Par 4-62 Page 4-144
THE NUMBER OF RIVETS REQUIRED IN EACH LEG ON EACH SIDE OF THE CUT IS DETERMINED BY THE WIDTH “W,” THE TH ICKNESS OF THE FRAME “t,” AND THE RIVET DIAMETER “d” USING TABLE 4-10 IN A MANNER SIMILAR TO THAT FOR STRINGERS IN FIGURE 4-20.
NOTE b. IN TABLE 4-10 INDICATES THAT ONLY 60 PERCENT OF THE NUMBER OF RIVETS SO CALCULATED NEED BE USED IN SPLICES IN INTERMEDIATE.
EXAMPLE: (FOR 2017-T3 aluminum alloy frame)
FLANGE LEG
t = .040” d = 1/8” 2117-T4 (AD) W1 & W 3 = .6 inch
NO. OF RIVETS PER INCH OF WIDTH FROM TABLE 4-10 = 6.2
No. of rivets required = W x 6.2 = .6 x 6.2 = 3.72 or 4 rivets.
60 percent of 4 rivets = 2.4 rivets.
USE 3 RIVETS ON EACH SIDE OF THE CUT IN EACH FLANGE LEG.
WEB OF ZEE (OR CHANNEL)
t = .040” d = 1/8” 2117-T4 (AD) rivet W = 2.0 inches
NO. OF RIVETS PER INCH OF WIDTH FROM TABLE 4-10 = 6.2
No. of rivets required = W x 6.2 =
2.0 x 6.2 = 12.4 or 13 rivets.
60 percent of 13 rivets = 7.8 rivets.
USE 8 RIVETS ON EACH SIDE OF CUT IN THE WEB OF ZEE (OR CHANNEL).
“L” SHOULD BE MORE THAN TWICE W2 Thickness of splice plate to be greater than that of the frame to be spliced.
FIGURE 4-20. Example of intermediate frame stringer splice (material 2017-T3 AL alloy).
CHANNELS
TRAILING FORWARD. EDGE
HORIZONTAL
RIBS SKIN
OVERTICAL SPAR CRACKS CRACKS ANCHOR
NUTS FOR RIB
ATTACH-
MENT OF
FIN TO SKIN
STABILIZER
AND TIP CRACK TO FIN
TRAILING EDGE
REAR SHEAR
FRONT BEAM SPAR CRACKS
LEADING EDGE
AILERON NOTE: ALL REINFORCING PLATES TO BE OF REAR → SAME ALLOY & APPROX. 1.5 THICKNESS OF ORIGINAL.
FIGURE 4-21. Typical methods of repairing cracked leading and trailing edges and rib intersections.
Par 4-62 Page 4-145
END RIB REAR SPAR
CONTROL
STIFFENING CHANNEL TO SURFACE
FIT UNDER END OF RIB, FITTING REINFORCEMENT AND UNDER ANCHOR NUT. MATERIAL: DRILL RELIEF DIA.)
SAME ALLOY AS ORIGINAL, APPROX. HOLES • 71/8
1.5 THICKNESS OF ORIGINAL OR GREATER.
RIVETS JOINING SPAR WEB WITH FRONT
AND REAR CHANNEL TYPE REINFORCEMENT
NOT CHED MEMBER
CRACKS AT
FITTING ANCHOR NUTS
TRAILING EDGE
PORTION OF RIB DRILL
TRELIEF HOLE REAR
SHEAR PEAR
REINFORCING PLATE BEAM
WITH FILLETED NOTCH
MATERIAL OF REINFORCING PLATES SAME ALLOY AS ORIGINAL AND 1.5 (OR MORE) × THICKNESS OF ORIGINAL. FLAP HINGE FIGURE 4-22. Typical methods of replacing cracked members at fittings.
Par 4-62 Page 4-146
CRACKS IN SKIN AND → AT DRAGG RIB JUNCTION (REPAIR BY OUTSIDE GUSSETS) TRANSVERSE STIFFENER
DRAG RIB
TRANSVERSE STIFFENER
LONGITUDINAL STIFFENER
CRACK DUE TO FATIGUE
DRAG RIB SPAN MENT TO BE / REINFORCE REPAIR OF CRACKED SAME MATERIAL STIFFENER.
AND AT LEAST
SAME AREA AS
TRANSVERSE STIFFENER.
FAILURES
SECTION A-A FIGURE 4-23. Typical methods of repairing cracked frame and stiffener combination.
Par 4-62 Page 4-147
FRONT SPAR HORN RIB BOTTOM
FUSELAGE (TOP)
FAILURES
FUSELAGE (SIDE) NOTE: USE SAME MATERIAL, NEXT HEAVIER GAUGE FOR REINFORCEMENT.
FIGURE 4-24. Typical repairs to rudder and to fuselage at tail post.
Par 4-62 Page 4-148
+ - BUSHING ELONGATED OR WORN.
2 TAPER WASHER OF 4130 ADDED. THICKNESS = NOT LESS THAN 1.5t OR GREATER THAN 2t - t 16
ELONGATED
HOLE IN
ORIGINAL REMOVE STRUT. ORIGINAL WASHER 2 NOTES:
16 R = M-16 1. METHODS A OR B MAY BE USED IN REPAIRING 3. MEMBERS ORIGINALLY HEAT TREATED MUST TYPE C STRUT ENDS. BE REHEAT TREATED AFTER WELDING.
2. METHOD B SHOULD BE
USED IN REPAIRING TYPE D & E STRUT ENDS.
FIGURE 4-25. Typical methods of repairing elongated or worn bolt holes.
Par 4-62 Page 4-149
Par 4-62 Page 4-150 To prevent or minimize disassembly, or reassembly.
Resizing worn components (plate to size).
Filling in damaged or corroded areas.
To plate small areas of extremely large parts.
To plate electrical contacts.
To plate parts too large for existing baths.
To supplement conventional plating.
To plate components which become contaminated if immersed in a plating bath.
To cadmium-plate ultrahigh strength steels without hydrogen embrittlement.
On-site plating.
Reverse current applications (e.g., stain removal, deburring, etching, and dynamic balancing).
Specifications. Selective plating (electrodepositions), when properly applied, will meet the following specifications and standards.
QQ-C-320, Chromium Plating.
QQ-N-290, Nickel Plating.
QQ-P-416, Cadmium Plating.
QQ-S-365, Silver Plating.
QQ-Z-325, Zinc Plating.
MIL-T-10727, Tin Plating.
MIL-C-14550, Copper Plating.
MIL-G-45204, Gold Plating.
General Requirements.
Areas to be repaired by this process should be limited to small areas of large parts, particularly electrical or electronic parts.
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.
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 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, and too slow a motion causes burning. A dry tool results in burnt plate, coarse grain structure, and unsound deposits.
The tool cannot be too wet. Solution temperatures of 110 °F to 120 °F are reached during operation.
Par 4-62 Page 4-151 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
Par 4-62 Page 4-152 that have been previously used with reverse current (because of solution contamination).
Equipment. The power source should operate on either 110 or 220-volt alternating current (AC), 60 Hertz, single-phase input. It s hould have a capability to produce direct current (DC) 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.
The ammeter should provide a full-scale reading equal to the maximum capacity of the power source, and with an accuracy of ±5 percent of the current being measured.
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.
An ampere-hour meter should be readable to
0.001 ampere-hour and have an accuracy of ±0.01 ampere-hour.
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.
The containers for holding and catching runoff solutions should be designed to the proper configuration and be inert to the specific solution.
The mechanical cleaning equipment and materials should be designed and selected to prevent contamination of the parts to be cleaned.
Materials. The anodes should be of high-purity dense graphite or platinum-iridium alloys. Do not mix solutions from different suppliers. This could result in contamination.
Detail Requirements. On large parts, no area greater than approximately 10 percent of the total area of the part should be plated by this selective plating process.
Small parts may be partially or completely plated.
Special cases exceeding these limitations should be coordinated with the manufacturer of the plating equipment being used and their recommendations should be followed.
Anode Selection. As a general guide, the contact area of the anode should be approximately one-third the size of the area to be plated. When selecting the anode, the configuration of the part will dictate the shape of the anode.
Required Ampere-Hour Calculation. The selected plating solution has a factor which is equal to the ampere-hours required to deposit 0.0001 inch on 1 square inch of surface. Determine the thickness of plating desired on a certain area, and multiply the solution factor times the plating thickness times the area in square inches to determine the ampere-hours required. This factor may vary because of temperature, current density, etc.
Cleaning. Remove corrosion, scale, oxide, and unacceptable plating prior to processing. Use a suitable solvent or cleaner to remove grease or oil.
Plating on Aluminum and Aluminum Base Alloys.
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.
Par 4-62 Page 4-153 Rinse the area in cold, clean tap water.
Activate the area with reverse current, 7 to 10 volts, in conjunction with the proper activating solution until a uniform, gray-to-black surface is obtained.
Rinse thoroughly in cold, clean tap water.
Immediately electroplate to color while the area is still wet, using the appropriate nickel solution.
Rinse thoroughly.
Immediately continue plating with any other solution to desired thickness.
Rinse and dry.
Plating on Copper and Copper Base Alloys.
Electroclean the area using direct current until water does not break on the surface. The electroclean process should be accomplished at 8 to 12 volts using the appropriate electroclean solution.
Rinse the area in cold, clean tap water.
Immediately electroplate the area with any of the plating solutions, except silver. Silver requires an undercoat.
Rinse and dry.
Plating on 300 and 400 Series Stainless Steels, Nickel Base Alloys, Chrome Base Alloys, High Nickel Ferrous Alloys, Cobalt Base Alloys, Nickel Plate, and Chrome Plate.
Electroclean the area using direct current until water does not break on the surface.
This electroclean process should be accomplished at 12 to 20 volts using the appropriate electrocleaning solution.
Rinse the area in cold, clean tap water.
Activate the surface using direct current for 1 to 2 minutes, using the activating solution, and accomplish at 6 to 20 volts.
Do not rinse.
Immediately nickel-flash the surface to a thickness of 0.00005 to 0.0001 inch, using the appropriate nickel solution.
Rinse thoroughly.
Immediately continue plating with any other solution to desired thickness.
Rinse and dry.
Plating on Low-Carbon Steels (Heat Treated to 180,000 psi).
Electroclean the area using direct current until water does not break on the surface. This electroclean process should be accomplished at 12 to 20 volts, using the appropriate electrocleaning solution.
Rinse the area in cold, clean tap water.
Reverse-current etch at 8 to 10 volts, using the appropriate activating solution, until a uniform gray surface is obtained.
Rinse thoroughly.
Par 4-62 Page 4-154
Par 4-62 Page 4-155 (and 4-52) Immediately electroplate the part using any solutions, except copper or silver. Both of these require undercoats.
Rinse and dry.
Plating on Cast Iron and High-Carbon Steels (Steels Heat Treated to 180,000 psi).
Electroclean the area using direct current until water does not break on the surface. This electroclean process should be accomplished at 12 to 20 volts, using the appropriate electrocleaning solution.
Rinse the area thoroughly in cold, clean tap water.
Reverse-current etch at 8 to 10 volts, using the appropriate etching solution, until a uniform gray is obtained.
Rinse thoroughly.
Remove surface smut with 15 to 25 volts using the appropriate activating solution.
Rinse thoroughly.
Electroplate immediately, using any of the solutions, except copper or silver (both of these require undercoats).
Rinse and dry.
Plating on Ultrahigh Strength Steels (Heat Treated Above 180,000 psi).
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.
Rinse the area thoroughly in cold, clean tap water.
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.
Rinse and dry.
Bake the part for 4 hours at 375 °F ± 25 °F.
NOTE: Where the solution vendor provides substantiating data that hydrogen embrittlement will not result from plating with a particular solution, then a postbake is not required. This substantiating data can be in the form of aircraft industry manufacturer’s process specifications, military specifications, or other suitable data.
NOTE: Acid etching should be avoided, if possible. Where etching is absolutely necessary, it should always be done with reverse current. Use alkaline solutions for initial deposits.
Dissimilar Metals and Changing Base. As a general rule, when plating two dissimilar metals, follow the plating procedure for the one with the most steps or activation. If activating steps have to be mixed, use reverse-current activation step s prior to direct-current activation steps.
Plating Solution Selection.
Alkaline and neutral solutions are to be used on porous base metals, white metals, highstrength steel, and for improved coating