Getting Wise to the EWIS: Wire Insulation

So many wires, so little maintenance. This seems to be the unfortunate state of affairs for many planes. Technology, especially in the form of computers, has evolved in leaps and bounds yet many of today’s aircraft are designed as if they are stuck fighting Hitler. No surprise then that wiring is still configured in ways that are incompatible with newer systems, communications or otherwise. Not to mention such configurations are inefficient, non-ergonomical, and dangerous.

Modern aircraft consist of an Electrical Wiring Interconnection System (EWIS). This system is complex, to say the least. Depending on the type of plane, this system can include anywhere from 10-200 miles of wire. That’s a lot of string that needs periodic investigation.

When dealing with your EWIS you have wire but you have other related components to consider as well: connectors, circuit breakers, and conduits.

One of the major issues when installing or replacing your EWIS is wire insulation. Of course, the purpose of insulation is quite obvious. If you’re running an electric current through a wire, you don’t want to get electrocuted and you also want the current to get to the right destination. Insulation thus provides both a barrier for protection and a means to guide electricity; that way it doesn’t spread in all directions along the wire path or transfer to surrounding areas. Thus, a circuit’s integrity is maintained and personnel are able to handle wire.

Selecting the right wire insulation is not easy since there are many trade-offs by choosing one over the other. Advantages and disadvantages need to be carefully considered and often costs and time may trump all. Still, it’s important that we at least supply you with some information to guide you through the process.

INSULATION TYPE

Without getting too complicated, there are generally four types of insulation material commonly found in aircraft: (1) Aromatic Polyimide, (2) ETFE, (3) PTFE, and (4) TKT.

Aromatic Polyimide – Sometimes polyimide is abbreviated PI; it is also called Kapton. The ‘aromatic’ refers to its molecular structure that offers great thermostability, hence its usage in insulating wiring. This material possesses great abrasion and cut-through resistance. It is also low smoke and non-flammable while lighter in weight compared to others. Its disadvantages: low arc-track resistance and limited flexibility.

ETFE – Short form of ethylene tetrafluoroethylene; aka Tefzel. Its ease of use makes it desirable. It also excels in chemical and abrasion resistance. Beware: ETFE tends to soften at higher temperatures and does not offer much in cut-through resistance. Because of its softness, it is well to avoid when bundling with other wire types.

PTFE – Stands for polytetrafluoroethylene but is often referred to as Teflon. PTFE offers a slew of advantages: superb high temperature properties, non-flammability, great flexibility and chemical resistance. Unfortunately, PTFE has poor cut-through resistance and is the heaviest form of insulation.

TKT – A composite of plastics; it stands for Teflon-Kapton-Teflon. It possesses a high temperature rating (260°C) and contains a solid level of cut-through and arc-track resistance. However, TKT is prone to outer layer scuffing.

For an equally useful and more thorough presentation of the pros and cons of insulation type, you can check out NASA’s Wire Insulation Selection Guideline Chart.

INSULATION PROPERTIES

Ten characteristics are often used when comparing one insulating material over another.

Weight – This is a major issue. Heavy wire multiplied by the amount of wire can add several hundred pounds of weight to your plane, especially if there are miles of wire required in your EWIS. The lighter the plane the less fuel is needed to overcome the weight burden. This translates to savings on costs associated with fuel consumption.

Temperature – Flight exposes wire to wide temperature variances. You want to ideally aim for insulation that offers the widest range or the highest temperature resistance.

Creep (at temperature) – This refers to the insulating material’s susceptibility to deformation, in this case how temperature warps the integrity of the material.

Flammability – When you deal with electrical wire there’s always the possibility of fire. Safety concerns have you aim for insulation that offers added protection against flames.

Smoke Generation – With flames comes smoke. Once a fire exists and the insulation starts to burn will it generate a great deal of toxic fumes?

Flexibility – Try to wire an airplane and you will quickly find configurations that use only straight lines are impossible. Wires have to bend during installations where point A to point B are not direct.

Resistance to:

Abrasion – Friction wears down materials. Wires are sometimes bundled but can still run up against adjacent surfaces. This leads to chafing and deterioration of insulation. No question, you don’t want insulation to wear down. If a wire is exposed, there’s the potential for electrocution, arc and spark creation, and possible fires.

Cut-through – This refers to the pressure exuded by a mechanical force, like the sharp edge of a wire cutter. You want the insulation material to be durable and be able to resist heavy loads or forces acted on it without disrupting the wires functionality.

Chemical – Planes, amongst other things, operate on the interaction of various chemicals. Fuel and even cleaning supplies will over time corrode insulation.

Arc Propagation – The causes of arc propagation are numerous; chafing, faulty installation, exposure to nearby water and fluids. Electric arcs can cause fires and pose a serious safety threat.

SIDE-BY-SIDE COMPARISON

FAA-wire-insulation

Comparison among wire insulation material based on desirable properties. Source: FAA Aircraft EWIS Best Practices Job Aid (Click to enlarge)

The FAA sure does have a lot of documentation. And that’s a good thing. Especially when dealing with the ins and outs of airplanes. The accompanying chart provides a useful guide in selecting wire insulation. Based on the chart, you can see that PI and PTFE offer the most desirable combination of traits. But TKT and ETFE still maintain certain advantages (stated earlier). By matching the above mentioned properties with the above types of insulating material, you can get an idea of how to improve your EWIS.

TERMINATION…FOR NOW

In the weeks and months ahead we will revisit issues related to EWIS as it is a growing concern and requires constant vigilance. Hopefully you found this post informative. Remember, EWIS is really just the word “wise” jumbled up. Don’t get tangled up with your wires. Get wise to the EWIS. Keep checking in from time to time and we will make sure you don’t.

References

http://www.eaa.org/experimenter/articles/0903_aircraft_wiring.pdf
http://www.vision.net.au/~apaterson/aviation/wire_types.htm
http://www.wirefacts.com/web/Insulations.aspx
http://www.tc.faa.gov/its/worldpac/techrpt/artn06-17.pdf
http://en.wikipedia.org/wiki/Electrical_wiring_interconnection_system
http://www.faa.gov/training_testing/training/air_training_program/job_aids/media/EWIS_job-aid_2.0_Printable.pdf
http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%20120-102A.pdf
http://www.mitrecaasd.org/atsrac/meeting_minutes/2002/2002_04_FAA_Wire_Degradation_Study.pdf
http://www.easa.eu.int/agency-measures/docs/agency-decisions/2008/2008-007-R/Decision%202008-007-R%20-%20Annex%20II%20-%20AMC%2020-21.pdf

The Wonderful World of WowToyz

Ah, to be young again.

magic-skylar-complete

The magic of Lauren Horgan©2013

Ever been around a child who is just a ball of energy? A kid who has eyes so big, you could confuse them with planets in our solar system? I’ve seen such a child. Especially every time I look into a mirror.

As you get older, you realize people constantly force you into doing things. They tell you to “grow up.” You have to get serious with your life. Don’t waste your time on such foolish and whimsical notions as “having fun.”

What happens? You get a job, possibly begin a business. And your entire life becomes consumed by it. Your daily routine varies little. It’s always a different day, same old stuff. No longer is your life about discovery and the joy it brings, it’s about following a set of procedures: lists, scheduled meetings, conference calls, endless emails—all for the sake of keeping your business afloat. Eventually time flies and you’re left with grey hair (that is if you haven’t lost it completely). You also have a new hobby; a dependency on Maalox and prescription drugs.

It doesn’t have to be that way.

Hi, my name is Skylar and I am a geek. A SkyGeek to be more precise. I help run this site, a site that revolves around aviation supplies. As our motto reveals, we aim to “Supply the Skies.” While certainly our focus is selling customers tools and parts related to aviation, we also sell more.

In fact, we have a portion of inventory dedicated to gifts and toys. One of the manufacturers we do business with is WowToyz. I figured highlighting the items we sell from them might allow you to tap into your inner child.

Books

“My Totally Awesome Travel Fun Book” – This book helps educate kids about planning trips. They will read about certain customs and manners to keep in mind while travelling. With a travel diary included as well as games to play, it certainly lives up to the name ‘fun book.’ Plus, I love the title: totally awesome!

“The Wright Brothers Coloring Book”– Come on, you can’t have a proper childhood without a coloring book. This particular book comes with a pack of crayons so children can learn about the founders of flight while delightfully doodling to their heart’s content. Brings new meaning to the term “flying colors.”

Builderific

This item is for all those growing gearheads and would-be engineers. If you love Legos but always felt limited by their pieces, Builderific is where it’s at. The pieces (118 per package) are not stiff but flexible. The benefit of this is clear: your designs are not limited to straight lines but can incorporate curves. This translates to more possibilities that will maximize junior’s imagination.

Space Shuttle Playsets

We tell our kids to reach for the stars (or at least shoot for them). Maybe with enough hard work they may someday work for NASA. Plant the seed of their future career by handing them one of four aerospace playsets. The 4-piece Space Shuttle playset is cool because not only is it fun to simulate rocket launches but the packaging comes with a blister card containing space exploration information. The Giant Space Shuttle playset adds to the above playset by featuring two astronauts and a launch pad; as a bonus it comes with a rocket poster. The 5-piece Space Shuttle playset adds satellite equipment in addition to the space shuttle, astronaut and rocket play pieces. As for the ultimate in space-themed toys the 20-piece playset has six astronauts, a “Saturn” rocket with a trailer truck, a lunar lander, moon rover, and more. When it comes to these items you’ll be thinking one thing: Space, the final fun-tier!

Gliders

An inexpensive yet immensely satisfying type of toy is the glider. WowToyz InAir® brand offers two popular choices. The Air Force One foam board glider is great if your child wishes to be the next President of the United States. The Giant Sky Rover foam board plane gives you the option of flying a mono or a biplane configuration; it also contains a nifty propeller (sort of like the SkyGeek hats…trust me, propellers can offer hours of entertainment).

But if you want to fly high and be super cool you can’t go wrong with the F-16C USAF Thunderbird foam board glider. This is the type of plane you think of when you want to wave Old Glory with pride and showcase your patriotism. Let it soar on veteran holidays or the Fourth of July and make Uncle Sam proud.

Fun Times

I can’t help but emphasize that all these items are under $25 and most of them are under $10. Try to go to any brick-and-mortar store and try to spend less than that. Personally, I like the fact that WowToyz sells to specialty retailers instead of big box stores. It lets them focus on quality rather than on massive output of hastily manufactured products. I think that approach has worked out well. How else do you explain the awards they’ve received for many of their toys.

Over the years, I have traveled many places and been to many exotic locales. Of course, most of them were imaginary but they were important in developing my sense of creativity. Toys may be seen as the financial equivalent of kicking yourself in the butt. It has also been equated with flushing your precious hard earned income down the toilet. “Why do I need to buy a dumb piece of plastic that we’re just going to throw out in a year?” some parents reason. If these same parents only knew what toys meant to kids and how they help cultivate a sense of ingenuity then they would know that toys are anything but a waste. In fact studies have shown that playing is useful in the healthy development of children.

A child is only young once. Relive the memories from your youth by creating memories for them. Perhaps you can even participate in the child’s play. Forever young in the form of fun brought to you by WowToyz.

FAA Safety Alert: New York Sectional, New York TAC, Boston TAC

Mack here with an update.

Below is a Safety Alert from our buddies at the FAA. It concerns effective date changes of Visual Flight Rules (VFR) charts in the Northeast U.S., specifically New York and Boston. The Safety Alert reads:

The effective dates for the New York Sectional Chart, New York Terminal Area Chart, and Boston Terminal Area Chart are being changed. The next editions of these charts (87th, 85th, and 82nd respectively) will be effective July 25, 2013 to November 14, 2013. The current editions of the New York Sectional Chart (86th), New York Terminal Area Chart (84th), and Boston Terminal Area Chart (81st) will remain effective until July 25, 2013. Please refer to the Aeronautical Chart Bulletins section of the Airport/Facility Directory for updated information regarding major changes in aeronautical information that have occurred since the last chart publication date.

If you don’t have it already, get the latest Northeast U.S. Airport/Facility Directory.

We realize it is well before July 25, 2013 but as with the purpose of the alert, better safe than sorry. We figured we’d give you some advanced warning. As all of you know, using an obsolete chart for navigation is reckless and dangerous and should be avoided at all costs. Don’t do it. Be prepared.

For all those affected by these changes, make sure your charts are up to date. Purchase or subscribe to any or each of these charts by clicking the links below:

New York Sectional Chart

New York Terminal Area Chart

Boston Terminal Area Chart

As for those who enjoy looking at the fancy FAA seal, you can view the official Safety Alert release.

As always, have a safe flight.

Got Your Ears On? A Guide to Headsets

As a pilot there is little doubt which piece of equipment is often regarded as top gun. Headsets. In fact, it’s not a stretch to say that one can feel naked without them. And if you have no means of communicating while flying, in many cases you may as well be flying blind.

Amongst the various pilot lingo used in aviation there’s one phrase that seems fitting when discussing headsets: “Got your ears on?” Are you on air and listening? SkyGeek has compiled some information that you can log into your noggin.cartoon-headset

Headphones or Headsets?

Of course we all know that aviation headsets are more than glorified headphones. Whereas headphones are primarily used for listening to music, headsets offer so much more since they have to compensate for variances in pressure and altitude–something not experienced in your average home.

For starters, wearing headsets is a way to reduce ambient noise. A plane is a battleground of sounds competing to annihilate your ear drums. Engines, propellers, gears, hail, airflow— these are just some culprits you want protection from. Prolonged exposure to high decibel levels (with planes, think of a leaf blower on steroids) will inevitably lead to hearing loss. Thus, headsets are a recommended means of avoiding damage to your ears. (Some say they should be mandatory and really, if you are repeatedly exposed to any kind of loud noise why wouldn’t you wear them, but that is a debate for another time).

The other highlight of a headset is its enhanced communication capabilities. Whether it’s between passengers or other planes or air traffic control (ATC), headsets are designed for radio transmission and reception, a device for relaying messages. Unlike headphones, many headsets have microphones in addition to speakers.

A headset is a big-ticket item that, depending on your preferences, may be pricier than expected. Headsets without all the bells and whistles can be under $100 but the high-end ones can easily exceed $600. So the more knowledge you have the more sound your purchasing decision.

It’s time now for a little cockpit commentary.

Features/Terms

When buying headsets, ever encounter terms that sound impressive but fly circles around your head? Here are a few phrases to part the clouds of confusion…

Attenuation – Fancy way of saying that your headset can reduce a signal with minimal distortion; measured in decibels (dB). Since attenuating something means to reduce it, a headset with high attenuation will reduce a lot of sound.

Frequency Response – The ability of a headset to reproduce audio frequencies; it is measured in hertz (Hz). This figure can be misleading as manufacturers may not accurately reveal a headset’s numbers, opting instead to present a range. You shouldn’t rely too heavily on this figure to make the final decision.

Impedance – Refers to a component on the headset that resists the electrical current passed through them; it is measured in Ohms. Should you look for low or high impedance? Like many answers, it depends. High impedance devices may not be compatible with older hardware so that may aural quality issues. Many modern systems will be able to adapt to both low and high impedance. Remember though, compatibility is key. Check to see if your headset fits with the system you are plugging it into, e.g. a low impedance headset and a low impedance system. Low and high either way may cause problems.

Electret – A combination of the word “electricity” and “magnet.” It refers to a material used in microphones that creates internal and external electric fields that support not only headsets but other electronic devices like GPS systems. It is mainly used so that a polarizing power supply is not needed. Electret microphones are usually considered high-impedance as opposed to dynamic microphones, which are associated with low-impedance. Dynamic microphones are commonly used in the military, in older model planes, and in helicopters.

Panel Powered – If a headset is labeled as “panel powered” it means you can use, say for instance, an ANR headset without batteries since you will receive power from the aircraft panel. However, when using this feature, make sure you have the panel specifically wired for this kind of headset. Otherwise, your headset may not be compatible with the aircraft radio and intercom installation.

TSO – An acronym that stands for Technical Standard Order. It is a minimum performance standard established by the Federal Aviation Administration (FAA). It is becoming increasingly more common for pilots to wear TSO-certified headsets. By following such a standard quality assurance can be monitored in regards to the equipment used. However, much controversy surrounds TSO-certification as some believe it is not necessary.

Passive vs. Active Noise Reduction

Aviation headsets usually highlight their ability to reduce noise levels because, as already mentioned, noise not only damages your ears but also interferes with communication. This is accomplished either passively or actively. Passive noise reduction (PNR) headsets mechanically block sound waves. They often consist of specialized ear cups that feature noise-proof insulation. A major benefit is their affordability, especially when compared to their active noise reduction counterparts.PNR headsets generally offer noise reduction up to 15 to 20 decibels.

In addition to the features of PNR headsets, active noise reduction (ANR) headsets often contain specialized microphones located outside each ear cup. Their claim to fame: their ability to cancel ambient noise with opposing sound waves. Of course, this added bonus tends to increase the price tag as it is more effective. ANR headsets reduce noise up to 30 decibels.

esterline-anr-pnr-graph

Visual aid showing the efficacy of active and passive noise reduction in a military setting. Graph provided by Esterline.

To give you a better idea of how PNR and ANR work in reducing noise levels, check out the graph provided by the folks at Esterline and compare the decibel levels with and without these reduction techniques. Based on the graph, you can see typical noise in military environments can easily exceed 100 decibels. But that’s just for ground vehicles. According to this same source, fast jets can approach 150 decibels, a level that exceeds the parameters of this graph! Even if you don’t fly military aircraft, this demonstrates the practicality of headsets that incorporate PNR and ANR technology.

Type

Once familiarized with some of the lingo, narrow your search for the right headset by choosing between type. This can be quite easy. The names indicate their use but just in case, here is a quick breakdown.

Military headsets are used in military aircraft, particularly those with a single jack (e.g. U-93A/U) and low impedance systems. Civilian helicopters with a single jack such as the U-174/U or U-93A/U will link up with helicopter headsets. Pilots who fly for a living on business airliners should investigate commercial headsets, which offer comfort to the cockpit environment. General aviation headsets are designed for fixed wing planes, especially those with two standard jacks—PJ-055 and PJ-068.

Headsets aren’t only for pilots but can be for passengers. Kids or adults with smaller head sizes will benefit from children headsets. SkyGeek even carries animal headsets for your pet pooch.

Brands

When it comes to selecting a headset based on brand, SkyGeek will not play favorites. Brand loyalty is something that is a personal choice; all manufacturers have their strong points. All we can do is offer you as many options as possible. That’s why we stock headsets from ASA , David Clark , Pilot USA , Telex , Sennheiser , FlightCom , Lightspeed , SoftComm , and Rugged Air. Clarity Aloft and Bose are other known and reputable brands.

blog-headphones

Illustration by Lauren Horgan©2013

SkyGeek recommends researching not only among the models within each brand but between the brands as well. As you examine the product pages of each headset you will come across overlapping features and will be able to discern one headset’s advantage(s) over another.

Final Thoughts

A headset is something that ultimately comes down to what feels right and what works best. Comfort is essential. Time and money are better spent on a headset that doesn’t weigh a ton or doesn’t crimp your ears. Use is another factor. If you are a professional or frequently fly to the point where you are practically sleeping in your cockpit, you don’t want to skimp on costs. When it comes to long term use, headsets made of durable material and cutting-edge designs (both which drive the cost upwards) will endure and provide the best return on investment. However, if you are really frugal and don’t see the need for advanced technology and top-of-the-line features, then buy something that is affordable. It all depends on your level of commitment to having the best protection and communication available given your budget.

References:
http://www.goodgearguide.com.au/article/296352/what_do_headphone_specifications_mean_/

http://www.ehow.com/list_7382196_parts-headset.html

http://uflymike.com/media/documents/UntanglingtheAirlinePilot-TSOHeadsetControversy.pdf

http://www.afeonline.com/shop/datasheets/headset_buying_advice.pdf

http://www.ehow.com/about_5375252_decibel-level-jet-plane.html

http://en.wikipedia.org/wiki/Electret_microphone

http://www.head-fi.org/t/571384/low-impedance-vs-high-impedance-huge-difference

http://www.airliners.net/aviation-forums/tech_ops/read.main/242986/

http://www.ablecomm.com/whdibeandhe.html

http://www.ehow.com/list_7382196_parts-headset.html