AD 47-47-05
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Martin-Marietta Corporation | 202 | Martin Model 202 Aircraft |
Unsafe Condition
Cracks at combustion chamber and heat exchanger end plates on Stewart-Warner 921-B heaters in cabin and wing systems may lead to heater failure.
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Required Actions
Inspect combustion chamber and heat exchanger end plates for cracks at specified intervals. Replace heaters showing impending failure. Conduct complete inspections and pressure tests every 300/600 hours (cabin/wing) and repeat at shorter intervals post-initial inspection.
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Compliance Time
Inspections must be conducted before further flight as per the specified intervals: cabin heaters at each 30 hours, wing heaters at each 60 hours. Complete inspections every 300/600 hours (cabin/wing), then every 100/200 hours thereafter.
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Affected Aircraft
Martin-Marietta Corporation Model 202 Aircraft with Stewart-Warner 921-B heaters in cabin and wing systems.
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Federal Register Abstract
Stewart-Warner 921B Heaters
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_47-47-05.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 47-47-05 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Martin Model 202 Aircraft Subject: Stewart-Warner 921B Heaters Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Martin-Marietta Corporation Model: 202 Product Type: Aircraft Product Subtype: Large Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 47-47-05 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 47-47-05 SUBJECT HEADING: Martin Model 202 Aircraft ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 47-47-05 MARTIN: (Was Service Note 1 of AD-795-1.) Applies to Model 202 Aircraft. The Stewart-Warner 921-B heaters in the Cabin heating and wing thermal deicing systems shall be inspected in accordance with the following: Any heaters indicating impending failure as a result of these inspections shall be replaced immediately: 1. Inspect combustion chamber and heat exchanger end plates on each end of the cabin heaters for signs of cracks at each 30 hours of airplane operation. For wing heaters this inspection should be conducted at each 60 hours of airplane operation. 2. Remove cabin heater for complete inspection and pressure test every 300 hours of airplane operation. In the case of wing heaters this inspection should be conducted at not less than every 600 hours of airplane operation. 3. Item 2. is to be repeated every 100 hours of airplane operation after the first 300- hour inspection for cabin heaters and every 200 hours of operation after the first 600-hour inspection in the case of wing heaters. NOTE: The above inspection periods may be varied within reasonable limits to suit the normal inspection periods of scheduled air carrier operators at the discretion of the assigned CAA Maintenance Inspector. If heater operating time is logged separately from airplane operating time, the inspections specified in 2. and 3. may be conducted on the basis of heater operating time except that, if this is done, both wing and cabin heaters should be inspected after the first 300 hours and each 100 hours thereafter. FOOTER:
Document Text
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AD Final Rules - DRS_47-47-05.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 47-47-05 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Martin Model 202 Aircraft Subject: Stewart-Warner 921B Heaters Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: Make: Martin-Marietta Corporation Model: 202 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: 47-47-05 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: AD NUMBER: 47-47-05 SUBJECT HEADING: Martin Model 202 Aircraft ACTION: SUMMARY: DATES: ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 47-47-05 MARTIN: (Was Service Note 1 of AD-795-1.) Applies to Model 202 Aircraft. The Stewart-Warner 921-B heaters in the Cabin heating and wing thermal deicing systems shall be inspected in accordance with the following: Any heaters indicating impending failure as a result of these inspections shall be replaced immediately: 1. Inspect combustion chamber and heat exchanger end plates on each end of the cabin heaters for signs of cracks at each 30 hours of airplane operation. For wing heaters this inspection should be conducted at each 60 hours of airplane operation. 2. Remove cabin heater for complete inspection and pressure test every 300 hours of airplane operation. In the case of wing heaters this inspection should be conducted at not less than every 600 hours of airplane operation. 3. Item 2. is to be repeated every 100 hours of airplane operation after the first 300- hour inspection for cabin heaters and every 200 hours of operation after the first 600-hour inspection in the case of wing heaters. NOTE: The above inspection periods may be varied within reasonable limits to suit the normal inspection periods of scheduled air carrier operators at the discretion of the assigned CAA Maintenance Inspector. If heater operating time is logged separately from airplane operating time, the inspections specified in 2. and 3. may be conducted on the basis of heater operating time except that, if this is done, both wing and cabin heaters should be inspected after the first 300 hours and each 100 hours thereafter. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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