Sandy

About Sandy
Sandy

Nuts and bolts and anything in between. Yeah, I know plenty about fixing aircraft. I aim to be the best mechanic. Hanging out all day in a hangar sounds like a perfect use of my time. You got questions pertaining to maintenance and repair? Ask away and I’ll have you flying high. If not, check some of my posts for tips or suggestions on what parts and supplies work best.

SpaceTEC’s Overview on Screwdrivers and Screw Heads

Greetings, avgeeks!

I received some encouraging feedback from my last post about SpaceTEC so I figured I would serve up another helpful short clip. Instead of safety wires, this brief guide covers the basics about screwdrivers:

Of all hand tools, screwdrivers are among the top in terms of popularity and usefulness. And yet they are not complex devices that require a PhD. As SpaceTEC states as a running footer in the above clip, screwdrivers offer simplicity when it comes to applied mechanics; they are made for the sole purpose of loosening or tightening screws. Nothing hard to understand there.

Search for a screwdriver and your head might get all twisted up since there are a variety of types—everything from slotted to jewelers. So how in the heck do you choose what is right for your application or assemblage?

According to SpaceTEC, screwdrivers are “classified by shape, type of blade, and blade length.” They recommend selecting the largest blade (or bit) that will fill the screw head. This makes sense. Why? If you’ve ever tried to fit too large of a bit into the head, you know that it obviously won’t work. Neither will trying to place a bit too small into the screw head. They won’t fill in the hollow correctly. They also won’t effectively turn the screw. Instead, a bit that is too small or too large for a socket will warp and misshape the screw head so that the right blade won’t even work. Oh, and it can even damage the bit itself. Talk about a frustrating and costly blunder.

The two most well-known screwdrivers are the straight/common/ flathead (which fit with slotted head screws) and Phillips head (which fit in heads that form perfect crosses). There’s also offset screwdrivers that have a Z-shape and are composed of two right angles that are designed for use in hard-to-reach areas. Offset screwdrivers can have tips that are either common or Phillips or both.

To select an appropriate screwdriver the main issue revolves around the screw head. Therefore it is really the screw that determines how to select the right driver. SpaceTEC lists nine screw heads, which are briefly identified below:

Slotted – The most basic type. Can’t get any simpler than this design and in fact it is probably the oldest and cheapest to make. A straight vertical or horizontal (depending on your position) line down the middle of the head.

Phillips – Perhaps the most famous. Try and not find this type of screw head. It’s certainly a household screw. Its cruciform shape allows for better torque.

Pozidriv – Nope, that is not a misspelling; the Pozidriv (which may or may not be derived from the term “positive drive”) is another cruciform type head. However, it almost looks like it is a “bloated” cross, i.e. kind of widened in the mid-section. An advantage over its predecessor: it has straight flanks as opposed to the round flanks of Phillips. This helps prevent what is referred to as “cam out,” i.e. that accidently and incredibly frustrating time when the screwdriver slips out of the screw head.

Torx – Also known by its less appealing, technical name “hexalobular.” This recess is designed to resemble a star with six points. This allows for greater torque while resisting the tendency to cam out. That results in less fatigue on your hand but also prolongs the life of the bit on your screwdriver.
screw-heads

Hex – Short for hexagon, it has a six-sided polygonal shape. It is specially designed for use with Allen wrenches (or “keys”). The advantage here comes with size: Allen keys can fit and rotate in smaller areas where other screwdrivers can’t.

Robertson – A good way to know this screw head’s advantage is by remembering this: “Robertson retains.” It has a square-shaped socket (indentation or recess). Its tapered design offers reduced cam out and product damage while speeding up production. This type of head is used prominently in Canada.

Tri-wing – As the name indicates, this screw head has a triangular recess with three wings extending from the vertices of the triangle. This socket was particularly designed for use in aeronautics but has since been extensively used for electronics equipment in other industries.

Torq-set – Another cruciform. Don’t adjust your glasses, this socket looks similar to a Phillips head but something seems off. Actually, that’s it—while it has a cross-shape, the “arms” are offset as if the lines were broken up. Thus, a Phillips screwdriver will not fit. This screw head is used in aviation.

Spanner – This screw head consists of two round holes that look like a pair of eyes. This design’s main purpose is to prevent tampering.

If you’re an avgeek, chances are you already know about screwdrivers and screws. Still, brains are like machines. Just as machines often need to be well-oiled, frontal lobes need lube in the form of learning and re-learning. Reinforcement is, after all, a major component in keeping things structurally sound and operational.

SpaceTEC’s Take on Safety Wire

Is it the red or the blue wire? Careful, if you cut the wrong one your ashy remains will be found after the dust settles from a mushroom cloud explosion…

Greetings, geeks! I haven’t posted in a while so figured I would. I’ve had safety wire on my mind lately so I decided to search the Interwebs for anything that would serve as a quick guide or at least a refresher. What I found was a nice short video from SpaceTEC:

“Safety wiring is considered a redundant means of securing components to prevent them from becoming loose, should the primary retention capability fail during operation.” That is what the first screen of the video says. ‘Redundant’ used in this context does not mean something negative; SpaceTEC is not talking about overusing words in a five-page paper in English class. Here, redundant simply refers to the purpose of safety wiring; it acts as an additional and precautionary measure so that parts, most often hardware, remain intact. When it comes to securing fasteners (nuts, bolt, screws, etc.) and preventing vibrational forces from loosening parts, safety wire is a reliable and inexpensive means that leads to peace of mind.

The next screen from the above video states: “Items shall be safety wired in such a configuration that the safety wire shall be put in tension when the parts tend to loosen.” The screen displays two images—illustrations of a safety wire installed on bolt-heads and safety wire used on Castle nuts. This serves as a nice visual aid to give you an idea of the appearance of the configuration. Such a configuration allows for the safety wire to act as an antagonist to the part, meaning as the nut loosens, the wire tenses up. It is similar to how muscles function: as one muscle expands or extends, a corresponding muscle contracts. Imagine if both muscles contracted at the same time? Snap! Well, if a safety wire loosens while a part loosens, it defeats the whole purpose of the configuration.

The third screen retains the two images from the previous screen. But now Aircraft Circular AC 43.13-1B is mentioned. “AC 43.13-1B covers all the aspects of general safety wire practices. There are three common sizes: 0.020, 0.032, 0.041. New safety wire shall be used for each application.” Check out Pages 19-25 of the Aircraft Circular AC43.13-1B where the FAA provides guidelines for “safetying.”

For the fourth and final screen of the video, safety wire pliers are briefly touched upon, particularly how they should be used to apply the wire: “Safety wire should be twisted six to eight turns per inch. The pigtail S/B 1/4 to 1/2-inch (three to six twists).” A picture illustrates this point.

For those who don’t know, SpaceTEC —located in Cape Canaveral, Florida— is the National Science Foundation’s (NSF) Resource Center. Its primary mission is to serve as an advocate for employing aerospace technicians. The organization achieves this by providing an academic outlet for such individuals. This leads to a well-trained workforce for commercial, civil, and defense space activities relating to the aerospace and aviation communities.

According to SpaceTEC: “Its certification programs offer performance-based examinations that result in industry-driven nationally recognized credentials that reflect the competencies employers demand. The certification program is offered through a nation-wide consortium of community and technical colleges, universities, business and industry organizations, and government agencies.”

The good news is that SpaceTEC recently received a grant renewal from the NSF; this was accomplished through the NSF’s Advanced Technical Education (ATE) program. This will certainly help with further developing the certificate program, which consists of five key areas – Applied Mechanics, Basic Electricity, Industrial Safety, Materials & Processes, and Tests & Measurements.

Thanks to SpaceTEC for offering a quick reference for the applied mechanics of safety wire.

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

SkyGeek and Sky-Tec: A Good Fit

Without an engine, you’re grounded. Without a starter, your engine is next to useless—unless you want a really heavy paperweight.

Sky-Tec Logo New

Ladies and geeks, start your engines…with Sky-Tec

Speaking of weight, when considering what starter to choose for your aircraft’s engine, you want something lightweight yet powerful enough to get you going all the way to your destination. Ultimately, you can’t begin your journey without a starter. The people at Sky-Tec seem to be on board with this sentiment.

In aviation you don’t want to carry anything that helps gravity out. You also don’t want to make your power source work harder than it has to in order to compensate for unnecessary weight, especially when that weight comes from the power source itself. Sky-Tec aims to apply the idea of “FlyweightTM” to engine starters and we’re eager to promote such ingenuity.

As a company consisting of everyday, regular, self-described “plane folk,” Sky-Tec cares about what they make by making it their business to know starters inside and out. SkyGeek is proud to partner up with them so that pilots around the country and around the globe, whether it’s for business or for pleasure, can begin taking flight without worrying about frequent maintenance, warranty issues, and/or an affordable replacement of their aircraft’s starter.

When deciding to team up with Sky-Tec, SkyGeek wanted to make sure their products were of a superior quality. After all, if we want to continue to provide our customers with excellent service and support we need to sell them products that are reputable and reliable and are in demand because of their quality. Based on our research, Sky-Tec has not only matched that expectation, but we have found that their people (real people, not automated messages) strive to exceed said expectations. Sky-Tec starters are used exclusively by all new aircraft manufacturers world-wide. Their starters continue to be the number one selling aftermarket replacement starter world-wide as well. In a word: Impressive.

You may be asking yourself, “Why all the praise?” SkyGeek sells thousands of Lycoming and Continental engine-related parts so naturally Sky-Tec starters fit in just nicely. Here’s a little breakdown of the key advantages these starters offer and why we’re so energized to sell them.

Feeds and Speeds

What do you get when you join sound engineering with technology that allows for the integration of lightweight materials? Answer: starters offering faster starts. Faster spinning ensures the quickest possible start and minimizes electrical system stress and mechanical wear. In addition, low current draw and highly efficient motor designs not only make for prompt starts, but minimum wear on airframe and engine components as well. What more could you ask for?

Higher Torque

Certainly if you were given the option between low or high, you would choose high torque. More torque gives you better rotational force that generates the juice you need in less time.  Through selective gear reduction methods, Sky-Tec starters are engineered to provide optimum starting torque, optimum cranking speed, and thus the most reliable start. Better efficiency and optimized designs, once again, yield better starts for the life of your engine—and beyond.

Rugged, Tough and Durable

HTC

Rough, tough, and hard to bluff on the HT starter’s durability.

Affordability (See below) of aircraft parts is what we all desire but not if it comes at the cost of quality and value. Sky-Tec doesn’t believe these factors are mutually exclusive. By considering total cost of ownership as a major issue, Sky-Tec’s engineers design starters with durability as their defining feature. For instance, the FlyweightTM LS/PM series starters are designed for minimum cost while still offering reliability that exceeds engine TBO. Tough, rugged construction highlights the HT series but weighs just half a pound more than the FlyweightsTM. And the NL’s unmatched efficiency and cranking torque cost even less with half a pound sacrificed to provide the industry’s best reliability. These features are exactly what you want in parts that are so critical to engine performance. Remember, durability stretches the dollar by nearly eliminating costs associated with maintenance and repair.

Affordability

And speaking of costs…Pound for pound, dollar for dollar, Sky-Tec’s full line of Lycoming and Continental starters is little more expensive and in some cases less expensive than heavier, older competitive designs that often ship with 25 or 50 hour maintenance requirements. Sky-Tec starters require zero maintenance and are fully supported by a 2-year factory warranty. Those same “plane folks” we spoke of are always available to help you with warranty, troubleshooting, and very affordable factory rebuilding services at costs comparable or in many cases less than rebuilding an old heavyweight starter.

NL

The NL starter: Popular and dependable.

Kickback Protection System

Many Sky-Tec starters now contain the exclusive Kickback Protection SystemTM (KPS), including the company’s #1 seller, the NL series, as well as HT and ST2-series starters. The KPSTM addresses the issue of kickback, i.e. when premature ignition misfire occurs. This system reduces damage to the starter and ring gear either by using a shear pin (NL-series starters) or self-resetting overtorque clutch (HT-series and ST2-series). Once again, Sky-Tec’s engineers have built in a safety feature that promises to maximize the life of your starter and the cash or credit in your wallet.

Lightweight Design and Construction

We realize we’ve mentioned this before but it cannot be emphasized enough: Sky-Tec engineers have designed lightweight starters that cannot be beaten. Evidence of this fact? Sky-Tec recently announced the lightest weight Lycoming starter available in the industry in 2013—the ultra lightweight XLT. Competitors may often lean on outmoded mechanical centrifugal devices; however, Sky-Tec engineers implement simple, affordable technology. This is proven in one crucial way. While inefficient Bendix drives are still in use by some manufacturers, Sky-Tec uses only lighter weight and more reliable electro-mechanical engagement drives. Customers can rejoice because simple, affordable technologies translate to affordable end products.Those that exemplify lightweight design without compromising power can be found not only in the newly announced XLT series Lycoming starters but also in Sky-Tec’s full line of top selling FlyweightTM LS & PM series starters—all available from SkyGeek.

LS

The Flyweight™ LS starter. Not quite light as a feather but the closest thing to it on the market.

Combine SkyGeek’s expedient shipping and desire to maintain customer satisfaction on every transaction with Sky-Tec starters and you can see that just as a starter and engine work together, SkyGeek and Sky-Tec make a good fit.

Find our entire stock of Sky-Tec products here.

We want our customers to get what they want so let us know how we are doing. Strike up the conversation in the comments section and be sure to review the products you buy.

As always, keep your eyes skyward.