AD 55-15-06
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Lockheed Aircraft Corporation | 1049C-55 | LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft |
| aircraft | Lockheed Aircraft Corporation | 1049D-55 | LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft |
| aircraft | Lockheed Aircraft Corporation | 1049E-55 | LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft |
| aircraft | Lockheed Aircraft Corporation | 149-46 | LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft |
| aircraft | Lockheed Aircraft Corporation | 49-46 | LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft |
| aircraft | Lockheed Aircraft Corporation | 649-79 | LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft |
| aircraft | Lockheed Aircraft Corporation | 649A-79 | LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft |
| aircraft | Lockheed Aircraft Corporation | 749-79 | LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft |
| aircraft | Lockheed Aircraft Corporation | 749A-79 | LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft |
Unsafe Condition
The cooling air system's aluminum duct between the oil cooler scoop and the shutoff valve in zone 1 creates a possible zone 1 to zone 2 firepath, compromising fire-resistance integrity.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Install a shutoff valve in a fireproof duct for Models 049/149 and 649/749 aircraft. Replace the aluminum duct with a fireproof duct between the oil cooler scoop and existing shutoff valve for Models 1049C and E aircraft.
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Compliance Time
April 1, 1956, for Model 1049 aircraft and October 1, 1956, for Models 049/149 and 649/749 aircraft.
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Affected Aircraft
Lockheed Models 049, 149, 649-749, 1049C, 1049D, and 1049E aircraft with specific serial numbers as listed in the AD: 049/149 serials 1963-1980, 2021-2088; 649-749 serials 2503-2590, 2610, 2611, 2614-2618; 1049C serials 4501-4548; 1049E serials 4549-4555, 4558, 4559, 4563-4565; 1049D serials 4163-4166.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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