AD 52-12-01
final rule
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Aero Spacelines Incorporated | 377 | BOEING Model 377 Aircraft |
| aircraft | Aero Spacelines Incorporated | 377MG | BOEING Model 377 Aircraft |
| aircraft | Aero Spacelines Incorporated | 377SGT | BOEING Model 377 Aircraft |
Unsafe Condition
Overheating of the freon compressor motors could result in fire.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Replace magnesium parts with aluminum parts (P/N P14A9709 to P35A9046, P14A9712 to P35A9044, A14B3724 to P35A9042) or install a temperature sensing switch actuating at 100 degrees or less with associated circuits and equipment. Alternatively, operate the aircraft with refrigeration systems inoperative.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Before any installation of overhauled or new compressor motor after October 1, 1952 (for item A) or prior to October 1, 1952 (for item B).
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Aero Spacelines Incorporated Model 377, 377MG, 377SGT aircraft.
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Federal Register Abstract
Compressor Motors
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_52-12-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 52-12-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: BOEING Model 377 Aircraft Subject: Compressor Motors Status: Current Citation: This information is not available. Citation Publish Date: 12/04/1956 Effective Date: Make: Aero Spacelines Incorporated Model: 377 | 377MG | 377SGT Product Type: Aircraft Product Subtype: Large Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: AIR-700: Compliance & Airworthiness Division Office of Primary Responsibility: AIR-720: Operational Safety Branch CFR Part Reference: Part 39 Comments: Unable to find issue date AIRWORTHINESS DIRECTIVES FINAL RULES: 52-12-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 52-12-01 SUBJECT HEADING: BOEING Model 377 Aircraft ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 52-12-01 BOEING: Applies to all Model 377 Aircraft. Compliance required as specified below. In order to reduce the hazard of fire resulting from overheating of the freon compressor motors, compliance with the following is required: A. Compliance required before any installation of overhauled or new compressor motor after October 1, 1952. (Not required if item B accomplished or airplane operated in accordance item C.) Replace the following Westinghouse compressor motor magnesium parts with corresponding aluminum parts: . . . . . . . . . . . . . . . . . P/N (Mg.) P/N (AL.) Inlet Cooling Cap P14A9709 P35A9046 Front Bearing Bracket P14A9712 P35A9044 Fan A14B3724 P35A9042 B. Compliance required prior to October 1, 1952. (Not required if both motors previously modified in accordance item A or if airplane operated in accordance item C.) Install a temperature sensing switch, adjusted to actuate at 100 degrees or less, in the cooling air outlet of each freon compressor motor. Install circuits and equipment so that this overheat switch, as well as the motor thermoguard switch, will illuminate a cockpit warning light or will open the compressor motor power circuit, or both. C. In the event the modifications outlined in A or B are not completed in accordance with the above requirements, aircraft may be operated with the refrigeration systems made inoperative. FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_52-12-01.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 52-12-01 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: BOEING Model 377 Aircraft Subject: Compressor Motors Status: Current Citation: This information is not available. Citation Publish Date: 12/04/1956 Effective Date: Make: Aero Spacelines Incorporated Model: 377 | 377MG | 377SGT Product Type: Aircraft Product Subtype: Large Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: AIR-700: Compliance & Airworthiness Division Office of Primary Responsibility: AIR-720: Operational Safety Branch CFR Part Reference: Part 39 Comments: Unable to find issue date AIRWORTHINESS DIRECTIVES FINAL RULES: 52-12-01 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 52-12-01 SUBJECT HEADING: BOEING Model 377 Aircraft ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 52-12-01 BOEING: Applies to all Model 377 Aircraft. Compliance required as specified below. In order to reduce the hazard of fire resulting from overheating of the freon compressor motors, compliance with the following is required: A. Compliance required before any installation of overhauled or new compressor motor after October 1, 1952. (Not required if item B accomplished or airplane operated in accordance item C.) Replace the following Westinghouse compressor motor magnesium parts with corresponding aluminum parts: . . . . . . . . . . . . . . . . . P/N (Mg.) P/N (AL.) Inlet Cooling Cap P14A9709 P35A9046 Front Bearing Bracket P14A9712 P35A9044 Fan A14B3724 P35A9042 B. Compliance required prior to October 1, 1952. (Not required if both motors previously modified in accordance item A or if airplane operated in accordance item C.) Install a temperature sensing switch, adjusted to actuate at 100 degrees or less, in the cooling air outlet of each freon compressor motor. Install circuits and equipment so that this overheat switch, as well as the motor thermoguard switch, will illuminate a cockpit warning light or will open the compressor motor power circuit, or both. C. In the event the modifications outlined in A or B are not completed in accordance with the above requirements, aircraft may be operated with the refrigeration systems made inoperative. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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Related Airworthiness Directives
55-09-01
final ruleBOEING Model 377 Aircraft
Unsafe Condition: Loss of manual r.p.m. control can occur as a result of tripping of the fast-acting magnetic circuit breaker before the slow-acting fuse is blown on a faulted branch.
