AD 72-21-06
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Lycoming Engines | IGSO-540-A1A | AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines |
| engine | Lycoming Engines | IGSO-540-A1C | AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines |
| engine | Lycoming Engines | IGSO-540-A1D | AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines |
| engine | Lycoming Engines | IGSO-540-A1E | AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines |
| engine | Lycoming Engines | IGSO-540-A1F | AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines |
| engine | Lycoming Engines | IGSO-540-B1A | AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines |
| engine | Lycoming Engines | IGSO-540-B1C | AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines |
Unsafe Condition
Shifting and possible failures of the crankcase bearings due to metal contaminants in the lubrication system.
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Required Actions
Inspect the lubrication system for metal contaminants within 10 hours after the effective date and every 25 hours thereafter. Engines with metal contaminants or exceeding 500 hours must comply with (d) or (f). Engines with 1200+ hours must comply with (f) within 50 hours. Remove cylinder and examine bearing position per Service Bulletin 327B or repair crankcase per Service Instructions 1112C with straight dowels.
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Compliance Time
Effective October 17, 1972. Actions required within specified hours in service: inspections within 10 hours after effective date and every 25 hours thereafter; compliance with (d) or (f) within 25 or 50 hours as specified.
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Affected Aircraft
AVCO LyCOMING IGSO-540-A series engines except S/N 2537-50 and subsequent; IGSO-540-B series except S/N 2541-50 and subsequent; and specific serial numbers overhauled after 26 January 1970.
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Federal Register Abstract
Crankcase Bearings
Applicability Source Text
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AD Final Rules - DRS_72-21-06.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 72-21-06 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines Subject: Crankcase Bearings Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 10/17/1972 Make: Lycoming Engines Model: IGSO-540-A1A | IGSO-540-A1C | IGSO-540-A1D | IGSO-540-A1E | IGSO-540-A1F | IGSO-540-B1A | IGSO-540-B1C Product Type: Engine Product Subtype: Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: Updated RGL applicability to match AD applicability; CAR C-11-185 AIRWORTHINESS DIRECTIVES FINAL RULES: 72-21-06 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-1535 AD NUMBER: 72-21-06 SUBJECT HEADING: AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines ACTION: SUMMARY: DATES: Effective October 17, 1972. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 72-21-06 AVCO LYCOMING: Amendment 39-1535. Applies to IGSO-540-A series engines except S/N 2537-50 and subsequent; and IGSO-540-B series engines except S/N 2541-50 and subsequent; and IGSO-540-A and -B engines S/N 747-50, 844-50, 852-50, 947-50, 1184-50, 1240-50, 1361-50, 1402-50, 1453-50, 1544-50, 1767-50, 1773-50, 1794-50, 1799-50, 1933-50 overhauled (also known as remanufactured) by Lycoming after 26 January 1970. To prevent shifting and possible failures of the crankcase bearings perform the following: (a) Engines that have accumulated less than 500 hours in service since new or overhaul must have the lubrication system inspected for metal contaminants within the next 10 hours in service after the effective date of this AD and every 25 hours in service thereafter. Further, at the accumulation of 525 hours in service compliance with (d) or (f) is required. (b) Engines that have accumulated 500 hours or more in service since new or overhaul must have the lubrication system inspected for metal contaminants within the next 10 hours in service after the effective date of this AD, and every 25 hours in service thereafter. Further, compliance with (d) or (f) is required within 25 hours in service after the effective date of this AD. (c) Compliance with (d) or (f) is required if metal contaminants are detected during the above inspections. (d) Remove number four cylinder and examine visually the position of number three main bearing for shifting in accordance with Part II of Avco Lycoming Service Bulletin No. 327B. Should shifting be detected, comply with paragraph (f). (e) Unless already accomplished, compliance with paragraph (f) is required within 50 hours in service after the effective date of this AD on engines that have accumulated 1200 hours or more in service since new or last overhaul. (f) Repair the crankcase as described in Lycoming Service Instructions No. 1112C and install straight crankcase bearing dowels per Lycoming Service Bulletin No. 326 or equivalent repair and alteration approved by Chief, Engineering and Manufacturing Branch, FAA, Eastern Region. Compliance with the provisions of this paragraph eliminates the inspection requirements of this AD. This amendment is effective October 17, 1972. FOOTER:
Document Text
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AD Final Rules - DRS_72-21-06.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 72-21-06 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines Subject: Crankcase Bearings Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 10/17/1972 Make: Lycoming Engines Model: IGSO-540-A1A | IGSO-540-A1C | IGSO-540-A1D | IGSO-540-A1E | IGSO-540-A1F | IGSO-540-B1A | IGSO-540-B1C Product Type: Engine Product Subtype: Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: Updated RGL applicability to match AD applicability; CAR C-11-185 AIRWORTHINESS DIRECTIVES FINAL RULES: 72-21-06 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-1535 AD NUMBER: 72-21-06 SUBJECT HEADING: AVCO LYCOMING Model IGSO-540-A and IGSO-540-B Series Engines ACTION: SUMMARY: DATES: Effective October 17, 1972. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 72-21-06 AVCO LYCOMING: Amendment 39-1535. Applies to IGSO-540-A series engines except S/N 2537-50 and subsequent; and IGSO-540-B series engines except S/N 2541-50 and subsequent; and IGSO-540-A and -B engines S/N 747-50, 844-50, 852-50, 947-50, 1184-50, 1240-50, 1361-50, 1402-50, 1453-50, 1544-50, 1767-50, 1773-50, 1794-50, 1799-50, 1933-50 overhauled (also known as remanufactured) by Lycoming after 26 January 1970. To prevent shifting and possible failures of the crankcase bearings perform the following: (a) Engines that have accumulated less than 500 hours in service since new or overhaul must have the lubrication system inspected for metal contaminants within the next 10 hours in service after the effective date of this AD and every 25 hours in service thereafter. Further, at the accumulation of 525 hours in service compliance with (d) or (f) is required. (b) Engines that have accumulated 500 hours or more in service since new or overhaul must have the lubrication system inspected for metal contaminants within the next 10 hours in service after the effective date of this AD, and every 25 hours in service thereafter. Further, compliance with (d) or (f) is required within 25 hours in service after the effective date of this AD. (c) Compliance with (d) or (f) is required if metal contaminants are detected during the above inspections. (d) Remove number four cylinder and examine visually the position of number three main bearing for shifting in accordance with Part II of Avco Lycoming Service Bulletin No. 327B. Should shifting be detected, comply with paragraph (f). (e) Unless already accomplished, compliance with paragraph (f) is required within 50 hours in service after the effective date of this AD on engines that have accumulated 1200 hours or more in service since new or last overhaul. (f) Repair the crankcase as described in Lycoming Service Instructions No. 1112C and install straight crankcase bearing dowels per Lycoming Service Bulletin No. 326 or equivalent repair and alteration approved by Chief, Engineering and Manufacturing Branch, FAA, Eastern Region. Compliance with the provisions of this paragraph eliminates the inspection requirements of this AD. This amendment is effective October 17, 1972. FOOTER:
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Retrieved: Apr 8, 2026
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