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Mission Statement 

The purpose of FLAPS-2-APPROACH is two-fold:  To document the construction of a Boeing 737 flight simulator, and to act as a platform to share aviation-related articles pertaining to the Boeing 737; thereby, providing a source of inspiration and reference to like-minded individuals.

I am not a professional journalist.  Writing for a cross section of readers from differing cultures and languages with varying degrees of technical ability, can at times be challenging. I hope there are not too many spelling and grammatical mistakes.


Note:   I have NO affiliation with ANY manufacturer or reseller.  All reviews and content are 'frank and fearless' - I tell it as I see it.  Do not complain if you do not like what you read.

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


All funds are used to offset the cost of server and website hosting (Thank You...)

No advertising on this website - EVER!


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

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Sim Avionics Flight Software - Review

I've heard it said that a "simulated flight deck is as good as the software behind the scenes" and I agree with this comment: a flight deck with poor software is a hive for frustration, disappointment and time wastage.

It's easy to write about the features and functionality of Sim-A as they are plentiful; but, I don't want to become too bogged down in minute detail, otherwise I’d be writing a manual.  This review will not address in detail everything that Sim Avionics (Sim-A) software can or cannot do; if your interested in a full functionality list, it’s best to check their website, as functions are altered and improved upon on a regular basis. 

Before continuing, it should be noted that 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 with 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. 

Sim Avionics is a complete avionics solution providing the avionics software needed to build a fully functioning home cockpit; no other software is required.  It has been designed to run on multiple PC's in various configurations interfacing with FS2004 (FS9) or FSX via FSUIPC and Wide Client.

Relative Newcomer

Although a newcomer to Sim-A and still learning some of the more advanced features of the software, I thought it pertinent that I make an "introductory review".


Reliability is the most important aspect of any software.  To date, Sim-A has performed as one would expect from any high-end payware software. Overall, the software is reliable, performs well, and appears to be a robust and stable platform with consistent responses.

Certainly, it seems much more stable than some of the competitors on the market (if comments on flight simulation forums are anything to go by) and is far easier to use than some other well known brands.  But, it must be remembered that the software is only as good as the information inputted; therefore, if you try and do things that the aircraft & software is not designed to do, expect problems.

Further, you must bear in mind that no one computer (PC) is the same as another.  Different drivers, software, flight models and hardware configuration can cause any software to behave erratically from time to time.

This said, Sim-A can on occasion produce spurious results.  This is mainly associated with the more advanced auto pilot functionality and user operator errors!  

I’ve documented the issues and fixes, including some user operator errors, that troubled my installation below.

Issue 1 - Trim Tab Dancing

Now and again the trim tab will become unstable as the auto pilot continually recalculates the required pitch for the aircraft at the current speed.   The trim tab will “dance” causing the aircraft to pitch up and down. The trim dance (as I call it) occurs only on flights that have weather depicted, and it doesn’t occur on every flight.

FSUPIC to the Rescue

Although a little disconcerting, I believe the cause is not so much Sim-A, but the way the weather, especially aloft winds, are generated causing the elevator to continually move to counter weather differences.  There is a tab within FSUPIC that stops the elevator trim from operating when the aircraft is in auto pilot mode.  Since checking this FSUPIC setting (placing a tick in the box), the trim dance I was observing has decreased markedly and is now nonexistent.

Information for the auto pilot is located within the aircraft's configuration file.  If auto pilot trim issues persist then some minor tweaking of the numbers maybe required.  If this happens to you, then be rest assured that FDS and Sim-A staff will assist you with any minor tweaking to get you flying.

I’ve discovered that if the auto pilot does not provide consistent outputs (such as trim dancing), an easy method to often solve the issue is to switch the auto pilot command button off and then back on. 

Issue 2 - V-Nav Inconsistency

Replicating the more advanced B737 auto pilot functions requires complicated algorithms.  This is especially so with vertical navigation (V-Nav).  

Sim-A handles V-Nav reasonably well, although you have to keep an eye on what V-Nav is doing, espeially when transitioning from level flight to descent and approach.  On some flights, V-Nav honours the speed and altitude restrictions and transitioning the STAR to approach is accurate.  However, at other times restrictions are not followed and the aircraft will overshoot the height and speed restriction.

V-Nav always operates correctly on take-off utilizing a Standard Instrument Departure (SID).

There is no particular reason for this - it just happens from time to time.

Understanding V-Nav and what its doing can be challenging

The challenge, I have discovered when using V-Nav is two-fold.  First and foremost, you must use it within the designed capabilities of the program, and second, 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 overfly of the entered restrictions.  This is not the fault of Sim-A.  It's user error

Sim-A, in my opinion is not alone with minor V-Nav issues; Project Magenta, Pro Sim 737 and others also have difficulties replicating this complicated algorithm. Indeed, real pilots are often confused understanding how V Nav operates and why it's doing whatever it's doing! 

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 believe to be correct, then turn it off and use the more reliable L-Nav, Level Change or Vertical Speed functions.

Issue 3 - Display Lag and Staggering

There is minimal display lag running Sim-A and FSX (using two computers). 

The gauge movement of the displays is fluid and there is no pausing as information is shuttled to and from the computer and Sim-A.  However, if “all waypoints” is selected to be displayed on the ND, then staggering becomes obvious on the Main Flight Display’s altitude tape, as the aircraft ascends or descends in altitude. 

I’ve been told by long-term Sim-A users that this is normal as the information required to display and update the “all waypoints” is very comprehensive and can easily generate an “information bottleneck”.  The solution is easy – turn off “all waypoints” when climbing, descending, or on approach.  Honestly, I rarely have "all waypoints" selected and only use this function if I am searching for the nearest waypoint to make an alteration to the flight plan.

I have not experienced any display lag or staggering issues with other EFIS functions. 

Issue 4 - Software Server.exe Lock-up

When you read this title, I can image the thoughts going through your mind.  But, this is one of those negative aspects that has a very positive twist. 

Although the software has never crashed to desktop, it has on occasion “locked up” requiring a reboot of the Sim-A server.exe.  The lock up usually occurs when I have been repeatedly doing something incorrectly, such as keying into the CDU  incorrect information, therefore; the lock-up caused by user error

If this issue should occur (for whatever reason), it's only a matter of closing the server.exe using the shutdown command tab and then reopening the server.exe window.  You do not need to close down Sim-A or FSX. 

This brings me to the positive twist I mentioned in the earlier paragraph.

Outstanding Sim-A Feature

Of the many features Sim-A has, the ability to historically re-set the software without loosing your flight details or actual flight (in real time) is probably one of the more beneficial. 

If a problem should transpire during a flight causing the server.exe display to freeze or something to stop working, you can re-set the software by closing the server.exe display and reopening it.  The interruption to your flight will be seamless, providing you depress the tab “last state” within ten seconds of reopening the server.exe display window.

This is but one of several "smart" features that are often overlooked.

Functionality Controlled by Control Panel

Sim-A’s central access point is the control window (server.exe) which is always visible on your “flight configuration” monitor. 

The server.exe display window is the core of the program and shows the current “avionics” status of your aircraft (EFIS settings, weather, terrain, TCAS settings, aircraft details, engine, hardware settings, etc).  The display also provides a handy central area in which you can tweak the aircraft’s .cfg file, FSUPIC settings, offsets and so forth.   For more detail on this comprehensive display I direct you to the Sim-A website.

LEFT:  This is screenshot of the main Sim-A interface (server.exe / control window).  From this screen you can control all of the Sim Avionics variables.  It does look complicated and there is a lot of information on the screen; however, it took me less than 30 minutes to get a rough idea what was happening and get into the air.  Menu tabs open up further screens and all settings are automatically saved on a regular basis. 


Sim Avionics Features

At the minimum Sim-A will supply you with:

  • Captain and First Officer Pilot Flight Display (PFD) and Navigation Display (ND)
  • EICAS Display (upper & lower) with fully integrated EICAS messaging
  • Virtual Main Control Panel (MCP)
  • Virtual EFIS Display (two)
  • Virtual overhead panel
  • Virtual CDU Display
  • Multiple CDU Support
  • Support for Hardware MCP & EFIS
  • Complex Auto Pilot Functionality (SINGLE CH, LAND 3)
  • Sound module
  • EGPWS and TCAS
  • B737 system logic
  • Radar (weather) & Terrain overlay displays
  • Virtual stand-by instruments (vast selection)
  • Fuel & scenario loading platform (dispatcher console)

Other functionality, such as instructor station, and observer CDU is available depending upon which license type you purchase.

To see screen grabs of the display functionality of Sim-A (PFD, ND, radar, etc), navigate to the PFD page on the Sim-A website

Of course, if you are operating a full flight deck with the appropriately supported hardware you will not require the virtual MCP, EFIS, CDU and overhead displays.

Support for Add On Hardware, Flight Models & Software Cloning

Speaking of hardware, SIM-A supports many of the popular hardwired instruments available on the market.  For instance, the CP Flight MCP and EFIS units are, with some minor .cfg  file alterations plug & fly.  Similarly, GoFlight and Flight Illusion products are easily configured for Sim-A use.

Currently SIM-A supports the B737 and the B777.  Several B737 and B777 aircraft configuration files (FS9 & FSX versions) are available within the software: default model, PMDG, Posky, Wilco, XPlane and Meljet.

Another feature of Sim-A is the ability to run certain aspects of the software from different computers.  For example, you can clone the sound module to run on different computers, thereby, playing aircraft sounds through one set of speakers, and ATC commands through another set of speakers (or headset).

CDU - Background Software

No review of Sim Avionics would be complete without a short segment on the CDU.

Sim-A 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. 

Most pages associated with a commercial CDU are modeled and updates continue to add new features and improve on existing functions.  Some of the basic features that are modeled by the software are:

  • Indent page on start-up (weights, fuel, cost index, etc)
  • Approach reference page with VREF selection
  • Route, LEGS, Arrival, Departures & Holding pages (user controlled including approaches, STARS & transitions)
  • Progress pages (fuel, distance to go, ETA, wind, crosswind component, cross track error, fuel prediction etc)
  • Cabin calls
  • METAR (real time)
  • V-Nav & L-Nav compliant (climb, cruise and descent)
  • GPWS overrides
  • NAV radio page (ADF, VOR & ILS data)
  • Captain EFIS control
  • SIM control page (separate commands to control SIM instead of using keyboard)

To see screen grabs showing the various features available, navigate to the CDU page on the Sim-A website

Further Functionality

I/O Interfacing and FSUPIC is fully supported as are FSUPIC offsets, and if your using an FDS MIP, a program called InterfaceIT provides an interface for connection of switches, lights and other modules to Sim-A. 


A manual is supplied with the software and there are several documents (within the documentation section of the main Sim Avionics folder) that assist in the correct set up procedure. It is VITAL that you read all the documentation BEFORE installation. 

To read the Sim-A installation & operations manual, navigate to the Training Section.

For a more in-depth look at how the autopilot functions, see this document in the Training Section Autopilot Functional Examples - Sim Avionics.  This document provides an excellent review of MCP procedures in relation to take off, descent and landing (ILS & LAND 3).

Software Installation

Installation is uncomplicated.  However, there are a number of changes you need to make to several files to ensure correct operation.   Additionally, if you’re using two computers then basic networking knowledge is required, as are the programs Wide Client FS and a registered copy of FSUPIC.

Determining the correct location for the various avionics displays on the computer monitors (within the MIP) is straightforward, although fine-tuning the location on the monitor can take a little time.  Basically, you alter the length and width of the various displays within the config files.  Once you know how this is done, it's just a matter of altering the line numbers until your satisfied with the result.

When Sim-A is set-up correctly, everything is relatively painless and obvious - more or less “following your nose”.

Running a flight deck isn’t pressing a button and “presto” there it is… 

For the avionics suite to operate correctly, several programs or clones of the program must be loaded.  At the minimum this is: Captain's PFD and ND, First Officer's PFD and ND, CDU, EICAS, Server.exe, Tcp Client, InterfaceIT, Wide FS and Sound.  Depending upon your requirements and set-up, the MCP, Overhead, First Officer's CDU and the Dispatcher console may also need loading.  The window displays are opened by clicking the .exe shortcut files that the program installed to your desktop.

To minimise the time in loading and to be user friendly, a handy program has been included with Sim-A, hidden within the documentation folder; it is a start-up batch file. This program allows to you start all the functions and displays with the click of one button.

I've compiled a short video showing how the program automatically opens and loads the software using the batch file.  In my set-up, Sim-A is installed and operates from my second computer (client). 

Double click to open and close full screen viewing.

Video showing operation of batch file.

Video showing the various functionality available via the main display server.exe window.

Ownership and Support

Sim Avionics is the preferred avionics suite of Flight Deck Solutions.  If you purchase an integrated MIP from FDS, Sim-A is the flight software that will be supplied. 

Support for Sim-A is provided by the software’s main engineer and FDS staff.  Help can be obtained either via the active support forum (on the FDS website) or via e-mail.

Continual Development & Financial Investment

Sim Avionics is not an inexpensive investment, however, it’s pleasing to see continued development of the software; updates that add or improve on existing functionality are released on a regular basis.  Furthermore, the software designer is open to suggestions from users on how to enhance the software.

At the time of writing, if you purchase Sim Avionics through Flight Deck Solutions then the price of the software includes full support and updates for an unlimited time period. 

Recommendation & Overall Score

Sim Avionics 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 and use, however, advanced knowledge is required to use some of the advanced features such as FSUPIC offsets and the like.  All avionics software has issues from time to time, and Sim-A is no different, but the ongoing development of this software and a solid support structure can only be seen as positive.

To investigate Sim Avionics more closely, visit their website - Sim Avionics Website.

My Rating is 8.9/10

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

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Reader Comments (2)

Really enjoying your blog with 737 build.
> I too am building a 737 sim and use SA as the driving software. I just
> saw your review on SA  and agree with it.  
> I've been using SA for a year now and I must say have not really enjoyed the
> experience . Because;
> 1. Lnav tracking is not realistic  at times...when over flying a waypoint,
> going direct to a waypoint and doing a course intercept for inbound approach
> etc  ( Mark has just released a beta that improves it though, but still needs
> work)
> 2. vnav...takeoff is a lot better now, I think the aircraft model with MCP is
> also much more stable...the pitching issues I was having were caused by a
> fsuipc setting.  (logging) just make sure boxes are not ticked!  
> 3. FMC...both Lnav and Vnav need a lot of work! If you load a flight plan with
> SID/Enroute Waypoints/STAR/APP and look at LEGs Page on CDU the waypoints for
> flight can be totally out of order etc....vnav Altitude s and Speeds are
> mostly wrong also, and because of this FMC has a hard time caluc correct Fuel
> estm.  
> 4. SA does not have a stand alone flight model.... So if you use FSX, you have
> to use  the default  FSX 737 which is Shit (sorry) or try and come up with a
> make shift work.
> Well ,because of all these reasons I decided to look at Prosim737 about a month
> ago.
> 99% of items 1-4 are correct with Prosim737. FMC is by far better! Sure ,not
> as many SA features (like metar etc) but all the stuff that needs to work  
> correctly does:-) ( Lnav ,vnav, holding,fuel caluc....etc) There are updates
> constantly which fix and add new features. Prosim only has 737 software so all there work goes into that , not like SA which has 737,777, and maybe more in works?
> Prosim737 flight model is great also....works correctly straight of the bat.
> And prosimi737 is a fraction of the cost of SA at $300 Euros. I spent $1700
> on SA .
> I think mark needs to work on really getting these issues solved or  he will
> find more and more people jumping ship to Prosim737 etc Maybe forget about other aircraft software (777,747 ) and fix the basic errors in SA first then build on that.


April 15, 2012 | Unregistered CommenterSim builder 737

Hello; Thank you for your comments. I am sorry to hear your experience with Sim Avionics has not been the best. You appear to be having more problems than V-NAV issues. Hopefully, the problems you are having will be sorted in their next upgrade release.

Thanks again for your feedback. Luck to you, Iain

April 15, 2012 | Registered CommenterFLAPS 2 APPROACH
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