AD 70-12-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-55 | Airworthiness Directives; Sikorsky Models S-55, S-55B, S-55C, and S-62A Type Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-55B | Airworthiness Directives; Sikorsky Models S-55, S-55B, S-55C, and S-62A Type Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-55C | Airworthiness Directives; Sikorsky Models S-55, S-55B, S-55C, and S-62A Type Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S62A | Airworthiness Directives; Sikorsky Models S-55, S-55B, S-55C, and S-62A Type Helicopters |
Unsafe Condition
Failure of the main rotor shaft due to fatigue cracks originating from surface conditions.
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Required Actions
Inspect main rotor shaft P/N S14-35-4308-1, -2, -3, or -4 for cracks and surface conditions using Sikorsky Service Bulletin 55B35-3, 62B35-10 (dated 3 April 1970) or equivalent. Retire and replace shafts with cracks or unreworkable conditions before further flight. Rework shafts with reworkable conditions per the same service bulletins, ensuring replacement shafts are inspected if removed from the main gear box.
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Compliance Time
within the next 15 hours in service after the effective date of this AD
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Affected Aircraft
Sikorsky Models S-55, S-55B, S-55C, and S-62A Type Helicopters certificated in all categories.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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