E-mail Subscription

Enter your email address:

Delivered by FeedBurner

Syndicate RSS

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!


Find more about Weather in Hobart, AU
Click for weather forecast






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

Journal Archive (Newest First)

Entries in B737 NG Throttle (2)


B737 Throttle Quadrant - Speedbrake Conversion and Use


The speedbrake serves three purposes: to slow the aircraft in flight (by incurring drag), to slow the aircraft immediately upon landing, and to assist in the stopping of the aircraft during a Rejected Takeoff (RTO).  

There are four speedbrake settings: Down (detent), Armed, Flight Detent and Up. 

In addition, there are three speedbrake condition annunciators (lights), located on the Main Instrument Panel (MIP), that annunciate speedbrake protocol.  They are: Speedbrake Armed, Speedbrakes Do Not Arm and Speedbrakes Extended.  These annunciators (lights) illuminate when certain operating conditions are triggered.

This post is rather long as I've attempted to cover quite a bit of ground.  The first part of the post relates to technical aspects while the second portion deals with conversion.  Hopefully, the video at the end of this post will help to clarify what I have written.

Technical Information

Speedbrakes consist of flight spoilers and ground spoilers. The speedbrake lever controls a 'spoiler mixer', which positions the flight spoiler power control unit (PCU) and a ground spoiler control valve.   The surfaces are actuated by hydraulic power supplied to the power control units or to actuators on each surface.

Ground spoilers operate only on the ground, due to a ground spoiler shutoff valve which remains closed until the main gear strut compresses on touchdown (this is activated by the squat switch).

In Flight Operation

Actuation of the speedbrake lever causes all flight spoiler panels to rise symmetrically to act as speedbrakes.  The lever can be raised partly or fully to the UP position.  This causes the extension of the flight spoilers to the equivelent full up (ground spoiler) position.

Ground Operation

All flight and ground spoilers automatically rise to full extension on landing, if the speedbrake lever is in the ARMED position and both throttle thrust levers are in IDLE. When spin-up occurs on any two main wheels, the speedbrake lever moves to the UP position, and the spoilers extend.

When the right main landing gear shock strut is compressed, a mechanical linkage opens a hydraulic valve to extend the ground spoilers.  If a wheel spin-up signal is not detected, the speed brake lever moves to the UP position, and all spoiler panels deploy automatically after the ground safety sensor engages in the ground mode.

After touchdown, all spoiler panels retract automatically if either throttle thrust lever is advanced. The speedbrake lever will move to the DOWN detent.

All spoiler panels will extend automatically if take-off is rejected (RTO) and either reverse thrust lever is positioned for reverse thrust. Wheel speed must be above 80 knots in order for the automatic extension of the spoilers to take place.

A failure in the automatic functions of the speedbrakes is indicated by the illumination of the SPEEDBRAKE DO NOT ARM Light. In the event the automatic system is inoperative, the speed brake lever must be selected manually placed in the UP position after landing by the pilot not flying.

Speedbrake Lever Movement

The logic relating to the position of the speedbrake lever is:

DOWN (detent)

  • All flight and ground spoiler panels are in the closed position.


  • Automatic speedbrake system armed.
  • Upon touchdown and activation of the squat switch, the speedbrake lever moves to the UP position and all flight and ground spoilers are deployed.


  • All flight spoilers are extended to their maximum position for inflight use.


  • All flight and ground spoilers are extended to their maximum position for ground use.

Illumination of Speedbrake Condition Annunciators (lights)

The logic relating to the illumination of the annunciator condition lights is:

Speedbrake Armed Annunciator

  • The light will not illuminate when the speedbrake lever is in the DOWN position.
  • The light illuminates green when the speedbrake is armed with valid automatic system inputs.

Speedbrake Do Not Arm Annunciator

  • The light will not illuminate when the speedbrake lever is in the DOWN position.
  • The light indicates AMBER if there is a problem (abnormal condition).
  • The light will illuminate during the landing roll following through 64 KIAS provided the speedbrake lever has not been stowed.  The light will extinguish when the aircraft stops or when the speedbrake lever is stowed.

Speedbrakes Extended Light

  • The annunciator illuminates AMBER pursuant to the following conditions.

In Flight

  • Amber light illuminates if speedbrake lever is positioned beyond the ARMED position, and
  • TE flaps are extended more than flaps 10, or
  • Aircraft has a radio altitude (RA) of less than 800 feet .

On The Ground

  • Amber light if the speedbrake is in the DOWN (detent) position.
  • Amber light if the ground spoilers are not stowed.

It is important to remember that the speedbrakes extended annunciator will not illuminate when the hydraulic systems A pressure is less than 750 psi.

Simulator Operation - What Works

Note that the following has since been replaced with more reliable system.

Throttle Quadrant Rebuild - Speedbrake Motor and Clutch Assembly Replacement.

  1. Rejected Take Off (RTO) after 80 knots called - Activation of either reverse thrust lever and throttle to idle will extend spoilers (if RTO armed).  Lever moves to UP position on throttle quadrant.
  2. Spoilers extend on landing when squat switch activated, throttles are at idle and lever is in armed position (3 requirements).  Lever moves to UP position on throttle quadrant automatically
  3. Spoilers extend automatically when reverse thrust is applied (if not previously armed - see above)
  4. Engaging thrust after landing automatically closes spoilers.  Lever moves to DOWN position on throttle quadrant.
  5. Speedbrakes extend incrementally in air dependent upon lever position (flight detent).

Speedbrake Logic - Alpha Quadrant Card and Closed System

The logic for the speedbrake, which is identical to the real B737 aircraft, is “hardwired” into the Alpha Quadrant card which is located in the Interface Master Module (IMM) and connected to the throttle quadrant by a custom wired VGA cable.  Programming the Alpha Quadrant card is by stand-alone software.

The speedbrake system is a closed system, meaning it does not require any interaction with the avionics suite software (ProSim737); however, the illumination of the condition lights does require configuration within the avionics suite as they are not part of the closed system (a future update will include all annunciators within the system). 


A common method to convert the speedbrake is to use a potentiometer and then calibrate using FSUIPC ( Flight Simulator Universal Inter-Process Communication).   Whilst this method is valid, it relies very much on FSUIPC to determine the accuracy of the visual position of the speedbrake lever.  The longevity of the system also very much depends upon the potentiometer used, its +- variance at time of manufacture and its cleanliness.  I wanted to move away from potentiometers and FSUIPC and develop a more reliable and robust system.

Micro-buttons Replace Potentimeter - Goodbye FSUIPC

A series of micro buttons are attached to a half-moon shaped arc made from aluminum.  The arc is installed directly beneath the speedbrake lever’s range of movement.  There are six micro buttons installed and each button corresponds with the exact point that a function will be activated when the speedbrake lever moves over the button.  A further two buttons are used forward of the throttle bulkhead and are associated with arming of the speedbrake.

The benefit of using buttons rather than a potentiometer is accuracy and reliability.  A button is on or off and there is little variance.  A potentiometer on the other hand has considerable variance in both accuracy and reliability.

Relay Card

The micro buttons are connected to a Phidget 0/0/8 relay card (4 relays) that, depending upon the position of the speedbrake lever, turn on or off the programmed speedbrake logic.  The Phidget 0/0/8 relay card is located in the Interface Master Module (IMM). 

Basically, the system is a mechanical circuit controlled by micro switches that reads logic programmed into the Alpha Quadrant cards.  Because it’s a closed system, the logic from the avionics suite (ProSim737) software is not required.  Nor, is calibration by FSUPIC.

Arming the Speedbrake - The Detail

To arm the speedbrake, two micro-buttons, located forward of the throttle bulkhead and attached to a solid piece of metal are used.  Connecting the lower end of the speedbrake lever to the clutch assembly is a green coloured rod.  The rod is the linkage that moves the speedbrake lever.  Adjacent to this rod is a cylinder made from aluminum used to open or close the arming circuit.

As the speedbrake lever is brought into the arm position, the cylinder is moved until it touches either of the arming on/off button-switches.  

The cylinder will stay in the armed position until voltage is provided to the motor to move the speedbrake lever, which in turn moves the rod and cylinder. 

Power is sent to the motor in only two circumstances: when the aircraft lands and the squat switch is activated, or during a Rejected Takeoff (RTO).

LEFT & BELOW LEFTDetail of the speedbrake mechanism (click picture for larger view).  

The motor powering the movement of the lever is the angled motor. The two arming button switches can be seen, one is red the other black, while the rod, clutch assembly and cylinder can easily be identified.


Most enthusiasts use a servo motor to control the movement of the speedbrake lever.  I used a servo motor on my first TQ and was never satisfied at the speed the lever moved; it was always VERY slow and seemed to lack consistent power.

In this conversion a DC electric motor, previously used to automobile power electric windows was used.   The advantage in using a motor of this type is its small size, strong build quality and high torque output.  This translates to more than enough power to mobilize the speedbrake lever.  The motor is mounted to the front of the throttle bulkhead.

Clutch Assembly

The purpose of the clutch is to enable the movement of the motor’s internal shaft to be transferred to the rod which moves the speedbrake lever.  The clutch is fitted with a synthetic washer and a torque nut either loosens or tightens the clutch to either increase or decrease the drag pressure on the speedbrake lever (see photograph).  

Speedbrake Lever Movement - Variable Voltage to Control Speed

The speedbrake lever in the real B737 moves rather slowly when the lever is powered.  Traditionally, this slow movement has been cumbersome to replicate, the movement of the lever either being too slow or too fast.  

Below is a short video showing the speed that the speedbrake lever moves on a real Boeing 737-800 (courtesy & copyright to 737maint U-Tube).  Apologies for the adverts which I can not remove from the embed code.

Altering the Speed of Lever Movement

You will note that the lever movement is speed-controlled in both directions (forward and aft).  Whilst controlling the speed of the lever during landing is relatively easy, controlling the speed of the lever as it is stowed (down) is more difficult.  At this time I have not attempted to control the later speed.

Variable Voltage - 12 Volts

If you provide 12 volts directly to the motor, the lever will move very fast in a movement I have coined the 'biscuit cutter'.  However, if you lower the voltage that is provided to the motor, the speed of the lever will slow.  The crux of the issue is if you provide a voltage that is too low the lever will not move and if the voltage is too high you have a 'biscuit cutter'.   There has to be enough voltage for the motor to provide power to start the movement of the lever and rod. Further, the power must be strong enough to be able to push the cylinder past the on/off switch when the speedbrake is armed and deployed (down), or is being closed (up) when throttles are advanced (after touchdown).

Two Methods  & Troubleshooting Potemtial Problems

I examined two methods to reduce the speed of the lever movement.

The first method uses a commercially manufactured reducer to lower the voltage, to a level that allows the lever to move more slowly than if full voltage was supplied to the motor.  This is the more expensive, but probably the better method to use, as you know exactly what voltage the motor is receiving after the reducer is connected.  Reducers can be purchased that reduce voltage by a known amount.

The second method takes advantage of voltage-reducing diodes and resisters to minimize the voltage coming directly from the relay card (the power connects directly to the relay card).  Although simplistic and less expensive than a reducer, it can be troublesome to determine the correct voltage reduction after the diodes or resisters are installed.  

As stated above, 'too little voltage and the lever will not move or move at a snail’s pace; too fast and your cutting biscuits… '

Although diodes and resisters were used, I believe using a reducer is probably more effective.  Using the former method involves educated "guesswork"  to how much voltage is needed to start the movement of the lever.  I believe a reducer may provide a more measurable approach.

The speed that the lever moves is not "perfect", but is adequate in comparison to the speed that the lever moves in the real aircraft.  I'd like to implement the correct noise that can be heard when the speedbrake is moving.  The noise (heard in the above video) emanates from the hydraulic actuator that pushes the lever mechanism.

Illumination of Speedbrake Condition Annunciators on MIP

As outlined earlier, there are specific operational conditions that dictate the illumination of annunciators on the MIP

It’s not difficult to connect the condition lights on the MIP, to the actual position that the speedbrake lever is in.  To do so requires re-routing the wiring from the lights so that they illuminate at the correct setting as determined by the on/off micro buttons.   Connecting the condition lights completes the speedbrake circuit (movement and illumination) in a closed system separate to the avionics suite.

I have chosen not to do this; therefore, whilst the movement of the lever is a closed system the illumination of condition lights is dictated by the flight avionics.  This said, if the micro buttons have been positioned correctly, synchronization between illumination of the condition lights and the speedbrake lever position will not be problematic.

Upgrading Condtion Annunciators to Closed System

Sometime in the future, I’ll probably opt to attach the condition lights to the speedbrake closed system.   The advantage of this being, that if the developers of the avionics suite alter their speedbrake logic, it will not interfere with the closed system logic I am using.

Power Supply

The speedbrake motor is powered by a Meanwell S150 12 Volt 12.5 amp power supply.

Below is a video showing the movement and speed of the speedbrake lever.  The video also shows how the mechanism operates.  Please ignore the lack of lower display panel and GoFlight panel.  The later is for testing purposes until I have installed a fully functional overhead panel.


B737-500 Throttle Conversion to NG Style - Overview

This is the second throttle unit I’ve owned and based on experience, there are many changes that have been implemented that are different to the earlier unit.

The throttle quadrant is a relatively complicated piece of kit.  To do it justice, rather than write about everything in one very long post, I’ve decided to divide the posts into sections.  

This is the first post that will deal with the general attributes of the throttle unit, interface cards used and touch on the automation and motorization of the unit.  Further detailed posts will address individual functionality, conversion and troubleshooting.

Historical Perspective and Conversion

The TQ and center pedestal were removed from an Alaskan Air Boeing 737-500 airframe.  I purchased the unit directly from the teardown yard in Arizona (via a finder).  

The conversion to full automation and motorization was not done by myself, but by a good friend of mine who is well versed in the intricacies of the B737 and in the various methods used to install automation to a throttle unit.  I am very fortunate to be friends with this individual as in addition to being an excellent craftsman with a though understanding of electronics; he is also a retired Boeing 737 Training Captain.

New Design

The new throttle unit has been converted to Flight Simulator use based on a new design.  The interface cards, rather than being mounted on the forward bulkhead have been mounted within the Interface Master Module (IMM) which is separate to the actual throttle unit.  The DC motors required for throttle and speed brake motorization are mounted forward of the throttle unit (in the traditional location).  

Connection from the throttle to the IMM is via specially-adapted VGA cables and D-Sub plugs.  This keeps the unit clean of unsightly wiring and interface cards.  it also keeps loose cables and wires to a bare minimum on the outside of, and inside the unit; automation and motorization means that there are now moving parts and it’s important to separate delicate cards and wiring away from mechanically moving parts

This is in stark contrast to my first throttle that had the interface cards mounted directly on the forward bulkhead and within the unit.

To read about the Interface Master Module (IMM) navigate to the main tabs at the top of the website.

In addition, micro buttons have been used in some circumstances to counter the traditional method of using potentiometers to control calibration of the speed brake, flaps and throttles.

Center Pedestal - Cabling and Wiring

The three-bay center pedestal, mounted directly behind the throttle unit, has a number of cables and connections required for individual panel operation.  Rather than have these cables weave through the mechanism of the throttle (remember this is an automated throttle and there is considerable movement inside the unit), I’ve opened a hole into the platform directly under the pedestal.  

Any wiring or cabling is routed through this hole into a piece of round flexible conduit tubing (it’s actually the hose from a disused washing machine). The cables, after making their way to the front of the platform, then connect either to the computer or the Interface Master Module.

The use of flexible tubing is not to be underestimated as any cabling must be protected to avoid the chance of snagging on the under-floor yoke and rudder mechanisms which are continually moving.  

Interface Cards

Conversion of any OEM part to operate within Flight Simulator requires interface cards.  The following cards are used to convert analogue outputs to digital inputs for the throttle unit.  The cards also provide functionality for the fire panel, landing gear, yaw dampener, flaps and brake pressure gauges on the Main Instrument Panel (MIP).  All cards are mounted on the separate Interface Master Module (IMM).

  • Alpha Quadrant Motor Controller card A - TQ automation & logic CMD A channel
  • Alpha Quadrant Motor Controller card B - TQ automation & logic CMD B channel
  • Phidget High Current AC Motor Controller card – Provides two channels for trim wheel speeds and trim wheel movement
  • Phidget Motor Controller Advanced Servo card – Provides the interface or bridging between the Alpha Quadrant cards and flight avionics and CMD A
  • Phidget Motor Controller Advanced Servo card - Provides the interface or bridging between the Alpha Quadrant cards and flight avionics and CMD B
  • Phidget Motor Controller Advanced Servo card – Movement of flaps gauge
  • Phidget Motor Controller Advanced Servo card – Movement of trim indicator tabs
  • Leo Bodnar BUO 836 A Joystick Contoller card – Controls all switches & buttons on TQ
  • PoKeys 55 card - Flaps (buttons)
  • Phidget 0/0/8 relay card – Speed brake, auto throttle relays CMD B, fire panels, trim wheel revolution speed on CMD B
  • Belkin 7 input USB 6.5 amp powered mini hub (2) – TQ

Phidget Cards

Phidgets cards provide the necessary interface between the throttle and flight simulator.  I believe that Phidget cards are probably one of the more reliable cards on the market that can be used to directly interface OEM parts to flight simulator.

In addition to the two Alpha Quadrant cards mentioned above, a Phidget High Current AC Controller card acts as a "bridge" to allow communication between the Alpha Quadrant cards and the avionics suite (in this case ProSim737).  This card also provides the connectivity to allow the trim wheels to spin when CMD A or B is selected on the Main Control Panel (MCP).

Trim Tab Indicators and Throttle Buttons

To control the movement of the two trim tab indicators, a Phidget Motor Controller Advanced Servo card is used to control the output to two, two-stage DC motors.  These motors, which are normally used to power water pumps, control the variable speed of the trim indicators and the revolution of the trim wheels.  The speed which the indicator moves is reliant on the user setting within the “trim section” in the configuration page of the flight avionics software.

A Leo Bodnar 386X Joystick Controller card is used to control all switches and buttons on the throttle unit, while a Phidget 0/0/8 relay card is used to turn logic on and off that controls the actions of the speed brake.  


Essentially, automation is the use of CMD A or CMD B (auto pilot) to control the N1 outputs of the throttle, and motorization is the moving of the throttle levers in unison with N1 output.  

Automation is achieved by the use of two main motor controller cards (Alpha Quadrant cards); one for CMD A and another card for CMD B.   Each card operates separately to each other and is dependent upon whether you have CMD A or CMD B selected on the Main Control Panel (MCP).

The Alpha Quadrant cards provide the logic from which the automation of the throttle unit operates.  

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

Main Controller Cards (thanks NASA)

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

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

CMD A/B Auto Pilot - Two Independent Systems

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

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

Synchronized or Independent Motorization

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

In the real aircraft, on earlier airframes, the levers were synchronized; however, the NG has a computer-operated fuel control system which can minutely adjust the N1 of each engine.  This fuel management can be observed in a real aircraft whereby each throttle lever creeps forward or aft independent of the other lever.

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

I decided to maintain the older system and have both levers synchronized.  If at some stage in the future I wish to change this, then it’s a matter of adding another motor to the front of the throttle bulkhead to power the second thrust lever.

Although the TQ is automated, manual override (moving the thrust levers by hand) is possible at any time as long as the override is within the constraints of the real aircraft logic and that provided by the flight avionics (ProSim737).


Four motors are used in the throttle unit.

Two electric motors are mounted forward of the bulkhead.  These motors power the movement of the throttle levers and speed brake.  Two DC “pump” motors are installed directly within the throttle unit and power the movement of the trim wheels and trim tab indicators.

A clutch system is also mounted to a solidly mounted frame on the forward bulkhead.  The clutch system is used by the speed brake.  The method of locomotion between clutch and thrust levers is a standard automobile style fan belt.  

To allow both thrust levers to move in unison, a bar linking the lever which is motorized to the non-motorized lever was fabricated and attached to the main shaft of the motor.  

The motors chosen were automobile electric window motors.  These motors are powerful, provide excellent torque and were selected due to their reliability and ease of use.

Trim Wheel Spinning

The trim wheels can spin at two different speeds dependent upon whether the auto pilot is engaged or whether automation is turned off (manual flying).  A Phidget High Current AC Controller card is used to interface the spinning of the trim wheels.  The Phidget card has two channels and each channel can be programmed to a different revolution speed.  The speed of the revolutions is controlled directly within the Phidget Advanced menu within the ProSim737 software.   

The system was duplicated using a second Phidget card to ensure that both CMD A and CMD B operated identically.

In the real aircraft there are four different revolution speeds dependent upon the level of automation and the radio altitude above the ground.  Although it is possible to program this logic into the Alpha Quadrant cards and bypass ProSim737 software, it was decided not to as the difference in two of the four speeds is marginal and probably unnoticeable.  Further, the level of complexity increases somewhat programming four speeds.

Trim Wheel Braking

In the real aircraft, the trim wheels have an effective braking mechanism that stops the trim wheels from spinning down; basically it’s a brake.  Testing of a military specification motor with brakes to stop wheel movement was done; however, the motors were too powerful and whilst the trim wheels did stop spinning, the noise and jolt of the brake activating was not acceptable.

Functionality and Configuration

The TQ has been converted to allow full functionality, meaning all functions operate as they do in the real Boeing aircraft. Speed brake, flaps, parking break, reverser levers, thrust levers, trim stabilizer runaway toggles, trim tab indications, TOGA and A/T buttons, horn cut out, fuel levers and two speed trim wheel spinning have been implemented.

These functions and the process of conversion and calibration (potentiometers and micro buttons) will be addressed in separate posts.

Configuration, if not directly to the Alpha Quadrant cards via an external software program is either directly through the avionics suite (ProSim737) and the Phidgets card software or through FSUPIC.  Where possible, direct calibration and assignments via FSX have not been used. 


The throttle unit's light plates, with the exception of the parking brake which is illuminated by a 28 Volt bulb, are back lit by 5 Volt aircraft bulbs.  A dedciated S150 5 Volt 30 amp power supply is used to supply power to the bulbs.

Stab Trim T-Locker Toggles

The only function which is different from the real aircraft is the stab trim switch.  The left hand toggle operates correctly for runaway trim; however, the right hand toggle has been configured that, if toggled to the down position, the trim wheels will stop spinning.  The toggle is a basic on/off circuit and stops current going to the motors that move the trim wheels.  

The reason for doing this is that I often fly at night and spinning trim wheels can be quite loud and annoying to non-flyers…  The toggle provides a simple and easy way to turn them on or off at the flick of a switch.

Finding T-Lockers

Finding T-Locker toggles that are used in the NG series airframes is not easy.  Reproduction units are available but they appear cheesy and rarely operate effectively as an OEM toggle.  Earlier airframes used metal paddles (my earlier 300 series throttle used these type of trim switches) while the 400 series uses a different style again.  Trim switches are usually removed and reinstalled into an aircraft; therefore, I was fortunate that the throttle unit I secured had the later model T-Lockers.

The switches are called T-Lockers as you must manually pull down the cover from each switch before pulling the toggle downwards.  This is a safety feature to ensure that the toggles are not inadvertently pushed by the flight crew.

More Pictures (less words...)

To see further pictures, navigate to the Image Gallery (tabs on main menu at top of page).

In this post we have discussed a general overview of the throttle quadrant and examined the automation and motorization.  We also have looked at the interface cards used and studied the stab trim T-Lockers in more detail.  In future posts we will examine the different parts of the throttle unit and learn how they were converted and calibrated to operate with Flight Simulator.

Click any mage to make it larger.