Attention:
Owners, operators and maintainers of Bell model 429 helicopters, serial numbers 57001 to 57335, 57338, 57343 and 57346.
| File Classification No.: | Z 5000-35 |
|---|---|
| RDIMS No.: | 20766897 |
| Document No.: | CASA 2025-08 |
| Issue No.: | 01 |
| Effective Date: | 2025-06-16 |
Purpose:
The purpose of this Civil Aviation Safety Alert (CASA) is to raise awareness of a potential for accelerated wear between the cyclic and collective bellcranks and the transmission mounted bellcrank supports of Bell 429 helicopter.
Background:
Low torque values on the transmission bellcrank assembly joints were observed in production which, if not corrected, have the potential to cause increased bolt oscillatory loading, fretting and fatigue cracking of the bolt and/or bellcrank support. The bellcrank assembly was under-torqued because 40 in-lb was used as torque values instead of 40 ft-lb in some cases.
Bell has issued an Alert Service Bulletin (ASB) 429-22-58 Rev A that provides instructions for operators to inspect the transmission-mounted bellcranks and supporting structure, particularly for fretting damage in the pivoting area of the bellcrank assemblies and adjacent areas of the support, replace the affected hardware and install new hardware with the correct torque values. Additionally, the 2-year inspection procedure of flight controls (DMC-429-A-67-00-00-03A-310A-A) in the maintenance manual has been revised to include inspection of the transmission-mounted bellcranks and supports.
The following figure illustrates the transmission-mounted bellcrank assembly joint which may be undertorqued.
Figure 1. Support Installation, Cyclic and Collective Bellcranks, Transmission Mounted
Recommended action:
For Bell model 429 helicopters with serial numbers 57001 to 57335, 57338, 57343 and 57346, Transport Canada recommends that owners, operators, and maintainers carry out the inspections, part replacements and assembly using the correct torque values as described in Bell ASB 429-22-58 Rev A while performing the 2-year flight controls inspection per the latest revision of the inspection procedure DMC-429-A-67-00-00-03A-310A-A.
Contact office:
For more information concerning this issue, contact a Transport Canada Centre; or contact Varun Karthik S, Continuing Airworthiness in Ottawa, by telephone at 1-888-663-3639, or by e-mail at TC.CAWWEBFEEDBACK-retroactionWebMDLN.TC@tc.gc.ca
Original signed by
Jenny Young
Chief, Continuing Airworthiness
National Aircraft Certification
Low Torque on Transmission Mounted Bell Cranks
(PDF, 548 KB)
The Transport Canada Civil Aviation Safety Alert (CASA) is used to convey important safety information and contains recommended action items. The CASA strives to assist the aviation industry's efforts to provide a service with the highest possible degree of safety. The information contained herein is often critical and must be conveyed to the appropriate office in a timely manner. The CASA may be changed or amended should new information become available.