AD 2012-27050
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Sikorsky | Aircraft Corporation | Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters |
Unsafe Condition
Presence of a protective plug inadvertently left in the intermediate gearbox (IGB) oil passages, blocking internal oil flow, leading to overheating, seizing of the IGB, failure of the tail rotor drive output shaft, loss of tail rotor drive, and subsequent loss of control of the helicopter.
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Required Actions
Before further flight, borescope inspect the IGB for any obstruction in the oil passages. As an alternative, disassemble the IGB and inspect the oil passages for any obstruction. If an obstruction is found, replace the IGB with an airworthy one before further flight.
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Compliance Time
Before further flight
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Affected Aircraft
Sikorsky Aircraft Corporation Model S-70, S-70A, S-70C, S-70C(M), and S-70C(M1) helicopters with intermediate gearbox (IGB) part numbers 70357-06300-042, 70357-06300-043, or 70357-06300-044, with 100 or less hours time-in-service since new or overhaul on October 11, 2011.
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Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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