Tips From Lycoming Technical Support

A list of the most frequently asked questions and issues from customers and a list of field practices that Lycoming Engines would like to see addressed, eliminated, or changed.

Field practices Lycoming Engines would like to see addressed, eliminated, or changed

Practice: During the course of regular oil and oil filter changes, the suction screen inspection is frequently overlooked.

Lycoming: Most likely it is overlooked because it can be located in different places and be a different shape based on the engine model. Inspecting it is vitally important because these screens capture large debris and prevent it from entering the oil pump. Debris in the suction screen is an indication that your engine has other problems that need further investigation.

Practice: An engine is running a high cylinder head temperature (CHT) and the normal suspects have been ruled out but not the engine baffling.

Lycoming: Service providers frequently undervalue the importance of “tight” baffling and its impact on proper engine cooling. We suggest an inspection of the sheet metal baffling with stapled seals that is attached by the airframe OEM to the engine that directs cooling air over the engine. If these baffles are missing, cracked, or have worn seals, the engine cooling is compromized. These baffles and associated seals conform to the cowling and must be intact and serviceable, or be replaced.

Practice: After an engine has experienced metal contamination, steps are frequently overlooked before returning an engine to service.

Lycoming: We occasionally see engines where service providers have overlooked checking propellers, governors, and oil coolers. We also suggest that you review the component or aircraft manufacturer’s requirements for continued airworthiness. Metal particles can migrate to these airframe components and contaminate the oil systems the next time the engine is operated. When metal contamination is known or suspected, those items must be checked and flushed as well. In particular AMTs need to send the oil cooler out to be flushed by a service provider authorized to certify that the cooler is clean and approved for return to service.

Practice: When refurbishing rocker arms, or rocker arm tips, the original geometry is not always maintained as it relates to the valve cap interface.

Lycoming: While the overhaul manual does allow the replacement of worn rocker arm bushings, no resurfacing of the rocker arm tip is permitted. Replacement of the rocker arm assembly is required whenever the tip exceeds the wear limits provided in the overhaul manual as this is an airworthiness issue. Unauthorized repairs may result in misalignment or side loading and can result in a broken valve stem.

Aircraft Maintenance Technology: Lycoming has been in business a long time and there are thousands of your engines in service. How important is it that AMTs and services providers have and are using the most current Lycoming Technical Publications?

Lycoming: It is required and necessary to have the recommended manuals to maintain standards and specifications and follow the latest service instructions and OEM best practices. It is extremely helpful to have the current technical publication(s) in front of you so when you call Lycoming Technical Support we are looking at the same information. This helps to troubleshoot and solve complicated problems quickly. Contact Lycoming ( or Aircraft Technical Publishers (ATP) for the most up-to-date overhaul manuals, operator’s manuals, illustrated parts catalogs, bulletin/letter/instruction, and special publications.

Aircraft Maintenance Technology: What information should AMTs and other maintenance service providers collect and have available before calling Lycoming Product Support?

Lycoming: First and most important is the engine serial number. All service data and maintenance history is tracked by the serial number.

Other important customer information:

  • Caller’s name, organization, telephone number, mail, and email address
  • Engine hours
  • TSO hours and who performed the last overhaul, Lycoming or another service provider?
  • Name of the aircraft owner and when the aircraft and engine were acquired. If the caller is not representing the original owner, then please provide the name of the previous owner.

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