AD 56-26-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Lockheed Aircraft Corporation | 1049-54 | LOCKHEED Model 1049 Series Aircraft |
| aircraft | Lockheed Aircraft Corporation | 1049B-55 (Navy R7V-1) | LOCKHEED Model 1049 Series Aircraft |
| aircraft | Lockheed Aircraft Corporation | 1049C-55 | LOCKHEED Model 1049 Series Aircraft |
| aircraft | Lockheed Aircraft Corporation | 1049D-55 | LOCKHEED Model 1049 Series Aircraft |
| aircraft | Lockheed Aircraft Corporation | 1049E-55 | LOCKHEED Model 1049 Series Aircraft |
| aircraft | Lockheed Aircraft Corporation | 1049F-55 (USAF C-121C) | LOCKHEED Model 1049 Series Aircraft |
| aircraft | Lockheed Aircraft Corporation | 1049G-82 | LOCKHEED Model 1049 Series Aircraft |
| aircraft | Lockheed Aircraft Corporation | 1049H-82 | LOCKHEED Model 1049 Series Aircraft |
Unsafe Condition
The relays in the generator feeder protection main relay box are capable of overheating at high generator output, which could become excessive when one or more generators become inoperative, leading to potential complete electrical outage in the vital DC bus area.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Install a blower and replace existing interconnecting bus bars with new ones having increased cooling areas, or use an equivalent means approved by the FAA Chief, Engineering and Manufacturing Branch, Western Region.
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Compliance Time
as soon as possible but not later than the next block overhaul or major inspection period after parts become available
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Affected Aircraft
Lockheed Aircraft Corporation Model 1049 Series Aircraft, LAC Serial Numbers 4501 Through 4565, 4572 Through 4647 and 4163 Through 4166
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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