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SERVICE DIRECTIVE BULLETIN
DATE:
1.
SUBJECT:
2.
MODEL:
3.
EFFECTIVITY:
4.
BACKGROUND:
At the time of the initial release of this Service Directive Bulletin (SDB), Enstrom
discovered that some flex packs (ECD4024-1) used in the main rotor drive system do not
meet the required specifications. A flex pack consists of eight stacked elements (or plates)
designed to permit flexing of the drive system shaft. The sub-standard flex packs contained
only six elements.
This SDB requires a one time inspection of the two flex packs for the required eight
elements.
Technical aspects of this SDB were coordinated with the FAA at the time of the original
issue in 2009.
Revision 1 removed a reference to SDB T-017 (data is presented in WAD T-001 Revision
1), updated paragraph 6, Special Tools List, and updated the nomenclature for the text
pertaining to ECD4024-1.
5.
COMPLIANCE:
Within ten hours, inspect the flex packs in accordance with paragraph 5.1 to determine if
they have the correct number of elements.
Any flex packs with fewer than eight elements must be replaced prior to the next flight in
accordance with paragraph 5.2.
5.1
PLATE INSPECTION:
December 12, 2023
Drive System Flex Packs
TH-28, 480, and 480B
All Serial Numbers
Perform all maintenance IAW the TH-28/480 Series
Maintenance Manual.
SERVICE DIRECTIVE BULLETIN NO. T-036
NOTE
Page 1 of 5
Revision 1
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Related Manuals for ENSTROM T-0139-1
Summary of Contents for ENSTROM T-0139-1
- Page 1 All Serial Numbers BACKGROUND: At the time of the initial release of this Service Directive Bulletin (SDB), Enstrom discovered that some flex packs (ECD4024-1) used in the main rotor drive system do not meet the required specifications. A flex pack consists of eight stacked elements (or plates) designed to permit flexing of the drive system shaft.
- Page 2 If there are eight elements per flex pack, no further action is required. If a flex pack contains fewer than eight elements, the flex pack must be removed and replaced in accordance with paragraph 5.2. Contact Enstrom Product Support with the results of the flex pack inspections. 5.2. REPLACEMENT:...
- Page 3 SERVICE DIRECTIVE BULLETIN NO. T-036 December 12, 2023 Revision 1 Replace the flex pack(s) with a set of eight elements IAW TH-28/480 Series Maintenace Manual paragraphs 11-19 and 11-20. If the aft flex pack is replaced, the lower pulley assembly must be removed from the aircraft. CAUTION Ensure that the three spacers used on each side of the flex pack (forward side or aft side) are of equal thickness.
-
Page 4: Special Tools
Replacement - 3 hours if the lower pulley assembly is not removed; up to 16 hours if the lower pulley assembly is removed. WARRANTY: Per Enstrom Helicopter Warranty policy. (Note, the original flex packs must be returned for warranty.) WEIGHT CHANGE:... - Page 5 SERVICE DIRECTIVE BULLETIN NO. T-036 December 12, 2023 Revision 1 Drive System Assy Flex Pack (ECD4024-1) Lower Pulley Lower Pulley Assy Flex Pack (ECD4024-1) Figure 1. Page 5 of 5...
- Page 6 Work Aid Document: T-001 December 12, 2023 Revision 1 Aligning the TH-28/480 Series Lower Drive System 1. Purpose: The purpose of this document is to provide additional reference information for aligning the lower drive system in the TH-28/480 Series helicopters. Use this document as additional reference information for the TH-28/480 Series Maintenance Manual instructions.
- Page 7 Work Aid Document: T-001 December 12, 2023 Revision 1 4. Power Output Shaft to Lower Pulley Drive Shaft Alignment (Refer to paragraph 11-17,C): 1. The lower pulley system is a pendulum and movement is in an arc. 2. Acceptable alignment is achieved when the bolt can be threaded into the power output shaft flange using finger pressure (See Figures 5 and 6).
- Page 8 Work Aid Document: T-001 December 12, 2023 Revision 1 4. Adjust the position of the blower shroud as required after completing the oil cooler blower shaft alignment. 6. Lower Drive System Reassembly (Refer to paragraph 11-17,E): 1. Reassembly the lower pulley aft coupling using .250 inch spacers, P/N 4130521-25, between the flex pack and the flanges of the hub and the pulley shaft (See Figure 17).
- Page 9 Work Aid Document: T-001 December 12, 2023 Revision 1 Figure 2 - Lower Pulley Tie Rods Figure 3 - Alignment Tool at Upper Pulley Page 4 of 12...
- Page 10 Work Aid Document: T-001 December 12, 2023 Revision 1 Figure 4 - Alignment Tool at Lower Pulley Figure 5 - Engine to Lower Pulley Alignment (Engine Low) Page 5 of 12...
- Page 11 Work Aid Document: T-001 December 12, 2023 Revision 1 Figure 6 – Engine to Lower Pulley Alignment (Aligned) Figure 7 - Engine Bi-Pod Mount Page 6 of 12...
- Page 12 Work Aid Document: T-001 December 12, 2023 Revision 1 Figure 8 - Engine Tri-Pod Mount Figure 9 - Engine Upper Mount Page 7 of 12...
- Page 13 Work Aid Document: T-001 December 12, 2023 Revision 1 Figure 10 - Flange Position for Lateral and Axial Alignment Check Figure 11 - Lateral Alignment (Aligned) Page 8 of 12...
- Page 14 Work Aid Document: T-001 December 12, 2023 Revision 1 Figure 12 - Intermediate Shaft Installed with T-0166-11, Alignment Spacer Notes: 1. Make from steel or aluminum. 2. Break all sharp edges. Figure 13 - T-0166-11, Alignment Spacer Page 9 of 12...
- Page 15 Work Aid Document: T-001 December 12, 2023 Revision 1 (Note vertical misalignment) Figure 14 - Oil Cooler Blower Forward Mount Figure 15 - Oil Cooler Blower Aft Mount Page 10 of 12...
- Page 16 Work Aid Document: T-001 December 12, 2023 Revision 1 Figure 16 - Oil Cooler Blower Shaft Vertically Aligned Figure 17 - Aft Coupling Normal Installation Page 11 of 12...
- Page 17 Work Aid Document: T-001 December 12, 2023 Revision 1 Figure 18 - Elongation Limits of Oil Cooler Bearing Housing Supports Page 12 of 12...
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