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## Model 234 

# SERVICE BULLETIN

This document and any technical data contained is proprietary to Columbia Helicopters Incorporated (CHI)

and shall not be used, released, or disclosed, in whole or in part without written permission from CHI. Number: 234-54-0004 Date: 11/22/2013 Revision: 0 ATA System: Nacelles/Pylons
SUBJECT: Aft Pylon STA 534 and 594 Inspection
1. Planning Information A. Effectivity:

B. Concurrent Requirements None C. Previous Modifications None D. ReasonTo inspect the aft pylon structure in the areas of the STA 534 and 594 tension attachment fittings. E. Description This service bulletin provides in structions for recurring detailed special inspection of the aft pylon STA 534 and 594 structure surrounding th e tension attachment fittings above WL +72, using the dye penetrant method of inspection. F. Compliance Compliance with this service bulletin is mandatory and must be accomplished within 50 flight hours after receipt of this service bulletin; and recurring inspections performed every 100 flight hours thereafter. G. Approval This service bulletin is FAA approved. H. Manpower Approximately 6 man-hours are required to accomplish this service bulletin. I. Tooling N/A (1) Aircraft Affected S/N CHI Model 234 ALLPage 2 of 9 Revision 0 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-54-0004 J. Weight and Balance This service bulletin has no effect on weight and balance. K. Electrical Load Data N/A L. Software Accomplishment Summary N/A M. References 234-2 Maintenance Manual 234-3 Structural Repair Manual N. Publications Affected 234-2 Maintenance Manual O. Materials and Equipment Requirements

2. Detailed Special Inspection – Dye Penetrant Method WEAR APPROPRIATE PERSONAL PROTEC TIVE DEVICES AND USE ADEQUATE VENTILATION DURING THE CLEANIN G AND PAINT REMOVAL PROCESSES.
A. Requirements (1) Personnel performing this inspection must hold a current A&P certificate, or equivalent, and be familiar with the liquid penetrant inspection method. (2) Temperature limits for structure undergoing inspection: 45° to 125°F (7.2° to 51.7°C). (3) The inspection areas of interest are the areas surrounding the STA 534 and 594 forward and aft tension attachments. Refer to Figure 1 for a general overview of the inspection areas. (4) Due to physical limitations, a detailed close vi sual inspection of the outboard side of the aft STA 594 fittings shall be performed. Refer to the shaded area noted in Figure 3

. (a) This type of inspection is detailed in nature and accomplished using ample lighting, at no more than arm’s length, and using 3X or better magnification, as appropriate. A borescope may be us ed to perform this inspection. B. Aircraft Preparation (1) Prepare the aircraft for safe ground maintenance. (2) Gain access to the aft pylon upper WL +72 deck, forward and aft of STA 534 and 594. Nomenclature Part Number Quantity Acetone ASTM D329 A/R Borescope Commerc ially available 1 Cleaning solvent MIL-PRF-680 A/R Grease remover Ditz-O® DX440 (ALT for MIL-PRF-680) A/R Naphtha TT-N-97 or TT-N-95 (ALT for MIL-PRF-680) A/R Cloth, lint-free

— A/R Dye penetrant materials ASTM E 1220, using the Type II, Method C, and Nonaqueous developer 1
Paint remover Eldorado PR-3500; MIL-R-8129, or equiv. A/R Wash primer MIL-C-8514 A/R Sealant PR1422 B-1/2; AMS-S-8802, Class B A/RPage 3 of 9 Revision 0 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-54-0004 (3) Clean each set of LH and RH tension attachments and the area surrounding each attachment, using cleaning solvent. Refer to Figure 2 and Figure 3

. (4) First Inspection Only – Re move the paint and primer from the areas of interest, as depicted in Figure 2and Figure 3 , where practicable. Plus remove an additional one inch width of paint and primer extending beyond the areas of interest, where practicable. It is not necessary to remove the paint and primer from the fittings.
Inspection of the area outboard of each attachment is limited to the exposed area between the attachment and th e outboard longitudinal structure.
(a) Apply paint remover using the brush-on method. (b) Allow at least 15 minutes of co ntact time to loosen the paint. (c) Agitate the loosened paint to dislodge it. (d) Squeegee the stripper and loose paint off the surface, using a non-metallic scraper. Collect the loose paint and stripper residue in plastic sheeting. (e) Flush the area thoroughly using fresh water. REMOVE THE PAINT AND PRIMER PR IOR TO REMOVING THE FILLET SEAL TO PREVENT PAINT REMOVER FROM PENETRATING THE GAPS BETWEEN THE STATION FRAME AND THE TENSION FITTINGS. (5) First Inspection Only – Remove the fillet s ealant from around each tension fitting. Use a non-metallic scraper, cle an cloths, and cleaningsolvent or acetone. Remove the sealant only if it extends mo re than 1/4" out from the face of the fitting or it is damaged during paint and primer removal.
(6) Subsequent Inspections: (a) Remove the wash primer from the areas of interest using acetone. Refer to Figure 2and Figure 3

. (b) Remove the fillet sealant if it extends more than 1/4" out from the face of the fitting.Page 4 of 9 Revision 0 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-54-0004

General Overview of the Inspection Areas Figure 1Page 5 of 9 Revision 0 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-54-0004

STA 534 Areas of Interest Figure 2Page 6 of 9 Revision 0 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-54-0004

STA 594 Areas of Interest Figure 3Page 7 of 9 Revision 0 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-54-0004 C. Inspection Preparation (1) Clean the area of interest and one inch surrounding that area, using the penetrant cleaner/remover and clean cloths towipe the area clean. Refer to Figure 2 and Figure 3

. (2) Allow adequate time for the cleaner/remover todissolve any contaminates or organic soils. (3) Allow a minimum of 30 seconds and up to 5 minutes for the cleaner/remover to completely evaporate from the area. Wait until the area is visibly dry and then double that amount of time to allow any residual cleaner/remover to dry completely from any defects.
D. Penetrant Application (1) Spray a small amount of penetrant into a small, suitable container. (2) Apply the penetrant to the area of interest , using a cotton swab or small brush. Refer to Figure 2and Figure 3

. (3) Remove any penetrant that drips or goes in to other areas, using cleaner/remover and a clean cloth.
Care should be taken to keep excess penetrant to a minimum.
(4) Let the penetrant sit (dwe ll) on the part for 30 minutes minimum to two hours maximum. (a) Reapply penetrant as necessary to prevent drying during the dwell time. (b) Clean the penetrant and restart the process, beginning at Para 2.C.(1) , if the penetrant is allowed to dry. E. Penetrant Removal DO NOT SPRAY CLEANER/REMOVER ON THE AREA UNDERGOING INSPECTION. EXCESSIVE USE OF CLEANER/ REMOVER COULD RESULT IN AN UNDETECTED DEFECT DUE TO FLUSHING PENETRANT OUT OF THE DEFECT. (1) Wipe the penetrant from the surface in one direction only, using a clean cloth or cotton swab moistened with cleaner/remover for each wipe. (2) Use as few wipes as possible. (3) Stop the cleaning process when the surface is visibly clean. (4) Allow a minimum of 30 seconds and up to 5 minutes for the cleaner/remover to completely evaporate from the area. Wait until the area is visibly dry and then double that amount of time to allow any residual cleaner/remover to dry completely from any defects.
F. Nonaqueous Wet Developer Application (1) Shake the developer can for at least 30 seconds. The developer needs to be shaken before each use to allow for proper mixing of the developer and volatile carrier.
(2) Spray a light even coat that covers the area of interest and one inch surrounding that area. (3) Apply two or three light applications ofdeveloper, as opposed to one heavy coat. (4) Wait 15 minutes to allow all indications to fully develop prior to inspecting the area of interest.Page 8 of 9 Revision 0 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-54-0004 G. Inspection (1) Inspect the area of interest. (a) A crack may appear as a solid straight or jagged line as shown in Figure 4

. (b) A very tight crack may appear as a series of dots or an interrupted line as shown in Figure 5

. (2) Any crack indication within the area of interest is ca use for rejection. (a) Contact CHI Engineering prior to any fu rther action, if a crack indication is detected. (b) Photograph any questionable indication and forward the photograph to CHI Engineering for disposition, prior to any further action.

Example of a Solid or Jagged Line Crack Figure 4

Example of a Very Tight Crack Figure 5 H. Post-Inspection Cleaning RESIDUAL DEVELOPER ATTRACTS MOIS TURE, WHICH CAN LEAD TO CORROSION. MAKE SURE ALL RESIDUAL DEVELOPER IS REMOVED FROM THE STRUCTURE. (1) Wipe the area with a cloth saturated with water or cleaning solvent to remove residual developer from the surface. Pay partic ular attention to gaps and crevices. (2) Repeat wiping until all residual developer is removed from the surface.Page 9 of 9 Revision 0 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-54-0004 I. Inspection Completion Perform this procedure if inspection results are negative or after completing necessary repairs, as applicable. (1) Apply one coat of wash primer to t he areas where the finish was removed in Para 2.B.(4) , as directed in 234-3 Structural Repair Manual , Section 51-30-03. (2) Apply a fillet seal around each tension attach ment where it joins the surrounding structure, as directed in the 234-3 Structural Repair Manual , Section 51-45-00. Refer to Figure 6

. Sealant application is onlyrequired if the sealant was removed for the first inspection or if subseque nt inspections or repairs require re-application of sealant to give proper moisture protection.Apply the minimum amount of sealant necessary to prevent moisture penetration between the station frame and the tension attachment. Minimal application of sealant allows subsequent insp ection without removing the sealant. (3) Close up the aft pylon. (4) Restore the aircraft to an airworthy condition.

Typical Fillet Sealant Application Figure 6 3. Log Book Entry Upon completion of the work directed in this Service Bulletin, record complia nce in the aircraft log book.

Should you require any further information or have any questions, please contact: Columbia Helicopters, Inc. Engineering, at: contactengineering@colheli.com.