Par 4-90 Page 4-76 TABLE 4-15. CHART SHOWING WELDING FILLER ROD SELECTION Welding Rod # AMS Spec. AWS Spec. Welds These Metals 4130 AMS 6457 AWS A5.18 Mild steel, 4130 steel 4140 AMS 6452 AWS A5.28 4140 steel 4043 AMS 4190 AWS A5.10 Most weldable aluminum 308L AMS 5692 AWS A5.9 304 stainless steel 316L AMS 5692 AWS A5.9 316 stainless steel AZ61A AMS 4350 AWS A5.19 AZ61A magnesium ERTi-5 AMS 4954 AWS A5-16 Titanium
4-91. REPAIR OF TUBULAR MEMBERS.
a. Inspection. Prior to repairing tubular members, carefully examine the structure surrounding any visible damage to insure that no secondary damage remains undetected.
Secondary damage may be produced in some structure, remote from the location of the primary damage, by the transmission of the damaging load along the tube. Damage of this nature usually occurs where the most abrupt change in direction of load travel is experienced. If this damage remains undetected, subsequent normal loads may cause failure of the part.
b. 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.
c. 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 4-34.)
To prepare the patch plate, cut a section of steel sheet of the same material and thickness as the heaviest tube damaged. Trim the reinforcement plate so that the fingers extend over the tubes a minimum of 1.5 times the respective tube diameter. (See Figure 4-34.) Remove all the existing finish on the damaged cluster-joint area to be covered by the reinforcement plate. The reinforcement plate may be formed before any welding is attempted, or it may be cut and tack-welded to one or more of the tubes in the cluster joint, then heated and 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 cluster joint, weld all the plate edges to the cluster joint.
Par 4-91 Page 4-77 FIGURE 4-34. FINGER PATCH REPAIRS FOR MEMBERS DENTED AT A CLUSTER
d. Mem bers 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 inch) stop holes at the ends of the crack.
4-92. REPAIR BY WELDED SLEEVE. This repair is outlined in Figure 4-35. 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 the sleeve reinforcement at a 30-degree angle on both ends so that the minimum distance of the sleeve from the edge of the crack or dent is not less than 1-1/2 times the diameter of the damaged tube. Cut through the entire length of the reinforcement sleeve, and separate the half-sections of the sleeve. Clamp the two sleeve sections to the proper positions on the affected areas of the original tube. Weld the reinforcement sleeve along the length of the two sides, and weld both ends of the sleeve to the damaged tube. (See Figure 4-35.) The filling of dents or cracks with welding rod in lieu of reinforcing the member is not acceptable.
FIGURE 4-35. MEMBERS DENTED IN A BAY (REPAIRS BY WELDED SLEEVE)
DENTED OR BENT TUBE
CRACKED TUBE
REINFORCEMENT TUBE SPLIT NOTE:
LOCALLY DENTED OR
BENT MEMBERS SHOULD
FIRST BE REFORMED IN CLAMP.
REINFORCEMENT SLEEVE TO BE OF SAME
MATERIAL AND AT LEAST THE SAME GAUGE AS TUBE BEING REPAIRED.
1-1/2 A ‹WELD 11-1/2 A *
AS ALTERNATIVE TO SPLIT TUBE,
A TWO-PIECE REINFORCEMENT
SLEEVE MAY BE FORMED FROM STEEL SHEET OF THE SAME MATERIAL 300 AND AT LEAST THE SAME GAUGE AS 1A → • 1A ~ THE DAMAGED TUBE. USE FISHMOUTH 1-1/2AM •1-1/2A•
ENDS AND FOUR ROSETTE WELDS AS SHOWN.
Par 4-92 Page 4-78
Par 4-93 Page 4-79
4-93. 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 bolt holes, in this type of repair, may prove critical.
4-94. WELDED-PATCH REPAIR. Dents or holes in tubing may be repaired by using a patch of the same material, one gauge thicker. (See Figure 4-36.)
FIGURE 4-36. WELDED-PATCH REPAIR
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.
4-95. 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 is recommended; especially where a smooth tube surface is desired. (See Figure 4-37.)
a. 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 diagonal 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 inner-sleeve tube material snugly within the original tube, with a maximum diameter difference of 1/16 inch. From this inner-sleeve tube material cut two
Par 4-95 Page 4-80 sections of tubing, each of such a length that the ends of the inner sleeve will be a minimum distance of 1-1/2-tube diameters from the nearest end of the diagonal cut.
b. If the inner sleeve fits very tightly in the replacement tube, chill the sleeve with dry ice or cold water. If this is insufficient, polish down the diameter of the sleeve with emery cloth.
Tack the outer and inner replacement tubes using rosette welds. Weld the inner sleeve to the tube stubs through the 1/8-inch gap, forming a weld bead over the gap.
4-96. 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 outer-sleeve method is given in Figure 4-38 and Figure 4-39.
FIGURE 4-37. SPLICING BY INNER-SLEEVE METHOD ALLOW 1/8" GAP BETWEEN ORIGINAL AND ROSETTE WELD- REPLACEMENT TUBES FOR WELDING.
ORIGINAL TUBE 30 ISLEEVE TUBE INSIDE 1/4A -A- I1/2A
REPLACEMENT TUBE
ROSETTE WELD FOR WELDIN CAP 1/4A TUBE - /1/2A --1/2A Par 4-96 Page 4-81
FIGURE 4-38. SPLICING BY OUTER-SLEEVE METHOD (REPLACEMENT BY
WELDED OUTSIDE SLEEVE) 30° SLEEVE 30
ROSETTE WELDS MAY -- WELD
BE OMITTED WHEN SLEEVES FIT TIGHTLY.
- REPLAGEMENT TUBE
ORIGINAL TUBE , FISH-MOUTH 1/2A - SLEEVE 1/2A 1/4A
ROSETTE WELDS MAY AWELD
BE OMITTED WHEN SLEEVES FIT TIGHTLY.
- REPLACEMENT TUBE
ORIGINAL TUBE
FOUR ROSETTE WELD HERE FIRST ORIGINAL TUBE WELDS → 11/40 +1/244 30 • 1/8" GAP T1'½A-71/29 1½A → FOR WELDING ALTERNATIVE SPLIT SLEEVE SPLICE ~ IF OUTSIDE DIAMETER OF ORIGINAL TUBE IS LESS THAN 1 INCH, SPLIT SLEEVE MAY BE MADE FROM STEEL TUBE OR SHEET STEEL. USE SAME MATERIAL OF AT LEAST THE SAME GAUGE.
Par 4-96 Page 4-82
Par 4-96 Page 4-83 FIGURE 4-39. TUBE REPLACEMENT AT A STATION BY WELDED
OUTER SLEEVES
a.
Remove the damaged section of a tube utilizing a 90-degree 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 exceed 1/32 inch. The outer-sleeve tube material selected must be of the same material and at least the same wall thickness as the original tube.
The clearance between inside diameter of the sleeve and the outside diameter of the original tube may not exceed 1/16 inch.
b. From this outer-sleeve tube material, cut diagonally (or fishmouth) two sections of tubing, each of such length that the nearest end of the outer sleeve is a minimum distance of 1–1/2-tube diameters from the end of the cut on the original tube. Use a fishmouth sleeve wherever possible. Deburr the edges of the sleeves, replacement tube, and the original tube stubs.
c. Slip the two sleeves over the replacement tube, align the replacement tube with the original tube stubs, and slip the sleeves over the center of each joint. Adjust the sleeves to suit the area and provide maximum reinforcement.
d. 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 one sleeve weld to cool before welding the remaining tube to prevent undue warping.
4-97. SPLICING USING LARGER DIAMETER REPLACEMENT TUBES. The method of splicing structural tubes, as shown in Figure 4-40, requires the least amount of cutting and welding. However, this splicing method cannot be used where the damaged tube is cut too near the adjacent cluster joints, or where bracket-mounting provisions make it necessary to maintain
Par 4-97 Page 4-84 the same replacement tube diameter as the original. As an aid to installing the replacement tube, squarely cut the original damaged tube leaving a minimum short stub equal to 2-1/2-tube diameters on one end and a minimum long stub equal to 4-1/2-tube diameters on the other end.
Select a length of steel tube of the same material and at least the same wall thickness, having an inside diameter approximately equal to the outside diameter of the damaged tube. Fit this replacement tube material snugly around the original tube with a maximum diameter difference of 1/16 inch. From this replacement tube material, cut a section of tubing diagonally (or fishmouth) of such a length that each end of the tube is a minimum distance of 1-1/2-tube diameters from the end of the cut on the original tube. Use a fishmouth cut replacement tube wherever possible. Deburr the edges of the replacement tube and original tube stubs. If a fishmouth cut is used, file out the sharp radius of the cut with a small round file. Spring the long stub of the original tube from the normal position, slip the replacement tube over the long stub, and then back over the short stub. Center the replacement tube between the stubs of the original tube. Tack weld one end of the replacement tube in several places, then weld completely around the end. In order to prevent distortion, allow the weld to cool completely, then weld the remaining end of the replacement tube to the original tube.
FIGURE 4-40. SPLICING USING LARGER DIAMETER REPLACEMENT TUBE
4-98. REPAIRS AT BUILT-IN FUSELAGE FITTINGS. Make splices in accordance with the methods described in paragraphs 4-86 through 4-92. Repair built-in fuselage fittings in the manner shown in Figure 4-41. The following paragraphs outline the different methods as shown in Figure 4-41.
Par 4-98 Page 4-85 FIGURE 4-41. REPAIRS AT BUILT-IN FUSELAGE FITTINGS
a.
Tube of Larger Diameter Than Original. A tube (sleeve) of larger diameter than the original is used in the method shown in Figure 4-41, image (A). The forward splice is a 30-degree scarf splice. Cut the rear longeron (right) approximately 4 inches from the centerline of the joint and fit a 1 inch long spacer over the longeron, and edge weld this spacer and longeron. Make a tapered “V” cut approximately 2 inches long in the aft end of the outer sleeve, and swage the end of the outer sleeve to fit the longeron and weld.
b. Tube of Same Diameter as Original. In the method shown in Figure 4-41, image (B), the new section is the same size as the longeron forward (left) of the fitting. The rear end (right) of the tube is cut at 30 degrees and forms the outside sleeve of the scarf splice. A sleeve is centered over the forward joint as indicated.
c. Simple Sleeve. In Figure 4-41, image (C), it is assumed the longeron is the same size on each side of the fitting. It is repaired by a sleeve of larger diameter than the longeron.
Par 4-98 Page 4-86
d. Large Difference in Longeron Diameter Each Side of Fitting. Figure 4-41, image (D) assumes that there is 1/4-inch difference in the diameter of the longeron on the two sides of the fitting. The section of longeron forward (left) of the fitting is cut at 30 degrees, and a section of tubing of the same size as the tube and of such length as to extend well to the rear (right) of the fitting is slipped through it. One end is cut at 30 degrees to fit the 30-degree scarf at left, and the other end fishmouthed. This makes it possible to insert a tube of proper diameter to form an inside sleeve for the tube on the left of the fitting and an outside sleeve for the tube on the right of the fitting.
4-99. ENGINE-MOUNT REPAIRS. All welding on an engine mount must be of the highest quality, since vibration tends to accentuate any minor defect. Engine-mount members should preferably be repaired by using a larger diameter replacement tube, telescoped over the stub of the original member, and using fishmouth and rosette welds. However, 30-degree scarf welds in place of the fishmouth welds will be considered acceptable for engine-mount repair work.
a. Repaired engine mounts must be checked for accurate alignment. When tubes are used to replace bent or damaged ones, the original alignment of the structure must be maintained.
When drawings are not available, this can be done by measuring the distance between points of corresponding members that have not been distorted.
b. Grind out all cracked welds.
c. Use only high-grade metallurgically controlled (mc) welding rods for engine-mount repairs.
d. If all members are out of alignment, reject the engine mount and replace with one supplied by the manufacturer or one which was built to conform to the manufacturer’s drawings.
The method of checking the alignment of the fuselage or nacelle points should be requested from the manufacturer.
e. Repair minor damage, such as a crack adjacent to an engine-attachment lug, by rewelding the ring and extending a gusset or a mounting lug past the damaged area.
Engine-mount rings which are extensively damaged must not be repaired, unless the method of repair is specifically approved by the FAA, or the repair is accomplished in accordance with FAA-approved instructions.
f. If the manufacturer stress relieved the engine mount after welding it, the engine mount should be re-stress relieved after the weld repairs are made.
4-100. BUILT-UP TUBULAR WING OR TAIL-SPARS. Repair built-up tubular wing or tail-spars by using any of the applicable splices and methods of repair shown in Figure 4-35 through Figure 4-45, provided the spars are not heat treated. In the case of heat-treated spars, the entire spar assembly would have to be reheat treated to the manufacturer’s specifications after completion of the repair. In general, this will be found less practicable than replacing the spar with one furnished by the manufacturer or holder of the Parts Manufacturer Approval (PMA) for the part.
FIGURE 4-42. STREAMLINE TUBE SPLICE USING ROUND TUBE (APPLICABLE
TO LANDING GEAR) , GAP E WELD,
FORM INSIDE AT LEAST AT LEAST TUBE TO FIT. • 30.
A- Slot Width (Original Tube).
B- Outside Diameter (Insert Tube).
C- Streamline Tube Length of Major Axis.
S.L. Size A B D 1" 375 563 1.340 .496 1-¼ .375 -688 1.670 .619 1-½ .500 .875 2.005 .743 1-¾ .500 1.000 2.339 .867 2 .500 1.125 2.670 991 2-¼ .500 1.250 3.008 1.115 2-½ _500 1.375 3.342 1.239
ROUND INSERT TUBE (B) SHOULD BE AT LEAST OF SAME MATERIAL AND ONE GAUGE THICKER THAN ORIGINAL STREAMLINE TUBE (C).
Par 4-100 Page 4-87