Aircraft Inspection, Repair & Alterations: Acceptable Methods, Techniques, & Practices (FAA Handbooks)

Contents
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Effects of Shrinkage.  When the moisture content of a wooden part is lowered, the part shrinks.  Since the shrinkage is not equal in all directions, the mechanic should consider the effect that the repair may have on the completed structure.  The shrinka......Page 35
Adhesives acceptable to the FAA can be identified in the following ways:......Page 37
Phenol-formaldehyde adhesive is commonly used in the manufacturing of aircraft grade plywood.  This product is cured at elevated temperature and pressure; therefore, it is not practical for use in structural repair.......Page 38
PREPARATION OF WOOD SURFACES FOR BONDING.  It is recommended that no more time than necessary be permitted to elapse between final surfacing and bonding.  Keep prepared surfaces covered with a clean plastic sheet or other material to maintain cleanliness......Page 39
Pressing (or clamping) time is the period during which the parts are pressed tightly together and the adhesive cures.  The pressing time must be sufficient to ensure that joint strength is adequate before handling or machining the bonded structure.......Page 40
The size of the nails must vary with the size of the members.  If multiple rows of nails are required, the nails should be 1€inch apart in rows spaced 1/2€inch apart.  The nails in adjacent rows should be staggered.  In no case should the nails in adjace......Page 41
Immediately after clamping or nailing a member, the mechanic must examine the entire joint to assure uniform part contact and adhesive squeeze-out.  Wipe away excess adhesive.......Page 42
Proper shop ventilation is essential to disperse fumes emitted from adhesives such as resorcinol and epoxy.......Page 43
INSPECTION METHODS.  Whenever possible, the aircraft should be kept in a dry, well-ventilated hangar, with all inspection covers, access panels, etc., removed for as long as possible before final inspection.  The aircraft should be given a preliminary in......Page 45
Check front and rear spars for longitudinal cracks at the ends of the plywood reinforcement plates where the lift struts attach.  Triple-check this area if the wing has encountered any kind of ground strike.......Page 46
The usual locations for cracks have been the front spar at both ends of the reinforcement plate for the lift strut and the front spar rib attach points, both inboard and outboard of the spar reinforcement plate; and the rear spar lift strut and rib attac......Page 47
Destructive testing of sample bonded joints whenever a new bond joint is made, a sample joint should be made with the adhesive from the same batch used on the repair and scraps of wood left over from the repair.  After curing, the sample joint should be......Page 48
SCARF JOINTS.  The scarf joint is the most satisfactory method of making an end joint between two solid wood members.  Cut both parts accurately.  The strength of the joints depends upon good joint design and a thin, uniform bond line.  Make the scarf c......Page 49
SPAR LONGITUDINAL CRACKS AND LOCAL DAMAGE.  Cracked spars (except box spars) may be repaired by bonding plates of spruce or plywood of sufficient thickness to develop the longitudinal shear on both sides of the spar.  Extend the plates well beyond the te......Page 50
Longitudinal Cracking of Wood Wing Spars of Aircraft Operating in Arid Regions.  Aircraft having wood spars and operating in arid regions may develop longitudinal spar cracks in the vicinity of the plywood reinforcement plates.  These cracks result from......Page 51
RIB REPAIRS.  Ribs may be replaced by new parts made by the manufacturer or the holder of a PMA for that part.  Owner-produced ribs may be installed providing they are made from a manufacturer-approved drawing or by reference to an existing original rib.......Page 52
Figure€112(A) illustrates the repair of a compression rib of the “I” section type; i.e., wide, shallow cap strips, and a center plywood web with a rectangular compression member on each side of the web.  The rib is assumed to be cracked through the cap......Page 53
DETERMINATION OF SINGLE OR DOUBLE CURVATURE.  Much of the outside surface of plywood aircraft is curved.  On such areas, plywood used for repairs to the skin must be similarly curved.  Curved skins are either of single curvature or of double (compound) c......Page 54
REPAIRS TO SINGLE CURVATURE PLYWOOD SKIN.  Repairs to single curvature plywood skin may usually be formed from flat plywood, either by bending it dry or after soaking it in hot water.  The degree of curvature to which a piece of plywood can be bent will......Page 55
REPAIRS TO DOUBLE CURVATURE PLYWOOD SKIN.  The molded plywood necessary for a repair to a damaged plywood skin of double curvature cannot be made from flat plywood unless the area to be repaired is very small or is of exceedingly slight double curvature;......Page 56
Use waxed paper or plastic wrap, (cut larger than the size of the patch) between the patch and the plywood pressure plate.  This prevents excess adhesive from bonding the pressure plate to the skin.  Center the pressure plate carefully over the patch.......Page 59
Use waxed paper or plastic wrap to prevent bonding of the backing block to the skin.......Page 60
Steps in making an oval plug patch are as follows:......Page 61
Explore the area about the hole to be sure it lies at least the width of the oval......Page 62
FABRIC PATCH.  Small holes not exceeding 1€inch in diameter, after being trimmed to a smooth outline, may be repaired by doping a fabric patch on the outside of the plywood skin.  The edges of the trimmed hole should first be sealed, and the fabric patch......Page 65
Sawdust, shavings, and chips must be removed from enclosed spaces before they are sealed off by replacement of skin.  A vacuum cleaner is useful for such cleaning.......Page 68
Exposed end grain includes such surfaces as spar butts, skin edges, areas around vent holes, inspection holes, fittings, and exposed scarfed or tapered surfaces.......Page 69
SEALING OF BOLT HOLES.  Bolt holes in wooden structure provide a vulnerable entry point for moisture.  Variations in moisture content around bolt holes can lead to decay or splitting.  In addition, excessive moisture at bolt holes promotes corrosion of t......Page 70
Installation.  Initial installation of polyester fabric is similar to natural fabric.  The fabric is installed with as little slack as possible, considering fittings and other protrusions.  It may be sewn into an envelope, installed as a blanket, or inst......Page 72
PREPARATION OF THE STRUCTURE FOR COVERING.  One of the most important items when covering aircraft is the proper preparation of the structure.  Before covering, the airframe must be inspected and approved by a FAAcertified mechanic or repair station.......Page 73
Worn Holes.  Oversized screw holes or worn size€4 selftapping screw holes through ribs and other structures used to attach fabric may be redrilled a minimum 11/2€hole diameter distance from the original hole location with a #€44 (0.086) drill bit.  Si......Page 74
Small metal or wood surfaces, such as rib caps, to which fabric will not be dope bonded as a part of the particular fabric attachment procedure may be protected from dope damage by cellophane tape or aluminum foil.......Page 75
Machine-sewn seams should be double stitched using any of the styles illustrated in figure€21 A, B, C, or D.  A machine-sewn seam used to close an envelope at a wingtip, wing trailing edge, empennage and control surface trailing edge, and a fuselage lon......Page 76
For an overlapped and doped seam on a wing’s leading edge, on aircraft with a velocity never exceed (Vne) speed up to and including 150€mph, overlap the fabric 2€inches and cover with a finishing tape that is at least 3€inches wide, with the tape centere......Page 77
The Blanket Method.  A blanket is developed by sewing together, sidebyside, multiple sections of fabric with the seams chordwise or two wide sections of fabric, sidebyside, placing the seam spanwise on the leading edge, the same as an envelope.  Clos......Page 80
When the aircraft Vne speed is over 250€mph, antitear strips, cut from the same quality fabric used to cover the aircraft, are recommended for use under reinforcing tape on the entire top surface of the wing and on the portion of the wing’s bottom surfa......Page 81
Stationary structures interfering with needle routing may be circumvented by aligning the needle forward or aft adjacent to the rib cap.  Pull the needle through the wing and then return through the same hole and exit at the desired adjacent location.......Page 82
Both surfaces of fabric covering on wings and control surfaces must be securely fastened to the ribs by lacing cord or any other method originally approved for the aircraft.  Care must  be taken to insure that all sharp edges against which the lacing cor......Page 83
Rib lace spacing on wings, formerly referred to as stitch spacing, should be no greater than the spacing used by the original aircraft manufacturer.  When the original spacing cannot be determined the maximum spacing illustrated in figure€212 should be......Page 90
Single-wire clips may be removed without damage to the rib by inserting a wide, thin screwdriver blade under the clip and carefully twisting.  Apply a lifting force at the clip end to pull it up through the hole.......Page 92
INSPECTION RINGS AND DRAIN GROMMETS.......Page 93
After all coating applications and sanding are completed, open all holes through flat drain grommets by cutting through the fabric with a small-blade knife.  Do not attempt to open drain holes by punching with a sharp object because the drain hole will n......Page 94
During the coating-buildup procedure, solvents released from each succeeding coat will penetrate and be absorbed into the previous dope film, temporarily releasing the tension and increasing the drying time between coats as the dope film becomes thicker.......Page 95
To offset the deteriorating effect of mildew or other fungus on natural fibers, especially in damp climates, it is recommended that a fungicide be added to the first coat of dope.  The preferred fungicide is zinc dimethyldithiocarbamate powder, which sho......Page 96
Step 5.  After drying at least 2€hours at 70€?F, a third heavy coat of clear dope is applied over the entire surface, preferably with a paint spray gun if brush marks are to be avoided.  After the third coat of dope has dried at least 2€hours at 70€?F, t......Page 97
COVERING OVER PLYWOOD.......Page 98
Blushing.  The appearance of light shaded dull areas on the surface as dope dries is the result of moisture in the atmosphere condensing on a surface due to the cooling effect of the fast-evaporating components of dope thinner escaping from the coating.......Page 99
Spray Gun Laps and Streaks.  These defects may be caused by one or more of the following conditions:......Page 100
Metallic finishes sprayed too heavily allowing metallic pigments to move or flow after deposit, causing a marbled appearance.......Page 101
Coating Cracks.  Fabric exposed through cracks in the coating may be initially tested for deterioration by pressing firmly with a thumb to check the fabric’s strength.  Natural fibers deteriorate by exposure to ultraviolet radiation, mildew, fungus from......Page 103
COATING IDENTIFICATION.......Page 104
FABRIC TESTING.  Mechanical devices used to test fabric by pressing against or piercing the finished fabric are not FAA approved and are used at the discretion of the mechanic to base an opinion on the general fabric condition.  Punch test accuracy will......Page 105
REJUVENATION OF THE DOPE FILM.  If fabric loses its strength, there is nothing to do but remove it and recover the aircraft.  But if the fabric is good and the dope is cracked, it may be treated with rejuvenator, a mixture of very potent solvents and pl......Page 106
REPAIR OF TEARS AND ACCESS OPENINGS.  When all the original fabric is intact, an opening may be repaired by sewing the two sides together with a curved needle as illustrated in figures€213 and€214.  The fabric edges should be pulled together uniformly......Page 107
SEWN-PATCH REPAIR.  Openings that cannot be repaired by closing with stitches may be repaired by sewing in a new fabric section.  The edges of the fabric around the opening should be trimmed straight on four sides to facilitate the installation of strai......Page 108
If the opening is less than 8€inches in length in any direction and the aircraft Vne speed is greater than 150€mph, a 2inch wide finishing tape should be installed on all sides, centered on the edge of the 2inch overlap patch.......Page 109
If the opening is more than 16€inches in length in any direction and the Vne speed is greater than 150€mph, the patch overlap should be 4€inches and the finishing tape should be 6€inches in width, centered on the edge of the patch.......Page 110
FIBERGLASS LAMINATE REPAIRS.  The following repairs are applicable to fiberglass laminate used for non-structural fairing, covers, cowlings, honeycomb panel facings, etc.  Prior to undertaking the repair, remove any paint by using normal dry sanding meth......Page 111
Damage that extends completely through one facing and into the core requires the replacement of the damaged core and facing.  A method for accomplishing this type of repair is shown in figure€32.  An alternate method for repairing the facing is shown in......Page 112
Prepare the patches by (see figure€34) laying the proper weight fiberglass cloth impregnated with resin on a piece of peel ply.  A weight of resin equal to the weight of the patch provides a 50percent ratio.......Page 113
StepJoint Method.  The scarf method of repairing a laminated fiberglass face sheet of a honeycomb structure is the easiest method to use.  In this type of repair, the damage is outlined with a compass.  If a square or rectangular repair is more appropri......Page 114
SAMPLE BAGGING AND CURING PROCESS.  Figure€39 shows a typical bagging arrangement for a localized repair in which patch plies of prepreg are cured with a layer of adhesive, and a heating blanket is used to supply heat.......Page 115
To provide a path to draw off the air initially inside the bag, layers of fiberglass cloth or similar noncontaminating materials, known as breather plies, are placed inside the bag.  When prepreg is being cured as part of the repair, it is sometimes nece......Page 116
One or more thermocouples should be in contact with the heat blanket to monitor its temperature.  Additional thermocouples should be placed near the curing repair to monitor the temperature of the curing resin.......Page 117
Observe cure time requirements established by the product manufacturer.......Page 118
For the repair of larger holes in which it is inconvenient to use a face patch because of aerodynamic smoothness requirements in that area, both the core and facing are sometimes replaced with glass-fiber fabric discs and resin.  Undercut the core, as sh......Page 119
Core potting is the process of filling the core cutout with a curable paste filler material.  If the damage is sustained in an area with an already-potted core, the replacement core should also be potted.  In other cases, if the honeycomb or foam core is......Page 120
Complete removal of core material to the opposite face generally requires some hand-cutting with a core knife.  Figure€315 shows core material being removed with a core knife.  The core can be peeled away from the skin bond using duckbill pliers.  Sandi......Page 121
Trim the top of the cured core plug flush with either the original core or the mold line, depending on the type of laminate repair to be performed.  Proceed with laminate repair.......Page 122
FINISHING.  The type of finish coating applied to a metallic sandwich repair will normally be determined by the exposed material and the application of the part or assembly.  Rain erosion of plastic parts, the need for electrical or dielectric properties......Page 123
Formed sections should be stored with ample support so they will not lose their shape.  Vertical nesting should be avoided.  Protect formed parts from temperatures higher than 120€(F (49€(C), and leave their protective coating in place until they are ins......Page 125
The mold should be large enough to extend beyond the trim line of the part, and provisions should be made for holding the hot plastic snug against the mold as it cools.......Page 126
Several types of saws can be used with transparent plastics, however circular saws are the best for straight cuts.  The blades......Page 127
PS30 and WeldOn€40 should be used at temperatures no lower than 65€(F.  If cementing is done in a room cooler than 65€(F, it will require a longer time to harden and the joint strength will be reduced.......Page 128
REPAIR OF PLASTICS.  Replace, rather than repair extensively damaged transparent plastic, whenever possible, since even a carefully patched part is not the equal of a new section, either optically or structurally.  At the first sign of crack development,......Page 129
Plug Patch.  When using inserted patches to repair holes in plastic structures, trim the holes to a perfect circle or oval and bevel the edges slightly.  Make the patch slightly thicker than the material being......Page 130
Do not attempt hand polishing or buffing until the surface is clean.  A soft, opentype cotton or flannel buffing wheel is suggested.  Minor scratches may be removed by vigorously rubbing the affected area by hand, using a soft clean cloth dampened with......Page 131
In installations involving bolts or rivets, make the holes through the plastic oversize by 1/8inch diameter and center so that the plastic will not bind or crack at the edge of the holes.  The use of slotted holes is also recommended.......Page 132
After using the finest abrasive paper, use rubbing compound and buff in a circular motion to remove all traces of the sanding.......Page 133
After removing the damaged windshield, clean all of the sealer from the grooves and cut the new windshield to fit.  New windshields are covered with either protective paper or film to prevent damage during handling or installation.  Carefully peel back j......Page 134
Do not remove the protective paper or film until the windshield is installed and all of the securing screws are in place.......Page 135
IDENTIFICATION OF STEEL STOCK.  The Society of Automotive Engineers (SAE) and the American Iron and Steel Institute (AISI) use a numerical index system to identify the composition of various steels.  The numbers assigned in the combined listing of standa......Page 137
IDENTIFICATION OF ALUMINUM.  To provide a visual means for identifying the various grades of aluminum and aluminum alloys, such metals are usually marked with symbols such as a Government Specification Number, the temper or condition furnished, or the co......Page 138
BRINELL HARDNESS TEST.  In this test a standard constant load, usually 500€to 3,000€kg, is applied to a smooth flat metal surface by a hardened steel-ball type indenter, 10€mm in diameter.  The 500kg load is usually used for testing nonferrous metals su......Page 141
MICROHARDNESS TESTING.  This is an indentation hardness test made with loads not exceeding 1€kg (1,000€g).  Such hardness tests have been made with a load as light as 1€g, although the majority of microhardness tests are made with loads of 100€to 500€g.......Page 142
INDENTATIONS.  The Vickers indenter penetrates about twice as far into the work  piece as does the Knoop indenter.  The diagonal of the Vickers indentation is about onethird of the total length of the Knoop indentation.  The Vickers indenter is less sen......Page 143
Table 4-5. Hardness values for aluminum alloys. (Reference MIL-H-6088G.)......Page 144
Trim Tab Maintenance.  Loose or vibrating trim tabs will increase wear of actuating mechanisms and hinge points which may develop into serious flutter conditions.  When this happens, primary control surfaces are highly susceptible to wear, deformation, a......Page 145
Use Of Stacked Doublers.  A stacked doubler is composed of two or more sheets of material that are used in lieu of a single, thicker sheet of material.  Because the stress transferred at each row of rivets is dependent upon the maximum stress that can be......Page 146
Rivet Holes.  Rivet holes are slightly larger than the diameter of the rivet.  When driven, solid rivets expand to fill the hole.  The strength of a riveted joint is based upon the expanded diameter of the rivet.  Therefore, it is important that the prop......Page 147
Use of Annealed Alloys for Structural Parts.  The use of annealed aluminum alloys for structural repair of an aircraft is not recommended.  An equivalent strength repair using annealed aluminum will weigh more than a repair using heat-treated aluminum a......Page 148
Setback is a measurement used in sheet metal layout.  It is the distance the jaws of a brake must be setback from the mold line to form a bend.  For a 90 degree bend, the point is back from the mold line to a distance equal to the bend radius plus the me......Page 149
Solid shank rivets are used widely during assembly and repair work.  They are identified by the material of which they are made, the head type, size of shank, and temper condition.......Page 150
An example of identification marking of rivet follows.......Page 151
Replace rivets with those of the same size and strength whenever possible.  If the rivet hole becomes enlarged, deformed, or otherwise damaged; drill or ream the hole for the next larger size rivet.  However, make sure that the edge distance and spacing......Page 152
on aircraft in air intake areas where rivet parts may be ingested by the engine, on aircraft control surfaces, hinges, hinge brackets, flight control actuating systems, wing attachment fittings, landing gear fittings, on floats or amphibian hulls below t......Page 155
Self plugging frictionlock cherry rivets.  This patented rivet may be installed when there is access to only one side of the structure.  The blind head is formed by pulling the tapered stem into the hollow shank.  This swells the shank and clamps the sk......Page 156
Mechanicallock rivets have a device on the puller or rivet head which locks the center stem into place when installed.  Many friction-lock rivet center stems fall out due to vibrations; this in turn, greatly reduces its shear strength.  The mechanical-l......Page 157
The CherryMax (see figure€49) rivet uses one tool to install three standard rivet diameters and their oversize counterparts.  This makes the use of CherryMax rivets very popular with many small general aviation repair shops.  CherryMax rivets are availa......Page 160
An OlympicLok (see figure€410) rivet is a light threepiece mechanically locked, spindletype blind rivet.  It carries its stem lock integral to the manufactured head.  While installing, the lockring is pressed into a groove on the pulling stem just as......Page 161
The specific instructions in paragraphs 458g through 458n.  When following the instruction in paragraphs 458g through 458n, the general rule for the diameter of the rivets used to join aluminum sheets is to use a diameter approximately three times th......Page 162
REPAIR METHODS AND PRECAUTIONS FOR ALUMINUM STRUCTURE.  Carefully examine all adjacent rivets outside of the repair area to ascertain that they have not been harmed by operations in adjacent areas.  Drill rivet holes round, straight, and free from cracks......Page 163
Repair of Damaged Skin.  In cases where metal skin is damaged extensively, repair by replacing an entire sheet panel from one structural member to the next.  The repair seams are to lie along stiffening members, bulkheads, etc.; and each seam must be mad......Page 164
To avoid reducing the strength in tension of the original bulb angle, the rivet holes at the ends of the splice are made small (no larger than the original skin attaching rivets), and the second row of holes (those through the bulbed leg) are staggered b......Page 165
Splicing of Intermediate Frames.  The same principles used for stringer splicing may be applied to intermediate frames when the following point is considered.  Conventional frames of channel or Z sections are relatively deep and thin compared to stringer......Page 174
T......Page 175
T......Page 176
Selective Plating Uses.  This process can be utilized for any of the following reasons.......Page 178
Brush-plating solutions are five to fifty times as concentrated as tank solutions.  The current densities used range from 500€to 4,000€amps/feet2.  The voltages listed on the solution bottles have been precalculated to give proper current densities.  Too......Page 185
Electroclean the area using direct current until water does not break on the surface.  This electroclean process should be accomplished at 10€to 15€volts, using the appropriate electroclean solution.......Page 186
Rinse thoroughly.......Page 187
Plating Solution Selection.......Page 188
Personnel Training for Quality Control.  Manufacturers of selective-plating equipment provide training in application techniques at their facilities.  Personnel performing selective plating must have adequate knowledge of the methods, techniques, and pra......Page 189
EQUIPMENT SELECTION.  Use the welding equipment manufacturer’s information to determine if the equipment will satisfy the requirements for the type of welding operation being undertaken.  Disregarding such detailed operating instructions may cause substa......Page 191
The welding scale is removed.  The welding scale can be removed using a wire brush or by sandblasting.  Remove any......Page 192
TORCH SIZE (Oxyacetylene welding).  When using oxyacetylene welding, the torch tip size depends upon the thickness of the material to be welded.  Commonly used......Page 193
Gas Welding.  A fuel gas such as acetylene or hydrogen is mixed inside a welding torch with oxygen to produce a flame with a temperature of around 6,300€F (3,482€(C).......Page 194
Gas Tungsten Arc Welding (GTAW).  This is the form of electric arc welding that fills most of the needs in aircraft maintenance.  It is more commonly known as Tungsten Inert Gas (TIG) welding and by the trade names of Heliarc or Heliweld.  These trade na......Page 195
Seam Welding.  Rather than having to release the electrodes and move the material to form a series of overlapping spot welds, a seamwelding machine is used to manufacture......Page 196
The effect of the brazing process on the strength of the parent or base metal of steel alloys should be considered in the structural design.  Where copper furnace brazing is employed, the calculated allowable strength of......Page 197
When both parts of the base metal are at the right temperature (indicated by the flow of flux), brazing alloy can be applied to the surface of the under or inner part at the edge of the seam.  It is necessary to simultaneously direct the flame over the s......Page 198
The application of the melted solder requires somewhat more care than is apparent.  The parts to be soldered should be locked together or held mechanically or manually while tacking.  To tack the seam, the hot copper iron is touched to a bar of solder, t......Page 199
Location and Alignment of Welds.  Unless otherwise noted, welded steel tubing may be spliced or repaired at any location along the length of the tube.  To avoid distortion, pay particular attention to the proper fit and alignment.......Page 200
Members Dented at a Cluster.  Repair dents at a steel-tube cluster joint by welding a specially formed steel patch plate over the dented area and surrounding tubes.  (See figure€434.)  To prepare the patch plate, cut a section of steel sheet of the same......Page 201
Make a diagonal cut when removing the damaged portion of the tube, and remove the burr from the edges of the cut by filing or similar means.  Diagonally cut a replacement steel tube of the same material and diameter, and at least the same wall thickness,......Page 203
Tack weld the two sleeves to the replacement tube in two places before welding.  Apply a uniform weld around both ends of one of the reinforcement sleeves and allow the weld to cool; then, weld around both ends of the remaining reinforcement tube.  Allow......Page 205
SPLICING USING LARGER DIAMETER REPLACEMENT TUBES.  The method of splicing structural tubes, as shown in figure€440, requires the least amount of cutting and welding.  However, this splicing method cannot be used where the damaged tube is cut too near th......Page 206
Use only high-grade metallurgically controlled (mc) welding rods for engine-mount repairs.......Page 209
Streamline Tube Construction.  Repair landing gears made of streamlined tubing by either one of the methods shown in figure€442, figure€444, or figure€445.......Page 211
A welded joint may be repaired by cutting out the welded joint and replacing it with one properly gusseted.  Standard splicing procedures should be followed.......Page 212
STAINLESS STEEL STRUCTURE. Repair structural components made from stainless steel, particularly the “188” variety (18€percent chromium, 8€percent nickel), joined by spot welding, in accordance with the instructions furnished by the manufacturer, DER, or......Page 213
FIRE PROTECTION.  Practice fire prevention techniques whenever oxy-fuel operations are in progress.  Simple precautions prevent most fires, and minimize damage in the event a fire does occur.  Always practice the following rules and safety procedures.......Page 219
FIRST-AID KITS.  Always keep a special welder’s first-aid kit where it is easily accessible.  Burns are the most common welding accidents.......Page 220
The individual must have 2 years of engineering or science study at a university,......Page 221
Segregation is a nonuniform distribution of various chemical constituents that can occur in a metal when an ingot or casting solidifies.  Segregation can occur anywhere in the metal and is normally irregular in shape.  However, there is a tendency for so......Page 222
A cold shut is a failure of metal to fuse.  It can occur in castings when part of the metal being poured into the mold cools and does not fuse with the rest of the metal into a solid piece.......Page 223
Plating cracks can occur when hardened surfaces are electroplated.  Generally, they are found in areas where high residual stresses remain from some previous operation involving the part.......Page 224
Possible locations and orientations of defects;......Page 225
Tap testing......Page 226
Xenon (for over 100€percent more light than standard bulbs).......Page 229
A flexible or rigid tube with wiring that carries the image signal from a Charge Couple Device (CCD) imaging sensor at the distal tip.......Page 230
Corrosion Treatment.  Treat any corrosion found during preliminary inspection after completing a visual inspection of any selected part or area.......Page 231
Recordkeeping.  Document all discrepancies by written report, photograph, and/or video recording for appropriate evaluation.  The full value of visual inspection can be realized only if records are kept of the discrepancies found on parts inspected.  The......Page 232
EDDY CURRENT COILS AND PROBES.  A wide variety of eddy current coils and probes is available.  Coils and probes are not always interchangeable between various types of instruments and, for best results, should be matched to a specific instrument and freq......Page 235
Many types of probes are available such as: flat-surface; spring-loaded; pencil; shielded pencil; right-angle pencil; or fastener hole probes.......Page 236
ESTABLISHING EDDY CURRENT INSPECTION PROCEDURES.  When establishing eddy current inspection procedures, where no written procedures are available, the following factors must be considered:  type of material to be inspected; accessibility of the inspectio......Page 237
Abrupt changes in geometry or in magnetic properties within the part.......Page 239
MATERIALS USED IN MAGNETIC PARTICLE INSPECTION.  The particles used in magnetic particle inspection are finely divided ferro-magnetic materials that have been treated with color or fluorescent dyes to improve visibility against the various surface backgr......Page 240
T......Page 241
Dry Continuous Method.  This method is not recommended for use on aerospace components because of its lower sensitivity level.......Page 242
Direct Induction (contact method).  Pass current through the part mounted horizontally between contact plates.  As an example, circular magnetization of a round steel bar would be produced by placing the ends of the steel bar between the heads of the mag......Page 243
For the 10to1 fill factor, the effective region of inspection is 1 coil radius on either side of the coil with 10€percent overlap.  (Refer to ASTME1444.)......Page 244
SPECIAL EXAMINATION TECHNIQUES.......Page 245
Methods of magnetization should be done according to standard procedures; however, alternating fields should not be used, and the level of magnetizing force imposed should usually be increased above the normal levels to ensure a higher residual field wit......Page 246
When oil suspensions are used, solvent clean or remove the part until all magnetic particles and traces of oil are removed.......Page 247
After magnetic particle examination has been completed, restore any removed finishes according to the manufacturer’s repair manual.......Page 248
BASIC STEPS TO PERFORM PENETRATION INSPECTION.  Table€54 shows a general process, in the procedures flow sheet, for commonly used penetrant inspection processes.  It is important to ensure that parts are thoroughly cleaned and dried before doing penetra......Page 249
Table 5-3. Classification of penetrant inspection materials covered by MILI25135E.......Page 250
Drying.  If removal of the excess penetrant involves water or other cleaning liquids, drying of the part may be required prior to developer application.  When drying is required, the time can be decreased by using ovens or ventilation systems.......Page 253
TECHNICAL STANDARDS.  Two of the more generally accepted aerospace industry standards are the MILI25135E, Inspection Materials, Penetrants (see table€56) and ASTME1417.  The penetrant materials specification (MILI25135E) is used to procure penetra......Page 254
Table 5-6. Listing of commonly accepted standards and specifications for penetrant inspection.......Page 255
COMPUTED TOMOGRAPHY......Page 257
COMPARISON WITH OTHER NDI METHODS.  Radiography and ultrasonic are the two generally-used, nondestructive inspection methods that can satisfactorily detect flaws that are completely internal and located well below the surface of the test part.  Neither m......Page 258
SAFETY.  Radiographic safety requirements can be obtained from; the OEM’s manual, FAA requirements, cognizant FAA ACO engineers, and radiation safety organizations such as the Nuclear Regulatory Commission (NRC).  Information in radiation safety publicat......Page 259
BASIC EQUIPMENT.  Most ultrasonic inspection systems include the following basic equipment; portable instruments (frequency range 0.5€to€15€MHz), transducers (longitudinal and shear wave), positioners, reference standards, and couplant.......Page 261
Ultrasonic Instruments.  A portable, battery-powered ultrasonic instrument is used for field inspection of airplane structure.  (See figure€517.)  The instrument generates an......Page 262
Different types and thickness of adhesives are used in bonded structures.......Page 263
Fabrication of NDI Reference Standards.  Every ultrasonic test unit should have sample materials that contain unbonds equal to the sizes of the minimum rejectable unbonds for the test parts.  Information on minimum rejectable unbond sizes for test parts......Page 265
Mechanical impedance.  Low-frequency, pulsed ultrasonic energy is generated into a structure.  Through ultrasonic mechanical vibration of the structure, the impedance or stiffness of the structure is measured, analyzed, and displayed by the instrumentati......Page 266
Operation.  In general, operation of the adhesive bond test instruments noted is similar.  The test probe is moved over the surface in smooth overlapping strokes.  The direction of the stroke with regard to the surface is generally immaterial; however, w......Page 267
Standard Method.  A standard method of testing for leaks using ultrasonics is provided in ASTM€E€1002.  The method covers procedures for calibration, location, and estimated measurements of leakage by the ultrasonic technique (sometimes called ultrasonic......Page 270
Typical Applications.  Some typical applications for the ultrasonic leak detector on aircraft are: fuel system pressurization tests, air ducts and air conditioning systems, emergency evacuation slides, tire pressure retention, electrical discharge, oxyge......Page 271
SECTION 9.  ACOUSTICEMISSION......Page 273
SECTION 11.  HOLOGRAPHY......Page 274
SECTION 12.  SHEAROGRAPHY......Page 275
Lead/graphite pencil marks on aircraft surface metals.......Page 277
are less resistant and also at boundaries between regions, resulting in the formation of pits and intergranular corrosion. Metals have a wide range of corrosion resistance.  The most active metals, (those which lose  electrons eas-......Page 278
MICRO-ORGANISMS.......Page 279
Microbial growth must be removed completely to avoid corrosion.  Microbial growth should be removed by hand with a firm non-metallic bristle brush and water.  Removal of microbial growth is easier if the growth is kept wet with water.  Microbial growth m......Page 280
PITTING CORROSION.  Pitting corrosion is one of the most destructive and intense forms of corrosion.  It can occur in any metal but is most common on metals that form protective oxide films, such as aluminum and magnesium alloys.  It is first noticeable......Page 281
ACTIVE-PASSIVE CELLS.  Metals which depend on a tightly adhering passive film, usually an oxide, for corrosion protection are prone to rapid corrosive attack by active-passive cells.  Active-passive cells are often referred to as a type of concentration......Page 282
EXFOLIATION CORROSION.  Exfoliation corrosion is an advanced form of inter-granular corrosion and shows itself by lifting up the surface grains of a metal by the force of expanding corrosion products occurring at the grain boundaries just below the surfa......Page 283
Internal stress is more important than design stress, because stress corrosion is difficult to recognize before it has overcome the design safety factor.  The level of stress varies from point to point within the metal.  Stresses near the yield strength......Page 284
Fatigue corrosion failure occurs in two stages. During the first stage the combined action of corrosion and cyclic stress damages the metal by pitting and crack formations to such a degree that fracture by cyclic stress will occur, even if the corrosive......Page 285
FRETTING CORROSION.  Fretting corrosion,(also known as wear corrosion or friction oxidation) can occur at the interface of two highly-loaded surfaces which are not supposed to move against each other.  However, vibration may cause the surfaces to rub tog......Page 286
DICHROMATE TREATMENT.  This treatment consists of boiling magnesium parts in a solution of sodium dichromate.  It provides good paint base and protective qualities on all standard wrought magnesium alloys except the magnesium-thorium alloys.  Acid pickli......Page 287
TUBE INTERIORS.  Protect the interiors of structural steel and aluminum tubing against corrosion.  A small amount of water entrapped in a tube can corrode entirely through the tube thickness in a short period.  Coat the tube interior by flushing with hot......Page 288
After drying, coat the propeller, hubs, blades and other unpainted or unprotected parts of the engine and its installation parts by spraying or rubbing lightly with corrosion preventive compound, Specification MILC16173, Grade€4.......Page 289
Except for friction and bearing surfaces, apply a protective coating to all parts of wheels and brake assemblies.......Page 290
Inspect piano type hinges for corrosion. When piano hinges are inspected they should be lubricated and actuated through several cycles to ensure complete penetration of the lubricant.......Page 291
If the electrical connector is suspected of having moisture intrusion, disassemble the connector, clean the connector, and inspect it for corrosion.......Page 292
If materials (acid, alkali, paint remover, or conversion coatings) are spilled on equipment and/or tools, treat immediately by rinsing with clean water, if possible, and /or neutralizing acids with baking soda and alkalies with a weak (5€percent) solutio......Page 293
Coated metal surfaces should not be polished for aesthetic purposes.  Buffing would remove the protective coating and a brightly polished surface is normally not as corrosion resistant as a non-polished surface unless it is protected by wax or paint.......Page 294
Severely corroded screws, bolts, and washers should be replaced.  When a protective coating, such as a cadmium plating on bolts, or screws, is damaged, immediately apply an appropriate protective finish to prevent additional corrosion damage.......Page 295
In critical and highly stressed areas, all pits remaining after the removal of corrosion products should be blended out to prevent stress risers that may cause stress corrosion cracking.  (See figure€614.)  On a non-critical structure, it is not necessa......Page 297
CLEANERS, POLISHES, AND BRIGHTENERS.  It is important that aircraft be kept thoroughly clean of contaminating deposits such as oil, grease, dirt, and other foreign materials.......Page 298
STANDARD METHODS.  Several standard mechanical and chemical methods are available for corrosion removal.  Mechanical methods include hand sanding using abrasive mat, abrasive paper, or metal wool; and powered mechanical sanding, grinding, and buffing, us......Page 299
Remove all excess sealant after fasteners are installed.  Apply a fillet sealant bead around the edge of the repair.  After the sealant has cured apply the protective paint finish to the reworked area.......Page 301
The corrosion removal compound aluminum pretreatment MILC38334, an acid material, may be used to remove corrosion products from aluminum alloy materials or items (e.g., skins, stringer, ribs in wings, tubing, or ducts).  MILC38334 is available in two......Page 302
Where the problem is severe enough to warrant the use of power tools, a pneumatic drill motor driving either an aluminum-oxide-impregnated nylon abrasive wheel, flap brush or rubber grinding wheel may be used with an abrasive value to approximately 120€g......Page 303
Apply paint finish to area.......Page 304
REPAIR OF MAGNESIUM SHEET METAL AFTER EXTENSIVE CORROSION REMOVAL.  The same general instructions apply when making repairs in magnesium as in aluminum alloy skin, except that two coats of epoxy primer may be required on both the doubler and skin being p......Page 305
Previously been sand blasted.......Page 306
Do not use rotary wire brushes on magnesium.......Page 307
Container: Stainless Steel, Aluminum, Vinyl, Polyethylene, or Rubber.......Page 308
Remove masking and protective coverings.......Page 309
If any deterioration or corrosion does occur on austenitic steels, and the structural integrity or serviceability of the part is affected, it will be necessary to remove the part.......Page 311
Remove masking and protective coverings.......Page 312
Corrosive attack on titanium surfaces is difficult to detect.  It may show deterioration from the presence of salt deposits and metal impurities at elevated temperatures so periodic removal of surface deposits is required.  However, if corrosion develops......Page 313
Titanium surfaces are susceptible to hydrogen embrittlement that can induce stress corrosion and associated pitting.  Therefore, chemicals such as fireresistant hydraulic fluids must be controlled.  Chlorinated hydrocarbon solvents and chemical corrosio......Page 314
Zinc coatings offer protection in an identical manner to cadmium, and the corrective treatment for failure is generally the same as for cadmium-plated parts.  However, the amount of zinc on aircraft structures is very limited and usually does not present......Page 315
Spray the interior of metal-covered wings and fuselages with an adherent corrosion inhibitor.......Page 317
Prevent the entry of water by sealing, as completely as possible,  all openings in wings, fuselage, control-surface members, openings for control cables, tail-wheel wells, etc.......Page 318
AIRFRAME.  The salvable components of the fuselage, wings, empennage,  seaplane and amphibian hulls and floats, and movable surfaces should be processed as follows:......Page 319
Remove instruments and radios and applicable cables and plumbing, and repair and inspect as necessary.......Page 320
Corrosion-resistant steel rivets are used primarily in riveting corrosion-resistant steel parts such as firewalls, exhaust stack bracket attachments, and similar structures.......Page 321
Blind rivets in the NASM20600 through NASM20603 series rivets and the mechanically-locked stem NAS 1398, 1399, 1738, and 1739 rivets sometimes may be substituted for solid rivets.  They should not be used where the looseness or failure of a few rivets wi......Page 322
PANHEAD SCREWS (NAS600 THROUGH NAS606, NAS610 THROUGH NAS616, NAS623, AND NAS1402 THROUGH NAS1406).  Flathead screws (MS35188 through MS35203), panhead machine screws (MS35024 through MS35219), and truss-head screws (AN526) are general-purpose screws use......Page 323
WOOD SCREWS  AN545 and AN550, MS35492 and MS35493 are screws used in wood structures of aircraft.......Page 324
Special-purpose bolts include high-strength, low-strength, and close-tolerance types.  These bolts are normally inspected by magnetic particle inspection methods.  Typical markings include “SPEC” (usually heat-treated for strength and durability), and an......Page 325
Run the nut down to near contact with the washer or bearing surface and check the friction drag torque required to turn the nut.  Whenever possible, apply the torque to the nut and not the bolt.  This will reduce rotation of the bolt in the hole and redu......Page 326
ENGINE BOLTS.  These are hex head bolts (AN101001 through AN101900), drilled shank hex head bolts (AN101901 through AN102800), drilled hex head (one hole) bolts (AN102801 through AN103700), and drilled hex head (six holes) bolts (AN103701 through AN10460......Page 327
CLOSE-TOLERANCE BOLTS.......Page 329
EYEBOLTS (AN42 THROUGH AN49).  These bolts are used in applications where external tension loads are to be applied.  The head of this bolt is specially designed for the attachment of a turnbuckle, a clevis, or a cable shackle.  The threaded shank may or......Page 330
NUT IDENTIFICATION FINISHES.  Several types of finishes are used on self-locking nuts.  The particular type of finish is dependent on the application and temperature requirement.  The most commonly used finishes are described briefly as follows.......Page 331
CASTLE NUT (AN310).  The castle nut is used with drilled shank hex head bolts, clevis bolts, drilled head bolts, or studs that are subjected to tension loads.  The nut has slots or castellations cut to accommodate a cotter pin or safety wire as a means o......Page 332
SHEET SPRING NUTS (AN365).  Sheet spring nuts are commonly called speed nuts.  They are used with standard and sheet metal self-tapping screws in nonstructural applications.  They are used to support line and conduit clamps, access doors, etc.  Their use......Page 333
TAPER PIN WASHERS (AN975).  Taper pin washers are used with the threaded taper pin.  NAS143 and MS20002 washers are used with NAS internal wrenching bolts and internal wrenching nuts.  They may be plain or countersunk.  The countersunk washer (designated......Page 335
QUICK-RELEASE PINS.  These pins are used in some applications where rapid removal and replacement of equipment is necessary.  When equipment is secured with these pins, no binding of the spindle should be present.  Spindle binding could cause the locking......Page 337
When using double-twist method of safety wiring, .032€inch minimum diameter wire should be used on parts that have a hole diameter larger than .045€inch.  Safety wire of .020€inch diameter (double strand) may be used on parts having a nominal hole diamet......Page 339
Drilled boltheads and screws need not be safety wired if installed with self-locking nuts.......Page 340
Squeeze handles together to release wire.......Page 341
SECURING OIL CAPS, DRAIN COCKS, AND VALVES.  (See figure€74a.)  When securing oil caps and drain cocks, the safety wire should be anchored to an adjacent fillister-head screw.  This method of safety wiring is applied to wingnuts, filler plugs, single-dr......Page 342
To prevent injury during and after pin installation, the end of the cotter pin can be rolled and tucked.......Page 346
Nylon-coated cable is made by extruding a flexible nylon coating over corrosion-resistant steel (CRES) cable.  The bare CRES cable must conform and be qualified to MILW83420.  After coating, the jacketed cable must still conform to MILW83420.......Page 347
thereby, greatly reducing their effect on the cable.......Page 348
CABLE SPECIFICATIONS.  Cable diameter and strength data are given in table€73 and table€74.  These values are acceptable for repair and modification of civil aircraft.......Page 349
Insert the cable into the terminal approximately 1€inch, and bend toward the terminal, then push the cable end entirely into the terminal barrel.  The bending action puts a kink or bend in the cable end, and provides enough friction to hold the terminal......Page 350
Test the cable by proof-loading it to 60€percent of its rated breaking strength.......Page 351
At all subsequent service inspections of the swaged fitting, check for a gap in the painted section to see if cable slippage has occurred.......Page 352
Terminal Gauge.  To make a satisfactory copper sleeve installation, it is important that the amount of sleeve pressure be kept uniform.  The completed sleeves should be checked periodically with the proper gauge.  Hold the gauge so that it contacts the m......Page 353
Other Applications.  The preceding information regarding copper oval sleeves and stop sleeves is based on tests made with flexible aircraft cable.  The sleeves may also be......Page 354
Kinking of wire cable can be avoided if properly handled and installed.  Kinking is caused by the cable taking a spiral shape as the result of unnatural twist. One of the most common causes for this twist is improper unreeling and uncoiling.  In a kinked......Page 355
As wear is taking place on the exterior surface of a cable, the same condition is taking place internally, particularly in the sections of the cable which pass over pulleys and quadrants.  This condition (shown in figure€719) is not easily detected unle......Page 356
Various cable system malfunctions may be detected by analyzing pulley conditions.  These include such discrepancies as too much tension, misalignment, pulley bearing problems, and size mismatches between cables and pulleys.  Examples of these condition a......Page 357
Lubrication and corrosion preventive treatment of carbon steel cables may be effected simultaneously by application of compound MILC16173, grade€4, or MILC11796, Class€I.  MILC16173 compound should be brushed, sprayed, or wiped on the cable to the......Page 358
CABLE TENSION ADJUST-MENT.  Carefully adjust, control cable tension in accordance with the airframe manufacturer’s recommendations.  On large aircraft, take the temperature of the immediate area into consideration when using a tension meter.  For long ca......Page 359
WITNESS HOLE.  Some manufacturers of turnbuckles incorporate a “witness hole,” in the turnbuckle barrel to ensure that the threaded cable terminals are screwed in far enough into the barrel.  The “witness hole” can be inspected visually, or by using a pi......Page 361
Pass a single length of wire through the cable eye or fork, or through the hole in the swaged terminal at either end of the turnbuckle assembly.  Spiral each of the wire ends in opposite directions around the first half of the turnbuckle barrel, so as to......Page 363
For the method shown in figure 726D, pass one length of wire through the center hole of the turnbuckle and bend the wire ends toward opposite ends of the turnbuckle.  Then pass each wire end through the cable eye or fork, or through the hole in the swag......Page 364
Apply pressure to hook shoulder to engage hook lip in turnbuckle barrel and to complete safety locking of one end of turnbuckle.......Page 365
SECTION 11.  HARDWARE IDENTIFICATION TABLES......Page 369
If the engine manufacturer does not provide the required information, then the engine case must be opened and every major component part must be inspected using visual and/or nondestructive inspection (NDI) procedures as applicable.......Page 395
Remove the propeller reduction gear housing and inspect for:......Page 396
CRANKSHAFT INSPECTION AND REPAIR REQUIREMENTS.  Carefully inspect for misalignment and replace if bent beyond the manufacturer’s permissible service limit.  Worn journals may be repaired by regrinding in accordance with manufacturers’ instructions.  It i......Page 397
When there is at least one full thread protruding beyond the nut.......Page 398
A list of engine and maximum permissible cylinder barrel oversize are referenced in table€81.......Page 399
COMPRESSION TESTING OF AIRCRAFT ENGINE CYLINDERS.  A test to determine the internal condition of the combustion chamber cylinder assembly by ascertaining if any appreciable internal leakage is occurring is compression testing of aircraft engine cylinders......Page 400
While performing the check the following procedures are listed to outline the principles involved, and are intended to supplement the manufacturer’s instructions for the particular tester being used.......Page 401
Heat Range.  The heat range of a spark plug is the principal factor governing aircraft performance under various service conditions.  The term “heat range” refers to the......Page 402
“Hot” plugs have a long insulator nose; thereby, creating a long heat transfer path, whereas “cold” plugs have a relatively short insulator to provide a rapid transfer of heat to the cylinder head.  (See figure€83.)......Page 403
Check the plug and cylinder bushing to ascertain that only one gasket is used per spark plug.  When a thermocouple-type gasket is used, no other gasket is required.......Page 404
Oil fouling is identified by a wet, black carbon deposit over the entire firing end of the plug as shown in figure€86b.  This condition is fairly common on the lower plugs in horizontally-opposed engines, and both plugs in the lower cylinders of radial......Page 405
Bridged Electrodes.  Occasionally, free combustion chamber particles will settle on the electrodes of a spark plug and gradually bridge the electrode gap, resulting in a shorted plug.  Small particles may be dislodged by slowly cycling the engine as desc......Page 406
Flashover.  It is important that spark plug terminal contact springs and moisture seals be checked regularly for condition and cleanliness to prevent “flashover” in the connector well.  Foreign matter or moisture in the terminal connector well can reduce......Page 407
Connector seat at the top of the shielding barrel badly nicked or corroded.......Page 408
Look for frayed insulation on the leads in the breaker compartment of the magneto.  See that all terminals are secure.  Be sure that wires are properly positioned.......Page 409
Check the magneto ventilators for proper functioning and obstructions.  If drilled plugs are used, they should be in the lowest vent hole of the magneto to serve as a drain for condensation and oil.......Page 410
The possibility of a timing error exists if a timing indicator which attaches to the propeller shaft or spinner of geared engines is used.  Engine timing specifications are always given in degrees of crankshaft travel and cannot be applied directly to ge......Page 411
FUEL TANKS AND CELLS.  Welded or riveted fuel tanks that are made of commercially pure aluminum,€3003,€5052, or similar alloys, may be repaired by welding.  Tanks made from heat-treatable aluminum alloys are generally assembled by riveting.  In case it i......Page 413
FUEL TANK CAPS, VENTS, AND OVERFLOW LINES.  Inspect the fuel tank caps to determine they are the correct type and size for the installation, and that “O” rings are in good condition.......Page 414
FUEL FILTERS, STRAINERS, AND DRAINS.  Check each strainer and filter element for contamination.  Determine and correct the source of any contaminants found.  Replace throw-away filter elements with the recommended type.  Examine fuel strainer bowls to se......Page 415
Do not use Teflon tape on any fuel lines to avoid getting the tape between the flare and fitting, which can cause fluid leaks.......Page 416
MANIFOLD/STACK FAILURES.......Page 417
In addition, local hot spot areas caused by uneven exhaust gas flow, result in burning, bulging, and rupture of the outer muffler wall.  (See figure€814.)  As might be expected, the time required for these failures to develop is longer than that for fa......Page 418
The highest rate of internal muffler failures occurs between 500€and 750€hours of operating time.  Engine power loss and excessive back-pressure caused by exhaust outlet blockage may be averted by the installation......Page 419
Should a component be inaccessible for a thorough visual inspection or hidden by non-removable parts, remove the component and check for possible leaks by plugging its openings, applying approximately 2€psi internal pressure, and submerging it in water.......Page 420
REPAIRS.  It is generally recommended that exhaust stacks, mufflers, tailpipes, and etc., be replaced with new or reconditioned components rather than repaired.  Welded repairs to exhaust systems are complicated by the difficulty of accurately identifyin......Page 421
AUGMENTOR SYSTEMS.  Inspect augmentor tubes periodically for proper alignment, security of attachment, and general......Page 422
ALUMINUM PROPELLER REPAIRS.  Aluminum-alloy propellers and blades with dents, cuts, scars, scratches, nicks, leading-edge pitting, etc., may be repaired, provided the removal or treatment does not materially affect the strength, weight, or performance of......Page 423
Flaws in Edges.  Round out nicks, scars, cuts, etc., occurring on the leading edge of aluminum-alloy blades as shown in figure€824 (view€B).  Blades that have the leading edges pitted from normal wear in service may be reworked by removing sufficient ma......Page 424
REPAIR LIMITS.  The following limits are those listed in the blade manufacturing specification for aluminum-alloy blades and govern the width and thickness of new blades.  These limits are to be used with the pertinent blade drawing to determine the mini......Page 425
Step 2.  Calculate percent of blade radius to repair (r%)......Page 426
PROPELLER HUB AND FLANGE REPAIR.  When the fixed-pitch propeller bolt holes in a hub or crankshaft become damaged or oversized, it is permissible to make repairs by using methods (A) or (B) in figure€829, or by use of aircraft standard bolts 1/16inch l......Page 427
DEICING SYSTEMS.  Components used in propeller deicing systems should be inspected, repaired, assembled, and/or tested in accordance with the manufacturer’s recommendations.  Only those repairs which are covered by the manufacturer’s recommendations shou......Page 428
Fixed-pitch propellers are normally removed from the engine at engine overhaul periods.  Whenever the propeller is removed, visually inspect the rear surface for any indication of cracks.  When any defects are found, disassemble the metal hub from the pr......Page 431
METAL PROPELLERS AND BLADES.  These propellers and blades are generally susceptible to fatigue failure resulting from the concentration of stresses at the bottoms of sharp nicks, cuts, and scratches.  It is necessary, therefore, to frequently and careful......Page 432
Inspection procedures require removal of the propeller spinner for examination of the prop hub area.  Cracks may be present in the hub area between or adjacent to bolt holes and along the hub pilot bore.  Cracks in these areas cannot be repaired and requ......Page 433
TACHOMETER€INSPECTION.  Due to the exceptionally high stresses that may be generated by particular propeller/engine combinations at certain engine revolutions per minute (RPM), many propeller and aircraft manufacturers have established areas of RPM restr......Page 434
Cabin vibration can sometimes be improved by reindexing the propeller to the crankshaft.  The propeller can be removed, rotated€180(, and reinstalled.......Page 435
The propeller spinner can be a contributing factor to an out-of-balance condition.  An indication of this would be a noticeable spinner “wobble” while the engine is running.  This condition is normally caused by inadequate shimming of the spinner front......Page 436
CLEANING AND LUBRICATING.......Page 437
Air-oil struts should undergo an inspection similar to that recommended for spring-oleo struts.  In addition, the extension of the strut should be checked to see that it conforms to the distance specified by the manufacturer.  If an air-oil strut “bottom......Page 438
The proper operation of the anti-retraction system should be checked in accordance with the manufacturer’s instructions.  Where safety switches are actuated by the torque links, the actual time of switch closing or opening can be checked by removing all......Page 439
Gear Doors.  Inspect gear doors frequently for cracks, deformation, proper rigging, and general condition.  Gear door hinges are especially susceptible to progressive cracking, which can ultimately result in complete failure, allowing the door to move an......Page 440
Micro-Switches.  Inspect micro-switches for security of attachment, cleanliness, general condition, and proper operation.  Check the associated wiring for chafing, proper routing, and to determine that protective covers are installed on wiring terminals,......Page 441
In retractable wheel-ski arrangements, the ski is mounted on a common axle with the wheel.  In this arrangement, the ski can be extended below the level of the wheel for landing on snow or ice.  The ski can be retracted above the bottom of the wheel for......Page 442
Skis and Ski Installation.  Skis should be inspected for general condition of the skis, cables, bungees, and fuselage attachments.  If retractable skis are used, checks in accordance with the general practices for retractable gear should be followed.  Sk......Page 443
Cracks primarily occur at the edge of bolt holes on the surface and down inside the bore.  (See figures€93 and€94.)......Page 444
RETRACTION TESTS.  Periodically perform a complete operational check of the landing gear retraction system.  Inspect the normal extension and retraction system, the emergency extension system, and the indicating and emergency warning system.  Determine t......Page 445
Surface Condition.  The surface condition of a tire can be inspected with the tire on the aircraft.  The tread should be checked for abnormal wear.  If the tread is worn in the center of the tire but not on the edges, this indicates that the tire is over......Page 446
DISASSEMBLE THE WHEEL in accordance with aircraft manufacturer’s instructions.......Page 447
WHEEL INSPECTION.  Check wheels for damage.  Wheels that are cracked or damaged must be taken out of service for repair or replacement in accordance with the manufacturer’s instruction manual.......Page 448
The grease cover or wheel cover, if used, is then installed.  During this installation any required brake, air-pressure sensors, and speed-sensor components should be installed and connected, as appropriate, for the specific aircraft.......Page 449
Phosphate Ester-Based Fluid (Skydrol/Hyjet).  These fluids are used in most commercial transport category aircraft, and are extremely fire-resistant.  However, they are not fireproof and under certain conditions, they will burn.  The earliest generation......Page 451
The hydrocarbon-based hydraulic fluids are, in general, safe to handle.  To work with these fluids, reasonable handling procedures must always be followed.  Take precaution to avoid fluid getting in the eyes.  If fluid contacts the eye, wash immediately......Page 452
When replacing filter elements, be sure that there is no pressure on the filter bowl.  Protective clothing and a face shield must be used to prevent fluid from contacting the eye.  Replace the element with one that has the proper rating.  After the filte......Page 453
An operational check of the system can be performed using the engine-driven pump, an electrically-operated auxiliary pump (if such a pump is included in the system), or a ground test unit.  The entire system and each subsystem should be checked for smoot......Page 454
The importance of the proper torque applied to all nuts and fittings in a system cannot be over-emphasized.  Too much torque will damage metal and seals, and too little torque will result in leaks and loose parts.  The proper torque wrenches with the app......Page 455
Repair of Metal Tube Lines.  Minor dents and scratches in tubing may be repaired.  Scratches or nicks not deeper than 10€percent of the wall thickness in aluminum alloy tubing, that are not in the heel of a bend, may be repaired by burnishing with hand t......Page 456
Teflon hose is used in many aircraft systems because it has superior qualities for certain applications.  Teflon is compounded from tetrafluoroethylene resin which is unaffected by fluids normally used in aircraft.  It has an operating range of -65(F€to€......Page 457
Assure that the sealing surfaces are clean and free of nicks or scratches before installing seal.......Page 458
Hydraulic Components.  Hydraulic components such as pumps, actuating cylinders, selector valves, relief valves, etc., should be repaired or adjusted following the airplane and component manufacturer’s instructions.  Inspect hydraulic filter elements at f......Page 459
T......Page 465
LIFE RAFT INSPECTIONS.  Inspection of life rafts should be performed in accordance with the manufacturer’s specifications.  General inspection procedures to be performed on most life rafts are as follows.......Page 467
Survival Kit Contents.  Each raft  accommodating passengers or crew members  should contain, as a minimum, the following:......Page 468
First-Aid Kit.  Inspect each kit prior to flight to ensure that the seal is intact; the kits have not been tampered with or opened; and check the date when the kit contents should be inspected (120day interval), and containing the following:......Page 469
Repair Kit.  Check for proper wrapping and missing items.  Four plugs are wrapped in a single container.  This container and the pliers are wrapped in waterproof paper and sealed with waterproof tape.  The package is stenciled repair plugs and pliers wit......Page 470
Folding Life Rafts. Fold the life rafts per the manufacturer’s folding diagram using soapstone and secure the raft in its container. Check the container for obvious damage.......Page 471
From the material referenced, fabricate a patch as shown in figure€913.......Page 472
Using cleaning solvent, cleanse an area on the inside surface of the fabric slightly larger than the patch to be applied. Ensure that the repaired area is thoroughly dry, both inside and outside; apply two coats of extra light cement, two coats of light......Page 473
Allow to cure for at least 60€hours before performing leak tests and storing.......Page 474
Check rescue light.  Inspect and test.......Page 475
When repacking is scheduled, to comply with the 120day requirement in Title€14 of the Code of Federal Regulation (14€CFR) part€105 section€105.43 a careful inspection of the parachute shall be made by a qualified parachute technician (rigger).  If repai......Page 476
Oxygen Tanks and Cylinders.  Inspect the entire exterior surface of the cylinder for indication of abuse, dents, bulges, and strap chafing.......Page 477
Oxygen Tanks, Cylinders, and Hold-Down Brackets.......Page 478
The high-pressure lines which are located between the oxygen bottle (outside the oxygen service filler) and the regulator are normally fabricated from stainless steel or thick-wall, seamless copper alloy tubing.  The fittings on high-pressure lines are n......Page 479
Observe that each mask breathing tube end is free of nicks, and that the tube end will slip into the cabin oxygen receptacle with ease and not leak.......Page 480
Charging High-Pressure Oxygen Cylinders.  The following are recommended procedures for charging high-pressure oxygen cylinders from a manifold system, either permanently-installed or trailer-mounted.......Page 481
Charging of Low-Pressure Oxygen Systems and Portables.  For recharging a low-pressure aircraft oxygen system, or portable cylinders, it is essential that the oxygen trailer or cart have a pressure-reducing regulator.  Military types E2 or C1 reducing r......Page 482
If the fabric is bought in bulk to refurbish a part€23 aircraft then the fabric must meet the part€23 burn requirements.  A burn test would have to be done on samples of the material and fabrics by an approved and rated FAA Repair Station.  That FAA Repa......Page 485
UPHOLSTERY AND/OR BELTS.  Upholstery and/or belts that have been washed may lose some or all of their fireresistant qualities.  Unless the soap is completely removed from the cloth, the strength of the material may be significantly reduced.  Consult the......Page 486
Datum.  The datum is an imaginary vertical plane from which all horizontal measurements are taken for balance purposes with the aircraft in level flight attitude.  The datum is indicated in most Aircraft Specifications or TCDS.  On some of the older airc......Page 487
of the datum, and minus ( - ) if measured forward of the datum.  Examples of plus and minus arms are shown in figure€102.......Page 488
Empty Weight Center of Gravity Range.  The empty weight c.g. range is determined so that the empty weight c.g. limits will not be exceeded under standard specifications loading arrangements.  Calculations as outlined in paragraph€1016 should be complete......Page 489
Weighing Point.  If the c.g. location is determined by weighing, it is necessary to obtain horizontal measurements between the points on the scale at which the aircraft’s weight is concentrated.  If weighed using......Page 490
Tare.  The weight of chocks, blocks, stands, etc., used when weighing aircraft is called tare and is included in the scale readings.  Tare is deducted from the scale reading at each respective weighing point when tare is involved, to obtain the actual ai......Page 494
10-15a.  REPAIRS AND ALTERATIONS are the major sources of weight changes, and it is the responsibility of the aircraft mechanic making any repairs or alteration to know the weight and location of these changes, and to compute the new CG and record the ne......Page 497
WEIGHT AND BALANCE COMPUTATIONS.  It is often necessary after completing an extensive alteration to establish......Page 498
The TCDS do not list the basic required equipment prescribed by the applicable airworthiness regulations for certification.  Refer to the manufacturer’s equipment list for such information.......Page 499
The maximum weights, arms, and moments of the items of useful load that are located aft of the rearward c.g. limit.......Page 500
Required and optional equipment may be shown on the equipment list with reference to the pertinent item number listed in the applicable specifications only when they are identical to that number item with reference to description, weight, and arm given i......Page 502
EQUIPMENT CHANGE.  The person making an equipment change is obligated to make an entry on the equipment list indicating items added, removed, or relocated with the date accomplished, and identify himself by name and certificate number in the aircraft rec......Page 503
SAMPLE WEIGHT AND BALANCE REPORT.  Suggested methods of tabulating the various data and computations for determining the c.g., both in the empty weight condition and the fully loaded condition, are given in figures€1017 and€1018, respectively, and repr......Page 507
INSTALLATION OF BALLAST.  Ballast is sometimes permanently installed for c.g. balance purposes as a result of installation or removal of equipment items and is not used to correct a nose-up or nose-down tendency of an aircraft.  It is usually located as......Page 508
Compute a separate loading condition when the aircraft is to be loaded in other than the specified conditions shown in the loading schedule.......Page 511
Ensure that ventilation and cooling air passages are clear and unobstructed.......Page 512
INSULATION OF ELECTRICAL EQUIPMENT.  In some cases, electrical equipment is connected into a heavy current circuit, perhaps as a control device or relay.  Such equipment is normally insulated from the mounting structure since grounding the frame of the e......Page 513
BUS BARS.  Annually check bus bars for general condition, cleanliness, and security of all attachments and terminals.  Grease, corrosion, or dirt on any electrical junction may cause the connections to overheat and eventually fail.  Bus bars that exhibit......Page 514
BATTERY FREEZING.  Discharged lead-acid batteries exposed to cold temperatures are subject to plate damage due to freezing of the electrolyte.  To prevent freezing damage, maintain each cell’s specific gravity at€1.275, or for sealed lead-acid batteries......Page 516
Mechanical Integrity.  Proper mechanical integrity involves the absence of any physical damage as well as assurance that hardware is correctly installed and the battery is properly connected.  Battery and battery compartment venting system tubes, nipples......Page 517
Lead-acid batteries are usually charged by regulated DC voltage sources.  This allows maximum accumulation of charge in the early part of recharging.......Page 518
ELECTROLYTE€SPILLAGE. Spillage or leakage of electrolyte may result in serious corrosion of the nearby structure or control elements as both sulfuric acid and potassium hydroxide are actively corrosive.  Electrolyte may be spilled during ground servicing......Page 519
Battery Sump Jars.  A battery sump jar installation may be incorporated in the venting system to dispose of battery electrolyte overflow.  The sump jar should be of adequate design and the proper neutralizing agent used.  The sump jar must be located onl......Page 520
Quick-Disconnect Type Battery.  If a quick-disconnect type of battery connector, that prohibits crossing the battery lead is not employed, ensure that the aircraft wiring is connected to the proper battery terminal.  Reverse polarity in an electrical sys......Page 521
Static power converters often emit unacceptable levels of EMI that may disrupt communication equipment and navigation instruments. Properly shielded connectors, terminal blocks, and wires may be required, with all shields well grounded to the airframe.......Page 522
When two or more generators and alternators are operated in parallel and the total connected system load can exceed the rated output of a single generator, a method should be provided for quickly coping with a sudden overload that can be caused by genera......Page 523
Wiring.  Junction box layouts should take into consideration the necessity for adequate wiring space and possible future additions. Electrical wire bundles should be laced or clamped inside the box so that cables do not touch other components, prevent re......Page 524
Automatic reset circuit breakers, that automatically reset themselves periodically, are not recommended as circuit protection devices for aircraft.......Page 526
Inductive circuits have magnetic energy stored in solenoid or relay coils that is released when the control switch is opened and may appear as an arc.......Page 527
Typical logic load devices have a voltage of 0.5€volts to 28€volts and a continuous current of less than 0.5€amps.  A suitable method of rating switches for use on logic load devices is specified in ANSI/EIA€5200000.  (General specification for special u......Page 528
Sealing.......Page 529
Operating a relay at less than nominal coil voltage may compromise its performance and should never be done without written manufacturer approval.......Page 530
OPERATING CONDITIONS FOR SWITCHES AND RELAYS.  Switches and relays should be compared to their specification rating to ensure that all contacts are made properly under all conditions of operation, including vibration equivalent to that in the area of the......Page 531
Values in tables€117 and€118 are for tin-plated copper conductor wires.  Because the resistance of tin-plated wire is slightly higher than that of nickel or silver-plated wire, maximum run lengths determined from these charts will be slightly less than......Page 532
Approximate T2 can be estimated using the following formula:......Page 533
Correct Size.  To select the correct size of electrical wire, two major requirements must be met:......Page 536
Procedures in Example No. 1  paragraph€1168c, can be used to find the wire size for any continuous or intermittent operation (maximum two minutes).  Voltage (e.g. 14€volts, 28€volts, 115€volts, 200€volts) as indicated on the left scale of the wire chart......Page 537
Use figure€116, find the derate factor for 8€wires in a bundle at 60€percent.  First find the number of wires in the bundle€(8) at bottom of graph and intersect with the 60€percent curve meet.  Read derating factor, (left side of graph) which is€0.6.  M......Page 538
Example 1.  Assume a harness (open or braided), consisting of 10 wires, size€#20, 200€?C rated copper and 25 wires, size€#22, 200€?C rated copper, will be installed in an area where the ambient temperature is 60€?C and the vehicle is capable of operating......Page 539
Example 2.  Assume a harness (open or braided), consisting of 12,€size€#12, 200€?C rated copper wires, will be operated in an ambient of 25€?C at sea level and 60€?C at a 20,000foot altitude.  All 12€wires will be operated at or near their maximum capac......Page 540
Authentic Aircraft Wire.  Most aircraft wire designs are to specifications that require manufacturers to pass rigorous testing of wires before being added to a Qualified Products List (QPL) and being permitted to produce the wire.  Aircraft manufacturers......Page 548
MIL-W-5088L, replaced by AS50881A, wiring aerospace vehicle, Appendix A lists wire types that have been approved for military......Page 549
The use of current military specification, multi-conductor cables in place of OEM installed constructions may create......Page 550
SHIELDED WIRE.  With the increase in number of highly sensitive electronic devices found on modern aircraft, it has become very important to ensure proper shielding for many electric circuits.  Shielding is the process of applying a metallic covering to......Page 552
Ensure that wires and cables are not tied or fastened together in conduit or insulating tubing.......Page 556
Separate wires from high-temperature equipment, such as resistors, exhaust stacks, heating ducts, etc., to prevent insulation breakdown.  Insulate wires that must run through hot areas with a high-temperature insulation material such as fiberglass or PTF......Page 557
Wiring that is known to have been exposed to electrolyte or on which the insulation appears to be, or is suspected of being, in an initial stage of deterioration due to the effects of electrolyte.......Page 558
All wires, terminal blocks, and individual studs are clearly identified to correspond to aircraft wiring manuals.......Page 559
Ensure that there is no evidence of deterioration such as cracking, missing, or disintegration of the potting material.......Page 560
JUNCTIONS.  Ensure that only aircraft manufacturer approved devices, such as solderless type terminals, terminal blocks, connectors, disconnect splices, permanent splices, and feed-through bushings are used for cable junctions.  Inspect for the provision......Page 561
Power input tests must be conducted with the equipment powered by the airplane’s electrical power generating system, unless otherwise specified.......Page 562
IDENTIFICATION STENCILS AND PLACARDS ON ELECTRICAL EQUIPMENT.  Replace worn stencils and missing placards.......Page 563
RF cables should not bend on a radius of less than six€times the outside diameter of the cable.......Page 564
Never use coaxial cable for a handle, lean on it, or hang things on it (or any other wire).......Page 565
MOVABLE CONTROLS WIRING PRECAUTIONS.  Clamping of wires routed near movable flight controls must be attached with steel hardware and must be spaced so that failure of a single attachment point can not result in interference with controls.  The minimum se......Page 568
FLAMMABLE FLUIDS AND GASES.  An arcing fault between an electrical wire and a metallic flammable fluid line may puncture the line and result in a fire.  Every effort must be made to avoid this hazard by physical separation of the wire from lines and equi......Page 569
Plastic ties should not be used between the service loop breakout and the electrical connector when they are likely to chafe against adjacent wire.......Page 570
Service Loop Harness Termination.  Strain relief should be provided at the service loop harness termination, and is normally provided by the connector manufacturer’s backshell, heat-shrinkable boot, or tubing.......Page 571
the electronic equipment to prevent strain at the cable terminals and to minimize adverse effects on shock-mounted equipment.......Page 572
LACING AND TIES.  Ties, lacing, and straps are used to secure wire groups or bundles to provide ease of maintenance, inspection, and installation.  Braided lacing tape per MILT43435 is suitable for lacing and tying wires.  In lieu of applying ties, str......Page 576
INSULATION TAPE.  Insulation tape should be of a type suitable for the application, or as specified for that particular use.  Insulation tape should be used primarily as a filler under clamps and as secondary support.  Nonadhesive tape may be used to wra......Page 577
Selection of proper crimping tool, refer to paragraph 11-178.......Page 580
Terminal Lugs.  Wire terminal lugs should be used to connect wiring to terminal block studs or equipment terminal studs.  No more than four terminal lugs or three terminal lugs and a bus bar should be connected to any one stud.  Total number of terminal......Page 582
Size of Studs.  In designing the stud for a feed-through connection, attention should be given to the higher resistance of brass, as compared to copper.  A suggested method of determining the size is to use a current density in the stud equivalent to tha......Page 583
The tool calibration and adjustments are make only by the manufacturer or an approved calibration laboratory.......Page 584
LOCK WASHERS FOR TERMINALS ON EQUIPMENT.  Where locknuts are used to ensure binding and locking of electrical terminals, they should be of the all metal type.  In addition, a spring lock washer of suitable thickness may be installed under the nut to ensu......Page 585
Heavy-Current Grounds.  Power ground connections, for generators, transformer rectifiers, batteries, external power receptacles, and other heavy-current, loads must be attached to individual grounding brackets that are attached to aircraft structure with......Page 586
The effect of the interconnection of the circuits when ungrounded should be considered whenever a common ground connection is used.  This is particularly important when employing terminal junction grounding modules or other types of gang grounds that hav......Page 587
Bonding jumpers should be installed in such a manner as not to interfere in any way with the operation of movable components of the aircraft.......Page 588
Use appropriate washers when bonding aluminum or copper to dissimilar metallic structures so that any corrosion that may occur will be on the washer.......Page 589
CREEPAGE DISTANCE.  Care should be used in the selection of electrical components to ensure that electrical clearance and creepage distance along surfaces between adjacent terminals, at different potentials, and between these terminals and adjacent groun......Page 590
Table 11-14. Stud bonding or grounding to flat surface.......Page 591
LIGHTNING€PROTECTION BONDING.  Electrical bonding is frequently required for lightning protection of aircraft and systems, especially to facilitate safe conduction of lightning currents through the airframe.  Most of this bonding is achieved through norm......Page 595
HARDWARE ASSEMBLY.  Details of bonding  connections must be described in maintenance manuals and adhered to carefully when connections are removed or replaced during maintenance operations.  In order to avoid corrosion  problems and ensure long-term inte......Page 596
Indirect marking is accomplished by printing a heat-shrinkable sleeve and installing the printed sleeve on the wire or cables outer covering.  Indirectmarked wire or cable should be identified with printed sleeves at each end and at intervals not longer......Page 598
Alternative identification methods such as “Laser Printing”, “Ink Jet”, and “Dot Matrix” are preferred. When such modern equipment is not available, the use of stamped identification sleeving should be considered on insulation wall thickness of 10€mils o......Page 599
IDENTIFICATION SLEEVES.......Page 600
IDENTIFICATION OF WIRE BUNDLES AND HARNESSES.  The identification of wire bundles and harnesses is becoming a common practice and may be accomplished by the use of a marked sleeve tied in place or by the use of pressure-sensitive tape as indicated in fig......Page 601
SLEEVES AND CABLE MARKERS SELECTION.  Sleeves and cable markers must be selected by cable size and operating conditions.  (See tables€1118 through€1121).......Page 602
Thread the tie-down straps through holes in marking plate and around cable. Thread tip of tie-down strap through slot in head.  (See figure€1129.)  Pull tip until strap is snug around cable.......Page 603
Table 11-21. Selection table for cable markers.......Page 604
Hold marker, printed side up, and press end of wire on lip of sleeve to open sleeve.  (See figure€1133.)......Page 605
Shrink marker  sleeve, using heat gun with shrink tubing attachment.  (See figure€1134.)......Page 606
Environmental Classes.  Environment-resistant connectors are used in applications where they will probably be subjected to fluids, vibration, thermal, mechanical shock, corrosive elements, etc.  Firewall class connectors incorporating these same features......Page 608
Module Blocks.  These junctions accept crimped contacts similar to those on connectors.  Some use internal busing to provide a variety of circuit arrangements.  They are useful where a number of wires are connected for power or signal distribution.......Page 609
Drainage.  Connectors must be installed in a manner which ensures that moisture and fluids will drain out of and not into the connector when unmated.  Wiring must be routed so that moisture accumulated on the bundle will drain away from connectors.  When......Page 615
POTTING CONNECTORS.......Page 616
THROUGH BOLTS.  Through bolts are sometimes used to make feeder connections through bulkheads, fuselage skin, or firewalls.  Mounting plates for through bolts must be a material that provides the necessary fire barrier, insulation, and thermal properties......Page 617
Table 11-23. Bend radii for rigid conduit.......Page 619
Table 11-24. Minimum bending radii for flexible aluminum or brass conduit.......Page 620
Unsealed Connector Installations.  It is not required to fill unused contact cavities of unsealed connectors installed in pressurized areas with Teflon sealing plugs or rods.  Installation of spare contacts is optional, except for future wiring addition......Page 621
Table 11-26. Sealing rod  dimensions.......Page 622
Table 11-27. Electronic/Electrical Symbols.......Page 623
Table 11-27. Electronic/Electrical Symbols (continued).......Page 624
Table 11-27. Electronic/Electrical Symbols (continued).......Page 625
Table 11-27. Electronic/Electrical Symbols (continued).......Page 626
Table 11-27. Electronic/Electrical Symbols (continued).......Page 627
Table 11-27. Electronic/Electrical Symbols (continued).......Page 628
Table 11-27. Electronic/Electrical Symbols (continued).......Page 629
Table 11-27. Electronic/Electrical Symbols (continued).......Page 630
Table 11-27. Electronic/Electrical Symbols (continued).......Page 631
Table 11-27. Electronic/Electrical Symbols (continued).......Page 632
Table 11-27. Electronic/Electrical Symbols (continued).......Page 633
Table 11-27. Electronic/Electrical Symbols (continued).......Page 634
Table 11-27. Electronic/Electrical Symbols (continued).......Page 635
HANDLING OF COMPONENTS.  Any unit containing electronic components such as transistors, diodes, integrated circuits, proms, roms, and memory devices should be protected from excessive shocks.  Excessive shock can cause internal failures in an of these co......Page 637
cracked antenna housing......Page 639
Perform a function check of the radio by transmitting a request for a radio check.  Perform a function check on navigation equipment by moving the omni bearing selection (OBS) and noting the needle swing and the TO/FROM flag movement.......Page 640
at a different frequency.  The aircraft unit measures the time it takes to transmit and then receive the signal, which then is translated into distance.  DME operates on frequencies from 962€MHz to 1213€MHz.  Because of the curvature of earth, this line-......Page 641
MARKER BEACON.  Marker beacon receivers operate at 75€MHz and sense the audio signature of each of the three types of beacons.  The marker beacon receiver is not tunable.  The blue outer marker light illuminates when the receiver acquires a 75€MHz signal......Page 642
Examine the altimeter face for evidence of needle scrapes or other damage.  Check smoothness of operation, with particular attention to altimeter performance during decent.......Page 643
Battery Corrosion.  Gain access to the ELT battery and inspect.  No corrosion should be detectable.  Verify the ELT battery is approved and check its expiration date.......Page 644
Conditions for tape replacement (as applicable):......Page 645
WEATHER RADAR.  Ground performance shall include antenna rotation, tilt, indicator brilliance, scan rotation, and indication of received echoes.  It must be determined that no objectionable interference from other electrical/electronic equipment appears......Page 646
System impedance matching.......Page 647
Have the aircraft taxied to the NORTH (0() radial on the Compass Rose.  Use a hairline sight compass (a reverse reading compass with a gun sight arrangement mounted on top of it) to place the aircraft in the general vicinity.  With the aircraft facing No......Page 649
Standby (wet) Compass.  Adjustment and compensation of the Standby Compass may also be accomplished by using the “compass swing” method.......Page 650
There are two sizes of venturi tubes: those which produce four inches of suction are used to drive the attitude gyros, and smaller tubes, which produce two inches of suction, are used for the turn and slip indicator. Some installations use two of the lar......Page 651
Positive Pressure Systems.  Above about 18,000€feet there is not enough mass to the air drawn through the instruments to provide sufficient rotor speed, and, to remedy this problem, many aircraft that fly at high altitude use positive pressure systems to......Page 652
from the cabin where there is usually a good deal of dust and very often tobacco smoke.  Unless all of the solid contaminants are removed from the air before it enters the instrument, they will accumulate, usually in the rotor bearings, and slow the roto......Page 653
Inspect air passages in the systems for water, paint, dirt or other foreign matter.  If water or obstructive material has entered the system, all drains should be cleaned.   Probe the drains in the pitot tube with a fine wire to remove dirt or other obst......Page 655
Pitot-static leak tests should be made with all instruments connected to assure that no leaks occur at instrument connections.  Such tests should be accomplished whenever a connection has been loosened or an instrument replaced.......Page 656
MAINTENANCE PRECAUTIONS.  Observe the following precautions in all pitot-static system leak testing:......Page 657
CODE......Page 658
The circuit breaker trips again, if so:......Page 659
If the manufacturer’s manual does not describe a test procedure, the repair station must coordinate with the manufacturer to develop the necessary procedures, prior to any use of the equipment.......Page 661
into a personal minimums checklist, which asks the mechanic to answer 10 ‘yes or no’ questions before the maintenance task is begun and 10 ‘yes or no’ questions after the task is completed. If the mechanic answers “NO” to any of the 20 questions, the air......Page 663