AC 43.13-1A 1972 formed around the joint to produce a smooth contour. Apply sufficient heat to the plate while forming so that there is generally a gap of no more than 1/16 inch from the contour of the joint to the plate. In this operation avoid unnecessary heating, and exercise care to prevent damage at the point of the angle formed by any two adjacent fingers of the plate. After the plate is formed and tack-welded to the clusterjoint, weld all the plate edges to the clusterjoint.
d. Members Dented in a Bay. Repair dented, bent, cracked, or otherwise damaged tubular members by using a split-sleeve reinforcement;
carefully straighten the damaged member; and in the case of cracks, drill No. 40 (0.098) stopholes at the ends of the crack.
71. REPAIR BY WELDED SLEEVE. This repair is outlined in figure 2.5. Select a length of steel tube sleeve having an inside diameter approximately equal to the outside diameter of the damaged tube and of the same material, and at least the same wall thickness. Diagonally cut Ithe sleeve reinforcement at a 30° angle on both ends so that the minimum distance of the sleeve from the edge of the crack or dent is not less than 11/2 times the diameter of the damaged tube. Cut through the entire length of the reinforcement sleeve, and separate the halfections of the sleeve. Clamp the two sleeve sections to the proper positions on the affected reas of the original tube. Weld the reinforce- Page 35 ment sleeve along the length of the two sides, and weld both ends of the sleeve to the damaged tube as shown in the figure. The filling of dents or cracks with welding rod in lieu of reinforcing the member is not acceptable.
72. REPAIR BY BOLTED SLEEVE, Do not use bolted sleeve repairs on welded steel tube structure unless specifically authorized by the manufacturer or the FAA. The tube area removed by the boltholes in this types of repair may prove critical.
73. WELDED-PATCH REPAIR. Dents or holes in tubing may be repaired by a welded patch of the same material and one gauge thicker, as shown in figure 2.6 provided:
a. Dented Tubing.
(1) Dents are not deeper than 1/10 of tube diameter, do not involve more than 1/4 of the tube circumference, and are not longer than tube diameter.
(2) Dents are free from cracks, abrasions, and sharp corners.
(3) The dented tubing can be substantially reformed without cracking before application of the patch.
b. Punctured Tubing. Holes are not longer than tube diameter and involve not more than 1/4 of tube circumference.
* TUBE CIRCUM. -NOT GREATER THAN "A" (MAX.)
• 2A -
- DAMAGE FIGURE 2.6.-Welded patch repair.
Chap 2 Far 70
AC 43.13-14 1971 ALLOW 1/8" GAP BETWEEN ORIGINAL AND ROSETTE WELD REPLAGEMENT TUBES FOR WELDING.
INSIDE
ORIGINAL TUBE ISLEEVE TUBE
- UZA
REPLACEMENT TUBE
ROSETTE WELD FORVIPELVISAP
INSIDE SLEEVE TUBE
ORIGINAL TUBE FIGURE 2.7.-Splicing by inner sleeve method.
74. SPLICING TUBING BY INNER SLEEVE METHOD.
If the damage to a structural tube is such that a partial replacement of the tube is necessary, the inner sleeve splice shown in figure 2.7 is recommended, especially where a smooth tube surface is desired. 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, to match the length of the removed portion of the damaged tube. At each end of the replacement tube allow a 1/8-inch gap from the diago- Par 74 nal cuts to the stubs of the original tube. Select a length of steel tubing of the same material, and at least the same wall thickness, and of an outside diameter, equal to the inside diameter of the damaged tube. Fit this innersleeve tube material snugly within the original tube, wit a maximum diameter difference of 1/16 inc From this inner-sleeve tube material cut 2 se tions of tubing, each of such a length that th ends of the inner sleeve will be a minimum dis tance of 1 1/2-tube diameters from the neares end of the diagonal cut.
If the inner sleeve fits very tightly in the replacement tube, chill the sleeve with dry ice or Chap 3
I€ 43.13-1A Page 37 972 ,30° SLEEVE
ROSETTE WELDS MAY - WELD
BE OMITTED WHEN SLEEVES FIT TIGHTLY.
- REPLAGEMENT TUBE
ORIGINAL TUBE
FISH-MOUTH SLEEVE
- UZA
ROSETTE WELDS MAY WELD
BE OMITTED WHEN SLEEVES FIT TIGHTLY.
LREPLACEMENT TUBE
ORIGINAL TUBE
FOUR ROSETTE - WELD HERE FIRST WELDS
ORIGINAL TUBE -1/8" GAP
FOR WELDING ALTERNATIVE SPLIT SLEEVE SPLICE ~
IF OUTSIDE DIAMETER OF ORIGINAL TUBE IS LESS THAN I INCH, SPLIT SLEEVE MAY BE MADE FROM STEEL TUBE OR SHEET STEEL. USE SAME
MATERIAL OF AT LEAST THE SAME GAUGE, FOR ORIGINAL TUBE DIAMETERS OF 1 INCH AND OVER, USE SHEET STEEL ONLY.
FIGURE 2.8.-Splicing by outer sleeve method-replacement by welded outside sleeve.
Par 74
in cold water. If this is insufficient, polish down the diameter of the sleeve with emery cloth. Weld the inner sleeve to the tube stubs through the 1/8-inch gap, forming a weld bead over the gap.
75. SPLICING TUBING BY OUTER SLEEVE METHOD.
If partial replacement of a tube is necessary, make the outer sleeve splice using a replacement tube of the same diameter. Since the outer sleeve splice requires the greatest amount of welding, it should be used only when the other splicing methods are not suitable. Information on the replacement by use of the welded outside sleeve method is given in figures 2.8 and 2.9.
Remove the damaged section of a tube utilizing a 90° cut. Cut a replacement steel tube of the same material, diameter, and at least the same wall thickness to match the length of the removed portion of the damaged tube. This replacement tube must bear against the stubs of the original tube with a total tolerance not to AC 43.13- 19 exceed 1/82 inch. The outer sleeve tube mat rial selected must be of the same material an at least the same wall thickness as the origin tube. The clearance between inside diameter c the sleeve and the outside diameter of the orig inal tube may not exceed 1/16 inch. From thi outer sleeve tube material, cut diagonally (o fishmouth) 2 sections of tubing, each of suc length that the nearest end of the outer sleev is a minimum distance of 1 1/2-tube diameter from the end of the cut on the original tube Use a fishmouth sleeve wherever possible. Re move the burr from the edges of the sleeves replacement tube, and the original tube stubs Slip the two sleeves over the replacement tube aline the replacement tube with the origina tube stubs, and slip the sleeves out over thi center of each joint. Adjust the sleeves to sui the area and to provide maximum reinforce ment. Tackweld the two sleeves to the replace ment tube in two places before welding. Apply a uniform weld around both ends of one of the reinforcement sleeves and allow the weld t cool; then, weld around both ends of the r < ORIGINAL TUBE
SLEEVE SLEEVE
TUBE TUBE
ROSETTE ORIGINAL TUBE WELD WELD ORIGINAL TUBE 1/2 A SLEEVE Ve" GAF ALLOW REPLACEMENT TUBE SLEEVE TUBE
TUBE BETWEEN SLEEVES
FOR WELDING, FIGURE 2.9.-Tube replacement at a station by welded outer sleeves.
Far 74
АС 43.73-1А Page 41 1972
WELD SPACER APPROXIMATELY "A" LONG WELDED ON
INSIDE TUBE
•ЗА~ (А) (B) GENERAL NOTE:-
ALL ROSETTE WELDS (C) TO BE & DIAMETER OF THE ORIGINAL TUBES.
GAP 1" (D) FIGURE 2.11.-Repairs at built-in fuselage fittings.
Par 79
Page 42 АС 43.13-1А 1972 GAP I" 30 WELD mh ABC
FORM INSIDE TUBE TO FIT. AT LEAST - 3C - AT LEAST
A - SLOT WIDTH (ORIGINAL TUBE) 8 - OUTSIDE DIAMETER (INSERT TUBE)
C - STREAMLINE TUBE LENGTH OF MAJOR AXIS S.L. SIZE D 9/16 1.340" • 496" 1- 4 11/16 1.670 • 619 1-2 2.005 . 743 1- 4 2.339 .867 2 2,670 991 2-¼ 3.008 1.115 г- ½ ı- ₴ 3.342 1.239
ROUND INSERT TUBE (B) SHOULD BE AT LEAST OF SAME
MATERIAL AND ONE GAUGE THICKER THAN ORIGINAL STREAMLINE TUBE (C).
FIGURE 2.12.-Streamline tube splice using round tube (applicable to landing gears).
Par 79
1972 AC 43.13-TA
OPEN OUT OPEN OUT TO FIT ORIGIN ORIGINAL TUBE AND WELD.
OUTSIDE SLEEVE MAY BE OF SAME SL. TUBING AS ORIGINAL OR USE AT LEAST S.L. TUBING OF AT LEAST THE C- SAME GAUGE.
AT LEAST WELD
A - MINIMUM LENGTH OF SLEEVE 9- STREAMLINE TUBE LENGTH OF MINOR AXIS
- STREAMLINE TUBE LENGTH Of MAJOR AXIS S. L. SIZE
7.324" .572" 1.340" 1-¼ 9.128 .714 1.670 1-½ 10.960 .858 2.005 1- ¾ 12.784 1.000 2.339 2 14.594 1.144 2.670 2-4% 16.442 1.286 3.008 2 - ½ 18.268 1.430 3.342 FIGURE 2.13.—Streamline tube splice using split aleeve (applicable to wing and tail surface brace struts and other members).
Page 44 AC 43.13-1A 1972 *B-* WELD GAP $" SIZE OF ROSETTES = 14G. DRILL OUTSIDE
TUBES ONLY B C
SEA-SEE * B- -2A-→ IŁA L = MAXIMUM INSERT LENGTH SAW .08 C OFF OF T.E. AND WELD INSERT TUBE IS OF SAME STREAMLINE TUBING AS ORIGINAL.
A IS E B 8 IS MINOR AXIS LENGTH OF ORIGINAL STREAMLINE TUBE
C IS MAJOR AXIS LENGTH OF ORIGINAL STREAMLINE TUBE S. L. SIZE .382 _ 572 1.340 5.16 1¼ ,476 • 714 1.670 6.43 1/½ . 572 1858 2.005 7.72 1 ¾ .667 1.000 2.339 9.00 2 .763 1.144 2.670 10.30 2 '¼ .858 I.286 3.008 11.58 2 V/½ ,954 1.430 3.342 12.88 FIGURE 2.14.-Streamline tube splice using split insert (applicable to landing gears).
Par 79
kc 43.13-14 1972
c. Axle Assemblies. Representative types of repairable and nonrepairable landing gear axle assemblies are shown in figure 2.16. The types as shown in A, B, and C of this figure are formed from steel tubing and may be repaired by the applicable method shown in figures 2.5 thru 2.15 in this Advisory Circular. However, it will always be necessary to ascertain whether or not the members are heat treated.
The axle assembly as shown in figure
2.16(D) is, in general, of a nonrepairable type for the following reasons:
(1) The axle stub is usually made from a highly heat-treated nickel alloy steel and carefully machined to close tolerances. These stubs are usually replaceable and should be replaced if damaged.
(2) The oleo portion of the structure is generally heat-treated after welding and is perfectly machined to assure proper functioning of the shock absorber. These parts would be istorted by welding after machining.
J. BUILT-UP TUBULAR WING OR TAIL SURFACE ARS. Repair built-up tubular wing or tail surce spars by using any of the applicable plices and methods of repair shown in figures 5 through 2.15 provided the spars are not eat-treated. In the case of heat-treated spars, he entire spar assembly would have to be reeat-treated to the manufacturer's specificaons after completion of the repair. In genal, this will be found less practicable than placing the spar with one furnished by the anufacturer.
WING AND TAIL BRACE STRUTS. In general, 'ill be found advantageous to replace damwing-brace struts made either from ded or streamlined tubing with new mempurchased from the original manufac- However, there is no objection from an rthiness point of view to repairing such ers in a proper manner. An acceptable d, in case streamlined tubing is used, will nd in figure 2.18. Repair similar memnade of round tubes using a standard as shown in figures 2.5, 2.7, or 2.8.
a. Location of Splices. Steel brace struts may be spliced at any point along the length of the strut, provided the splice does not overlap part of an end fitting. The jury strut attachment is not considered an end fitting; therefore, a splice may be made at this point. The repair procedure and workmanship should be such as to minimize distortion due to welding and the necessity for subsequent straightening operations. Observe every repaired strut carefully during initial flights to ascertain that the vibration characteristics of the strut and attaching components are not adversely affected by the repair. A wide range of speed and enginepower combination must be covered during this check.
(1) Fit and Alignment. When making repairs to wing and tail surface brace members, pay particular attention to proper fit and alinement to avoid distortion.
82, REPAIRS TO WELDED PARTS. Repairs to welded assemblies may be made by:
a. Repiacing welded joints-cutting out the welded joint and replacing it with one properly gusseted, or
b. Replacing weld deposit-chipping out the metal deposited by the weld process and rewelding after properly reinforcing the joint by means of inserts or external gussets.
83. STAINLESS STEEL STRUCTURE. Repair structural components made from stainless steel, particularly the "18-8" variety (18 percent chromiun, 8 percent nickel), joined by spot welding in accordance with the instructions furnished by the manufacturer. Substitution of bolted or riveted connections for spot-welded joints are to be specifically approved by an authorized representative of the FAA.
a. Secondary Structural and Nonstructural Elements. Repair such elements as tip-bows or leading and trailing edge tip-strips of wing-andcontrol surfaces by soldering with a 50-50 lead-tin solder or a 60-40 alloy of these metals.
For best results use a flux of phosphoric acid (syrup). Since the purpose of flux is to attack the metal so that the soldering will be effec- Par 79
Page 48 AC 43.13-:
19:
tive, remove excess flux by washing the joint. welded seams in boat hulls, fuel tanks, etc., in Due to the high-heat conductivity of the stain- similar manner.
less steel, use a soldering iron large enough to do the work properly. Repair leaky spot- 84.~94. RESERVED.
Par 83
lAC 43.13-1A Page 49 1972 Section 3. METAL REPAIR PROCEDURES
95. RIVETED OR BOLTED STEEL TRUSS-TYPE STRUC- TURES. Repairs to riveted or bolted steel trusstype structures should be made, employing the general principles outlined in the following paragraphs on aluminum alloy structures.
Methods for repair of vital members should be specifically approved by a representative of the Federal Aviation Administration.
96. ALUMINUM ALLOY STRUCTURES. Extensive repairs to damaged stressed skin on monocoque types of aluminum alloy structures should preferably be made in accordance with specific recommendations of the manufacturer of the aircraft. In many cases, repair parts, joints, or reinforcements can be designed, and proof of adequate strength shown, without the calculaion of the design loads and stresses, by properly considering the material and dimensions f the original parts and the riveted attachments. Examples illustrating the principles of this method as applied to typical repairs are given in this handbook, or may be found in extbooks on metal structures. An important point to bear in mind in making repairs on nonocoque structures is that a repaired part must be as strong as the original with respect to all types of loads and general rigidity.
a. Use of Annealed Alloys for Structural Parts.
he use of annealed 2017 or 2024 for any ructural repair of an aircraft is not consided satisfactory because of its poor corrosionisting properties.
Hygroscopic Materials Improperly Moisturefed. The use of hygroscopic materials imberly moisture-proofed, such as impregd fabrics, or leather, and the like, to effect r-tight joints and seams is not an acceptacactice.
rilling Oversized Holes. Avoid drilling zed holes or otherwise decreasing the effective tensile areas of wing-spar capstrips, wing, fuselage, or fin longitudinal stringers, or other highly stressed tensile members. Make all repairs or reinforcements to such members in accordance with factory recommendations or with the specific approval or a representative of the Federal Aviation Administration.
d. Disassembly Prior to Repairing. If the parts to be removed are essential to the rigidity of the complete structure, support the remaining structure prior to disassembly in such a manner as to prevent distortion and permanent damage to the remainder of the structure.
When rivets are to be removed, weaken the rivet head by drilling. Use a drill of the same size as the rivet. Drilling must be exact center and to the base of the head only. After drilling, break off the head with a pin punch and carefully drive out the shank. Removal of rivet heads with a cold chisel and hammer is not recommended because skin damage and distorted rivet holes will probably result. Care must also be taken whenever screws must be removed for disassembly or removal of stress plates, access plates, fillets, etc., to avoid damage to adjoining structure. When properly used, impact wrenches can be effective tools for removal of screws; however, damage to adjoining structure may result from excessive vertical loads being applied through the screw axis.
Excessive loads are usually related to improperly adjusted impact tools or attempting to remove screws that have seized from corrosion.
Remove seized screw by drilling and use of a screw extractor. Structural cracks may appear in the doubler or tang that runs parallel to the line of anchor or plate nuts installed for securing access doors or plates. Inspect rivet joints adjacent to damaged structure for partial failure (slippage) by removing one or more rivets to see if holes are elongated or the rivets have started to shear.
Por 95
97. SELECTION OF ALUMINUM FOR REPLACEMENT PARTS. In selecting the alloy, it is usually satisfactory to use 2024 in place of 2017 since the former is stronger. Hence, it will not be permissible to replace 2024 by 2017 unless the deficiency in strength of the latter material is compensated by an increase in material thickness, or the structural strength is substantiated by tests or analysis. Information on the comparative strength properties of these alloys, as well as 2014, 6061, 7075, etc., is contained in MIL-HDBK-5, Metallic Materials and Elements for Flight Vehicle Structure.
The choice of temper depends upon the severity of the subsequent forming operations. Parts having single curvature and straight bend lines with a large bend radius may be advantageously formed from heat-treated material, while a part, such as a fuselage frame, would АС 43.13-11 197:
have to be formed from soft, annealed sheet and heat-treated after forming. Make sure sheet metal parts which are to be left unpainted are made of clad (aluminum coated) material. Make sure all sheet material and finished parts are free from cracks, scratches, kinks, tool marks, corrosion pits, and other defects which may be factors in subsequent failure.
a. Forming Sheet Metal Parts. Bend lines should preferably be made to lie at an angle to the grain of the metal (preferably 90°). Before bending, smooth all rough edges, remove burrs, and drill relief holes at the ends of bend bure, and lines and at corners, to prevent cracks from starting. For material in the heat-treated condition, the bend radius should be large. (See figure 2.17 for recommended bend radii.)
FIGURE 2.17.-Recommended radii for 90° bends in aluminum alloys.
Approximate sheet thickness (t) (inch) Alloy and temper
0.016 0.082 0.064 0.128 0.182 0.268 2024-01 0-1t O-1t 0-1t 0-1t 2024-T8** 133t-St 2t 4t 8t-5t 4t-6t 4t-8t 2024-T6' 2t 4t 8t-5t 3t-5t 4t-6t 5t-7t 5052-0 O-It 0-1t O-It 5052-H82 ½t-It ½ t-1½t est-1%t 5052-H84 3st-1½t 1½t-2½t 1½t-2½t 5052-H86 0-1t % t-1½t 1t-2t 1½t-St 2t-4t 5052-F88 36t-1t It-2t 1½t-3t 2t-1t 8₺-бt 6061-0 0-1t O-1t 0-1t O-1t 6061-T4 0-It 0-1t 1t-2t 1½t-St 6061-T6 0-1t ½t-1%t 1t-2t 1½t-St 2t-4t 7075-0 0-It 0-1t ½t-1½t 1t-21 7075-T6' 2t-4t 3t-5t 4t-6t St-7t ' Alclad sheet may be bent over slight smaller radif than the corresponding tempers of uncoated alloy.
' Immediately after quenching, this alloy may be formed over appreciably smaller radi..
98. HEAT TREATMENT OF ALUMINUM ALLOY PARTS. All structural aluminum alloy parts are to be heat-treated in accordance with the heattreatment instructions issued by the manufacturers of the materials. If the heat-treatment produces warping, straighten the parts immediately after quenching. Heat-treat riveted parts before riveting, to preclude warping and corrosion. When riveted assemblies are heated in a salt bath, the salt cannot be entirely Par 97 washed out of the crevices, thus causing cor sion.
a. Quenching in Hot Water or Air. Quench terial from the solution heat-treating temp ture as rapidly as possible, with a minir delay after removal from the furnace. Que ing in cold water is preferred, although drastic chilling (hot or boiling water blast) is sometimes employed for bulk