130° SLEEVE 12-112- 30° ==== 30
ROSETTE WELDS MAY - WELD
BE OMITTED WHEN SLEEVES FIT TIGHTLY.
- REPLACEMENT TUBE
ORIGINAL TUBE
FISH-MOUTH 1/2A- SLEEVE -1/2A ROSETTE WELDS MAY • WELD
BE OMITTED WHEN SLEEVES FIT TIGHTLY.
- REPLACEMENT TUBE
ORIGINAL TUBE FOUR ROSETTE •WELD HERE FIRST ORIGINAL TUBE WELDS • 0 114A 30 - 1/8" GAP
•1/2A FOR WELDING
- 1/2A - - 1/2A + 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.
FIGURE 4-38. Splicing by outer-sleeve method (replacement by welded outside sleeve).
Par 4-85 Page 4-172
< ORIGINAL TUBE
SLEEVE SLEEVE
TUBE TOBE ** 1/4B 1/4D 1/2B
ROSETTE ORIGINAL TUBE WELD _D WELD 1/4A LA -A~ 30° ORIGINAL TUBE 1/2A 1/2A SLEEVE ALLOW 1/8" GAP REPLACEMENT TUBE SLEEVE TUBE
TUBE BETWEEN SLEEVES FOR WELDING.
FIGURE 4-39. Tube replacement at a station by welded outer sleeves.
•2-1/2A - REPLACEMENT TUBE ORIGINAL → 1/2A TUBE 1-1/2A-
- REPLACEMENT TUBE 4-1/2A 30° →1/2A
ORIGINAL TUBE -1-1/2A→ FIGURE 4-40. Splicing using larger diameter replacement tube.
Par 4-86 Page 4-173
Par 4-87 Page 4-174 normal position, slip the replacement tube over the long stub, and then back over the short stub. Center the replacement tube between the st ubs 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.
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.
Tube of Larger Diameter Than Original. A tube (sleeve) of larger diameter th an the original is used in the method shown in figure 4-41 (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.
Tube of Same Diameter as Original. In the method shown in figure 4-41 (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.
Simple Sleeve. In figure 4-41 (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.
Large Difference in Longeron Diameter Each Side of Fitting. Figure 4-41 (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.
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.
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.
Grind out all cracked welds.
Use only high-grade metallurgically controlled (mc) welding rods for engine-mount repairs.
WELD SPACER APPROXIMATELY "A" LONG WELDED ON
INSIDE TUBE 5·= JAL 3A→ (A) (B) 30° GENERAL NOTE: -
ALL ROSETTE WELDS (C) TO BE & DIAMETER OF THE ORIGINAL TUBES.
30* GAP $"* (D) FIGURE 4-41. Repairs at built-in fuselage fittings.
Par 4-88 Page 4-175
Par 4-90 Page 4-176 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.
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.
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.
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 PMA for the part.
WING-BRACE STRUTS AND TAIL-BRACE STRUTS. In general, it will be found advantageous to replace damaged wing-brace struts made either from rounded or streamlined tubing with new members purchased from the original manufacturer. However, there is no objection, from an airworthiness point of view, to repairing such members in a proper manner.
An acceptable method of repair, if streamlined tubing is used, will be found in figure 4-43.
Repair similar members made of round tubes using a standard splice, as shown in figure 4-35, figure 4-37, or figure 4-38.
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 jurystrut 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 charact eristics of the strut and attaching components are not adversely affected by the repair. A wide range of speed and engine-power combination must be covered during this check.
Fit and Alignment. When making repairs to wing and tail surface brace members, pay particular attention to proper fit and alignment to avoid distortion.
LANDING GEAR REPAIR.
Round Tube Construction. Repair landing gears made of round tubing using standard repairs and splices as shown in figure 4-35 and figure 4-41.
Streamline Tube Construction. Repair landing gears made of streamlined tubing by either one of the methods shown in figure 4-42, figure 4-44, or figure 4-45.
Axle Assemblies. Representative types of repairable and nonrepairable landing gear axle assemblies are shown in figures 4-46 and 4-47. 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
Par 4-91 Page 4-177
A- Slot Width (Original Tube).
B- Outside Diameter (Insert Tube).
C- Streamline Tube Length of Major Axis.
S.L. Size A B C 6A 1” .380 .560 1.340 .496 1-¼ .380 .690 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 1.380 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 4-42. Streamline tube splice using round tube (applicable to landing gear).
shown in figure 4-35 through figure 4-45. However, it will always be necessary to ascertain whether or not the members are heat treated. The axle assembly as shown in figure 4-47 is, in general, of a nonrepairable type for the following reasons.
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 must be replaced if damaged.
The oleo portion of the structure is generally heat treated after welding, and is perfectly machined to ensure proper functioning of the shock absorber. These parts would be distorted by welding after machining.
REPAIRS TO WELDED ASSEMBLIES. These repairs may be made by the following methods.
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.
Par 4-93 Page 4-178
A- Minimum Length of Sleeve.
B- Streamline Tube Length of Minor Axis.
C- Streamline Tube Length of Major Axis.
S.L. Size A B C 1” .572 .82 1.340 1-¼ .714 .476 1.670 1-½ .858 .572 2.005 1-¾ 1.000 .667 2.339 2 1.144 .762 2.670 2-¼ 1.286 .858 3.008 2-½ 1.430 .954 3.342
FIGURE 4-43. Streamline tube splice using split sleeve (applicable to wing and tail surface brace struts and other members).
Replacing weld deposit by chipping out the metal deposited by the welding process and rewelding after properly reinforcing the joint by means of inserts or external gussets.
STAINLESS STEEL STRUCTURE. Repair structural components made from stainless steel, particularly the “18-8” variety (18 percent chromium, 8 percent nickel), joined by spot welding, in accordance with the instructions furnished by the manufacturer, DER, or FAA.
Substitution of bolted or riveted connections for spot-welded joints are to be specifically approved by a DER or the FAA.
Repair secondary structural and nonstructural elements such as tip bows or leading and trailing edge tip strips of wing and control surfaces by soldering with a 50-50 lead-tin solder or a 60- 40 lead-tin solder. 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 effective, remove excess flux by washing the joint. Due to the high-heat conductivity of the stainless steel, use a soldering iron large enough to do the work properly.
Par 4-93 Page 4-179 INSERT TUBE IS OF SAME STREAMLINE TUBING AS ORIGINAL.
A- Is ²/³ B.
B- Is Minor Axis Length of Original Streamline Tube.
C- Is Major Axis Length of Original Streamline Tube.
S.L. Size A B C 6A 1” .382 .572 1.340 5.160 1-¼ .476 .714 1.670 6.430 1-½ .572 .858 2.005 7.720 1-¾ .667 1.000 2.339 9.000 2 .763 1.144 2.670 10.300 2-¼ .858 1.286 3.008 11.580 2-½ .954 1.430 3.342 12.880
FIGURE 4-44. Streamline tube splice using split insert (applicable to landing gear).
Par 4-93 Page 4-180
A- Streamline Tube Length of Minor Axis, Plate Widths.
B- Distance of First Plate From Leading Edge, ²/³ A.
C- Streamline Tube Length of Major Axis.
S.L. Size A B C 6A 1” .572 .82 1.340 3.430 1-¼ .714 .476 1.670 4.280 1-½ .858 .572 2.005 5.150 1-¾ 1.000 .667 2.339 6.000 2 1.144 .762 2.670 6.860 2-¼ 1.286 .858 3.008 7.720 2-½ 1.430 .954 3.342 8.580
FIGURE 4-45. Streamline tube splice using plates (applicable to landing gear).
Par 4-93 Page 4-181
(A), (B), AND (C) ARE TYPES OF REPAIRABLE AXLE ASSEMBLIES. ASSEMBLIES ORIGINALLY HEAT TREATED MUST BE REHEAT TREATED AFTER WELDING.
F IGURE 4-46. Representative types of repairable axle assemblies.
Par 4-93 Page 4-182 (and 4-80)
Par 4-104 Page 4-183 FIGURE 4-47. Landing gear assemblies that CANNOT be repaired by welding.
4-94.4-103. [RESERVED.]