AD 98-26-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky Aircraft Corporation | S-61A | Airworthiness Directives; Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61D | Airworthiness Directives; Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61E | Airworthiness Directives; Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61L | Airworthiness Directives; Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61N | Airworthiness Directives; Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61NM | Airworthiness Directives; Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61R | Airworthiness Directives; Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V Helicopters |
| aircraft | Sikorsky Aircraft Corporation | S-61V | Airworthiness Directives; Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V Helicopters |
Unsafe Condition
Fatigue crack in the main rotor shaft could result in shaft structural failure, loss of power to the main rotor, and subsequent loss of control of the helicopter.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Within 30 calendar days or 240 hours time-in-service after the effective date, determine if the shaft has been used in repetitive external lift (REL) operations. For shafts used in REL operations, within 1,100 hours time-in-service after the effective date, conduct a non-destructive inspection (NDI) for cracks in the shaft per the Overhaul Manual. Remove and replace any cracked shaft with an airworthy one, and mark shafts per Sikorsky ASB 61B35-68.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within the next 30 calendar days or 240 hours time-in-service after the effective date, whichever occurs first; and within 1,100 hours time-in-service after the effective date for shafts used in REL operations.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V helicopters with main rotor shaft part numbers S6135-20640-001, S6135-20640-002, or S6137-23040-001.
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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