AD 75-22-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Enstrom Helicopter Corporation, The | F-28A | Airworthiness Directives; Enstrom Model F-28A Helicopters |
Unsafe Condition
Improper machining of the tapered bore of main rotor spindle P/N 28-14282 and excessive bore depth in main rotor spindles, which may lead to spindle failure.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Within 100 hours time in service after July 1, 1976, inspect helicopters listed in Table I for improper machining using Enstrom Service Note No. 0020A or approved procedure. Identify affected spindles as life limited and replace them no later than 4,500 hours total time in service. Similarly, inspect Table II helicopters for excessive bore depth using Service Note 0021B, mark deficient spindles, and replace them by 4,500 hours.
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Compliance Time
Within the next 100 hours time in service after the effective date of this Airworthiness Directive
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Affected Aircraft
Enstrom Model F-28A helicopters with serial numbers listed in Table I and II (specific serials provided) and those receiving replacement main rotor spindles between June 18, 1974, and October 1, 1974.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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