AD 52-12-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Lockheed Aircraft Corporation | 149-46 | LOCKHEED Models 49-46, 149-46, 649-79, 649A-79, 749-79, 749A-79, C-121A, and VC-121B Aircraft |
| aircraft | Lockheed Aircraft Corporation | 49-46 | LOCKHEED Models 49-46, 149-46, 649-79, 649A-79, 749-79, 749A-79, C-121A, and VC-121B Aircraft |
| aircraft | Lockheed Aircraft Corporation | 649-79 | LOCKHEED Models 49-46, 149-46, 649-79, 649A-79, 749-79, 749A-79, C-121A, and VC-121B Aircraft |
| aircraft | Lockheed Aircraft Corporation | 649A-79 | LOCKHEED Models 49-46, 149-46, 649-79, 649A-79, 749-79, 749A-79, C-121A, and VC-121B Aircraft |
| aircraft | Lockheed Aircraft Corporation | 749-79 | LOCKHEED Models 49-46, 149-46, 649-79, 649A-79, 749-79, 749A-79, C-121A, and VC-121B Aircraft |
| aircraft | Lockheed Aircraft Corporation | 749A-79 | LOCKHEED Models 49-46, 149-46, 649-79, 649A-79, 749-79, 749A-79, C-121A, and VC-121B Aircraft |
Unsafe Condition
Cracks in the bulkhead ring channel bend radius (P/N 283984-2, -3 and 285772-2, -3) and bracket (P/N 252886) could lead to structural failure.
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Required Actions
Inspect the bulkhead ring and bracket by August 1, 1952. If no cracks found, reinspect at 2,000-hour intervals until 8,000 total airplane hours, then at 600-hour intervals. If cracks exceed limits, repair with interim fix (bolting steel blocks) or final fix (replacing bracket with steel and adding doublers).
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Compliance Time
Compliance required as indicated.
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Affected Aircraft
Lockheed Models 49-46, 149-46, 649-79, 649A-79, 749-79, 749A-79, C-121A, and VC-121B Aircraft.
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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