AD 91-12-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-61A | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-61 Series Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61D | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-61 Series Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61E | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-61 Series Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61L | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-61 Series Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61N | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-61 Series Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61NM | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-61 Series Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61R | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-61 Series Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61V | Airworthiness Directives; SIKORSKY AIRCRAFT Model S-61 Series Helicopters |
Unsafe Condition
Failure of a main rotor blade spindle due to improper application of sealing compound between the spacer and spindle assembly, which could cause loss of the main rotor blade and subsequent loss of the helicopter.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Visually inspect sleeve and spindle assemblies for sealing compound integrity using an inspection mirror and flashlight. If sealing compound is missing or defective, conduct ultrasonic inspections for cracks or flaws. Replace spindle assemblies with cracks/flaws before flight. For intact sealing compound, perform one-time ultrasonic inspection within 200 hours. Record compliance in aircraft logs.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within the next 10 hours time in service after receipt of this AD (for assemblies with 6 months/500 hours time in service since new/overhaul) or within 10 hours after reaching 6 months/500 hours time in service (for others).
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Sikorsky Model S-61A, S-61D, S-61E, S-61L, S-61N, S-61NM, S-61R, S-61V helicopters with main rotor head assemblies equipped with sleeve and spindle assemblies P/N S6110-23350-041 manufactured/overhauled before February 6, 1991.
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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