AD 98-12-30
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | MD Helicopters, Inc. | MD900 | Airworthiness Directives; McDonnell Douglas Helicopter Systems Model MD-900 Helicopters |
Unsafe Condition
Cracks in the main rotor upper hub assembly (part number 900R2101006-101 or -103) could result in failure of the hub assembly, loss of drive to the main rotor, and subsequent loss of control of the helicopter.
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Required Actions
Inspect the hub assembly for cracks using a 10-power or higher magnifying glass after removing paint from the upper mating surface. Replace the hub assembly if cracks are found. Verify attachment nut torque values and perform repetitive inspections at intervals not exceeding 150 hours time-in-service.
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Compliance Time
Before further flight for hub assemblies with 300 or more hours time-in-service (TIS); within the next 25 hours TIS for those with less than 300 hours TIS.
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Affected Aircraft
McDonnell Douglas Helicopter Systems Model MD-900 helicopters with main rotor upper hub assembly part number 900R2101006-101 or -103 installed.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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