Par 4-57 Page 4-28 The rough end of the retained stem in the center on the manufactured head must never be filed smooth, because it will weaken the strength of the lockring and the center stem could fall out.
(See Figure 4-8.)
FIGURE 4-8. MECHANICAL-LOCK (BULBED CHERRYLOCK) CHERRY RIVET STEM
STEM IS PULLED
INTO RIVET SLEEVE
LOCKING BEFORE AND STARTS TO FORM
COLLAR PULLING BULB BLIND HEAD BEGINS RIVET
- HEAD SHEET
GAP ) CLAMP-UP AND
HOLE FILL
ACTION BEGIN SHEAR RING
FORMATION OF BLIND
CLAMP-UP COMPLETED HEAD AND HOLE FILLING
AS STEM CONTINUES TO ARE COMPLETED
BULB OUT BLIND HEAD
SHEAR RING NOW SHEARS
FROM STEM CONE TO ALLOW
STEM TO PULL FURTHER INTO
RIVET HEAD RIVET
FIRMLY SEATED
BLIND SIDE BULB HEAD
IS FORMED BELOW SHEAR RING GUARANTEES
MINIMUM GRIP BLIND SIDE BULBED HEAD (IN MINIMUM GRIP SHEAR
RING MAY NOT SHEAR)
SHEAR RING HAS MOVED
DOWN STEM CONE UNTIL
PULLING HEAD AUTOMATICALLY STOPS STEM BREAK NOTCH COMPLETELY INSTALLED BULBED CHERRYLOCK
FLUSH WITH TOP OF
RIVET HEAD
PULLING HEAD HAS
LOCKING COLLAR IS NOW INSERTED LOCKING
READY TO BE INSERTED COLLAR AND STEM
HAS FRACTURED FLUSH
WITH RIVET HEAD (MAXIMUM GRIP
ILLUSTRATED)
BLIND SIDE
BULBED HEAD Par 4-57 Page 4-29
Par 4-57 Page 4-30
(b) The Bulbed CherryLOCK rivets are available in two head styles: universal and 100-degree countersunk. Their lengths are measured in increments of 1/16 inch. It is important to select a rivet with a length related to the grip length of the metal being joined.
(c) The Bulbed CherryLOCK rivet can be installed using a G30 Cherry Rivet Hand Puller or a pneumatic Bulbed CherryLOCK pulling tool.
(4) The CherryMAX rivet (see Figure 4-9) uses one tool to install three standard rivet diameters and their oversize counterparts. This makes the use of CherryMAX rivets very popular with many small general aviation repair shops. CherryMAX rivets are available in four nominal diameters: 1/8, 5/32, 3/16, and 1/4 inch; and three oversized diameters. CherryMAX rivets are manufactured with two head styles: universal and countersunk. The CherryMAX rivets consists of five parts: bulbed blind header, hollow rivet shell, locking (foil) collar, driving anvil, and pulling stem. The blind bulbed header takes up the extended shank and forms the bucktail on a CherryMAX rivet stem. Rivet sleeves are made from 5056 aluminum, Monel, and INCONEL 600. The stems are made from alloy steel, corrosion resistant steel (CRES), and INCONEL X-750 stem. CherryMAX rivets have an ultimate shear strength ranging from 50 thousands of pounds per square inch (KSI) to 75 KSI.
FIGURE 4-9. CHERRYMAX RIVET (
5) An Olympic-Lok rivet (see Figure 4-10) is a light three-piece mechanically locked, spindle-type blind rivet. It carries its stem lock integral to the manufactured head. While installing, the lockring is pressed into a groove on the pulling stem just as the rivet completes drawing the metal together. After installation is completed, never file the stem of an Olympic-Lok rivet, because it will weaken the lockring attachment. The Olympic-Lok fastener is available in three head styles: universal protruding, 100-degree flush countersink, and 100-degree flush shear; and three diameters: 1/8, 5/32, and 3/16 inch. The three diameters are available in eight different alloy combinations of 2017-T4, A-286, 5056, and Monel.
Olympic-Lok lock spindles are made from the same material as the sleeves.
FIGURE 4-10. OLYMPIC-LOK RIVET
SLEEVE REDUCED INTERNAL DIAMETER TO DOUBLE
PRECISELY ALIGN THE LOCKING GROOVE TAPER DESIGN
FULLY SERRATED STEM CONTINUOUS INTEGRAL
FOR INCREMENTAL PULL-UP LOCKING COLLAR RV 1201 SERIES
COUNTERSUNK
HEAD STYLE 1/16 INCH GRIP VARIATION CAPABILITY
DESIGNED INTO FASTENER
LARGER SECOND SHANK RV 1200 SERIES FLUSH BREAKING STEM DIAMETER FOR EXTRA
PROTRUDING SLEEVE EXPANSION AND
HEAD STYLE GREAT BLIND-SIDE
BEARING AREA
GREATER LOCKING COLLAR VOLUME PROTRUDING HEAD
DRIVEN INTO LOCKING GROOVE UNDERCUT ELIMINATES
DEBURRING When the stem travel is Continued pulling breaks Olympic-Lok blind rivet is Tool jaws grip the stem and stopped by the sleeve's inter- the stem flush to the fasteninserted into a prepared pull it into the sleeve, closing nal step, the integral locking er head. Flushness is hole. Note the clearance the sheet gap, expanding the collar shears free and is assured by the positioning between the rivet and the sleeve to fill the hole, and forced into the stem locking of the break-groove when sides of the hole and the forming a consistently larger groove. This forms a stem travel is stopped by gap between the sheets. blind side bearing area. permanent mechanical lock. the sleeve's internal step.
(6) Huck rivets (see Figure 4-11) are available in two head styles: protruding and flush.
They are available in four diameters: 1/8, 5/32, 3/16, and 1/4 inch. Their diameters are measured in increments of 1/32 inch and lengths are measured in 1/16 inch increments. They are manufactured in three different combinations of alloys: 5056 aluminum sleeve with 2024 aluminum alloy pin, A-286 corrosion-resistant steel sleeve with an A-286 pin, and a Monel 400 sleeve with an A-286 pin. The Huck fastener has the ability to tightly draw up two or more sheets of metal together while being installed. After the take up of the Huck fastener is completed, the lockring is squeezed into a groove on the pulling stem. The anvil or footer (of the installation tool) packs the ring into the groove of the pulling stem by bearing against the lockring.
Par 4-57 Page 4-31
Par 4-57 Page 4-32 FIGURE 4-11. HUCK RIVET (
7) Common pull-type POP rivets, produced for nonaircraft related applications, are not approved for use on certificated aircraft structures or components.
g. Design a new or revised rivet pattern for strength required in accordance with one of the following:
(1) The aircraft manufacturer’s maintenance manuals.
(2) The techniques found in structural textbooks and using the mechanical properties found in MIL-HDBK-5 or MMPDS-10.
(3) The specific instructions in subparagraphs 4-58g through 4-58n. When following the instructions in subparagraphs 4-58g through 4-58n, the general rule for the diameter of the rivets used to join aluminum sheets is to use a diameter approximately three times the thickness
Par 4-57 Page 4-33 of the thicker sheet. Do not use rivets where they would be placed in tension, tending to pull the heads off; and backup a lap joint of thin sheets with a stiffener section.
4-58. REPAIR METHODS AND PRECAUTIONS FOR ALUMINUM STRUCTURE.
Carefully examine all adjacent rivets outside of the repair area to ascertain that they have not been harmed by operations in adjacent areas. Drill rivet holes round, straight, and free from cracks. Deburr the hole with an oversize drill or deburring tool. The rivet set used in driving the rivets must be cupped slightly flatter than the rivet head. (See Figure 4-6.) Rivets are to be driven straight and tight, but not overdriven or driven while too hard, since the finished rivet must be free from cracks. Information on special methods of riveting, such as flush riveting, usually may be obtained from manufacturer’s service manuals.
a. Splicing of Tubes. Round or streamline aluminum alloy tubular members may be repaired by splicing. (See Figure 4-12.) Splices in struts that overlap fittings are not acceptable.
When solid rivets go completely through hollow tubes, their diameter must be at least one-eighth of the outside diameter of the outer tube. Rivets which are loaded in shear should be hammered only enough to form a small head and no attempt made to form the standard roundhead. The amount of hammering required to form the standard roundhead often causes the rivet to buckle inside the tube. (Correct and incorrect examples of this type of rivet application are incorporated in Figure 4-12.)
FIGURE 4-12. TYPICAL REPAIR METHOD FOR TUBULAR MEMBERS OF
ALUMINUM ALLOY L = 20 SPACES 3 d EACH TOTAL NO. OF RIVETS - 18 (9 EACH SIDE OF SPLICE) B+ -C A = ORIGINAL TUBE C = REPLACEMENT TUBE B = SLEEVE USE 2117-T "45" ALUM. ALLOY RIVETS SMALL HEAD
HAMMER STANDARD SPLICES MAY BE USED ON LIGHTLY- 2dl ROUND HEAD LONGERONS OR WEB MEMBERS.
CORRECT WAY INCORRECT WAY d MUST NOT BE LESS THAN D/8.
R = 3 d 00 1000
STREAMLINE M/3 EACH- (USE BASIC ROUND SIZES IN TABLE FOR SIZE OF RIVETS ETC.)
A, C* 3/4 7/8 1 1-1/8 1-1/4 1-/3/8 1-1/2 1-/5/8 1-3/4 1-7/8 065 .065 .065 .065 058 .058 .058 .058 .058 .058 B 7/8 1 1-1/8 1-1/4 1-3/8 1-1/2 1-5/8 1-3/4 1-7/8 _2 ALL .058 THICK RIVET DIA 5/32 5/32 3/16 3/16 3/16 3/16 1/4 1/4 1/4 1/4 L 9-3/8 9-3/8 11-1/4 11-1/4 11-1/4 11-1/4 15 15 _ 15 15 * INCLUDES ALL THICKNESSES UP TO AND INCLUDING MAXIMUM SHOWN.
NOTE. USE SAME MATERIAL AS ORIGINAL FOR SLEEVE AND REPLACEMENT TUBE.
b. Repairs to Aluminum Alloy Members. Make repairs to aluminum alloy members with the same material or with suitable material of higher strength. The 7075 alloy has greater tensile strength than other commonly used aluminum alloys such as 2014 and 2024, but is subject to somewhat greater notch sensitivity. In order to take advantage of its strength characteristics, pay particular attention to design of parts to avoid notches, small radii, and large or rapid changes in cross-sectional areas. In fabrication, exercise caution to avoid processing and handling defects, such as machine marks, nicks, dents, burrs, scratches, and forming cracks. Cold straightening or Par 4-58 Page 4-34
Par 4-58 Page 4-35 forming of 7075-T6 can cause cracking; therefore, it may be advisable to limit this processing to minor cold straightening.
c. Wing and Tail Surface Ribs. Damaged aluminum alloy ribs either of the stamped sheet-metal type or the built-up type employing special sections, square or round tubing, may be repaired by the addition of suitable reinforcement. (Acceptable methods of repair are shown in Figure 4-13 and Figure 4-14.) These examples deal with types of ribs commonly found in smalland medium-size aircraft. Repair schemes developed by the aircraft manufacturer are acceptable, but any other methods of reinforcement are major repairs and require approved data.
d. Trailing and Leading Edges and Tip Strips. Repairs to wing, control surface trailing edges, leading edges, and tip strips should be made by properly executed and reinforced splices.
Acceptable methods of trailing edge repairs are shown in Figure 4-15.
e. Repair of Damaged Skin. In cases where metal skin is damaged extensively, repair by replacing an entire sheet panel from one structural member to the next. The repair seams are to lie along stiffening members, bulkheads, etc.; and each seam must be made exactly the same in regard to rivet size, splicing, and rivet pattern as the manufactured seams at the edges of the original sheet. If the two manufactured seams are different, the stronger one will be copied. (See Figure 4-16 for typical acceptable methods of repairs.)
FIGURE 4-13. TYPICAL REPAIR FOR BUCKLED OR CRACKED METAL WING RIB
CAP STRIPS
- D CRACK 0 30 30 3020203030,30 D
AT LEAST AS THICK
AS ORIGINAL
ORIGINAL
REINFORCEMENT MaTERIaL — DURAL.OR 2117-AD RIVETS ALUMINUM ALLOY USED IN 3/32" DIA. MIN.
ORIGINAL CONSTRUCTION.
SCALE - TWICE SIZE SECTION A-A
SCALE - TWICE SIZE
- 2017-T3 D SQ. ROD 30_ 30 3D 3D 30, 30 30 3D 30 • 2117-AD RIVETS 1/8" DIA: MIN.
NOTE: FOR MINIMUM NUMBER OF RIVETS REQUIRED, SEE PARAGRAPH 4-58g AND SUBSEQUENT.
Par 4-58 Page 4-36
FIGURE 4-14. TYPICAL METAL RIB REPAIRS (USUALLY FOUND ON SMALL-
AND MEDIUM-SIZE AIRCRAFT)
SEE (C) SEE (D) 1000 OTO (A) + SEE (E) (B) D = RIVET DIA.
ROX.) (MINIMUM 3/32") TER.
BEND RADI TO FIT
ORIGINAL RIB.
(G) 3/16 PLYWOOD TO STIFFEN BENT RIBS.
- D - MACHINE SCREW OR RIVET.
• 1.5 ₺ (APPROX.)
- PEEN (E) 2030_30 2020130|30.22 (D) NOTE: FOR MINIMUM NUMBER OF RIVETS REQUIRED, SEE PARAGRAPH 4-58g AND SUBSEQUENT.
Par 4-58 Page 4-37
FIGURE 4-15. TYPICAL REPAIRS OF TRAILING EDGES "А" "B" 2024-T3 SPLICE BAR 040" 2017-T3 SPACER "Д" 20,30 30 202030,30 20 I-+i "В" - 8 030001 2117-AD RIVETS →4-0 3/32" DIA. MIN. CRACK 2117-AD RIVETS 3/32" DIA. MIN. « Д→
- ЗА ЗА I. STRAIGHTEN CRIMPED OVER PORTION. - CRACK
2. INSERT HARDWOOD (ASH) INSERT SHAPED.
TO CONFORM TO T.E. PIECE.
2117-AD RIVETS 20 20 2D D 3/32" DIA. MIN.
FLATTEN HEADS (APPROX. 1.5 t ) OUTSIDE I. STRAIGHTEN CRIMPED PORTION. - CRACK
2. USE SAME AL. ALLOY AS IN ORIGINAL.
Par 4-58 Page 4-38
FIGURE 4-16. TYPICAL REPAIRS OF STRESSED SHEET METAL COVERINGS (SEE TABLES 4-9, 4-10, AND 4-11 TO CALCULATE NUMBER OF RIVETS TO BE USED) (A) ADDED
STIFFENERS TO →15; 2 EACH BACK UP SEAM | 24-5/32" REQ'D OF PATCH.
2117-T4 BACKED PATCH PLATE
BY SAME TO BE OF SAME 3" HOLE MAX. DIA. JRIVETS 2" HOLE MAX DIA |22=112 MATERIAL AS ORIGINAL AND SAME OR NEXT HEAVIER GAUGE.
16-5/32" RIVET SIZE, 2117-T4 RIVETS SPACING,
MATERIAL, AND
PATTERN "G", "H", AND "K SAME AS ARE ORIGINAL A B.
CIRCULAR PATCH PLATES. DAMAGED SKIN DIMENSIONS OF CIR. PATCH PLATES SHOULD BE DESIGNATION "K" "H" "G" CLEANED OUT DIAMETER (OUTSIDE) 2-1/2" 5" 7-12" SMOOTHLY AS DIA. INNER RIVET CIRCLE 1-3/4" 3" 4" INDICATED BY DIA. OUTER RIVET CIRCLE 4" 6-1/2" CDEF.
SAME RIVET SIZE, SPACING, MATERIAL, & PATTERN AS B C.
SAME RIVET SIZE, SPACING, MATERIAL, & PATTERN AS A D.
PATCH PLATE
TO BE QF SAME
•1" HOLE MATERIAL AS 8-5/32" 2117-T4 MAX DIA. ORIGINAL AND
RIVETS SAME OR NEXT
HEAVIER GAUGE CRACK — NOT LESS THAN 2 TIMES LENGTH SPORTION OF SKIN REPLACED. OF CRACK ORIGINAL SKISEET 4 RIVETS REQD. EACH SIDE
RIVET SPACING AT LEAST 3X RIVET DIA
HOLES DRILLED TO PREVENT CRACK SPREADING.
SKIN GAUGE = .028" (B) RIVET DIA. = 1/8" CRACK 2.5" LONG Par 4-58 Page 4-39