Page 66 АС 43.13- "I" more than twice the width "W," and the rivets spread out to cover the plate.
101. REPAIRING CRACKED MEMBERS. Acceptable methods of repairing various types of cracks in structural elements are shown in figures 2.82 to 2.35. The following general procedures apply in repairing such defecta:
a. Drill small holes 3/82 inch (or 1/8 inch) at the extreme ends of the cracks to minimize the possibility of their spreading further.
b. Add reinforcement to carry the stresses across the damaged portion and to stiffen the joints (as shown in figures 2.82 to 2.35).
The condition causing cracks to develop at a particular point is stress concentration at that point in conjunction with repetition of stress, such as produced by vibration of the structure.
The stress concentration may be due to the q sign or to defects such as nicks, scratches, to marks, and initial stresses or cracks fro forming or heat-treating operations. It shou be noted, that an increase in sheet thickne alone is usually beneficial, but does not nece sarily remedy the conditions leading to crac ing.
102. STEEL AND ALUMINUM FITTINGS.
a. Steel Fittings-Inspection for Defects.
(1) Finings are to be free from scratche vise and nibbler marks, and sharp bends ‹ edges. A careful examination of the fitting wit a medium power (at least 10 power) magnif ing glass is acceptable as an inspection.
(2) When repairing aircraft after an accide or in the course of a major overhaul, inspe FIGURE 2.30.-Number of rivets required for splices (single-lap joint) in 5052 (all hardnesses) sheet.
Thictness "t" in inches No. of 2117-AD protruding head rivets required per inch of width "p" No. of bolt AN-31
0.016-. 6. 3 1, 7 .020_. В. з 4.7 3. 8 .025__ 6. 8 3. 8 .032_. 6. 3 4, 7 3. 8 3. 2 .036__. 7.1 4.7 8. 8 3. 2 2.4 .040__ 7. 0 4. 7 3. 8 3. 2 2.4 .051-. 10. 1 5. 6 3. 8 3. 2 2,4 .064_ 12.7 7.0 46 3. 2 .081_. & 9 5. 8 2 .091-- 10. 0 6. 5 .102_ 11. 2 7. 3 .128_ 9. 2 NOTES:
a. For stringers in the upper surface of a wing, or in a fuselage, 80 percent of the number of rivets shor table may be used.
b. For intermediate frames, 60 percent of the number shown may be used.
c. For single lap sheet jointe, 75 percent of the number shown may be used.
ENGINEERINO NOTES: The above table was compuled as follows:
1. The load per inch of width of material was calculated by assuming a strip one inch wide in tension.
2. Number of rivets required was calculated for 2117-AD rivets, based on & rivet allowable shear stre.
70 percent of the sheet allowable tensile stress, and a sheet allowable bearing stress equal to 165 percent of allowable tensile stress, using nominal hole diameters for rivete
3. Combinations of sheet thickness and rivet size above the heavy line are critical in (l.e., will fall by) be the sheet; those below are critical in shearing of the rivets.
Par 100
13.13-14 Page 6?
THE NUMBER OF RIVETS REQUIRED IN EACH LEG ON EACH SIDE OF THE CUT AND THE NET DIAMETER TH USING HIG. 22) IN DE ANNER SIMILAR TO THAT FOR STRINGERS IN FIG. 2.26.
NOTE b. IN FIG. 2.29 INDICATES THAT ONLY 60% OF THE NUMBER OF
RIVETS SO CALCULATED NEED BE USED IN SPLICES IN INTERMEDIATE FRAMES EXAMPLE (For 2017-T3 aluminum alloy frame)
FLANGE LEG
• = „040"
(2.0) W, & W. = .6 inch d = 1/8" 2117-AD rivel 6) NO. OF RIVETS PER INCH OF WIDTH FROM FIG. 2.29 = 6.2 No. of rivets required = W × 6.2 =
•6 × 6.2 = 3.72 or 4 rivets.
60% of 4 rivets = 2.4 rivets.
USE 3 RIVETS ON EACH SIDE OF THE CUT IN EACH FLANGE LEG.
WEB OF ZEE (OR CHANNEL) + = „040" d = 1/8" 2117-AD rivet W = 2.0 inches NO. OF RIVETS PER INCH OF WIDTH FROM FIG. 2.29 = 6.2 No. of rivets required = W x 6.2 =
2.0 x 6.2 =12.4 or 13 rivets.
60% of 13 rivets = 7.8 rivets.
USE 8 RIVETS ON EACH SIDE OF CUT IN THE WEB OF ZEE (OR CHANNEL).
SHOULD BE MORE THAN TWICE We hickness of splice plate to be greater than that of the frame to be spliced.
FIGURE 2.81.—Example of splice of intermediate frame (material 2017 AL alloy).
Par 102
Page 68 AC 43.13
CHANNELS
TRAILING
FORWARD EDGE
HORIZONTAL
RIBS SKIN
OVESTARL CRACKS
CRACKS' ANCHOR
NUTS FOR RIB
ATTACH-
MENT OF
FIN TO SKIN
STABILIZER
AND TIP TO FIN CRACK
TRAILING EDGE
REAR SHEAR
FRONT BEAM SPAR CRACKS
LEADING EDGE AILERO:
NOTE: ALL REINFORCING PLATES TO BE OF REAR SAME ALLOY & APPROX. 1.5 THICKNESS OF ORIGINAL.
FiGURE 2.32. -Typical methoda of repairing cracked leading and trailing edges and rib intersections.
Par 102
END RIE REAR SPAR
CONTROL
STIFFENING CHANNEL TO SURFACE
FIT UNDER END OF RIB, FITTING
REINFORCEMENT AND UNDER ANCHOR NUT. MATERIAL DRILL REL " DIA.)
SAME ALLOY AS ORIGINAL, APPROX. HOLES 1/8
1.5 THICKNESS OF ORIGINAL OR GREATER.
RIVETS JOINING SPAR WEB WITH FRONT
AND REAR CHANNEL TYPE REINFORCEMENT
NOTCHED MEMBER
CRACKS AT
FITTING ANCHOR NUTS
TRAILING EDGE
PORTION OF RIB TORILL RELIEF HOLE
SHEAR REAR PEAR
REINFORCING PLATE - BEAM
WITH FILLETED NOTCH
MATERIAL OF REINFORCING PLATES SAME ALLOY AS ORIGINAL AND 1.5 (OR MORE) × THIGKNESS OF ORIGINAL. FLAP HINGE FIoURE 2.88.-Typical methods of replacing cracked members at fittings.
Par 103
Page 70 AC 43
ORACKS IN SKIN AND
TRANSVERSE STIFFENER
AT DRAG RIB JUNCTION
IEPAIR SY OUTSIDE GUSSE TRANSVERSE STIFFENeR
LONGITUI _ORAOK DUE
DRAG I REINFORCE-)
MENT TO DE REPAIR OF GRACKED
SAME MATERIAL STIFFENER
AND AT LEAST
SAME AREA AS
TRANSVERSE
STIFFENER
FAILURES
SECTION A-A FIGURE 2.34.-Typical methods of repairing cracked frame and stiffener combinat Par 102
1.13-1A Page 71 FRONT SPAR HORN RIB BOTTOM
FUSELAGE (TOP)
FAILURES
FUSELAGE (SIDE) USE SAME MATERIAL, NEXT HEAVIER GAUGE FOR REINFORGEMENT.
FIoURE 2.86.-Typical repairs to rudder and to fuselage at tail post.
Par 102
Page 72 AC 43 +→#‡ BUSHING
ELONGATED OR WORN.
TAPER WASHER OF 4130 ADDED. THICKNESS NOT LESS THAN 1.5 t OR 167 GREATER THAN 2t.
ELONGATED
HOLE IN
ORIGINAL REMOVE STRUT. ORIGINAL WASHER 2 NOTES:
16 R=M - iG I. METHODS A OR B MAY BE USED IN REPAIRIN TYPE C STRUT ENDS.
2. METHOD B SHOULD BE USED IN REPAIRIN TYPE D & E STRUT ENDS.
3. MEMBERS ORIGINALLY HEAT TREATED M
BE REHEAT-TREATED AFTER WELDING, FIGURE 2.36.-Typical methods of repairing elongated or worn boltholes.
Par 102
43.12-1A CHG 1 highly stressed main fittings, as set forth in apter 7, and if necessary, take corrosion vention measures as recommended in Chap-
(3) Replace torn, kinked, or cracked fittings.
(4) Elongated or worn boltholes in fittings ich were designed without bushings are not be reamed oversize. Replace such fittings, ess the method of repair is approved by a resentative of the FAA. Do not fill holes h welding rod. Acceptable methods of rering elongated or worn boltholes in landing r, stabilizer, interplane, or cabane-strut ends y, not originally equipped with pin plates, are wn in figure 2.36. (Also see figure 2.11 on geron repair at fitting.)
. Aluminum and Aluminum Alloy Fittings.
(1) Replace damaged fittings with new parts, ring the same material specifications.
(2) Repairs may be made in accordance with a furnished by the aircraft manufacturer or a substantiating the method of repair may be mitted to the FAA for review.
1. CASTINGS. Damaged castings are to be reced and not repaired unless the method of air is specifically approved by the aircraft nufacturer or substantiating data for the rer has been reviewed by the FAA.
I. SELECTIVE PLATING IN AIRCRAFT MAINTE- NCE. Selective plating is a method of depositmetal from an electrolyte to the selected The electrolyte is held in an absorbent terial attached to an inert anode. Plating tact is made by brushing or swabbing the * (cathode) with the electrolyte-bearing Selective Plating Uses. This process can be I for any of the following reasons:
Co prevent or minimize disassembly, reor masking costs.
sizing worn components (plate to size).
ing in damaged or corroded areas.
plate small areas of extremely large plate electrical contacts.
plate parts too large for existing Page 73
(7) To supplement conventional plating.
(8) To plate components which become contaminated if immersed in a plating bath.
(9) To cadmium-plate ultra high strength steels without hydrogen embrittlement.
(10) On-site plating.
(11) Reverse current applications (e.g., stain removal, deburring, etching, dynamic balancing).
b. Specifications. Selective plating (electrodeposition), when properly applied, will meet the following specifications and standards:
2Q-C-320 Chromium Plating QQ-N-290 Nickel Plating QQ-P-416 Plating, Cadmium QQ-5-865 Silver Plating QQ-Z-325 Zinc Plating MIL-T-10727 Tin Plating MIL-C-14550 Copper Plating MII-G-45204 Gold Plating
c. General Requirements.
(1) Areas to be repaired by this process should be limited to reasonably small areas of large parts, although it may be desirable to plate small parts, particularly electrical or electronic parts, in their entirety.
(2) All solutions should be kept clean and free from contamination. Care should be taken to insure that the solutions are not contaminated by used anodes or other plating solutions. Brush plating solutions are not designed to remove large amounts of scale, oil, or grease. Mechanical or chemical methods should be used to remove large amounts of scale or oxide. Use solvents to remove grease or oil.
(3) Brush plating solutions are five to fifty times as concentrated as tank solutions. The current densities used range from 500 to 4,000 amps/feet?. The voltages listed on the solution bottles have been precalculated to give proper current densities. Too high a current density burns the plating, while too low a current density produces stressed deposits and low efficiencies.
Agitation is provided by anode/cathode motion.
Too fast a motion results in low efficiencies and stressed deposits; too slow a motion causes burning. A dry tool results in burnt plate, coarse grain structure, and unsound deposits. The tool* Par 102
* cannot be too wet. Solution temperatures of 110° to 120° F. are reached during operation.
(4) Materials such as stainless steel, aluminum, chromium, and nickel, which have a passive surface, will require an activating operation to remove the passive surface. During the activating process, do not use solutions that have been previously used with reverse current because of solution contamination.
d. Equipment. The power source should operate on either 110 or 220 volt alternating current (AC), 60 Hertz, single phase input. It should have a capability to produce direct current having smooth characteristics with controlled ripple and be able to output a current of at least 25 amperes at 0 to 25 volts. Minimum instrumentation of the power source should include a voltmeter, ammeter, and ampere-hour meter.
(1) The ammeter should provide a full scale reading equal to the maximum capacity of the power source with an accuracy of +5 percent of the current being measured.
(2) The voltmeter should have sufficient capacity to provide a full scale reading equal to the maximum capacity of the power source and an accuracy of +1.0 volt.
(3) An ampere-hour meter should be readable to 0.001 ampere-hour and have an accuracy of 10.01 ampers-hour.
(4) The stylus should be designed for rapid cooling and to hold anodes of various sizes and configurations. For safety, the anode holder should be insulated.
(5) The containers for holding and catching runoff solutions should be designed to the proper configuration and be inert to the specific solution.
(6) The mechanical cleaning equipment and materials should be designed and selected to prevent contamination of the parts to be cleaned.
e. Materials. The anodes should be of highpurity dense graphite or platinum-iridium alloys.
Do not mix solutions from different suppliers.
This could result in contamination.
f. Detail Requirements. On large parts, no area greater than approximately 10 percent of the total area of the part should be plated by this process. Small parts may be partially or completely plated. Special cases exceeding these Par 104 AC 43.13-1A CI limitations should be coordinated with the ma facturer of the plating equipment being used :
his recommendations should be followed.
g. Anode Selection. As a general guide, contact area of the anode should be appr mately one-third the size of the area to be plat When selecting the anode, the configuration the part will dictate the shape of the anode,
h. Required Ampere-Hour Calculation.
selected plating solution has a factor which equal to the ampere-hours required to dep
0.0001 inch on one square inch of surface. :
termine the thickness of plating desired or certain area and multiply the solution fac times the plating thickness times the area square inches to determine the ampere-hours quired. This factor may vary because of te I. Cleaning. Remove corrosion, scale, oxi and unacceptable plating prior to processi Use a suitable solvent or cleaner to remove gre or oil.
I. Plating on Aluminum and Aluminum Bi Alloys.
(1) Electroclean the area using forw (direct) current until water does not break the surface. This electroclean process should accomplished at 10 to 15 volts, using the app priate electroclean solution.
(2) Rinse the area in cold clean tap water.
(3) Activate the area with reverse curre 7 to 10 volts, in conjunction with the proj activating solution until a uniform gray to bla surface is obtained.
(4) Rinse thoroughly in cold, clean tap wat
(5) Immediately electroplate to color wh the area is still wet, using the appropriate nic solution.
(6) Rinse thoroughly.
(7) Immediately continue plating other solution to desired thickness.
(8) Rinse and dry.
k. Plating on Copper and Copper i
(1) Electroclean the area usin (direct) current until water does no the surface. The electroclean process accomplished at 8 to 12 volts using t.
priate electroclean solution.
43.13-1A CHG 1
(2) Rinse the area in cold, clean tap water.
(3) Immediately electroplate the area with y of the plating solutions except silver. Silver quires an undercoat.
(4) Rinse and dry.
I. Plating on 300 and 400 Series Stainless Steels, ckel Base Alloys, Chrome Base Alloys, High ckel Ferrous Alloys, Cobalt Base Alloys, Nickel ate, and Chrome Plate.
(1) Electroclean the area using forward irect) current until water does not break on e surface. This electroclean process should be complished at 12 to 20 volts using the approiate electrocleaning solution.
(2) Rinse the area in cold, clean tap water.
(3) Activate the surface using forward lirect) current for 1 to 2 minutes using the tivating solution and accomplish at 6 to 20 Its.
(4) Do not rinse.
(5) Immediately nickel flash the surface to thickness of 0.00005 to 0.0001 inch using the propriate nickel solution.
(6) Rinse thoroughly.
(7) Immediately continue plating with any her solution to desired thickness.
(8) Rinse and dry.
m. Plating on Low-Carbon Steels (Heat Treated 180,000 psi).
(1) Electroclean the area using forward irect) current until water does not break on e surface. This electroclean process should be complished at 12 to 20 volts using the approiate electrocleaning solution.
(2) Rinse the aren in cold, clean tap water.
(3) Reverse current etch at & to 10 volts, the appropriate activating solution, until form gray surface is obtained.
Rinse thoroughly.
mediately electroplate the part using ns except copper acid or silver. Both re undercoats.
se and dry.
ig on Cast Iron and High-Carbon Steels at Treated to 180,000 psi).
flectroclean the area using forward current until water does not break on Page 73-2 the surface. This electroclean process should be accomplished at 12 to 20 volts using the appropriate electrocleaning solution.
(2) Rinse the area thoroughly in cold, clean tap water.
(3) Reverse current etch at & to 10 volts, using the appropriate etching solution, until a uniform gray is obtained.
(4) Rinse thoroughly.
(5) Remove surface smut with 15 to 25 volts using the appropriate activating solution.
(6) Rinse thoroughly.
(7) Electroplate immediately using any of the solutions except copper or silver (both these require undercoats).
(8) Rinse and dry,
o. Plating on Ultra High Strength Steels (Heat Treated Above 180,000 psi).
(1) Electroclean the area using REVERSE current until water does not break on the surface.
This electroclean process should be accomplished at 8 to 12 volts using the appropriate electroclean solution.
(2) Rinse the area thoroughly in cold, clean tap water.
(3) Immediately electroplate the part, using either nickel, chromium, gold, or cadmium. Other metals require an undercoat of one of the above.
Plate initially at the highest voltage recommended for the solution so as to develop an initial barrier layer. Then reduce to standard voltage.
(4) Rinse and dry.
(5) Bake the part for 4 hours at 375° +25° F.
NoTF 1: Where the solution vendor provides sub stantiating data that hydrogen embrittlement will not result from plating with a particular solution, then a post bake Is not required. This substantlating data can be in the form of aircraft Industry manufacturers' process specifications, military specifications, or other suitable data.
NoTE 2: Acid etching should be avoided, if pos sible. Where etching is absolutely necessary, It should always be done with reverse current. Use alkaline solutions for initial deposita.
p. Dissimilar Metals and Changing Base.
a general rule, when plating two dissimilar metals, follow the plating procedure for the one with the most steps or activation. If activating* Par 104
* steps have to be mixed, use reverse current activation steps prior to forward (direct) current.
activation steps.
q. Plating Solution Selection.
(1) Alkaline and neutral solutions are to be used on porous base metals, white metals, highstrength steel, and for improved coating ability.
Acid solutions are to be used for rapid buildup and as a laminating structure material in conjunotion with alkaline type solutions.
(2) Chrome brush plating solutions do not yield as hard a deposit as bath plating solutions.
The hardness is about 600 Brinell as compared to 1,000 Brinell for hard chrome deposited from a tank.
(3) Silver immersion deposits will form with no current flowing on most base metals from the silver brush plating solutions; such deposits have poor adhesion to the base metal. Consequently, a flash or a more noble metal should be deposited prior to silver plating to develop a good bond.
(4) In general, brush plating gives less hydrogen embrittlement and a lower fatigue strength loss than does equivalent tank deposits.
However, all brush-plated, ultra high strength steel parts (heat treated above 180,000 psi) Par 104 AC 43.13-1A CI should be baked as mentioned in paragr
104.0.(5), unless it is specifically known t embrittlement is not a factor.
r. Qualification Tests. All brush plated t faces shall be tested for adhesion of the elec deposit. Apply a 1-inch wide strip of Minnes Mining and Manufacturing tape code 250, or approved equal, with the adhesive side to freshly plated surface. Apply the tape v heavy hand pressure and remove it with quick motion perpendicular to the plated t face. Any plating adhering to the tape shall cause for rejection.
s. Personnel Training for Quality Cont Manufacturers of selective plating equipm provide training in application techniques their facilities. Personnel performing select plating must have adequate knowledge of methods, techniques, and practices invol These personnel should be products of th training programs and certified as qualified erators by the manufacturers of the prod used, as well as by local quality control deps
105.-114. RESERVED.
Page 74 AC 43.13 Section 4. REPAIR OF LAMINATE STRUCTURES
115. GENERAL. There is a wide variation in the composition and structural application of laminates, and it is essential that these factors be given major consideration when any restoration activities are undertaken. To a similar extent, there also exist many types of laminate structure repairs that may or may not be suitable for a given condition. For this reason, it is important that the aircraft or component manufacturer's repair data be reviewed when determining what specific type of repair is permissible and appropriate for the damage at The materials used in the repair of laminate structures must preserve the strength, weight, aerodynamic characteristics, or electrical properties of the original part or assembly. This . can best be accomplished by replacing damaged material with material of identical chemical composition or a substitute approved by the manufacturer.
In order to eliminate dangerous stress concentrations, avoid abrupt changes in cross-sectional areas. Whenever possible, for scari joints and jacings, make small patches round or oval-shaped, and round the corners of large repairs. Smooth and properly contour aerodynamic surfaces.
It is recommended that test specimens be prepared at the same time that the actual repair is accomplished. These can then be subjected to a destructive test to establish the quality of the adhesive bond in the repaired part. To make this determination valid, the specimens must be assembled with the same adhesive batch mixture and subjected to curing pressure, temperature, and time identical with those in the actual repair.
a. Fiberglass Laminate Repairs. The following repairs are applicable to fiberglass laminate used for fairings, covers, cowlings, honeycomb panel facings, etc. Prior to undertaking the re- Par 115 pair, clean the repair area thoroughly with castile soap and warm water. Remove a paint by wet or dry sanding methods. Se blasting may be used but caution must be ex cised to not abrade the surfaces excessively.
Superficial scars, scratches, surface abi sion, or rain erosion can generally be repair by applying one or more coats of a suital resin, catalyzed to cure at room temperatu to the abraded surface. The number of co required will depend upon the type of re and severity of the damage.
Damage not exceeding the first layer or of fiberglass laminate can be repaired by fil with a putty consisting of a compatible ro temperature-setting resin and clean short gl fibers. Before the resin sets, apply a sheet cellophane over the repair area and work c any bubbles and excess resin. After the res has cured, sand off any excess and prepare t area for refinishing.
Damage deep enough to seriously affect t strength of the laminate (usually more th the first ply or layer of fabric) may be 1 paired as illustrated in figure 2.87. Coat t
DAMAGE TO FACING
DAMAGED MATERIAL /REMOVED BY SANDIN . REPLACED LAMINATIONS
SANDED TO CONTOUR FIGURE 2.37.-Typical laminate (facing) repair.
Chaj