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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 w hole or in part without written permission from CHI. Number: 234-62-0008 Date: 12/06/2013 Revision: 1 ATA System: Rotors

SUBJECT: Inspection of the Rotor Blade Trailing Edge Revision 1 corrects typographical errors in several compliance references.

1. Planning Information A. Effectivity:

B. Concurrent Requirements N/A C. Previous Modifications N/A D. Reason To detect dis-bonding co nditions in the trailing edg e of the ro tor blades. E. Description This service bulletin provides in structions for a visual and a detailed special coin tap inspection of the trailing edge of the rotor blades. F. Compliance Compliance with this servic e bulletin must be accomplished within 50 flight hours after receipt of this service bulletin. (1) Perform an initial inspection of the rotor blades as follows. (a) Visual inspections per Para 3.A. (b) A coin tap test per Para 3.B. (2) Recurring inspections to be performed every 500 flight hours after the initial inspection. (a) Perform general and close visual inspections per Para 3.A. (1) Aircraft Affected S/N CHI Model 234 ALL (2) Spares Affected S/N Rotor Blades Part Number 114R1702 All Dash Numbers ALLPage 2 of 4 Revision 1 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-62-0008 (b) If indications of dis-bonding are noted du ring the visual inspec tions perform a coin tap inspection per Para 3.B. (3) Perform a recurring coin tap inspection every 3000 flight hours after initial inspection per Para 3.B. (4) Perform visual and coin tap inspections on spare rotor blades per Para 3.A. and Para 3.B. prior to installation. G. Approval This service bulletin is FAA approved. H. ManpowerApproximately 1 hour and a crew of 1 is required to accomplish the visual inspection. Approximately 4 hours and a crew of 1 is required to accomplish the coin tap inspection. I. Tooling N/A J. Weight and Balance N/A K. Electrical Load Data N/A L. Software Accomplishment Summary N/A M. References 234-2 Maintenance Manual N. Publications Affected N/A O. Material Requirements N/A P. List of Components N/A 2. Definitions A. General Visual Inspection (GVI) A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made from within touching distance unless otherwise specified. A mirror may be necessary to enhance visual access to all exposed surfaces in the inspection area. This le vel of inspection is made under normally available lighting conditions such as daylight, hanga r lighting, flashlight, or drop light, and may require removal or access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked. B. Close Visual Inspection This type of inspection is detailed in nature an d accomplished using ample lighting, at no more than arm’s length, and using 10X magnification, as appropriate. C. Detailed Special Inspection – Coin Tap Method The “Coin Tap” method is a common technique/pr ocedure used for detecting voids or delaminations in thin face sheet honeycomb construction. When tapping any area, a clear, sharp ringing sound is indicative of a well-bonded solid structure, while a dull sound or thud indicates a void or delamination.Page 3 of 4 Revision 1 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-62-0008 3. Accomplishment Instructions A. Visual Inspections (1) General Visual Inspection (a) Clean the rotor blades. Refer to 234-2 Maintenance Manual , Section 12-22-00, Para. 4.F., on page 204. (b) Perform a general visual inspection of the entire rotor blade, looking for obvious defects, damage and dis-bonds by looking down the entire length of the rotor blade and paying particular attention to ripples, which may indicate a dis-bond condition. (2) Close Visual Inspection (a) Perform a close visual inspection at no more than arm’s length. Use ample lighting and 10X magnification, as necessary. (b) Angle the lighting and plane of view as necessary, such that irregularities in the surface are visible. Irregularities may indicate a dis-bond condition. (3) Report information to Colu mbia Helicopters Engineering as soon as practical, but no later than 90 days from the date of the inspection. (4) If dis-bonding is greater than the limits provided in 234-2 Maintenance Manual, Section 62-11-00, contact Columbia Helicopters Engi neering for repair assistance. Repair or replace the blade prior to further flight. B. Detailed Special Inspection – Coin Tap Method (1) Rotor blade trailin g edge dis-bonding can be identified by tapping the surface with a solid metal disk. The disk or coin should be approximately 1.5" diameter and approximately 0.10" thick. Bo nded areas will produce a shar p ringing sound, dis-bonded areas will produce a dull hollow sound. (2) Perform the coin tap inspection as follows: (a) Clean the area to be inspect ed and check the surface visually. (b) To ensure full coverage of the inspection area, the tapping pattern must be performed in both the spanwise a nd chordwise directions as follows: 1: Tap the surface approximately every 1 to 2 square inches over the entire area depicted by the gray area in Figure 1

. 2: Repeat step 1: on the underside of the blade.

Trailing Edge Inspection Area Figure 1 (c) Hold the disk between the thumb and se cond finger slightly above the center. Using the edge of the disk, tap lightly, bu t firmly, with a rhythmic speed along the trailing edge as described in step (b) wh ile lightly touching t he adjacent surface with the finger tips.Page 4 of 4 Revision 1 

### COLUMBIA HELICOPTERS INC. SERVICE BULLETIN NUMBER 234-62-0008

THIS INSPECTION REQUIRES THE OPERATOR TO DISTINGUISH CHANGES IN SOUND AND VIBRATION.

(d) Void areas will produce a change in sound and a slight vibration of the trailing edge. A void can be identified by a dull hollow sound accompanied by feeling the vibration in the trailing edg e adjacent to the void. (e) Identify any area that produces a change of sound or vibration. 1: Examine the surrounding area to determine the size of the dis-bonded area. 2: Outline the edge of the void, using a suitable marker. (f) If dis-bonding of the fairing skin and core ( Figure 2 ) is detected, refer to 234-2 Maintenance Manual , Section 62-11-00 fo r serviceability and re pair before further flight in accord ance with 234-2 Maintenance Manual , Section 62-11-30. 1: Report information to Columbia Helicopters Engineering as soon as practical, but no later than 90 days from the date of the inspection. 2: If dis-bonding is greater than the limits provided in 234-2 Maintenance Manual, Section 62-11-00 Inspection/Chec k, contact Columbia Helicopters Engineering for repair assistance. Repair or replace the blade prior to further flight. (g) If dis-bonding of the trailing edge is detected, refer to 234-2 Maintenance Manual, Section 62-11-00 for servicea bility and repair before furt her flight, in accordance with 234-2 Maintenance Manual, Section 62-11-40. 1: Report information to Columbia Helicopters Engineering as soon as practical, but no later than 90 days from the date of the inspection. 2: If dis-bonding is greater than the limits provided in 234-2 Maintenance Manual, Section 62-11-00 Inspection/Chec k, contact Columbia Helicopters Engineering for repair assistance. Repair or replace the blade prior to further flight.

Rotor Blade Trailing Edge Cross-Section Figure 2 4. Log Book Entry Upon completion of the work directed in this Servic e Bulletin, record complia nce in the aircraft log book or component records.

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