AD 91-08-12
final rule
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | The Boeing Company | 737-100 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-200 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-200C Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-300 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-400 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-500 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-600 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-700 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
| aircraft | The Boeing Company | 737-800 Series | Airworthiness Directives; BOEING Model 737 Series Airplanes |
Unsafe Condition
Disbonded doublers and corrosion/cracks in lap splices and stringer S-17 could cause inability to carry fail-safe loads and rapid decompression.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Perform a one-time external ultrasonic inspection within 60 calendar days after May 17, 1991. If disbonding is found, conduct HFEC and visual inspections for cracks/corrosion, repair as needed, and install oversize protruding head solid fasteners within specified flight cycles. Repeat inspections at intervals not exceeding 4,500 flight cycles or 15 months, whichever comes first. Replace blind fasteners with solid fasteners within 10,000 flight cycles.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Within 60 calendar days after the effective date of this AD (May 17, 1991) for the initial inspection. Subsequent actions must be done prior to further flight or within specified intervals (e.g., 4,500 flight cycles, 15 months, 3,000 flight cycles, 10,000 flight cycles).
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Boeing Model 737 series airplanes, line numbers 520 through 610.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Bonded Doublers Inspection
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_91-08-12.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 91-08-12 Document Type: AD Final Rules Docket Number: 90-NM-179-AD Subject Heading: Airworthiness Directives; BOEING Model 737 Series Airplanes Subject: Bonded Doublers Inspection Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 05/17/1991 Make: The Boeing Company Model: 737-100 Series | 737-200 Series | 737-200C Series | 737-300 Series | 737-400 Series | 737-500 Series...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: 91-08-12 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: 90-NM-179-AD AMENDMENT: 39-6967 AD NUMBER: 91-08-12 SUBJECT HEADING: Airworthiness Directives; BOEING Model 737 Series Airplanes ACTION: SUMMARY: DATES: Effective May 17, 1991. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 91-08-12 BOEING: Amendment 39-6967; Docket No. 90-NM-179-AD. Applicability: Model 737 series airplanes, line numbers 520 through 610, certificated in any category. Compliance: Required as indicated, unless previously accomplished. To prevent inability of the airplane to carry fail-safe loads due to disbonded doublers, and to reduce the possibility of rapid decompression, accomplish the following: A. Within 60 calendar days after the effective date of this AD, perform a one-time external ultrasonic inspection of the bonded doublers not mechanically fastened above stringer (S-) 26 between body station (BS) 259 and BS 1016 in accordance with Boeing Service Bulletin 737-53-1124, dated August 24, 1989. NOTE: The area inspected in accordance with AD 89-16-05, Amendment 39-6281, does not require reinspection for disbonding. B. If disbonding is detected, prior to further flight, accomplish the following: 1. Perform a high frequency eddy current (HFEC) inspection for cracks and a visual inspection for corrosion along the upper rivet row of the lower lap splices and both rivet rows of S-17 (if affected), for the entire length of affected panel, in accordance with Boeing Service Bulletin 737-53-1124, dated August 24, 1989. If, during the inspections required by this paragraph, paint inhibits identification of the fastener heads or cracks, the paint must be stripped using an FAA-approved chemical stripper. a. If no cracking or corrosion is found, repeat the HFEC and visual inspections at intervals not to exceed 4,500 flight cycles until the preventive modification required by paragraph C. of this AD is accomplished. b. If cracks are found, repair prior to further flight, in accordance with Boeing Service Bulletin 737-53-1124, dated August 24, 1989. Within 3,000 flight cycles following the repair, accomplish the lap splice preventive modification on the affected panel, which includes installation of oversize protruding head solid fasteners in the lap splice upper row and S-17, in accordance with Boeing Service Bulletin 737-53-1124, dated August 24, 1989. (1) Blind fasteners may be used as a temporary repair only. Repairs using blind fasteners must be repetitively inspected for loose or missing fasteners at intervals not to exceed 3,000 flight cycles following installation, and replaced with protruding head solid fasteners within 10,000 flight cycles following installation. (2) Repairs previously installed with blind fasteners prior to the effective date of this AD must be inspected for loose or missing fasteners within 1,000 flight cycles after the effective date of this AD and thereafter at intervals not to exceed 3,000 flight cycles. Blind fasteners must be replaced with protruding head solid fasteners within 10,000 flight cycles following installation. 2. Perform a detailed external visual inspection for cracks and corrosion at circumferential splices along the most forward and most aft rivet row of each panel found to contain delamination, in accordance with Boeing Service Bulletin 737-53-1076, Revision 2, dated February 8, 1990. Remove paint with an FAA-approved chemical stripper prior to inspection, or ensure that the fastener head is clearly visible. In addition to the detailed external visual inspection, perform a HFEC inspection for cracks at each circumferential splice from S-10R to S- 10L in accordance with Boeing Service Bulletin 737-53-1076, Revision 2, dated February 8, 1990, along the most forward and most aft rivet row of each circumferential splice. a. If no cracks, corrosion, or delamination are found as a result of the detailed external visual inspection, repeat the detailed external visual and HFEC inspections required by this paragraph at intervals not to exceed 4,500 landings or 15 months, whichever occurs first. b. If any cracking is detected, repair prior to further flight, in accordance with Boeing Service Bulletin 737-53-1076, Revision 2, dated February 8, 1990. c. Replacement of the most forward and most aft fastener rows with standard protruding head solid fasteners at all circumferential fuselage splices, in accordance with Boeing Service Bulletin 737-53-1076, Revision 2, dated February 8, 1990, constitutes terminating action for the inspections required by this subparagraph, B.2. 3. In areas where corrosion or delamination are found as a result of the inspections required by paragraphs B.1 and B.2. of this AD, prior to further flight, perform a low frequency eddy current (LFEC) inspection using an FAA-approved method: a. If corrosion depth, does not exceed 10% of the skin's thickness, conduct the repetitive external detailed visual inspections required by paragraphs B.1. and B.2. of this AD, of each panel found to contain corrosion at intervals not to exceed 2,250 flight cycles or 6 months, whichever occurs first. b. If corrosion depth, exceeds 10% of the skin's thickness, or if cracks or delamination is found as a result of the detailed external visual inspections, repair prior to further flight, in accordance with Boeing Service Bulletin 737-53-1076, Revision 2, dated February 8, 1990. Following such a repair, continue to inspect in accordance with paragraphs B.1. and B.2. of this AD, at intervals not to exceed 4,500 flight cycles or 15 months, whichever occurs first. c. Any crack found must be repaired, prior to further flight, in accordance with an FAA-approved method. Blind fasteners may be used as a temporary repair only. They must be repetitively inspected for loose or missing fasteners at intervals not to exceed 3,000 flight cycles following installation and then replaced with protruding head solid fasteners within 10,000 flight cycles following installation. 4. Repair all disbonded tearstraps prior to further flight, in accordance with Boeing Alert Service Bulletin 737-53A1039, Revision 4, dated April 14, 1988, or Revision 5, dated May 25, 1989; or Boeing Service Bulletin 737-53-1089, Revision 1, dated October 13, 1989; or Revision 3, dated November 2, 1989; as appropriate. C. Within 24 months after detection of disbonding as a result of the inspection required by paragraph A. of this AD, accomplish the lap splice and S-17 preventative modification of the affected panel, which includes installation of oversize protruding head solid fasteners in the upper rivet row, in accordance with Boeing Service Bulletin 737-53-1124, dated August 24, 1989. Accomplishment of this modification constitutes terminating action for the inspection requirements of paragraph B.1. and B.2 of this AD for the affected panel. D. An alternative method 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 (ACO), FAA, Transport Airplane Directorate. NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Seattle ACO. 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 information from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. This amendment (39-6967, AD 91-08-12) supersedes Amendment 39-6281, AD 89-16- 05, which became effective on September 5, 1989. This amendment (39-6967, AD 91-08-12) becomes effective on May 17, 1991. FOOTER:
Document Text
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AD Final Rules - DRS_91-08-12.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 91-08-12 Document Type: AD Final Rules Docket Number: 90-NM-179-AD Subject Heading: Airworthiness Directives; BOEING Model 737 Series Airplanes Subject: Bonded Doublers Inspection Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 05/17/1991 Make: The Boeing Company Model: 737-100 Series | 737-200 Series | 737-200C Series | 737-300 Series | 737-400 Series | 737-500 Series...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: 91-08-12 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: 90-NM-179-AD AMENDMENT: 39-6967 AD NUMBER: 91-08-12 SUBJECT HEADING: Airworthiness Directives; BOEING Model 737 Series Airplanes ACTION: SUMMARY: DATES: Effective May 17, 1991. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 91-08-12 BOEING: Amendment 39-6967; Docket No. 90-NM-179-AD. Applicability: Model 737 series airplanes, line numbers 520 through 610, certificated in any category. Compliance: Required as indicated, unless previously accomplished. To prevent inability of the airplane to carry fail-safe loads due to disbonded doublers, and to reduce the possibility of rapid decompression, accomplish the following: A. Within 60 calendar days after the effective date of this AD, perform a one-time external ultrasonic inspection of the bonded doublers not mechanically fastened above stringer (S-) 26 between body station (BS) 259 and BS 1016 in accordance with Boeing Service Bulletin 737-53-1124, dated August 24, 1989. NOTE: The area inspected in accordance with AD 89-16-05, Amendment 39-6281, does not require reinspection for disbonding. B. If disbonding is detected, prior to further flight, accomplish the following: 1. Perform a high frequency eddy current (HFEC) inspection for cracks and a visual inspection for corrosion along the upper rivet row of the lower lap splices and both rivet rows of S-17 (if affected), for the entire length of affected panel, in accordance with Boeing Service Bulletin 737-53-1124, dated August 24, 1989. If, during the inspections required by this paragraph, paint inhibits identification of the fastener heads or cracks, the paint must be stripped using an FAA-approved chemical stripper. a. If no cracking or corrosion is found, repeat the HFEC and visual inspections at intervals not to exceed 4,500 flight cycles until the preventive modification required by paragraph C. of this AD is accomplished. b. If cracks are found, repair prior to further flight, in accordance with Boeing Service Bulletin 737-53-1124, dated August 24, 1989. Within 3,000 flight cycles following the repair, accomplish the lap splice preventive modification on the affected panel, which includes installation of oversize protruding head solid fasteners in the lap splice upper row and S-17, in accordance with Boeing Service Bulletin 737-53-1124, dated August 24, 1989. (1) Blind fasteners may be used as a temporary repair only. Repairs using blind fasteners must be repetitively inspected for loose or missing fasteners at intervals not to exceed 3,000 flight cycles following installation, and replaced with protruding head solid fasteners within 10,000 flight cycles following installation. (2) Repairs previously installed with blind fasteners prior to the effective date of this AD must be inspected for loose or missing fasteners within 1,000 flight cycles after the effective date of this AD and thereafter at intervals not to exceed 3,000 flight cycles. Blind fasteners must be replaced with protruding head solid fasteners within 10,000 flight cycles following installation. 2. Perform a detailed external visual inspection for cracks and corrosion at circumferential splices along the most forward and most aft rivet row of each panel found to contain delamination, in accordance with Boeing Service Bulletin 737-53-1076, Revision 2, dated February 8, 1990. Remove paint with an FAA-approved chemical stripper prior to inspection, or ensure that the fastener head is clearly visible. In addition to the detailed external visual inspection, perform a HFEC inspection for cracks at each circumferential splice from S-10R to S- 10L in accordance with Boeing Service Bulletin 737-53-1076, Revision 2, dated February 8, 1990, along the most forward and most aft rivet row of each circumferential splice. a. If no cracks, corrosion, or delamination are found as a result of the detailed external visual inspection, repeat the detailed external visual and HFEC inspections required by this paragraph at intervals not to exceed 4,500 landings or 15 months, whichever occurs first. b. If any cracking is detected, repair prior to further flight, in accordance with Boeing Service Bulletin 737-53-1076, Revision 2, dated February 8, 1990. c. Replacement of the most forward and most aft fastener rows with standard protruding head solid fasteners at all circumferential fuselage splices, in accordance with Boeing Service Bulletin 737-53-1076, Revision 2, dated February 8, 1990, constitutes terminating action for the inspections required by this subparagraph, B.2. 3. In areas where corrosion or delamination are found as a result of the inspections required by paragraphs B.1 and B.2. of this AD, prior to further flight, perform a low frequency eddy current (LFEC) inspection using an FAA-approved method: a. If corrosion depth, does not exceed 10% of the skin's thickness, conduct the repetitive external detailed visual inspections required by paragraphs B.1. and B.2. of this AD, of each panel found to contain corrosion at intervals not to exceed 2,250 flight cycles or 6 months, whichever occurs first. b. If corrosion depth, exceeds 10% of the skin's thickness, or if cracks or delamination is found as a result of the detailed external visual inspections, repair prior to further flight, in accordance with Boeing Service Bulletin 737-53-1076, Revision 2, dated February 8, 1990. Following such a repair, continue to inspect in accordance with paragraphs B.1. and B.2. of this AD, at intervals not to exceed 4,500 flight cycles or 15 months, whichever occurs first. c. Any crack found must be repaired, prior to further flight, in accordance with an FAA-approved method. Blind fasteners may be used as a temporary repair only. They must be repetitively inspected for loose or missing fasteners at intervals not to exceed 3,000 flight cycles following installation and then replaced with protruding head solid fasteners within 10,000 flight cycles following installation. 4. Repair all disbonded tearstraps prior to further flight, in accordance with Boeing Alert Service Bulletin 737-53A1039, Revision 4, dated April 14, 1988, or Revision 5, dated May 25, 1989; or Boeing Service Bulletin 737-53-1089, Revision 1, dated October 13, 1989; or Revision 3, dated November 2, 1989; as appropriate. C. Within 24 months after detection of disbonding as a result of the inspection required by paragraph A. of this AD, accomplish the lap splice and S-17 preventative modification of the affected panel, which includes installation of oversize protruding head solid fasteners in the upper rivet row, in accordance with Boeing Service Bulletin 737-53-1124, dated August 24, 1989. Accomplishment of this modification constitutes terminating action for the inspection requirements of paragraph B.1. and B.2 of this AD for the affected panel. D. An alternative method 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 (ACO), FAA, Transport Airplane Directorate. NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Seattle ACO. 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 information from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. This amendment (39-6967, AD 91-08-12) supersedes Amendment 39-6281, AD 89-16- 05, which became effective on September 5, 1989. This amendment (39-6967, AD 91-08-12) becomes effective on May 17, 1991. FOOTER:
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Retrieved: Apr 8, 2026
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