E-mail Subscription

Enter your email address:

Delivered by FeedBurner

Syndicate RSS
Welcome

Mission Statement 

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

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

 

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

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

 

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

No advertising on this website - EVER!

 

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

 

 

 

 

  FEEDBACK:  

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

Journal Archive (Newest First)

Entries in FSX (81)

Thursday
Jun232016

RNAV, RNP, LNAV and VNAV Operations - Overview 

New flyers to the Boeing 737NG often become confused understanding the various terminology used with modern on-board navigational systems.

Although the concepts are easy to understand, the inter-relationship between systems can become blurred when the various types of approaches and departures are incorporated into the navigational system.

LEFT:  Collins Mode Control Panel (MCP) showing illuminated LNAV annunciation (click to enlarge).

This post will not provide an in-depth review of these systems; such a review would be lengthy, confusing and counterproductive to a new virtual flyer.  Rather, this post will be a ‘grass-roots’ introduction to the concept of RNAV, RNP, LNAV and VNAV.  I will also touch on the concept of Performance Based Navigation (PBN).

In the Beginning there was RNAV  

RNAV is is an acronym for Area Navigation (aRea NAVigation). 

Prior to complex computers, pilots were required to use established on-the-ground navigational aids and would fly directly over the navaid.  Such a navaid may be a VOR, NDB or similar device.  Flying over the various navaids was to ensure that the flight was on the correct route.  Often this entailed a zigzag course as navaids could not be perfectly aligned with each other in a straight line - airport to airport. 

When computers entered the aviation world it became possible for the computer to 'create' an imaginary navigation aid based on a direction and distance from a ground-based navaid.  Therefore, a straight line could be virtually drawn from your origin to destination and several waypoints could be generated along this line.   The waypoints were calculated by the computer based on ground VORs and positioned in such a way to ensure more or less straight-line navigation.

In essence, RNAV can be loosely defined as any 'straight line' navigation method similar to GPS that allows the aircraft to fly on any desired path within the coverage of referenced NAVAIDS.

Required Navigation Performance (RNP) and Performance Based Navigation (PBN)

Simply explained, Required Navigation Performance (RNP) is a term that encompasses the practical application of advanced RNAV concepts using Global Navigation Satellite Systems (GNSS).

However, there is a slight difference between RNP and RNAV although the principles of both systems are very similar. 

RNAV airspace generally mandates a certain level of equipment and assumes you have a 95% chance of keeping to a stated level of navigation accuracy.  On the other hand, RNP is performance based and requires a level of on-board performance monitoring and alerting.  This concept is called Performance Based Navigation (PBN).

RNAV and RNP both state a 0.95 probability of staying within 1 nm of course.  But RNP (through PBN) will let you know when the probability of you staying within 2 nm of that position goes below 0.99999.  In essence, RNP and PBN enable an aircraft to fly through airspace with a higher degree of positional accuracy for a consistently greater period of time. 

To achieve this level of accuracy a selection of navigation sensors and equipment is used to meet the performance requirements.  A further enhancement of this concept is the use of RNP/ANP (Required Navigation Performance and Actual Navigation Performance.  Advanced RNAV concepts use this comparative analysis to determine the level or error between the required navigation (the expected path of the aircraft) and the actual navigation (what path the aircraft is flying.)  This information is then displayed to the flight crew.

LNAV and VNAV

LNAV and VNAV are parts of the Flight Guidance System, and are acronyms for Lateral Navigation and Vertical Navigation'.  Both these functions form part of the automation package that the B737NG is fitted with.

LNAV is the route you fly over the ground. The plane may be using VORs, GPS, DME, or any combination of the above. It's all transparent to the pilot, as the route specified in the clearance and flight plan is loaded into the Flight Management System (FMS), of which the Flight Management Computer (FMC) is the interface.

The route shows up as a magenta line on the Navigation Display (ND), and as long as the LNAV mode on the Mode Control Panel (MCP) is engaged and the autopilot activated, the aircraft will follow that line across the ground. LNAV however, does not tell the plane what altitude to fly, VNAV does this.

VNAV is where the specified altitudes at particular waypoints are entered into the FMS, and the computer determines the best way to accomplish what you want.  The inputs from VNAV are followed whenever the autopilot is engaged (assuming VNAV is also engaged).  

The flight crew can, if necessary alter the VNAV constraints by changing the descent speed and the altitude that the aircraft will cross a particular waypoint, and the computer will re-calculate where to bring the throttles to idle thrust and begin the descent, to allow the aircraft to cross the waypoint, usually in the most economical manner.

VNAV will also function in climb and take into account airspeed restrictions at various altitudes and will fly the aircraft at the desired power setting and angle (angle of attack) to achieve the speed (and efficiency) desired.

There is not a fast rule to whether a flight crew will fly with LNAV and VNAV engaged or not; however, with LNAV and VNAV engaged and the autopilot not engaged, LNAV and VNAV will send their signals to the Flight Director (F/D) allowing the crew to follow the F/D cue display and hand fly the aircraft the way the autopilot would if it were engaged.

Reliance on MCP Annunciators

LNAV and VNAV have dedicated annunciators located on the Mode Control Panel (MCP).  These annunciators illuminate to indicate whether  a particular mode is engaged. 

LEFT:  Flight Mode Annunciator (FMA) showing LNAV and VNAV Path Mode engaged.  The Flight Director provides a visual cue to the attitude of the aircraft while the speed is controlled by the the FMC.  CMD indicates that the autopilot is engaged (ProSim737 avionics suite).

However, reliance on the MCP annunciators to inform you of a mode’s status is not recommended.  Rather, the Flight Mode Annunciator (FMA) which forms part of the upper area of the Primary Flight Display (PFD) should be used to determine which modes are engaged.  Using the FMA will eliminate any confusion to whether VNAV (or any other function) is engaged or not.

This post explains the Flight Mode Annunciators (FMA) in more detail.

Summary

In summary, RNAV is a method of area navigation that was derived from the use of VOR, NDBs and other navaids.  RNP through it use of GNSS systems has enabled Area Navigation to evolve to include LNAV and VNAV which are sub-systems of the Flight Guidance System -  LNAV is the course across the ground, and VNAV is the flight path vertically. 

Historically, navigation has been achieved successfully by other methods, however, the computer can almost always do things better, smoother and a little easier – this translates to less workload on a flight crew.  

In my next post, we will discuss RNAV approaches and how they relate to what has been discussed above.

References

The information for this article came from an online reference for real-world pilots.

Acronyms and Glossary

Annunciator – Often called a korry, it is a light that illuminates when a specific condition is met
DME – Distance Measuring Equipment
FMA - Flight Mode Annunciator
FMC – Flight Management Computer
FMS – Flight Management System
GPS – Global Positioning System
GNSS - Global Navigation Satellite System
LNAV – Lateral Navigation
MCP – Mode Control Panel
ND – Navigation Display
NPA - Non Precision Approach
PBN - Performance-based Navigation
RNAV – Area Navigation
RNP - Required Navigation Performance
VNAV – Vertical Navigation
VNAV PTH – Vertical Navigation Path
VNAV SPD – Vertical Navigation Speed
VOR – VHF Omni Directional Radio Range

Thursday
May262016

Trim Wheel Nut Tool - New Design

A potential problem when using an OEM Boeing throttle unit, is removing the nut that secures the trim wheels to the side of the throttle.  The nut has been designed in such a way that loosening it can only be done with a specialised tool.  Attempting to use a screwdriver or pliers may burr the nut, or slip causing damage to the trim wheel.

LEFT:  The redesigned Trim Wheel Nut Tool (click to enlarge).

In an earlier post I examined how a simple tool had been designed to easily remove the nut from the spline shaft that holds the trim wheels in place.   Although this tool was functional there was room for improvement in its design and manufacture.

New Design and Improved Engineering

The tool, has been redesigned and incorporates an aluminium cylinder that has been produced from a solid block of aluminium using a milling machine.  The inside of the cylinder has been milled and a set screw securely inserted.  

The outer flange, adjacent to the set screw has then been machined so that two ridges, approximately 1mm in height are either side of the set screw.  The set screw mates with the female located on the end of the spline shaft while the ridge provides extra purchase by mating with the indents in the nut.  In addition, a circular hole 8mm in diameter has been drilled through the cylinder enabling a similar sized piece of metal, or the shaft of a screwdriver to be inserted.  This allows additional purchase and leverage should the nuts be difficult to loosen.   Finally, the aluminium on the outside of cylinder has been slightly scoured to facilitate better grip.

Round and Round

The trim wheels are continually rotating back and forth as the aircraft is trimmed.  This rotation causes the nut, that secures the trim wheels to the spline shaft to, over time, become tighter and therefore more difficult to loosen.  This firmness is often exacerbated if working on a throttle unit removed from a real aircraft, that has not had the spline nuts removed for several years; corrosion and caked grease can easily cement the nuts in place.

LEFT:  New design has easier mating which enables greater purchasing power for removing tight spline nuts (click to enlarge).

This tool, although not an OEM part, is more than adequate to loosen the most determined nut.

Thursday
May122016

Knobs Aren't Knobs - Striving for the Perfect Knob

In Australia during the early 1980’s there was a slogan ‘Oils Ain't Oils’ which was used by the Castrol Oil Company.   The meaning was simple – their oil was better than oil sold by their competitors.  Similarly, the term ‘Knobs aren’t Knobs’, can be coined when we discuss the manufacture of reproduction knobs; there are the very good, the bad, and the downright ugly.

Boeing Knobs

As a primer, there are several knob styles used on the Main Instrument Panel, forward and aft overhead, various avionics panels, and the side walls in the B737-800 NG

If you search the Internet you will discover that there are several manufacturers of reproduction parts that claim their knobs and switches are exactly identical to the OEM knobs used on Boeing aircraft – don’t believe them, as more often than not they are only close facsimiles.

In this article, I will primarily refer to the General Purpose Knobs (GPK) which reside for the most part on the Main Instrument Panel (MIP).  Boeing call these knobs Boeing Type 1 knobs.

Why Original Equipment Manufacturer (OEM) Knobs Are Expensive

Knobs are expensive, but there are reasons, be they not be very good ones.  

LEFT:  The real item – a Boeing Type 1 General Purpose Knob (GPK) and issue packet.  There can be nothing more superior to an OEM part, but be prepared to shell out a lot of clams (click to enlarge).

The average Boeing style knob is made from painted clear acrylic resin with a metal insert. On a production basis, the materials involved in their manufacture are minimal, so why do OEM knobs cost so much…   Read on.

There are two manufacturers that have long-term contracts to manufacture and supply Boeing and Airbus with various knobs, and both these companies have a policy to keep the prices set at an artificially high level.

Not all flight decks are identical, and the requirements of some airlines and cockpits are such that they require knobs that are unique to that aircraft model; therefore, the product run for knobs for this airframe will be relatively low, meaning that to make a profit the company must charge an inordinate amount of money to cover the initial design and production costs.

A high-end plastic moulding machine is used to produce a knob, and while there is nothing fancy about this type of technology and the process is automated, each knob still requires additional work after production.  This work is usually done by hand.

Once a knob has been produced, it must be hand striped and finished individually to produce a knob that is translucent and meets very strict quality assurance standards.  Hand striping is a complex, time consuming task. 

Additionally, each knob must undergo a relatively complex paint spraying procedure which includes several coats of primer and paint, and a final clear protective coating.  Spray too much paint and the translucent area (called the pointer) inside the twin parallel lines will not transmit light correctly.  Spray too little paint and the knob can suffer from light bleed.  There is a fine line during production when it is easy to ruin an otherwise good knob with a coat of thickly applied paint. 

Finally, any part made for and used by the aviation industry must undergo rigorous quality assurance, and be tested to be certified by the countries Aviation Authority.  Certifying a commercial part is not straightforward and the process of certification takes considerable time and expense.  This expense is passed onto the customer.

Replicating Knobs - OEM Verses Reproduction

It’s not an easy process to replicate a knob to a level that is indiscernible from the real item.  Aside from the design and manufacture of the knob, there are several other aspects that need to be considered: functionality, painting, backlighting, robustness and appearance to name but a few. 

LEFT:  Often disregarded during the manufacture of reproduction knobs is the inner metal sleeve.  The sleeve protects the material from being worn out from continual use (click to enlarge).

Backlighting and Translucency

To enable the knob to be back lit calls for the knob to be made from a translucent material.  Unfortunately many reproduction knobs fall short in this area as they are made from an opaque material.

The knob must also be painted in the correct colour, and have several coats of paint applied in addition to a final protective layer.  The protective layer safeguards against the paint flaking or peeling from the knob during normal use.  In the photograph below, you can see where extended use has begun to wear away part of the knob's paint work revealing the base material.

Set Screws and Metal Inserts

Often lacking in reproduction knobs is a solid metal set screw (grub screw).

The task of the set screw to secure the knob against the shaft of the rotary so that when you  turn/twist the knob it does not rotate freely around the shaft.  Plastic set screws can be easily worn away causing the knob to freely rotate on the shaft of the rotary encoder. 

LEFT:  Detail of the grip and metal set screw.  The set screw is important as it enables the knob to be secured against the shaft of the rotary.    This knob previously was used in a Boeing 737-500 (click to enlarge).

The position of the set screws on the knob also deserves attention.  Correctly positioned set screws will minimize the chance of rotational stress on the shaft when the knob is turned.

Of equal concern is the hole on the underside of the knob where the rotary shaft is inserted.  The hole should be sheathed in metal.  This will increase the knob’s service life.  If the hole does not have a metal sheath, it will eventually suffer from wear (disambiguation) caused by the knob being continually being turned on its axis.   Finally, the knob must function (turn/twist) exactly as it does in the real aircraft.

Reproduction knobs may fail in several areas:

(i)    The knob has various flaws ranging from injection holes in the molded plastic to being the incorrect size or made from an inferior plastic material;
(ii)    The knob does not use metal set screws, and the set screws are not located in the correct position on the knob;
(iii)    The knob has a poorly applied decal that does not replicate the double black line on NG General Purpose Knobs.  The adhesive may not be aligned correctly and may peel away from the knob;
(iv)    The knob is made from a material that does not have the ability to transfer light (translucent pointer);
(v)    The knob does not appear identical in shape to the OEM part (straight edge rather than curved);
(vi)    The paint is poorly applied to the knob and peels off.  OEM knobs have several thin coats of paint followed by hard clear coating of lacquer to ensure a long service life;
(vii)    The colour (hue) of the knob does not match the same hue of the OEM product; and,
(viii)    The circular hole in the rear of the knob, that connects with the shaft of the rotary encoder does not have inner metal sleeve.  

The time it takes to manufacture a knob is time consuming, and to produce a quality product, there must be a high level of quality assurance throughout the manufacturing process.

Older Classic-style Knobs

It's common knowledge that many parts from the classic series airframe (300 through 500) are very similar, if not identical to the parts used in the Next Generation airframe.  Unfortunately, while some knobs are identical most are not.

The knobs may function identically and be similarly designed and shaped, but their appearance differs.  Knobs used in the Next Generation sport a twin black-coloured line that abuts a translucent central line called the pointer, classic series knobs have only a central white line.

Rotary Encoders

Although not part of the knob, the rotary encoder that the knob is attached deserves mention.

A fallacy often quoted is that an OEM knob will feel much firmer than a reproduction - this is not quite true.  Whilst it is true that an OEM knob does has a certain tactile feel, more often than knot the firmness is caused by the rotary that the knob is attached to.

Low-end rotary encoders that are designed for the toy market are flimsy, have a plastic shaft, and are easy to turn.  In contrast, rotaries made for the commercial market are made from stainless steel and are firmer to turn.

Also, low end rotaries and knobs are made from plastic and with continual use the plastic will wear out prematurely resulting in the knob becoming loose.

Final Call

Whether you use reproduction or OEM knobs in your simulator is a personal choice; It doesn't play a huge part in the operation of a simulator.  After all, the knobs on a flight deck are exactly that – knobs.  No one will know you have used a reproduction knob (unless low end reproductions have been chosen).

LEFT:  Many reproduction knobs fit the bill, and for the most part look and feel as they should.   It's easy to criticise the injected plastic being a little uneven along the edge, but this is unseen unless you are using a magnifying glass.

However, the benefit of using a real aircraft part is that there is no second guessing or searching for a superior-produced knob.  Nor is there concern to whether the paint is the correct colour and shade, or the knob is the correct shape and design – it is a real aircraft part and it is what it is.  But, using OEM knobs does have a major set-back - the amount of money that must be outlaid.  

But, second-hand OEM NG style knobs are not easy to find and often there is little choice but to choose the ‘best of the second best’. 

BELOW:  Cross section of a Boeing Type 1 General Purpose Knob.

Friday
Mar112016

BRT / DIM Functionality - Lights Test Switch

The annunciators in the Boeing 737 are very bright when illuminated, and the reason for the high intensity is justified - the designers want to ensure that any system warnings or cautions are quickly noted by a flight crew.

However, when flying at night for extended periods of time the bright lights can be tiring on your eyes.  Also, during critical flight phases such as during a night-time approach, the bright lights can become distracting.  At this time, the flight deck is usually dimmed in an attempt to conserve night vision. 

For example, the three green landing annunciators (Christmas tree lights), speed brake and flaps extension annunciators are all illuminated during the final segment of the approach.  At full intensity these annunciators can, at the very least, be distracting.

LEFT:  Lights Test switch.  The three way switch located on the Main Instrument Panel (MIP) Captain-side is used to toggle the intensity of connected annunciators.  The panel label reads TEST, BRT and DIM.  The switch in the photograph is an OEM switch which has been retrofitted to a Flight Deck Solutions (FDS) MIP.

To help minimize eye strain and to enable night vision to be maintained as much as possible, pilots can select from two light intensity levels to control the brightness output of the annunciators. 

Anatomy of the Lights Test Switch

The switch (a three-way toggle) which controls the light intensity (brightness level) is called the Lights Test switch.  The switch is located on the Main Instrument Panel (MIP).  The switch is not a momentary switch and whatever position the switch is left at it will stay at until toggled to another position.  The switch has three labelled positions: Lights Test, BRT and DIM. 

(i)           UP controls the lights test (labeled Lights Test);

(ii)          CENTRE is the normal position which enables the annunciators to illuminate at full intensity (labeled BRT); and,

(iii)         DOWN lowers the brightness level of the annunciators (labeled DIM).

OEM annunciators have a built-in Push-To-Test function, and each annunciator will illuminate when pushed.  The brightness level is pursuant to the position the Lights Test switch (DIM or BRT). 

The Lights Test will always illuminate all the annunciators at their full intensity (maximum brightness). An earlier article explains the Lights Test switch in more detail.

Special Conditions

When the Light Test switch is set to DIM, all the annunciators will be display at their minimum brightness.  The exception is the annunciators belonging to the Master Caution System (MCS), which are the master warning, fire bell and six packs, and the Autopilot Flight Director System (AFDS).  These annunciators will always illuminate at their full intensity because they are construed as primary caution and warning lights.

Variable Voltage

There is nothing magical about the design Boeing has used to allow DIM functionality; it is very simplistic.

Annunciators for the most part are powered by 28 volts; therefore, when the Lights Test switch is in the neutral position (center position labeled BRT) the bulbs are receiving 28 volts and will illuminate at full intensity.  Moving the switch to the DIM position reduces the voltage from 28 volts to 16.5 volts with a correspondingly lower output.  In the real aircraft, the DIM functionality (and Light Test) is controlled by a semi-mechanical system comprising relays and zener-type diodes that vary the voltage. 

Two Controlling Systems - your choice

The DIM and Lights Test functionality can be achieved in the simulator by using one of two systems - software or mechanical.

Software Controlled

The avionics suites developed by Prosim-AR, Project Magenta and Sim Avionics have the ability to conduct a full Lights Test in addition to allowing DIM functionality.  However, depending upon the hardware used, the individual Push-To-Test function of each annunciator may not be functional.  The DIM functionality is controlled directly by the avionics suite software; it is not a mechanical system as used in the real aircraft.

In ProSim737 the DIM function can be assigned to any switch from the configuration/switches and indicators menu.  In Sim Avionics the function is assigned and controlled by FSUPIC offsets within the IT interface software.

Mechanically Controlled

I have chosen to replicate the Lights Test and DIM functionality in a similar way to how it is done in the real aircraft. 

There are no benefits or advantages to either system – they are just different methods to achieve the same result.

Two Meanwell power supplies are used to provide the voltage required to illuminate the annunciators.  A 28 volt power supply enables the annunciators to be illuminated at their brightest intensity, while the less bright DIM functionality is powered by a 16.5 volt power supply (or whatever voltage you wish).

A heavy duty 20 amp 28 volt relay enables selection of either 28 volt or 16.5 volts.

DIM Board

A small board has been constructed from ABS plastic on which is mounted a 20 amp 28 volt relay and a terminal block. The board, called DIM is mounted behind and beneath the MIP. This facilitates easy access to the required power supplies mounted within the Power Supply Rack (PSR)

LEFT:  The DIM Board is surprisingly simple and comprises a single terminal block and a heavy duty 28 volt relay.  Wires are coloured and tagged to ensure that each wire is connected to the correct terminal (click to enlarge).

An important function of the DIM board is that it helps to minimise the number of wires required to connect the DIM functionality to the various annunciators and to the Lights Test switch.   

Interfacing and Connections

Prior to proceeding further, a very brief explanation is required to how the various panels receive power. 

Rather than connect several panels directly to a power supply, I have connected the power supplies to two 28 volt busbars - one busbar is located in the center pedestal and other is attached to the rear of the MIP.  The busbars act a centralised point from which power is distributed to any connected panels.  This allows the wiring to be more manageable, neater, and easily traceable if troubleshooting is required.

Likewise, there is a lights test busbar located in the center pedestal that provides a central area to connect any panel that is lights test compliant.  Without this busbar, any panel that was lights test compliant would require a separate wire to be connected to the Lights Test switch in the MIP.  To read more about this feature, navigate to the page that deals with the lights test busbar.

The below mud schematic may make it easier to understand.  To view the schematic at full size click the image.

A 28 volt busbar located in the center pedestal is used as a central point from which to connect various panels to (lower pale blue box).  

The busbar is connected to the terminal block located on the DIM board.  Wires from the terminal block then connect to a 16.5 and 28 volt power supply located in the PSR (orange boxes). 

The 28 volt relay is also wired directly to the terminal block on the DIM board and a single wire connects the relay with the Lights Test switch located in the MIP (green box). 

From the Lights Test switch, a single wire connects with the lights test busbar located in the center pedestal (pale blue box).  The purple box represents any panel that is Lights Test compliant - a single wire connects between a panel and the lights test busbar.

Although this appears very convoluted, the principle is comparatively simplistic.

How it Works

When the Lights Test switch is toggled to the DIM position the relay is closed.  This inhibits 28 volts from entering the circuit, but allowing 16.5 volts to reach the 28 volt busbar (located in the center pedestal); any annunciators connected to this busbar will now only receive 16.5 volts and the annunciators will glow at their lowest brightness level.  Conversely, when the switch is toggled  to BRT or to Lights Test, the relay opens and the busbar once again receives 28 volts.

Which Annunciators are Connected to DIM Functionality

The annunciators that connect with the DIM board are those in the fire suppression panel, various panels in the center pedestal, the forward and aft overhead, and in the MIP.  If further annunciators in other systems require dimming, then it is a matter of connecting the appropriate wires from the annunciator to the 28 volt busbar, and to the and lights test busbar, both of which are located in the center pedestal.

BELOW:  A rather haphazard video showing the two brightness levels.  The example shows the annunciators in the OEM Fire Suppression Panel (FSP).  The clicking sound in the background is the Lights Test switch being toggled from BRT to DIM and back again.  Note that the colour of the annunciator does not alter - only the intensity (brightness).  The colour change in the video, as the lights alter intensity, is caused by a colour temperature shift which is not visible to the naked eye but is recorded by the video.

Glossary

Annunciator - A light that illuminates under set conditions.  Often called a Korry.
Busbar - A bar that enables power to distributed to several items from a centralised point.
Mud Schematic - Australian colloquialism meaning a very simplistic diagram (often used in geological mapping / mud map).
Push-To-Test Function - All annunciators have the ability to be pushed inwards to test the circuit and to check if the globe/LED is operational.
OEM - Original Equipment Manufacturer aka real aircraft part.
Panel/Module - Used interchangeably and meaning an avionics panel that incorporates annunciators.
Toggled - A verb in English meaning to toggle, change or switch from one effect, feature, or state to another by using a toggle or switch.

Saturday
Dec262015

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.

Dropout

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.

Surge

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.

Page 1 ... 3 4 5 6 7 ... 17 Next 5 Entries »