AD 73-13-08
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Cessna Aircraft Company | 421B | Airworthiness Directives; CESSNA Model 421B Airplane |
Unsafe Condition
Loss of engine oil due to insufficient retention by the crankcase breather oil separator line.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Install a check valve in the crankcase breather oil separator line following Cessna Service Letter No. ME73-10 or equivalent FAA-approved modification.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
within the next 25 hours' time in service after the effective date of this AD
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Cessna Model 421B (Serial Numbers 421B0260 through 421B0346) with AiResearch TH0871 turbochargers having serial number prefixes BC or later, or earlier serial numbers with new/ remanufactured turbochargers (prefixes BC/BCR and later).
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
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.