AD 75-12-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-61L | Airworthiness Directives; Sikorsky Models S-61L, S-61N, S-61R and S-61NM Helicopters Including Military Type CH-3C, HH-3C, CH-3E, and HH-3E Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61N | Airworthiness Directives; Sikorsky Models S-61L, S-61N, S-61R and S-61NM Helicopters Including Military Type CH-3C, HH-3C, CH-3E, and HH-3E Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61NM | Airworthiness Directives; Sikorsky Models S-61L, S-61N, S-61R and S-61NM Helicopters Including Military Type CH-3C, HH-3C, CH-3E, and HH-3E Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61R | Airworthiness Directives; Sikorsky Models S-61L, S-61N, S-61R and S-61NM Helicopters Including Military Type CH-3C, HH-3C, CH-3E, and HH-3E Helicopters |
Unsafe Condition
Free counterweights or loose material in the main rotor blade spar cavity may cause blade failure.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect each main rotor blade before first flight of each day and upon noting unusual one-per-rev vibration using Sikorsky Service Bulletin S61B15-18B or FAA-approved revisions. Remove blades from service if any sound indicates free counterweights or loose material and notify Sikorsky Product Support.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Prior to the first flight of each day and before further flight if unusual vibration is noted.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Sikorsky Models S-61L, S-61N, S-61R, S-61NM helicopters including Military types CH-3C, HH-3C, CH-3E, HH-3E equipped with main rotor blades S6115-20501 (up to -9), S6115-20601 (up to -044), S6117-20101 (up to -053), or S6188-15001 (up to -044) series.
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
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.