TECHNICAL BULLETIN
206L-07-226 8 October 2007 Revision A, 1 July 2014
MODEL AFFECTED:
206L Series
SUBJECT:
IMPROVED UPPER LEFT LONGERON / FITTING ASSEMBLY 206-031-314-217B OR -233B AND AFT FUSELAGE BULKHEAD 407-030-027-103, INTRODUCTION OF.
HELICOPTERS AFFECTED:
Part I and Part II Model 206L S/N 45003 through 45153 and 46601 though 46617, Model 206L1 S/N 45154 through 45790, 206L3 S/N 51001 through 51612, and Model 206L4 S/N 52001 through S/N 52357. [Model 206L4 helicopters S/N 52358 and subsequent will have the intent of this bulletin accomplished prior to delivery.] Part III and Part IV Model 206L S/N 45003 through 45153 and 46601 through 46617, Model 206L1 S/N 45154 through 45790, 206L3 S/N 51001 through 51612, and Model 206L4 S/N 52001 through S/N 52366. [Model 206L4 helicopters S/N 52367 and subsequent will have the intent of this bulletin accomplished prior to delivery.]
COMPLIANCE:
At customer’s option, or when the aft upper left longeron and/or fitting replacement is required, or when the aft fuselage bulkhead replacement is required.
TB 206L-07-226-RA Page 1 of 44 Export Classification C, ECCN EAR99 Approved for public release.
DESCRIPTION: Bell Helicopter Textron recently introduced a new upper left tailboom attachment fitting on the fuselage of the Model 206L4 helicopters. This improved fitting, made of CRES material, can also be used on all Model 206L series helicopters as a spare replacement. Due to special assembly procedures (CRES fitting hot bonded and cold work fastener holes), this part can only be procured as an aft longeron and fitting assembly under 206-031-314-217B. Detail parts of this assembly will not be procurable separately. Revision A makes a correction to the MATERIAL section of this bulletin in order to offer a newer aft longeron and fitting assembly 206-031-314-233B as an option or after depletion of the aft longeron and fitting assembly 206-031-314-217B. This bulletin also introduces a new machined aft fuselage bulkhead. This improved bulkhead is made of aluminum with thicker material in radius and wider flanges for better fit and reliability. This bulkhead can be used as a direct replacement on the Model 206L series helicopters. Part I of this bulletin provides instructions to remove the upper left longeron/fitting and the aft fuselage bulkhead. It gives the requirements and defines limitations that will permit the use of a portable drill plate. Part II of this bulletin provides instructions to install the new upper left longeron/fitting assembly and reuse of the existing sheet metal aft bulkhead. Even though reuse of the sheet metal aft bulkhead is possible, it is recommended to install the new machined aft fuselage bulkhead in accordance with Part III or Part IV. Part III of this bulletin provides instructions to install the new machined aft fuselage bulkhead. This procedure can be used when replacing the aft fuselage bulkhead only or in conjunction with the replacement of the upper left longeron/fitting assembly. Part IV is an alternate to this procedure. Part IV of this bulletin gives a procedure to install the new machined aft fuselage bulkhead when the pilot hole in the new bulkhead does not match with the center of the bolt hole in the existing longeron/fitting. This is an alternate method to Part III.
TB 206L-07-226-RA Page 2 of 44 Export Classification C, ECCN EAR99 Approved for public release.
-NOTEModel 206L4 helicopters S/N 52186 through 52357 were manufactured with the upper left longeron/fitting 206-031314-157A. Product Support Engineering has authorized field replacement of this assembly on the Model 206L/L1/L3 and L4 helicopters. Helicopters fitted with the longeron 206-031314-157A meet the intent of Part I and Part II of this bulletin. In comparison with the longeron/fitting 206-031-314-157A, the -217B has the addition of a tapered shim and a radius block. In comparison with the -217B, the -233B has an additional doubler hot bonded to the channel. APPROVAL: The engineering design aspects of this bulletin are Transport Canada Civil Aviation (TCCA) approved. CONTACT INFO: For any questions regarding this bulletin, please contact: Bell Helicopter Product Support Engineering - Light Helicopters Tel: 450-437-2862 / 1-800-363-8023 /
[email protected] MANPOWER: Approximately 28.0 man-hours are required to complete Part I and Part II of this bulletin. Approximately 12.0 man-hours are required to complete Part III or Part IV of this bulletin. Man-hours are based on hands-on time, and may vary with personnel and facilities available. WARRANTY: There is no warranty credit applicable for parts or labor associated with this bulletin. MATERIAL: Required Material: The following material is required for the accomplishment of this bulletin and may be obtained through your Bell Helicopter Textron Supply Center.
TB 206L-07-226-RA Page 3 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Part Number
Nomenclature
206-031-314-217B
Aft longeron and fitting assembly (Note 10) Bolt (Note 4) Aft bulkhead (Note 1) Left aft skin (Note 2, 5) Upper skin (Note 5) Pin Collar Nutplate Nutplate (Note 7) Rivet (Note 3) Rivet (Note 3) Rivet (Note 3) Rivet (Note 3) Rivet (Note 3) Rivet (Note 3) Rivet (Note 3, 6) Rivet (Note 3) Rivet (Note 3) Rivet (Note 3, 5) Rivet blind (Note 3) Rivet blind (Note 3, 8) Rivet blind (Note 3)
20-065-06028 407-030-027-103 206-033-003-153 206-033-003-161 100-048-6-7 30-015-6 MS21075L3 MS21061L3 MS20470AD3 MS20470AD4 MS20470AD5 MS20426AD3 MS20426AD4 MS20426AD5 MS20426E4 MS20615-3MP NAS1738MW5 NAS1200M4P M7885/2-4 M7885/7-4 M7885/9-4
Quantity 1 1 1 1 (optional) 1 (optional) 2 2 7 1 (optional) A/R A/R A/R A/R A/R A/R A/R A/R A/R 10 (optional) A/R A/R (optional) A/R (optional)
NOTES: 1. Required only if existing bulkhead 206-032-308-003/-103 or 407-030-027-103 needs replacement when performing Part I and Part II. 2. Required only if existing skin 206-033-003-153 or both skins 206-033-003-137 and -139 need replacement. 3. Quantity and rivet length to be determined at installation. 4. Refer to ASB 206L-06-140 for thread count and washer requirement. 5. If hot dimpling capability is not available. As an alternate to hot dimpling the longeron, install the new left aft skin 206-033-003-153 and the upper skin 206-033003-161. Install the 10 NAS1200M4P rivets in lieu of the MS20426AD4 rivets. Countersink the upper skin only (Figure 1, Note 9). 6. The M7885/9-4 blind rivet can be used as an alternate to MS20426E4 (Figure 1, Note 2). 7. One MS21061L3 can be used as an alternate for the MS21075L3 nutplate at one location only (Figure 1, Note 3). 8. The M7885/7-4 blind rivet can be used as an alternate to MS20426AD4 (Figure 1, Note 2).
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9. Aluminum material 2024T3 per QQ-A-250/4 may be required to locally fabricate shims. The size and thickness of the shims will be determined at installation. Thickness limitations are provided in the Accomplishment Instructions of this bulletin. 10. The aft longeron and fitting assembly 206-031-314-233B can be used as an alternate to 206-031-314-217B. Consumable Material: The following material is required to accomplish this bulletin, but may not require ordering, depending on the operator’s consumable material stock levels. This material may be obtained through your Bell Helicopter Textron Supply Center. Part Number
Nomenclature
MIL-PRF-81733 2.5 OZ Acetone gallon MIL-P-85582,TY1, CL2 MIL-C-81706 1 QT
Sealant Acetone (per Q-A-51) Primer Chem Film, alodine 1200
Quantity
Reference
1 1 1 1
C-392 (Note 1) C-316 (Note 2) C-204 (Note 3) C-100
NOTES: 1. As an alternate, use MIL-S-81733. 2. As an alternate, use Methyl Ethyl Ketone (C-309). 3. As an alternate, use MIL-P-23377. SPECIAL TOOLS: Tailboom drill plate (Structural Repair Manual BHT-206-SRM-1, Appendix B-2) Flange bushings and drill bushings. Refer to Figure 2 for size required. Hot dimpling equipment: Thermo dimple control panel No. ZT2409-G (or equivalent) with portable dimpler No. ZT2427 or ZT2429 (Product of Zephyr Manufacturing Co). WEIGHT AND BALANCE: Bell Helicopter Textron considers this modification to have no significant effect to the helicopter weight and balance. ELECTRICAL LOAD DATA: Not affected.
TB 206L-07-226-RA Page 5 of 44 Export Classification C, ECCN EAR99 Approved for public release.
REFERENCES: BHT-206L-SERIES-IPB, Illustrated Parts Breakdown BHT-206-SRM-1, Structural Repair Manual BHT-206-MM-1, Maintenance Manual BHT-206L1-MM-1, Maintenance Manual BHT-206L3-MM-1, Maintenance Manual BHT-206L4-MM-1, Maintenance Manual ASB 206L-06-140, Upper left tailboom attachment hardware, Inspection of, BHT-ALL-SPM, Standard Practice Manual PUBLICATIONS AFFECTED: BHT-206L-SERIES-IPB, Illustrated Parts Breakdown ACCOMPLISHMENT INSTRUCTIONS: Part I: Removal of the existing upper left longeron and aft fuselage bulkhead 1. Prepare the helicopter as follows: a. Disconnect the battery. b. Refer to the applicable chapter in the Maintenance Manual and get access to the aft left longeron area by removing the following items: (1) Engine cowl. (2) Oil cooler blower fairing. (3) Tail rotor driveshaft (steel) between the engine and the oil cooler. (4) Engine. (5) Engine oil reservoir. (6) Segmented short shaft assembly. (7) Oil cooler and blower assemblies. (8) Tailboom. (9) Hat bin, blanket assemblies, and liner from the aft end of the cabin above and behind the rear passenger seat. (10) Remove any ducts, doors, or equipment in the aft cabin closure.
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(11) Discard the left upper bolt that attaches the tailboom to the fuselage. Retain the remaining hardware for reuse. c. Protect or remove any electrical, electronic, ECU, and heating equipment that may be mounted on the canted web.
-NOTEThe helicopter must be in a BHT approved fuselage fixture if the cause of the longeron assembly replacement is an incident or accident. 2. At FS 231.4, remove the aft fuselage bulkhead (1) from the fuselage as follows: a. Refer to Figure 1, View A. (1) For Model 206L/L1 and L3 helicopters, drill and remove eight rivets (14), three rivets (55), and two rivets (12) that secure the upper skin (49), and both left and right upper longeron/fittings. (2) For Model 206L4 helicopters, drill 9 rivets (15) and four rivets (12) that secure the upper skin (49), and both left and right upper longeron/fittings. b. Remove the two Hi-lok pins (13) that secure the left and right lower longeron/fittings. c. Drill and remove the 14 rivets (16) and two rivets (17) that secure the left aft skin (7). d. Drill and remove the 11 rivets (21) that secure the lower fairing (50). e. Drill and remove the 11 rivets (18 or 19) that secure the web (51). f. Drill and remove the one rivet (24) that secures the right angle support (3). g. Drill and remove the eight rivets (20) that secure the clips (2, 4, and 5) on the aft face of the bulkhead (1).
-NOTESolid shims may have been installed around the circumference of the bulkhead (1) to fill the existing gap. Retain these shims for reinstallation.
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h. Separate the bulkhead (1) from the aft fuselage structure with a warm thin blade putty knife to release sealant. Remove the bulkhead and keep for reinstallation. 3. Locally manufacture a drill plate to the dimension shown in the BHT-206-SRM-1. 4. Verify that the fuselage to the tailboom attachment bolt pattern matches with the drill plate.
-NOTEThe maximum diameter allowed in service on the upper and the lower longeron bolt hole is 0.391 inch. a. If the bolt hole pattern matches the drill plate and each hole does not exceed the maximum diameter, go to step 5. b. If any bolt hole does not match, the affected longeron must be replaced with the helicopter loaded in a BHT approved fuselage fixture. 5. Verify that the four longeron/fittings are in plane within 0.002 inch. a. Attach the drill plate to the four longeron/fittings with the existing hardware and torque the nuts to 50 inch-pounds. A gap in excess of 0.002 inch between the drill plate and the aft face of the longeron/fitting indicates that this longeron/fitting is not in plane. b. If the longeron/fittings are in plane, go to step 6. c. If one longeron/fitting is not in plane other than the upper left longeron, the affected longeron/fitting must be replaced using the drill plate prior to replacing the upper left longeron. d. If more than one longeron/fitting is not in plane, the affected longeron/fitting must be replaced with the helicopter loaded in a BHT approved fuselage fixture.
-NOTEFour spacers of equivalent thickness (+/- 0.001 inch) may be required between each tailboom attachment fitting and the drill plate to prevent interference with the fuselage skins.
TB 206L-07-226-RA Page 8 of 44 Export Classification C, ECCN EAR99 Approved for public release.
-NOTEIt is not necessary to disassemble the left fuselage-totailboom attachment fitting from the main longeron and the inboard channel. The new channel, clips, and aft longeron and fitting assembly 206-031-314-217B or -233B will replace the existing parts as a unit. 6. Record the type and size of the rivets before their removal. Drill and remove the 22 rivets that secure the oil cooler cowl retainer L/H (6). With a putty knife, break the sealant and remove the retainer. Keep the retainer for reinstallation. Drill and remove the rivets that secure the skins (7 or 8). The skins may be in one or two pieces. Use care to break the sealant and remove the skin.
-NOTEThe forward skin (9) can be removed completely. As an option, the skin can be spliced at FS 192.00 in accordance with the BHT-206-SRM-1. 7. Drill and remove all the rivets that secure the forward skin (9). With a putty knife, break the sealant and remove the skin. 8. At FS 192.00, remove the 10 rivets (27, View C) that secure the forward longeron (11) to the aft longeron and fitting assembly (10). Remove the four rivets (32, View F-F) that secure the doubler (31) to the aft longeron and fitting assembly. 9. At FS 204.92, remove the two rivets (27, View C and View G-G) that secure the clips (33 and 38) to the aft longeron and fitting assembly (10). 10. Remove the two rivets (35, View D and View G-G) that secure the clip (38) to the bulkhead. Separate the clip and keep for reinstallation. Remove the two rivets (36) and the four rivets (34) that secure the clip (33) and the splice (48). Separate the clip and the splice and keep for reinstallation. 11. At FS 217.84, remove the one remaining rivet (39, View D and View H-H) that secures the upper skin (49) through the splice (45). Remove the splice and keep for reinstallation. Remove the two rivets (46) that secure the clips (41 and 42) to the aft longeron and fitting assembly (10). Remove the two rivets (47) that secure the clip (43) to the aft longeron and fitting assembly. 12. Remove the six rivets (44) that secure the clips (41, 42, and 43) to the bulkhead. Separate the clips and keep for reinstallation. TB 206L-07-226-RA Page 9 of 44 Export Classification C, ECCN EAR99 Approved for public release.
13. Break the sealant at the interface between the aft longeron and fitting assembly (10) and the forward longeron (11). Remove the aft longeron and fitting assembly from the aft fuselage assembly by gently sliding out of position toward the aft of the helicopter. Part II: Installation of the new aft longeron and fitting assembly and the reuse of the existing sheet metal aft fuselage bulkhead. 1. Clean the cured sealant from the faying surfaces of all parts. 2. Draw a center line on the upper flange of the aft longeron and fitting assembly (10) to ensure correct location of the rivet. Draw a center line on the lower flange where the doubler (31) is attached. Slide the new aft longeron and fitting assembly into position. 3. Temporarily install the existing bulkhead (1) in position.
-NOTEFour spacers of equivalent thickness (+/- 0.001 inch) may be required between each tailboom attachment fitting and the drill plate to prevent interference with the fuselage skins. 4. Temporarily secure the drill plate to the R/H upper longeron/fitting and both lower longeron/fittings (9, Figure 2, View E) with the existing bolts and nuts and torque to 50 inch-pounds. A stack of washers might be required to ensure the grip length is adequate. Attach the drill plate to the new longeron and fitting, upper left (6, View D) with a 3/16 inch bolt and nut through the existing 3/16 inch pilot hole already drilled in the longeron, and torque to 50 inch-pounds. Make sure that there is no gap at the four locations between the longeron/fitting and the bulkhead. 5. Position the forward portion of the aft longeron and fitting assembly (10, Figure 1) to make sure that the top surface of the longeron is flush with the upper surface of the bulkheads against the upper skin. Temporarily clamp the aft longeron and fitting assembly to the forward longeron (11). Make sure that the line previously marked on the upper and lower flanges of the longeron match with the existing rivet patterns of the upper skin (49) and doubler (31). Make sure that the minimum edge distance is within limits. New skins must be installed if the minimum edge distance of 2D is not met on the longeron. Do not drill the upper flange of the longeron at this time. 6. Temporarily install the splice (48, View G-G) and the clips (33 and 38) with clecos. TB 206L-07-226-RA Page 10 of 44 Export Classification C, ECCN EAR99 Approved for public release.
7. Temporarily install the splice (45, View H-H) and the clips (41, 42, and 43) with clecos. 8. Transfer the 10 rivet holes from the forward longeron (11, View C and View H-H). Transfer four rivet holes (32) from the doubler (31) to the lower flange of the aft longeron and fitting assembly (10). At STA 204.92, transfer two rivet holes from the clip (38). At Sta 217.81, transfer two rivet holes from the clips (41 and 43) to the side of the aft longeron and fitting assembly (10) and secure with clecos. 9. Transfer the rivet holes from the splices (45 and 48, View D) to the upper flange of the aft longeron and fitting assembly (10). 10. Temporarily install the skins (7 and 9) with clecos. Transfer all the rivets holes from the skins (7, 9, and 49) to the upper flange of the aft longeron and fitting assembly (10) and secure with clecos. 11. Transfer one rivet hole (12, View A) from the flange of the bulkhead (1) to the aft longeron and fitting assembly (10). Transfer four rivets holes (20) from the bulkhead to the clips (2 and 4).
CAUTION THE LONGERON IS MADE OF 7075 T6 MATERIAL THAT IS CHEMICALLY MILLED FROM 0.063 INCH AT STA 231.4 TO 0.032 INCH AT STA 192.00. FAILURE TO HOT DIMPLE THE LONGERON FOR THE COUNTERSINK RIVET MAY RESULT IN CRACKING IN SERVICE. COLD DIMPLE PROCESS INTO THE LONGERON IS NOT ACCEPTABLE. 12. Remove all the clecos and the drill plate. Separate the aft longeron and fitting assembly (10) from the structure. Deburr all rivets holes. -NOTEAs an alternate to hot dimpling the aft longeron and fitting assembly (10) at the location for the 10 rivets (29), it is acceptable to replace the skins (7 and 49) at the same time and do a countersink in the skin (49) only. Install the new left aft skin (7) and the new upper skin (49) with the 10 rivets (53) in lieu of the rivet (29). Countersink the upper skin only to suit the rivet (53). Do not perform step 13. 13. Dimple the 10 rivet holes (29) using the hot dimple process (Annex A). TB 206L-07-226-RA Page 11 of 44 Export Classification C, ECCN EAR99 Approved for public release.
14. Brush coat the mating faces of the forward longeron (11) and the aft longeron and fitting assembly (10) with sealant (C-392). Install the aft longeron and fitting assembly into place with clecos. Do not install the aft skin (7) at this time. 15. Reinstall the bulkhead (1) with clecos. Reinstall the drill plate (1, Figure 2, View D) with a 3/16 inch diameter bolt (7) at the new longeron and fitting, upper left (6). Use the existing bolt to attach the drill plate to the three other fittings (9, View E). Torque the bolts (7 and 11) and the nuts (8 and 12) to 50 inch-pounds. 16. Secure the forward section of the aft longeron and fitting assembly (10, Figure 1) with the rivets (27). 17. Secure the doubler (31) with the rivets (32). 18. Secure the clips (33 and 38, View G-G) to the aft longeron and fitting assembly (10) with the rivets (27). Secure the clips (33) to the bulkhead with the rivets (34) and secure the clip (38) to the bulkhead with the rivets (35). 19. Secure the clip (43, View H-H) to the aft longeron and fitting assembly (10) with the rivets (47). Secure the clips (41 and 42) to the aft longeron and fitting assembly with the rivets (46). Secure the clips (41, 42, and 43) to the bulkhead with the rivets (44). 20. Apply sealant (C-392) to all the faying surfaces and edges of the fuselage skins (7, 9, and 49). 21. Do not install rivets for the retainer L/H (6, View D) at this time. Secure the skins (7, 9, and 49) to the aft longeron and fitting assembly (10) with the rivets. 22. Brush coat the mating surface of the retainer L/H (6) with sealant (C-392). Install the retainer L/H on top of the skins (9 and 49). Secure the retainer L/H to the skins and to the aft longeron and fitting assembly (10) with the same type of rivets recorded before their removal. Do not install the rivets through the bulkhead (1) at this time. 23. Install all the rivets through the skins (7 and 9) with same type of rivets recorded before their removal. -NOTEIt is acceptable to reuse the previously removed sheet metal aft bulkhead (1). However, it is recommended to install the new machined aft bulkhead. If a new machined bulkhead is installed, accomplish Part III (preferred method) or accomplish Part IV (alternate method). If the same aft sheet metal aft bulkhead is reinstalled, go to step 24. TB 206L-07-226-RA Page 12 of 44 Export Classification C, ECCN EAR99 Approved for public release.
24. Secure the aft bulkhead (1, View A) to the aft fuselage with the rivets. 25. Remove the bolt (7, Figure 2) and the nut (8) from the longeron and fitting, upper left (6). Remove the bushing (3).
-NOTEThe upper left fitting is made of CRES material that is difficult to drill. Low speed drilling is required to avoid overheating the material. Drill by increasing the size of the drill bit until final ream can be achieved. Drilling by step increments will require a variety of bushing sizes that are not listed in this bulletin. It is at the discretion of the operator. 26. Drill by increasing the size of the drill bit until you can final ream to 0.376 to 0.378 inch through the bulkhead (1, Figure 1, Section E-E), aft longeron and fitting assembly (10), and radius block (52). 27. Back spotface the forward surface of the radius block (52) to 0.750 inch diameter, deep enough to have a constant flat surface. The depth of the spotface must not exceed 0.040 inch. 28. Remove the drill plate (1, Figure 2) from the aft fuselage. Deburr and clean the hole and the spotface in the longeron and fitting, upper left (6). 29. Apply primer (C-204) to all bare surfaces including the spotface surface in the radius block (52). Apply a joint of sealant (C-392) at each edge of the skins. 30. Refinish the paint, as required. 31. Remove the protective cover from the equipment on the canted web.
-NOTEAs compared to the previous installation, the total thickness of the aft longeron and fitting assembly (10, Figure 1) and the radius block (52) is larger. Therefore, a longer bolt (56) is required at the upper L/H longeron to attach the tailboom. Refer to ASB 206L-06-140 for thread count and washer requirements.
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32. Reinstall all items that were removed in step 2 and step 3 of Part I. Use the new bolt (56) at the upper L/H longeron to attach the tailboom to the fuselage. 33. Make an entry in the helicopter logbook and historical service records indicating compliance with this Technical Bulletin. Part III: Installation of a new machined aft fuselage bulkhead (preferred method) -NOTEThis procedure uses the existing 3/16 inch pilot holes in the new machined frame. Part IV is an alternate to this procedure when the pilot holes do not match with the center of the hole in the aft longeron and fitting assembly and the drill plate.
-NOTEModels 206L/L1 and L3 are using the same size and type of rivets to secure the aft bulkhead. Model 206L4 is using a different size and type at specific locations. Make sure to use the proper rivet size and type. If solid shims are reinstalled, use the same type and size of rivets recorded before their removal. -NOTEFour spacers of equivalent thickness (+/- 0.001 inch) may be required between each tailboom attachment fitting and the drill plate to prevent interference with the fuselage skins. 1. Remove the drill plate (1, Figure 2) from the aft fuselage, if already installed. 2. Remove the existing bulkhead (5) in accordance with Part I, step 2 and keep it to fabricate a template. Install the new aft bulkhead in position. Attach the drill plate (1, View A) to the aft fuselage at the longeron and fitting, upper left (6). Attach the drill plate through the three other fittings (9, View B). Torque all the bolts (7) and the nuts (8) to 50 inch-pounds. 3. Do not drill holes for the nutplates (22, Figure 1, View A) and holes for the rivets (18 or 19) at this time. Transfer all the rivet holes from the aft fuselage to the bulkhead (1) and install clecos. TB 206L-07-226-RA Page 14 of 44 Export Classification C, ECCN EAR99 Approved for public release.
-NOTEDo not install shims between the aft face of the longeron/fitting and the bulkhead. -NOTEOn Models 206L/L1 and L3, if a shim (maximum of 0.016 inch thick) is installed between the upper skin and the bulkhead, the rivets installed through this shim shall be changed for the size and type of the Model 206L4. 4. Make sure that there is no gap between the side flange of the aft bulkhead and skins or the longerons. If a gap exists, fabricate the shim with Aluminum 2024T3 material to fill the gap. Taper the shim, as required, to a minimum thickness of 0.005 inch. Maximum thickness of the shim must not exceed 0.016 inch at any location (exception to gap is described in Figure 1, Notes 7, 11, and 12). 5. Temporarily install the access door (26) with the screws (25) on the right side of the fuselage. Locate the seven holes from the door for the nutplates (22). Drill seven holes, size 0.190 to 0.196 inch. Remove the access door. 6. Remove the drill plate (1, Figure 2), clecos, and aft bulkhead (5). 7. Fabricate a template with the old bulkhead by removing the side flange from the old bulkhead. Position the template over the new bulkhead (1, Figure 1) using the longeron bolt holes as a locator. Transfer the 11 rivet holes (18 or 19) in the new bulkhead. Remove and discard the template. 8. Deburr all the holes. Install the seven nutplates (22) with the rivets (23). 9. Reinstall the new bulkhead (5, Figure 2) into position with the clecos. Attach the drill plate (1, View A) to the aft fuselage at the longeron and fitting, upper left (6). Attach the drill plate through the three other fittings (9, View B). 10. Secure the aft bulkhead (1, Figure 1, View A) with the rivets. 11. Remove the bolt (7, Figure 2), nut (8), bushings (3 and 10) from the upper right fitting (9). Drill by increasing the size of the drill bit until you can final ream the bulkhead (5) to 0.376 to 0.378 inch (View C). Install a 3/8 inch size bolt and nut, and torque to 50 inch-pounds. 12. Do step 11 for both lower fitting locations.
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13. Remove the bolt (7) and the nut (8) from the longeron and fitting, upper left (6). Remove the bushing (3).
-NOTEThe upper left fitting is made of CRES material that is very hard to drill. Low speed drilling is required to avoid overheating the material. Drill by increasing the size of the drill bit until final ream can be achieved. Drilling by step increments will require a variety of bushing sizes that are not listed in this bulletin. It is at the discretion of the operator. 14. Drill by increasing the size of the drill bit until you can final ream 0.376 to 0.378 inch through the bulkhead (1, Figure 1, Section E-E), aft longeron and fitting assembly (10), and radius block (52). 15. Back spotface the forward surface of the radius block (52) to 0.750 inch diameter, deep enough to have a constant flat surface. Depth of the spotface must not exceed 0.040 inch deep. 16. Remove the drill plate (1, Figure 2) from the aft fuselage. Deburr and clean the longeron fitting hole and the spotface. 17. Apply primer (C-204) to all bare surfaces including the spotface surface in the radius block (52). Apply sealant (C-392) at each edge of the skins. 18. Refinish the paint, as required. 19. Remove the protective cover from the equipment on the canted web. -NOTEAs compared to the previous installation, the total thickness of the aft longeron and fitting assembly (10) and the radius block (52) is larger. Therefore, a longer bolt is required at the upper left longeron to attach the tailboom. Refer to ASB 206L-06-140 for thread count and washer requirement. 20. Reinstall all the items that were removed in step 2 and step 3 of Part I. Use the new bolt (56) at the upper left longeron to attach the tailboom to the fuselage. 21. Make an entry in the helicopter logbook and historical service records indicating compliance with this Technical Bulletin.
TB 206L-07-226-RA Page 16 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Part IV: Installation of a new machined aft fuselage bulkhead (alternate method) -NOTEThis procedure does not use the existing 3/16 inch pilot holes in the new machined frame. -NOTEModel 206L/L1 and L3 are using the same size and type of rivets to secure the aft bulkhead. Model 206L4 is using a different size and type at specific locations. Make sure to use the proper rivet size and type. If solid shims are reinstalled, use the same type and size of rivets recorded before their removal. -NOTEFour spacers of equivalent thickness (+/- 0.001 inch) may be required between each tailboom attachment fitting and the drill plate to prevent interference with the fuselage skins. 1. Remove the drill plate (1, Figure 2) from the aft fuselage, if already installed. 2. Remove the existing bulkhead (5) in accordance with Part I, step 2 and keep it to fabricate a template. Verify that the bolt holes in the upper right longeron and both lower longeron fittings (9) match with the bushing holes in the drill plate (1). Install the new aft bulkhead in position.
CAUTION DO NOT DAMAGE THE BULKHEAD LONGERON/FITTING. USE PROTECTIVE WHEN SECURING WITH A C-CLAMP.
OR THE MATERIAL
3. Temporarily secure the bulkhead (5) at each longeron/fitting with a C-clamp. 4. Install three flange bushings (10) in the upper right longeron and both lower longerons fittings (9). Disregard the existing pilot holes in the aft bulkhead (5). Backdrill 0.187 to 0.189 inch from the longeron/fitting into the bulkhead at those three locations. These are the new pilot holes.
TB 206L-07-226-RA Page 17 of 44 Export Classification C, ECCN EAR99 Approved for public release.
5. Remove the bulkhead (5) from the fuselage. On a bench, install the bushings (2 and 3) in the drill plate (1) for the upper right and both lower longeron fitting (9) holes. Attach the bulkhead to the drill plate with the 3/16 inch diameter bolts (7), nuts (8), and washers (14, as required) through the three new pilot holes previously drilled in step 4. Torque to 50 inch-pounds. Secure the bulkhead to the drill plate with a C-clamp all around the circumference. 6. Remove the 3/16 inch diameter bolt (7), nut (8), and washer (14) from the lower right longeron/fitting hole and drill by increasing the size of the drill bit until you can final ream the bulkhead (5) 0.376 to 0.378 inch. Install a 3/8 inch diameter bolt (11), nut (12), and washer (13, as required), and torque to 50 inch-pounds. 7. Repeat step 6 for the lower left longeron and fitting hole. 8. Repeat step 6 for the upper right longeron and fitting hole. 9. Remove the C-clamp, nuts (12), washers (13), and bolts (11). Separate the bulkhead (5) from the drill plate (1). Deburr all three holes in the longeron fittings (9). 10. Position the bulkhead (5, View E) on the aft fuselage. Install the drill plate through the three longeron fittings (9) with the bolt (11), washer (13), and nut (12). Torque all the nuts to 50 inch-pounds. Secure the longeron and fitting, upper left (6) with a C-clamp. 11. Do not drill holes for the nutplates (22, Figure 1, View A) and the rivet holes (18 or 19) at this time. Transfer all the rivet holes from the aft fuselage to the bulkhead (1) and install with clecos.
-NOTEDo not install shims between the aft face of the longeron fitting and the bulkhead. -NOTEOn Models 206L/L1 and L3, if a shim (maximum of 0.016 inch thick) is installed between the upper skin and the bulkhead, the rivets installed through this shim shall be changed for the size and type of the Model 206L4.
TB 206L-07-226-RA Page 18 of 44 Export Classification C, ECCN EAR99 Approved for public release.
12. Make sure that there is no gap between the side flange of the aft bulkhead and skins or the longerons. If a gap exists, fabricate the shim with Aluminum 2024T3 material to fill the gap. Taper the shim, as required, to a minimum thickness of 0.005 inch. Maximum thickness of the shim not to exceed 0.016 inch at any location (exception to the gap is described in Figure 1, Notes 7, 11, and 12).
-NOTEThe left upper fitting is made of CRES material that is very hard to drill. Low speed drilling is required to avoid overheating the material. Drill by increasing the size of the drill bit until final ream can be achieved. Drilling by step increments will require a variety of bushing sizes that are not listed in this bulletin. It is at the discretion of the operator. 13. Drill by increasing the size of the drill bit until you can final ream 0.376 to 0.378 inch through the bulkhead (1, Section E-E), aft longeron and fitting assembly (10), and radius block (52). 14. Back spotface the forward surface of the radius block (52) to 0.750 inch diameter, deep enough to have a constant flat surface. Depth of the spotface must not exceed 0.040 inch deep. 15. Temporarily install the access door (26) with the screws (25) on the right of the fuselage. Locate the seven holes from the door for the nutplates (22). Drill seven holes 0.190 to 0.196 inch. Remove the access door and the drill plate (1, Figure 2). 16. Remove the clecos and separate the aft bulkead (1, Figure 1) from the aft fuselage. 17. Fabricate a template with the old bulkhead by removing the side flange from the old bulkhead. Position the template over the new bulkhead (1) using the longeron bolt holes as a locator. Transfer the 11 rivet holes (18 or 19) in the new bulkhead. Remove and discard the template. 18. Deburr all holes and spotface the area. Install the seven nutplates (22) with the rivets (23). Apply chemical film (C-100) and primer (C-204) to all bare metal surfaces including the spotface surface in the radius block (52). 19. Reinstall the aft bulkhead (5, Figure 2) into position with the clecos in the rivet holes. Attach the drill plate (1, View E) to the aft bulkhead, three longeron fittings (9), longeron and fitting, upper left (6) with the bolt (11), washer (13), and nut (12). Torque all nuts to 50 inch-pounds.
TB 206L-07-226-RA Page 19 of 44 Export Classification C, ECCN EAR99 Approved for public release.
20. Secure the aft bulkhead (1, Figure 1, View A) with the rivets. 21. Remove the drill plate (1, Figure 2) from the aft fuselage. 22. Apply chemical film (C-100) and primer (C-204) to all bare surfaces. Apply sealant (C-392) at each edge of the skins. 23. Refinish the paint, as required. 24. Remove the protective cover from the equipment on the canted web.
-NOTEAs compared to the previous installation, the total thickness of the aft longeron and fitting assembly (10) and the radius block (52) is larger. Therefore, a longer bolt is required at the upper left longeron to attach the tailboom. Refer to ASB 206L-06-140 for thread count and washer requirement. 25. Reinstall all items that were removed in step 2 and step 3 of Part I. Use the new bolt (56) at the upper left longeron to attach the tailboom to the fuselage. 26. Make an entry in the helicopter logbook and historical service records indicating compliance with this Technical Bulletin.
TB 206L-07-226-RA Page 20 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Figure 1. Installation of Upper L/H Longeron (Sheet 1 of 7) TB 206L-07-226-RA Page 21 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Figure 1. Installation of Upper L/H Longeron (Sheet 2 of 7) TB 206L-07-226-RA Page 22 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Figure 1. Installation of Upper L/H Longeron (Sheet 3 of 7) TB 206L-07-226-RA Page 23 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Figure 1. Installation of Upper L/H Longeron (Sheet 4 of 7) TB 206L-07-226-RA Page 24 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Figure 1. Installation of Upper L/H Longeron (Sheet 5 of 7) TB 206L-07-226-RA Page 25 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Figure 1. Installation of Upper L/H Longeron (Sheet 6 of 7) TB 206L-07-226-RA Page 26 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Figure 1. Installation of Upper L/H Longeron (Sheet 7 of 7) TB 206L-07-226-RA Page 27 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Figure 2. Installation of Drill Plate (Sheet 1 of 3) TB 206L-07-226-RA Page 28 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Figure 2. Installation of Drill Plate (Sheet 2 of 3) TB 206L-07-226-RA Page 29 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Figure 2. Installation of Drill Plate (Sheet 3 of 3) TB 206L-07-226-RA Page 30 of 44 Export Classification C, ECCN EAR99 Approved for public release.
DIMPLING PROCESS – ANNEX A This process sheet establishes requirements for dimpling of aluminum, magnesium, stainless steel and titanium.
1.0
GENERAL INFORMATION
1.1
DESCRIPTION OF PROCESS Dimpling is a process for forming a controlled contour depression in sheet metal to receive the conical head of a flush type fastener to effect a flush installation. The dimple is formed by pressure applied to male and female dies with the sheet in between. Coin dimpling utilizes an additional pressurized internal coining ram to produce a well defined contour on the dimple and restrain expansion of the pilot hole, thereby minimizing cracking tendencies.
1.2
PROCESS LIMITATIONS Dimpling can be applied to all aluminum alloy sheet materials magnesium alloy sheet materials in single thickness up to .081 inch regardless of heat treat (temper) condition. The 300 Series stainless sheet materials up through 1/2 hard condition and all commercially titanium can be dimpled up to .050 inch thick.
1.3
and thick steel pure
DIMPLING REQUIREMENT Dimpling requirements depend on sheet thickness and under sheet thickness. Refer to Table I for dimpling and countersink requirements.
2.0
DIMPLING EQUIPMENT, PROCESS AND PRODUCT REQUIREMENTS
2.1
DIMPLING EQUIPMENT The following equipment is recommended (other brand name equipment may be used provided complete setup and operation instructions are available): Dimpling Machine: Thermo Dimple Control Panel No. ZT2409-G (or equivalent) with portable dimpler No. ZT2427 or ZT2429 (Product of Zephyr Manufacturing Co.). Heaters - Refer to Zephyr equipment catalogue for heater.
TB 206L-07-226-RA Page 31 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Punches and Dies - Refer to Zephyr equipment catalogue for punches and dies. 2.2
PROCESS REQUIREMENT
2.2.1
Dimpling Method Coin Dimpling on stationary or portable equipment shall be the only acceptable method for forming dimples, except when the hole location does not allow sufficient clearance for the coin dimpling dies, the particular dimple may be formed using modified radius dies in stationary or portable equipment. The application of hot or cold dimpling processes shall be as specified in Table II for the applicable material being dimpled.
2.2.2
Machine Settings
2.2.2.1
Hot Dimpling When hot dimpling is specified in Table II the die and punch temperatures, machine dwell time and dwell pressure shall be as specified in the dimpling equipment manufacturer's published equipment operation instructions.
2.2.2.2
Cold Dimpling Where cold dimpling is specified in Table II, the machine setting shall be in accordance with paragraph 2.2.2.1 except that the dwell time shall be set at zero and the punch and die shall be cold.
2.2.2.3
Optional Temperature Where optional temperature is specified in Table II, the machine setting can be in accordance with paragraph 2.2.2.1 or 2.2.2.2.
2.2.3
Material Form Limitations Dimpling may be applied to sheet products only, extruded products shall not be dimpled.
2.2.4
Surface Condition for Dimpling Parts to be dimpled shall be clean and free from oil films, grease, chips and other foreign matter.
2.2.4.1
Surface Coatings Limitations
TB 206L-07-226-RA Page 32 of 44 Export Classification C, ECCN EAR99 Approved for public release.
2.2.4.1.1 Aluminum Alloys Aluminum alloys may be dimpled with bare, chemical film treated or chromic acid anodized surfaces. Dimpling of primed surfaces is also allowed. 2.2.4.1.2 Magnesium Alloys Magnesium alloys shall be dimpled with chromate surface treatment (Dow 7) only. Dimpling of primed surfaces is not allowed. 2.2.4.1.3 Titanium Alloys Titanium alloys shall be dimpled bare. Dimpling of primed surfaces is not allowed. 2.2.4.1.4 All Materials Hot dimpling shall not be performed on any material having the following surface coatings: a. Temporary strippable protective coatings b. Enamels, lacquers, epoxys c. Aluminized paint d. Cadmium or zinc plating 2.2.5
Bonded Laminates Bonded laminated sheets of aluminum alloys or stainless steel alloys or aluminum alloys or stainless steel alloys bonded to plastic laminates shall be dimpled in accordance with paragraphs 2.2.1 and 2.2.2. Machine settings shall be those for a single sheet of the applicable metallic material having a thickness of the total stack up of the bonded laminate.
2.2.6
Re-Dimpling Re-dimpling is permitted only to deepen or obtain better definition on a dimple. Re-dimpling to obtain a larger diameter dimple or to reverse a dimple is not permitted.
2.2.7
Simultaneous Dimpling Simultaneous dimpling (dimpling of more than one sheet at one time) is not allowed.
TB 206L-07-226-RA Page 33 of 44 Export Classification C, ECCN EAR99 Approved for public release.
2.2.8
Pilot Hole Requirements The size of pilot holes may vary provided the hole after dimpling meets all the requirements for the specific fastener. Refer to manufacturer's equipment operation instructions for pilot hole sizes.
2.2.9
Precaution In drilling titanium, it is important to maintain correct drill speed and to keep the drill cutting once it has started.
2.3
PRODUCT REQUIREMENTS
2.3.1
Magnifying Glass Inspection Inspect (using a 10X magnifying glass) and disposition dimples and dimpled parts with reference to illustrations in Figure I.
2.3.2
Dimensional Control Dimensional requirements of finished dimples including the hole size shall be governed by the requirements for the particular fastener for which the dimple was made.
2.3.3
Flushness Tolerance on rivet flushness shall be in accordance with normal manufacturing practices.
2.3.4
Nesting of Single Sheet Dimpling Single sheet dimpled recesses must be so formed that any number of dimples will nest into other dimples or countersunk holes of the same size. A maximum gap between sheets of .015 inch, but not more than 25 percent of the outer sheet thickness, is permissible after dimpling.
3.0
PROCEDURE REQUIREMENTS
3.1
Machine Settings For dimpling machine setup instructions, refer to the manufacturer's operational handbooks applicable to the type of hot dimpling machine being operated and the dimpled material.
TB 206L-07-226-RA Page 34 of 44 Export Classification C, ECCN EAR99 Approved for public release.
4.0
PROCESS CONTROL REQUIREMENTS
4.1
SPECIFIC CONTROLS
4.1.1
Dimpling Machine Calibration Pressure, gauges, dwell times, and temperature indicators shall be calibrated periodically in accordance with ISO 10012-1 or ANSI/NCSL Z540-1.
4.1.2
Dimpling Control Log A dimpling control log shall be maintained for each dimpling machine. This log shall record the part number and quantity of parts dimpled, the material condition, and the thickness, the date dimpled, the machine operators name and the inspectors symbol and disposition of the parts. The approved machine setting required to be used for each applicable material, material condition, thickness and fastener shall be posted at each dimpling machine.
4.1.3
Process Control Panel For cold and hot dimpling processes, a test panel or panels shall be dimpled, inspected and tested, whenever the machine settings or alloy or material condition or thickness are changed.
4.1.3.1
Process Control Test Panel Configuration The test panel or panels shall be of the same material, heat treat condition and thickness and have the same pilot hole as the material being dimpled. Size of panel or panels shall be one (1) inch in width and of sufficient length to accommodate not less than a total of 10 dimples spaced approximately one (1) inch increments.
TB 206L-07-226-RA Page 35 of 44 Export Classification C, ECCN EAR99 Approved for public release.
4.1.3.2
Routine Process Control Panel Test The dimpled test strip shall be physically inspected for dimple definition, ram flat, gouges, and convexity in accordance with Figure I, see paragraph 2.3.1. In addition, dimpled test strips shall be fluorescent penetrant inspected for cracks in accordance with Figure I. Should the test dimples prove unsatisfactory the machine operator shall adjust the machine settings until satisfactory dimples are obtained. One half of the dimples shall be used in the breaking test using the procedure and criteria of Figure II. The balance of the dimples shall be used for the pry test. Of these dimples the inspector shall pry test (See Figure III) to failure at least three (3) dimples, leaving two (2) or more dimples untested. If the pry test reveals any unsatisfactory dimples, it shall be considered cause for repeating the test. If the second test fails, the machine shall be shut down until the source of trouble can be found and corrected. In the event of pry test failure, the remaining dimples shall be submitted to a Metallurgical Laboratory where they will be sectioned, polished, etched, and examined Metallographically at 100 magnification.
4.1.4
Inspection All cold and hot dimpled parts shall receive one hundred percent (100%) inspection per paragraph 2-3-1. Each individual dimple shall be physically inspected. Aluminum parts dimpled with primed surfaces shall be inspected after dimpling operation to ensure primer has not cracked and/or peeled. Primer shall be locally removed as required and all bare metal surfaces reprimed.
4.2
PRODUCT ASSURANCE The Product Assurance Department shall assure application of process controls and additional controls as may be necessary for compliance with this process sheet.
TB 206L-07-226-RA Page 36 of 44 Export Classification C, ECCN EAR99 Approved for public release.
TABLE I DIMPLING REQUIREMENTS Under Sheet .016 .020 .025 .032 .040 .051 .064 .072 .081 .090 .102 .125 Under Sheet .016 .020 .025 .032 .040 .051 .064 .072 .081 .090 .102 .125
Top Sheet .016 Rivet Diameter 1/16 3/32 1/8 5/32 3/16 1/4
Top Sheet .020 Rivet Diameter 1/16 3/32 1/8 5/32 3/16 1/4
Top Sheet .025 Rivet Diameter 1/16 3/32 1/8 5/32 3/16 1/4
1
1
1
1
1
1
1
1
1
1
1
1
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
3
1
1
1
1
1
2
1
1
1
1
1
2
1
1
1
1
1
3
1
1
1
1
1
2
2
1
1
1
1
2
2
1
1
1
1
3
2
1
1
1
1
2
2
2
1
1
1
2
2
2
1
1
1
3
2
2
1
1
1
2
2
2
2
4
4
2
2
2
2
4
4
3
2
2
2
4
4
2
2
2
2
4
4
2
2
2
2
4
4
3
2
2
2
4
4
2
2
2
2
2
4
2
2
2
2
2
4
3
2
2
2
2
4
2
2
2
2
2
2
2
2
2
2
2
2
3
2
2
2
2
4
2
2
2
2
2
2
2
2
2
2
2
2
3
2
2
2
2
2
Top Sheet .032 Rivet Diameter 1/16 3/32 1/8 5/32 3/16 1/4
Top Sheet .040 Rivet Diameter 1/16 3/32 1/8 5/32 3/16 1/4
Top Sheet .051 Rivet Diameter 1/16 3/32 1/8 5/32 3/16 1/4
3
1
1
1
1
1
3
3
1
1
1
1
3
3
3
1
1
1
3
1
1
1
1
1
3
3
1
1
1
1
3
3
3
1
1
1
3
1
1
1
1
1
3
3
1
1
1
1
3
3
3
1
1
1
3
1
1
1
1
1
3
3
1
1
1
1
3
3
3
1
1
1
3
1
1
1
1
1
3
3
1
1
1
1
3
3
3
1
1
1
3
1
1
1
1
1
3
3
1
1
1
1
3
3
3
1
1
1
3
2
2
1
1
1
3
3
2
1
1
1
3
3
3
1
1
1
3
2
2
2
4
4
3
3
2
4
4
4
3
3
3
4
4
4
3
2
2
2
4
4
3
3
2
2
4
4
3
3
3
2
4
4
3
2
2
2
2
4
3
3
2
2
4
4
3
3
3
2
4
4
3
2
2
2
2
4
3
3
2
2
2
4
3
3
3
2
2
4
3
2
2
2
2
2
3
3
2
2
2
4
3
3
3
2
2
4
TB 206L-07-226-RA Page 37 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Under Sheet .016 .020 .025 .032 .040 .051 .064 .072 .081 .090 .102 .125
Top Sheet .064 Rivet Diameter 1/16 3/32 1/8 5/32 3/16 1/4
Top Sheet .072 Rivet Diameter 1/16 3/32 1/8 5/32 3/16 1/4
3
3
3
3
1
1
3
3
3
3
3
4
3
3
3
3
1
1
3
3
3
3
3
4
3
3
3
3
1
1
3
3
3
3
3
4
3
3
3
3
1
1
3
3
3
3
3
4
3
3
3
3
1
1
3
3
3
3
3
4
3
3
3
3
1
1
3
3
3
3
3
4
3
3
3
3
1
1
3
3
3
3
3
4
3
3
3
3
4
4
3
3
3
3
3
4
3
3
3
3
4
4
3
3
3
3
3
4
3
3
3
3
4
4
3
3
3
3
3
4
3
3
3
3
2
4
3
3
3
3
3
4
3
3
3
3
2
2
3
3
3
3
3
4
1
Dimple all sheets
2
Dimple top sheet Countersink under sheet
3
Countersink top sheet only
4
Do not use. Contact Product Support Engineering for assistance.
TB 206L-07-226-RA Page 38 of 44 Export Classification C, ECCN EAR99 Approved for public release.
TABLE II REQUIREMENTS FOR APPLICATION OF HOT OR COLD DIMPLING Material
Alloy
Aluminum
2000 Series 6000 Series 7000 Series
Magnesium Titanium CRES
Low Alloy Steel
All Commercially Pure 300 series All Precipitation Hardening Alloys (15-7,1t-7,17-4,455) All
Heat Treat Condition O,T3(x) or T4(x) T6(x), T8(x) O or T4 T6 O T6(x),T7(x) All Annealed A, 1/4H, 1/2H Annealed All Others
Method of Dimpling
A or N Hardened
Optional Hot
TB 206L-07-226-RA Page 39 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Cold Hot Optional Hot Optional Hot Hot Hot Optional Optional Hot
CONDITION
ACCEPTABLE LIMITS AND PROBABLE CAUSE Acceptable - Good ram pressure. No scratches or marks on dimple surface. No cracks. Good definition. For single sheet dimpling the diameter of ram flat should be equal to the diameter of the ram itself.
A
Correct Dimple
B
Circumferential Crack
Not Acceptable - Insufficient heat in the sheet. Sheet re-dimpled in reverse direction to original. This type of crack is more apt to appear in thin sheet dimpled for large fasteners.
C
Cracks in Dimple Flare
Not Acceptable - Dies not properly heated. Insufficient ram pressure. Inner rams cracked. Pilot holes too small. This type of crack is more apt to appear in thin sheet dimpled for large fasteners, particularly the screws.
D
Ram Flat Too Small
E
Ringed Ram Flat
Not Acceptable - Insufficient ram pressure. Use of insufficient ram pressure will contribute to radial cracking, circumferential tension cracking and some types of internal defects. Re-striking the dimple will not correct these faults. Acceptable - However excessive ram pressure. Inner ram worn.
FIGURE I – ACCEPTANCE LIMITS FOR DIMPLES
TB 206L-07-226-RA Page 40 of 44 Export Classification C, ECCN EAR99 Approved for public release.
CONDITION
ACCEPTABLE LIMITS ANDPROBABLE CAUSE Not Acceptable - Insufficient heat in the sheet. Dimple formed too fast (Speed of operation valve open, etc.) Re-dimpled to reverse a dimple. See Figure II on how to detect these cracks. Acceptable - Scratches or marks usually indicate scored punches or dies, or foreign matter on tools. Tools shall be kept as clean as possible to avoid this condition. Tools shall be replaced if marks caused by dirty or defective tools.
F
Internal Circumferential Tension Cracks
G
Marks on Dimple
H
Ringed Dimple
I
Convex Sheet Dimpling)
(Due
to Not Acceptable - Dimpling pressure to be adjusted.
J
Concave Dimpling)
(Due
to Not Acceptable adjusted.
Acceptable - However excessive dimpling pressure.
Sheet
Dimpling pressure to be
FIGURE I – ACCEPTANCE LIMITS FOR DIMPLES (Cont’d)
TB 206L-07-226-RA Page 41 of 44 Export Classification C, ECCN EAR99 Approved for public release.
TB 206L-07-226-RA Page 42 of 44 Export Classification C, ECCN EAR99 Approved for public release.
FIGURE III - PRY TESTING A DIMPLE INTERNAL CIRCUMFERENTIAL SHEAR CRACKS
Punches used for pry checking should be of the same nominal diameter as the fastener for which the dimple is made. Prying may be done from either side, however, care shall be taken to see that the end of the punch protrudes through the dimple sufficiently so that the dimple is not cut through by the end of the punch. In addition, the tapered part of the punch should not contact the dimple. This test is designed primarily to detect internal circumferential shear cracks in the dimple (see picture above). When present, these cracks will show up during the pry test as follows: a. Break out of complete dimple washer as pictured. b. Clean break out of a segment of a dimple washer with break in the internal circumferential shear area.
-NOTEIn the drawing above that internal circumferential shear cracks do not start at the sharp radius at the junction of the dimple cone and the sheet but slightly down on the dimple cone.
TB 206L-07-226-RA Page 43 of 44 Export Classification C, ECCN EAR99 Approved for public release.
Failures of the above type denote unsatisfactory dimples and shall cause the machine to be shut down until the cause can be found and corrected. Good dimples will normally fail radially during the pry test. However, occasionally the failure will start circumferentially in the area at the sharp radius at the juncture of the dimple cone and the sheet but these cracks should not progress circumferentially around the dimple. This failure is not indicative of internal circumferential shear cracks and shall not be cause for rejection of the dimple. If, during pry testing, several dimples fail initially by radial cracking, but upon reacting the internal circumferential shear area the failure turns into an internal circumferential shear failure, some of the dimples shall be removed from the panel and examined metallurgically.
TB 206L-07-226-RA Page 44 of 44 Export Classification C, ECCN EAR99 Approved for public release.
