AC 43.13-1A Page 191 1972 FIGURE 11.14.-Bolt and nut bonding or grounding to flat surface.
- SCREW OR BOLT
WASHER A
WASHER B
LOCKWASHER
TERMINAL LIMITED TO 4
LOCKNUT WASHER C Aluminum Terminal and Jumper Etruoture Bores or Bolt and Hut plate Lookraaher Washer 1 Washer B Washer O Alaminum Alloy Cad. Plated Steel Cad. Plated Steel Cad. plated steel None Cad. plated or aluminum steel or aluminum Magnesium Alloy Cad. Plated Steel Cad. Plated Steel Magnesfum Alloy None or Cad. plated Magnesium steel or
• AllOy aluminum Steel, Oadmium Cad. Plated Steel Cad. Plated Steel Cad. Plated Steel Cadmium Cad. plated plated plated steel or ateel aluminum Steel, Corrosion Corrosion Resiat. Cad. Plated Steel Corrosion Resiat- Cadmium Cad. plated Resisting Steel or Cad. Ing Steel plated steel or plated steel steel aluminum Tinned Copper Terminal and Jumper Aluminum Alloy Cad. Plated Steel Cad. Plated Steel Cad. plated steel Aluminum Cad. plated aline ateol
Page 192 AC 43.12-1A 1972 CAD. PL. STEEL AN 735 CLAMP SCREW COPPER
TERMINAL
ALUMINUM
CYLINDRICAL WASHERS
SURFACE CAD. PL. STEEL
LOCKWASHER CAD. PL. STEEL
LOCKNUT FIGURE 11.15-Copper jumper connecter to tubular structure.
CAD. PL. STEEL SCREW AN 735 CLAMP WASHER ALUMINUM
• STRUCTURE _ ALUMINUM
ALUMINUM ALLOY WASHER OR CORROSION.
RESISTING STEEL CAD. PL. STEEL
CONDUIT LOCKWASHER CAD. PL. STEEL
LOCKNUT FIGURE 11.16.-Bonding condult to structure.
CAD. PL. STEEL SCREW AN 735 CLAMP
ALUMINUM WASHER
ALUMINUM
TERMINAL
AC 43.13-1A 1972 avoided, the choice of jumper and hardware should be such that corrosion is minimized, and the part likely to corrode would be the jumper or associated hardware. Figures 11.12 through 11.17 show the proper hardware combinations for making a bond connection. At locations where finishes are removed, apply a protective finish to the completed connection to prevent subsequent corrosion.
c. Bonding Jumper Attachment. Avoid the use of solder to attach bonding jumpers. Bond tu- Page 193 bular members by means of clamps to which the jumper is attached. Proper choice of clamp material will minimize the probability of corrosion.
d. Ground Return Connection. When bonding jumpers carry substantial ground return current, determine that the current rating of the jumper is adequate, and that a negligible voltage drop is produced.
453.-463. RESERVED.
Page 194 AC 43.13-1А 1972 Section 4. WIRE MARKING
464. WIRE IDENTIFICATION. To facilitate instal- 465. SLEEVE SELECTION FOR IDENTIFICATION.
lation and maintenance, original wire-marking identification is to be retained. The wire identi- a. Flexible vinyl sleeving, either clear or fication marking should consist of a combina- opaque, is satisfactory for general use.
tion of letters and numbers which identify the b. For sleeving exposed to high temperatures wire, the circuit it belongs to, its gauge size, and any other information to relate the wire to (over 400° F.), use materials such as silicone rubber or silicone fiberglas.
a wiring diagram. The preferred method is to stamp the identification marking directly on c. Use nylon sleeving in areas where resistthe wire. Place identification markings at each ance to solvent and synthetic hydraulic fluids end of the wire and at 12- to 15-inch intervals is necessary. The size of identification sleeving along the length of the wire. Wires less than & for the various sizes of wire are shown in inches long need not be stamped. Wire lengths fgure 11.18.
8 to 7 inches should be stamped at the center.
If the outer covering or wire insulation will FIGURE 11.18.-Sizes of identification sleeving.
not stamp easily, insulating tubing may be stamped with the identification mark and in- Wire Size Sleeving Bixe stalled on the wire. Identification sleeves are MIL-W-50в6 MIL- X7-9072 Nominal I.D.
normally used for identifying the following AN No. (inches) types of wire or cable: #24 12 .085
a. Unjacketed shielded wire. #22 #20 10 11 ,095 .106
b. Thermocouple wire. #18 .118 #16 .118
c. Multiconductor cable. #14 7 •148 # 12 .166
d. High temperature wire with insulation #10 4 .208 difficult to mark (such as asbestos, teflon, and #8 #8 2 .268 fiberglas). #6 #6 .380 #4 #4 8/8 Inch .875
(1) Thermocouple wire identification is nor- #2 #2 1/2 inch .500 mally accomplished by means of identification #1 #1 1/2 inch -500 sleeves. As the thermocouple wire is usually of #0 #0 5/8 inch .625 the duplex type (two insulated wires within #00 #00 5/8 inch -625 the same casing), each wire at the termination Doint bears the full name of the conductor #0000 #000 #000 #0000 8/4 Inch 8/4 inch .750 -750
AC 43.13-1A Роде 195 1972
PRESSURE -
SENSITIVE TAPE XYZ15
SLEEVE MARKER
TIED IN PLACE XYZ15 FIGURE 11.10.--Identification of wire bundles and harnesses.
467,-477. RESERVED.
Page 196 AC 49.13-1А 1972 Section 5. CONNECTORS 478, GENERAL PURPOSE CONNECTORS. Connec tors (plugs and receptacles) are used to facilitate maintenance when frequent disconnection is required. Since the wires are soldered to the connector inserts, the joints should be individually installed and the wire bundle firmly supported to avoid damage by vibration. Connectors have been particularly vulnerable to corrosion in the past, due to condensation within the shell. Special connectors with waterproof features have been developed and may be used may be pro to replace nonwaterproof type plugs in areas where moisture causes a connector problem.
Use a replacement connector of the same basic type and design as the connector it replaces.
Connectors that are susceptible to corrosion difficulties may be treated with a chemically inert waterproof jelly. When replacing connector assemblies, use the socket-type insert on that half which is live or "hot" after the connector is disconnected to prevent unintentional grounding.
479. TYPES OF CONNECTORS. Connectors are identified by AN numbers and are divided into types and classes with manufacturer's variations in each type and class. The manufacturer's variations are differences in appearance and in the method of meeting the specification;
however, they do not preclude mating plugs and receptacles of different manufacturers.
There are six basic types of AN connectors used in aircraft which are further broken down into five classes as indicated in figures it is important that the soldered connectors are readily accessible. The back shell is held together by a threaded ring or by screws.
Class C-A pressurized connector with inserts that are not removable. Looks like a Class A connector but the inside sealing arrangement is sometimes different and is used on walls of bulkheads of pressurized equipment.
Class D-Moisture and vibration resisting connector which has a sealing grommet in the back shell. Wires are threaded through tight fitting holes in the grommet, thereby sealing against moisture.
Class K-A fireproof connector used in areas where it is vital that the electric current is not interrupted, even though connector may be exposed to continuous open flame. Wires are crimped to the pin or socket contacts and the shells are made of steel, This class of connectors is normally longer than the other classes of connectors.
480. AN CONNECTOR IDENTIFICATION. Code letters and numbers are marked on the coupling ring or shell to identify the connector. This code provides all the information necessary to obtain the correct replacement for a defective or damaged part. To facilitate ready identification the code found on a typical connector (aa shown in figure 11.22) is explained as follows:
a. The letters AN indicate the connector was made to a onvarnment standard
AC 43.13-1А Page 197 1972 AN 3102 AN 3100 BOX RECEPTACLE WALL RECEPTACLE AN 3101
CABLE RECEPTACLE AN 3106 AN 3106 STRAIGHT PLUG AN 3107 STRAIGHT PLUG
QUICK DISCONNECT PLUG AN 3108 AN 3106
ANGLE PLUG ANGLE PLUG FIGURE 11.20.-AN connectors.
Page 198 AC 43.13-1A 1972
STANDARD AN 3106 CLASS TYPE NUMBER SIZE
INSERT ARRANGEMENT NUMBER
CONTACT STYLE
INSERT ROTATION FIGURE 11.22.-AN connector marking.
•. Number 4 indicates a certain arrangement of contacts; however, this number does not indicate the number of contacts. Manufacturers of connectors provide charts giving diagrams of the various contact arrangements.
f. Letter (s) indicates contact style. This letter may be either a (P) or (S) which indicates whether the contacts are pins or sockets.
g. A letter may or may not follow the contact ture connector, rectangular shell connector, connectors with short body shells or of split shell construction used in applications where potting is required.
482. POTTING COMPOUNDS, Potting compounds meeting Specification MIL-S-8516 are prepared in ready-to-use tube-type dispensers, or in the unmixed state consisting of the base compound and accelerator packed in paired
AC 43.13-1A 1972 to the base compound and includes the time expended during the mixing and application processes. Mixed compounds that are not to be used immediately must be cooled and thawed quickly to avoid wasting the short working life. Chilled compounds should be thawed by blowing compressed air over the outside of the container, Normally the compound will be ready for use in 5 to 10 minutes.
CAUTION Do not use heat or blow compressed air into the container when restoring to working tempersture.
483. POTTING CONNECTORS. Connectors that have been potted primarily offer protection against concentration of moisture in the SPARE SPARE
FILL ALL SPARE
CONTACTS WITH
MAXIMUM SIZE WIRES Page 199 connectors. A secondary benefit of potting is the reduced possibility of breakage between the contact and wire due to vibration.
Solder wires to all contacts of the connector prior to the application of the potting compound, Wires that are not to be used should be long enough to permit splicing at a later date.
Identify the wires not used as shown in figure
11.28 and cap the cut ends with potting compound prior to securing to the wire bundle.
After the soldering operation, scrape off the resin and wash the connector with clean stoddard solvent, brushing vigorously. Rinse the areas to be potted with methylene chloride and complete the potting operation within 2 hours after this cleaning. Allow the potting com-
- IDENTIFY SPARE WIRES
WITH CODE LETTER TO
CORRESPOND WITH CONTACT
pound to cure for 24 hours at a room temperature of 70° to 75° F. or carefully place in a drying oven at 100° F. for 3 to 4 hours.
484. THROUGH BOLTS. Through bolts are sometimes used to make feeder connections through bulkheads, fuselage skin, or firewalls. Mount through bolts in such a manner that they are mechanically secure and independent of the terminal nuts. Provide sufficient cross section to insure adequate conductivity against overheating and enough contact area to minimize voltage drop. Mechanically secure such bolts independent of the terminal mounting nuts, taking particular care to avoid dissimilar metals among the terminal hardware. During inspection, pay particular attention to the condition of the insulator plate or spacer and the insulating boot that covers the completed terminal assembly.
485. TERMINAL STRIPS. Wires are usually joined AC 43.13-1A 1972 at terminal strips. Use a terminal strip fitted with barriers to prevent the terminals on adjacent studs from contacting each other. Studs must be anchored against rotation. When more than four terminals are to be connected together, use two or more adjacent studs and mount a small metal bus across the studs. In all cases, the current is to be carried by the terminal contact surfaces and not by the stud itself. Replace defective studs with studs of the same size and material as terminal strip studs of the smaller sizes may shear due to overtightening the nut. Assure that the replacement stud is securely mounted in the terminal strip and that the terminal securing nut is tight.
Mount terminal strips in such a manner that loose metallic objects cannot fall across the terminals or studs. It is good practice to provide at least one spare stud for future circuit expansion, or in case a stud is broken.
486.-496. RESERVED.
AC 43.13-1A Page 201 1972 Section 6. CONDUITS
497. GENERAL, Conduit is available in metallic and nonmetallic materials and in both rigid and flexible form. Primarily, its purpose is for mechanical protection of the wire within, although some radio interference shielding may be provided.
498. SIZE OF CONDUIT, When selecting conduit size for a specific wire bundle application, it ia common practice to allow for ease in maintenance and possible future circuit expansion by specifying the conduit inner diameter about 25 percent larger than the maximum diameter of the wire bundle. The nominal diameter of rigid metallic conduit is the O.D. Therefore, to obtain the I.D., subtract twice the tube wall thickness.
499. CONDUIT FITTINGS, From the abrasion standpoint, conduit is vulnerable at its ends.
Affix suitable fittings to conduit ends in such manner that a smooth surface comes in contact with wire within. When fittings are not used, flare the end of the conduit to prevent wire insulation damage. Support the conduit using clamps along the conduit run.
as much a8 80 percent of the tube area. Minimum acceptable tube bend radii for rigid conduit is shown in figure 11.24. Kinked or wrinkled bends in rigid conduits are not considered acceptable. Tubing bends that have been flattened into an ellipse and the minor diameter is less than 75 percent of the nominal tubing diameter is not considered satisfactory because the tube area will have been reduced at least 10 percent. Carefully deburr tubing that has been formed and cut to final length to prevent wire insulation damage. When installing replacement tube sections with fittings at both ends, exercise care to eliminate mechanical strain.
502. FLEXIBLE CONDUIT. Flexible aluminum conduit conforming to Specification MIL-C-6186 is available in two types; Type I, Bare Flexible Conduit, and Type II, Rubber Covered Flexible Conduit. Flexible brass conduit conforming to Specification MIL-C-7981 is available and normally used instead of flexible aluminum where necessary to minimize radio interference. Flexible conduit may be used where it is impractical to use rigid conduit such as areas that have
500. CONDUIT INSTALLATION. Many of the past troubles with conduit can be avoided by proper Nominal Minimum bond attention to the following details: 1408 O.D. rodil (inches)
a. Do not locate conduit where passengers or maintenance personnel might use it as a handhold or footstep.
b. Provide drainholes at the lowest point in a conduit run. Drilling burrs should be carefully removed.
c. Support conduit to prevent chafing against structure and to avoid stressing its end fittings.
301. RIGID CONDUIT. Repair conduit sections that have been damaged to preclude injury to the wires or wire bundle which may consume FIoURE 11.24.-Bend radii for rigid condult.
Chap 11 Par 497
Pergo 202 motion between conduit ends or where complex bends are necessary. The use of transparent adhesive tape is recommended when cutting flexible tubing with a hacksaw to minimize fraying of the braid. Center the tape over the eut reference mark and saw through the tape.
AC 43.73-TA 1972 After cutting the flexible conduit, remove the transparent tape, trim the frayed ends of the braid, remove burrs from inside the conduit, and install coupling nut and ferrule. Minimum acceptable bending radii for flexible conduit is shown in fgure 11.25.
FIGURE 11.25.-Minimum bending radii for flexible aluminum or brass conduit.
Nominal I.D. Minimum bending of conduit radise ineido (Imohes) (Imoice)
393.-513. RESERVED.
Per 502 Chap 11