AD 2021-10-16
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky | Aircraft Corporation | Airworthiness Directives; Carson Helicopters, Inc.; Croman Corporation; Sikorsky Aircraft Corporation; and Siller Helicopters |
Unsafe Condition
The left and right input freewheel unit (IFWU) assemblies on certain main gearboxes may slip or disengage, resulting in both engines overspeeding, engine shutdowns, and loss of engine power to the transmissions.
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Required Actions
Create a component history card or equivalent record and record the hours time-in-service (TIS) and external lift cycles for each affected main gearbox left and right IFWU assembly. Determine if the IFWU assembly is a repetitive external lift (REL) or non-REL IFWU assembly. For REL IFWU assemblies, perform repetitive inspections, replace affected parts with an airworthy part, and permanently mark the REL IFWU camshafts and gear housings with the letters 'REL' on the surface of these parts.
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Compliance Time
Within 50 flight hours
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Affected Aircraft
All Carson Helicopters, Inc., Model S-61L and SH-3H helicopters; Croman Corporation Model SH-3H helicopters; Sikorsky Aircraft Corporation Model S-61A, S-61D, S-61E, and S-61V helicopters; and Siller Helicopters Model CH-3E and SH-3A helicopters.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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