77-20-07: Loose Rocker Arm Retaining Studs and Hydraulic Tappets
FAA order 77-20-07 is an airworthiness directive in force since August 31, 1978. The FAA's subject line: Loose Rocker Arm Retaining Studs and Hydraulic Tappets. It names the Lycoming O-320-H2AD, Lycoming O-320 series engines: about 27,394 aircraft on the U.S. register today across them, though an order usually covers particular versions or serial numbers rather than every one. System: engine.
What it applies to as the FAA lists it
- Kind of product
- Engine
- Makes
- Lycoming Engines
- Models
- O-320-H1AD, O-320-H1BD, O-320-H2AD, O-320-H2BD, O-320-H3AD, O-320-H3BD
- Engine series
- Lycoming O-320-H2AD 83 aircraft
Lycoming O-320 series 27,311 aircraft
Dates and paperwork
- In force since
- August 31, 1978
- Docket
- Unknown
- Status
- Current
- The FAA's document
- Read the order on the FAA's site
The order itself the regulatory text, as published
Show the full text (2,054 characters)
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 ofmetal. 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.
Source: FAA Dynamic Regulatory System, airworthiness directives. The FAA's document is the authority; the register counts are this site's, from the FAA register of October 30, 2026. Connections as data: /graph/directive/77-20-07.json · aircraft systems.