August 01, 2015

Throttle Quadrant Rebuild - New Wiring Design and Rewiring of Center Pedestal

August 01, 2015/ Flaps 2 Approach

oem 737-500 center pedestal. the panels change as oem components are purchased and converted

Put bluntly, the wiring in the center pedestal was not to a satisfactory standard. Several panels were daisy chained together, the wires were not colour coded, and the pedestal looked like a rat’s nest of wires. Likewise, the wiring of the Master Caution System (MCS) required upgrading as several of the original wires showed signs of fraying.

A word of thanks goes to a friend (you know who you are...) who helped wade through the labyrinth of wires!

This post shares several links to other pages in the website.

Wiring Redesign (pedestal and panels)

The set-out of the inside of the center pedestal was redesigned from the ground up, and several of the pedestal panels re-wired to ensure conformity to the new design standard, which was neater and more logical than its predecessor. Additionally, the MCS was rewired using colour-coded wire and the wires labeled accordingly.

New Design (panels must be stand-alone)

The new design called for each panel (module) that was installed into the pedestal to be stand-alone. Stand-alone means that if removal of a panel was necessary, it would be a simple process of unscrewing the DZUS fasteners, lifting the panel out and disconnecting a D-Sub plug and/or 5 volt backlighting wire. Doing this with panels that were daisy chained together was impossible.

The following panels have been re-wired:

(i) EVAC panel;

(ii) Phone panel;

(iii) ACP units (2);

(iv) On/off lighting/flood panel; and,

v) Radar panel.

737-800 EVAC panel, although not a panel that resides in the pedestal, it demonstrates the 'stand-alone' panel philosophy. One D-Sub plug with labelled and colour-coded wire. The mate of the D-sub resides inside the pedestal with the wires connected to the appropriate busbar

All the panels have been retrofitted with colour-coded and labeled D-Sub connections. Removing a panel is a simple as unfastening a DZUS connector, disconnecting a D-Sub connector, and unscrewing the 5 volt backlighting wire from the 5 volt terminal block (if ued). If a USB cable is needed for the panel, then this must also be disconnected.

A word concerning the ACP units, which were converted some time ago with an interface card located on a separate board outside of the unit. As part of the rebuild, the two ACP units were completely re-wired to include the interface card within the unit. Similar to the fire suppression panel, the ACP units are now stand-alone, and only have one USB cable which is used to connect to the computer. The First Officer side ACP is daisy chained to the Captain-side unit.

Center Pedestal Flat Board

A flat board 1 cm in thickness and constructed from wood was cut to the same dimensions of the pedestal base. The board was then attached to the inside bottom of the pedestal by screws. The wood floor has been installed only to the rear two thirds of the pedestal, leaving the forward third open to allow easy access to the platform floor and area beneath the floor structure..

Attached to the flat board are the following items:

(i) FDS 5 Volt IBL-DIST panel power card (backlighting for FDS panels);

(ii) 28 Volt busbar;

(iii) 5 Volt busbar (backlighting);

(iv) 12 Volt relay (controls backlighting on/off tp panel knob);

(v) Terminal block (lights test only);

(vi) Light Test busbar;

(vii) OEM aircraft relay; and a,

(viii) Powered USB hub (NAV, M-COM, ACP & Fire Suppression Panel connection).

The 5, 12 and 28 volt busbars (mounted on the flat board) receive power continuously from the power supplies, mounted in the Power Supply Rack (PSR) via the System Interface Module (SIM). Each panel then connects directly to the respective busbar depending upon its voltage requirement.

In general, 5 volts is used for panel backlighting while 12 and 28 volts is used to power the fire suppression panel, EVAC, throttle unit, phone panel and other OEM components

The flat board has a fair amount of real-estate available; as such, expanding the system is not an issue if additional items need to be mounted to the board.

Lights Test busbar. Similar in design to the 5 volt busbar, its use centralizes all wires and reduces the number of connections to a power supply. Despite the pedestal rewire, there is still a lot of loose wire that cannot be 'cleaned up'. The grey coloured object is the flat board

Lighting Panel Knob (backlighting on/off)

All the panels in the center pedestal require 5 volt power to illuminate the backlighting. The general purpose knob located on the pedestal OEM lights panel is used to turn the backlighting on and off.

Instead of connecting each panel’s wire to the on/off lights panel knob – a process that would consume additional wire and look untidy, each wire has been connected to a 10 terminal 5 volt busbar. The busbar in turn is connected to a 12 volt relay which is connected directly with the on/off knob.

When panel lights knob is turned from off to on, the relay closes the circuit and the busbar is energised; any panel connected to the busbar will automatically receive power.

The busbar and relay are mounted to the flat board.

This system has the advantage that it minimizes the number of wires that are connected to the lights panel knob. It also enables one single high capacity wire to connect from the relay to the knob rather than several smaller gauge wires. This minimises the heat produced from using several thinner wires. It is also easier to solder one wire to the rear of the panel knob than it is to solder several wires.

Lights Test and DIM Functionality

The center pedestal also accommodates the necessary components (Lights Test busbar) to be able to engage the Lights Test and DIM functionality. These functions are triggered by the Lights Test Toggle located on the Main Instrument Panel (MIP).

All wires have been corrected colour coded to various outputs and wire ends use ferrules to connect to the card

Interface Cards

In the previous throttle quadrant, a number of interface cards were mounted within the center pedestal.

To ensure conformity, all the interface cards have been removed from the pedestal and are now mounted within one of the interface modules located forward of the simulator.

Furthermore, all the wiring is colour-coded and the wire ends that connect into the I/O cards use ferrules.

The First Officer-side MCS completely rewired. The MCS has quite a bit of wiring, and making the wire neat and tidy, in addition to being relatively accessible, was a challenge

The use of ferrules improves the longevity of the wiring, makes wire removal easier, and looks neater.

Wiring and Lumens

Needless to say, the alterations have necessitated rewiring on a major scale. Approximately 80% of the internal wiring has had to be replaced and/or re-routed to a position that is more conducive to the new design.

The majority of the wiring required by the throttle unit now resides in a lumen which navigates from the various interface modules (located forword of the simulator) to the Throttle Communication Module (TCM).

From the TCM the lumen routes through the throttle firewall, along the Captain-side of the throttle unit before making its way to the flat board in the center pedestal.

The exception to the above is the cabling required for a powered USB hub located within the center pedestal, the wires required for the Lights Test (from the Lights Test Toggle located in the MIP), and the various power wires navigating to the pedestal from the Power Supply Rack. These wires have been bundled into a separate lumen, which resides beneath the floor structure.

Identifying the voltage of wires is an important aspect of any simulation build

Wire Management

Building a simulator using OEM parts, requires an inordinate amount of multi-voltage wiring of various gauges, and it can be challenge to maintain the wire in a neat and tidy manner.

Running the wire through conduits and lumens does help, but in the end, due to the amount of wire, the number of connections, and the very limited space that is available, the wire is going to appear a little messy. Probably more important, is that the wire conforms to an established design standard – meaning it is colour-coded and labelled accordingly.

A dilemma often facing builders is whether to use electrical tape to secure or bind wires. Personally, I have a strong dislike for electrical tape - whilst it does have its short-term usages, it becomes sticky very easily, and becomes difficult to remove if left on wires for a considerable time .

My preferred method is to use simple cable ties, snake skin casing, or to protect the wires near terminals of OEM parts. to use electrical shrink tubing (which can be purchased in different colours for easy identification of wires and terminals).

Final Product

The design and rewiring of many parts in the simulator has been time consuming. But, the result has been:

(i) That all the wires are now colour-coded and labelled for easy identification;

(ii) The wiring follows a defined system in which common-themed items have been centralised.

(iii) Panels that were daisy chained have been rewired with separate D-Sub plugs so they are now stand-alone;

(iv) The frayed wires from the MCS have been replaced with new wires; and,

(v) The wires in general are neater and more manageable (the rat's nest is cleaner...).

This article is one of several concerning the conversion of the OEM Throttle Quadrant.

July 19, 2015

Throttle Quadrant Rebuild - Four Speed Stab Trim and Stab Trim Indicator Tabs

July 19, 2015/ Flaps 2 Approach

Captain-side stab trim wheel with manual trim handle extended. The white line on the trim wheel is an aid to indicate that the trim wheels are rotating

This post will document several changes that have been made to enable the stab trim wheels to utilise four speeds. I will also discuss several problems that were encountered and their solution. Finally, I will provide some possible reasons for the erratic behavior of the stab trim indicator tabs.

In the previous throttle unit, the power to rotate the trim wheels was from a inexpensive 12 Volt pump motor, and the forward and aft rotation speed of the stab trim wheels was controlled by an I/O card. The system worked well, but the single speed was far from realistic.

The upgrade to the throttle quadrant enables the stab trim wheels to rotate at four speeds which are identical to the speeds observed in a Boeing aircraft. The speed is controlled by three adjustable speed controller cards, five relays and a Phidget 0/0/8 interface card – all of which are mounted within the Throttle Interface Module (TIM).

To generate the torque required to rotate the trim wheels at varying speeds, the pump motor was replaced with an encoder capable 12 volt dual polarity brush motor. The replacement motor is mounted on a customized bracket attached to the inside frame of the throttle unit. This style of motor is often used in the robotics industry.

Boeing Rotation Speed

The speed at which the trim wheels rotate is identical to the Boeing specification for the NG series airframe. Simply written, it is:

(i) Manual trim - speed without flaps (slow speed);

(ii) Manual trim - speed with flaps extended (very fast speed);

(iii) Autopilot trim - speed without flaps extended (very slow speed); and,

(iv) Autopilot trim - speed with flaps extended (faster speed than iii but not as fast as ii).

To determine the correct number of revolutions, each trim wheel cycle was measured using an electronic tachometer. Electronic tachometers are often used in the automobile industry to time an engine by measuring the number of revolutions made by the flywheel.

It is important to understand that it is not the rotation speed of the trim wheels which is important, but more the speed at which the aircraft is trimmed. With flaps extended, the time taken to trim the aircraft is much quicker than the time taken if the flaps were retracted.

Electric stab trim switch on Captain-side yoke. Whenever the trim is engaged the stab trim wheels will rotate with a corresponding movement in the stab trim indicator tabs

Is There a Noticeable Difference Between the Four Speeds

There is definitely a noticeable difference between the speed that the trim wheels rotate at their slowest speed and fastest speed; however, the difference is subtle when comparing the intermediate speeds.

Design and Perils of Stab Trim

If you speak to any real-world pilot that flies Boeing style aircraft, they all agree upon a dislike for the spinning of the trim wheels. The wheels as they rotate are noisy, are a distraction, and in some instances can be quite dangerous, especially if your hand is resting on the wheel and the trim is engaged automatically by the autopilot. This is not to mention the side handle used to manually rotate the trim wheels, which if left extended, can easily damage your knee, during an automatic trimming operation.

If you look at the Airbus which is the primary rival of Boeing, the trim wheels pale by comparison; they are quiet, rotate less often, and are in no way obtrusive. So why is this case?

Boeing when they deigned the classic and NG series aircraft did not design the throttle unit anew. Rather, they elected to build upon existing technology which had changed little since the introduction of the Boeing 707. This saved the company considerable expense.

Airbus, on the other hand, designed their throttle system from the ground-up and incorporated smaller and less obtrusive trim wheels from the onset.

Interestingly, Boeing in their design of the Dreamliner have revamped the design of the stab trim wheels and the new design incorporates smaller, quieter and less obtrusive trim wheels than in the earlier Boeing airframes – no doubt the use of automated and computer controlled systems has removed the need for such a loud and visually orientated system.

Problems Encountered (Teething Issues)

Three problems were encountered when the trim wheels were converted to use four speeds. They were:

(i) Excessive vibration when the trim wheels rotate at the fastest speed;

(ii) Inconsistency with two of the speeds caused when CMD A/B is engaged; and,

(iii) Fluttering (spiking) of the stab trim indicator tabs when the electric stab trim switch was engaged in the down position.

Point (i) is discussed immediately below while points (ii) and (iii), which are interrelated, have been discussed together.

(i) Excessive vibration

When the trim wheels rotate at their highest speed there is considerable vibration generated, which causes the throttle quadrant to shake slightly on its mounts.

Stab trim wheel cog and mechanism (before cleaned) from the First Officer side. The picture shows some of the internal parts that move (and vibrate) when the trim wheels rotate at very high speeds. The high and narrow shape of the throttle unit is easily noted

One of the reasons for the excessive vibration becomes obvious when you compare the mounting points for the throttle quadrant in a homemade simulator to those found in a real aircraft – the later has several solid attachment points between the throttle unit, the center pedestal, the main instrument panel (CDU Bay), and the rigid floor of the flight deck.

In a simulator, replicating these attachment points can be difficult. Also, the throttle is a relatively high yet narrow structure and any vibration will be exacerbated higher in the structure.

Another reason for the cause of the vibrations is the material used to produce the center pedestal. In the classic airframe the material used was aluminum; however, in the NG carbon fiber is used, which is far more flexible than aluminum. Any vibration caused by the rotation of the trim wheels has a tendency to become amplified as it travels to the less rigid center pedestal and then to the floor of the flight deck.

Solution

Solving the vibration issue is uncomplicated – provide stronger, additional, and more secure mounting points for the throttle quadrant and the attached center pedestal, or slow the rotation of the trim wheels to a more acceptable speed. Another option is to replace the platform’s floor with a heavier grade of steel or aluminum. This would enable the throttle quadrant and center pedestal to be attached to the floor structure more securely. However, this would add significant weight to the structure. In my opinion, a heavy steel floor is excessive.

By far the simplest solution, is to reduce the fastest speed at which the trim wheels rotate. The rotation speed can be altered, by the turn of the screwdriver, on one of three speed controller cards mounted within the Throttle Interface Module (TIM).

For those individuals using a full flight deck including a shell, the excessive vibration is probably not going to be an issue as the shell provides additional holding points in which to secure the throttle quadrant, MIP and floor structure.

(ii) Inconsistency with two of the speeds caused when CMA A/B is engaged

When the autopilot (CMD A/B) was selected and engaged on the MCP, the rotation of the trim wheels would rotate at an unacceptable very high speed (similar to run-away trim).

The mechanics of this issue was that when the autopilot was engaged, the electronics was not activating the relay that is responsible for engaging the speed controller card.

(iii) Fluttering of the stab trim indicators

When the electric stab trim switch was depressed to the down position, it was observed that the stab trim indicator tabs would often flutter. Although the fluttering was mechanical and had no bearing on the trim accuracy, or speed at which the aircraft was trimmed, it was visually distracting.

A possible cause for the run-away trim was electromagnetic interference (RF) generated by the high torque of the trim motor. The higher than normal values of RF were being ‘picked up’ by the relay card, which were causing the relay to not activate when the autopilot was engaged. Similarly, the fluttering of the stab trim indicator tabs, was thought to have been caused by RF interfering with the servo motor.

There were several possibilities for RF leakage.

(i) The high torque of the motor was generating and releasing too much RF;

(ii) The wire lumen that accommodates the cabling for the throttle is mounted proximal to the servo motor. If the lumen was leaking RF, then this may have interfered with the operation of the servo motor;

(iii) The servo motor was not digital and did not have an RF shield attached;

(iv) The straight-through cable from the Throttle Communication Module (TCM) to the Throttle Interface Module (TIM) did not have RF interference nodules attached to the cable.

Solution

To counter the unwanted RF energy several modifications were made:

(i) Three non-polarized ceramic capacitors were placed across the connections of the trim wheel motor;

(ii) The analogue servo motor was replaced with a higher-end digital servo with an RF shield;

(iii) The straight-through cable between the TIM and TCM was replaced with a cable that included high quality RF nodes; and,

(iv) The wires from the servo motor were re-routed and shielded to ensure they were not lying alongside the wire lumen.

Manual Trimming

Manual trimming (turning the trim wheels by hand) is not implemented in the throttle quadrant, but a future upgrade may incorporate this feature.

Stab trim cut out switches with spring-loaded cover open on main and closed on autopilot

Cut-out Stab Trim Button (throttle mounted)

In the earlier conversion, the stab trim cut-out toggle was not functional and the toggle had been programmed to switch off the circuit that powers the rotation of the trim wheels. Having the ability to disconnect the rotation of the trim wheels is paramount when flying at night, as the noisy trim wheels kept family members awake.

The new conversion does not incorporate this feature as the trim cut-out toggle is fully functional. Rather, a push-to-engage, green-coloured LED button has been installed to the forward side of the Throttle Interface Module (TIM). The button is connected to a relay, which will either open or close the 12 volt circuit responsible for directing power to the trim motor.

Stab Trim Indicator Tabs

The method used to convert the stab trim indicators has not been altered, with the exception of replacing the analogue servo with a RF protected digital servo (to stop RF interference).

LEFT: Stab trim indicator tabs (Captain side). The throttle is from B737-500. The indicator tabs on the NG airframe are slightly different - they are more slender and pointed (click to enlarge).

To review, a servo motor and a Phidget advanced servo card have been used to enable the stab trim tab indicators to move in synchronization to the revolution and position of the stab trim wheels. The servo card is mounted within the Throttle Interface Module (TIM) and the servo motor is mounted on the Captain-side of the throttle unit adjacent to the trim wheel. There is nothing exceptional about the conversion of the stab trim indicator tabs and the conversion is, more or less, a stock standard.

Is Variable Rotation Speed Important to Simulate

As discussed earlier, it is not the actual rotation of the trim wheels that is important, but more the speed at which the aircraft is trimmed. In other words, the speed at which the trim wheels rotate dictates the time that is taken for the aircraft to be trimmed.

If the trim wheels are rotating slowly, the movement of the stab trim indicator tabs will be slow, and it will take longer for the aircraft to be trimmed. Conversely, if the rotation is faster the stab trim indicator tabs will move faster and the aircraft will be trimmed much more quickly.

Stab Trim Wheel Braking

The amperage of the motor is controlled by a motor controller card; a lower amperage ensures the trim wheel rotates slowly while a high amperage causes the trim wheel to rotate faster. A brake has not been used to stop the rotation of the trim wheel and the wheel rotation stops by inertia or by pushing the electric trim switch (forward or reverse).

A future upgrade may look at using a dynaclutch system or magnetic braking. Another method to install braking is to use software rather than a mechanical system. A motor controller card with a H-Bridge circuit (not available at the time of conversion) could also possibly be used as a brake to stop the trim wheel rotation when the electric trim switch is relesed.

Final Call - is Four-speed Trim Worthwhile

Most throttle conversions implement only one speed for the forward and aft rotation of the trim wheels with the conversion being relatively straightforward.

Converting the throttle unit to use four speeds has not been without problems, with the main issue being the excessive vibration caused by the faster rotation speed. Nevertheless, it is only in rare instances, such as when the stab trim is engaged for longer than a few seconds at a time, and at the fastest rotation speed, that the vibration becomes an issue. If the rotation for the fastest speed is reduced, any vibration issues are alleviated – the downside to this being the fastest speed does not replicate the correct Boeing rotation speed.

For enthusiasts wishing to replicate real aircraft systems, there is little excuse for not implementing four-speed trim, however, for the majority of flight deck builders I believe that two-speed trim, is more than adequate.

Video

Below is a short video, which demonstrates the smooth movement of the stab trim indicator tabs from the fully forward to fully aft position. The video is only intended to present the functionality of the unit and is not to represent in-flight settings.

737 Throttle Quadrant trim tab indicator movement

Below is short video that demonstrates two of the four rotation speeds used. In the example, manual trim is has been engaged, beginning with flaps UP, flaps extended, and then flaps UP again. The rotation speed of the trim wheels with flaps extended (in this case to flaps 1) is faster than the rotation speed with flaps UP. The video does not reflect in-flight operations and is only to present the functionality of the unit in question.

737 Throttle Quadrant variable speed of trim wheels

This article is one of several pertaining to the conversion of the OEM Throttle Quadrant. .

Glossary

Electromagnetic Interference (RF) – RF is a disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source (see Wikipedia definition).
MCP – Mode Control Panel.
MIP – Main Instrument Panel.
Stab Trim Indicator Tabs – The two metal pointed indicators located on the throttle unit immediately adjacent to the %CG light plate. If not using a workable throttle unit, then these tabs maybe located in the lower EICAS as a custom user option.
Servo Motor – Refers to the motor that powers the stab trim indicator tabs.
Trim Motor – Refers to the motor that powers the stab trim wheels.

July 01, 2015

Throttle Quadrant Rebuild - Parking Brake Mechanism Replacement, Improvement, and Operation

July 01, 2015/ Flaps 2 Approach

Parking brake lever in the UP engaged position. The red incandescent bulb is 28 volts, however, a 12 volt bulb can be used. Throttle is Boeing OEM

As part of the throttle quadrant rebuild, the parking brake system was enhanced. In the previous system, the parking brake lever was controlled by a relay and a 12 volt solenoid. The system worked well, however, there were some minor differences between the simulated system and that of the system used in the real Boeing aircraft.

Furthermore, as it was predominately a software system, any change to the avionics suite would affect its operation.

To understand more fully the mechanical linkages used, please read the article regarding the previous system 737 Parking Brake Mechanism .

Revamped System

There has been minimal alteration to the mechanical system, with the exception that the solenoid has been replaced by a 12 volt actuator, a micro-switch has replaced the toggle switch, and the system now requires the toe brakes to be depressed to engage the parking brake.

The actuator is partially visible; the blue coloured mechanism. The parking brake vertical control rod, micro limit switch and upper part of the high tensile spring can be to seen to the lower right

What is an Actuator

An actuator is a type of motor that is responsible for moving or controlling a mechanism or system. It is operated by a source of energy, typically electric current, hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion.

Almost every modern automobile has a door lock actuator which is responsible for the locking and unlocking of the door locks. This website 'How Stuff Works' provides a very good overview of how an actuator works.

The actuator is responsible for maintaining the parking brake lever in the UP position. This occurs when the circuit is closed and 12 volt power is briefly directed to the actuator to lock the device into the engaged position.

The actuator used is an automotive door lock actuator - code BOLA-2 by Bullz-Audio (amazon link).

System Overview

The actuator is the mechanism that enables the parking brake lever to be locked into the UP position. Without power, the actuator is in the resting position and the parking brake lever is pulled to the DOWN position by a high tensile spring.

The annunciator is mounted horizontally on the Captain-side of the throttle quadrant and is powered by 12 volts.

To connect the actuator to the parking brake system, the following items have been used:

An actuator;
A micro-limit switch;
A relay;
A 12 volt power supply and busbar;
A standard interface card (Leo Bodnar BU0836A Joystick Controller card); and,
Depending upon your requirements (mechanical or part mechanical system), a Phidget 0/0/8 card (1017_1).

Registration of Parking Brake Movement

After the parking brake lever has been wired to the BU0836A card, it must be registered in Windows. After this has been completed, the parking brake lever can be assigned in ProSim737, P3D, or FSUIPC.

Micro-Switch and Relay

Two items are used to control whether power enters the circuit: a micro-switch and a double throw relay.

A micro-switch is used to open or close the circuit when the parking brake lever is raised or lowered.

The micro-switch has been mounted proximal to the vertical control rod, and when the parking brake is is in the DOWN position, the connectors from the micro switch are touching a flange that has been attached to the rod, however, when the parking brake lever is moved to the UP position, the connection is severed (circuit open or closed).

The relay is connected to the toe brakes, and when the brakes are depressed, the relay will close. Conversely, when the brakes are released the relay will open. The connection of the relay to the toe brakes can be done a number of ways, but probably the easiest way is to install a button or micro-switch to the toe brakes.

The mechanism, to function correctly, requires that the micro-switch be closed and the parking brake lever be in the raised position. The micro-switch will receive power only when the relay is closed (toe brakes depressed) and the micro-switch is closed (parking lever raised).

In short, the relay (open/closed) is triggered by the movement of the toe brakes and the relay, either enables or inhibits 12 volt power to flow into the circuit, and this is dependent upon the whether the toe brakes are depressed.

The reason for this set-up will be understood shortly.

Toe Brakes

In the real aircraft, the parking brakes can only be engaged or disengaged when the Captain-side or First Officer-side toe brakes are depressed. This mechanical system has been faithfully replicated by using a relay, micro-switch and actuator.

How It Works

The actuator will only engage when the toe brakes are depressed. This means that the parking brake cannot be engaged (lever locked in the UP position with red annunciator on) or disengaged (lever in DOWN position with red annunciator off) unless the toe brakes are depressed.

Depressing or releasing the toe brakes closes or opens the relay which in turn enables 12 volt power to reach the annunciator via the busbar. However, the system is only 'live' (closed system) when the parking brake lever is moved to the UP position, enabling power to flow unhindered through the circuit. When the toe brakes are released, the circuit is open and the actuator remains in the engaged locked position with the parking brake lever locked in the UP position.

To release the parking brake lever, the opposite occurs. When the toe brakes are depressed, the relay opens directing power to the actuator which disengaged the actuator lock. The parking brake lever is then pulled to the DOWN position by the tensile spring.

How To Engage The Parking Brake

The method used to engage the parking brake is as follows:

Slightly depress the toe brakes. This will open the relay and enable 12 volts to engage the actuator;
Raise the parking brake lever to the UP position and hold it in this position; and,
Release the toe brakes. Releasing pressure on the toe brakes causes the actuator to lock into the engaged position, as the power ceases to flow to the actuator.

To release the parking brake, the toe brakes are depressed. This will cause the actuator to unlock and return to its resting position. The high tensile spring will pull the parking brake lever to the DOWN position with a loud snapping sound.

More Ways To Skin A Cat - Full Mechanical or Part-Mechanical

There are several methods that can be used to connect the actuator to the parking brake mechanism. No one method is better than the other. I have outlined two methods. A Phidget 0/0/8 card can also be used, but this method is slightly more convoluted.

(1) Mechanical Method: This has been described above and requires minimal software.

The toe brakes have a micro-switch that connects to a relay, busbar/12 volts power source and the actuator.

The parking brake lever needs to be wired directly to an interface card, registered in Windows, and the l;ever assigned in ProSim-AR, FSX, or FSUIPC.

(2) Part-mechanical/Software Controlled: This involves using the USER section in the configuration menu within ProSim-AR.

A Phidgets 0/0/8 relay card is connected to ProSim-AR and the the USER interface section in the ProSim737 is used to register the movement of the toe brakes. Using a Phidget card removes the need to install a micro-switch or button to the toe brakes.

The USER interface section can be found in the ProSim737 configuration menu. As an example, USER 1 will be used. Each USER IN has a corresponding USER OUT and this is located in GATES. Opening Configuration/Gates, the same USER number is found (USER 1). In the tab beside USER 1 the output from the Phidgets 0/0/8 card is entered. Therefore, whenever USER 1 is triggered, there will be a corresponding output from the Phidget card.

When the toe brakes are depressed, the software will read the movement and send a signal to the Phidget card to engage the relay. This in turn will enable the busbar to be powered and the micro-switch to receive power. Whether the parking brake lever is engaged (UP) or disengaged (DOWN) will open or close the relay controlling the micro-switch (closing or opening the circuit).

The actuator will be engaged (circuit closed) only if the micro-switch (located on the vertical rod mentioned earlier) connection is severed (parking brake lever is in the raised position closing the circuit).

Actuator Power and Caution LED

The 12 volt actuator is connected to the 12 volt busbar in the Throttle Communication Module (TCM) and then, via a straight-through cable, to the Throttle Interface Module (TIM). The relay for the parking brake mechanism is located in the TIM.

The design of an actuator is such, that it will burn out if continuous power is applied to the mechanism for an extended time. However, if the parking brake is used correctly, the actuator will only receive power for a short period of time when the toe brakes are depressed and the parking brake lever is raised at the same time.

To combat against the unforeseen event of power being continuously supplied to the actuator, for example by a relay that is stuck in the open (on) position, a coloured LED has been fitted to the front of the Throttle Communication Module (TCM ). This flashing purple coloured LED illuminates only when the circuit is closed and the actuator is receiving 12 volt power. If the LED is always on it indicates a problem in the system.

Important Point:

Two terms often confused are open circuit and closed in relation to an electrical circuit.

Any circuit which is not complete is considered an open circuit. Conversely, a circuit is considered to be a closed circuit when electricity flows from an energy source to the desired endpoint of the circuit.

Conversely, a closed relay means it allows voltage to travel through it, while an open relay is the opposite.

Additional Information

Like many things, there are several ways to accomplish the same or a similar task. The following posts located in the ProSim737 forum discuss the conversion of the parking brake lever.

How To Make Your Own Parking Brake Release
Parking Brake Logic
This article is one of several that explain the conversion of the OEM Throttle Quadrant.
NOTE: Since publication, ProSim-AR has incorporated into their software a parking brake release 'command'. This by-passes the need to use the USER OUT settings mentioned above. The command is set to the output on the Phidget 0/0/8 card. The parking brake release can be found in the Configuration/Gates menu. (MORE TO COME - under construction).
Updated 04 January 2025

June 11, 2015

Throttle Quadrant Rebuild - Speedbrake Motor and Clutch Assembly Replacement

June 11, 2015/ Flaps 2 Approach

The motor that provides the power to move the speedbrake lever is attached via a slipper clutch to the speedbrake control rod. The slipper clutch can easily be adjusted and if set correctly provides the correct torque required for the speedbrake lever to move. Below the motor is the Throttle Communication Module (TCM) that accommodates, amongst other things, the relays that are used by the logic to control the speedbrake lever's movement

The mechanics of the speedbrake system has been completely overhauled, however, the logic that controls the speedbrake has remained ss it was.

Several problems developed in the earlier conversion that could not be successfully rectified. In particular, the speed of the speedbrake lever when deployed was either too fast, too slow, or did not move at all, and the clutch mechanism frequently became loose.

Other minor issues related to the condition korrys that illuminate when the speedbrake is either armed or extended; these korrys did not always illuminate at the correct times.

Rather than continually‘tweak the earlier system, it was decided to replace the motor and clutch assembly with a more advanced and reliable system. To solve the arming issue, a linear throw potentiometer has been used to enable accurate calibration of the speedbrake lever in Prosim737.

To read about the first conversion and learn a little more about closed-loop systems and how the speedbrake works, please read the companion article PRIOR to reading this article. This article only addresses the changes made to the system and builds on information discussed in the other article: 737 Throttle Quadrant Speedbrake Conversion and Use.

Motor and Clutch Assembly

A 12 volt motor is used to power the speed brake. The motor is mounted forward of the throttle unit above the Throttle Communication Module (TCM). The wiring from the motor is routed, in a lumen through the throttle firewall to a 12 volt busbar and several relays. The relays, mounted inside the TCM, are dedicated to the speedbrake.

Attached to the 12 volt motor is a slipper-clutch assembly, similar in design to the slipper clutches used in the movement of the two throttle thrust levers. The clutch can easily be loosed or tightened (using a pair of padded pliers) to provide the correct torque on the speedbrake lever, and once set will not become loose (unless exposed to constant vibration).

The slipper clutch and bearings have been commercially made.

A linear throw potentiometer has been mounted on the Captain-side of the quadrant. The potentiometer enables the movement of the speedbrake lever to be finely calibrated in ProSim737

Speedbrake Mechanics

In the real Boeing 737 aircraft, buttons are located beneath the metal arc that the speedbrake travels. If you listen carefully you can hear the buttons clicking as the lever moves over the button. These on/off buttons activate as the speedbrake lever travels over them, triggering logic that causes the speedbrake to move.

This system has been replicated by using strategically placed micro-buttons beneath the speedbrake lever arc. As the speedbrake lever moves over one of the buttons, the button will trigger a relay to either open or close (on/off). To replicate the speedbrake system requires the use of 4 relays (speedbrake armed, stowed, engaged on landing, or placed in the UP position). A Phidget 0/0/8 relay card has been used and this card is mounted inside the Throttle Communication Module (TCM).

Speedbrake Korry (armed and extended)

The speedbrake system is a closed system, meaning it does not require the avionics suite (ProSim737) to operate. However, the illumination of the condition lights (speedbrake armed and extended on the MIP) is not part of the closed loop system and the korrys must be configured in ProSim737 (switches/indicators).

An easy workaround to include the arm korry to the closed loop system is to install a micro-switch beneath the speedbrake lever arc. The position of the micro-switch needs to correspond to the position of the lever when it is moved to the armed position. Then, when the level travels over the micro-switch the arm korry will illuminate.

Speedbrake Operation

To connect the mechanical system to the avionics, a linear throw potentiometer has been connected to a Leo Bodnar BU0836A Joystick Controller card. This enables the movement of the speedbrake lever to be calibrated in such a way that corresponds to the illumination of the korrys and the extension of the spoilers on the flight model. The potentiometer has been mounted to the throttle superstructure on the Captain-side.

Using a potentiometer enables the DOWN and ARM position to be precisely calibrated in ProSim737 (config/throttle & MCP/Levers).

The following conditions will cause the speedbrake lever to deploy from the DOWN to the UP position.

When the aircraft lands and the squat switch is activated;
During a Rejected Takeoff (RTO). This assumes that the autobrake selector switch has been set to RTO, there is active wheel spin, and the groundspeed exceeds 80 knots; and,
If the reverse thrust is engaged with a positive wheel spin and a ground speed in excess of 100 knots.

Point 3 is worth expanding upon. The speedbrake system (in the real aircraft) has a built-in redundancy in that if the flight crew forget to arm the speedbrake and make a landing, the system will automatically engage the spoilers when reverse thrust is engaged. This redundant system was installed into the Next Generation airframe after several occurrences of pilots forgetting to arm the speedbrake prior to landing.

Therefore, the speedbrake will deploy on landing either by activation of the squat switch (if the speedbrake was armed), or when reverse thrust is applied.

Speedbrake Logic

The following logic have been programmed into the logic that controls the operation of the speedbrake.

Rejected Take Off (RTO). RTO can occur after the 80 knots call-out. Spoilers will extend to the UP position when reverse thrust is applied. The speedbrake lever moves to UP position on throttle quadrant. RTO must be armed prior to takeoff roll;
Spoilers extend on landing when the squat switch is activated. For this to occur, both throttle thrust levers must be at idle (at their stops). The speedbrake lever must also be in the armed position prior to landing. The speedbrake lever moves to the UP position;
Spoilers extend automatically and the speedbrake lever moves to the UP position when reverse thrust is applied;
Spoilers close and the speedbrake lever moves to the DOWN position when the thrust levers are advanced after landing (auto-stow); and,
Speedbrakes extend incrementally in the air dependent on the lever position (flight detent).

The logic for the speedbrake is 'hardwired' into the Alpha Quadrant card. The logic has not changed from what it was previously.

Speedbrake Lever Speed

When the speedbrake lever is engaged, the speed at which lever moves is quite fast. The term ‘biscuit cutter’ best describes the energy that is generated when the lever is moving; it certainly will break a biscuit in two as well as a lead pencil. Speaking of lead pencils, I have been told a favorite trick of pilots from yesteryear, was to rest a pencil on the throttle stop so that when the speedbrake engaged the pencil would be snapped in two by the lever!

The actuator that controls the movement of the speedbrake. This image was taken from beneath the floor structure of a Boeing 600 aircraft. Image copyright to Karl Penrose

In the real Boeing 737 aircraft the movement of the lever is marginally slower and is controlled by an electrically operated actuator (28 volts DC).

In theory, the slower speed that the speedbrake lever moves in the real aircraft should be able to be duplicated; for example, by suppressing the voltage from the 12 volt motor using a capacitor, using a power supply lower than 12 volts, or by using speed controllers. These alternatives have yet to be trialed.

It is unfortunate that most throttle quadrants available to the simulation community do not include the actuator. The actuator is not part of the throttle unit itself, but is located in the forward section under the flight deck. The actuator is then connected to the speedbrake mechanism unit via a mechanical linkage.

In the real aircraft, the speedbrake lever and actuator provide the input via cables, that in-turn actuate the speedbrakes. There is no feedback directly from the hydraulics and all operation is achieved either by manual or electric input of the speedbrake lever.

Actuator Sound

The sound of the actuator engaging can easily heard in the flight deck when the speedbrake engages (listen to the below video). To replicate this sound, the sound of the actuator engaging was recorded. The .wav sound file was then uploaded into the ProSim737 audio file library and configured to play when the speedbrake is commanded to move (squat switch).

The .wav file can be shortened or lengthened to match the speed that the lever moves.

The actuator sound can be downloaded from the File Download tab.

Synopsis

I realize this and the companion article are probably confusing to understand. In essence this is how the speedbrake operates (in no particular order):

A potentiometer enables accurate calibration (in ProSim737) of the DOWN and ARM position of the speedbreak lever. This enables the condition korrys to illuminate at the correct time.
Micro-buttons have been installed beneath the arc that the speedbrake lever travels. The position of each button, is in the same position as the on/off buttons used by Boeing (the buttons are still present and you can hear them click as the speedbrake lever moves across a button).
The micro-buttons are connected to a Phidget 0/0/8 relay card (4 relays). The relay card is located within the Throttle Communication Module (TCM).
The speedbrake system is a closed-loop system and does not require ProSim737 to operate.
The logic for the system has been programmed directly into the Alpha Quadrant card mounted in the Throttle Interface Module (TIM). This logic triggers relays, located in the Throttle Communication Module (TCM) to turn either on or off as the speedbrake lever travels over the micro-buttons. This is exactly how it's done in the real aircraft.
The speedbrake moves from the ARM position to the UP position when the squat switch is triggered (when the landing gear touches the runway). The squat switch is a configured in ProSim737 (config/gate/squat switch).

Video

The upper video demonstrates the movement of the speedbrake lever. The lower video, courtesy of U-Tube, shows the actual movement of the lever in a real Boeing aircraft.

The video is not intended for operational use, but has been shown to demonstrate the features of the speedbrake system.

If you listen carefully to both videos, you will note a difference in the noise that the actuator generates. I have been informed that the 'whine' noise made by the actuator is slightly different depending upon the aircraft frame; the actuator in the older classic series Boeing being more of a high whine in comparison to the actuator in the Next Generation aircraft.

737-500 automated speedbrake deployment

This article comprises one of several articles relating to the conversion of the OEM Throttle Quadrant.

Glossary

Condition(s) - A term referring to a specific parameter that is required to enable an action to occur.
FSUIPC - Flight Simulator Universal Inter-Process Communication. A fancy term for software that interfaces between the flight simulator programme and other outside programmes.
Speedbrake Lever Arc - The curved arc that the speedbrake lever travels along.

Updated 11 July 2020.
Updated 03 January 2025

May 20, 2015

Book Review - Touch and Go Landings by Jonathan Fyfe

May 20, 2015/ Flaps 2 Approach

I read Jonathan Fyfe’s initial on-line tutorial Flying the Circuit in the 737 some time ago. I was impressed with Fyfe’s writing style which is succinct and easy to read. As a result I was keen to review his latest publication ‘Touch and Go Landings in the 737 NGX which is a follows on from his original tutorial.

Overview

The book (here on referred to as a guide) is paperback A5 in size, is 135 pages in length and has been printed in colour. The guide is printed on quality paper and has a glossy-style plastic cover.

As the title of the text eludes, the guide examines in-depth all the aspects needed by a flight crew to successfully fly the Boeing 737 in a standard circuit, including crosswind approaches, missed approaches, engine out operations and rejected takeoffs. Although the title of the guide may not appear substantive, the guide addresses nearly everything required to conduct a manual/part automated takeoff and landing.

Detail

I was surprised at the volume of information that Fyfe has managed to place in the guide; initially I thought the content appeared rather thin; however, closer examination revealed a wealth of information covering both systems and procedures. This is in addition, to pictures that demonstrate correct landing technique and diagrams that are well-presented and clear.

Derated takeoffs, assumed temperature thrust reduction, descent profiles, runway markings, drift calculations and aircraft systems data, which include: spoiler use, flap schedules, flight deck warnings, use the autothrottle and controlled wheel steering – too mention a few, are explained.

Well-written Framwork

Fyfe’s ability as a flight instructor and educator comes to bear in the nature of how he explains the various procedures. He does not ‘parrot’ procedures, the FCOM or FCTM, but rather adds to this information by his ability to be able to shape the material into a parcel that is easily understood.

Many of the more complicated aspects, such as crosswind approaches, the effects of wind and the balanced field length are explained more clearly by the use of coloured diagrams. This translates to a guide that is very easy to comprehend allowing the reader to easily apply the information when flying their simulated aircraft.

Breakdown

The guide is divided into three primary lessons which encompass: standard circuits, missed approach and crosswind circuits and engine out/asymmetrics.

Each section has three sub-sections.

Groundwork;
Systems; and,
Air Work.

In groundwork, the theory and methodology for the upcoming lesson is primarily discussed, along with a lesson briefing. In Systems, the focus is towards pertinent information that relates to the lesson; for example, flap positions, warning horns, autothrottle, N1 calculations and FMA annunciations. In Air Work, a tutorial-style lesson is presented, in which Fyfe explains the necessary procedures to complete the lesson. The student (you) can set-up their simulator to mimic the same conditions that Fyfe is flying. This allows the student to self-evaluate their ability.

All the sub-sections, but especially so in air work, are augmented by several screenshots depicting aircraft positions and instrument readings.

The lessons revolve around the use of the Boeing 737 NGX produced by Precision Manuals Development Group (PMDG) and Flight Simulator 10 (FSX); however, the information can easily be applied to any simulated B737 that is using a professional avionics suite, such as ProSim737, Sim Avionics, Project Magenta, I-Fly, etc.

Some enthusiasts may find the guide lacking in that it does not attempt to explain or demonstrate the various automated-style approaches that the B737 is capable of (ILS, VOR, IAN, RNAV, etc.). Nor does it cover off on climbing to altitude, descent or cruise. Although this knowledge is important, it is not relevant to touch and go takeoffs and landings.

Peer Review

The amount of information, especially on the Internet concerning flying the Boeing 737 aircraft is voluminous; however, a caveat must be issued in that much of this information has not been peer reviewed and in many instances is not correct. Although there are numerous monographs available that deal with the Boeing aircraft, these texts are usually very expensive and have not been written with the lay person in mind; often they are technical and assume an inherent level of prior knowledge. Likewise, the FCOM, FCTM are certainly very helpful documents; however, they have been written for trained flight crews and their method of explanation is often clouded without prior knowledge and experience in aircraft systems.

In this guide, Fyfe has succeeded in translating much of this information in a concise way that is easy to read and comprehend.

Fly Dubai - steep climb out after touch and go (photograph copyright Mohammadreza Farhadi Aref)

Why Touch and Go - Why Are They Important

Some enthusiasts may wonder why knowing how to accomplish a touch and go landing is important. After all, surely it is more important to understand the intricacies of a full stop landing using one of the several approach types that the B737 is certified to carry out, and be able tom land the aircraft following the procedure outlined in the approach chart.

Flying circuits and performing touch and go landings will vastly improve your airmanship, as a good majority of what is required during touch and go landings can be applied to other aspects of flying the B737. Additionally, the touch and go procedures are consolidated into a time-dependent envelope in which everything occurs relatively quickly. If a virtual flyer is competent in carrying out a touch and go landing, then it is a very easy transition to use one of the more advanced approach formats.

Final Call and Score

‘Touch and Go Landings’ is aimed at the novice to intermediate virtual pilot who wishes to learn the correct procedures first time around; advanced users will also benefit by not second guessing procedures they are presently using. This said, there are many ways to fly the Boeing 737 aircraft, and often the method chosen depends on the flight crew, environmental constraints and the airline policy.

It is important to realise that the guide is not a glorified tutorial written by an aviation enthusiast, but rather is a thoroughly researched and well written and easy to read text, that provides a pallet of information and comprehensive procedures that are relevant to flying the B737. The guide not only provides a framework of what to do, but it also explains the how and why.

To read more about the guide or to purchase a copy, navigate to the author's website at www.jf737ngx.wordpress.com. Otherwise, copies can be purchaed directly from Amazon.

The current retail price is $24.95.

Introductory discount coupons are available, for a limited time, at Jonathan Fyfe’s website.

I have given the guide a score of 9/10.

Transparancy

I have not received remuneration for this review; however, I was provided a guide ‘gratis’ to read. The review is my opinion.

Glossary and Acronyms

FCOM – Flight Crew Operations Manual (Boeing airline specific document)
FCTM – Flight Crew Training Manual (Boeing airline specific document)
FMA – Flight Mode Annunciations

May 06, 2015

B737 Original Equipment Manufacture RMI Knobs Fully Functional

May 06, 2015/ Flaps 2 Approach

oem rmi knobs mounted to the potentiometers that control the rmi

In two previous posts, I documented the installation of two bespoke reproduction RMI knobs and aN OEM ADF/VOR switch assembly mounted in the center pedestal. The purpose of the switch assembly, which originally was used in a Boeing 727 airframe, was to provide an easy method to switch between ADF and VOR as the two knobs mounted on the RMI were non-functional.

With the acquisition of OEM RMI knobs, the next step was to implement the functionality of these knobs by installing micro-rotary switches to the RMI frame behind each knob. The non Next Generation compliant RMI Switch Assembly panel would then be superfluous and removed from the center pedestal.

Installing the Micro-rotary Switches to the RMI Frame

The first step was to remove the RMI frame from the MIP and enlarge the holes that the RMI knobs reside. This is to allow the installation of the two micro-rotary switches. To do this, a Dremel rotary tool was used.

To enable the wires from the rotary switches to be routed neatly behind the RMI frame, a very narrow trench was cut into the rear of the plastic frame. It is very important that this task is done with due diligence as the RMI frame produced by Flight Deck Solutions (FDS) is manufactured from ABS plastic and not metal – if the cut is too deep or too much pressure is applied to the Dremel, then the frame will be damaged.

The wires from the the RMI knobs are then laid inside the earlier cut trench and aluminum-based tape is applied over the wires. This ensures the wires are secure and do not dislodge from the RMI frame.

The micro-rotary switches used in this conversion are 1 cm in length (depth); therefore, to use these rotaries successfully you will need to have a certain amount of airspace between the rear of the RMI frame and front of the computer screen (central display unit). Whether there is enough room to facilitate the installation of the rotary switch, will depend upon the manufacturer of the MIP and RMI frame – some manufacturers have allowed a centimeter or so of space behind the RMI frame while others have the frame more or less flush to the center display unit screen. If the air space is minimal, the rear of the rotary may rub against the display unit.

RMI frame and OEM knobs connected to small rotary potentiometers. Note the metal sleeve and grub screw in the knob.

There are several methods that can be used to secure the rotaries to the RMI frame. By far the easiest is to enlarge the hole in the RMI frame to a diameter that the rotary can be firmly pushed through the hole and not work its way loose. Another method, more permanent, is to glue the rotary inside the hole. No matter which method used, the rotary must be secured inside the hole otherwise when the RMI knob is turned the rotary will swivel within the hole.

Once the rotaries are installed to the frame, the OEM knobs are carefully pushed over the rotaries and the metal grub screws on the knob tightened. One of the benefits of using OEM knobs is that the inside of the knob has a metal sleeve which ensures that the knob will not wear out and slip with continual use – reproduction knobs rarely are manufactured with an inside metal sleeve.

Interface Card and Configuration

To enable functionality, the wires from the rotaries are carefully threaded through the MIP wall and routed to an interface card; A PoKeys card, mounted in the System Interface Module (SIM), has been used. It is not necessary to use a large gauge wire to connect the rotaries to the interface card. This is because the electrical impulse that travels through the wire is only when the RMI knob is turned, and then it is only for a scone or so.

The functionality for the RMI knobs is configured within the ProSim737 avionics suite in the configuration/switches area of the software.

Micro-rotary Switches

There are several micro-rotary switches available in the market. This conversion uses A6A sealed rotary DIP switches; they are compact and inexpensive.

When selecting a rotary, bear in mind that many rotaries are either two, three or four clicks in design. This means that for a 90 degree turn, such as required when altering the RMI from VOR to ADF, the rotary will need to travel through a number of clicks to correspond with the visual position of the switch.

The A6A type mentioned above are a two click type. The first click will change the designation (VOR to ADF or back again), however, for realism two clicks are made (90 degree turn). At the time of the conversion it was not possible to find a small enough rotary that was one click. Despite this shortcoming, the physical clicks are not very noticeable.

This conversion is very simple and is probably one of the easiest conversions that can be done to implement the use of OEM knobs. There is minimal technical skill needed, but a steady hand and a good eye is needed to ensure the RMI frame is not damaged when preparing the frame for the installation of the two rotary switches.

oem rmi knobs in original plastic bag. note metal inner sleeve and grub screw

OEM RMI Gauge

This conversion uses two OEM RMI knobs and rotaries to interface with the standard virtual RMI gauge provided within the ProSim737 avionics suite. Converting an OEM RMI gauge for standalone operation is possible and has been accomplished by other enthusiasts; however, whether a full RMI conversion can be done very much depends upon your particular simulation set-up.

If a OEM RMI gauge is installed, there may be a spacing issue with the other alternate gauges. In particular, the Integrated Standby Flight Display (ISFD) will require a smaller dedicated display screen. Likewise, the EICAS display screen will need to be smaller so as to fit between the RMI gauge and the landing gear assembly. Also, an extra display port will be required for the computer to read the ISFD display screen.

Certainly, a complete conversion of a RMI gauge is the best way to proceed, if you already own a OEM RMI unit, and if the set-up problems are not too difficult to overcome.

Acronyms

MIP – Main Instrument Panel
OEM – Original Equipment Manufacturer
RMI – Radio Magnetic Indicator

April 24, 2015

ANZAC Day - Lest We Forget

April 24, 2015/ Flaps 2 Approach

Royal New Zealand Fighter Pilots circa Second World War. New Zealand and Australia have always been close allies. ANZAC is the abbreviation for Australian and New Zealand Army Corps. 15 Squadron at Whenuapai NZ about late September 1942

In Australia, April 25th is known as ANZAC Day. ANZAC day began in 1916 and initially was a part day holiday to reflect on those soldiers, who in the First World War had lost their lives in Gallipoli. Over the years, the day has become one in which to reflect on all those from all services and corps who have lost their lives in military conflicts that Australia has been involved in.

The significance of ANZAC Day to many Australians, is as a day in which to reflect on the courage and sacrifice of others, and the fact that Gallipoli and other similar actions helped to forge Australia as a nation - a nation that came into being as the Commonwealth of Australia in 1901.

What is the connection between ANZAC Day and the building of a B737-800 flight simulator or for that matter aviation in general?

The carnage of war was one of the main catalysts to the evolution of many new innovations of which aviation was but one. Of importance. was the emergence of the Australia Flying Corps (AFC) which was the forerunner of the Royal Australian Airforce (RAAF).

QANTAS

Emerging from the hell of the Great War came three Australians (Fysh, M’Ginness and McMaster) who, toughened by war, hardship and bonded by mateship, developed what would be the second oldest airline in the world. In 1920 the trio formed the Queensland and Northern Territory Aerial Services Ltd, or QANTAS.

Hudson Fysh was born in Launceston, Tasmania, on 7 January 1895. He enlisted with the 3rd Light Horse Regiment, at the outbreak of World War I and saw active service at Gallipoli, Sinai and Palestine before transferring to the Australian Flying Corps. He was commissioned at a lieutenant and served as an air gunner with No. 1 Squadron AFC in Palestine and received a Distinguished Flying Cross for his gallantry in air combat and attacking ground targets in late 1918.

Fysh and M'Ginness in AFC attire circa 1918

Paul McGinness was born at Framlingham, Victoria, on 4 February 1896. He joined the 8th Light Horse Regiment in 1914 as a trooper. After training in Egypt, he served at Gallipoli where he was one of the few survivors of the charge at The Nek in August 1915 and was wounded. He later received the Distinguished Conduct Medal for scouting and leadership in the Sinai desert in 1916.

.Fergus McMaster fought in the Great War as a gunner with the 7th Battery, 3rd Brigade, Australian Field Artillery at Amiens, Villers-Bretonneux and Hamel.

W Arthur Baird was not a founding a member of QANTAS; however, his engineering skill was vital to the early success of the air service. Baird joined the Australian Flying Corps and served as a flight sergeant in Palestine with No. 1 Squadron AFC where he met Paul McGinness and Hudson Fysh. He was awarded the Meritorious Service Medal (MSM) for his ability to maintain aero engines in difficult conditions, and Baird was an obvious choice to keep the aircraft flow by QANTAS in the air.

Lest We Forget.

April 20, 2015

Boeing Nut Cracker - Loosening Stab Trim Wheel Nuts

April 20, 2015/ Flaps 2 Approach

Boeing Nut Cracker - two raised lugs fit firmly into their opposite number to enable the stab trim wheel nut to be easily loosened or tightened

Any industry has tools that have been designed for a specific task – whether it is for automotive, construction or aviation.

Specialist tools enable a particular job to be accomplished quickly and effectively with the minimum of fuss. More importantly, damage to a part is less likely when using a specialised tool.

A person who makes tools usually has a trade certificate and those who are gifted in this area are called boiler makers; a gifted boiler maker can literally make anything.

Stab Trim Wheel Nut

The stab trim wheels have two nuts that hold the trim wheels in place - one on each side of the throttle quadrant. When attempting to remove the trim wheel nut it is a good idea to use a tool, as the nut can be easily damaged (burred).

The nut has two shallow indentations each side of it to enable it to be firmly tightened.

Often the nut is over-tightened by the continual rotation of the trim wheels, or by an overzealous technician applying more force than they should. If the nut has been over tightened, removing the trim wheels can be difficult.

A common man’s blade screwdriver can be used to loosen the nut, by applying the blade to one side of the two indentations, grasping the trim wheel firmly and turning the driver. But, do not be surprised if the recessed indents are damaged, the screwdriver slips and scratches something, or worse you end up with the blade of the screwdriver through your hand!

Boeing Specialised Tool

Boeing technicians use a specialised tool to loosen and tighten the nuts that hold the trim wheels in place – no doubt it also has a special name (?). This tool, like all specialist tools is expensive, and more so because it is used in the aviation industry.

I explained the problem to a friend of mine who like a ‘genie in a bottle’, designed and made this small tool for me. It is not fancy or technical, but it does the job it has been designed to do especially well – every time.

The tool is made from aluminium with two raised indentations that fit into the two recessed indentations on the trim wheel nut. A simple shaft placed through a drilled hole in the stem of the tool enables the user to apply enough leverage to 'crack' all but the most resistant of trim wheel nuts.

The heavy duty cog wheel that the trim wheels are secured to. When removing the trim wheels it is very important not to dislodge the cog as the bearings on the inner side of the cog will fall out of alignment

Caution - Removing the Trim Wheels from the Main Shaft

Whenever the trim wheels have to be removed from the throttle quadrant, it is very important not to dislodge the cog by pushing or pulling the shaft through the throttle unit. This is relatively easy to do as often the trim wheels adhere to the cog.

Attached to the cog (inside the throttle unit) are several bearings, which if dislodged, will fall out of alignment. The bearings are important to the correct functioning of the trim wheels and it is very difficult, if not impossible, to reinstall the bearings after they have fallen out of place.

When removing the trim wheels, carefully 'jiggle' the trim wheel until it works its way loose of the cog - never forcefully pull the trim wheel outwards as the cog and shaft may come out of the throttle unit, allowing the bearings to fall out of alignment. Furthermore, be mindful that when you remove one of the trim wheels the other may rotate forward or backwards due to centrifugal force.

Before replacing the trim wheels, to help avoid the wheel from sticking to the shaft and cog, apply an amount of grease to the cog teeth.

Update

on 2016-05-26 00:01 by FLAPS 2 APPROACH

This tool has now been replaced with a new design with better engineering. To read about the new tool: Trim Wheel Nut Tool - New Design.

April 06, 2015

Throttle Quadrant Rebuild - Clutch, Motors, and Potentiometers

April 06, 2015/ Flaps 2 Approach

Captain-side of throttle quadrant showing an overview of the new design. The clutch assembly, motors, and string potentiometer can be seen, in addition to a portion of the revised parking brake mechanism

An earlier article, Throttle Quadrant Rebuild – Evolution Has Led to Major Changes has outlined the main changes that have been made to the throttle quadrant during the rebuild process.

This article will add detail and explain the decision making process behind the changes and the advantages they provide. As such, a very brief overview of the earlier system will be made followed by an examination of the replacement system.

Limitation

It is not my intent to become bogged down in infinite detail; this would only serve to make the posts very long, complicated and difficult to understand, as the conversion of a throttle unit is not simplistic.

This said, the provided information should be enough to enable you to assimilate ideas that can be used in your project. I hope you understand the reasoning for this decision.

The process of documenting the throttle quadrant rebuild will be recorded in a number of articles. In his article I will discuss the clutch assembly, motors, and potentiometers.

Why Rebuild The Throttle Quadrant

Put bluntly, the earlier conversion had several problems; there were shortfalls that needed improvement, and when work commenced to rectify these problems, it became apparent that it would be easier to begin again rather than retrofit. Moreover, the alterations spurred the design and development of two additional interface modules that control how the throttle quadrant was to be connected with the simulator.

TIM houses the interface cards responsible for the throttle operation while the TCM provides a communication gateway between TIM and the throttle.

Motor and Clutch Assembly - Poor Design (in previous conversion)

The previous throttle conversion used an inexpensive 12 volt motor to power the thrust lever handles forward and aft. Prior to being used in the simulator, the motors were used to power electric automobile windows. To move the thrust lever handles, an automobile fan belt was used to connect to a home-made clutch assembly.

This system was sourly lacking in that the fan belt continually slipped. Likewise, the nut on the clutch assembly, designed to loosen or tighten the control on the fan belt, was either too tight or too loose - a happy medium was not possible. Furthermore, the operation of the throttle caused the clutch nut to continually become loose requiring frequent adjustment.

The 12 volt motors, although suitable, were not designed to entertain the precision needed to synchronize the movement of the thrust levers; they were designed to push a window either up or down at a predefined speed on an automobile.

The torque produced from these motors was too great, and the physical backlash when the drive shaft moved was unacceptable. The backlash transferred to the thrust levers causing the levers to jerk (jump) when the automation took control (google motor backlash).

This system was removed from the throttle. Its replacement incorporated two commercial motors professionally attached to a clutch system using slipper clutches.

Close up image of the aluminium bar and ninety degree flange attachment. The long-threaded screw connects with the tail of the respective thrust lever handle. An identical attachment at the end of the screw connects the screw to the large cog wheel that the thrust lever handles are attached

Clutch Assembly, Connection Bars and Slipper Clutches - New Design

Mounted to the floor of the throttle quadrant are two clutch assemblies (mounted beside each other) – one clutch assembly controls the Captain-side thrust lever handle while the other controls the First officer-side.

Each assembly connects to the drive shaft of a respective motor and includes in its design a slipper clutch. Each clutch assembly then connects to the respective thrust lever handle. A wiring lumen connects the clutch assembly with each motor and a dedicated 12 volt power supply (mounted forward of the throttle quadrant). See above image.

Connection Bars

**diagram 1:** crossection and a cut-away of a slipper clutch

To connect each clutch assembly to the respective thrust lever handle, two pieces of aluminium bar were engineered to fit over and attach to the shaft of each clutch assembly.

Each metal bar connects to one of two long-threaded screws, which in turn connect directly with the tail of each thrust lever handle mounted to the main cog wheel in the throttle quadrant.

Slipper Clutches

close up of slipper clutch showing precision ball bearings

A slipper clutch is a small mechanical device made from tempered steel, brass and aluminum. The clutch consists of tensioned springs sandwiched between brass plates and interfaced with stainless-steel bearings. The bearings enable ease of movement and ensure a long trouble-free life.

The adjustable springs are used to maintain constant pressure on the friction plates assuring constant torque is always applied to the clutch. This controls any intermittent, continuous or overload slip.

A major advantage, other than their small size, is the ease at which the slipper clutches can be sandwiched into a clutch assembly.

Anatomy and Key Advantages of a Slipper Clutch

A number of manufacturers produce slipper clutches that are specific to a particular industry application, and while it's possible that a particular clutch will suit the purpose required, it's probably a better idea to have a slipper clutch engineered that is specific to your application.

The benefit of having a clutch engineered is that you do not have to redesign the drive mechanism used with the clutch motors.

Key advantages in using slipper clutches are:

Variable torque;
Long life (on average 30 million cycles with torque applied);
Consistent, smooth and reliable operation with no lubrication required;
Bi-directional rotation; and,
Compact size.

The clutch assembly as seen from the First Officer side of the throttle quadrant. Note the slipper clutch that is sandwiched between the assembly and the connection rods. Each thrust lever handle has a dedicated motor, slipper clutch and connection rod. The motor that powers the F/O side can be seen in the foreground

Clutch Motors

The two 12 Volt commercial-grade motors that provide the torque to drive the clutch assembly and movement of the thrust lever handles, have been specifically designed to be used with drives that incorporate slipper clutches.

In the real world, these motors are used in the railway and marine industry to drive high speed components. As such, their design and build quality is excellent. The motors are designed and made in South Korea.

Each motor is manufactured from stainless steel parts and has a gearhead actuator that enables the motor to be operated in either forward or reverse. Although the torque generated by the motor (18Nm stall torque) exceeds that required to move the thrust lever handles forward and aft, the high quality design of the motor removes all the backlash evident when using other commercial-grade motors. The end result is an extraordinary smooth, and consistent operation when the thrust lever handles move.

A further benefit using this type of motor is its size. Each motor can easily be mounted to the floor of the throttle quadrant; one motor on the Captain-side and the second motor on the First Officer-side. This enables a more streamlined build without using the traditional approach of mounting the motors on the forward firewall of the throttle quadrant.

captain-side 12 Volt motor, wiring lumen and dual string potentiometer that control thrust levers

String Potentiometers - Thrust Levers 1/2

Two Bourns dual-string potentiometers have been mounted in the aft section of the throttle unit. The two potentiometers are used to accurately calibrate the position of each thrust lever handle to a defined %N1 value. The potentiometers are also used to calibrate differential reverse thrust.

The benefit of using Bourns potentiometers is that they are designed and constructed to military specification, are very durable, and are sealed. The last point is important as sealed potentiometers will not, unlike a standard potentiometer, ingest dust and dirt. This translates to zero maintenance.

Traditionally, string potentiometers have been mounted either forward or rear of the throttle quadrant; the downside being that considerable room is needed for the operational of the strings.

In this build, the potentiometers were mounted on the floor of the throttle housing (adjacent to the motors) and the dual strings connected vertically, rather than horizontally. This allowed maximum usage of the minimal space available inside the throttle unit.

Automation, Calibration and Movement

The automation of the throttle remains as it was. However, the use of motors that generate no backlash, and the improved calibration gained from using string potentiometers, has enabled a synchronised movement of both thrust lever handles which is more consistent than previously experienced.

Reverse Thrust 1/2

Micro-buttons were used in the previous conversion to enable enable reverse thrust - reverse thrust was either on or off, and it was not possible to calibrate differential reverse thrust.

Dual string potentiometer that enables accurate calibration of thrust lever handles and enables differential thrust when reversers are engaged

In the new design, the buttons have been replaced by two string potentiometers (mentioned earlier). This enables each reverse thrust lever to be accurately calibrated to provide differential reverse thrust. Additionally, because a string potentiometer has been used, the full range of movement that the reverse thrust is capable of can be used.

The video below demonstrates differential reverse thrust using theProSim737 avionics suite. The first segment displays equal reverse thrust while the second part of the video displays differential thrust.

Incremental reverse thrust N1 displayed on eicas (ProSim737) from dual potentiometer

Calibration

To correctly position the thrust lever handles in relation to %N1, calibration is done within the ProSim737 avionics software In calibration/levers, the position of each thrust lever handle is accurately ‘registered’ by moving the tab and selecting minimum and maximum. Unfortunately, this registration is rather arbitrary in that to obtain a correct setting, to ensure that both thrust lever handles are in the same position with identical %N1 outputs, the tab control must be tweaked left or right (followed by flight testing).

When tweaked correctly, the two thrust lever handles should, when the aircraft is hand-flown (manual flight), read an identical %N1 setting with both thrust levers positioned beside each other. In automated flight the %N1 is controlled by the interface card settings (Polulu JRK cards or Alpha Quadrant cards).

Have The Changes Been Worthwhile

Comparing the new system with the old is 'chalk and cheese'.

One of the main reasons for the improvement has been the benefits had from using high-end commercial-grade components. In the previous conversion, I had used inexpensive potentiometers, unbalanced motors, and hobby-grade material. Whilst this worked, the finesse needed was not there.

One of the main shortcomings in the previous conversion, was the backlash of the motors on the thrust lever handles. When the handles were positioned in the aft position and automation was engaged, the handles would jump forward out of sync. Furthermore, calibration with any degree of accuracy was very difficult, if not impossible.

The replacement motors have completely removed this backlash, while the use of string potentiometers have enabled the position of each thrust lever handle to be finely calibrated, in so far, as each lever will creep slowly forward or aft in almost perfect harmony with the other.

An additional improvement not anticipated was with the installation of the two slipper clutches. Previously, when hand-flying there was a binding feeling felt as the thrust lever handles were moved forward or aft. Traditionally, this binding has been difficult to remove with older-style clutch systems, and in its worst case, has felt as if the thrust lever handles were attached to the ratchet of a bicycle chain.

The use of high-end slipper clutches has removed much of these feeling, and the result is a more or less smooth feeling as the thrust lever handles transition across the throttle arc.

Future Articles

Future articles will address the alterations made to the speedbrake, parking brake lever, and internal wiring, interfacing and calibration. The rotation of the stab trim wheels and movement of the stab trim indicator tabs will be discussed.

This article is one of several that pertain to the conversion of the OEM throttle quadrant. A summary page with links can be viewed here: OEM Throttle Quadrant.

Update

on 2018-04-11 01:08 by FLAPS 2 APPROACH

This article was not able to be published at an earlier time because of issues with confidentiality and potential patents. The article has been re-written (March 2018).

March 25, 2015

OEM Annunciators Replace Reproduction Korrys in Main Instrument Panel (MIP)

March 25, 2015/ Flaps 2 Approach

There can be little doubt that OEM annunciators shine far brighter than their reproduction counterparts. The korrys are lit during the lights test. OEM Flaps gauge yet to be installed

A task completed recently has been the replacement of the reproduction annunciators located on the Main Instrument Panel (MIP) with OEM annunciators.

The reason for changing to OEM annunciators was several-fold. First, anything OEM is superior to a reproduction item. Second, I wanted to reproduce the same korry annuciation lighting observed in the OEM panels in the center pedestal, fire suppression panel, and when fitted, the forward and aft overhead panels. Additionally, it was also to enable the push-to-test functionality and to provide better illuminance during daylight. Some reproduction korrys are not that bright when annunciated and are difficult to see during the day.

This post will explain the anatomy of the annunciators that are fitted to the Main Instrument Panel (MIP). It will also detail how the annunciators are wired and configured in ProSim737, and provide incite into some of the advantages and functionality that can be expected when using OEM annunciators.

The individual indexing can be observed on the top surface of the upper assembly (3 groves). To separate the two assemblies a hex screw must be used to loosen the hex screw located inside the brass-coloured circular fitting. Note that this is a new style LED korry which does not support the older incandescent bulbs

Anatomy of a Annunciator (Korry)

An annunciator is a light which is illuminated when a specific function occurs on the aircraft. Annunciators are often called by the generic name ‘Korry’, as Korry is the registered trademark used by a company called Esterline that manufactures annunciators for the aero and space industry.

There are two types of annunciators used in the Boeing aircraft, the 318 and the 319 which are either a Type 1 or Type 2 circuit.

The 318 and 319 Korrys are not interchangeable. Each Korry has a different style of bulb, differing electrical circuits, and a different method of internal attachment (captive hex screw verses two blade-style screws). The only similarity between the 318 and 319 korrys is that the hole needed to house the korry in the MIP is identical in size - .440” x .940”. The 318 Korry replaced the 319 Korry.

The circuit type refers to the electrical circuit used in the Korry. Both circuit types require a ground-controlled circuit to turn it on, however, Type 1 circuits are ground-seeking while Type 2 circuits are power-seeking. Visually (when installed to the MIP) the 318 and 319 korrys are indiscernible.

Annunciators have five parts that comprise:

(i) The lower assembly and terminals (usually four terminals in number);

(ii) The upper assembly;

(iii) The outer housing/sleeve which has a lip to allow a firm connection with the MIP;

(iv) The push-in light plate which includes the bulbs; and,

(v) The legend, which incorporates a replaceable coloured lens.

The four terminal connections on the rear of each annunciator are specific to the functionality of the unit. Each will exhibit a differing circuit dependent upon its function. Likewise, each annunciator is individually indexed to ensure that the upper assembly cannot be inadvertently mated with the incorrect lower assembly.

Annunciators typically are powered by 28 Volts, use two incandescent ‘push-in style’ bulbs, and dependent upon the korry’s function, may have a light plate coloured amber, white red or green. The legend is the name plate, and legends are usually laser engraved into the light plate to ensure ease of reading. The engraved letters are in-filled with colour to allow the printing to stand out from the light plate’s lens colour.

Specialised Korry

The Boeing 737 aircraft uses a Korry, a type 318, that is slightly different to the standard Korry. This Korry enables the functionality for the BELOW G/S – P-Inhibit function.

The Type 318 differs from other korrys used in the MIP in that it has a dry set of momentary contacts which are controlled by pressing the light plate. Pressing the illuminated light plate extinguishes the annunciator and cancels the aural ‘Below Glideslope’ caution.

Reproduction Verses Original Equipment Manufacture (OEM)

The four biggest differences between reproduction and OEM annunciators are:

(i) The ability to depress the light plate in the OEM unit for Push-To-Test function;

(ii) The ability to replicate specific functions, for example the Below G/S P-Inhibit korry;

(iii) The hue (colour) of the lens and crispness of the legend; and,

(iv) The brightness of the annunciator when illuminated (5 volts verses 28 volts).

Reproduction Korry Shortfalls

Two areas lacking in reproduction units is the brightness of the annunciator when illuminated, and poorly defined legends.

For the most part, reproductions use 5 volts to illuminate two LEDS located behind the lens. Whilst it is true that the use of LED technology minimises power consumption and heat generation, the brightness of the LEDS, especially during the day, may not be as bright as the two 28 volt incandescent bulbs used in an OEM annunciator. Moreover, 5 volts does not allow the successful use of DIM functionality.

It is unfortunate that many lower priced annunciators also lack well defined engraved lens plates making the ability to read the annunciator legend difficult at best.

Shortfalls notwithstanding, most high-end reproduction annunciators are of high quality and do the job very well.

**Table 1:** quick reference to determine the main differences between OEM and reproduction annunciators. Note that the appearance of the annunciator can alter markedly between different manufacturers of reproduction units

Installation, Interfacing and Configuration of OEM Annunciators

Replacing a reproduction annunciator with its OEM counterpart is straightforward if the Main Instrument Panel (MIP) has been produced 1:1; however, reproduction MIPs are rarely exactly 1:1 and in all probability you may need to enlarge the hole that the annunciator resides. If this is the case, ensure you use a fine-grade aluminum file and gentle abrade the hole to enlarge it. When enlarging the hole, ensure you continually check the hole size by inserting the korry – if the hole is enlarged too much, the korry will be loose and will require additional methods to secure to the MIP.

Disassembling a Korry

It is important to understand how to unassemble the annunciator.

First, the light plate has to be gently pried loose from the upper assembly. Once this is done, the upper and lower assemblies must be separated to allow the outer/sleeve to be removed. The Type 318 annunciators have a hex screw, located in the lower assembly unit, which needs to be loosened with a 5/64th hex wrench to allow separation, while the Type 319 annunciators are secured by two standard screws that require a small blade screwdriver.

Once the two parts are separated, it should be noted that the upper assembly has a flange at the forward end; this flange enables the annunciator to be firmly connected to the MIP.

Attaching a Korry to the MIP

Is your MIP 1:1 and will it fit OEM korrys without further to do? Click the diagram to see the dimensions of korrys (with thanks to Mongoose for diagram)

Insert the upper assembly into the MIP flange facing forward. Next, slide the housing over the rear of the mechanism from the rear of the MIP. Rejoin the lower section and tighten the hex screw. If the MIP is 1:1, the annunciator should now be firmly secured to the MIP wall. The light plate can now be pushed into the mechanism.

If the annunciator does not fit firmly into the MIP, it can be secured by using silastic or a glue/metal compound. (I do not recommend this. It is best to ensure the hole is the correct size or a tad too small. This will guarantee that the annunciator will have a firm fit).

Provided the mechanism is not faulty or does not break, the chance that it will need to remove it is very remote. If the bulbs fail, they are easily replaced as they are contained within the light plate.

Wiring - Procedure

Wiring the MIP annunciators is a convoluted and repetitious process that involves daisy-chaining the various annunciators together. Because wiring is to and from four terminals, it can be difficult to remember which wire goes where. As such, it is recommended to use coloured wire, label each wire and keep meticulous notes.

Each annunciator has four terminals located on the rear of the unit that corresponds to:

(i) Positive (28 volts);

(ii) Logic for the function of the korry;

(iii) Lights test; and,

(iv) Push-To-Test.

To crosscheck the above, each Type 2 korry has a circuit diagram stenciled on the side of the assembly.

**Figure 1:** A schematic of the three types of korrys used in the Boeing 737. The left diagram is from the 318 push to inhibit korry (diagram copyright David C. Allen

For the OEM korrys to function correctly, they need to be connected with an interface card (I/O card). An example of such a card is a Phidget 0/16/16 card.

(i) Designate the annunciator closest the I/O card and power supply as the lead annunciator (alpha).

(ii) Terminal 1 and Terminal 4 are the power terminals for each korry. Connect to the alpha korry the positive wire from the 28 Volt power supply to terminal 1 and the 28 Volt negative wire to terminal 4. The wires from these two terminals are then daisy-chained to the identical terminals on the other korrys in the system.

(iii) Terminal 2 controls the logic behind the function for each korry. A wire must connect from terminal 2 of each korry to the output side of the I/O card. To close the loop in the I/O card, a wire is placed from 28 Volts negative to the ground terminal on the card (input).

(iv) Terminal 3 controls the logic behind the light test toggle. A wire is daisy-chained from terminal 3 of the alpha korry to all other korrys in the system. A wire is then extended from the final korry to the lights test toggle switch. This switch has been discussed in detail in a separate post.

Quite a bit of wire will be needed to connect the thirteen or more annunciators and it is a good idea to try and keep the wire neat and tidy by using a lumen to secure it to the rear of the MIP.

Mounting and Brackets

Every simulator design is different, and what is suitable for one set-up may not be applicable to another.

The I/O card that is used to control the MIP annunciators is mounted within the System Interface Module (SIM ). To this a straight-through cable is securely attached that connects to a D-Sub connector mounted on an aluminum bracket. The bracket and two terminal blocks are strategically mounted on the rear of the MIP and enable the various wires from the korrys to connect with the straight-through cable.

Interfacing and Configuration Using ProSim737

To interface the annunciators, follow the directions on how to wire your I/O card.

This article provides information on the Phidget 21 Manager (software) and how a Phidget interface card is used.

Using Interface cards and Canon Plugs to Convert OEM 737 Parts .

If the annunciators have been correctly daisy-chained together, only the wires from terminal 2 of each korry will need to be connected to Phidget card. When power is applied, the Phidgets software will automatically assign outputs to any device (korry) attached to the 0/16/16 card.

To determine the digital output number for each annunciator, open the Phidgets 21 Manager, push the light plate on a chosen annunciator and record the allocated output number. The output numbers are used by ProSim737 to allocate that annunciator to a specific software command line.

Configuring the MIP annunciators in ProSim737 is a two-step process. First, the annunciator must be assigned as a switch (for the puhs- to-test function to operate), then as an indicator (for the annunciator to illuminate). Before commencing, check that Phidgets have been assigned in the driver section of the configuration section of the main ProSim737 menu.

Open the configuration screen and select switches and scroll downwards until you find the appropriate switch that corresponds to the annunciator. Assign this switch to the output number assigned by the Phidgets software (If you have multiple Phidget cards installed ensure the correct card is assigned).

After this has been completed, continue the configuration process by assigning each annunciator to the appropriate indicator in the configuration/indicators section.

Lights Test

A lights test is used to determine whether all the annunciators are operating correctly. A lights test can be accomplished two ways.

The first method is to press the light plate of an annunciator which operates a momentary switch that causes the light to illuminate (push-to-test). This is an ideal way to determine if an individual annunciator is working correctly.

The second method is to use the MIP toggle switch. Engaging the toggle switch to the on position will illuminate all the annunciators that are connected to the toggle switch. This is an excellent way to ensure all the annunciators are operational and is standard practice before beginning a flight.

It should be noted that for all the annunciators to illuminate, each korry must be connected to the toggle switch.

An earlier post explained the conversion and use of a OEM Lights Test Toggle Switch.

The fire suppression panel annunciators are also korrys. Like their MIP sisters, the korrys are very bright when illuminated as they are powered by 28 volts

Korry Systems

This post has discussed the main annunciators on the MIP which is but one system. Other systems include the annunciators for the forward and aft overhead annunciators, fire suppression panel and several other panels.

To connect additional systems to the enable a full lights test to be done, an OEM aircraft high amperage relay can be used.

OEM multi-relay device. The relay from a Boeing aircraft is not necessary; any aircraft relay will suffice. It's wise to choose a relay that has multiple connection posts as this will enable different systems to be connected to the relay. The relay is easily fitted to the rear of the MIP or to the inside of the center pedesta

Depending upon the type of relay device used (there are several types), it may be possible to connect up to three systems to the one relay. This is made possible by the OEM toggle switches unique multi-segment system, and the ability of the relay to handle high amperage from multiple aircraft systems.

A benefit of using an OEM relay is that it provides a central point for all wires from the various systems to attach, before connecting to the lights test toggle switch. Note that 28 volts bmust be connected directly to the relay for correct operation.

The relay will, depending upon the throw of the toggle switch (lights test), open or close the circuit of the relay. Opening rhe relay circuit (when the light test toggle is thrown) enables 28 volts to flow through the relay and illuminate any annunciators connected to the system.

Availability

The Korrys originally were used in British Airways 737-400 Airframe 25843 G-DOCM (copyright Aero icarus)

Fortunately, apart from a few functions, there is little difference between older style annunciators used in the classic series airframes and those used in the Next Generation aircraft - an annunciator is an annunciator no matter from what airframe (100 series, Classic or Next Generation).

Annunciators are relatively common and are often found ion e-Bay. However, to acquire a complete collection that is NG compliant can be time consuming, unless a complete panel is purchased and the annunciators removed.

Lineage

The annunciators used in the simulator came from a B737-400 airframe. This aircraft - serial number N843BB and construction number 25843 had a rather interesting lineage.

It began service life in March 1992 with British Airways as G-DOCM before being transferred to Fly Dubai and Air One in 2004. Late 2004 the airframe was purchased by Ryan International and the registration changed to N843BB. Between 2005 and 2010 the aircraft was leased to the Sundowner LCC who at the time was contracted to the US Dept. of Justice. The aircraft was returned to Ryan International mid 2010 and subsequently scrapped.

Acronyms

OEM - Original Equipment Manufacturer (aka real B737 aircraft part)

March 14, 2015

New Interface Modules

March 14, 2015/ Flaps 2 Approach

My friend and I have not been sitting idle. Part of the upgrade to the simulator has been additional interface modules.

In early 2014, an Interface Master Module (IMM) was constructed to trial the modular concept. This module housed most of the interface cards and relays that, at the time, were used in the simulator. This trail was successful. The single trial IMM has now been discarded and has been replaced with the:

Throttle Interface Module (TIM);
Throttle Communication Module (TCM);
System Interface Module (SIM SMART); and,
A more advanced Interface Alert System (IAS) that connects to the TIM and a lesser degree the TCM.

Information concerning each of these modules, including an introduction to the modular concept, can be found in a new section named Interface Modules. Interface Modules can be assessed from the main menu tabs located at the top of each website page (the brown banner).

It has taken considerable time to design and construct, and then interface these modules to the simulator. To some, the process may appear complex and convoluted. However, in the long term the idea is sound and a centralized area offers considerable advantages.

I hope you enjoy reading about the new modular systems.

March 02, 2015

Throttle Quadrant Rebuild - Evolution Has Led to Major Alterations

March 02, 2015/ Flaps 2 Approach

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.

This article is one of several that discusses the conversion of the OEM Throttle Quadrant.

February 17, 2015

Autobrake System - Review and Procedures

February 17, 2015/ Flaps 2 Approach

air berlin 737-700 - autobrake set, flaps 30, spoilers deployed, reverse thrust engaged (Marcela, GFDL 1.2 www.gnu.org/licenses/old-licenses/fdl-1.2.html, via Wikimedia Commons)

The autobrake, the components which are located on center panel of the Main Instrument Panel (MIP), is designed as a deceleration aid to slow an aircraft on landing. The system uses pressure, generated from the hydraulic system B, to provide deceleration for pre-selected deceleration rates and for rejected takeoff (RTO). An earlier post discussed Rejected Takeoff procedures. This article will discuss the autobrake system.

General

The autobrake selector knob (rotary switch) has four settings: RTO (rejected takeoff), 1, 2, 3 and MAX (maximum). Settings 1, 2 and 3 and RTO can be armed by turning the selector; but, MAX can only be set by simultaneously pulling the selector knob outwards and turning to the right; this is a safety feature to eliminate the chance that the selector is set to MAX accidentally.

When the selector knob is turned, the system will do an automatic self-test. If the test is not successful and a problem is encountered, the auto brake disarm light will illuminate amber.

The autobrake can be disengaged by turning it to OFF, by activating the toe brakes, or by advancing the throttles; which deactivation method used depends upon the circumstances and pilot discretion. Furthermore, the deceleration level can be changed prior to, or after touchdown by moving the autobrake selector knob to any setting other than OFF. During the landing, the pressure applied to the brakes will alter depending upon other controls employed to assist in deceleration, such as thrust reversers and spoilers.

The numerals 1, 2, 3 and MAX provide an indication to the severity of braking that will be applied when the aircraft lands (assuming the autobrake is set).

In general, setting 1 and 2 are the norm with 3 being used for wet runways or very short runways. MAX is very rarely used and when activated the braking potential is similar to that of a rejected take off; passenger comfort is jeopardized and it is common for passenger items sitting on the cabin floor to move forward during a MAX braking operation. If a runway is very long and environmental conditions good, then a pilot may decide to not use autobrakes favouring manual braking.

Often, but not always, the airline will have a policy to what level of braking can or cannot be used; this is to either minimize aircraft wear and tear and/or to facilitate passenger comfort.

The pressure in PSI applied to the autobrake and the applicable deceleration is as follows:

Autobrake setting 1 - 1250 PSI equates to 4 ft per second squared.
Autobrake setting 2 - 1500 PSI equates to 5 ft per second squared.
Autobrake setting 3 - 2000 PSI equates to 7.2 ft per second squared.
Autobrake setting MAX and RTO - 3000 PSI equates to 14 ft per second (above 80 knots) and 12 ft per second squared (below 80 knots).

Conditions

To autobrake will engage upon landing, when the following conditions are met:

The appropriate setting on the auto brake selector knob (1, 2, 3 or MAX) is set;
The throttle thrust levers are in the idle position immediately prior to touchdown; and,
The main wheels spin-up.

If the autobrake has not been selected before landing, it can still be engaged after touchdown, providing the aircraft has not decelerated below 60 knots. Setting the autobrake usually forms part of the approach cehcklist.

To disengage the autobrake system, any one of the following conditions must be met:

The autobrake selector knob is turned to OFF (autobrake disarm annunciator will not illuminate);
The speed brake lever is moved to the down detent position;
The thrust levers are advanced from idle to forward thrust (except during the first 3 seconds of landing); or,
Either pilot applies manual braking.

The last three points (2, 3 and 4) will cause the autobrake disarm annunciator to illuminate for 2 seconds before extinguishing.

Important Facet

It is important to grasp that the 737 NG does not use the maximum braking power for a particular setting (maximum pressure), but rather the maximum programmed deceleration rate (predetermined deceleration rate). Maximum pressure can only be achieved by fully depressing the brake pedals or during an RTO operation. Therefore, each setting (other than full manual braking and RTO) will produce a predetermined deceleration rate, independent of aircraft weight, runway length, type, slope and environmental conditions.

Autobrake Disarm Annunciator

The autobrake disarm annunciator is coloured amber and illuminates momentarily when the following conditions are met:

Self-test when RTO is selected on the ground;
A malfunction of the system (annunciator remains illuminated - takeoff prohibited);
Disarming the system by manual braking;
Disarming the system by moving the speed brake lever from the UP position to the DOWN detente position; and,
If a landing is made with the selector knob set to RTO (not cycled through off after takeoff). (If this occurs, the autobrakes are not armed and will not engage. The autobrake annunciator remains illuminated amber).

The annunciator will extinguish in the following conditions:

Autobrake logic is satisfied and autobrakes are in armed mode; and,
Thrust levers are advanced after the aircraft has landed, or during an RTO operation. (There is a 3 second delay before the annunciator extinguishes after the aircraft has landed).

Preferences for Use of Autobrakes and Anti-skid

When conditions are less than ideal (shorter and wet runways, crosswinds), many flight crews prefer to use the autobrake rather than use manual braking, and devote their attention to the use of rudder for directional control. As one B737 pilot stated - ‘The machine does the braking and I maintain directional control’.

Anti-skid automatically activates during all autobraking operations and is designed to give maximum efficiency to the brakes, preventing brakes from stopping the rotation of the wheel, thereby ensuring maximum braking efficiency. Anti-skid operates in a similar fashion to the braking on a modern automobile.

Anti-skid is not simulated in FSX/FS10 or in ProSim737 (at the time of writing).

To read about converting an OEM Autobrake.