repaint the actual throttle levers and knobs in white to replicate the colour scheme used by a Next Generation throttle, I have opted to leave the colour of the handles as they are.  The levers and knobs of the throttle (after cleaning) were in exceptionally good condition, and it seems a shame, almost criminal to repaint them.

Therefore, although the MIP is a simulation of a Next Generation airframe, the throttle quadrant will remain as a 300 series quadrant.  In many respects, simulation is about compromise, and to destroy an historical 300 series throttle to replicate a Next Generation throttle doesn't seem the right thing to do. 

Update

on 2020-07-14 23:32 by FLAPS 2 APPROACH

Not long now...   I spoke with my friend in Florida this morning and he informed me the throttle conversion has been completed. 

The throttle will soon be travelling as cargo to Australia either by United Airlines or Qantas for I hope a late October delivery.

Update

on 2011-10-16 07:10 by FLAPS 2 APPROACH

The throttle quadrant is finished and is finally in the air winging its way from the US to Australia.  After a stint in Australian Customs, it will then be send across Bass Straight and on to Hobart - its new home.  The next phase will then be the addition of avionic panels to the pedestal and connection and configuration to flight simulator.

Boeng 737 Trip Reminder Indicator

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OEM 737-800 Trip Indicator Reminder

Trip reminder indicators are an airline option that can be inserted to the upper portion of the yoke on both the Captain and First Officer side.  The indicator is a manual three digit memory device.

Initially used to remember the flight number of the flight, they were rarely used and eventually phased out of service. 

The pilot uses his thumb to move the three segmented dials to indicate the flight number.  I am told that when flight numbers began moving into 4 digits the devices were replaced with 4 digit indicators or their use discontinued.

I find the trip indicator very helpful and use it as a prompt to remember the landing speed (Vref).  After Vref has been calculated I scribe the speed into the trip indicator. 

The indicator is backlit from three 5 Volt incandescent bulbs, and it's a basic task to run a wire from the rear of the indicator through the yoke and column to a 5 volt power supply.  Other than a power wire, no other configuration needs to be done.

Although the trip reminder indicator is a very small addition, it's pieces of equipment such as this that provide increased immersion. 

Computers Ordered

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I'm not a fan on computers and I'm fortunate to know a few people who can guide me through the maze of computer hardware (thanks Nat & Boyd).

Two computers are required.  One computer will be the server and this will be networked with the second computer, the client.  The server will have flight simulator installed and other add-on software, while the client computer will be dedicated to the avionics software (Sim Avionics).  The client computer will have three video graphic cards installed to enable multiple monitors that Sim Avionics require

PC's are ordered and will shortly be assembled.

Update

on 2020-07-14 13:02 by FLAPS 2 APPROACH

The computers have arrived.  WOW, these brutes look powerful and impressive.  I'll be installing flight simulator and networking them over the weekend.  Hopefully, the MIP from Flight Deck Solutions and control column from ACE Engineering will arrive soon.

Research & Development Completed - MIP & Yoke Ordered

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R&D mode has taken considerable time with the last two weeks being almost full time.  It takes time to double check everything, scour the Internet, and wait for e-mail replies from various manufacturers.

Starting

Every project must start somewhere and I wanted to use as many OEM components in the build as possible, however, procuring components takes considerable time and I was keen to begin.  Therefore, rather than wait until everything was found, a decision was made to begin the project with a number of reproduction items.  This at least would get the project started, and as OEM components were obtained these would replace reproductions.  It would also enable me to fly the simulator more or less from the beginning of the project.

I researched a number of companies to supply the Main Instrument Panel (MIP) and two companies stood out from the rest, Flight Deck Solutions (FDS) and Fly Engravity. 

Flight Deck Solutions was chosen mainly because of support availability in Melbourne Australia, and a more reasonable Australian to Canadian monetary exchange rate.  Fly Engravity were a very close second, however the Euro is very strong and freight so expensive from Europe, that using this company became financially prohibitive.

In addition to the Main Instrument Panel, FDS will also supply some of the avionics and the avionics software (Sim Avionics). 

ACE Engineering (another Canadian company) will be supplying the reproduction 737 yoke and control column. 

I already am in possession of a the Mode Control Panel (MCP) and EFIS, both manufactured by CP Flight in Italy.  These will eventually be replaced by a more upmarket MCP and EFIS.

I've been told that delivery of the yoke and MIP will be late September (2011).

Now that the main part of the simulator has been ordered, I can begin to widen my search for additional component..

Presently, I'm talking with an individual who has a OEM Boeing 737 throttle for sale.  If negotiations are successful, I hope to purchase this quadrant. 

Update

on 2011-12-01 02:22 by FLAPS 2 APPROACH

Its taken some time, since my August order, to receive notification that the MIP I have ordered from Flight Deck Solutions is "almost" ready.  I've been told it will ship late this week so it should be in Australia by December 22 (2011).  Once the MIP has arrived, it will allow me to begin to develop the simulator.

Update

on 2011-12-07 11:25 by FLAPS 2 APPROACH

At last I've been told that the MIP I ordered from Flight Deck Solutions (FDS) in Canada has been completed.  The MIP is currently on the way to Australia via DHL air cargo.  It's been a long wait and I hope the product has been worth the lengthy waiting time.

Welcome - First Post from Flaps 2 Approach

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This is the first post on Flaps 2 Approach

This website will document the building of a working Boeing 737 simulator.  This is an exciting multifaceted project that will take considerable time to complete.  I'll have to learn skills in a number of fields that, and brush up on old skills not used for sometime.  I expect I'll be phoning knowledgeable friends and asking LOTS of questions....

Also I am not a website designer or developer, so I have a lot to learn in this area as well.

The website, in addition to documenting the progress of the build, will also act as a conduit to:

  • Discuss aviation-minding subjected pertinent to the Boeing 737;

  • Discuss operational and other flight procedures used in the 737 aircraft; and,

  • Provide reviews on hardware and software pertinent to flight simulation (in particular to the 737 aircraft).

Website Name

I thought carefully about a name for the website.  Initially the usual names came to mind - 'My 737 Site' and similar.  I wanted something distinctly aviation and something that related to all aircraft.  Flaps to approach seemed the logical choice as nearly every aircraft has to set flaps to approach.  I used the numeral 2 instead of the word to enable the name to be more easily entered into a browser, and also to differentiate between setting the 'flaps to approach' and the website name.

So let's get the ball rolling..... 

- Chocks Away - or should it be 'Prepare For Landing - Flaps 2 Approach'

- Chocks Away - or should it be 'Prepare For Landing - Flaps 2 Approach'