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Mission Statement 

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

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


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

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


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

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

Journal Archive (Newest First)

Entries in B737-800 Flight Simulator (45)


Replacement Curtains - B737 OEM Throttle Dust Curtains

Interesting items can arrive in the post.  Earlier today I opened a small parcel to find a collection of grey coloured pieces of material.  To anyone else they would appear exactly as they do – pieces of material stamped with numbers.

LEFT:  OEM dust covers for the Boeing throttle.

The throttle quadrant I use is original equipment manufacture (OEM) and once plied the skies above Europe.  As such it is a used item with the usual wear and tear you expect from a well-used aircraft part. 

One item that continually caught my attention was the dust curtains or skirts that sit behind the two thrust levers.  In my throttle, the curtains had been abused at some point and were torn and the edges looked rather ragged in appearance.  Although a replacement curtain could have been made by using vinyl or another similar material it would not be the same. 

The numbered pieces of material now have a home – they are OEM dust curtains that will replace the damaged curtains on the throttle.

Installing the Dust Curtains

The B737 throttle quadrant has three dust curtains.  Two on the outer side of the thrust levers and one double-sided curtain that resides between the thrust levers.  Each curtain comprises three parts sandwiched together and held by three screws. 

The parts are:

(i)     The thin aluminium arc which is the outer face plate;
(ii)    The actual curtain; and,
(iii)   The plastic arc retainer. 

The plastic arc retainer is curve-shaped and sits flush against the bare metal of the quadrant.  The dust curtain then lies above the retainer and beneath the outer face plate.

LEFT:  Dust curtains have been removed and the plastic retainer and aluminium arc can be seen along with one of the three attachment screws (click to enlarge).

Replacing the curtains is straightforward. Remove the three screws that hold the metal arc in place to the throttle, then gentle pry loose the aluminium strip beneath which are the dust curtain and plastic arc retainer.  It’s wise to ensure that you place the parts anatomically on the workbench as each of the items must be reassembled the same way it was removed.

One aspect of Boeing philosophy which makes building a flight simulator much easier is their reuse of parts from earlier airframes.  Boeing do not always redesign a part from scratch, but add to or change existing parts.  This philosophy can save the company millions of dollars.

For those who study this type of thing, you will know that dust curtains can come in differing colour shades.  In general, the older classic style throttle used a paler grey/cream coloured skirt whilst the Next Generation airframes use a standard light grey colour.  But, I would not get too concerned if the colour does not exactly match.

Why are the Dust Curtains Important

The main purpose of the dust curtainsis to minimise the chance of foreign bodies falling into the throttle mechanism.  Think pens, rubbers, straws, paper clips and coke can pull tabs (or anything else pilots play with in the flight deck).  The dust curtains are made from a fire retardant material (not asbestos) which minimises the chance of any fire/sparks from licking up the sides of the thrust levers in the unlikely event that a fire devlops inside the throttle quadrant.

For those keen to find replacement OEM dust curtains the stock numbers are: 69-33918-8 REF, 69-33918-9 REF-F and 69-33918-10 REF-F.


Anatomically – Meaning items removed are placed on a table in the same position as they were when they were in place.
Curtain Arc – the semi circular arc that the dust curtains are attached to.
OEM – Original Equipment Manufacture (aka real aircraft part).
Plastic Arc Retainer – A piece of heavy duty plastic shaped as a curve (arc).


Protection for Interface Cards - USB Isolator

In the first of two previous posts we discussed surge protectors and the need for a protector to secure your simulator system from unwanted power surges.  The second post addressed circuit breakers in more detail and examined the different types of breakers that can be used.  In this final post I will discuss the use of an isolator to protect both your computer and any USB connected interface cards.

LEFT:  Phidget 3060 USB Isolator mounted on arcylic base (click to enlarge).

Multiple Phidget Card Failure

Recently I had to replace several Phidget interface cards.  The cards failed following failure of the internal power supply on my server computer.  The reason for the power supply failure is unknown, however for whatever reason a surge travelled through the USB port to the SMART module irreparably damaging two Phidget 0/16/16 cards and two Phidget 1066 motor controllers.

I contacted Phidgets in Canada who were very helpful in diagnosing the reason for the card failure.  Apparently it is not unheard of for powered Phidget cards to cease working following the failure of a computer power supply that Phidget cards are attached.

Potential Problem

The discussion with the technician highlighted a potential problem that Phidget cards are susceptible to.

When the internal computer power supply (CPS) fails the circuits are no longer fully operational which may cause unregulated power to briefly travel the shortest route to leave the system.  PCI cards and USB ports are for the most part totally unprotected and act as a first port of call for any unwanted transient power.  The power then travels through the connected USB cable to whatever is attached.  Although the surge (I will call it a surge) may only be a millisecond, it is enough to fatally damage or shorten the life of an attached interface card.  

Bear in mind that not every instance of a power supply failure will result in a surge; it depends on how the power supply failed.  In my case, when the power supply failed 5 volts continued to be distributed.  However, I believe the 5 volts was not clean power meaning that the voltage fluctuated.

The technician commented that it is relatively uncommon for the event described above to occur.  He suggested that a far more common issue is that, following the failure of a powered Phidget card, the unregulated power travels to the computer via the connected USB cable (the opposite direction to what happened in my situation).  In these circumstances, the USB port, PCI card, internal computer power supply, or worse still – the computer’s motherboard can be destroyed.

For a more detailed explanation with examples, I refer you to the Phidget website.

The Solution

Fortunately there is an easy solution to this potential problem – the Phidgets 3060 USB isolator.  

The isolator is connected between the USB port and the interface cards.  In this way the cards are protected from the computer and the computer is protected from the cards, wiring and external power supplies used to power the cards.

LEFT:  Phidget 3060 isolator – the size of a credit card, the isolator can provide protection for both the computer and the interface cards that are connected to it.  This isolator is installed into the SMART module and provides protection for the two 0/16/16 cards and two 1066 motor controllers (click to enlarge).

The 3060 isolator is a tad smaller than the standard-sized credit card and does not require a power supply.  The isolator has two USB connections, one side has a mini and the other side a standard connection.  This enables in-line connection of the isolator between the computer’s USB port and interface card/power hub.

LEFT:  The 3060 isolator installed into the Throttle Interface Module (TIM).  The isolator has been installed into an acrylic casing.  Although the casing is by no means necessary, it ensures that the isolator card does not become contaminated by dust.  The blue-coloured plastic band is temporary only (click to enlarge).

In addition to the protection already mentioned, the isolator also protects against possible basic wiring errors and different ground voltages.  In some circumstances the isolator can also assist to stabilise a system form untimely USB disconnects.  The isolator achieves this by maintaining the correct voltage.

The interface cards used in the simulator have been mounted in standalone interface modules that in turn connect via USB to the server computer.  To protect the contents of each module, a 3060 isolator has been installed into each interface module.

Computer Power Supplies (CPS)

Although this problem was easily solved by purchasing replacement interface cards and installing isolators, it should not have occurred in the first place and it brings into question the reliability and quality of computer power supplies.

The choice of a CPS is often by chance, being the unit supplied with the computer (probably a inexpensive Chinese model).  However, CPS’s are not identical and you get what you pay for.  

Many manufactures claim a specific output/voltage/wattage from their power supplies, however only a few manufactures check and guarantee these outputs.  The last thing you want is a power supply that has fluctuating voltage or a unit that is rated a particular output but does not meet this requirement.  

The CPS installed in the server computer was not a quality item (it came with the computer and was not upgraded despite the remainder of the computer being re-built to flight simulator specifications).  For a few months I had noted that the CPS appeared to be running quite warm.  In hindsight, I should have realized the tell-tail symptoms of an impending problem.  

The failed CPS has been replaced with a Corsair RM750x Power Supply.  This particular model is used when tight voltage control is needed.  

Other benefits of using a Corsair CPS is that the capacitors are Japanese made and provide consistent and reliable output.  Furthermore, Corsair bench check every unit to ensure that they meet the outputs published.

Final Call

It is your call whether the expenditure and use of a USB isolator is warranted.  Certainly replacing Phidget cards can be expensive, not too mention the time required to install and rewire.  The isolator should be viewed as a type of insurance policy  - a 'just in case' option.

Further Information

NOTE: The isolator is designed by Phidgets primarily to operate with powered Phidget cards.   The interface modules I use have Phidget, PoKeys and Leo Bodnar cards installed and connecting an isolator did not cause any issues with the operation of these cards.

I do not know if the isolator will cause problems with other USB standalone modules.

This post is but a primer.  For additional information, refer to the Phidgets website.  Note I am not affiliated with Phidgets in anyway.


CPS – Computer Power Supply.
PCI Card – Computer bus for connecting various hardware devices.


Circuit Breakers For Self Preservation

Following on in the same theme as my earlier post 'Are You Protected - Power Surges', we discuss in more detail the various circuit breakers that can be used in a simulator setting.  Additionally, it is stressed that electricity can kill and a qualified electrician should be contacted prior to implementing anything suggested below.

LEFT:  Selection of Eaton Memshield MCB circuit breakers. 

My thanks to Dave Egkkman (flight simulator enthusiast based in the United Kingdom) who has written this article.  I think the content adds considerably to my earlier post and I am grateful to Dave for writing and allowing it to be posted here.

Circuit Breakers and Fuses 

It is a common misconception that fuses and circuit breakers are there for personnel protection. It is very important to understand that this is not the case.

It can take as little as 0.03A to kill a human being, that’s 30mA! So, if you have a circuit protected by a 30A fuse/circuit breaker, it will allow 1000 times more current to flow than it takes to kill, before it breaks the circuit and stops the current flow.

Fuses and circuit breakers (protective devices) are there to protect the cabling in an electrical circuit from damage by overload. This is achieved by installing a suitably rated circuit breaker at the beginning of a circuit. The rating of the protective device will be calculated to protect the lowest rated cable in the circuit, by stopping the flow of current in an overload situation before the current flow exceeds the current rating of the cable.

A common scenario in the UK is the use of 13A fuses in plugs. In domestic plugs in UK, the plug can take a variety of fuses rated from 1A to 13A. Often loose plugs are supplied fitted with a 13A fuse or, if a fuse ‘blows’ the user will commonly fit a 13A fuse as a replacement. However, if the appliance is a lamp standard, the cable from the plug to the electrical appliance could be rated at 6A or less.

So, in the event of a fault developing that allows 10A to flow, the fuse will not break the circuit, but the cable could well overheat and catch fire, and still the fuse may not break the circuit.


A fuse is simply a piece of small wire designed to melt and break the circuit if more current flows than the fuse wire is designed to allow to flow.

In some cases, faults can occur in which the current may not be large enough to melt the fuse but enough to seriously harm the user of the electrical appliance. Circuit breakers generally offer better protection

Circuit Breakers

For domestic installations there are three main types of circuit-breakers.

1.         Miniature Circuit Breaker (MCB)

2.         Residual Current Circuit Breaker (RCCB) or Residual Current Device (RCD).

3.         Residual Circuit Breaker with overload (RCBO)

Miniature Circuit Breaker (MCB)

The MCB is a protective device typically used where a fuse would have been. MCBs are quicker to respond than fuses, are more reliable, more sensitive and can be reset once the fault has been cleared, the problem identified and fixed.

LEFT:  Protec 63A 363-2C-6kA Triple Pole MCB circuit breaker.

There are many different configurations of MCBs, which we won’t go into here. We should however consider the three different ‘Types’ that are available. All 3 MCB types use a magnetic fault protection, which trips the MCB within one tenth of a second when the overload reaches a set level.

How a MCB Works

Basically, the live input cable is wound around an iron core. As current flows a magnetic Field is generated. If the magnetic field reaches a pre-set level, an iron latch is pulled towards the iron core (magnet) and breaks the circuit.

In normal domestic use a Type B MCB will be used. A Type B breaker will trip between 3 and 5 times full load current.

For electrical loads that have a high inrush current when they are switched on, a Type B breaker is likely to trip as it ‘sees’ the inrush current as an overload.

A Type C breaker trips between 5 and 10 times full load current. This allows the MCB to withstand the initial inrush current, whilst still providing overload protection in normal use.

A Type D breaker trips between 10 and 20 times full load current, typically used where high inductive loads are present such as motors and transformers.

For those with problems of an MCB (or a fuse) tripping when turning on equipment, a Type C breaker may be the answer. Selecting the correct Type and rating of breaker is not an arbitrary decision. An electrically qualified person should make this decision.

Whichever MCB type is used, it is extremely dangerous to cut corners by using inferior quality devices, therefore they should only be bought from a reputable supplier. Copy and cheap MCBs have been found to have no copper/nickel/silver contacts within them, just steel. Upon introducing a fault, the contacts simply weld together, the consequences are obvious. Don’t go cheap.

Residual Current Device

A residual current device IS designed to offer personnel protection. RCDs are used in combination with fuses and MCBs.

LEFT:  ETI 25A 30mA RCD 2 throw circuit breaker.

Residual current circuit breakers work by comparing the current entering the appliance via the live input with the current leaving the appliance through the neutral.

How a RCD Works

The live wire and neutral wire within the device, are wound around iron cores in opposite directions. When the appliance is working correctly ALL the electrical current entering the appliance via the live wire, exits the appliance through the neutral wire. The magnetic fields generated around the iron cores cancel out.

In the event of a fault some of the electric current will flow through the earth wire, casing of the appliance or in the absence of proper earthing through the body of the user. This results in an imbalance between the current entering the appliance through the live wire and the current exiting through the neutral wire.

This difference in electrical current is called the residual current and it is what causes the device to break the circuit.

Residual Current Circuit Breakers have the advantage of being highly sensitive with a very quick response time.

There are various ratings of RCDs. Typically, in domestic use a 30mA RCD will be used, but 10mA is also common. Selecting the correct Type and rating of RCD is not an arbitrary decision. A qualified person should make this decision.

It is not unusual for people to complain that RCDs suffer from nuisance tripping. If an RCD is tripping there is a problem, the problem should be identified and corrected. If an upstream RCD is tripping, rather than the local RCD, for example the RCD in the house trips and the one in the out building does not, then the configuration of the circuit is incorrect. These issues should be addressed by, yes you guessed it, a suitably electrically qualified person. Issues of disconnection times, voltage drop, resistance of the earth path all need to be considered.

Residual Circuit Breaker with overload

A residual circuit breaker with overload (RCBO) protection is a device that combines overload and personnel protection.

They are often used where there is not enough space for an MCB and RCD in one consumer unit / fuse board.


This information is provided to offer guidance only and hopefully to suggest when an electrically qualified person should be approached for guidance. It is not comprehensive and only scrapes the surface of the subject of electrical protection.

I don’t want to come across as ‘holier than thou’ but, I really don't wish to be drawn into offering guidance to people about which and what protective devices should be used for their particular installation. I don't even agree with DIY companies selling fuse boards, MCBs etc. I'm hoping my words will encourage folks to seek professional advice from a local engineer/electrician who can assess their own situation. It's not the same as deciding which interface card to use for TQ servo activation!

All electrical work must be carried out by a qualified engineer/electrician and this post is not suggesting otherwise.


A - Amp
mA - Milliamp


Are You Protected - Power Surges 

The power requirement, or more to the point the regulation of the power is often overlooked when building a functional flight deck. 

A basic desktop-style simulator controlled by a single computer and displayed on two computer monitors will draw very little power and can easily be connected to a single household wall socket.  However, as a simulator build becomes more complex and incorporates multi-displays and various other pieces of equipment the power requirements become more complex.  

In this post, I will discuss the basics surrounding the distribution of power, in particular amperage draw.  I will also address the need for surge protection. 

This post is an introduction into the somewhat confusing and complicating world of electricity and power quality; it is not intended to be a definitive work.

Amperage Draw

The biggest issue with many simulators is amperage draw, with many builds drawing close to, if not over 10 amps.  Drawing in excess of 10 amps can cause a standard household circuit breaker (or fuse) to be triggered cutting off the electricity supply to the simulator.

Although a power shut down from the triggering of a circuit breaker can be annoying, especially if part way through a simulator flight, a bigger problem is that many interface cards including Phidget cards may lose important configuration and calibration parameters if they are ‘murdered1by a power shutdown.

Amperage Draw, Circuit Breakers and Zones

The power distribution in a modern house is distributed into zones (circuits).  

A zone will have any number of power points attached to it, and will be protected by a dedicated circuit breaker of specific amperage.  For example, water and heat is one zone, while lighting and power points can be spread across one, two or more zones (depending on the number of lights and their respective amperage draw). 

In Australia, all standard household power points (except heat and water) are rated at 10 amps while the wire that runs from the power point to the circuit board is rated at a higher capacity; usually 15 amps.  

If the power requirements exceed 10 amps within a zone, then the circuit breaker on the circuit board will be triggered and the electricity will cease to flow into that zone.

Many will be accustomed to this inconvenience, when they have a number of heaters plugged into various power points within one zone.  Turning on the kettle to boil water, will then be enough to exceed the power amperage for that zone and the circuit breaker will be triggered.

  • My next post will take a more detailed look at circuit breakers and the types that can be used in various situations, so more more on this later.

Amperage Draw and Heat

An easy method to enable a greater amperage draw is to replace the 10 amp circuit breaker with one rated at a higher capacity.  This will alleviate the situation of the circuit being tripped every time you exceed 10 amps.  Whilst this is feasible, after all the wire running between the board and the power point is 15 amps, it is not recommended.  

A by-product of drawing too many amps along one wire is heat, and although the wire may be rated at 15 amps, the heat may cause electrical wrapping to begin to melt.  Furthermore, if the amperage draw is maintained the power point may begin to melt and burn due to the exceeded amperage draw.

Calculating Amperage Draw

Calculating the amperage draw can be complicated as equipment can draw different amperages at different times.  For example, a computer when turned on will initially draw more amperage; however, this draw will lower after the initial start cycle has been completed.  

LEFT:  Amperage draw and status can be measured if an appropriate gauge is installed and the wiring connected correctly.  The gauges in the picture are measuring amperage status of different sectors (5  & 12 volt sectors) in the Throttle Interface Module.

Often, you can cause an over-amperage draw and trigger a circuit breaker by starting everything simultaneously.  However, by starting different systems sequentially you can keep the amperage draw to a minimum and below the 10 amp rating of the circuit breaker.

Upgrading the Amperage

If the simulator (or any number of electrical appliances) draws more than 10 amps, and the circuit breaker continuously is triggered, there are two methods in which to solve the problem.  

First, is to have an electrician replace the wire for the zone that the simulator is connected to.  This involves replacing the 10 amp power point with a power point rated at 15 amps, running higher capacity wire between the power point and circuit breaker, and using a higher amperage circuit breaker in the circuit board.  A 15 amp power point also incorporates a larger blade assembly (earth) on the plug..

The second method is to spread the power requirements over two or more zones.  This way, if the simulator operates across two 10 amp zones you will have 20 amps of power available.

The downside of the second method is that you will need to have power points in close proximity to each other that connect to two zones; otherwise, an extension cable may need to be run between the simulator and the designated power point.

Power Surges, Noise and Clean Power

Unfortunately, power is not clean and everyone will experience at sometime or another voltage fluctuations (power surges).  The severity and frequency of the fluctuations will depend  upon the ability of the power grid to obtain, store and distribute power.  

LEFT: Sine wave data read-out showing the tell-tail spike  of a power surge.

The power requirements of a large industrial complex powering on in the morning maybe enough to cause a fluctuation (surge) as it draws initial power from the grid.  Furthermore, surges in power can often occur when the electrical company adjusts the grid to take into account the day and night-time power requirements of the surrounding region.  

Whilst these are standard day to day activities, a major disruption in power, with resultant surges and spikes, can occur during severe storm events.  During such events, power disruptions can be common as poles and wires are damaged due to high wind and torrential rain.  In the most extreme case, an electrical discharge from lightening can occur directly on your home or in an area nearby.  If your house is struck by lightning, then there is very high chance that permanent damage will result to any plugged in equipment.

Is this problematic – yes and no.  An odd low level minor surge will probably not cause too much grief; however, a high volume power surge or a constant surge can damage equipment.  

A high-end simulator usually incorporates numerous interface cards, system boards and other delicate components which, more often than not, are not amiable to power surges.  

A high volume or constant power surge may destroy the motherboard, power supply and USB PCI cards in the computer, in addition to destroying interface cards attached to the computer.  However, minor power surges may not enlist any observable damage (other than the lights flickering or dimming briefly), but they may shorten the effective life of attached components leading to premature burnout.

Surge Protection and How It Works

There are several pieces of equipment that can be used to protect electronic equipment; the most common being a surge protector board.  

LEFT:  Six plug power surge protection board with internal circuit breaker manufactured by Belkin.  Two LED lights indicate on/off and earth leakage while the circular black pop out switch is a standard-type circuit breaker.  The Belkin is probably one of the more popular boards and provides average protection with a rating of around 600 Joules (depends on model) (click to enlarge).

In essence, a surge protector board is a glorified power board with some type of mechanical mechanism that is either destroyed or partly destroyed when a power surge occurs.  Higher end protectors may also provide noise filtering and a internal circuit breaker.

The level of protection provided by a surge protector is, at its bare minimum, determined by the level of Joules the board is rated at.    Joules (J) is a derived unit of energy as defined by the International System of Units and should be thought of as a reservoir of protection.  

Simply put, a board rated with a high number of Joules has a larger reservoir and therefore provides greater protection for a longer period of time.   For example, if a board is rated at 525 Joules, the board will provide protection for either one power surge rated at 525 Joules or any number of smaller power surges below 525 Joules until the rating is exceeded.  

The design of the board is such that once the level of protection (Joules) has been exceeded, the board will need to be replaced.  

Many minor power surges go completely unnoticed, and although you did not notice the surge, the surge protector will have filtered the power imbalance and lost a portion of its own protection (Joule reservoir).  This can lead to a false sense of security as many protector boards will still function, albeit without any form of available protection.  Inexpensive surge protectors often do not have any type of indicator to warn when their Joule reservoir is about to, or has been exceeded.

Re-set Buttons

Many surge protector and extension boards have a reset button.  The reset button has nothing to do with surge protection or resetting the board after a power surge has occurred.  Rather, the button is the reset for the circuit breaker which is for protection against a short circuit or over-load condition that could otherwise cause the wiring to melt with the board.

Main Types Of Power Surge

The following is an excerpt from Electrosafe, a company based in New Zealand.


This is where a portion of the sine wave has a lower than expected value or is missing entirely, usually for a portion of a cycle. These types of problems can be caused when large motors are started, spot welders are operated, lightning arresters conduct (during a lightning hit), or when electrical equipment fails. Dropouts can lead to failures in computers and electronic equipment, reduced life of motors and flickering lights.

Power Failure

When the duration of a dropout exceeds 1 cycle it is usually referred to as a power failure, or blackout. This problem is usually the easiest to recognise.

Sag or Brownout

A power sag (or low line voltage) is a decrease in line voltage of at least 10% of the average line voltage for half a cycle or longer. The power sag is often caused by large inductive equipment, e.g. photocopy, bank of fluorescent lights.  Sags can be caused by external factors as well, such as large power draining equipment used in other buildings.

Sags can be particularly detrimental to electronic equipment because of the malfunctions caused by the sudden decrease of available voltage to the power supply. Relays and solenoids can chatter generating spikes. Complete failure rarely occurs, however equipment lockup or lockout can occur requiring a resetting process.

Often equipment continues to operate, with the user, unaware of any problems that may have occurred.


A power surge is the opposite of a sag and is often referred to as ‘High Line Voltage’.   A surge is defined as an increase in line voltage above 253 volts (on a 230V Line) for a half cycle or longer. Like the sag, the power surge is often caused by large inductive loads being applied on the same line. Power surges can cause some of the most dangerous situations, and their resulting damage is most difficult to repair.

Direct Relationship

There is a direct relationship between the amount of protection provided, the cost for that level of protection, and the price it is to replace the items destroyed.  Furthermore, there is a convenience factor.  How easy is it to replace and rewire the damaged component verses the cost of protection.

Almost 'Spiritual' Protection

Some manufacturers of surge protectors often claim almost ‘spiritual’ protection; however, not every board is identical in the level of protection offered.

LEFT:  A generic extension board featuring back lit on/off button and a red LED, that when illuminated, instils confidence in the words 'surge protected'.  This particular board does not have any form of surge protection and is not protected by a internal circuit breaker.

Inexpensive surge boards may only work once, and then not provide any indication to whether they have been damaged.  Recall that many surges are invisible and only the surge protector will know a surge has occurred.  

Other protectors do not provide high level protection, meaning that your equipment will be protected by a minor power surge, but not by a higher or continuous surge.

Many inexpensive power extension boards sport on their faceplate the writing ‘surge protected’.  These boards are nothing more than glorified power boards and are not suitable for the protection of delicate equipment against any form a power surge.

Circuit Breakers Verses Surge Protection

A circuit breaker will provide an initial level of protection against a power surge – provided the circuit breaker trips, does not malfunction, and the intensity of the power surge is great enough to trigger the circuit breaker.  However, a circuit breaker is NOT designed to filter electrical noise or minor power surges – these electrical imbalances will not trigger a circuit breaker and the electricity will travel to the power point and onward to any equipment attached to the power point.  As discussed earlier, minor power surges are responsible for shortening the life of many components.

It should be remembered that although a circuit breaker will probably be triggered during a high volume or continuous power surge, the breaker may not trigger if the power surge is minimal.  It also worth remembering that a circuit breaker does not trip immediately a power surge enteres its circuit.  There is a millisecond or two delay.  This delay can be enough for power to travel through the circuit breaker to any delicate equipment attched to a power point.

A circuit breaker is designed to trigger when there is an over amperage above the circuit breaker's rating.  it protects the wires from over-amperage and overheating and potential for fire to occur.  A surge protector - which may also incorporate a circuit breaker,  is designed to protect/filter against power surges.  Although both pieces of equipment are similar, there end uses are different.

I have used, for several years, surge protectors manufactured by Belkin.  In general they were reliable and each unit provided two LED lights to warn if the device was not working.  However, Belkin protectors have a limited life time based on their Joule reservoir, which in moderately priced units is around 525 Joules.

Novaris Tasmania

Considering the expense and the amount of time that has been expended into building the simulator, I decided to up the ante and purchase a more solid and reliable system to protect against possible unwanted power surges, noise and spikes.  

LEFT:  Novaris PP10A/4 surge filter.  Simple LEDs indicate functionality of the unit while a push to reset circuit breaker button is located on the side of the unit.  4 power points facilitate connection of plugs or extension boards.

Novaris Tasmania sounds more in-line with something Stephen Hawkens has recently discovered and named in a far away galaxy; however, the name belongs to a Tasmanian company that develops and manufacturers surge protection equipment explicitly for industries that operate delicate equipment.

Two PP10A(4) surge filters manufactured by Novaris in Tasmania, Australia were commissioned.   For those more technically or theoretically inclined, the PP10A/4 specification sheet can be read here.  

The simulator, with everything operational, draws very close to 10 amps; therefore, to stop the possibility of the household circuit breaker tripping if the 10 amp boundary is crossed, various simulator sectors are connected to two power points in two power zones.  At each power point I have installed a PP10A/4.  

The PP10A/4 enables four extension boards to be attached, which between two units, is more than enough to ensure that everything in the simulator is protected.

Complete Protection - Modems and Routers

Often forgotten is the need to also protect against unwanted noise and surges that may be transmitted along copper wires from the telephone line to the router, modem and switch box (assuming the simulator is connected to the Internet).

This may or not be an issue depending upon the type of wiring that has been used – older style copper wires have good conductivity; therefore, these wires will transmit the effects of a power surge; however, modern glass wire has minimal conductivity which lessons the opportunity for electricity to migrate.

Many surge protectors also provide protection in this area; however, as stated earlier the effectiveness of any surge protector to protect against unwanted power surges is dictated by its Joule reservoir.

Future Post

This post has focused, in the simplest terms, on the concept of household power distribution and the need for some type of surge protector.  In a future post, I will discuss other methods of protecting delicate components from unwanted surges in power – in particular how to protect interface cards from damage from internal power spikes caused by computer power supply failures, reverse spiking, and grounding issues.

1 Murdering is a term used in the computer industry to describe when a process is stopped suddenly (such as turning the power off) without allowing the correct closing procedure to be followed.


Control Wheel Steering (CWS) Explained

CWS is an acronym for Control Wheel Steering.  Broadly speaking, it is a sub-set of the autopilot system which can used on either System A or B.  When engaged, CWS maneuvers the aircraft in response to control pressures applied to the control wheel or column.

LEFT:  B737 Mode Control Panel (MCP) showing location of CWS buttons on Collins unit .  The CMD and CWS buttons are located on the First Officer side of the MCP.  Each of the four press to engage buttons has a green annunciator which illuminates when the mode is engaged.

The control pressure is similar to that required for manual flight. When control pressure is released, the autopilot holds the existing attitude until CWS is disengaged, or the autopilot is engaged. 

The Flight Crew Training Manual (FCTM) states:

‘Control Wheel Steering (CWS) may be used to reduce pilot workload. Follow the manually flown procedure but instead of disengaging the autopilot, engage CWS.’

CWS is a similar system to the ‘Fly By Wire’ system utilised by Airbus.

Advantages of CWS

The obvious advantage in using CWS is that you do not have to continually apply positive pressure on the yoke and control column to maintain a set pitch or roll.  The control pressures on the flight controls are in the order of 37 pounds push/pull value +- 3 pounds and continually applying this pressure for a protracted period of time can be tiring.

Additionally, CWS enables you to fly the aircraft using the flight controls, rather than turning the heading knob on the Mode Control Panel (MCP) or configuring other automated processes such as Level Change, Vertical Speed, VNAV, etc.  Being able to ‘feel’ the control surfaces through the yoke and column has obvious benefits that flying using the MCP cannot convey.

CWS is also advantageous when flying in turbulent conditions (additional information below) as it results in smoother transitions than when the autopilot is used.  CWS also allows for greater control of the aircraft when performing touch and goes and circuits at lower altitudes.

Practical Example

CWS is often used during the climb to altitude, with the A/P being engaged at 10,000 feet.  

LEFT: PFD with CWS engaged during climb following flaps retraction.  FMA displays CWS R & CWS P, vertical speed is 2650 and pitch mode is V/S after changing from TOGA thrust following climb out.  Pitch and roll follows the FD bars and speed is 240 with altitude set to flight level 20900.  If CWS remains engaged, the aircraft will continue at this attitude.  Of importance is that the airspeed is NOT protected in certain modes.  In other words, if the attitude is altered, the airs[peed may increase or decrease accordingly without autothrottle intervention.

Following rotation, the Flight Director (FD) bars will be followed maintaining V2+15/20 until Acceleration Height (AH) is reached.  At AH, the MCP speed will be increased to climb speed, or to a constraint if required by Air Traffic Control.  As airspeed increases the flaps will be retracted.  When the flaps are retracted, the control column will be placed in a position that correlates to the Flight Director bars and CWS A or B will be engaged – the attitude of the aircraft will now be fixed.  

The aircraft, in TOGA thrust, will maintain the established pitch as it ascends to the altitude set on the MCP.  TOGA thrust is speed protected; therefore, as long as the FD bars are followed there will not be a speed incursion.  If a roll mode is selected, the navigational data provided by this mode is also supplied to the Flight Director.  Once the desired altitude has been reached, LNAV / VNAV is engaged.

Whether a flight crew used CWS is personal preference.  Some flight crews use it regularly while others have never used it.

Turbulence (autopilot or CWS)

The Flight Crew Training Manual (FCTM) states:

‘That during times of turbulence the A/P system (CMD A/B) should be disengaged.’

When the aircraft is flying through turbulence, the autopilot is attempting to maintain an attitude (pitch) that is based upon a predefined barometric pocket of air that is present at the altitude you are flying at.   In severe turbulence this pocket of air may not be stable and the autopilot will try to change altitude to match the changing barometric pressure.  At its worse, the autopilot may unexpectedly disconnect.

CWS provides a stable buffer in which the aircraft will maintain its position when flying through turbulence.  When CWS is engaged, it will maintain a preset attitude rather than the A/P attempting to match the attitude to changing barometric pressure.

Flight Crew Training Manuals differ in their content, as each manual has been written with a particular airline.  Many virtual flyers duplicate the procedures followed by Ryanair.  This is because the documentation for Ryanair is relatively easy to find, and the policy of this airline is reasonably conservative.  As such, I have transcribed from the Ryanair FCTM the segment on the use of CWS during turbulence.

The Ryanair FCTM states:

‘Flight through severe turbulence should be avoided, if possible.  When flying at 30,000 feet or higher, it is not advisable to avoid a turbulent area by climbing over it unless it is obvious that it can be overflown well in the clear.  For turbulence of the same intensity, greater buffet margins are achieved by flying the recommended speeds at reduced altitudes.  Selection of the autopilot Control Wheel Steering (CWS) is recommended for operation in severe turbulence’.

The recommended Ryanair procedures for flight in severe turbulence are:

•    Do not use Altitude Hold (ALT HLD) mode.

•    Airspeed - Target airspeed should be approximately 280 KIAS or 0.76 MACH, whichever is lower.

•    Severe turbulence will cause large and often rapid variations in indicated airspeed.  Do not chase the airspeed.

•    Yaw Damper – Engaged.

•    Autopilot - Optional - If the autopilot is engaged, use CWS position, do not use ALT HLD mode.

•    Autothrottle – Disengage.

•    Attitude - Maintain wings level and the desired pitch attitude. Use the attitude indicator as the primary instrument. In extreme drafts, large attitude changes may occur.  Do not use sudden large control inputs.  After establishing the trim setting for penetration speed, do not change the stabilizer trim.

Autothrottle Use

When CSW is engaged, the autothrottle should not be engaged.  The reason for this is because the autothrottle is coupled to the automation, and if there is a change in the aircraft's attitude there will be a corresponding change in engine thrust (similar to if the autopilot was engaged). 

This said, I have spoken with several pilots who claim that they leave the autothrottle on when using CWS.  In some respects it depends on the severity of the turbulence encountered. 

Lazy Flying

Although not sanctioned by Boeing, some pilots use CWS as a 'lazy way' of flying, whereby they may establish the aircraft at a specific attitude and vertical speed with the autothrottle engaged.  As CWS is a sub-set of the autopilot system, trim control will still be controlled by the system and the aircraft will maintain the desired attitude until CWS is cancelled.

A Virgin First Officer has stated that, after takeoff and flaps retraction, she will often use engage CWS to climb to a specific altitude, then she will engage LNAV, VNAV and the autopilot. 

It's important to realise there are many ways, (although not sanctioned by Boeing or a specific airline policy) to fly the Boeing 737 aircraft.

Technical Data (general)

The Flight Crew Training Manual states:

‘After autopilot engagement, the airplane may be manoeuvred using the control wheel steering (CWS) pitch mode, roll mode, or both using the control wheel and column. Manual inputs by the pilot using CWS are the same as those required for manual flight. Climbs and descents may be made using CWS pitch while the roll mode is in HDG SEL, LNAV or VOR/LOC. Autopilot system feel control is designed to simulate control input resistance similar to manual flight.'

The Mode Control Panel (MCP) has two CWS buttons located on the First Officer side of the MCP beneath the two CMD buttons (CMD A/B).  Like the autopilot, CWS has a redundancy system (system A or system B).  By default the CWS system is off (annunciator is not illuminated). 

The CWS system has been designed in such a way that it can be used with or without the autopilot.

To engage the CWS system, either of the two CWS buttons must be pressed, or the control column moved.  When engaged, the CWS annunciator will illuminate green and the Flight Mode Annunciator (FMA) on the Primary Flight Display (PFD) will annunciate CWS P and/or CWS R.

CWS cannot be engaged when any of the following conditions are met:

•    Below 400 feet.
•    Below 150 feet RA with the landing gear in the down position.
•    After VOR capture with TAS 250 kt or less.
•    After LOC capture in the APP mode.

Important Points:

  • CWS can only be engaged when there is no pressure on the flight controls. 
  • CWS can be engaged with the autopilot engaged or not engaged.

Operation - What CWS Does

As mentioned, the CWS system can be used with or without the autopilot being engaged. 

To use CWS in its own right, the autopilot (CMD) must be disengaged and the CWS button on the MCP pressed.  This will cause the CMD annunciation to extinguish and the CWS annunciation to illuminate.   To access the CWS system partially, and still use the autopilot, the control column is moved (pitch/roll) while the autopilot is engaged.

Although the CWS concept is easy to understand, documenting exactly what it does is difficult and this can cause confusion.  I wouldn't become too concerned with the 'technical jargon' below, as CWS is easy to master by using the function and remembering what it does:

The following information has been edited from documentation acquired from Smart Cockpit Airline Training.

1:  CWS selected - PITCH and ROLL   (autopilot not engaged)

•    Depressing the CWS button on the MCP engages the autopilot pitch and roll axes in the CWS mode.  It also displays CWS-P and CWS-R on the FMA on both the Captain and First Officer Primary Flight Displays (PFD).  (Note that CMD is not selected and the CMD annunciation is extinguished on the MCP).

•    With CWS engaged, the autopilot maneuvers the aircraft in response to control pressures applied to the control wheel or column.  The control pressure is similar to that required for manual flight.  When control pressure is released, the autopilot holds existing attitude and roll.

•    If the column pressure is released with a bank angle 6 degrees or less, the autopilot rolls the wings level and holds existing heading. This feature is inhibited when any of the following conditions are met:

(i)     Below 150 ft RA with the landing gear down;

(ii)    After F/D VOR capture with TAS 250 kt or less; and,

(iii)   After F/D LOC capture in the APP mode.

2:  Moving control column - PITCH  (autopilot engaged)

•    The FMA will display CWS-P.

•    The pitch axis engages in CWS while the roll axis is in CMD when:

(i)     The autopilot pitch has been manually overridden with control column force and the  force required for override is greater than normal CWS control column force.  Note that manual pitch override is inhibited in the APP mode with both autopilots are engaged (autoland).

Important Points:

  • When approaching a selected altitude in CWS-P with the A/P in CMD, CWS-P changes to ALT ACQ and, when at the selected altitude, ALT HOLD engages.
  • If pitch is manually overridden while in ALT HOLD at the selected altitude, ALT HOLD changes to CWS-R If control force is released within 250 ft of the selected altitude, CWS-P changes to ALT ACQ and the autopilot returns to the selected altitude and ALT HOLD engages.  If the elevator force is held until more than 250 ft from the selected altitude, pitch remains in CWS PITCH.

3:  Moving control column - ROLL  (autopilot engaged)

•    The FMA will display CWS-R.

The roll axis engages in CWS while the pitch axis is in CMD when:

(i)     The pitch has been manually overridden with control column force and the force required for override is greater than normal CWS control column force.  

Important Point:

  • With CWS-R selected and the autopilot engaged, the aircraft will capture a selected radio course while the VOR/LOC or APP mode is armed. Upon intercepting the radial or localizer, the F/D and autopilot annunciation changes from CWS-R to VOR/LOC engaged and the autopilot tracks the selected course.

Using CWS (Autopilot Engaged) - Simplified

This segment has been added in response to some readers who stated they had difficulty in understanding some of the above content.  I hope it explains, in easier terms, how the CWS system can be used when the autopilot is engaged.

Moving the flight controls (pitch/roll) during automated flight will cause the CWS system to engage.  However, the autopilot (CMD) will remain selected and the annunciator will remain illuminated on the MCP. 

Flying the aircraft in this manner can be useful when hand flying an approach, but wishing to follow the automated inputs from the ILS and/or FMC.

The following observations will occur.

Moving flight controls left or right (roll):

(i)      The autopilot annunciation will remain illuminated;

(ii)     The FMA on the PFD will alter from CMD to CWS-R;

(iii)    The AFDS will illuminate A/P P/RST; and,

(iv)    The heading annunciation on the MCP will extinguish, as will the LNAV annunciation if engaged.

The aircraft can now be flown using control wheel steering.  To return to fully automated flight, press the heading button on the MCP.  LNAV, if used, will also need selecting.

Moving flight controls up or down (pitch):

(i)      The autopilot (CMD A/B) annunciation will remain illuminated;

(ii)     The FMA on the PFD will alter from CMD to CWS-P;

(iii)    The AFDS will illuminate A/P P/RST; and,

(iv)    The heading annunciation on the MCP will extinguish, as will LNAV annunciation if engaged.

Important Point:

  • If the pitch is altered to cause the aircraft to ascend, the altitude window in the MCP must be changed to the new altitude prior to moving the flight controls (altitude capture is automatic).  This is not required if the pitch is changed to cause the aircraft to descend.

Final Call

The use of CWS is very much underused and under appreciated - whether used as a stand-alone system, or in conjunction with the autopilot.

Although surface control loading in a simulator rarely matches that of a real aircraft, the use of CWS in a simulator environment can still have positive benefits equating to better aircraft handling, especially when flying circuits and flying in turbulence.

NOTE:   This article has been rewritten to aid in clarity (18 June 2018).

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