Aircraft Electrical Installation Hands On Workshop

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Gyles Griffin
6 years ago
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1 Aircraft Electrical Installation Hands On Workshop I. Introduction What we will cover in this presentation a. Aircraft electrical installation b. Materials c. Tools d. Techniques e. Recommended practices II. Qualifier a. For the Lawyers among us The Information discussed here does not supersede or replace government regulations or specifications or the manufacturers instructions III. AC B a. FAA Advisory Circular Publication documenting recommended techniques for aircraft maintenance and repair i. It is an advisory circular not a rule ii. Paragraph 11 and 12 deal with Electrical and Avionics b. How to get it i. You can download it free from the FAA ( use quick find search for advisory circulars then AC B ii. NOTE: It is a PDF file so you will need Adobe Reader ( if you don t already have it. iii. If you download it you will not want to print the whole document, it is several hundred pages long iv. Or you can buy a hard copy from most aviation book sellers or pilot shops IV. Wire - Auto and Marine vs. Aircraft wire a. Auto wire i. Is not usually tinned or plated with a corrosion resistant coating like tin, nickel or silver ii. Wire made for automobile applications often has PVC or vinyl insulation which will burn and produce poisonous fumes b. Marine wire i. Marine wire is usually tinned to inhibit corrosion but also usually uses PVC insulation c. Mil spec 5086A Wire (See Picture #1) i. Relatively thick PVC insulation ii. Finely stranded and tinned with tin, nickel or silver iii. Found in most aircraft produced until the late 1970 s iv. PVC insulation produces Cyanide when it burns and will support combustion d. Mil spec Wire (See Picture #2) i. Marking MIL-22759/ (number) (wire gauge) ii. Teflon or Tefzel insulation iii. Will not support combustion and does not generate poisonous fumes when exposed to flame iv. Is always finely stranded v. Is always tinned with tin, nickel or silver making it highly corrosion resistant vi. Table Open Wiring in page Par page (See Page 11) e. Kapton Wire (See Picture #3) i. BAD NEWS DO NOT USE! ii. Plentiful and cheap on the surplus market because it is being removed from commercial and military aircraft as fast as they can economically get it out. iii. Cracks rapidly with age and burns like primercord when it gets lit iv. Several air carrier and military inflight fires and crashes have been traced to Kapton wire V. Wire Stripping Tools Page 1

2 Aircraft Electrical Installation Hands On Workshop a. Knife or Chisel type (See Picture #4) i. Make a good tack hammer (not a good aircraft wire stripper) ii. Extremely easy to damage wire b. Ring Die type (See Picture #5) i. Ideal Tool Co. Stripmaster or Custom Stripmaster ii. Ring Die type come in several varieties iii. Be careful of the surplus strippers designed for Kapton wire! the relief for the insulation is smaller because of the thinner insulation on Kapton wire and will not work well on wire iv. The dies are changeable in Stripmasters VI. Terminating and Splicing a. Crimping vs. Soldering i. Solid wire is highly susceptible to damage from vibration ii. Houses do not vibrate (much), this is why house wiring is solid or has very large strands iii. Aircraft wire is very finely stranded to make it vibration damage resistant iv. Soldering makes it a solid wire for an indeterminate distance beyond the soldered joint or terminal v. A termination using the correct type of crimp terminal crimped with the correct crimper is the most reliable and longest lasting connection for a wire in an aircraft application b. Crimp Terminals Automotive vs. Aircraft (See Picture #6) Crimp terminals for auto use Amp calls them Plastigrip Crimp terminals for aircraft use Amp calls them Pre Insulated Diamond Grip or PIDG Use Vinyl insulation Always use Nylon insulation Do not have a metal insulation grip Have a metal sleeve for insulation grip Do not have a brazed barrel for the wire grip Have a brazed or soldered barrel for the wire grip grip VII. Crimping Tools (See Picture #7) VIII. a. Crimp depth is important so the wire isn t damaged in the crimping process b. The wire grip and insulation grip must both be crimped at the same time for a proper termination c. Tack hammers do not give predictable crimp depth and crimp one grip area at a time d. Ratcheting dual die crimpers give a predictable crimp depth and crimp both the insulation grip and the wire grip at the same time to the correct depth Coaxial Cable a. RG-58/(letter) (See Picture #8) i. Has black PVC insulation, stranded inner conductor with clear nylon or polyethylene insulation ii. Cheaper versions of this cable (CB Cable) are not tinned and have a bare copper outer braid and are highly susceptible to corrosion iii. Is fine cable other than the PVC burning thing until it gets about 5 to 7 years old iv. Gets brittle with age and begins cracking and absorbing moisture v. Coaxial cable is used in systems where constant impedance for the length of the cable is vital. When it absorbs moisture it changes the impedance of the cable in the area where moisture is absorbed Page 2

3 Aircraft Electrical Installation Hands On Workshop b. RG-400 cable (See Picture #9) i. RG 58 has been superseded by RG 400 which is a much higher performance cable ii. Has translucent gold colored Teflon insulation, silver tinned double outer braid and stranded tinned inner conductor with Teflon insulation iii. Silver tinned outer braid and inner conductor make RG 400 highly corrosion resistant iv. Does not become brittle or crack with age due to Teflon insulation v. Is slightly more expensive but very much worth it for airborne applications c. Coaxial Cable Termination i. All connectors made for RG 58 will fit RG 400. ii. Crimp connectors are the preferred connectors for our aircraft applications iii. Crimp connectors are easier to attach properly and are more vibration resistant than clamp type that screw together iv. Most good quality connectors (Amphenol) have a stripping dimension diagram on the package (See Picture #10) v. The hole in the center pin is NOT for soldering in a crimp type connector it is a view hole to verify that the center conductor is bottomed in the pin vi. A good quality crimper for these connectors can be purchased for less than $25 vii. Buy some extra connectors and cable, you will need to practice IX. Wire Support & Securing a. Ty Wraps i. Come in many varieties not all of which are appropriate for aircraft use ii. Vinyl vs Nylon and telling the difference iii. Metal tab vs plastic tab iv. Limitations in high heat areas v. Minimize blood loss, use flush cutting side cutters to cut off the tails b. Lacing Cord i. Better than Ty Wraps because it is easier on the wire. ii. Comes in several varieties, waxed, unwaxed, nomex for hot areas etc iii. Bundle lacing shown in AC is good but has drawbacks when maintenance or modification is required it all comes unraveled! iv. The skilled technicians at NASA have a better way, this knot as been used on military aircraft, ships and spacecraft for many years v. (See Picture # 11) Here is the knot on the wiring bundles on a Gemini space capsule, the entire wiring harness on the capsule is tied up with this knot vi. The knot I am going to show you takes the place of individual Ty Wraps (See Picture #12) vii. More info on the lacing tape here c. Clamps i. Adel Clamps MS 2919-XX-X ii. (See Page 12 of 13) iii. General Color code: black or darker color is for cool and/or less chemically threatening areas and red, orange or yellow is for hot and/or more chemically threatening areas iv. Nylon Clamps not for hot areas v. Same caution applies as for nylon and vinyl Ty Wraps vi. Spacing Page 3

4 X. Wire Bundle Routing Aircraft Electrical Installation Hands On Workshop a. Separate Noisy Bundles from Quiet ones i. Route high current (flap and landing gear motors, landing lights, starters etc.) or noise producing (strobes) circuits as far as possible away from instrumentation, audio and data circuits ii. Six inches is good but farther is better b. Crossing Angle i. If you have to cross an audio, instrumentation or data cable with a high current or noisy circuit do it at 90 degrees ii. This minimizes the electrical coupling between the two circuits c. Pay attention to where wiring is in relation to liquid lines (especially fuel) i. Route wiring ABOVE fuel or other liquid lines so if the lines leak they will not leak on the wires ii. Do not secure wiring to liquid lines XI. Wire Protection a. Strain relief and environmental protection i. Heat shrink tubing is great but has some limitations ii. Regular heat shrink can actually trap moisture under it iii. Special types of heat shrink are available with gel inside to make it waterproof iv. Most inexpensive heat shrink is PVC which can burn and make cyanide gas v. Heat shrink specifically for aircraft use is made from Polyolefin vi. Protect sharp edges with chafe protection (See Picture #13) vii. Give yourself service loops at the ends of wires XII. Wire Marking XIII. a. Do yourself a favor, mark everything so you can find it later i. Mark both ends of a circuit and if it is a long one every 3 or so feet along the way if it is accessible ii. White heat shrink with lettering by ball point pen or fine point sharpie works great iii. Clear heat shrink with paper underneath for marking is also slick way to do this b. Dymo, Brother and Brady make inexpensive (<$75) label makers that work great for this i. Oil and moisture resistant label tape is available for these ii. These are commonly used for data network cable labeling iii. Get one that can print in wrap format so it can be wrapped around the wire THE END a. That s all Folks! Come on up and try what I just showed you Page 4

5 Pictures from Slide Show Picture #1 Picture #2 Picture #3 Picture #4 Knife or chisel type stripper Picture #5 Ring die type stripper Page 5

6 Pictures from Slide Show Picture #6 Picture #7 Page 6

7 Pictures from Slide Show Picture #8 Picture #9 Picture #10 Picture #11 Page 7

8 Pictures from Slide Show Picture #12 Wire Tying Knot (Way better than a Ty-Wrap!) PLACE LOOP BEHIND BUNDLE Step 1 WIRE BUNDLE PULL LOOP FROM SPOOL SIDE IN FRONT OF BUNDLE THROUGH FIRST LOOP Step 2 WIRE BUNDLE PULL LOOSE END IN FRONT OF BUNDLE THROUGH SECOND LOOP AND PULL TIGHT Step 3 WIRE BUNDLE HOLD SPOOL AND PULL TIGHT Step 4 HOLD SPOOL AND PULL TIGHT PULL TIGHT WIRE BUNDLE Page 8

9 Pictures from Slide Show Picture #13 Page 9

10 AC B CHG 1 9/27/01 TABLE Open Wiring. Document Voltage rating (maximum) Rated wire temperature ( C) Insulation Type MIL-W-22759/ Fluoropolymer insulated TFE and TFE coated glass MIL-W-22759/ Fluoropolymer insulated TFE and TFE coated glass MIL-W-22759/ Fluoropolymer insulated TFE -glass- TFE MIL-W-22759/ Fluoropolymer insulated TFE -glass- FEP Conductor type Silver coated copper Nickel coated copper Nickel coated copper Silver coated copper MIL-W-22759/ Fluoropolymer insulated extruded TFE Silver coated copper MIL-W-22759/ Fluoropolymer insulated extruded TFE Nickel coated copper MIL-W-22759/ Fluoropolymer insulated extruded TFE Silver coated copper MIL-W-22759/ Fluoropolymer insulated extruded TFE Nickel coated copper MIL-W-22759/ Fluoropolymer insulated extruded TFE Silver coated copper MIL-W-22759/ Fluoropolymer insulated extruded TFE Nickel coated copper MIL-W-22759/ Fluoropolymer insulated FEP PVF2 Tin coated copper, MIL-W-22759/ Fluoropolymer insulated extruded ETFE MIL-W-22759/ Fluoropolymer insulated extruded ETFE Tin coated copper, Silver coated high strength copper alloy MIL-W-22759/ Fluoropolymer insulated extruded TFE Silver coated high strength copper alloy MIL-W-22759/ Fluoropolymer insulated extruded TFE Nickel coated high strength copper alloy MIL-W-22759/ Fluoropolymer insulated crosslinked modified ETFE Tin coated copper MIL-W-22759/ Fluoropolymer insulated crosslinked modified ETFE MIL-W-22759/ Fluoropolymer insulated crosslinked modified ETFE MIL-W-22759/ Fluoropolymer insulated crosslinked modified ETFE MIL-W-22759/ Fluoropolymer insulated crosslinked modified ETFE Silver coated high strength copper alloy Nickel coated copper Nickel coated high strength copper alloy Silver coated copper MIL-W-25038/3/2/ See specification sheet * See specification sheet MIL-W-81044/ Crosslinked polyalkene Tin coated copper MIL-W-81044/ Crosslinked polyalkene Silver coated high strength copper alloy MIL-W-81044/ Crosslinked polyalkene Tin coated copper MIL-W-81044/ Crosslinked polyalkene Silver coated high strength copper alloy * Inorganic Fibers - Glass - TFE Page Par 11-89

11 Adel Clamps Everything you ever wanted to know but were afraid to ask by Bob Nuckolls I've seen some conversation recently concerning "Adel" clamps and their suitability for use around fuel, high temps, etc. I've pulled the specs and will excerpt some of their contents as follows: The "Adel" clamp is more properly called an MS21919 aircraft clamp. The company named Adel built a goodly portion of the MS21919 clamps back in the 60's (and may still). The term sort of stuck on these devices in spite of the fact that they are now made by dozens of companies. The full description for these clamps follows the convention MS21919WXXZZ where: W = "wedge" feature in cushion that helps prevent escape of small wires out of cushion. Virtually all new production of MS21919 clamps below size 50 have the wedge feature... XX characters have the following significance: DE = Aluminum band, Ethylene Propylene Cushion (212F) DF = Aluminum band, Nitrile Cushion (212F) DG = Aluminum band, Chloroprene Cushion (212F) CE = Corrosion Resistant Steel band, Ethylene Propylene Cushion (275F) CF = Corrosion Resistant Steel band, Nitrile Propylene Cushion (200F) CH = Corrosion Resistant Steel band, Silicone Cushion (400F) CG = Corrosion Resistant Steel band, Chloroprene Cushion (212F) CJ = Corrosion Resistant Steel band, Fluorosilicone Cushion (450F) F = Low Carbon Steel Band, Nitrile Cushion (212F) G = Low Carbon Steel Band, Chloroprene Cushion (212F) H = Low Carbon Steel Band, Silicon Cushion (400F) CAUTION - Clamps with low carbon steel bands are not recommended for new design and most were purged from stocks back in early 80's, however, you never know what might show up in the Fly-Market at OSH so I've included the "heads up" here. Cushion Application and Color Information: Ethylene Propylene - for use in areas contaminated with phosphate- ester hydraulic fluid and other synthetic fluids. Excellent ozone resistance., Not resistant to petroleum based fluids. Color shall be solid purple. Nitrile - for use primarily in fuel immersion and fuel vapors. Good ozone resistance. Not resistant to phosphate-ester based fluids. Not for use on titanium tubing. Color shall be solid yellow. Chloroprene - for general purpose use in areas contaminated with petroleum based hydraulic fluids and occasional fuel splash. Excellent ozone resistant. Not resistant to phosphate-ester based fluids. Not for use on titanium tubing. Color shall be black with a blue identifier patch. Silicone - for elevated temperature usage in phosphate-ester based fluid and other synthetic fluid contaminated areas. Unaffected by ozone. Not resistant to petroleum based fluids. Color shall be natural white. Fluorosilicone - for elevated temperature usage in petroleum based fluid contaminated areas. Unaffected by ozone. Not resistant to phosphate-ester based fluids. Color shall be solid blue. Silicone - RED now obsolete and used only on the low carbon Steel Page 11

12 Adel Clamps Everything you ever wanted to know but were afraid to ask by Bob Nuckolls The last characters (ZZ) are digits describing the internal diameter of the closed clamp in 1/16ths of an inch. E.G. an MS21219WDG4 is aluminum strap inside a chloroprene cushion and sized to support 1/4" diameter bundle of wires, tubing, etc. I note that the spec does not speak to the "red" cushions currently being discussed. I recall seeing a number of clamps with red cushions over the years but quite frankly, I don't know if they were MS21919 or perhaps some other part number. UPDATE: All of the "reds" have been purged from Raytheon's stocks, couldn't even find one in the junk boxes that I had access to. Mr. Sobek says the one he found does carry the part number MS21919H** which tells us it is indeed the obsolete, low carbon steel version and silicon rubber (not recommended for use where "wet" with hydrocarbons. Page 12

13 Sun & Fun Hands On Workshops Vendor Website or Physical Address Phone # Content Aeroelectric Connection Excellent articles and guides for wiring your airplane Amateur Electronic Supply Online Amateur Radio and Electronic Supplies Amateur Electronic Supply Orlando Retail Store 621 Commonwealth Ave. Orlando, FL Amateur Radio and Electronic Supplies B & C Specialty Products D-Sub, PIDG, Coax and Molex Crimpers, Ideal Strippers Contact East/Jensen Tools (Stanley Supply Services) Commercial Electronics Tools, Test Equipment Digi Key Corp Commercial Electronics Distributor, Tools, Test Equipment Edmo Distributors Major Avionics Supplies Distributor Ideal Industries (Stripmaster Manufacturer) Parts for Ideal Stripmaster Stripper Tools Matronics Inc Kitbuilding Electrical Advice and Supplies Mouser Electronics Commercial Electronics Distributor, Tools, Test Equipment Skycraft Surplus Online Store skycraftsurplus.com Wire and Surplus Tools Skycraft Surplus Orlando Retail Store 2245 West Fairbanks Ave. Winter Park, FL Wire and Surplus Tools Specialized Products Commercial Electronics Tools, Test Equipment Techni-Tool Commercial Electronics Tools, Test Equipment Useful Links Aeroelectric Links Page of useful links to kitbuilding and electrical suppliers Direct Link to FAA Website to download AC B Gudebrod (Carwild) Lacing Tape Website where you can get the presentation from this workshop Page 13

Bob's Shop Notes: Alternatives to RG58 in Lightspeed Ignition Wiring

1 of 9 8/12/2003 7:48 PM Bob's Shop Notes: Alternatives to RG58 in Lightspeed Ignition Wiring Instructions for the popular and capable electronic ignition system from Lightspeed recommends RG58 coaxial