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Mission Statement 

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

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


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

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


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

Journal Archive (Newest First)

Entries in Video (4)


CDU by Flight Deck Solutions - Review

The Control Display Unit (CDU) is the pilot interface to the Flight Management Computer (FMC).  The FMC integrates with the Flight Management System (FMS) of the aircraft.  The FMS contains the navigational database.

LEFT:  Pro Mx CDU by Flight Deck Solutions.  Click to enlarge.

Historical Context 

The first true FMC was introduced in 1984 with the release of the Boeing 737-300.  In its most basic description, the FMC can be described as a computer that can store flight and navigation data and perform detailed and comprehensive assessments of the stored data, providing the pilot with up date information that is relative to safe and accurate flight.

Flight Management Computer (FMC) & Control Display Unit (CDU)

The CDU interface enables the flight crew to interact with the FMC and FMS to access, amougst other things: the navigational database, autopilot, flight director, auto-throttle and internal reference system (IRS).

An aircraft will only have one CDU installed, however, dependent upon company regulations, air safety and routing (flying over water), many operators will have two CDU units installed for redundancy and independent use by the Captain and First Officer.  Think of the CDU as a keyboard to the FMC which in turn is a component of the FMS.

This said, the acronyms CDU and FMC are often used interchangeable in aviation parlance.

Flight Management System (FMS)

The FMS is an integrated system of which the FMC and CDU is just one component.  The FMS is capable of four dimensional area navigation (latitude, longitude, altitude & time) while optimizing performance to achieve the most economical flight possible.  

The FMS stores the navigation database and route information which the autopilot will fly when in LNAV mode. When given data such as YMHB & KSEA, it takes inputs from the fuel summation unit to give a gross weight and best speeds for take off, climb, cruise, descent, holding, approach, etc. These speeds can all be flown directly by the autopilot & auto-throttle in VNAV mode.

Flight Deck Solution's PRO Mx CDU

The CDU manufactured by Flight Deck Solutions (FDS) is an outstanding piece of simulation engineering.  The unit is well built, solid, and replicates a real B737 style CDU 1:1.

The CDU body and bezel (front plate) is manufactured from high grade metal while the rear section that houses the electronics is plastic.  A USB and VGA cable connects to the video card output on the computer. The connections to the cable are located on the rear of the unit allowing easy connectivity to the computer.  The CDU has been painted in the correct Boeing grey colour and the paint has been applied professionally in several thin layers; the paint does not chip or wear off with use.  Importantly, for those using genuine aviation parts, the unit is DZUS complaint and drops into the rails in the CDU bay with perfect precision.  FDS includes four DZUS fasteners to allow connection to the rails.

High Fidelity Dimable Keyboard

The keyboard used in the CDU is made from high definition injection-molded plastic and the keys are dimpled and back-lit.  The keys are very tactile and when depressed an audible click is heard ensuring you know the key has been depressed.  

For night operations, the unit has a knob that can be rotated to dim the back-lighting brightness level of the keys.  A functional metal carry bracket, that folds out from the edge of the bezel is also included.  This replicates the carry handle on the real CDU.

Functionality - Software (Sim Avionics & ProSim737)

It is important to understand that the functionality of the CDU is not generated by software that comes bundled with the unit, but by the avionics suite you have chosen to use.  Therefore, I have chosen not to discuss the various options that each software suite may or may not replicate.  In the real world, airline companies have the opportunity to purchase specific options they believe are relevant to their flight operations.  This said, many of the variations have been replicated in both software suites.

I have used the CDU with Sim Avionics and ProSim737; both software suites provide excellent functionality and work flawlessly with the unit.

The CDU is used throughout a flight; therefore, reliability is expected.  The solid construction of the FDS CDU has not let me down and after endless pressing on keys they still function as you would expect them to. 

Navigation Database

The unit does not ship with navigation data included.  The navigational database which includes STARS and SIDS, Runways, airports must be purchased separately from Navigraph and then installed into your avionics software suite.  Download and installation of the database is very easy and most of the installation is automated.

LEFT:  The CDU at night showing only illumination from the unit.  The backlighting is adjustable and able to be dimmed by turning the dim knob on the unit.

WOW Factor

The best feature of the CDU I have left to last – the display.  'WOW' is the only word to describe the display.

The display is a colour VGA display unit sporting 800 x 600 resolution.  What this means is that the script on the display is VERY clean, VERY readable and VERY sharp.  Being a colour display means that differing colours (white, green and magenta) can be used for the fonts that your avionics software generates.  The use of colour helps distinguish between functions that are activated or in stand-by mode, not to mention enhancing the units display readability.

The display is equally distinguishable in full daylight and in darkness and does not exhibit screen cut off when viewed at an angle (as some laptop screens are prone).

CDU Set-Up

Setting up the CDU using Sim Avionics was relatively painless.  You must designate which CDU you are installing (Captain, First Officer or Instructor), edit a few lines in the .ini file to ensure it recognises the correct CDU, and configure the display location.  The only teething issue I had was ensuring that the monitor display window size was correctly positioned on the screen for the location of the CDU.  It took quite a few attempts to get the position 'just right'.

The set-up with ProSim737 is equally straightforward, however, to ensure correct operation you must install and enable additional software supplied by ProSim737.  Installing and initiating the software is relatively straightforward, however, it's important to follow the provided instructions to ensure trouble free operation.

Manual and Tuition

A manual explaining the functions of the CDU and/or tutorial is not included.  In my opinion, FDS should develop a video tutorial that runs you through the basic functions of the unit including a simulated flight.  This said, there are several dozen excellent tutorials that can be found on U-Tube that provide basic and advanced CDU use.  If you navigate to the video section on this website, you will find a number of CDU training videos.  FDS do include a basic manual explaining the installation and set-up procedure.

The FMC Guide written and sold by Bill Bulfer is strongly recommended as this guide provides basic and advanced tuition in how to use the CDU.  A review of the FMC Guide can be read here.

I cannot fault the CDU unit manufactured by Flight Deck Solutions and believe it to arguably be the best piece of reproduction hardware currently available.

My Rating 10/10

Please note that this review is not endorsed by Flight Deck Solutions (FDS) or by any other reseller.

A short video depicting some of the more commonly used keystrokes of the Flight Deck Solutions CDU.  No particular key sequence has been followed. The video is to demonstrate the screen resolution and the uptake speed after depressing a key.  Double click video to view full screen.  Note that this video was produced using Sim Avionics software suite.  ProSim737 software provides slightly different options.


Video - Weber Pilot Seat Adjustment Capabilities

A short video clip to follow up on the installation of two B737 Weber pilot seats (Captain and First Officer) that have been installed into the simulator. The seats were retrieved from a South West B737 that was destined for the wrecking yard. This video demonstrates the range of movements that the seats are capable of.  Double click video to vuew full screen.

To read addtional information on the seats, see these other Journal entries.

Weber Pilot Seat Adjustments from Anaspides Photography on Vimeo.



Video - Operational Trim Wheels & Indicators

Now that the throttle quadrant is operational, USB hubs working and the Phidgets correctly configured, I thought I’d post a short video clip showing the trim wheel operation.  The wheel spin is controlled by inputs either from the auto pilot or from electric trim switches located on the yoke.  When the wheels spin, there is corresponding movement of the trim wheel indicator tabs; the indicators, which are coloured white show the pitch of the aircraft.

Currently, the trim wheels spin at only one speed (mono-speed adjustable in the Phidget settings).  Later on, when I have time I'll be altering the speed to variable-speed  This will allow the wheels to spin at differing speeds dependent upon whether the aircraft is being controlled manually or by the autopilot.  This configuration requires some extra time with Phidgets and is not essential at the present time.

The trim wheels are connected to a 12 volt DC servo motor.  The motor is mounted inside the throttle quadrant near the actual wheels. To control the power to the servo motor I have used a Phidget advanced servo motor controller.  Double click video to view full screen.

Boeing 737-300 Trim Wheels Spinning 


Safety First

The trim wheels have a white line painted on them for a very good reason (not invasion markings for D-Day 1944).  The spinning wheels are dangerous – keep your fingers well away when they are operational!  The white line, when spinning acts as a visual warning to pilots that the wheels are spinning.  It also provides a means with which to calibrate the rotation speed of the trim wheels.  Each wheel also has a pull out handle that can be used to control trim manually.  Like your fingers, if your knee is in front of the handle when the wheels spin expect a solid whack on your knee cap.  I’ve been told by a real world B737 Captain, that there have been several occasions when pilots have suffered injuries to knee caps from being whacked by spinning wheels, after inadvertently leaving the handle extended.  As for me, well when they first "spun" into action the cup of coffee that was resting slightly against the wheel spun across the floor  :)

Stab Trim Switch Cut Out

As you can image, spinning trim wheels can be slightly annoying and very noisy – especially if you’re flying at night and others in the house are attempting to sleep.  Therefore, to stop the trim wheels spinning, I have programmed the trim stabilizer (stab trim) switches on the throttle quadrant to cut the power to the servo motor.  Push the stab trim switches to normal and the wheel spin; push the switch down and spinning stops.  Although the spinning stops, the trim indicator tabs still move.

In a real B737 this switch is used to stop run away trim wheels, so there is a certain amount of authenticity connecting this functionality to this switch.

Trim Tabs – Why Are They Important?

The use of trim tabs (elevator & pitch) significantly reduces pilots' workload during continuous  flight maneuvers (sustained climb to altitude after takeoff or descent prior to landing), allowing them to focus their attention on other tasks such as traffic avoidance or communication with ATC.

Trim affects the small trimming part of the elevator on jet airliners. Trim (controlled by the trim switch on the yoke) is used all the time after the flying pilot has disabled the autopilot, especially after each time the flaps are lowered or at every change in the airspeed, at the descent, approach and final.   Trim is most used for controlling the attitude at cruising by the autopilot.

Correct trim frees the pilot from exerting constant pressure on the pitch controls for a given airspeed / weight distribution. Typically, when the trim control is rotated forward, the nose is held down; conversely, if the trim wheel is moved back, the tail becomes "heavy" and the nose is held high.

Trim Tabs - Technical Hype (the basics)

When a trim tab is employed, it is moved into the slipstream opposite to the control surface's desired deflection. For example, in order to trim an elevator to hold the nose down, the elevator's trim tab will actually rise up into the slipstream. The increased pressure on top of the trim tab surface caused by raising it will then deflect the entire elevator slab down slightly, causing the tail to rise and the aircraft's nose to move down.  In the case of an aircraft where the deployment of flaps would significantly alter the longitudinal trim, a supplementary trim tab is arranged to simultaneously deploy with the flaps so that pitch attitude is not markedly changed.


Video Training Clip - SAS 737 Series - Review

This is a short exerp from a SAS flight video. The video takes you through several domestic flights with the two pilots explaining the proceedures they are doing during the flight.   I found the excerpt  interesting, so thought I'd post it.  The DVD is available for purchase.  I have ordered the two DVD set and will post a review once I have watched it.