AD 97-11-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Bell Helicopter Textron, Inc. | 412 | Airworthiness Directives; Bell Helicopter Textron, Inc. Model 412 and 412EP Helicopters |
| aircraft | Bell Helicopter Textron, Inc. | 412EP | Airworthiness Directives; Bell Helicopter Textron, Inc. Model 412 and 412EP Helicopters |
Unsafe Condition
Fatigue failure of the main rotor mast and spline plate due to unanticipated high number of takeoffs and external load lifts utilizing high power settings, leading to main rotor system failure and potential loss of control.
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Required Actions
Create a component history card or equivalent record using a Retirement Index Number (RIN) system; track RIN increases based on takeoffs, external load lifts, and elevation differences; retire mast and spline plate at specified RIN limits (80,000 or 60,000) or 10,000 hours TIS, whichever comes first. Spline plates on Model 412EP must be vibro-etched and annotated.
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Compliance Time
within 100 hours time-in-service after the effective date of this AD
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Affected Aircraft
Bell Helicopter Textron, Inc. Model 412 and 412EP helicopters with main rotor masts (part numbers 412-040-101-105, -109, -117, -121, -125, -127, -129) and main rotor spline plates (part numbers 412-010-167-105 or 412-010-177-101, -105, -109, -113, -117).
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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