AD 51-15-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Wytwornia Sprzetu Komunikacyjnego | 6A4-165-B3 | FRANKLIN Model 6A4-165-B3 Engines |
Unsafe Condition
Cracks in the crankcase webbing near the main journal area and at the main bearing stud hole, which could lead to crankcase fracture and engine failure.
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Required Actions
Inspect the crankcase webbing near the main journal area for cracks. Replace crankcases with fractures or advanced cracks with P/N 18925 assembly. Inspect at 250-hour intervals if no cracks found, or 50-hour intervals if surface cracks or cracks near main bearing stud hole are detected.
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Compliance Time
by July 15, 1951. Effective on and after this date, inspections required for engines with 500 hours of operation since new or 250 hours since last overhaul.
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Affected Aircraft
Franklin Model 6A4-165-B3 Engines serial numbers 33046 and below with original crankcase assembly P/N 18553 (left half No. 18305; right half No. 18306).
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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