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.
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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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Federal Register Abstract
Cooling Air System Rework
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_55-15-06.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 55-15-06 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft Subject: Cooling Air System Rework Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Lockheed Aircraft Corporation Model: 1049C-55 | 1049D-55 | 1049E-55 | 149-46 | 49-46 | 649-79 | 649A-79 | 749-79 | 749A-79 Product Type: Aircraft Product Subtype: Large Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 55-15-06 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 55-15-06 SUBJECT HEADING: LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 55-15-06 LOCKHEED: Applies to 049, 149 Aircraft, Serial Numbers 1963 Through 1980, 2021 Through 2088; 649-749 Aircraft, Serial Numbers 2503 Through 2590, 2610, 2611, 2614 Through 2618; 1049C Aircraft, Serial Numbers 4501 Through 4548; 1049E Aircraft, Serial Numbers 4549 Through 4555, 4558, 4559, and 4563 Through 4565; 1049D Aircraft, Serial Numbers 4163 Through 4166. Compliance required by April 1, 1956, for Model 1049 aircraft and October 1, 1956, for Models 049/149 and 649/749 aircraft. To improve the fire-resistance integrity of the above aircraft, revisions to the system supplying cooling air to the accessory section of the powerplant installation are considered necessary. For 049-149 aircraft and 649-749 aircraft, the revision consists of installing a shutoff valve in a fireproof duct. For the 1049C and E aircraft, the revision consists of replacing a section of aluminum duct between the oil cooler scoop, and the existing shutoff valve, with a fireproof duct. This section is in zone 1, and provides a possible zone 1 to zone 2 firepath. Lockheed Service Bulletins 49/718, for 049/149 aircraft; 1049/2384, for 1049 aircraft; and 49/391A, for 649-749 aircraft, cover these subjects. FOOTER:
Document Text
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AD Final Rules - DRS_55-15-06.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 55-15-06 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft Subject: Cooling Air System Rework Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Lockheed Aircraft Corporation Model: 1049C-55 | 1049D-55 | 1049E-55 | 149-46 | 49-46 | 649-79 | 649A-79 | 749-79 | 749A-79 Product Type: Aircraft Product Subtype: Large Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 55-15-06 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 55-15-06 SUBJECT HEADING: LOCKHEED Models 049, 149, 649-749, 1049C, 1049D, and 1049E Aircraft ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 55-15-06 LOCKHEED: Applies to 049, 149 Aircraft, Serial Numbers 1963 Through 1980, 2021 Through 2088; 649-749 Aircraft, Serial Numbers 2503 Through 2590, 2610, 2611, 2614 Through 2618; 1049C Aircraft, Serial Numbers 4501 Through 4548; 1049E Aircraft, Serial Numbers 4549 Through 4555, 4558, 4559, and 4563 Through 4565; 1049D Aircraft, Serial Numbers 4163 Through 4166. Compliance required by April 1, 1956, for Model 1049 aircraft and October 1, 1956, for Models 049/149 and 649/749 aircraft. To improve the fire-resistance integrity of the above aircraft, revisions to the system supplying cooling air to the accessory section of the powerplant installation are considered necessary. For 049-149 aircraft and 649-749 aircraft, the revision consists of installing a shutoff valve in a fireproof duct. For the 1049C and E aircraft, the revision consists of replacing a section of aluminum duct between the oil cooler scoop, and the existing shutoff valve, with a fireproof duct. This section is in zone 1, and provides a possible zone 1 to zone 2 firepath. Lockheed Service Bulletins 49/718, for 049/149 aircraft; 1049/2384, for 1049 aircraft; and 49/391A, for 649-749 aircraft, cover these subjects. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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