BELL NAS9926-4L Corrosion Resistant Steel Nut Instructions
- August 31, 2024
- Bell
Table of Contents
BELL NAS9926-4L Corrosion Resistant Steel Nut
Specifications
- Model: GEN-24-54
- Revision: A, 19 August 2024
- Date: 2 July 2024
Product Information
The GEN-24-54 is a safety notice issued to all owners and operators of Bell helicopters regarding non-conforming NAS9926-4L nuts. It emphasizes the importance of measuring tare torque of self-locking fasteners and following proper attaching hardware torquing procedures.
Usage Instructions
Importance of Tare Torque Measurement
-
Before installation, measure the tare torque of self-locking fasteners using a torque wrench.
-
Attaching Hardware Torquing Procedures:
Follow the specified torquing procedures for attaching hardware as outlined in General OSN, GEN-24-53. -
Torque Check After Installation:Some components may require a torque check after installation.
Ensure that the required torque checks are completed as recommended.
FAQ
Q: What should I do if I suspect non-conforming nuts on my Bell
helicopter?
A: Contact Bell Product Support Engineering at Tel:
1-450-437-2862 /
1-800-363-8023 or email
productsupport@bellflight.com for
assistance.
OPERATION SAFETY NOTICE GEN-24-54
2 July 2024
Revision A, 19 August 2024
TO: All owners and operators of Bell helicopters
SUBJECT: NON-CONFORMING NAS9926-4L NUTS
- The original release of this General Operation Safety Notice (GEN OSN) was issued to inform owners and operators of a quality escape that may have affected some of the subject nuts manufactured by ESNA. The suspected nuts were manufactured between 2022 and prior to the original release of this OSN. There was a possibility that some nuts were not meeting the 3.5 inch-pounds (0.40 Nm) minimum tare torque requirement and that they could have been installed on delivered helicopters or sold through Bell Spares.
- Bell and the Supplier are still investigating the root cause of the non-conformity. Based on findings, it has been established that only the NAS9926-4L ESNA manufactured nuts with the marking E or EN, as shown below, are suspected. Helicopters on the production assembly line were inspected for non-conforming nuts that could have been installed.
- Revision A of this OSN is to inform owners and operators of the result of our investigation. Bell findings indicate that no component or aircraft have been delivered with non-confirming NAS9926-4L nuts. However, based on the information received from the manufacturer ESNA, and the results of our inventory verification, some NAS9926-4L nuts having a tare torque below the minimum required of 3.5 inch-pounds (0.40 Nm) may have been delivered through Bell Spares between January 2023 and March 2024. As a reminder, and as instructed in the Standard Practices Manual (BHT-
- ALL-SPM), nuts that do not meet the minimum requirement for tare torque shall not be used.
- Bell emphasizes the importance of measuring the tare torque of self-locking fasteners prior to installation. The criticality of following proper attaching hardware torquing procedures is also highlighted in the recently released General OSN, GEN-24-53.
- As a reminder, some components require a torque check after installation. It is important to ensure that the required torque checks are accomplished as recommended per the applicable Maintenance Manual (MM) Chapter 5, to ensure proper clamp up and security of attachment.
- The self-locking feature of retaining nuts is to prevent complete separation of the nut from the bolt in the event it was improperly installed with the required torque. The Maintenance Manual (MM) and Standard Practices Manual (SPM) provide guidance to help operators/maintainers to use the correct installation torque for the fasteners. The scheduled inspections for the bolted assembly ensure joint integrity throughout the operational life of the helicopter.
Note: “EN” marking indicates the manufacturer is ESNA and the letter “C”
indicates CRES material.
For any questions regarding this letter, please contact:
Bell Product Support Engineering
Tel: 1-450-437-2862 /
1-800-363-8023 /
productsupport@bellflight.com
OSN GEN-24-54RA
Approved for public release.
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