AD 2020-04-21
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Textron | Canada Limited | Airworthiness Directives; Bell Helicopter Textron Canada Limited Helicopters |
| aircraft | Bell | Helicopter Textron Canada Limited | Airworthiness Directives; Bell Helicopter Textron Canada Limited Helicopters |
Unsafe Condition
Disengaged teeth of a curvic coupling due to improper installation, which may result in loosening of the T/R assembly and subsequent vibration and loss of drive to the outboard T/R blades, leading to degraded directional control.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspecting the curvic coupling teeth for proper engagement with the inboard and outboard flapping bearing teeth within 10 hours TIS. If the teeth are not properly engaged, removing the T/R hub and blade assembly and inspecting the curvic coupling teeth and the inboard and outboard flapping bearing teeth for a crack, wear, mechanical damage, and corrosion. Depending on the inspection results, replacing parts. Then, with the T/R hub and blade assembly installed, performing a rigging check of the directional control system. If the teeth are properly engaged, inspecting for axial play between both the inboard and outboard T/R hub and blade assemblies. If there is axial play, performing the inspections for a crack, wear, mechanical damage, and corrosion. If there is no axial play, inspecting for play between the teeth of the curvic coupling and both the inboard and outboard flapping bearing teeth, and if play exists, performing the inspections for a crack, wear, mechanical damage, and corrosion. Lastly, emailing information about the inspection results that resulted in the replacement of parts to Bell Canada.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within 10 hours TIS
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Bell Helicopter Textron Canada Limited Model 429 helicopters, serial numbers 57001 through 57363.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 4, 2026
Rights: U.S. Government Public Domain
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