AD 74-17-07
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Enstrom Helicopter Corporation, The | F-28A | Airworthiness Directives; Enstrom Model F- 28A Helicopters |
Unsafe Condition
The main rotor gear box may experience gear tooth failure due to insufficient lubrication or material fatigue, leading to potential rotor system failure.
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Required Actions
Inspect the main rotor gearboxes by teardown and inspection at the Enstrom facility within specified timeframes based on their total time since remanufacture. Gearboxes with 100 hours or more must be inspected within 5 hours; those with less than 100 hours must be inspected before accumulating 100 hours.
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Compliance Time
within the next 5 hours
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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