AD 90-21-09
final rule
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 747-100 Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-100B Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-100B SUD Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200B Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200C Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-200F Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747-300 Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747SP Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
| aircraft | The Boeing Company | 747SR Series | Airworthiness Directives; BOEING Model 747 Series Airplanes |
Unsafe Condition
Failure of crossover pneumatic ducts could damage air conditioning packs, wing fairing panels, and/or electrical wiring.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Conduct a penetrant inspection, proof pressure test, and re-inspection to detect cracks or ruptures of crossover ducts per Boeing SB 747-36-2078 Rev 2. Repair or replace ducts if defects are found. Stress relieve ducts as part of the inspection process. Repeat inspections and stress relief within specified flight cycles after initial inspection. Full replacement of ducts per SB terminates AD requirements.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Prior to the accumulation of 5,850 flight cycles, or within 4,000 flight cycles since last inspection and testing per SB 747-36-2078 Rev 1, or within the next 1,850 flight cycles after the AD's effective date (November 9, 1990), whichever occurs later. Subsequent actions under paragraph B must be done before 3,000 flight cycles after the initial inspection.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Boeing Model 747 series airplanes except Model 747-400, line position 002 through 707, certificated in any category.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Crossover Pneumatic Ducts
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_90-21-09.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 90-21-09 Document Type: AD Final Rules Docket Number: 90-NM-49-AD Subject Heading: Airworthiness Directives; BOEING Model 747 Series Airplanes Subject: Crossover Pneumatic Ducts Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 11/09/1990 Make: The Boeing Company Model: 747-100 Series | 747-100B Series | 747-100B SUD Series | 747-200B Series | 747-200C Series | 747-200...Show more 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: 90-21-09 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: 90-NM-49-AD AMENDMENT: 39-6756 AD NUMBER: 90-21-09 SUBJECT HEADING: Airworthiness Directives; BOEING Model 747 Series Airplanes ACTION: SUMMARY: DATES: Effective November 9, 1990. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 90-21-09 BOEING: Amendment 39-6756. Docket No. 90-NM-49-AD. Applicability: Model 747 series airplanes, except Model 747-400, line position 002 through 707, certificated in any category. Compliance: Required as indicated, unless previously accomplished. To prevent damage to air conditioning packs, wing fairing panels, and/or electrical wiring as a result of failure of crossover pneumatic ducts, accomplish the following: A. Prior to the accumulation of 5,850 flight cycles, or within 4,000 flight cycles since last inspection and testing in accordance with Boeing Service Bulletin 747-36-2078, Revision 1, dated June 15, 1989, or within the next 1,850 flight cycles after the effective date of this AD, whichever occurs later, conduct a penetrant inspection, proof pressure test, and penetrant inspection again to detect cracks or ruptures of the crossover ducts, in accordance with the Accomplishment Instructions, Items A. through F., J., and K. of Boeing Service Bulletin 747- 36-2078, Revision 2, dated August 16, 1990. If cracks or ruptures are detected, prior to further flight, repair or replace in accordance with the service bulletin. The stress relieving procedure specified in Items G., H., and I. of the service bulletin may be accomplished in conjunction with the penetrant inspection and proof pressure testing required by this paragraph, and constitutes terminating action for the requirements of paragraph B. of this AD, for all crossover pneumatic ducts. B. Prior to the accumulation of 3,000 flight cycles after accomplishment of the initial inspection required by paragraph A. of this AD, accomplish the following actions concurrently: 1. Conduct a penetrant inspection, proof pressure test, and penetrant inspection again to detect cracks or ruptures of the crossover ducts, in accordance with Items A. through F., J., and K. of the Accomplishment Instructions of Boeing Service Bulletin 747-36- 2078, Revision 2, dated August 16, 1990. If cracks or ruptures are detected, prior to further flight, repair or replace in accordance with the service bulletin. 2. Conduct stress relieving of the crossover ducts in accordance with Items G., H., and I. of the Accomplishment Instructions of Boeing Service Bulletin 747-36-2078, Revision 2, dated August 16, 1990. C. Replacement of all ducts in accordance with Boeing Service Bulletin 747-36- 2078, Revision 2, dated August 16, 1990, constitutes terminating action for the requirements of this AD. D. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region. NOTE: The request should be forwarded through an FAA Principal Inspector (PI), who will either concur or comment and then send it to the Manager, Seattle Aircraft Certification Office. E. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD. All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington 98055-4056. Amendment 39-6756, AD 90-21-09, becomes effective on November 9, 1990. FOOTER:
Document Text
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AD Final Rules - DRS_90-21-09.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 90-21-09 Document Type: AD Final Rules Docket Number: 90-NM-49-AD Subject Heading: Airworthiness Directives; BOEING Model 747 Series Airplanes Subject: Crossover Pneumatic Ducts Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 11/09/1990 Make: The Boeing Company Model: 747-100 Series | 747-100B Series | 747-100B SUD Series | 747-200B Series | 747-200C Series | 747-200...Show more 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: 90-21-09 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: 90-NM-49-AD AMENDMENT: 39-6756 AD NUMBER: 90-21-09 SUBJECT HEADING: Airworthiness Directives; BOEING Model 747 Series Airplanes ACTION: SUMMARY: DATES: Effective November 9, 1990. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 90-21-09 BOEING: Amendment 39-6756. Docket No. 90-NM-49-AD. Applicability: Model 747 series airplanes, except Model 747-400, line position 002 through 707, certificated in any category. Compliance: Required as indicated, unless previously accomplished. To prevent damage to air conditioning packs, wing fairing panels, and/or electrical wiring as a result of failure of crossover pneumatic ducts, accomplish the following: A. Prior to the accumulation of 5,850 flight cycles, or within 4,000 flight cycles since last inspection and testing in accordance with Boeing Service Bulletin 747-36-2078, Revision 1, dated June 15, 1989, or within the next 1,850 flight cycles after the effective date of this AD, whichever occurs later, conduct a penetrant inspection, proof pressure test, and penetrant inspection again to detect cracks or ruptures of the crossover ducts, in accordance with the Accomplishment Instructions, Items A. through F., J., and K. of Boeing Service Bulletin 747- 36-2078, Revision 2, dated August 16, 1990. If cracks or ruptures are detected, prior to further flight, repair or replace in accordance with the service bulletin. The stress relieving procedure specified in Items G., H., and I. of the service bulletin may be accomplished in conjunction with the penetrant inspection and proof pressure testing required by this paragraph, and constitutes terminating action for the requirements of paragraph B. of this AD, for all crossover pneumatic ducts. B. Prior to the accumulation of 3,000 flight cycles after accomplishment of the initial inspection required by paragraph A. of this AD, accomplish the following actions concurrently: 1. Conduct a penetrant inspection, proof pressure test, and penetrant inspection again to detect cracks or ruptures of the crossover ducts, in accordance with Items A. through F., J., and K. of the Accomplishment Instructions of Boeing Service Bulletin 747-36- 2078, Revision 2, dated August 16, 1990. If cracks or ruptures are detected, prior to further flight, repair or replace in accordance with the service bulletin. 2. Conduct stress relieving of the crossover ducts in accordance with Items G., H., and I. of the Accomplishment Instructions of Boeing Service Bulletin 747-36-2078, Revision 2, dated August 16, 1990. C. Replacement of all ducts in accordance with Boeing Service Bulletin 747-36- 2078, Revision 2, dated August 16, 1990, constitutes terminating action for the requirements of this AD. D. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region. NOTE: The request should be forwarded through an FAA Principal Inspector (PI), who will either concur or comment and then send it to the Manager, Seattle Aircraft Certification Office. E. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD. All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington 98055-4056. Amendment 39-6756, AD 90-21-09, becomes effective on November 9, 1990. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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