AD 86-23-51
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Columbia Helicopters, Inc. | 234 | Airworthiness Directives; BOEING VERTOL Model 234 Series Helicopters |
Unsafe Condition
Failure of the spiral bevel ring gear/sun gear bolted joint.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Remove all spiral bevel ring gears, first stage sun gears, and spacer shims with more than zero hours time in service. Install new spiral bevel ring gear, first stage sun gear (serviceable), spacer shim, and associated hardware (bolt, washer, nut).
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
before further flight
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Boeing Vertol Model 234 series helicopters with forward rotor transmission P/N's 234D1200-2, -3, -4, -5, -6 and/or aft rotor transmission P/N's 234D2200-3, -4, -5.
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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