ALERT SERVICE BULLETIN 427-21-44

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ASB 427-21-44-RA Page 1 of 7 Approved for public release. ALERT SERVICE BULLETIN 427-21-44 15 February 2021 Revision A, 6 April 2021 MODEL AFFECTED: 427 SUBJECT: TRANSMISSION OIL CHECK VALVE 209-062-520- 001, INSPECTION AND REPLACEMENT OF. HELICOPTERS AFFECTED: Serial numbers 56001 through 56084, 58001, and 58002. COMPLIANCE: Part I: Within the next 25 flight hours or 30 days, whichever comes first after the release date of this bulletin. Part II: Within the next 25 flight hours or 30 days, whichever comes first after accomplishment of Part I and every 25 flight hours or 30 days thereafter until Part III is accomplished. Part III: No later than 600 flight hours or 12 months, whichever comes first after accomplishment of Part I. DESCRIPTION: Bell recently received a report of a cracked transmission oil check valve manufactured by Circor Aerospace (Circle Seal). This check valve was manufactured in 2009 which is outside of the manufacturing date range (October 2011 to March 2015) addressed in Alert Service Bulletin (ASB) 427-15-37. Corrective actions implemented in 2015 by Circor Aerospace to prevent cracking of the check valve housings are indicated by the “TQL” marking. A recent check valve cracking report indicates that additional oil check valves 209-062- 520-001 manufactured by Circor Aerospace (Circle Seal) not having the “TQL” marking may be susceptible to cracking with time in service. ASB 427-21-44-RA Page 2 of 7 Approved for public release. This Alert Service Bulletin (ASB) mandates a one-time inspection of the suspected oil check valve for housing dimension measurement. Oil check valves that do not meet the inspection requirements outlined in the Part I of the Accomplishment Instructions of this bulletin will require replacement. Check valves found serviceable after accomplishment of Part I of this bulletin will not require further inspection or replacement. Alert Service Bulletin 427-15-37 mandated a one-time inspection of transmission oil check valves manufactured between October 2011 and March 2015 without the “TQL” marking. Following the release of ASB 427-15-37, Bell received reports from operators indicating that some transmission oil check valves did not have a manufacturing date stamped on the housing. Based on additional information provided by Circor Aerospace, this bulletin mandates the inspection of all transmission oil check valves manufactured by Circor Aerospace at the Corona facility in California, not having the “TQL” marking. Transmission oil check valves manufactured at the Corona facility have the “CORONA CA” marking. Regardless of the manufacturing date, transmission oil check valves with the “TQL” marking are not affected by this bulletin. Bell has been informed by Circor Aerospace that the “TQL” marking on some oil check valves manufactured after March 2015 may have been omitted. Revision A of this bulletin informs operators that the omission of the “TQL” marking does not impact the serviceability of those affected check valves and they can be used as is. The housing dimension measurement on these check valves is not required. Revision A does not change the compliance of this bulletin. Applicability of this bulletin to any spare part shall be determined prior to its installation on an affected helicopter. 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 Product Support Engineering Tel: 1-450-437-2862 / 1-800-363-8023 / productsupport@bellflight.com MANPOWER: Approximately 1 man-hour is required to accomplish Part I of this bulletin and 0.5 man- hour to accomplish Part II. Approximately 1 man-hour is required to accomplish Part III of this bulletin. This estimate is based on hands-on time and may vary with personnel and facilities available. ASB 427-21-44-RA Page 3 of 7 Approved for public release. 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 Supply Center. Part Number Nomenclature Qty (Note) 209-062-520-001 Oil check valve A/R (1) M25988/1-910 Packing A/R (1) NOTE 1: Replacement will be required only if the check valve does not meet the inspection requirements of Part I of this bulletin. SPECIAL TOOLS: None required. WEIGHT AND BALANCE: Not affected. ELECTRICAL LOAD DATA: Not affected. REFERENCES: BHT-427-MM, Maintenance Manual, Chapter 79. PUBLICATIONS AFFECTED: None affected. ACCOMPLISHMENT INSTRUCTIONS: Part I. Oil check valve inspection. 1. Prepare the helicopter for maintenance and gain access to the transmission oil check valve. The transmission oil check valve is located on the transmission oil cooler (Figure 1, Details A). ASB 427-21-44-RA Page 4 of 7 Approved for public release. -NOTE- It is not necessary to remove the transmission oil check valve for inspection; however, some clamping may require removal for better access. Regardless of the manufacturing date, any transmission oil check valves with the “TQL” marking are not affected by this bulletin. Oil check valves manufactured by other suppliers are also not affected by this bulletin. Transmission oil check valves with the “CORONA CA” marking and without the “TQL” marking are affected by this bulletin. (Figure 1, Detail B). 2. Verify if the installed check valve is affected by this bulletin. 3. If the check valve is not affected, go to step 5. 4. If the check valve is affected, proceed as follows: a. Using a caliper or equivalent, measure the check valve housing at the center and record the dimension (Figure 2). b. Measure the housing at the inlet end where the threaded fitting is installed and record the dimension. c. If the dimension measured at the inlet end is no more than 0.003 inch (0.0762