AD 77-20-07
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Lycoming Engines | O-320-H1AD | AVCO LYCOMING Model O-320-H Series Engines |
| engine | Lycoming Engines | O-320-H1BD | AVCO LYCOMING Model O-320-H Series Engines |
| engine | Lycoming Engines | O-320-H2AD | AVCO LYCOMING Model O-320-H Series Engines |
| engine | Lycoming Engines | O-320-H2BD | AVCO LYCOMING Model O-320-H Series Engines |
| engine | Lycoming Engines | O-320-H3AD | AVCO LYCOMING Model O-320-H Series Engines |
| engine | Lycoming Engines | O-320-H3BD | AVCO LYCOMING Model O-320-H Series Engines |
Unsafe Condition
Loose rocker arm retaining studs and failure of the hydraulic tappets could cause hazards in flight.
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Required Actions
Remove rocker box covers, rocker arms, fulcrums, spacer washers, and push rods. Inspect fulcrum seating surfaces for wear steps exceeding 0.003 inches and replace affected parts. Remove shroud tube springs, shroud tubes, and hydraulic tappets. Inspect camshaft lobes for wear or metal loss and replace as needed. Replace P/N LW-15168 hydraulic tappets with P/N LW-16168 or LW-16585. Install new oversize rocker arm retaining studs for engines serial 101-76 through 2182-76 per Service Bulletin 412. Equivalent methods may be approved.
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Compliance Time
within the next 50 hours in service after the effective date of this AD unless previously accomplished
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Affected Aircraft
AVCO Lycoming Model O-320-H series engines, serial numbers L-101-76 through L-3829-76, L-3831-76, L-3843-76 through L-3859-76, L-3864-76, L-3866-76, L-3871-76, L-3902-76 through L-3907-76, and all engines overhauled by Lycoming before March 24, 1978.
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Federal Register Abstract
Loose Rocker Arm Retaining Studs and Hydraulic Tappets
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_77-20-07.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 77-20-07 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: AVCO LYCOMING Model O-320-H Series Engines Subject: Loose Rocker Arm Retaining Studs and Hydraulic Tappets Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 08/31/1978 Make: Lycoming Engines Model: O-320-H1AD | O-320-H1BD | O-320-H2AD | O-320-H2BD | O-320-H3AD | O-320-H3BD 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: AIRWORTHINESS DIRECTIVES FINAL RULES: 77-20-07 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-3284 AD NUMBER: 77-20-07 SUBJECT HEADING: AVCO LYCOMING Model O-320-H Series Engines ACTION: SUMMARY: DATES: Effective August 31, 1978. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 77-20-07 AVCO LYCOMING: Amendment 39-3051 as amended by Amendment 39-3284. Applies to O- 320-H series engines, Serial Number L-101-76 through L-3829-76, L-3831-76, L-3843-76 through L-3859-76, L-3864-76, L-3866-76, L-3871-76, L-3902-76 through L-3907-76 and all O-320-H series engines overhauled (Remanufactured by Lycoming) before March 24, 1978. Compliance required within the next 50 hours in service after the effective date of this AD unless previously accomplished. To prevent hazards in flight associated with loose rocker arm retaining studs and failure of the hydraulic tappets, accomplish the following: a. Remove all rocker box covers, rocker arm, fulcrums, spacer washers and push rods. b. Inspect the fulcrum seating surface in the rocker arm for wear steps in excess of .003 inches. Replace all parts found to have such indications. c. Remove the shroud tube springs, shroud tubes and hydraulic tappets from engine. d. Inspect the camshaft lobes for wear or loss of metal. Replace the camshaft found to have such indications. e. Replace P/N LW-15168 hydraulic tappets with P/N LW-16168 or P/N LW-16585 hydraulic tappets. (AVCO Lycoming Service Bulletin No. 424 refers to this subject.) f. On engine Serial Numbers 101-76 through 2182-76, remove all rocker arm retaining studs P/N 31- 16 from cylinder head and install new oversize rocker arm retaining studs in accordance with the instruction in Paragraph 3 of AVCO Lycoming Service Bulletin No. 412, dated July 8, 1977, or FAA approved equivalent. g. Equivalent methods of compliance may be approved by the Chief, Engineering & Manufacturing Branch, Federal Aviation Administration (FAA) Eastern Region. h. Upon submission of substantiating data by an owner or operator through an FAA Maintenance Inspector, The Chief, Engineering & Manufacturing Branch, Federal Aviation Administration (FAA) Eastern region may adjust the compliance time specified in this AD. Amendment 39-3051 was effective October 12, 1977. This amendment 39-3284 is effective August 31, 1978. FOOTER:
Document Text
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AD Final Rules - DRS_77-20-07.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 77-20-07 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: AVCO LYCOMING Model O-320-H Series Engines Subject: Loose Rocker Arm Retaining Studs and Hydraulic Tappets Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 08/31/1978 Make: Lycoming Engines Model: O-320-H1AD | O-320-H1BD | O-320-H2AD | O-320-H2BD | O-320-H3AD | O-320-H3BD 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: AIRWORTHINESS DIRECTIVES FINAL RULES: 77-20-07 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-3284 AD NUMBER: 77-20-07 SUBJECT HEADING: AVCO LYCOMING Model O-320-H Series Engines ACTION: SUMMARY: DATES: Effective August 31, 1978. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 77-20-07 AVCO LYCOMING: Amendment 39-3051 as amended by Amendment 39-3284. Applies to O- 320-H series engines, Serial Number L-101-76 through L-3829-76, L-3831-76, L-3843-76 through L-3859-76, L-3864-76, L-3866-76, L-3871-76, L-3902-76 through L-3907-76 and all O-320-H series engines overhauled (Remanufactured by Lycoming) before March 24, 1978. Compliance required within the next 50 hours in service after the effective date of this AD unless previously accomplished. To prevent hazards in flight associated with loose rocker arm retaining studs and failure of the hydraulic tappets, accomplish the following: a. Remove all rocker box covers, rocker arm, fulcrums, spacer washers and push rods. b. Inspect the fulcrum seating surface in the rocker arm for wear steps in excess of .003 inches. Replace all parts found to have such indications. c. Remove the shroud tube springs, shroud tubes and hydraulic tappets from engine. d. Inspect the camshaft lobes for wear or loss of metal. Replace the camshaft found to have such indications. e. Replace P/N LW-15168 hydraulic tappets with P/N LW-16168 or P/N LW-16585 hydraulic tappets. (AVCO Lycoming Service Bulletin No. 424 refers to this subject.) f. On engine Serial Numbers 101-76 through 2182-76, remove all rocker arm retaining studs P/N 31- 16 from cylinder head and install new oversize rocker arm retaining studs in accordance with the instruction in Paragraph 3 of AVCO Lycoming Service Bulletin No. 412, dated July 8, 1977, or FAA approved equivalent. g. Equivalent methods of compliance may be approved by the Chief, Engineering & Manufacturing Branch, Federal Aviation Administration (FAA) Eastern Region. h. Upon submission of substantiating data by an owner or operator through an FAA Maintenance Inspector, The Chief, Engineering & Manufacturing Branch, Federal Aviation Administration (FAA) Eastern region may adjust the compliance time specified in this AD. Amendment 39-3051 was effective October 12, 1977. This amendment 39-3284 is effective August 31, 1978. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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